boat building materials

Hardwood for boat building

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Hardwood is wood from angiosperm trees (or in other words non-monocot angiosperm trees). It may also be used for those trees themselves: these are usually broad-leaved; in temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen.

Surprisingly enough there are about a hundred times as many hardwoods as there are softwoods. Hardwood contrasts with softwood. Hardwoods are not necessarily harder than softwoods.

Below you will find a shore description of the most used hardwoods in boat building. These woods are teak, mahogany, oak, ash, beech larch and birch.

Teak

Picture of teak wood

Teak is hard and moisture resistant. It resists warping, cracking and decay and is the number one boat building wood for outside use. It’s used for boat building, hull construction, shipbuilding, flooring and decks.

Mahogany

Picture of mahogany wood

Mahogany is a fine-grained wood with reddish brown color. It is highly durable and can resist swelling, shrinking and warping. Mahogany is widely used in boat building but is not as durable as teak. It’s used for boat building, hull construction, interior and decks.

Oak

Picture of oak wood

Oak has good bending qualities apart from being durable due to the high natural content of tannic acid. It finishes well and resists moisture absorption. Oak is good for ship building, planking, frames, keels and general where strong wood is necessary.

Ash

Picture of ash wood

Ash has superior bending qualities due to the long strait wood veins. It doesn’t finish very well and is not really durable. It is the number one choices in boat building for bend frames.

Beech

Picture of beech wood

Beech is normally not good for boat building since it has terrible bad durable properties. However it has been used in shipbuilding for keels and underwater hull planks since it’s just as durable as oak if kept wet all the time. Else beech doesn’t have much interest for boat building.

Larch

Picture of larch wood

Larch has fine durable properties. Normally considered to be somewhere between pine and oak in durability. Larch is great for hull planking due to the long strait wood veins and it’s possible to get even really long lengths without any knots. It finishes well and resists moisture absorption.

Birch

Picture of birch wood

Birch is the number one plywood veneer. This is due to birch’s extremely fine properties for cutting in thin veneers or peeling. If you use it for stitch and glue boat building make sure it’s sufficient protected from moister.

Happy boat building,

Morten Olesen, Naval Architect
http://www.boatplans.dk/

Softwood for boat building

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The term softwood is used for wood coming from conifers trees that stay green all year round. Therefore it has nothing to do with the wood being soft or not. In fact you can find some softwoods that are harder than hardwood 🙂

More than 80% of the world’s timber production is softwood. This timber is mainly produced in Scandinavia, Baltic, Russia and North America.

Below you will find a shore description of the most used softwoods in boat building. These woods are pine, fir, spruce and cedar.

Pine

Picture of pine wood

Pine has a uniform texture and is very easy to work with. It finishes well and resists shrinkage, swelling and warping. It is widely used in paneling, decks, bulwark and for spares. Pine has a strong core and is therefore really good to laminated spares.

Fir

Picture of fir wood

Fir is uniformly textured and has low resistance to decay. It is nonresinous, works easy and finishes well. Fir is used for making plywood, veneer, paneling, interior trim and spares. Fir has a relatively weak core and is strongest at the rim. This means that if it is used for spares the bark should just be removed from the trunk and as little as possible machining of the wood.

Spruce

Picture of spruce wood

Spruce is a strong wood that finishes well and has low resistance to decay. It possesses moderate shrinkage and is light. It is also fine for spars, crates, boxes, general millwork and ladders.

Cedar

Picture of cedar wood

Cedar is a reddish wood with sweet odor. It is very easy to work with, uniform in texture and is resistant to decay. Cedar is extensively used for interior decorating, closet lining, deck planks and strip plank boat hulls.

For the pine, fir and spruce it is normal to see some local quality variations where the wood from trees growing slow in cold places get a special nickname. This give the signal that this is a special superb variant where there is close between the rings. Some of the special designations are Oregon pine and Kalmar pine.

Happy boat building,

Morten Olesen, Naval Architect
http://www.boatplans.dk/

Fiberglass and epoxy

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Boat building with stitch and glue includes fiberglass and epoxy. I have set up some information about this topics so you can study the materials a bit more below. Enjoy 🙂

Fiberglass tape

Fiberglass tape

The fiberglass tape can be of any regular available type. One important thing is that you choose a tape with the minimum weight as specified for the boat building job you are doing. If your normal supplier does not have the weight specified choose the nearest weight above.

Fiberglass fabric

Fiberglass fabric

Most of the designs from my company do not require fiberglass fabric on the entire hull. Basically it is a choice omitted because the fabric often makes the finish work more difficult and result in a heavier boat. For most designs the strength of the plywood is more than enough so fiberglass fabric is not necessary.

However you can choose to cover the hull with fiberglass fabric to get better durability and easier maintenance over the years. If you choose so my advice will be to select a crowfoot woven fabric. The crowfoot weave has the advantage that it will be totally invisible when wetted out with epoxy.

Epoxy resin

West system epoxy

You can get epoxy resin for your new boat from many suppliers and manufactures. Choose the supplier where you get the best service and guidance, also if something turns out not exactly as you suspected.

