balsa core material

[flyingfrizzle]

Found a deal on a bundle (17 2x4) sheets of of 3/4 end grain balsa core material. Wouldn't go out and buy this normally but got it cheep enough it was hard to pass on. I got a few ideas where to use it but got to thinking about how it was used every where on the seacrafts originally and was thinking about re-coring the floor in my 23 with it. Was planning on using the fir marine ply but now that I got this why not. Well I was hoping some of yall guys could tell me if it would be fine or why not. My main concern is how long it would last vs the fir. I plan on glassing both sides fully not just resin coating it.

[FishStretcher]

I would expect it would be much better than the fir, pound for pound. The 1/2" end grain balsa in my 25 is still holding up well at 42 years old, except where holes were drilled into it and left open to the elements. Even at that, the grain is vertical, so water doesn't migrate far. I am continually surprised by the relative lack of water damage where holes were drilled. Plywood grain is lateral, so it would let the water travel along the panel quickly- I suspect delaminating and soaking up water more quickly. There is a little bit of genius in using end grain balsa.

[flyingfrizzle]

Originally Posted by FishStretcher

I would expect it would be much better than the fir, pound for pound. The 1/2" end grain balsa in my 25 is still holding up well at 42 years old, except where holes were drilled into it and left open to the elements. Even at that, the grain is vertical, so water doesn't migrate far. I am continually surprised by the relative lack of water damage where holes were drilled. Plywood grain is lateral, so it would let the water travel along the panel quickly- I suspect delaminating and soaking up water more quickly. There is a little bit of genius in using end grain balsa.

That was my thought due to the idea that balsa core centralizes the water to a cell vs spreading, also I thought the 2x4 sheets would work better than the ply due to hearing about large sheets warping. I haven't had this problem but heard that it happens and smaller sections will eliminate this. I will be harder to install the 2x4 sections vs a full 4x8 sheets with less seems but a little more effort and it wouldn't be that bad I think.

[Bushwacker]

FS is absolutely right about balsa core! I think it's better than plywood for deck cores provided you use some common sense and don't put unsealed holes in it!

I've read a number of yacht surveyor Dave Pascoe's excellent articles, and this one http://www.yachtsurvey.com/core_materials.htm indicates that he likes balsa core better than most core materials! I suspect Carl Moesly researched it quite thoroughly before he started using it, as he did with most anything involving boats! Water doesn't migrate quickly through it like plywood, it has better shear strength than most of the foam materials, you always know what you're getting with balsa core (unlike many foam materials), and resin bonds to it really well, which is not the case with most composite materials. It seems like they really require the use of cabosil or equivalent and maybe even vacuum bagging to be really confident about getting a good bond with fiberglass!

Every square inch of the balsa core in my 42 year old boat is just as solid as the day it was built, probably because the original owner, who only had it for 3 years, never drilled any holes in it! I've always used the drill-oversize-hole/backfill-with-epoxy-cabosil/redrill technique on any holes I put in it, so the stuff should last forever if it's properly sealed and maintained!