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A TRIBUTE TO SCULPTURAL ELEGANCE

The masterful play of lines and curves gives rise to a natural tension, which runs from the bow to the extreme stern, dressing the abundant interior volumes with a gritty and dynamic exterior design. The large full-height windows rise from the hull to the superstructure, further lightening the yacht’s appearance while expanding the sense of space inside.

ABSOLUTE AESTHETIC

The interiors transcend simple decoration, focusing on the composition of the space: free-flowing surfaces detach from the walls, becoming design elements in their own right; soft lines and organic geometries liquify the environments, welcoming and relaxing the ambience; the total project is charmed by a distinctive style and an independent mind.

THE TOP SPOT

Every form of lounging is comfortably accomodated on the yacht’s largest flush outdoor deck, and the superlative views put the cherry ontop of any rooftop revelry hosted here.

A SEA-IMMERSIVE EXPERIENCE

The full-height windows in the owner’s suite offer extraordinary views of the sea and an expanded perception of space. Every precious detail shines under the flood of natural light that follows.

OUR ADVANCED TOOLKIT

Azimut’s pioneering use of carbon fiber lamination goes beyond pure performance. The Carbon-Tech Generation offers expanded volumes on board, while maintaining excellent dynamic stability and perfect handling. Preserving the yacht’s low center of gravity, the carbon fiber was focused on the upper parts of the yacht, lightening the laminated components by up to 30% and reducing the natural roll momentum up to 15%.

Automatic interceptors by Humphree gives the vessel the lift it needs to get up on plane faster or to reach that optimum running trim. In this way the resistance of the hull is automatically optimised for every speed and load condition, this resulting in increased speed and lower fuel consumption. The Humphree system is all electric powered by 12-24 Volt DC. Thanks to the design of the Interceptor it only requires a small amount of power to move the blade up and down, even under high speed operation.

The stabilization system consists of Stabilis Electra™ stabilizing fins and Dualis Electra™ thrusters. Reliable, precise and silent, the stabilizing fins are even capable of reducing energy consumption. The thrusters’ quality casting and mechanics yield a high thrust-to-power ratio, higher than other systems.

The helm displays consolidate all the functions of the yacht with Simrad Command, from the visualization of engine data and related consumption, to the control of generators, trim and interceptor management, lights, batteries and air conditioning. There are also advanced navigation tools and system automations to make the pilot’s job easier.

This yacht’s design and engineering meet the highest standards for production recreational vessels. Azimut Yachts issues a declaration of the premium materials, advanced technology and rigorous testing procedures.

GRANDE 27M AT A GLANCE

• Length overall (incl. pulpit) 26,78 m (87' 10'')
• Beam max 6,59 m (21' 7'')
• Draft (incl. props at full load) 1,93 m (6' 4'')
• Displacement (at full load) 93 t (205028lb)
• Building material GRP + Carbon Fibre
• Exterior designer Stefano Righini
• Interior designer Achille Salvagni Architetti
• Hull designer P.L. AUSONIO Naval Architecture & Azimut R&D Dept.
• Builder Azimut Yachts
• Keel Planing, deadrise 13.6° at stern and 16.8° amidship
• Certifications CE A; NMMA
• Cabins 4/5 + 2 crew
• Berths 8/10 + 3 crew
• Head compartments 5 + 2 crew
• Engines 2 x MAN R V12 1900 hp
• Maximum speed (test load) up to 28 kn
• Cruising speed (performance test mass) up to 24 kn
• Fuel capacity 9500 l (2510 US Gal)
• Water capacity 2000 l (528 US Gal)

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Home » Blog » Buy a boat » 5 best small sailboats for sailing around the world

5 best small sailboats for sailing around the world

By Author Fiona McGlynn

Posted on Last updated: April 19, 2023

A small sailboat can take you big places

Small sailboats are the ticket to going cruising NOW — not when you retire, save up enough money, or find the “perfect” bluewater cruising boat. In fact, it’s the first principle in Lin and Larry Pardey’s cruising philosophy: “Go small, go simple, go now.”

Small yachts can be affordable, simple, and seaworthy . However, you won’t see many of them in today’s cruising grounds. In three years and 13,000 nautical miles of bluewater cruising, I could count the number of under 30-foot sailboats I’ve seen on one hand (all of them were skippered by people in their 20s and 30s).

Today’s anchorages are full of 40, 50, and 60-foot-plus ocean sailboats, but that’s not to say you can’t sail the world in a small sailboat. Just look at Alessandro di Benedetto who in 2010 broke the record for the smallest boat to sail around the world non-stop in his 21-foot Mini 6.5 .

So long as you don’t mind forgoing a few comforts, you can sail around the world on a small budget .

What makes a good blue water sailboat

While you might not think a small sailboat is up to the task of going long distances, some of the best bluewater sailboats are under 40 feet.

However, if you’re thinking about buying a boat for offshore cruising, there are a few things to know about what makes a small boat offshore capable .

Smaller equals slower

Don’t expect to be sailing at high speeds in a pocket cruiser. Smaller displacement monohulls are always going to be slower than larger displacement monohulls (see the video below to learn why smaller boats are slower). Therefore a smaller cruiser is going to take longer on a given passage, making them more vulnerable to changes in weather.

A few feet can make a big difference over a week-long passage. On the last leg of our Pacific Ocean crossing, our 35-foot sailboat narrowly avoid a storm that our buddy boat, a 28-foot sailboat, couldn’t. Our friend was only a knot slower but it meant he had to heave to for a miserable three days.

Small but sturdy

If a pocket cruiser encounters bad weather, they will be less able to outrun or avoid it. For this reason, many of the blue water sailboats in this list are heavily built and designed to take a beating.

Yacht design has changed dramatically over the last 50 years. Today, new boats are designed to be light and fast. The small sailboats in our list are 30-plus year-old designs and were built in a time when weather forecasts were less accurate and harder to come by.

Back in the day, boat were constructed with thicker fiberglass hulls than you see in modern builds. Rigs, keels, rudders, hulls and decks – everything about these small cruising sailboats was designed to stand up to strong winds and big waves. Some of the boats in this post have skeg-hung rudders and most of them are full keel boats.

The pros and cons of pocket cruiser sailboats

Pocket cruiser sailboats present certain advantages and disadvantages.

More affordable

Their smaller size makes them affordable bluewater sailboats. You can often find great deals on pocket cruisers and sometimes you can even get them for free.

You’ll also save money on retrofits and repairs because small cruising sailboats need smaller boat parts (which cost a lot less) . For example, you can get away with smaller sails, ground tackle, winches, and lighter lines than on a bigger boat.

Moorage, haul-outs, and marine services are often billed by foot of boat length . A small sailboat makes traveling the world , far more affordable!

When something major breaks (like an engine) it will be less costly to repair or replace than it would be on a bigger boat.

Less time consuming

Smaller boats tend to have simpler systems which means you’ll spend less time fixing and paying to maintain those systems. For example, most small yachts don’t have showers, watermakers , hot water, and electric anchor windlasses.

On the flip side, you’ll spend more time collecting water (the low-tech way) . On a small sailboat, this means bucket baths, catching fresh water in your sails, and hand-bombing your anchor. Though less convenient, this simplicity can save you years of preparation and saving to go sailing.