You can get epoxy resin with different hardeners. Some uses slow hardener and some uses fast. If you can’t find a hardener with a curing time that fits your need it is often possible to mix the hardener. This means that if you would like to have a gel time between the slow and fast hardener you simply mix the two and achieve a gel time in between.

Some manufactures make a special tropic hardener. It’s very fine for laminating in warm areas. You will then have time to apply and work with the epoxy even if the temperature reaches 43°C (109F).

Filler

Wood flour

The filler is applied to the epoxy resin to make it thicker. The thickened epoxy is used for gluing the different hull parts.

For most of my designs you can use ordinary wood flour. Basically the wood flour is some fine and very clean sawdust, and in principles you can make it yourself.

One advice for working with thickened epoxy is to make the seams as nice and fair as possible before the glue sets. Believe me it’s much easier to work with before it sets than having to fair it with sandpaper after.

Happy boat building,

Morten Olesen, Naval Architect
http://www.boatplans.dk/

Plywood part 3

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When going to your lumberyard you can find several different plywood grades. It is not always obvious what the different designations stand for but I will try giving you an overview of some of the most normal grades plywood comes in.

Grade N veneers
Grade N veneer shall be smoothly cut 100% heartwood or 100% sapwood, free from knots, knotholes, pitch pockets, open splits, other open defects, and stain. The veneer shall consist of not more than two pieces in 1220 mm (48-inch) widths and not more three pieces in wider panels, and shall be well matched for color and grain.

Grade A veneers
Grade A veneer shall be firm; smoothly cut; and free of knots, pitch pockets, open splits, and other open defects and well jointed when of more than one piece.

Grade B veneers
Grade B veneer shall be solid and free from open defects and broken grain, except repaired smaller splits, openings, knots and cracks or checks. Slightly rough grain shall be permitted. Minor sanding and patching defects shall not exceed 5% of panel area.

Grade C veneers
Sanding defects shall not impair the strength or serviceability of the panel.

Grade C Plugged
 veneers
Knotholes, worm and borer holes, and other open defects; sound and tight knots; split; broken grains; pitch pockets; plugs; patches and shims shall be permitted. Where grades having C Plugged face veneer are fully sanded, sanding defects shall be the same as admitted under B grade.

Plywood with plugs

Grade D veneers
Any number of plugs, patches, shims, worm or borer holes, sanding defects, and other characteristics shall be permitted, provided they do not seriously impair the strength or serviceability of the panel.

The above list is not a fully description of all the grades available but I am pretty sure it will cover most of the plywood you’ll find at your lumberyard.

Oh, and one last thing. Remember always to buy plywood that are glued with water and boiling proof glue. That is normally stated with a WBP mark.

Happy boat building,

Morten Olesen, Naval Architect
http://www.boatplans.dk/

Plywood part 2

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You can get plywood in many different qualities and versions. The price differs a lot depending on what you choose. The different plywood grades are normally designate in accordance with the surfaces and the core.

The most superior plywood for boat building is of course marine plywood. For a large variety of applications it is excellent but for some applications it might be overkill to use marine plywood.

Picture of marine plywood

For most backyard and home build boats it is fully acceptable to use exterior grade plywood. It is always recommended to prime the plywood with epoxy resin in order to make the plywood moister resistant.

I have for many of my own boats used cheap Brazilian plywood in grade B/C and it has worked fine without any problems. Below you can see the different grades for plywood. The B/C grade means that one side is B-grade and the other is C-grade.

Beside the grades it’s also possible to get plywood with a specified surface veneers. This means that you can have the plywood with whatever you prefer, mahogany, birch, teak, ash, beech etc on top. One thing though, this won’t make your plywood cheaper buying with some special veneers on top 🙂

And there is still more to plywood than this… In the last part of this series I will give you a overview about the different grades you can typically find in your lumberyard.

Happy boat building,

Morten Olesen, Naval Architect
http://www.boatplans.dk/

Plywood part 1

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One material that is often used when for backyard and home boat building is plywood. You can get a large variety of boat plans using the stitch and glue building method. My own company Boatplans.dk is also dedicated to developing and selling boat plans for stitch and glue plywood boats.

Picture of plywood and the different plies

Plywood is thin sheets of wood glued together and each ply has the veneers going perpendicular to the next ply. As you can see on the picture there are always an uneven number of plies. This is so the surface plies have their veneers going in the same direction. This is really handy when cutting the plywood.

The properties of plywood are in many ways superior to that of wood. Since the plies are glued together the dimensional stability is really good, meaning it’s possible to join plywood with epoxy and fiberglass.

The plies are glued together and this gives the main disadvantage for plywood in a wet marine environment. If the glue is not right and the plywood not sufficient protected from water the plywood will delaminate and the structural integrity of the boat will be compromised.

But there is more to plywood than this… The next part of this series will deal with the fact that plywood can be bought both cheap and really expensive. So which grade should you choose?…

Happy boat building,

Morten Olesen, Naval Architect
http://www.boatplans.dk/