Spine plywood

[bpalumbo159]

Is birch plywood ok to use for the spine , I have a full 4'x8' sheet at my house and it's been sitting here for awhile? Also does all or any of the wood have to be marine grade? Also the rails are they 11' or can they be pieced together, sorry if these sound dumb but I'm new to this and I'm trying to learn. Thanks guys

[juliangibraltar]

Not sure about birch...other than weight I don't see why there should be any issue as long as the thickness is about right.
Marine grade is simply the bonding glue in the ply that wont dissolve when wet. In an excellent build you would not get water inside so there should be no problem but in a build where you place an air valve (to allow for hot/cold air expansion) and you might forget to close it and water gets in then you might have more of a problem if its not marine grade.

What I've done is fill the inside with foam so there is no air inside, therefore no valve needed (or forgotten!)....so, on the basis my glue, resin and fibreglass is waterproof there should be no water getting in. Having said that I still chose Marine grade as the price was good.

Re the rails, they should really be 11' (or longer for the curve). They take a lot of stress and twist and chances are if you pre-glue them they wont take the strain...theres a lot of steaming or soaking done at this point to curve them. I suppose you might be able to place them in shorter lengths but again because of the curves you probably wont get a good end to end join and this will become a weak point......I would get the full length ones.

[bpalumbo159]

Julian thank you for the insite that helps a lot! I figured I'd ask because I've heard people say they've used fence pickets. I am planning on using 12fters anyway but thank you very much

[kevvisser]

Hey guys

juliangibraltar what foam did you use and at what stage/how did you put it in ?

Thanks Kev

[jensen1031]

Kev,

Good luck with your build. I did the foam simialr to Julian. Take a look at the "NJ Sup" build thread. I have posted a lot of photos. One word of caution......it will add a lot of weight to the board. Im willing to take that gamble as im a buigger guy.

I added the foam once the bottom and the rails were glued. The only remaining thing I had to do was add the top and then start shaving. Some people on the threads said that you can get half of the top on and then reach under to spray the foam. I may try that next time.

I used "Great Stuff Big Gap" filler. It has a higher expansion than the normal stuff. If you are looking on the shelf, it has the black label, vs. the red label. I probably used 8 XL bottles or so. Probably could have used less since I had to shave a ton off.

Good luck.

[kevvisser]

Thanks Jensen

your pics and ideas on jigs look great, thanks.

[vilanobeachsurf]

Jul 29, 2014 21:10:58 GMT -5 bpalumbo159 said:

Is birch plywood ok to use for the spine , I have a full 4'x8' sheet at my house and it's been sitting here for awhile? Also does all or any of the wood have to be marine grade? Also the rails are they 11' or can they be pieced together, sorry if these sound dumb but I'm new to this and I'm trying to learn. Thanks guys

Greetings,

With regard to the use of non-marine plywood. I don't think that you will have a problem if you take the time to paint the inside of the board before you put the deck on. I used some old waterproof primer rattle can that I had laying around. I also always put my vent plug in a consistent, safe place! Next boards will use gortex vents!

I almost put foam inside, but was concerned about the weight...

Anyway, let us know which way you go!