View Full Version : balsa or marine plywood ??????

11-15-2005, 06:14 PM
What would be better for a floor 5 foot x 3 foot, 3/4 balsa or marine plywood ?????? The balsa is Coated, Contourable, Endgrain Balsa Wood for use in marine and boatbuilding applications. Coated with a thin resin film to enhance bond with epoxy from Jamestown Distributors.

mike farmer
11-15-2005, 07:30 PM
the plywood

Ted Stryker
11-15-2005, 08:09 PM
I'm a big fan of Balsa coring, but the plywood will probably hold fasteners better IF you can't nut/washer the back of em'... The plywood is sure to be an easier installation...

FX10 Superboats
11-16-2005, 04:30 AM
Go with the plywood. I wouldn't use Balsa core on a floor, where fasteners have to go into it. Save some money and go with CDX plywood at home depot. It's exterior grade. Put a layer of 1 1/2oz. mat on the underside prior to installation.


glassing oldie
11-21-2005, 04:15 AM
What would be better for a floor 5 foot x 3 foot, 3/4 balsa or marine plywood ?????? The balsa is Coated, Contourable, Endgrain Balsa Wood for use in marine and boatbuilding applications. Coated with a thin resin film to enhance bond with epoxy from Jamestown Distributors.

Plywood is the better chose but it needs to be 5 ply not 3 ply . Seal with epoxy resin it once you have cut and shaped it completel . The resin will only penetrate to the first glue line on any side just make sure it is completely sealed .
Water soaking into the ply will eventually make it heavy and rot never sleeps .
Ply will hold screws and the like much better than Balsa . 5 ply will stay straight and not want to bend and twist out of shape before you get it fixed in the boat .
With a balsa panel you would need to insert ply where fittings are going to be screwed to the panel so ply it .

Fast Fred
11-21-2005, 06:08 AM
make a combo sheet, your guna glass it on boath sides anyway, insert 9ply
ware your guna bolt down, and Balsa every ware else. super strong super light :cool:

Tampa Cat
11-21-2005, 03:48 PM
Now that's an idea worth thinking about,thank's FastFred.

aaron bjerke
11-21-2005, 04:29 PM
The more plies the stronger. I used Baltic Birch ( hardwood ) that at a 1/2" thick has 7 or more plies. It also has no knots or chop filler. You can find it in 5'x5' sheets at home depot or at your local lumberyard.

12-08-2005, 05:46 AM
Use plywood. cd ply is good. Dont mess with end-grain balsa with inserts for fasteners. Your floor is only 5 foot by 3 foot, and balsa is quite heavy for a core material at around 130 kg / cubic metre. Sorry about the metric, but thats what we use in Australia. Get with the program America. Metric is far easier to work in... lol.
If you use balsa with inserts you weight saving will be minimal and will require more effort than using ply. And if you aren't experienced it may come out heavier than plywood!
Don't use epoxy to seal the plywood unless your boat is constructed in epoxy and you are going to laminate with epoxy. If you are using polyester or vinylester you should preseal the ply before laminating both sides with glass. Ask your supplier how to make the preseal mix.
There are good reasons why ply is used by many performance boat builders, and cost is just one of them. Good luck

12-08-2005, 06:11 AM
you DONT wanna use marine (treated)plywood cause it gets saturated with sealent from the factory and when fiberglassed it cant breath plus the weight is not good either (its heavier)cause of the treatment it gets.what will happen is it will try to breath the saturation out of it after it gets glassed witch will cause the fiberglass not to cure properly.regular plywood would be better (cdx)but douglas fur is the answer.at the warehouses they just call it fur.

12-08-2005, 06:17 AM
....like 1/2", and seal and glass both sides first. Like someone else said, get as many plys in 1/2" as you can find. :cool:

01-08-2006, 06:52 PM
rick on that 1/2 plywood would you use treated or non treated

01-08-2006, 10:26 PM
And if it's glassed properly, the treatment is wasted anyway. :cool:

01-09-2006, 11:14 AM
dont used teated unless its the special marine stuff. the resin dont adheire to the regular treated plywood. heat the plywood up to 100 degrees [drape a plastic tarp over the plywood on saw horses and put electric heater under]. this the resin 10% with styrene for ployseter[boat resin] of tolyene for epoxy. coat the end grain at least twice. then do as fast fred suggested.

if possible determine where fastners will go and put nut plates on the underside where possible.

01-09-2006, 02:33 PM
When I did mine I made panels to fit the floor. I made two because that way I could get them back out if I had to in this hull. Anyway, I used 3/8" and I think it was thinner than that really. It was cheap cdx 3 ply. I got it cut and tossed it in, it was weak but sure it was thinner than what I took out....and lighter;) So what I did was paint it with epoxy resin 3 times to get it full. Then I epoxied little supports/braces where I needed them to make it stronger, like little stringers. Laid glass on it too (more in traffic areas) and mounted the whole thing in the boat. Worked real nice, feels solid even though it is thin. I let the wood dry for a week or two in 90F heat/sun before I used it, yeah it was a hot job but the resin soaked into the wood very nicely. Originally I had that stuff to do seat bucks and thought I would try it for the floor instead of driving to store. What happened is only certain areas needed to be stronger I found, so I beefed it up more in those places like where it crossed a span or something mounted to it. One weak spot in the middle I doubled up, and with epoxy it is very stiff.

Treated- I don't think it is worth much unless you use it for a part, like a door that is not glassed/etc. If you glass it in the glass may not stick to it well, if water gets to it the glass will still delaminate from it just like normal wood, and it is very wet when you get it so you have to let dry it a lot while it warps.