Baltic Birch for transom recore ?

[linear]

Checked out sheet for for a transom recore on a 26' twin I/O boat. This stuff is marketed as premium underlayment material. Says all plys Baltic Birch, no voids and exterior glue. Looks like good stuff, flat & smooth and 9 plys I think.
This is about $55 for a 4x8 sheet of 1/2" nominal thickness, will be laminating 3 sheets one at a time in the boat.
Is it worth using this or would plain old cheap ext ply work just as well for core material?

[alan white]

A transom on an otherwise cheap old boat might not warrant top shelf materials, but an otherwise high value boat deserves better stuff.
The wood you should be investigating for a transom replacement for a reasonably nice boat would probably be Douglas fir, two layers in your case,3/4" marine plywood. The transom is subject to a lot of issues--- it sits in water with a drain hole below the waterline, has motor mount or outdrive bolts passing through, a great force pushing on it, in short, you want the best materials and methodology when you build it.
The 3/4" marine ply would require only one gluing, half as much. The three 1/2" layers will eat more glue and time.
As important is that you encapsulate the whole panel in epoxy (three coats usually) before you attach it to the boat. The holes for bolts, fittings and drain and other holes all need to be given a lot of attention since they are just about always the source of water ingress, and no doubt the cause of the original transom problem.
Those holes all need to be oversized to begin with and jacketed by epoxy rings (prior to glassing is best).
Any case, the bottom line is use the materials that contribute to a boat that is made up of parts that have similar longevity and value. If it's an old work skiff you want to get another five years out of (because the whole rest of the boat is nearly played out, go quick and dirty and cheap. But if it's a gold plater, don't chase that with materials that would detract from its value.

[TeddyDiver]

Baltic birch has rather high sugar content which makes it a good ground for mildew etc. So if used monoethyleneglycol before epoxy..

[mitiempo]

Baltic birch is not waterproof but water resistant. If you take a square of it and boil it you will see the plies separate. I did this before using on my boat rebuild. I do use it where water is not an issue - for interior joinery where it is either painted or epoxied and kept out of the bilge in any case. For structural and possibly wet areas I use Joubert ply which I believe is the best available. Not only are there no voids but every ply is void free to start with and not pieced whatsoever. It is Lloyds approved. I think a piece of exterior grade fir is more waterproof than the baltic birch and the boil test would prove it to be so or not. The problem I had is that good quality marine grade fir is almost unattainable locally (Victoria B.C.) and exterior while probably as waterproof as most is full of patches and lousy looking surface veneers but if it will be encapsulated in epoxy and biaxial cloth or similar then it would be ok in this regard. It will have voids though and you have to watch out for these. Here is a link to Joubert: http://www.westwindhardwood.com/PDF/Jourbert/JOUBERT-SalesBrochure-ENG.pdf
Brian

[apex1]

Do´nt use birch ply for marine applications! Although the material of choice in aviation, it does not do well on the water.
Use a hardwood marine ply instead. All the "Mahogany" substitutes, like Okume, Sapeli and so on.

Regards
Richard

[tkk]

If you plan to use it you want to get more specific information about the mfg country. If it is Finland the glue used will stand the boil test and you only have the rot/mold to worry about. :p

If it was made in Russia or Estonia you don´t want to touch it with a two meter pole.

[apex1]

If it was made in Russia or Estonia you don´t want to touch it with a two meter pole.

Well, the best quality actually is made in Russia! (and the highest quantity too) it is completely DIN EN ISO standard and stands every common test as the best.
And Estonia btw. is the number one country in terms of efficiency in the whole EU. The Baltic Suisse.......

sorry to contradict you completely
Richard

[tkk]

How come they sell us only the cheap and non-waterproof stuff?

All the cheap no-good plywood in Finland seems to come from former Soviet states, wheras all the domestic production has been glued with waterproof stuff for decades.

[apex1]

How come they sell us only the cheap and non-waterproof stuff?

All the cheap no-good plywood in Finland seems to come from former Soviet states, wheras all the domestic production has been glued with waterproof stuff for decades.

I have heard that there is very crappy stuff around the Baltic, but do´nt know where it comes from. It may be (just a wild guess) that they export mainly to central Europe (the good quality).
The Finnish was (and is) known for being first quality thats true, but the Russian at present is better.

No offense meant.

