Plywood Questions

[J.E.D.]

I'm new here, so hello all!

 

Respectfully, yes, I know there is some info from Kudzu in the faq's thread. I do still have some questions regarding plywood choices.

 

First, I am a carpenter/cabinet maker who is very fond of canoing and camping. I've never actually paddled a kayak except once on those silly plastic sit-on-top ones. However, I've become very intrigued with kayaks. Also I am thorougly impressed by the construction of "fuselage frame" SOF boats. Plywood is a fantastic modern material with many uses and benefits. Lashing makes perfect sense too.

 

Now to the point: I see that most builders here are using Baltic Birch to make the frames. I'm very familiar with this material but as far as I'm aware, it does not have any water resistant properties. (please correct me?)

 

Also, Fir plywood seems to be popular in plans and pictures Even if you can get good Fir plywood, it is not only weak but the grain is VERY loose. It catches on everything now matter how much you round it and sand it.

 

I can get half inch marine plywoods, made of various hardwoods but they run about $125 to $150 per sheet.

 

So, I'm curious to know why builders on this forum use to plywoods they have chosen.

 

Jered -I've got a boat building itch that must be scratched-

[Kudzu]

I think the answer is largely "Because that is all we can find" and some would tag on "at a reasonable price'.

 

At least this is the case for me. Marine plywood, REAL marine plywood has be shipped in and I am looking at $100 shipping for 5-6 sheets.  Or driving 300+ miles. While $150 is a lot for a sheet, if  you look at the total cost of the boat it's still a bargain. I just can't find it or I would probably use it.

 

The alleged Douglas Fir marine plywood I can get is A+ garbage. I refuse to sell it.

 

Baltic birch is the best I can find and while it won't pass a boiling test (but who boils their boat?) it is very water resistant. I have left it outside, floating in water, used it on a lot of boats and so far, not a single failure or delamination yet. What your getting may not be the same grade as what I am getting but I have been totally impressed with BB.

 

Now, if something else comes along I am willing to try it. But at the moment this is the only thing I can find I will sell to my clients. Others will reply, but the number one problem most people have is finding a suitable plywood.

[P Doug (WA)]

Hello Jered and welcome.  On the plywood I used BB because that is what was recommended and easy for me to get at around $38 a 5 X 5 sheet.  Keep in mind none of us leave our boats in the water.  Use them then take them home, clean them up and let them dry out. And, we coat the plywood during the building process with something that helps protect it.  

[J.E.D.]

Well, thanks for answering so promptly guys. As usual, it's a matter of common sense.

 

As a further note. My sheetstock supplier notes that the Baltic Birch 5 x 5 sheets are laminated with Urea glue which is "water resistant". Most interior plys are made with Urea though, so that doesn't say much. It would explain though why it does seem to hold up to being wet. "BB" is definitely a fantastic structural plywood.

 

As far as a wood preservative goes, I prefer not to use a "shell" material. I've heard about mixing equal parts Pine Tar, Linseed Oil, and Terps. Apparantley it's what the old timers used on their boats. Any thought's on this?

[mitchmellow]

I have to admit that I get a little lost in the plywood discussions.  However, I've looked at Baltic birch from a midwest big box store and the specs say "exterior phenolic" for the glue.  Here's a link:

 

http://www.menards.com/main/building-materials/panel-products/plywood/1-2-x-4-x-8-baltic-birch-plywood/p-1479673-c-5698.htm

 

Open the specs pdf file on the first page.

[J.E.D.]

I have to admit that I get a little lost in the plywood discussions.  However, I've looked at Baltic birch from a midwest big box store and the specs say "exterior phenolic" for the glue...

 

That looks like a good product mithmellow. I'll have to do further research to see if I can get that plywood here. My origional though was that birch does not have any resistance to rot. Typically marine plys like Fir, Occume, Sappel, Mahogany all have verying degrees of rot resistance. As it has been pointed out, these kayak frames don't see prolonged wetting so rot isn't really issue. At least this Baltic Birch has an exterior glue which would prevent delamination when wet.

 

...Baltic birch is the best I can find and while it won't pass a boiling test (but who boils their boat?) it is very water resistant. I have left it outside, floating in water, used it on a lot of boats and so far, not a single failure or delamination yet. What your getting may not be the same grade as what I am getting but I have been totally impressed with BB...

 

Maybe I'll just experiment like Kudzu and soak some plywoods in water for a long time, get rough with them and see what happens.

[woodman]

I have had a pc. of 1/2'' BB outside for a few years nailed to a fence post and it hasn't delaminated yet....

[Bcone1381]

This thread from a few months ago that helped me gain knowledge on plywood.

http://messing-about.com/forums/topic/8412-plywood/

[J.E.D.]

This thread from a few months ago that helped me gain knowledge on plywood.http://messing-about.com/forums/topic/8412-plywood/

I'll have to make sure I do  more thorough search of previous threads before I start a new one. Lots of information there. ThanksBcone1381 and everyone else for their input.

 

Jered