Oh, and did I mention that you’ll become a complete water meiser? Conserving water aboard becomes pretty important when you have to blue-jug every drop of it from town back to your boat.

Easier to sail

Lastly, smaller boats can be physically easier to sail , just think of the difference between raising a sail on a 25-foot boat versus a 50-foot boat! You can more easily single-hand or short-hand a small sailboat. For that reason, some of the best solo blue water sailboats are quite petite.

As mentioned above small boats are slow boats and will arrive in port, sometimes days (and even weeks) behind their faster counterparts on long offshore crossings.

Consider this scenario: two boats crossed the Atlantic on a 4,000 nautical mile route. The small boat averaged four miles an hour, while the big boat averaged seven miles an hour. If both started at the same time, the small boat will have completed the crossing two weeks after the larger sailboat!

Less spacious

Living on a boat can be challenging — living on a small sailboat, even more so! Small cruising boats don’t provide much in the way of living space and creature comforts.

Not only will you have to downsize when you move onto a boat  you’ll also have to get pretty creative when it comes to boat storage.

It also makes it more difficult to accommodate crew for long periods which means there are fewer people to share work and night shifts.

If you plan on sailing with your dog , it might put a small boat right out of the question (depending on the size of your four-legged crew member).

Less comfortable

It’s not just the living situation that is less comfortable, the sailing can be pretty uncomfortable too! Pocket cruisers tend to be a far less comfortable ride than larger boats as they are more easily tossed about in big ocean swell.

Here are our 5 favorite small blue water sailboats for sailing around the world

When we sailed across the Pacific these were some of the best small sailboats that we saw. Their owners loved them and we hope you will too!

The boats in this list are under 30 feet. If you’re looking for something slightly larger, you might want to check out our post on the best bluewater sailboats under 40 feet .

Note: Price ranges are based on SailboatListings.com and YachtWorld.com listings for Aug. 2018

Albin Vega 27($7-22K USD)

The Albin Vega has earned a reputation as a bluewater cruiser through adventurous sailors like Matt Rutherford, who in 2012 completed a 309-day solo nonstop circumnavigation of the Americas via Cape Horn and the Northwest Passage (see his story in the documentary Red Dot on the Ocean ). 

• Hull Type: Long fin keel
• Hull Material: GRP (fibreglass)
• Length Overall:27′ 1″ / 8.25m
• Waterline Length:23′ 0″ / 7.01m
• Beam:8′ 1″ / 2.46m
• Draft:3′ 8″ / 1.12m
• Rig Type: Masthead sloop rig
• Displacement:5,070lb / 2,300kg
• Designer:Per Brohall
• Builder:Albin Marine AB (Swed.)
• Year First Built:1965
• Year Last Built:1979
• Number Built:3,450

Cape Dory 28 ($10-32K USD) 

This small cruising sailboat is cute and classic as she is rugged and roomy. With at least one known circumnavigation and plenty of shorter bluewater voyages, the Cape Dory 28 has proven herself offshore capable.

• Hull Type: Full Keel
• Length Overall:28′ 09″ / 8.56m
• Waterline Length:22′ 50″ / 6.86m
• Beam:8’ 11” / 2.72m
• Draft:4’ 3” / 1.32m
• Rig Type:Masthead Sloop
• Displacement:9,300lb / 4,218kg
• Sail Area/Displacement Ratio:52
• Displacement/Length Ratio:49
• Designer: Carl Alberg
• Builder: Cape Dory Yachts (USA)
• Year First Built:1974
• Year Last Built:1988
• Number Built: 388

Dufour 29 ($7-23K)

As small bluewater sailboats go, the Dufour 29 is a lot of boat for your buck. We know of at least one that sailed across the Pacific last year. Designed as a cruiser racer she’s both fun to sail and adventure-ready. Like many Dufour sailboats from this era, she comes equipped with fiberglass molded wine bottle holders. Leave it to the French to think of everything!

• Hull Type: Fin with skeg-hung rudder
• Length Overall:29′ 4″ / 8.94m
• Waterline Length:25′ 1″ / 7.64m
• Beam:9′ 8″ / 2.95m
• Draft:5′ 3″ / 1.60m
• Displacement:7,250lb / 3,289kg
• Designer:Michael Dufour
• Builder:Dufour (France)
• Year First Built:1975
• Year Last Built:1984

Vancouver 28 ($15-34K)

A sensible small boat with a “go-anywhere” attitude, this pocket cruiser was designed with ocean sailors in mind. One of the best cruising sailboats under 40 feet, the Vancouver 28 is great sailing in a small package.

• Hull Type:Full keel with transom hung rudder
• Length Overall: 28′ 0″ / 8.53m
• Waterline Length:22’ 11” / 6.99m
• Beam:8’ 8” / 2.64m
• Draft:4’ 4” / 1.32m
• Rig Type: Cutter rig
• Displacement:8,960lb / 4,064 kg
• Designer: Robert B Harris
• Builder: Pheon Yachts Ltd. /Northshore Yachts Ltd.
• Year First Built:1986
• Last Year Built: 2007
• Number Built: 67

Westsail 28 ($30-35K)

Described in the 1975 marketing as “a hearty little cruiser”, the Westsail 28 was designed for those who were ready to embrace the cruising life. Perfect for a solo sailor or a cozy cruising couple!

• Hull Type: Full keel with transom hung rudder
• Hull Material:GRP (fibreglass)
• Length Overall:28′ 3” / 8.61m
• Waterline Length:23’ 6” / 7.16m
• Beam:9’ 7” / 2.92m
• Displacement:13,500lb / 6,124kg
• Designer: Herb David
• Builder: Westsail Corp. (USA)
• Number Built:78

Feeling inspired? Check out the “go small” philosophy of this 21-year-old who set sail in a CS 27.

Fiona McGlynn is an award-winning boating writer who created Waterborne as a place to learn about living aboard and traveling the world by sailboat. She has written for boating magazines including BoatUS, SAIL, Cruising World, and Good Old Boat. She’s also a contributing editor at Good Old Boat and BoatUS Magazine. In 2017, Fiona and her husband completed a 3-year, 13,000-mile voyage from Vancouver to Mexico to Australia on their 35-foot sailboat.

Saturday 1st of September 2018

Very useful list, but incomplete - as it would necessarily be, considering the number of seaworthy smaller boats that are around.

In particular, you missed/omitted the Westerly "Centaur" and its follow-on model, the "Griffon". 26 feet LOA, bilge-keelers, weighing something over 6000 pounds, usually fitted with a diesel inboard.

OK, these are British designs, and not that common in the US, but still they do exist, they're built like tanks, and it's rumored that at least one Centaur has circumnavigated.

Friday 31st of August 2018

This is a helpful list, thank you. I don't think most people would consider a 28' boat a pocket cruiser, though!

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Review of Saphire 27

Basic specs..

The boat is equipped with 42.0 liter fresh water capacity.

The boat equipped with a fractional rig. A fractional rig has smaller headsails which make tacking easier, which is an advantage for cruisers and racers, of course. The downside is that having the wind from behind often requires a genaker or a spinnaker for optimal speed.

