I plan to build a small wave shortboard (5’10 x 20.5") using a 1.5 pcf marko eps blank w/ a carbon fiber bottom and bamboo (possibly another type of wood) deck. Never worked w/ CF but think it looks great. I’d like to share my plan and see what comments suggestions you guys have regarding working w/ the CF.
I’d like to cut out the bamboo for the deck and trace the template onto the shaped blank. Tape off inside the traced template so I can cutlap the CF. Lam the bottom w/ CF doing a cutlap. Vac the bamboo to the deck. Auto pin tape the seam. Lam the bottom w/ 6oz E glass, wrapping over the CF/Bamboo seam by an inch and a half or so (cutlap). Lam deck w/ 6 oz, hotcoat both sides and sand.
Would I be better off from a finished product perspective if I vac’d the CF on the bottom? How complicated would that be? Can you vac the CF until its at the right stage to cut the laps, pull it out of the bag and cut the laps and throw it back in the bag?
I like the idea of cutlapping the CF b/c I want to create a nice, clean inset for the bamboo… am I smoking crack for thinking I’ll be able to get it that clean? Is cutlapping CF a bitch? Should I just freelap the CF and bag the wood over the laps?
A few thoughts. CF can be cut lapped, but it is hard to do. Been a while, but I think I used a cut lap tool with a razor built in. I you may be able to see the tape with a flash lite underneath, but not sure. I wouldn’t try to time the vac bag to cut lap. That is a roll of the dice. A bamboo covering over the rail line will look good and as Pompano says is a good suggestion. But don’t do the whole bottom CF and bamboo. Way over built. CF looks cool, but I’m not sure it is worth the effort. Too hot in the summer (literally burns the hand) , dings will shatter and are hard to fix, with CF on the rails your board will not flex under any load you can apply no matter what, it’s expensive, and hard to work with.
But do experiment. And let us know how it goes. Post pictures. thx
I appreciate the suggestions shared to date and would be jazzed to hear from John, Mike Daniel and GL. I know those guys have been there, done that and worn out the t shirt they got there. I woke up at 3am wondering about the possibilities… I think maybe Greg Tate nailed it: too stiff. I don’t want a board that looks great but that’s going to ride like shit.
As a backyard experiment with materials and bagging, I played around with a scrap of 2lb EPS and made a bellyboard.
I hand laminated a carbon bottom with generous freelaps that were feathered out before a bamboo/carbon composite skin was vacuumed to the deck. A wide 'pinline' was masked off along the edge of the bamboo and a little pigmented epoxy bog was used to reduce the step before a layer of clear fiberglass was hand laminated over the bamboo.
The carbon/bamboo composite deck skin was prefabbed topside down on a flat vacuum table. I used a pair of scissors to trim to fit - like Greg Loehr's Timberflex method
Cutting carbon is easy enough - a razor blade cuts right through (like with fiberglass) when it's at that stage where it's not so soft as to be too sticky but not so hard as to be a pain. The tricky part is finding your tapeline under the carbon. One way out is to build up several layers of tape along the cutline so you can see the bump under the carbon and cut along that. Some weaves might be easier to see though than others. In fact you might take steps to avoid any 'see through' of the white foam under the carbon. I sprayed my blank black where I thought that might occur.
I think you will get a smoother transition if you inlay your bamboo deck inside the carbon cutline. I will try that next time. It's a trade off between having the potential shear line of an edge to edge transition VS overlapping the skin over the freelap which eliminates the shearline but leaves a bit of a step.
Until you have some experience with vacuuming, carbon might be an expensive experiment. Getting a wrinkle-free rail wrap under a vacuum bag might be tougher than it sounds. The bag tends to wrinkle and those wrinkles distort the carbon which is visible. If you figure it out, Please let me know how you did it.
With 6 oz carbon bottom and a staggered 9 oz carbon/bamboo/4 oz fiberglass the deck is fairly durable and very stiff. The portions of the deck that are the full combination are impossible for me to pressure dent with my thumb or even a good hard knock with my fist. The single 6 oz carbon bottom is stronger than most shortboards but I can dent it if I push pretty hard. The cool thing is that as the board heats up in the sun, the dents disappear.
My experience with stiff boards is that with enough tail rocker, belly/roll, and a flexy fin, stiffness is not that big of a deal.
Oh yeah... I've had issues with ghostly white areas when I frothed the resin as I glassed clear over carbon.
We did hand-lam carbon over 1 lb stringered blanks back in the late 80s. E-glass over the 5 oz carbon, I painted mine white to prevent explosion. I still have one of the boards. Carbon sandwich glass-on fins too. Dave "Davo'' Dedrick was the ace carbon hand-lam guy back then.
Carbon in surfboards needs another fiber in an additional layer (or hybrid weave). By itself in single layers it has little toughness. Plus you don't want to sand into it. Carbon on the rails makes no sense at all to me, putting the most brittle material in the most vulnerable position.
If you live somewhere where you can get away without painting it, it will look cool. I don't think it's functionally the best way to build a board, but if you want to do it, I'd say freelap it to avoid the stress riser of butting to bamboo. At least on the bottom it'll be on the tension side, on the deck carbon is such an effective stiffener it'll lock the whole structure into deadness (if you put enough of it to not dent easily).
The board I still have is a 6'2'' x 20'' x 2.25'', flat deck and boxy rails. It weighed 5lbs, 2 oz when fresh. I made a 9'0''hplb that weighed 10 even. Unfortunately they all broke (explosively!) because compression loads on deck skin (bending compression, not point load) blow up carbon. If you did multiple layers on deckside it would be stronger, but then see above.
Carbon is at it's best in multi layer applications where building laminate thickness by taking advantage of it's low specific gravity is an advantage, and very stiff parts are desired. Or where fiber orientation can be engineered to take specific loads.
@Kirk - That's the direction I'm heading. I want to make a Timberflex (and possibly carbon-bottomed) SUP in the spring. I'll let you know when I get it down.
"I’d like to cut out the bamboo for the deck and trace the template onto
the shaped blank. Tape off inside the traced template so I can cutlap
the CF. Lam the bottom w/ CF doing a cutlap. Vac the bamboo to the deck.
Auto pin tape the seam. Lam the bottom w/ 6oz E glass, wrapping over
the CF/Bamboo seam by an inch and a half or so (cutlap). Lam deck w/ 6
oz, hotcoat both sides and sand."6
With that build it’s gonna be really stiff. I’ve got a 5’10 and 6’0 with 1.5# stringerless EPS and they both have double 4 bottom, carbon rails, 2oz/bamboo/4oz decks. They are plenty strong and ride great. Light foot dents on both which tells me they aren’t overbuilt but still have a bit of give to them.
I think a full carbon bottom is overkill and will stiffen the board up too much. The bamboo is already pretty stiff stuff once glassed on both sides, so use that as your key structural component.
The boards ride really good though, so I think you’ll be happy with the construction if you don’t overbuild it.
Like MD said, the carbon on the rails is the worst place for it as far as durability, but it’s also the best place to take advantage of it’s characteristics especially on a stringerless board. Just make sure to cover it with some fiberglass to make life easier as far as sanding.
I’ve seen some of pompano’s boards and he seems to have a good grasp of how to apply carbon rails. Pick his brain on it
