Birch Plywood in boatbuilding

I am sort of beginner in all boat business - however I do have patience.
I live now in the US and am a "proud" member of the rat race in South Cali.

However I will be moving back to Finland in 5 or so years and will have family farm with its ample space to work on things. I am building up momentum into starting some sort of boat projects and I know that you can get really nice birch plywood at very reasonable prices back home.

As mentioned here, bare birch is not rot resistant - so I would be curious to hear from other people's experiences in using it in stitch and glue / cold molding aplications where it would be totally sealed with epoxy.

Thanks,
Heikki

 

Birch Plywood

Heikki, birch is a very pretty wood and the sap makes a great home-brew wine (as an old Scots Highlander I know) but like most soft woods when converted into ply is easily bruised. Sure you could use it for boat building- BUT - it will need to be throughly sealed both inside and out - and in doing so you'll lose much of its natural beauty. Unless of course you intend to hide it under several layers of paint ( and that would be a pity).
But (and here's the Highland Scot coming to the fore) if it's cheap and plentiful - then go for it. But, I repeat, make sure its well sealed. And do constant checks for scratches and chips. Patch them instantly.

 

Another note is to insure the plywood panel has a proper rating for it's intended use, such as BS 1088. Many birch panels are "cabinet" grade which don't use water proof glue in it's construction (not good in a boat) and these panels also have paper thin outer veneers of birch with junk wood inside. The outer veneer should be darn near the same thickness as the other, interior veneers, to provide strength. For use inside the boat as furniture and non-structural applications this is fine, but for exterior uses, like on the hull, deck, cockpit, cabin sides/top, you'll want the best stuff you can get, with good rot resistance, water proof glue, quality (panel) construction and strength.

 

kerosene
Here is a picture of an Open 60 (Ocean Planet) that has done two single hand around the world races. Extremely punishing conditions did not harm it's birch ply deck. To be exact it is 2mm aircraft Finn birch on either side of 25mm Nomex impregnated Kevlar honey comb. Light and bigtime strong. With a few patches of carbon reinforcement to take some of the larger tension loads it was bulletproof and showed no signs of movement or fatigue.

 

Birch in Boatbuilding

What a great picture DGreenwood Senior - taken by a camera strapped to an albatross no doubt - unless the camera like the albatross was hung round your neck But a superb shot however taken.
And PAR - excellent advice as ever. And typical of me to overlook the most important fact. As is becoming my catch-phrase Heikki: "Listen to your Uncle PAR." Check the quality of that ply.

 

The really great thing about that shot is being able to see the consistant sail shape from bottom to top even though it is quite a flexible unstayed rig. When that thing flexes like that it scares the bejeezus out of you but it is fact very reliable. Bruce never had to climb it during the race. Many others did.

 

Dod a boil test on some baltic birch type stuff once. It passed with flying colors. Then stored it in a damp place, and all panels became lumpy, like a 3d topographical map of Louisiana. It might have laminated okay, to build up bigger chunks, but as panels, no way. Was this stuff defective? Dunno.

Alan

 

alan
Birch ply is very prone to mold. I have seen it turn black almost over night. When protected properly it is really tough. Many airplanes are built with it.
As Par says, you gotta make sure you have the right stuff before you can screw , glue or guarantee any thing.

 

I'm sure that's right, DC. I guess it all depends on one's construction methods. Cost could be offset to the ply or the means to protect it. I avoid epoxy as much as possible---- glue with gorilla glue above the waterline (Just spliced a mast with gorilla glue yesterday).
I would always favor the material that lives well under a coat of paint alone, but then, I'm very low tech.

Alan

 

This boat is built of meranti, pine and birch plywood. The birch is stained to look a little like mahogany (I guess). The builder bought some epoxy from me and I don't know much about the design.

The whole story here:
http://home.broadpark.no/~okvien-1/baat/index-e.html

The birch deck here:
http://home.broadpark.no/~okvien-1/baat/e33.html

 

It would be interesting to see how some older boats have fared. I'm wondering if birch ply is necessarily married to epoxy encapsulation.

A.

 

Okoume (for example) is not very rot resistant either, so if birch is treated right it may last. I would suggest epoxy and a light (160g) cloth.

Birch is quite strong:
(from http://www.treteknisk.no/fullstory.aspx?m=721&amid=3599)

 

It is apparent that birch ply is prevalent for the reason that it possesses all of the features that make it great for house cabimetry and furniture----(availability of stock, uniformity of grain, gluability, etc.). Probably why other more rot-resistent woods are not as widely used. I'm thinking of spruce, cedar, cypress, etc.
Those are softwoods, of course, but panels would be thicker at the same weight, and hence stiffer for their weight.
Birch is very cheap here compared to ANY other ply except possibly phillipine mahogany, for example. Last kitchen I built, it was under $40 per 1/2" (12 mm) sheet for cabinet grade and while one cherry facing kicked the price up to double that, birch was always on the back face if specified with one cherry face.
I imagine that a manufacturer that had some process of treating plys with mildewcide, etc., could produce decent panels not requiring full encapsulation, and that would make a pretty good marine panel.
Most of my exterior boat structure (only hull is fiberglass) is marine fir, which appears fine under paint alone after perhaps thirty years.
Epoxy is expensive, messy, and time consuming for the small boat home-buider. If fir marine ply were even twice the cost of equal replacement birch ply, I would factor in the savings in epoxy and time to get a true cost and I'm guessing the fir would actually be cheaper, all things considered.
Have you ever analyzed this comparison?

Alan

 

Birch is a fine wood and can be used, but it will need some protection. The best, of course, is entombing it in plastic (epoxy), but well cared for painted panels could do okay.

Since you have the availability, check the glue used (needs to be WBP), the general panel construction (number of voids, repairs, veneer count, etc.) and use the stuff, with an eye toward protecting it against abrasion and moisture ingress. In my mind this means well coated with epoxy for hull and weather deck applications, with cloth sheathing in high traffic or exposed areas (exterior hull surfaces, soles, etc.).

 

Birch veneers were used after WW2 by Fairey Marine when they started building their hot molded wooded boats.

There are plenty of the early Fireflies, Nat 18's, Swordfish, Albacores around after 60 years that haven't ever seen a drop of epoxy.

I believe it was cost that triggered the move away from birch in the 50's.

But as PAR said, there is a lot more to plywood than just the wood species.