DaggerBoard

The Saphire 27 is equipped with a daggerboard keel. A daggerboard is a lifting keel that can be lowered and raised, allowing the boat to enter shallow waters as well.

The boat can enter even shallow marinas as the draft is just about 0.45 - 0.55 meter (1.48 - 1.78 ft) dependent on the load. See immersion rate below.

Sailing characteristics

This section covers widely used rules of thumb to describe the sailing characteristics. Please note that even though the calculations are correct, the interpretation of the results might not be valid for extreme boats.

What is Capsize Screening Formula (CSF)?

The capsize screening value for Saphire 27 is 2.31, indicating that this boat would not be accepted to participate in ocean races.

What is Theoretical Maximum Hull Speed?

The theoretical maximal speed of a displacement boat of this length is 6.6 knots. The term "Theoretical Maximum Hull Speed" is widely used even though a boat can sail faster. The term shall be interpreted as above the theoretical speed a great additional power is necessary for a small gain in speed.

The immersion rate is defined as the weight required to sink the boat a certain level. The immersion rate for Saphire 27 is about 125 kg/cm, alternatively 703 lbs/inch. Meaning: if you load 125 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 703 lbs cargo on the boat it will sink 1 inch.

Sailing statistics

This section is statistical comparison with similar boats of the same category. The basis of the following statistical computations is our unique database with more than 26,000 different boat types and 350,000 data points.

What is Motion Comfort Ratio (MCR)?

What is L/B (Length Beam Ratio)?

What is a Ballast Ratio?

What is Displacement Length Ratio?

What is SA/D (Sail Area Displacement ratio)?

Maintenance

When buying anti-fouling bottom paint, it's nice to know how much to buy. The surface of the wet bottom is about 24m 2 (258 ft 2 ). Based on this, your favourite maritime shop can tell you the quantity you need.

Are your sails worn out? You might find your next sail here: Sails for Sale

If you need to renew parts of your running rig and is not quite sure of the dimensions, you may find the estimates computed below useful.

This section is reserved boat owner's modifications, improvements, etc. Here you might find (or contribute with) inspiration for your boat.

Do you have changes/improvements you would like to share? Upload a photo and describe what you have done.

We are always looking for new photos. If you can contribute with photos for Saphire 27 it would be a great help.

If you have any comments to the review, improvement suggestions, or the like, feel free to contact us . Criticism helps us to improve.

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New Azimut Grande 27 Metri motor yacht sold

A 2020-built 26.78 metre Azimut Grande 27 Metri motor yacht, listed for sale by Azimut of America, has been sold with the buyer introduced by Henry Schonthal of Reel Deal Yachts.

Following in the footsteps of the yard’s flagship Azimut Grande 35M , the 27 Metri also features the same design combination of Achille Salvagni for the interiors and Stefano Righini for the exteriors.

Extensive use of carbon fibre in the superstructure has allowed the designers much more scope to expand the upper deck areas without compromising on the stability of the Azimut Grande 27 Metri.

Accommodation is for 10 guests split across five cabins, including a full-beam main-deck owner’s cabin that benefits from extra space thanks to the vertical section of the bow as well as a fold-out superyacht balcony . Meanwhile the compact crew quarters allow for a staff of two people.

The impact of this light and airy design is best seen in the main-deck saloon with its freestanding furniture and floor-to-ceiling windows on both sides. On-deck relaxation options are plentiful, with a large foredeck seating area and a raised observation deck back aft.

The asking price of the Azimut Grande 27 Metri has been withheld.

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Crossover 27

There are moments in life when the body and mind demand balance and the desire for a machine that encompasses the best of two worlds. Lynx Yachts’ Crossover Series embodies this thinking and offers a range of vessels that provide the versatility of the YXT Series with the elegance and style of the Adventure Series. The Crossover is neither one nor the other but something in between and firmly ahead of the game.

Specifications at a glance

LENGTH OVERALL 

FUEL (MAX) 

The Exterior

This 27.4-metre is the first model in the Crossover Series, offering a stylish solution to a challenge faced by the market. It embraces the qualities of a graceful superyacht and the versatility of a support vessel into one fully customisable expedition yacht that delivers more than meets the eye. Stylish and robust, the Crossover 27 answers the call of owners in search of a vessel that can keep pace with their sporty lives.

Offering 360-degree views out to sea and a generous seating area behind the helm, the bridge is a peaceful command centre. Enjoy your favourite movie or review the day’s events in complete comfort while keeping an eye on your surrounds or the direction of your voyage. Should you desire a different layout, LYNX YACHTS is more than happy to realise your wishes.

70 SQUARE METRE MAIN-DECK​

The main deck is one of the core features of this model with an area of 70-square-metres to be enjoyed. Like the YXT Series, this space can stow multiple tenders and toys but once clear, this area makes the most of the 7.1-metre beam to create an impressive open space for entertainment. Leading off from the main deck is a spacious saloon with large windows

Technical Specifications

DISPLACEMENT

GROSS TONNAGE

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How to Calculate Outboard Motor Size for Sailboats

It seems so complex to pick the right engine size for your sailboat. I was done with complex calculations and tried to make it easier here.

How to pick the right outboard motor size for your sailboat? To get the right amount of horsepower needed to efficiently propel a sailboat, divide the displacement of the boat (in lb) by 550. You need approximately 1 HP per 550 lb of displacement or 4 HP per 2200 lb. Most sailboats don't need a motor with more than 30 HP.

In this article, I'm talking about small outboard engines for sailboats. We're talking about displacement hulls here, so in other words: keel boats. They need more power than flat bottoms.

But they're not powerboats - so it's not our mission to go fast. It's our mission to get decent speed, good control over the boat, and the best possible fuel efficiency. Without breaking the bank of course.

On this page:

How to pick the right motor size, other factors that are important for size, why is the right motor size important, is there a max hp for sailboats, in conclusion, related questions.

Sailboats need way smaller engines than powerboats. That's great news (unless your ultimate goal is speed), because it's cheaper to buy, cheaper to drive, and cheaper to maintain.

The amount of power you need is related to the hull displacement of your boat.

I like to use the simple formula:

HP = displacement (lb) / 550

So 1 HP for every 550 lb displacement, and 4 hp per 2200 lb.

Here, HP is the amount of horsepower you need to reach the maximum hull speed. This is in optimal conditions. So you have smooth water, no windage, a clean and polished hull, and so on.

If you want to get it absolutely right, you also need to correct for propellor size. And of course, a lot of other factors come into play (more on that later). But generally, these engine sizes will work with the following weights:

That sounds about right to me. But remember that these are all rough estimates: I just try to give you a ballpark figure. There is no one formula to get an exact number. The hull design, sailing conditions, and your personal preference are all very important.

If you're serious about getting a new engine, I definitely recommend to get advice from an expert . But you know, salespeople always recommend the Turbo version. Remember that you don't have to overpower a sailboat. Usually you don't need anything over 30 HP. So at least you now know what will work on average.

What is hull displacement?

• Hull displacement is the weight of the boat, or the amount of water the boat displaces.
• Maximum hull displacement is the weight of the boat when it's fully loaded, including crew.

