Sorry for the slow update. Been a busy week, finally got around to some lamination.
So to recap, the boxes are laminated into a divinycell block going all the way to the front foot. Box is bonded in with pour foam, faired in with fairing compound. Sanded fair, time to laminate the bottom carbon.
Prep - sanding, acetone, blue tap. Tape is going to be outside of the laminate(carbon doesn’t overlap over tape). Pull the vent plug on the board - there’s air in there and the vacuum will pull it out, better going out through the plug instead through your laminate creating a pin-hole.
Carbon gets cut inside the tape(use a tape measurer to cut the laminate precisely) I do Uni under the biax carbon and another carbon patch in the back. Uni shouldn’t be exposed.
Peel ply needs to overlap tape (so carbon is 100% covered by peel ply) then the bleeder breather sits inside the peel ply. (bleeder with resin without peel ply = stuck on mess).
The whole thing goes in the bag, i like to have some bleeder around the vac tube just to facilitate the vacuum getting where it needs to go. I use the long tube bags and these clamps to hold it together. I have a pinhole in the bag thats marked and keeps the vacuum at a reasonable level - don’t want to be imploding the board.
I’m not a professional by any means, this is my system, happy to hear input from more experienced laminators.
Another freedom techno being rebuilt. This one is keeping its original boxes. I found the box removal and reinstall to be problematic and expensive so I’m leaving the original boxes, cutting off the inside box flange(for better stringer adhesion) and putting in a PVC foam and carbon stringer. As you can see in the pics the stock freedom internal reinforcement is non existent. Routed a track, dropping in PVC foam wrapped in carbon. Trim and sand flush, cap with carbon.
It doesn’t work very long. The tricky thing is the box Failures aren’t immediately visible. There’s no cracks or dealumination, just flex. I’ve had people report that their freedom board lost his stiffness And responsiveness on the very first session. Almost all production boards have that flex if you know what you’re looking for.
UPDATE Got a current model WCFC in for reinforcement. Let’s see if freedom has cleaned up their act at all.
Cutting into this one I’m seeing two extra bulkhead style pieces of foam reinforcement but they don’t go all the way to the deck, only 1/4” past the boxes really. Not sure why they even bothered. still no internal fiber reinforcement. Also, VOIDS where the boxes are glued in.
So extra effort for 0 performance plus a failure on the box lamination.
Having re-built or installed more than a dozen foil boxes over the years, and being a mechanical engineer, this design screams 100% failure. I can not believe a company goes into production with this design and sells the boards for $1,500 . . $2,000 . . $2,500++
The compressive forces on the leading edge of the tracks are many multiples of the riders weight. Think of a cantilevered hang man structure. This all sitting on top of ‘beer cooler foam’.
There is no amount of lamination you can apply to prevent cyclic failure from this design.
What do you think of this method of repair? I know replacing the boxes and attaching to the deck laminate would be stronger but it adds a TON of work. I feel like my tie-in to the existing tracks on the last few have been kind of creative, I’m wrapping that d-cell beam in carbon and where the laminate creeps around the D-cell at the boxes im wrapping it onto the top of the existing track box, trying to tie that laminate into the foil as much as possible.
I’m able to do this repair now with about $40 in materials and 3 hrs of work which I’m pretty happy with!
I am not sure after all the posts what the final repair is. I think it is this picture.
The challenge is that you have a lever arm extended out over the front of the mast plate. The effect is 2.5X the weight of the rider (see next post). So a 200 lbs rider will impart 500 lbs of force on the front edge of the mast plate. This amounts to ~ 200 psi (1/2" x 5" = 2.5 square inches holding 500 lbs of load). You should not be expecting anything without vertical load capability, deck-to-deck, to hold that load. AKA no beer cooler EPS foam in-between that compresses easily in a vacuum at less than 5 psi.
A quick update to your beam approach would be to use carbon arrow shafts. Most specifically under the front of the plate. Push them through until they hit the upper deck. Then gorilla glue them in place. 4 or 6 up front and 2 at the back would probably do it with the Divinycell beam approach.
Here is the math on the leverage applied to the front (compression) of the mast plate and the lift (tension) on the back of the mast plate.
This is a simple Free Body Diagram of the loads using a 100 kg rider and Axis standard fuselage dimensions.
Net result 260 Kilograms of force on the front of the mast plate, 575 lbs of force. Nothing on a surfboard compares to this where the riders weight is spread over a large portion of the bottom of the board. aka 21" wide board ~ 3 (36") feet of waterline = 756 sq inches. → 0.3 PSI on the bottom of the board.
Yeah, I’m not questioning the leverage and the force. My approach is about tying the boxes into a stiff carbon d cell beam and using that to move the forward loads to the foil. It’s about getting the energy from the front foot to the foil - the front foot being the only way to get that kind of leverage to generate the kind of loads your quoting. Being honest I don’t really care for that arrow approach. I feel like if it really did anything it would be applying inappropriate loads to the deck skins. So if the deck skins are fine then it’s not doing anything…or it’s killing the deck skins. Also, I wouldn’t touch gorilla glue or poly foam for anything structural.
