I'm not sold on the engineering principles of the brokite construction, but hey, if it works it works. An I beam needs a web to connect the outer layers, but the web doesn't contribute much apart from keeping the outer layers apart and preventing shear. A core does exactly the same thing, which is why you probably don't need the carbon web (stringer).phuqit wrote: ↑Fri Aug 10, 2018 11:12 pmThen, I've cut the board into 5 pieces, like brokites g5 (look it up on utube), and wrapped each of them on the sides with 5cm wide unidirectional carbon strips, that are almost long enough to reach the fins. This is supposed to form an I-beam which strengthens the construction.
My opinion is that slight concave or convex has little effect of the dynamic behaviour of the board, apart from stiffening it. Sure a significant concave will cause the edges to provide more lift than a flat board, but a high aspect fin does a much better job. Besides, the stiffness provided by the concave messes with the flex I try to get, so I prefer flat boards.phuqit wrote: ↑Fri Aug 10, 2018 11:12 pmPulled the board from vacuum earlier today, and boy it's awesome. Flex is pretty much the same as the original board (I didn't want it to be as stiff as the previous experiment I've done, it's really hard on your knees). Rocker is pretty much spot on. Original board had a convex bottom (why would they do that???), so I chose to do a flat bottom instead. Concave was considered, but I decided not to deviate from the original too much.
1. It sometimes helps to massage during infusion, using a foam roller. This promotes resin flow into all the fibres.phuqit wrote: ↑Fri Aug 10, 2018 11:12 pmThere are a few obvious issues though:
1. Bottom has few tiny dryspots (~1x5mm). My guess I should have turned the vacuum pump off as soon as it infused, but I kept it going for another 8 hours or so.
2. The rails are... missing. I wanted to use FG rails idea, but as I started laying it up, it became apparent I have no clue how to do it properly - glass doesn't really bend. I'll need to reiterate the process again.
3. No bottom or topsheet. Top is probably easiest covered by UV-stable epoxy, as it sticks nicely to the top once you remove the peel-ply, and it doesn't add much extra weight. I've ordered bottom nylon sheets from junksupply, but they managed to fsck something up with their shipping provider, so it ain't happening until mid next week. I don't expect this board to last.
shhh.. it's a secret
Sounds like it could work, if it doesn't collapse under vacuum. Do some test pieces.phuqit wrote: ↑Mon Aug 13, 2018 9:30 pmOne more question - would it make sense to make the rails using a square fiberglass rope as a filler? Glue it to the edge, make sure it's flush with the edge, and laminate with infusion. I'm thinking, something along the lines (pun intended) of 4x4mm that people use for fireplaces:
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