The weight of the boat is the same as its displacement, because the weight of any object is exactly equal to the weight of the water it displaces (aka: pushes aside). This is called Archimedes Principle.

The weight slightly differs in saltwater from freshwater, because saltwater is heavier. In saltwater, the boat gets a bit lighter. So in theory you can use a smaller engine for a bluewater boat, but in practice this is offset by the stronger current and wind.

How to find the displacement of your boat?

Most manufacturers simply give you the displacement of your boat. If you can't find any data, because, for example, you own an old boat, you can weigh your boat on a truck scale. You can also haul it out and measure it (which is painstaking work).**

Tip: if you're gonna weigh your boat, simply drive it onto a truck scale, and retract the weight of the trailer from the total weight.

Of course, it's not so simple. This formula gives a rough estimate. But for me this was way clearer than all that black magic that I get when I ask people what size engine I should get.

Let's look at the things this formula doesn't take into account.

2-strokes are more powerful than 4-strokes. Two-stroke engines fire once every revolution and four-strokes fire once every other revolution. This makes the 2-stroke twice as powerful. They provide more torque at a higher RPM. But they also wear more quickly. The 4-stroke will last you a lot longer, and its also more fuel efficient.

The right propellor size is just as important as having enough horsepower. With a smaller prop diameter, it has to work harder to generate the same propulsion as a larger diameter. But you can't just go larger always. The prop affects the RPM of your engine, and you have to get in the right range (more on this later). You also have to check the maximum diameter that fits your boat.

Diesels have more torque, because the compression rate is higher than that of gasoline engines. So if you consider a diesel, you can do with less HPs.

High windage hulls (multihulls) need a bit more. A multihull (or larger hull in general) suffers from more friction because of the larger surface. So the engine needs to work a little harder.

If you sail longer distances under power , or against the wind it's a good idea to get a larger engine (but not too large). This helps you to save on fuel since you have lower RPM. Especially if you sail offshore or on open sea. The engine needs to work harder due to stronger wind and current.

If you're just sailing in and out of the marina under power, you may need less HP.

Smooth hull designs need less HPs than bulky hull designs, like the classic wooden clippers and crabbers for example.

It matters to get the right size outboard motor for a couple of reasons.

First of all: smaller engines are cheaper, so you save money on buying the engine.

Secondly: smaller engines use a lot less fuel, so you save money on using the engine.

Thirdly: smaller engines are cheaper to maintain: so you save money on maintenance.

So why not get the smallest engine and get the best fuel economy? There are a couple of advantages to getting a (slightly) bigger engine:

• More power means more control (easier to stop the boat, in case you need to)
• Finding the sweet spot might actually reduce fuel consumption

The sweet spot

To perform optimally, an engine should get up to speed. The problem with an overpowered boat is that the engine won't rev up to 80 - 90% of the RPM. This kills fuel efficiency and also the cooling system won't operate optimally.

• The optimal cruising RPM of the engine is about 85-95% of the maximal RPM
• You should reach cruising RPM at hull speed, so your engine should be at about 90% RPM

The propeller size is very important for the RPM. If your prop diameter is too wide, the engine can't get up to speed and struggles to build power. Bad for fuel economy, bad for the engine, and bad for performance.

On the other hand, if your prop is too small, you don't make use of the engine's full power.

If you struggle to get to high RPM, your prop is too large. If your engine is constantly in the red, you're underpropped.

So don't go too big on the prop, but also don't go too small. The easiest way to get it right is to check the engines manual and see what the manufacturer recommends.

You can definitely go too big on a sailboats engine. An overpowered yacht doesn't make any sense. True, it can look cool, but it can't feel cool. Every displacement hull has a maximum hull speed. That means that it cannot go any faster than the max speed. So if your engine can cruise at that speed, it's not getting any better.

The problem with displacement hulls is that they displace the water, or in other words: they push the water in front of them. They cannot move any faster than they can push away the water. And because the resistance increases as speed increases, there's an absolute, physical speed limit for each keelboat.

That's why powerboats have to get out of the water to reach top speed.

Fun fact: the longer your boat, the higher the hull speed. Want to know the maximum hull speed for your boat? You can find it in this article .

So, you can't go faster than your maximum hull speed, so a 50+HP engine is kind of ridiculous. Bear in mind that a large engine also has the following disadvantages:

First of all: larger engines are more expensive, so you spend more money when buying the engine.

Secondly: larger engines use a lot more fuel, so you spend more money when using the engine.

Thirdly: larger engines are more expensive to maintain: so you spend more money on maintenance.

Also, if your engine is too big, it doesn't reach the optimal cruising RPM, so your fuel economy also gets really bad FAST.

I suggest getting the smallest possible engine that gets you to maximum hull speed while it's at roughly 90% of the RPM. As long as it gives you enough control and good handling, it will get you there. If you give up on going fast, you can actually get really good fuel economy and your engine will last you probably 20 years.

If you want to go fast, a sailboat is not the right one for you. You should instead get a powerboat.

I'm just kidding. Read my 13 Reasons Why Sailing is Better Than Powerboating here .

Do sailboats have motors? Most sailboats are power assisted boats, which means they have a small auxiliary engine to cruise in light air. When a sailboat is sailing under engine power, it is considered a motorboat and it doesn't have right of way.

Thanks for answering my questions.

Taylor Bishop

Thanks for explaining how you can figure out what size you need for an outboard motor. You mentioned that you should find the displacement by weigh a boat on a truck scale. I’m interesting to learn if you need to regularly weigh it in case the hull displacement could change or if it will always be consistent.

Shawn Buckles

Hi MitI, you’re welcome, my pleasure.

Hi Taylor, my pleasure.

You don’t need to weigh your boat regularly, as the hull displacement will stay consistent. You could literally see the hull displacement as the amount of space your hull takes up in the water. So as long as you don’t make any major changes to the hull shape or ballast of your boat, you should see no differences in displacement.

Roger S Johnson

How do you measure for shaft size, most outboard motors are for flat bottom and say measure to the bottom of the boat, most sailboats tapper to the aft. Where do you measure for a tapered bottom sail boat?

Will a 5 horse Honda 4 stroke be ok for a 25 foot Pearson Commander sail boat. Thanks for your time Luke

I think it would be Luke.

Great post, thanks for the info. A naive question from a soon-to-be sailor: I’m considering buying a 28 ft sailboat, with 2500 kg (ca. 5500 lbs) displacement. The engine is in pretty good condition, but is old and the original one (from 1977!), so I am also thinking of an alternative scenario in which it fails. I know that in my area replacing an inboard engine will cost double the price I’m putting down for the boat, and since I’m on a budget, that simply won’t be an option and outboards seem to be cheaper. So the question is: is it possible to put an outboard engine on all boats? Is there some factor that would make it impossible to mount an outboard engine on the boat? Thanks!

Garth Powelson

What is minimum length that a sailboat can go without an outboard. Does a 29’ “require by law” to have engine?