[alan white]

I'd try Baltic Birch if it were cheap AND it passed a boil test (I bought a booty-load of 1/4" once for very cheap, but did the boil test).
However, other plywood doesn't need to be tested every time. It's also going to be a wood species that holds up well in the marine environment even if it does get wet. That's why I'd use fir in a transom. It isn't best for many applications due to the surface changes it can go through, but otherwise it is reasonably light and ultra-strong.

[apex1]

DO NOT GO FOR BIRCH PLY IN MARINE ENVIRONMENT

That was clearly stated (and backed by arguments) above.

[Steve W]

Apex, Im curious as to why are you so adament about not using baltic birch plywood in a marine enviroment? if you are concerned with resistance to rot it is rated as "non durable",the same rating as Okume which you seem to approve of so obviously either panel will require epoxy protection, as someone suggested,one should do a comparative boil test of the birch before using it to test the glue line but throw in some known BS1088 Okume samples as a baseline. Ive been seeing the Baltic Birch in the lumber yards and have been very impressed by the construction as pointed out by the OP but have not yet done the boil test myself. As Alan has pointed out Doug fir is very strong and "Moderatly durable" but unfortunatly the construction of every panel i have ever seen is woeful,we make the worst plywood in the world here in the US, a good reasonably priced panel with the same duability rating as fir is BS1088 meranti which i find offers good value for the money where weight is not an issue,unfortunatly you cant just walk in to the lumber yard and pick up a sheet so its worth exploring the Birch option.
Steve.

[apex1]

one should do a comparative boil test of the birch before using it to test the glue line but throw in some known BS1088 Okume samples as a baseline.
Steve.

Well, if your coice is between devil and satan, of course it is worth to try birch ply too. I do´nt know the quality of US ply from own experience, have just heard (mainly here) that it is almost all crap.
As I stated above it is a perfect material in aircraft building (a top quality Birch) but a weak one when wet. And Teddy brought another point up, the sugar content. It rots much faster than, for example, the Mahogany substitutes. The boil test is a obligation, no matter which ply you buy, but thats common knowledge I think.

Richard

[petethai]

[QUOTE=apex1;290437]Well, if your coice is between devil and satan, of course it is worth to try birch ply too. I do´nt know the quality of US ply from own experience, have just heard (mainly here) that it is almost all crap.
As I stated above it is a perfect material in aircraft building (a top quality Birch) but a weak one when wet. And Teddy brought another point up, the sugar content. It rots much faster than, for example, the Mahogany substitutes. The boil test is a obligation, no matter which ply you buy, but thats common knowledge I think.

the answer is not so simple
this is traditional believe, or opinion about wood.
now we have reforestation, that means, different chemical composition of wood. type of soil, climate changes etc. etc.
Russian birch plywood is as good as marine plywood, probably better. we don't know where they buy basic materials for this plywood. globalization of market, means maybe old forest wood or fast growing one. swamp birch is rot resistant, white birch is not. American mahogany is not the same as Malaysian or from Philippines.
we are talking about biochemistry and molecular biology of lignification, lignin content in the heartwood, sapwood and earlywood, growth rate, weight density.
what about clones.
120000 fungus
Russian birch plywood properly protected with epoxy, will be as good as marine plywood, even better.
quality of production process is very important.

we should be careful, with our answers
pro publico bono

[apex1]

this is traditional believe, or opinion about wood.

There is no place for opinions or belief in professional boatbuilders statement.

Russian birch plywood properly protected with epoxy, will be as good as marine plywood, even better.

No, it will not! After all it is weaker by fibre than the usual hardwood used in the EU.

quality of production process is very important.

First grade marine ply is first grade marine ply, I did not compare US crap with that.

we should be careful, with our answers
pro publico bono

Absolutely right!

[liki]

How come they sell us only the cheap and non-waterproof stuff?

I would suspect the importers to be the culprit here.

[petethai]

I am not American, so I don't know about US crap.
But I am in the process of preparing information about plywood for my new boat. I find this:

http://65.23.157.7/cgi-bin/woodsearch.cgi?comparing=166&comparing=142

and this

http://65.23.157.7/cgi-bin/woodsearch.cgi?comparing=166&comparing=470

it looks good for me, I am talking about birch characteristics.
Also I checked some information about rot resistance for birch , oukume and sapele

"Precise ratings of decay resistance of heartwood of different
species are not possible because of differences within species
and the variety of service conditions to which wood is exposed"

http://www.fs.fed.us/ccrc/topics/urban-forests/docs/physical%20properties%20and%20moisture%20relations%20of%20wood.pdf

I don't see any advantage of okoume or sapele.
So what is in the fibers?
If this is not trade secret of professional builders.

