I’ve got 3 freedoms and a cab all getting rebuilt. Some boards are getting more internal structure than others based on what i have at hand.
Problems - All 4 boards have soft boxes - no visible damage but none are stiff enough for prone foiling anymore. No other damage, no delam, no dings, etc. Just soft boxes.
The plan is to bond chinook boxes to a divinycell foam structure long enough to get the power from the front foot to the boxes. This internal structure is going to be fully wrapped with carbon before being set in the board, to ensure stiffness, then bonded into the board, then have carbon reinforcement to the bottom.
Weight isn’t a priority - stiffness is the focus.
Looking at what’s in the board right now there’s varying degrees of the same thing. A 1in thick piece of divinycell foam that the boxes are set in, extending a few inches forward of the boxes. My feeling is this is woefully inadequate. I think the high density foam should extend forward to the front foot area and for longevity there should be internal carbon laminations.
Today I prepared the boards, set up a jig to route out the boards for reinforcement. Special attention was paid to keep the hole flat (tricky with the bottoms of the board not being flat). Routing out the boxes didn’t really work, router was not happy with the plastic so I ended up using the sawzall and a lot of leverage to get the boxes out first before the router.
Next step is fitting the boxes and foam to match the holes and shaped to the boards bottom contours.
Would make sense to link the bottom reinforcement to the deck lamination with HD foam if you want something bullet proof. The EPS foam will for sure fail if it supports the full load of the foil in compression, although you might be on the safe side with the surface area of the reinforcement you plan to set in.
Cant see why you want to wrap your new boxes with carbon before being installed? Doesnt really add anything but weight. You should rather try to connect bottom and deck using high dense foam for example. Or laminate your holes as they are now using vacuum and then glue in your new laminated box-construction.
i’d rely on a deck to bottom connection for building something new from scratch, but for a repair involving the deck in the repair almost doubles the work involved(stripping traction and clearing adhesive is a pain, involving an exrta lamination, extra fairing, etc)
i’d agree that the EPS wouldn’t be enough to support if it was just the boxe area floating in the back of the board (like the boards were stock). By bonding the boxes into an internal structure the EPS is able to support the loads over the full length and on the sides. 10 inches of EPS at 1 inch deep(stock) cannot support those foil boxes but 24 inches at 2.5 deep makes for an incredible amount of surface area that has to fail simultaneously.
As for laminating the internal structure your firmly tying the boxes into a stringer, preventing their movement relative to the stringer and making that stringer super strong and stiff.
I fully expect to harvest the internal structure out of these boards in a few years to re-use once dings have caused weight issues/delam.
I like this approach. Especially the modularity and recycling of the solid components.
Building up strength from the top of the mast to the front foot seems sensible, and just treating the rest of the board as surfboard.
Seems foil boards overuse carbon for the rest of the board when it could just be fibreglass as it doesn’t need to be at all as stiff, only the foot to mast part needs the carbon rigidity, and that could be internally rigid rather than external?
Over building the foil box, and then “regular building” the rest of the surfboard parts was an idea for my next downwind board, which doesn’t need carbon on the nose or tail.
I’d like to see a board with mostly fiberglass construction and carbon in the areas where strength and stiffness (around the box and under the feet) are critical. While carbon is much stronger than fiberglass, it’s not drastically lighter necessarily.
Inserts fit to the boards today. Doesn’t have to be perfect, filler is light. Next step wrap the inserts in carbon. I tried to ease the corners of the inserts to facilitate a nice carbon wrap vs a hard corner.
100% agree, I used this approach also with a carbon torsion box / stringer that picks up boxes and footstrap inserts, rest of board is relatively lightweight fairing. Without the carbon laminates on the internal parts the structure is much less stiff than the mast itself (by calculation) whereas I tailored the laminates to meet or exceed the mast stiffness.