Hello Mr. Buckles, Thanks for the informative article. I’m looking to get the smallest possible outboard for my 1.5 ton displacement fiberglass monohull Hood 23’ sloop. Can I get away with a 4HP?!? What size prop would I need?!? (I’m only going to use it when there is NO wind, and, if I can stay 4HP or below, I am not required to register my vessel—which is pretty cool, so here’s hoping!)

Thanks again, Ship

Hi, I’ve got a older Pearson 39’ . I’m looking to remove the old 40 ho westerbeke and go electric. Unsure of what hp is going to be needed?

emilio h javier

i am purchasing a catalina 22 ft. i have in mind a 4 HP motor. what would be the length of the shaft.

I am considering buying a 25 ft sailboat with a 7200 lb displacement. The boats top speed is listed at 7knots per hour but the diesel motor does not work. The owner has a 9.9hp outboard that can be purchased with the boat. Is 9.9hp enough to power the boat to at least 5 to 6 knots per hour? Thanks. Rick

What weight outboard would be too much for a 20’ Santana, displacement 1,350 lbs? I don’t want too much weight at the back. I want the boat to be seaworthy.

I have not seen this amount of BS in years :) I’m not a marine engineer, yet physicist & avation engineer. You even can’t tell the difference between mass of the vessel and diplacement :D Fcking genius.

Leave a comment

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Moisture Meters: Can You Trust Them? We Test Five Models

If you are buying a used boat or are faced with repairs to a blistered hull, watch out a survey shows that many surveyors dont fully understand moisture meter operation, and our tests reveal severe limitations. we tell you what they can and cannot do..

Youve made an offer on a used boat and have retained a marine surveyor to examine the vessel prior to completing the transaction. One of the more important things he or she will do is make some sort of assessment about the condition of the hull. Delamination of the skins from the core or osmotic blisters are serious problems and may cause you to nix the deal.

Over time, all fiberglass hulls absorb moisture. Small amounts are not of great concern. Even higher amounts may not be an indication that the hull has or ever will blister, of which there are various causes.

Still, the prudent buyer and surveyor will want some indication of a hulls level of wetness. To determine this, the most common tool is the moisture meter. These small, handheld devices, generally costing less than $500, were originally developed for other industries, such as timber, roofing and building trades. They were adopted by the marine industry, but in many cases the makers of these instruments have made no real effort to modify them for use on fiberglass. Hence, the readings one might get from a fiberglass hull must be extrapolated from a scale designed for wood or concrete. This is your first clue that the moisture meter is an imperfect device for determining moisture levels in a fiberglass boats hull.

At Practical Sailor, we receive quite a few calls from readers who have questions about how best to diagnose and repair a blistered hull. Often, they tell us that the yard or surveyor used a moisture meter and found unacceptably high levels of moisture. Occasionally, the owner is advised to have the gelcoat peeled, perhaps even some of the laminate, then replaced. Our advice to them is to first, before committing to such an expensive repair job, try determining why the hull has blistered. If you don’t know the cause, you can’t prescribe the cure. Simply popping blisters and filling them with epoxy putty wont stabilize a hull laminate that still has uncatalyzed hardener in it. And in some instances, blisters are not indicative of deteriorating laminates. For example, solvents trapped during the application of bottom paint can cause blisters that may look like trouble, but are in fact harmless.

Before undertaking any major repairs, retain an independent surveyor, rather than rely on your boat yards recommendation. After all, its the yard which stands to make a profit on your repairs.

Many laminate experts advocate cutting a hull plug with a hole saw and having it analyzed in a laboratory. The procedure is destructive, to be sure, but the $300 or so cost of this test could save you thousands if it is found that the laminate is basically sound in spite of high moisture meter readings.

But not all experts agree, noting that the common lab tests to determine percentage of moisture and detection of gases still fail to pinpoint the exact cause of blistering, or predict the likelihood of blistering.

How Much Do Surveyors Know? Last year, we collaborated with marine surveyor, Jonathan Klopman of Marblehead, Massachusetts, in the testing of five leading brands of moisture meters-Sovereign, Tramex Skipper, Caisson Novanex, Protimeter Aquant and Protimeter Surveymaster SM. Prior to these tests, Klopman, sponsored by Professional Boatbuilder magazine, also distributed a questionnaire to 94 fellow surveyors. The results are eye-opening.

Ninety percent said they owned either the Sovereign or Tramex. Forty percent have been using the instrument for one to five years. The majority use it weekly. But when asked if they understood the operating principle, 33% answered incorrectly and 22% said they didnt know!

Fortunately, most seem to understand their meters limitations. While 60% said they trusted the readings most of the time, this same number also admitted that their meter could not provide an accurate prediction of an osmotic problem when there are no blisters evident on the hull .

Regarding how deep into the laminate the meter can read, 63% said they werent sure. After testing them, we now know why they werent sure: Depth varies by brand, scale settings used, and the meters may be fooled by additives in bottom coatings or the laminate itself.

Nevertheless, surveyors use moisture meters more than anybody else and throughtraining programs conducted by organizations such as NAMS (National Association of Marine Surveyors) and SAMS (Society of Accredited Marine Surveyors), their level of knowledge is increasing.

How They Work Most moisture meters are of the capacitance type. These meters have two electrodes or sensors, one that transmits an AC signal and another that receives it. Because water has a much higher dielectric constant or permitivity than air or fiberglass, the difference in strength between the transmitted and received signal can be measured and displayed on the meter, either by an analog needle or digitally in an LCD window.

Some meters, like the Sovereign, also have two pin probes for measuring moisture in wood; these work by resistance and use a DC signal.

A third method, used by the Protimeter Aquant and called the free-field effect, is slightly different. Instead of two electrodes next to each other, the Aquant has a transmitter in the head of the instrument, which directs a signal into the laminate where it is redirected by any moisture present back to the second electrode in the handle. In effect, the water acts as an aerial to re-radiate the RF signal.

The Tests A number of fiberglass panels were laid-up for testing with the meters. These consisted of alternating layers of mat and woven roving with general purpose polyester resin, ranging in thickness from .135″ to .672″ (to achieve the 1″ thickness shown in the graph above, we combined several panels). Additional panels were made up of Coremat.

We also made up some epoxy panels with graphite, aluminum and copper powder, barrier coat additives and carbon fiber.

Additional tests were performed to see if frozen water gives different readings, and to see if different types of bottom paint affect readings.

Lastly, we tested to see if battery voltage makes a difference in the readings. All of the units use 9-volt batteries, except the Protimeter Surveymaster, which uses two AA batteries.

All of the above tests were performed indoors on a bench. For the thickness tests, the panels were placed on top of two pads of wet carpet, soaking in a shallow tray. Reference readings were taken of each panel before setting them on the wet carpet. A second set of tests used paper wetted alternately with fresh and saltwater. In the accompanying graphs, these reference numbers are subtracted from the wet readings to show the actual moisture reading. We started with the thinnest panels, progressing to thicker panels in fine increments so that we could detect when the meter stopped penetrating the laminate all the way to the water.

After two series of bench tests, the first conducted by one of our contributing editors, a nuclear physicist, and a second series conducted by Klopman and PS staff, we took them to several boat yards and tried all five meters on a variety of hulls, some known to be wet, some blistered, and some dry.

