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Old    Akadirtbikingdad (wakeboardingdad)      Join Date: Aug 2008       07-23-2010, 5:56 AM Reply   
Man, I thought I had found my foam connection, but now that I get down to the exacts, they only have 1# foam. Won't it be too brittle and porous?

Last edited by wakeboardingdad; 07-23-2010 at 5:59 AM.
Old    Shane Miller (hematoma)      Join Date: Jul 2008       07-23-2010, 6:01 PM Reply   
Quote:
Originally Posted by wakeboardingdad View Post
Man, I thought I had found my foam connection, but now that I get down to the exacts, they only have 1# foam. Won't it be too brittle and porous?
Go to Home depot or Lowes and get some exterior foam board, the kind with the reflective crap on it. They are using it to build boards. It's 1'' thick so you have to laminate 3 of them together. that will give you plenty to mow down to your final thickness. Check out swaylocks forum their's a guy that only shapes them using this stuff. He's got pics of his builds to look at. Once they are finished you can't even tell its not a surfboard blank.
Old    Jeff Walker (surfdad)      Join Date: Sep 2004       07-26-2010, 8:21 PM Reply   
I've worked extensively with 1# EPS, but mostly only in a sandwich build. The last one I doumented here on WW can be found here.

1# EPS is mostly air...well air and pentane blowing agent trapped inside the beads. The EPS that wakeboardingdad references is typically recycled up to about 25% and has an average weight in the .75# pounds per cubic foot. It's normally a C grade bead (C = crappy ).

While it's possible to use it for a board without a high density skin, like I use, you have to design your board to be used with that stuff to really work. What you would be using the foam for, is strictly to hold your shape, it won't support you and without adequate skins and a stringer it will be super floppy - you'll go to pump it and it'll flex under foot and feel mushy.

The stiffness of a board is primarily determined by the distance between the exterior laminations. Design your board to be thicker to gain some stiffness. Stick a goodly width stringer down the middle and balance the fiberglass well. Fiberglass is stronger in tension than in compression and since your core will NOT be helpful is displacing the loads, use twice as much 'glass on the deck side as on the bottom...I'd suggest 4 x 6oz deck over 2 x 6oz bottom. Also, because it's mostly air and we ride in super hot weather, and you aren't sealing it with a sandwich, you can expect it to delaminate unless you vent it.

Lots of work, when 2# foam, eleminates all that nonsense.
Old    Akadirtbikingdad (wakeboardingdad)      Join Date: Aug 2008       07-29-2010, 6:55 AM Reply   
Thanks Surfdad! I know I had seen something along these lines before, but I have looked at so many posts, I wasn't sure which one of yours it was. I think I have a hook up on some foam board now, but I have to wait until they are ready to order. Meanwhile, summer is slipping away and this weekend, well, I am free! The local supplier I have found, already has 3" thick blocks, but that is a little thin. I'll prolly need to laminate two together to get the whole thickness, (unless I am willing to form it) but that leaves me with a perpendicular joint right near the tip. Not sure if I like that, but if I plan it right, it will only be the very tip on one board I have planned which is an upsized LF custom, but on the red woody copy, it'll be a good section at the front. I should just go ahead and do it, since these two boards are probably disposable anyway.
Old    Jeff Walker (surfdad)      Join Date: Sep 2004       07-29-2010, 7:38 AM Reply   
I'm all for just doing it, too. Post up your "blank" construction of you get a chance, I think that could be interesting for folks. That material is so plentiful, everyone could do it.
Old    Akadirtbikingdad (wakeboardingdad)      Join Date: Aug 2008       08-24-2010, 6:34 AM Reply   
Jeff, I simply got tired of trying to find the better foam and ended up with the 1# junk. I'm going to vent it, string it, glass it and hope for the best.

I have a question though. If fiberglass works better in tension, then wouldn't it be better to have the heavier lay up of glass on the bottom? It would seem that the deck is in compression and the bottom is in tension when the board is being ridden. No? Thanks. And yes, I will document my build for all to see.
Old    Jeff Walker (surfdad)      Join Date: Sep 2004       08-24-2010, 8:42 AM Reply   
Yeah I hear you on trying to source materials. You can also run multiple stringers - one down the middle and say out 6 inches from center which might give a cool look and would provide some additional support.

You've got the tension and compression components correct. The deck side is in compression and the bottom is in tension, when the board is being ridden. Typical layups are double top and single bottom. Because fiberglass is stronger in tension than compression (by a factor close to 2:1), the deck or compression side needs about twice as much fabric/reinforcement to match the tension or bottom side. Boards tend to break when the structure is unbalanced. If the bottom had twice the layup as the deck that design would actually be about 4 times stronger on the bottom than the deck, when ridden. In order to "balance" or equalize the strength, to avoid the tendency towards breakage, the deck side or compression side needs twice the reinforcement as the tension or bottom side of the board.

I'm not sure if I made that any clearer, I hope it helped!

Yes! Looking forward to the build thread!
Old    Akadirtbikingdad (wakeboardingdad)      Join Date: Aug 2008       08-24-2010, 9:28 AM Reply   
Duh! Yes Jeff, that did help. I was thinking "backwards". Stronger meaning: less is required. Duh again!

I probably need to graduate from the short bus before I continue with this build.....
Old    Jeff Walker (surfdad)      Join Date: Sep 2004       08-24-2010, 9:56 AM Reply   
LOL - no you're fine. When I do the compression/tension deal I always have to sort of "push down" on an imaginary board and think - ok THAT's compression so the OTHER side is tenson. "lefty loosy, righty tighty" I need a good saying like that for compression and tension.

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