Laminated the inserts today, the side in the board got wrapped most aggressively because the other side will get more carbon when the bottom of the board is laminated. Not the prettiest wrap, the bag was on the small size and I tried to batch bake em instead of doing them individually. No pics of the bagging because that shit is hard enough without trying to take pics.
Glued the laminated inserts into the boards today. I used 2 part expanding PU foam as an adhesive to put in the inserts. I did this because none of these parts are a perfect fit and there’s inevitably some gaps to fill. I’ve had big PU pours fail in the past but I think these are thin enough and I’m spreading the load over a huge area makes me a little more confident. They came out a little proud and one had a deck bulge - both from foam expansion. I thought enough foam would squeeze out around the sides that pressure inside wouldn’t be an issue. I think it’ll be fine though, nothing tragic. No pics of it actually happening because it’s a time sensitive sticky process.
Next step is to sand the board to prep for lamination, then laminate the bottom layer of carbon on over the repairs. This will have some additional Uni/reinforcements. After lamination there will be fairing and finally paint.
Nice work! When I cut out the box on my kalama I used a multi tool/saw against a flat side of a 6x6, made a clean wall. I didn’t go as far as connecting the front foot, but I did connect the box to the deck with some wood and some biax, I bet doing something similar to the front of your beam would stiffen it nicely. But I did a similar thing to that beam when a converted a boogie board. I cut it into thirds at the width of the box and wrapped the edges in biax and uni to create “C” beams running length wise.
Love it! Yeah i probably could have done a cleaner extraction but there’s no flat part on these damn freedom boards to pull an angle off of! Looking at that glorious perfect flat pane on the bottom of that Kalama is making me jealous!
Also, no gonna lie, working with this freedom trash i’ve been a little quick and dirty. If id be working from a KALAMA BARRACUDA JESUS FUCKING CHRIST ITS SO BEAUTIFUL…i would have REALLY taken my time like go for coffee first then a late night of texting then a nice dinner…maybe meet her parents…sorry, getting a little hot and bothered here.
I think for building an EPS board from scratch bulkheads like that might be the best solution - even better than the extreme stringer idea. Because of the need for ding protection the outside is always going to be extra reinforced and the bulkheads allow the foil box to tie into that outer structure and make it stiffer.
Side note, more boards should get cut into and posted so we can shame builders into doing better! (Or in the case of Kalama give credit where due)
Yeah it took me a while to build up the courage to cut into it. I made a track extension out of g10 to be sure.
Even though the bottom is flat I still made a higher platform that could be moved since I couldn’t reach the middle just using the bottom. You could do the same thing using shims wherever you need.
The bulkheads were just connecting the tracks to the deck, front middle and back. The one I added was to replicate that with the new box. If I were building one from scratch I’d do the same thing but with a full hd block, and also after shaping cut longitudinally at the sides of the box and put in the aforementioned carbon c beams from the box to the front foot. Forward of the front feet the foam would be simply glued back together without carbon inside.
Thank you. Love this post, a friend came to me with a similar situation on his amundson and defaulted to a similar approach. Was trying to decide if I should go all the way through or right up to the top sheet.
Vacuum 209g carbon over XPS and future 1-shots for 30". Use expanding foam to re-insert.
Question is the downward pull on the foil going to significant enough to warrant some sort of extra wrap? That would be a PIA.
So i feel like the long reinforcement(all the way to the front foot) lets me get away with not having direct contact to the top sheet. Getting an internal reinforcement PERFECT with both sheets is hard, much easier to float it in the foam and just align the bottom. I wrap the inside of the insert, making sure to also tie in the boxes (i give the outer edge of the boxes a little radius to help them tie the foil into the carbon better better), then give a bottom sheet over it all to tie it into the existing bottom.
Agree in sticking w/ top sheet. Current plan: Cut the rectangle like you flush cut a piece of foam. Sand it on top and bottom to account for cloth, vac the ibeam with the tracks. Use gorilla glue as the expanding foam while clamped to secure it in. Then give it a pretty layer on bottom to seal everything in…
Will try and post pics when and if…