Though all of the meters have graduated scales, some indicating percentage of moisture, these are not true representations of the amount of moisture in a fiberglass panel (in part, because most of these meters are not designed for fiberglass). Consequently, we recorded our readings as a percentage of full scale.

Further to the matter of moisture percentage, a fully saturated fiberglass hull will have no more than 2.5% to 3.5% moisture. Most of the meters designed for timber sound an alarm at 20-25% moisture, which is a typical fiber saturation point for many species. Some meter makers provide a conversion card for timber to fiberglass (eg., 25% wood = 3% glass), but few surveyors put a lot of stock in it. Hence there is no correlation between the percentage of moisture indicated by the meter and the actual amount of moisture in the laminate.

What We Found While there were some anomalies that are difficult to explain, and some variation in the responses, due perhaps to differing conditions (e.g., how the meter head is oriented to a surface can have a significant effect on the readings), we did arrive at some basic conclusions.

Battery Test. All of the meters automatically compensated for low battery voltage except the Sovereign, which must be continually set to zero to account for changes in battery voltage. This is done easily with a knob and the needle, but it is not necessary with the others. Also, the Protimeter Aquant will not turn on below 8-volts, which one presumes is near its minimum operating voltage.

Thickness Test: As expected, the thicker the laminate, the more difficulty the meters had in detecting water, even though the same amount of water was present underneath each panel. If a meter had more than one scale for sensitivity, we tried all of them.

With all meters, the readings would be quite low with a thick laminate, which could lead an inexperienced user to conclude that there isn’t much moisture present. This is especially confusing where the meters scale incorporates colored zones-green (good or low), yellow (fair or moderate) and red (bad or high), or colored lights, as in the case of the Protimeter Aquant and Surveymaster. What this means is that a moisture meter cannot tell you where the water is in the laminate or precisely how much. A lot of moisture deep in the laminate may give the same reading as a small amount of moisture near the surface. Knowing the thickness of a hull laminate ahead of testing is helpful, but in many boats wont be known. Plus, thickness varies throughout the laminate, from topsides to bottom, and even within the same general area.

The order in which the five meters ranked, from deepest to shallowest, was: Tramex, Protimeter Aquant, Protimeter Surveymaster SM, Caisson Novanex V1-D3 and Sovereign. (See table on page 5.)

Frozen water. We ran two different tests to determine whether the meters could detect frozen water. In the first, we compared a sample of .135″ laminate and wet paper frozen. No meter gave a reading differing from laminate alone. This suggested that the meters do not detect frozen water.

In the second set of tests, we took four panels in various stages of wetness and deterioration: moist, saturated, advanced brown rot and white rot. Reading were taken wet. Then the panels were frozen and tested again. Comparing the wet and frozen readings, most of the frozen readings were lower than the wet, but not all. We cannot account for those few frozen readings that were the same as room temperature readings or higher.

While the tests werent the same, the discrepancies leave questions. Still, the bottom line is not to trust any moisture meter readings taken when the laminate is below 32F. Wait until the temperature warms and the laminate has thawed.

As a side note, glycol, a byproduct of the resins used in boats and the cause of some blistering, will not freeze and can be detected in sub-freezing weather.

Polar compounds. A thin laminate with raw catalyst trapped in the layers was measured. This showed no significant difference to the normal panels with fully reacted catalyst.

Isopropyl alcohol, epoxy and hardener were placed in small, separate divots in a panel and covered with a poly sheet. This is a very crude and non-quantitative test that only checks for gross sensitivity. The Tramex and Protimeter Aquant showed no sensitivity to the compounds. The Sovereign and Caisson did. The Protimeter Surveymaster SM was not in hand during this test and so was not tested.

Metal detection. When we placed a sheet of aluminum foil under a panel, all of the meters gave readings similar to wet paper.

Next, we mixed copper, aluminum and aluminum-based WEST System 422 barrier coat additive into epoxy resin and brushed it on a bare Masonite panel. We tested the panels both dry and with wet paper behind them. The meters did not react significantly differently to any of these additives. Dry, the panels with additives read about the same as the bare Masonite panel. The same was true with wet paper behind.

When we performed the same test with carbon fiber, however, every meter was pegged or nearly so. This means that any hull with carbon fiber cannot be tested for wetness with a moisture meter.

Lastly, we performed the same test on graphite powder, because it is sometimes used as a pigment in black bottom paint. Here we noted an increase in the readings of some meters. For example, the Tramex read about 5% (relative scale of 1-100%) on the bare panel and about 55% with graphite. The Caisson read 7% on the bare and about 17% with graphite. The Protimeter Aquant, because its signal appears to begin reading just beneath the surface (an advantage in avoiding false positives owing to surface moisture) did not react significantly to the graphite-epoxy coating. The bottom line is that any unusual reading taken on black bottom paint should be investigated for the presence of graphite. Safer is the common recommendation to scrape away bottom paint and place the meter head directly on clean gelcoat. Be wary, however, of paint remaining in the gelcoat pores.

Owners should also know that these meters will often detect the steel webbing inside a rudder, sometimes even the copper foil used as a counterpoise for SSB radios, and condensation on the inside of the hull. But the meter doesn’t know the difference between metal and moisture, whether its inside the laminate or harmless condensation. Its alarm just beeps.

Individual Meters In addition to bench and field tests, we also evaluated each meter for quality of construction, handling, visibility and overall ease of use. Following are our comments, plus a brief description of each meter.

Sovereign The UK-made Sovereign comes in a heavy-duty binocular-type case. Unlike most of the others, it comes with instructions, but no mention is made of fiberglass. The separate transducer head is connected via a cord. There are both probes for wood and a disc-shaped head for hard surfaces.

Strengths Heavy duty metal case and dials. Instructions for calibration and use. Battery check (but no warning) and calibration. Remote head is compact, but must be unplugged to fit in case. Relative scale included (0-100%). Adjustable alarm and zero control. Plastic protective cover for head. Easy battery access. Pins for probing wood.

Weaknesses No power on light; easy to drain batteries. Two-handed use is awkward. Neither of its two scales are calibrated for fiberglass. Scales not evenly graduated. Pressure on head affects readings. Doesnt compensate for low voltage.

Tramex Skipper Made in Ireland, the Tramex has an analog display with three scales. The transducer consists of two large pads on the backside of the same plastic case used by the Caisson Novanex.

Strengths Light, handy. Battery on light, but no check function. Scale evenly graduated and easy to interpret. Relative scale included (0-100%).

Weaknesses Scale switch inexpensive. Three scales not sequential from sensitive to less-sensitive (i.e. #2 scale is most sensitive, #3 least sensitive). Alarm non-adjustable. Large footprint. Case appears fragile. No automatic off feature. Small display difficult to read.

Caisson Novanex Made in the UK, the Novanex has a black plastic case. The display is digital. Like the Aquant, the head is at the forward end of the case.

Strengths Light, handy. Backlit LCD display easy to read. Small footprint; easy to orient head. Hard plastic head appears durable. Adjustable zero, alarm threshold, upper end of range (0-15). Low battery indicator.

Weaknesses Case appears fragile. No audio alarm. No automatic off feature. Poor switch.

