Hi all, looking for experienced opinions on a ~50L 4’6” wing board vacuum build I’m trying to keep super light. I don’t want a box failure but I’d be fine with a board that dings easily if I drop it on a rock, though not from pressure dings from just standing on it.
Option 1 : Pretty light (too light??)
2oz s glass entire top
4oz carbon/innegra whole top and rails
1/8” 5lb divinicell standing area
2oz s glass standing area
1lb EPS CORE
3 x 4oz carbon innegra overlapping patches for foil box.
4oz carbon/innegra entire bottom and rails
2oz s glass entire bottom
Option 2: heaviest
Same as 1 but 1.5lb and no divinycell, just some patches over foot locations
Option 3: heavier
Same as 1 but divinycell entire top (and bottom?)
Option 4: lightest
Same as 1 but no 2oz S glass finish, just 4oz carbon innegra.
Other stuff:
1.5” thick HD foam track foil box
Tuttle box through track box going to upper skin
HD blocks under footstraps and leash plug.
I’d like to finish as light as possible. All the fast guys in SF with custom boards have a peel ply finish with no pad. I’m not sure how they seal from pinholes. I think if I glass the 2oz separately that should fill the pinholes from the lower layer, correct? Or do I need a micro bead/epoxy rub ove that as well? If I just finish with carbon/innegra (which can’t be sanded) can I just do a microballoon /epoxy rub on that to finish?
Anyone make a board so light you got pressure dings? Anyone make a 1lb eps board and do a 4+2 oz like #1? Any issues?
I haven’t used these exact laminates but have some thoughts:
I don’t think 1lbs eps density will get you a lot of weight savings, 0.5lbs/ft3 difference is 8kg/m3 or 8g/l, 400g is saved on a 50L board by using 1lb foam - but i don’t think it will be stiff enough without a thicker skin layer which adds back weight and cost. Therefore i think this foam option without divinycell is less than optimal.
With divinycell top and bottom it will probably work, adds about 2x170g in itself but also needs to be glued to the eps. The amount of epoxy under the divinycell has to be kept at a minimum to keep weight down - you might need a spackling/seal on the EPS so that it doesn’t suck epoxy. My latest vacuumed board was not spackled and had epoxy sucked down to 1” depth of the foam, killing weight savings. An option might be to use foaming PUR glue for the divinycell to EPS bonding (like Gorilla wood glue or sikabond 545). That will require good pressure to bond evenly.
Option4:
innegra doesn’t sand well so any surface laminate with carbon/innegra will have to be either left imperfect (unlikely to be acceptable and possible only on top) or you’d need a thicker epoxy layer to avoid sanding through it - which adds weight but not strength. It’s then better to cover with a 2oz s-glass layer to facilitate both strength and a proper sanding.
Before vacuuming the actual board it’s wise to do a test with a piece of your planned sandwich layering to test how high vacuum the foam can take before it starts to crumble, especially with 1lb foam. My last board lost about 5% volume at full vacuum (d’oh!) causing ridges and wrinkles. It then needed a lot of spackling after the vacuum bagging which inevitably added unnecessary weight. I guess something like 0.2 atm of vacuum will probably work but not 0.9 (which i used).
You don’t need to worry about pinholes, vacuum plus peel ply leaves a uniform surface if done correctly.
Around the foil box i would replace all or at least two layers of carbon/innegra with 100% carbon to maximize stiffness. I don’t think the added toughness from the innegra is a focus in this area.