I've got a JP "single thruster" board to repair.
It's got a crack 2/3 across the bottom through the rail and ends just short of the front foot pad.
The board still feels solid, but I didn't want to exert too much force in case I increased the damage.
I started sanding away the damaged area on the bottom with a small right angle grinder, expecting to right through the sandwich.
But to my surprise the crack disappeared after only about 1mm of sandwich foam removal.
There's no way I can imagine ordinary PVC doing this, a crack this bad would normally go right through the sandwich, normal PVC foam is brittle.
I've used airex on a few boards in the past and it's very tough and pliable, you can bend it round the tightest rail without preheating or tapping the edge.
www.3accorematerials.com/en/markets-and-products/airex-foam/airex-r82-resistant-dielectric-foam
So is this airex foam, and it's absorbed whatever force has cracked the fibers?
If so I'll be confident I don't have to dig any deeper to do a good repair.
So anybody out there got any clues???
I have never seen a crack into the sandwich layer be only partial thickness. even with Corecell that has exceptional elongation at break (better than PVC so I use it if able) and even if that breaks it's complete. very strange happenings
when do we see your new board?
Maybe I'll dig down a bit and see what the underneath fiber looks like just to be sure.
But there's no crease, and there's no give around the crack, which you would expect if the sandwich has failed completely.
I suspect that Airex is better than corecell, you can tie a narrow slice in knots without it breaking
I'll try and get some pics later
The "flexible" airex is brownish R63 linear pvc, it's tough easier to work but cost a lot more than airex (herex) C70 cross link pvc. For custom sailboard in Europe, most used 5mm c70 for bottom and 3mm R82 for top and rails in 80 to 100 kg/m3 range.
Yesterday, I cut a slice across where the crack had been, and it came out in 1 piece. The crack only penetrated the foam about 20% of the way through.
This is incredibly surprising to say the least!
I think it isn't Airex R82 wich is more brown, look like corecell yellow color ?
That looks pretty much like my Airex.
Brilliant stuff.
When I was real flush I built my complete boards from it.
Now I only use it for the front 300mm and back 300mm, the sections which are most difficult to build/shape etc. Corecell for the remainder.
the colour is deceptive, it's covered in sanding dust so it's much more grey.
There seems to be two layers, the underneath layer is brighter and a bit more orange, (could be corecell)
So you need to look at that small spot on the side, that isn't covered by dust.
If it's not airex, it's equally tough!
That crack went 3/4 of the way across the board, to only go into the foam a mm is amazing