Protimeter Aquant Made in the UK, this meter differs from the others in that it transmits a radio frequency (RF) which is returned to the receiving electrode through the body of the user. Moisture in the laminate acts as an aerial that re-radiates the RF to the lower half of the instrument. This is called a free field effect. A transfer electrode or near field shield may be placed over the transmitter head for shallow readings. Placing a hand on the surface being measured affects the readings.

The transmitter head is along the forward end of the case and has a small footprint. To take readings, a single button is pushed. Readings are displayed by lighting up individual LED lights.

Strengths Light, handy. Small footprint. Easy to see readings, except in direct sunlight. Will not turn on at low voltage (8V). Space to carry spare battery. Automatic off (but time interval too short). Adjustable alarm threshold.

Weaknesses Switch not sealed. Short, coarse scale (3 flickering lights = +/-15%). No battery check feature. Case appears fragile. Head subject to abrasion. Must be held 90 to surface, which is sometimes difficult. Near field attachment unreliable at thicknesses over 0.125″.

Protimeter Surveymaster SM A relatively new product, the Surveymaster has a display similar to the Aquant, but the scale is different. Also, the transducer head is on the backside of the meter, covered with plastic, but easy to rock. The remote head and separate probes are attractive features. When using the remote head, the reading is displayed in a small LCD window.

Strengths Light, handy. Durable rubber case gasket. Remote head and probes. Easy battery access; good battery contacts. Automatic off (but time interval too short). Battery indicator. Adjustable audio alarm.

Weaknesses Head difficult to keep at 90 to surface. Because of head location on back, holding hand tends to obscure the LCD lights. No numbers on scale.

Conclusion The moisture meter is actually a fairly simple device. Some have called them glorified stud finders. A moisture meter cannot tell you the soundness of your hull laminate. But it can give you worthwhile clues on which to pursue further investigation.

In use, meter readings first should be taken in areas believed to be dry or at least typical of above water laminate. So, before checking the bottom, take readings in several areas of the topsides to obtain a general base number. Then begin testing the bottom. If the boat has just been hauled, allow some time for surface moisture to evaporate. It is best to scrape away the bottom paint and place the meters head directly on clean gelcoat.

Readings that vary significantly from the base may be worth investigating, certainly if there are blisters present. But if no blisters are present, even high readings may not correctly indicate problems in the laminate. When this is the case, you may elect to do nothing, at least for the time being. If the boat has been hauled for the winter, check again in the spring. If readings are still high (and they probably wont change a great deal if the laminate is extremely wet because it is difficult for the moisture to evaporate when entrapped), then you might consider lab analysis of a core sample or grinding down the gelcoat to reveal the inner plies of the laminate.

From the above, one can see why surveyors often rely more on their meters to measure dryness of a hull rather than its wetness. They don’t need a meter to detect surface blisters, but they do need help knowing when a hull is dry enough to recoat.

Moisture meters are also helpful in determining whether through-hull or deck fitting bedding has failed. If you get unusually high readings around, say, a deck cleat, it is advisable to remove the cleat and rebed it. If the bolts are through balsa core that is dripping wet, this may be the time to take the more radical step of cutting away the bad balsa and filling each area with an epoxy slurry.

Similarly, a meter may be helpful in determining the extent of wet coring in a deck.

After spending many hours with each of the five meters, we concluded that we prefer the Tramex for its superior ability to read through thick laminates. Had we the funds, wed also buy the Protimeter Aquant for its ability to ignore surface moisture. The near-field shield gives it some flexibility the others lack. The Sovereign, long the most popular meter, does not penetrate deeply through laminates, is awkward to use and is the most expensive of the group. The Caisson Novanex, which has the same case as the Tramex, is OK, but not our first choice. The Protimeter Surveymaster SM does not have a printed scale, forcing one to count lights or take special note of their colors. Because its transmitting electrode is on the backside, it is easy to cover the lights with your hand.

Contacts- Novanex, Caisson Audio Products, Toernooieveld 116, 6525 EC Nijmegen, Holland. Tramex, Tramex Ltd., Shankill Bus. Ctr., Co. Dublin, Ireland. Sovereign Chemical Industries Ltd., Barrow-in-Furness, Cumbria LA14 4QU England. Protimeter Aquant and Surveymaster, Protimeter North America, PO Box 450, Danvers, MA 01923; 781/938-3966. Novanex, Caisson Novanex and Sovereign available from US distributor: J.R. Overseas, PO Box 370, Kent, CT 06757; 860/927-3808, e-mail [email protected]

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Well done! My surveyor for a houseboat we purchased swore his moisture meter was telling him how much moisture was in the wall. I tried to explain the technology but he wasn’t interested… maybe I’ll send him this article :). Thanks!

THOSE *#@*ing MOISTURE METERS.

By Rob Scanlan, CMS/MMS/CACMS/IIMS Accredited, Certified & Internationally Registered Marine Surveyor & Marine Technician 52-Years in the marine sector; 38-years Accredited, Certified & Internationally Registered http://www.mastermarinesurveyor.com

I have tested and used the most expensive moisture meters available to the marine profession. These are the Sovereign Moisture Master; Sovereign Quantum and the Electro Physics GRP 33 marine moisture meters.

