So first off that bit of waffle that I always feel the need to do… I’ve mentioned before that I’ve made a hollow wood SUP then a hollow wood surfboard. My main surf SUP is waiting for me to tackle the leash point as I previously posted. I like to make! I make many things in varied forms and feel it’s reasonable to class myself as competent, not totally incompetent! (A jack of all, master of none?)
My latest pondering is around making another board.
I have had a stringer cut out of thick birch ply for years.
I have a plan to use the dreaded DIY store EPS (sorry!) as I have some free. ‘Real’ foam just isn’t a viable plan before anyone suggests it.
I have limited digital design skills to draw up a hollow wood board to print templates so feel that foam will give that freedom to shape.
My big question is around improving the deck dent resistance of the foam. I had thought at first that adding multiple layers of glass would be the way to go. I then remembered that I’ve been saving up some thin sections of balsa. I wondered if putting some panels down as a semi-full deck could work to spread the point loading. I then wondered if this could actually produce a stress riser at the front and back of the deck making it more likely to buckle or if the stringer would combat that.
I got to reading on compsand (composite sandwich?) and think(!) that they are all stringerless?
Compsand is “full-deck” veneer.
Patrtial deck veneer my cause “hinging” with low density/“low compressive strength” EPS.
Board buckling results from compressive failure.
Wood has good compressive strength.
Cork has good impact absorption (impact dispersal).
Cork sheet under wood veneer deck might work.
You will need a vent to prevent delam when internal gas of low density EPS expands in the heat.
Reported by a cork product manufacturer, “(Cork can be) compressed to 15% of their normal volume and then regain most or all of its size and shape slowly.”
I believe Greg Loehr used furniture thickness wood veneer. Check the Compsand WMD videos. They should say.
Do some testing with a piece the veneer over cork with FG over or FG over and under. I would think the combo of furniture veneer, cork and FG should be pretty tough.
Did a test piece of foam with cork and glass. Never have tried wood veneer.
I would bond cork directlty to the foam or do glass to foam with cork over the glass. Once that is bonded, I would bond the veneer to the cork.
Edit:
Now that I think about it, my test was bonding FG to a piece of foam first. Followed by bonding cork to FG (was a very tough combined skin). Next step was to laminate FG over the cork (test didn’t get that far — back burnered it for another project)…
I build in compsand and have also used veneer deck inlay on eps. If your blank has a stringer, I would think the risk of creating fracture zone would be greatly reduced if not eliminated. Of concern would be if the the thickness of the wood. I use 1/8” on comp boards with no stringer, but I do a full deck skin that is also bonded to the wooden rail structure. There is no stringer down the center. On regular eps with a stringer I often use a bamboo veneer that is paper backed. It lays flat enough that I don’t need to carve out any deck foam to get it flush, just feather the edges a bit. Have ridden the heck out of them. They have great dent resistance, not much heavier than a regular glass job, and look cool with a pin line around them.
Both of these are about 1/8” thick, glass under and over. The first pic is paulownia, the other is balsa. Zero problems. The white board is a few years old. The blue board is 10 years old, but I recently added the balsa because the deck was getting mashed.
I make boards with EPS and Balsa decks, been doing it for about 20 years. I use model airplane balsa so it is usually only 36" or 48" long. I cover the whole deck with either 1/16" or 1/8" thick Balsa. I often cut the pieces at 45 degree angles to keep from having a straight line across the board and sometimes I add a cloth inlay. There is no balsa under the cloth.
If the EPS is hard enough, like 1.5 PCF or 2.0 PCF, I just do 2 layers of 6 oz or 3 layers 4 oz glass on the deck.
Hi Huck, I don’t remember if I put glass under the balsa, but I probably did. I was glassing the deck with one layer then putting 1/16" balsa then glassing over the balsa for a while. This was from a slab blank that had a stringer, so it may not have glass under the balsa, just 1/8" balsa and then glass, but maybe 2 layers of 4oz glass. These boards don’t deck deck pressure dents. I made this for my brother 4 or 5 years ago. I did a couple like this with the cloth inlays. I got these thin hand towels while I was in Japan in 2017, so the board was made after 2017, probably around 2019. I did 3 like this. Here’s my 6-10.
I forgot… the balsa is vac bagged onto the board. For the stringerless boards I make, I laminate the board with one layer of glass then do the wood, then I glass over the wood. Quite often with the stringerless boards, I will do a second lam on the bottom after I install fin boxes. My boards don’t flex much, but I like them stiffer.