"There is no place for opinions or belief in professional boatbuilders statement"
if this true, can somebody show me some test numbers, which say that marine plywood is better as Russian birch plywood.


Regards











'

[tkk]

Birch logs or fallen trees left alone in the forest rot in your eyes. If you are quiet you can hear the hiss as they rot away :D

This has most probably led to the believe that birch is no good.

I think one of the reasons is that the bark is so effective in keeping all the moisture in and thus promoting growth of all wood-eating organisms.

This guy suspects, that the high pressure and/or high temperature used in plywood manufacturing might change the sugar in birch. Anyway, his experience with birch plywood is very encouraging indeed:

http://koti.kapsi.fi/hvartial/white/white.htm

As you can see here, all plywood manufactured in Finland has been waterproof to the boiling test standard for a long time.

I live and work in Finland and for the forest cluster, although not for plywood producers. You may freely call me a nationalist if you want. :p

http://www.forestindustries.fi/Infokortit/handbookplywood/Documents/HandbookOfFinnishPlywood.pdf

APEX1: do you know which companies and wher e produces the plywood in Russia that you refer to?

I tend to agree the comment that the exporters/importers are the culprits. Probably they see no market for the higher quality stuff since there is the domestic production, whereas the lower priced interior quality might find some interest in cabinetry.

[apex1]

[QUOTE]
http://65.23.157.7/cgi-bin/woodsearch.cgi?comparing=166&comparing=142

Also I checked some information about rot resistance for birch , oukume and sapele


That is a very good and reliable database and commonly used by the industry too. It is hard (nearly impossible) to find reliable data on rot resistance. Even the wood explorer shows a too wide range of comments to rely on.
The Okume and Sapeli might not have been the best species to compete but I named them so you are right when you do´nt find a difference worth talking. But there are many species of shorea and other "Mahogany" substitutes used in EU marine ply to get good data any way. Same is valid for the birch ply, many species are used.

When I´m back at my office I´ll dig out the Russian supplier.

[alan white]

Yeah, I have some land in back and I often cut up fallen trees for firewood.
While most other species remain basically sound for up to a few years, birch lasts at most for a few months, if that, when in contact with the ground (and sometimes not even touching the ground).
This isn't scientific; the wood still has bark on it. Still, isn't bark like the fiberglass skin of a transom? Waterproof, like a birchbark canoe.
Maybe we should make boats from the birch bark instead.
I am wiling to accept that different subspecies of the same wood may have very different characteristics.
However, it seems to be the high-tech boys who espouse birch for boats, having read about the strength properties according to engineers, are seeing the more immediate attributes of the wood rather than IF the water gets in and IF it can sit there for a while. I know white oak, cedar, mahogany, yellow pine, and some others do not immediately turn black and mushy when this happens. But I fear birch could. I would only use it in a boat that didn't sit in the water all the time.

[petethai]

"This isn't scientific; the wood still has bark on it. Still, isn't bark like the fiberglass skin of a transom? Waterproof, like a birchbark canoe.
Maybe we should make boats from the birch bark instead."

No epoxy is not like a bark.
When we apply epoxy, we try to protect all surface of plywood (it should be!), even with bark the wood is still exposed to the oxygen, this is why we have rot. But birch bark is waterproof, this is true.
If we cut oxygen, there is not rot.
I am sorry if I am drifting this post in different direction, but in this world, where max.profit is a goal, we have what we have. We have optimum, that means, cheapest product with quality we can accept.
I understand that there is a some marine plywood, which is the best for marine application, but I think, most of plywood which we can buy (not just in US), it is a plywood, not better, or much better as birch plywood. And a lot of the later can be a junk as well.
The reason why I am writing this (in my poor English) is that I like forum like Boat Design Forum. It gives me a lot of information about boats. I am not going to fight with anybody, I just try to tell what I found about this subject. If we exchange our experience our boats will be better.
If we fight, we are not better as "PC contra Apple, digital contra analog..." etc. forums.
Better boat is not just faster, it is safe one.
regards

[apex1]

>>>>If we fight, we are not better as "PC contra Apple, digital contra analog..." etc. forums.<<<<<

There was no fighting here by now!

[tkk]

I think we were only exchanging opinions, yours to mine :p

Seriously, I think some good points have been expressed by different people.

[petethai]

I think we were only exchanging opinions, yours to mine :p

Seriously, I think some good points have been expressed by different people.

Yes, I agree.

And I didn't say it is fight here, I try to say, I hope this discussion will not end in fight.

Best regards