I do not use any of my moisture meters during my pre-purchase survey unless I test the current humidity with my hygrometer; testing also the absolute moisture in the current air; current atmospheric temperature and relative humidity. Best scenario is the yacht stored in a climate-controlled building at least 48-72 hours PRIOR TO THE SURVEY and if you ever see a marine surveyor using any moisture meter on the bottom of a hull without removing the paint, kick him in the ass and tell him “Rob Scanlan told me to do it”. It still to this day, it is amazing that I still witness marine surveyors drive up in the family SUV, jump out with their little ditty-bags; remove their moisture meter; turn it on and immediately place it on the hull or decks. These meters are somewhat useful to assess moisture intrusion into cored hulls; cored decks, or on wooden hulls. Just about every client, and many surveyors, do not understand the workings of moisture meters or the many limitation necessary to achieve a reliable reading on a fiberglass or wood hull. Moisture analysis is one of the additional tests I conduct during my survey inspections and it is not included in my pre-purchase survey fee; the fee structure for this additional testing is outlined in my website. Moisture meters for use on fiberglass hulls are essentially radio transmitters/receivers. The measurement actually being made is dielectric constant or AC conductivity, which is affected by thickness and construction material of the bottom paint, trapped water in the paint, thickness of gel coat, thickness of laminate schedule, glass to resin ratio, and absorbed water. The hull surface must carefully cleaned. A large number of random 4″ x 4″ areas of the hull must have paint or other coating removed down to the gelcoat finish. Minimum number of measurements must be equal to the approximate one per sq. meter (3.3 feet) or 50-100 on the average 40 foot yacht. The seller will usually not allow the bottom paint to be scraped as necessary for any moisture assessment. Buyers are also not up to paying the cost for the marina to haul the yacht, block, support and scrape the bottom paint and repaint the bottom for this type of testing and analysis If I suspect a serious moisture problem, such as water intrusion in a cored hull, the meter may be used to try to determine the extent of the damage. There are a couple of different types of meters and several brands and detailed discussion would include terms like impedance, dielectric constant, capacitance, resistance and conductance but basically they measure how much electricity a hull-material can store or conduct. A simple analogy would be to suggest that they send out a signal and measure the difference in the sending-signal and the return-signal, thus measuring the conductivity of the hull material between the sending and receiving units. Wet fiber glass or core hull construction would be more conductive in theory than dry materials and therefore show a higher reading on the meter. There are many things that can confuse a moisture meter and extensive experience and training is required to make proper use of them. They actually measure capacitance rather than moisture, highly conductive materials will show higher readings on the meter whether or not they are saturated. You cannot put a moisture meter on a dry piece of steel it will show a very high reading just like a saturated balsa coring in the deck. If the gelcoat contains a lot of titanium dioxide which is a common white pigment with high dielectric constant, the meter may in fact read high depending on the pigment concentration. Place a meter on the outside of a hull with metal fittings, anchor chain, water hoses or fuel tanks in contact with the hull, the meter will read high. If there is a saturated blister deep in the laminate schedule, the meter may show dry as the moisture is too deep for the weak signal of the meter to penetrate the laminate schedule. If water saturated balsa coring has separated from the deck skin, the meter may read dry as there is no contact for conductivity. If the bottom of the hull is epoxy coated, the meter may read low due to the insulating characteristics of the epoxy. As they send out a very weak signal, these meters do not measure accurately much more than 1/4″ deep and not more than 1/8″ deep on some laminate schedules although manufacturers claim up to 1″. Many unnecessary epoxy bottom applications are started by the improper use of these moisture meters and many more of these jobs fail for the same reason. Keep in mind also that the meter is actually measuring the conductivity (or capacitance) of the material, consideration must be given to the fact that the fiber/resin ratio, whether chopped strand, woven roving or fiberglass mat and different types of resins will all have an effect on conductivity. The bottom, topside, deck areas and superstructure of a yacht will often have various laminate schedules and construction techniques all of which again affect conductivity. The average 30′ uncored hull can absorb 30-40lbs. (approx. a maximum of 2-3%) of water and it can take months to dry out…if ever. The only way to accurately measure moisture content is to cut a piece from the hull, weigh it, bake it for a couple of weeks or burn it, weigh it again and measure the difference. These meters may give an indication of relative moisture content or at least point out moisture problems. Once these problems have been detected and confirmed by examining the inside surface of any area for causes other than moisture or perhaps removing an area of bottom paint and testing again. Testing and identifying a confined area wet or dry does exactly that and in just that one area. Assuming the same substrate (the lay-up is likely different in several areas of the bottom), these meters may show different levels of moisture across a specific area. This can be instrumental if the bottom has been stripped of all gelcoat and you are trying to determine if it is dry enough to accept an epoxy barrier coat. If the meter reads higher content when the hull is first stripped, and lower moisture content a few months later, then moisture content has been reduced. If after another two months the meter still reads that same lower moisture reading, then the hull of the yacht will be as dry as it will get. Moisture content is in no way an indication of blistering. What is osmosis? The problems start to occur when the water molecules migrating into the GRP (fiberglass) encounter other chemicals inside the laminate, primarily water-soluble materials (WSMs) such as the emulsion binders used to hold the fiberglass mat together before it is moulded, or pockets of uncured or partially cured resins in the hull mould. The water molecules can have a chemical reaction with these substances, forming larger molecules of a new chemical, often acidic – which unlike the original small water molecules, can not carry on passing through the GRP. These larger molecules are then trapped. This is the point at which osmosis actually starts. The important parts are that the hull is not waterproof (it is a semi-permeable material), and that osmosis causes a low concentration fluid (water) to pass through the hull to join the higher concentration fluid (the chemical mix formed by the water plus WSM) inside the fiberglass laminate schedule. Pressure is thus built up inside the laminate. If this process takes place in a solid part of the laminate, there is usually no problem as the structure is strong enough to contain the pressure. If however it takes place on the boundary of a small air-bubble in the moulding, or at a point where layers of fiberglass are not properly bonded, the new chemical compounds slowly fill up the bubbles or the very small gaps between layers with liquid. Almost all mouldings have these air bubbles and small areas of poor bonding, although they should not. Ideally the resin should totally fill the gaps between the fiberglass strands, and every layer should perfectly bonded. This is extremely difficult to achieve with conventional moulding techniques. The process of osmosis in a fiberglass hull is very slow, unless the moulding is a poor lay-up schedule, and no matter how long it remains in water a typical fiberglass laminate cannot absorb more than about 2-3% of its own weight of water. If this osmosis (using the term in a correct manner) was all that happened, it would be a very minor problem. Even completely saturated with water molecules, a fiberglass laminated hull still retains most of its strength, although it does become slightly more flexible. Racers who want stiff hulls with the absolute minimum weight already mostly keep their boats ashore when not sailing, and for any properly built cruising boat 2% or so extra weight and a trace more flexibility in the hull-structure should not be a problem. Once again, if the air bubble simply filled with this acidic compound, the problem would still be relatively minor. However the nature of the osmosis process is that water molecules keep osmosing through the fiberglass laminate, and join the chemicals in the bubble, steadily building up hydraulic pressure. Eventually this causes the surface of the moulding to blister. These blisters are the typical sign of what I refer to as ‘osmosis’. When pierced these blisters will give off a small amount of chemical-smelling (usually vinegary) liquid – which is the juice built up inside the pressure-raised blisters. The term ‘blister juice’ is often used. This ‘blister juice’, which is usually acid, can break down the polyester. This breakdown process is known as hydrolysis, and causes a reduction in strength of the laminate. This is however normally very localized, and the moulding as a whole will still retain most of its strength despite blistering. Only if the blisters are very large, or very deep-seated, is this generally a problem.

There are those who will tell you that meters are easy to use but I don’t believe that is the case. There are many things that can confuse them. It’s important to understand how they work before you can know what they are telling you and whether you can trust the readings or not. So first a few facts…..

Moisture meters do not measure moisture. Fiberglass (the resin) is not waterproof, it is hygroscopic and polyester resin is water soluble (in 2 – 200 years …. it depends).

No meter can accurately tell you a percentage of moisture in fiberglass or composite cored structure. That’s not how they work. All production boats have areas of different resins, laminate and core that will give different readings whether wet or dry.

Good article technically, but out of date now as nearly all manufacturers have more recent models. I am a surveyor and like the majority rely on more than one meter as we recognise the differences and gain a greater understanding of measurements that way. For instance the Tramex has deep and shallow scales but deep scale will react to bilge water and metal items stowed in lockers. shallow scale is really only surface response. Sovereign’s Quantum has two scales that are much better graduated and is vast improvement of the old Sovereign tested in the article, but company has now gone bust so meters can no longer be re-calibrated.

Richard T…. Barrier coats behind the exterior gel coat it is possible to obtain erroneous high moisture level readings. The test results are exaggerated when taken from the exterior gel coated surface of the hull. The composition of said barrier coat is such that the coating may be electrostatically conductive. This can produce higher than normal readings on boat hulls containing barrier coats with certain conductive pigments.

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