The right wood for the job

[Meerkat]

In boat framing, are there different woods whose properties make them a better choice for different applications in the boat? I can see that a heavy, dense, rot-resistant wood would be good for a keel. What about stems, floors and breasthooks etc.?

I've seen a fair number of boats with a pale yellow wood (pine?) used as floorboards - is this a traditional use or are there good reasons to use this particular wood for this application?

[Tar Devil]

I've been asking the same question. These are some the the comments I've received...

Are you gonna glue the frames or fasten them with bedding? If fastening, white oak is hard to beat. If gluing, something other than white oak... perhaps mahogany (expensive), or douglas fir (tends to split), and perhaps longleaf yellow pine (a bit heavy). So I'm told, anyway.

I'm still wrestling with that decision on my dory. I'm leaning toward oak frames and breasthooks, fir chines/keel/sheer clamps/stem and stern posts, pine sole, and mahogany knees for the seats. And I've love to fashion my seats like this out of teak or mahogany...
http://us.f1.yahoofs.com/users/fd747376/bc/Boats/NOR_08.jpg?bc_Jhv9AOwrHiTTH

Later,

Phil

[Meerkat]

Hey Phil;

Meranti mahogany is one of the cheapest woods out west right now at $3.50/bd.ft. I think honduras is $5.

I've been considering brazilian cherry or purpleheart for keel, knees and breasthooks (double-ender) with meranti thwarts, floors, c/b trunk trim, gunwales and inwales with pine floorboards. Hull interior beige and exterior white with a bright sheer strake. Fore and aft decks to be faux laid deck over plywood. I thought about doing those in teak, but Iroko is much much less expensive. The pic you posted now has me thinking about meranti for that too...

I wonder how purpleheart would do as a mast? It's within pennies of the same price as meranti and that's HALF the price of Fir!

I hope my boat comes out half as good as that pic - thanks for posting it!

[dale o]

For masts and spars you need to look at the engineering properties of the wood. Thats why doug fir, sitka spruce and some pines are used for masts on sailing ships. Strength properties and strength to weight ratio are more important than cost here.

[botebum]

I'd have to agree with Dale O on this one. $$$ is a consideration but the tried and true are still the tried and true for a reason.

[Bruce Hooke]

While each part of a boat calls for particular properties that might point to certain woods I think we can break things down into a few basic categories and identify the traditional woods used for each (at least in Eastern North America).

Frames, stem, keel, floors, deck beams and other similar structural members -- what we are looking for here is high strength and very good rot resistance. Bendability with steam is also a consideration in some cases, mostly for frames. White Oak is the traditional solution because it is strong, rot resistant and steam bends well. The questions around glue-ability are its one downfall. On a boat where weight is a particular issue a lighter weight wood such as mahongany or even spruce might be used for the deck beams, although spruce has little rot resistance. "True" Mahogany ($$) will also work well for many of these parts as will various other tropical woods with similar properties.

Planking and Ceiling - Here strength is an issue, as is rot resistance, but weight is also important and it is also helpful to have a wood that doesn't shrink and swell too much for the planking. Some traditional woods for these areas are White Cedar (on smaller boats), Long Leaf Yellow Pine, Douglas Fir, Mahogany, Cypress and Teak, although Teak is rather on the heavy side for a small boat.

Decking - Similar to planking so the same woods are often used, but on lightweight boats rot resistance may be sacrificed in favor of weight so Pine or Spruce may be used.

Masts - Lightweight but strong are the essential qualities here and for this the Spruces, and especially Sitka Spruce, are unsurpassed despite their very limited rot resistance. Other softwoods such as Pine and Douglas Fir are also traditional. Another important factor for masts is that you need long pieces of wood, and again softwoods tend to be good in this area.

Non-structural members -- on small boats this is mostly floorboards and thwarts. Thwarts do add some strength but they are much larger than they need to be for strength purposes so the priority tends to be on keeping things light, and the same basic idea applies to floorboards. So, Pine, Spruce and White Cedar are traditional here. Cedar is especially good for floorboars since it is rot resistant and floorboards are often wet. If weight is not an issue then many other woods may be used just for looks. The same logic applies below-decks for the all the joinery work in the cabin -- if weight is a priority then use lightweight woods like pine and spurce, but in many cases a bit of weight is sacrificed for looks.

Of course this is just an overview and various other factors such as the size of the boat and how it will be used need to be factored in, but the basic principles are the same -- if you understand what qualities a part needs then you can identify a wood that has those qualities...

[Ross Faneuf]

I've used both South American and Meranti in laminations. SA is more attractive and stronger. Meranti has a very coarse grain structure, which actually make it quite good for laminations; epoxy actually does saturate right through it (which doesn't happen with SA). Depending on source, it may be very poory treated during seasoning - that is, it may be seasoned at too high a temperature making it brittle. That was true of the last batch of meranti I had, which was extremely weak and brittle - virtually unusable. So bad that I have never looked at it since.

A lot of SA isn't great either, but I've had much better luck - particularly where I can pick it. Here on the east coast, some suppliers segregate SA into straight grain (like what used to be Select), and reserve it for pattern makers. That take the highly figured grain and reserve for cabinet makers. They sell the rest (somewhat more cheaply) to boat builders and the like. I still have gotten a fair amount of good stuff this way.

SA glues very well, and is usually adequately strong. It prices out cheaper than most cabinet hardwoods, and out here is comparable to true white oak. Much depends on your supplier.

The cost of the wood in a boat is significant, but often less important than many other things - like fittings, fastenings, epoxy, and finishing materials. To say nothing of sails. Don't be tempted by notions of false economy to attempt to work with any inferior woods. It won't pay.

[DavePulaski]

It looks like I'm going to be using a variety of mahoganies for all the solid timber components of the Acorn 10 (except the floorboards, will probably use cedar for those). My local hardwood mill (Praise be to the Woodery!) has a pretty good stock of SA, African, and Philipine mahogany.

I picked up a wonderful piece of 8/4 philipine that I'm going to rip into strips for the stem laminations; some 4/4 SA for the hog, keel, skeg, and transom, and a few board feet of 3/4" Meranti for an as-yet undesignated purpose.

[Meerkat]

Ross, how can you tell by looking, if you can, whether or not Meranti has been seasoned properly? Would Barrett know? smile.gif

[EdenRose]

Meerkat,

Get a book called "Understanding Wood: A craftsman's guide to wood technology." by R. Bruce Hoadley. (If you want it new it is at Amazon.It is like getting a little music theory
before picking up the violin).
It covers every aspect of wood from a tech point of view. Strength, drying,gluing, selecting etc. There are lots species comparison
charts for rot, stress, strength, etc
It would have saved me a lot of money on
inappropriate or bad wood for my current project.
I cut a fir down for my mast and pretty much turned it into firewood because I got the book a little late in the process. (Thats ok I needed some way to heat the epoxy up this winter)
There are lots of good pictures that show the
effects of bad seasoning and drying.

[ 10-01-2002, 12:50 AM: Message edited by: EdenRose ]

[Ross Faneuf]

In my case I was working with meranti veneer. It was too brittle to bend much; I'd simply flex a sheet and if it broke it was no good. You could always rip a, say, 1/4" strip and see if it seemed reasonably flexible; it should tolerate around 25" radius before failing.

A really crude test; but relevant to doing lamination work.