Hollow Carbon Board

General Discussion
1

Yes, I’d like to make one but first… I wished I had known about this site long ago!

I surfed 4-5 days a week in H.school/College then for the last 35 years have been out, on one of my two 70’'s boards (7’2". 7’8") 2-3 times every other year (usually in the fall, it’s the off season… I train/compete in triathlons the rest of the year).

This last fall I was surfing in Santa Cruz and was thinking what would I do if anything happened to my boards? that led to thinking… I wonder if I could build my own? Next thing I know I have Shaping 101, Glassing 101, a Clark blank and finallized plans of shaping and glassing a 9’6" nose rider with Harbor Nose Rails. The only thing is I only read about the Nose Rail, hadn’t seen them, so my rendition looks more like hydrofoils. Oh, did I mention I can’t follow one plan, I incorporate two or three and always need to do a little experimenting? I glassed it with epoxy, one layer, top and bottom with 6oz. S Glass and a 5oz 3/4 deck patch of carbon fiber.

I was a bit apprehensive taking it out for the first time… what if it didn’t work like I planed? I finally got up the gumption and out I went. Monterey beach break, 3-4’ waves, no wind chop, decient for beach break around here and no one around. I put the board in the water… well it floats! I hopped on, found the balance point and began paddling… WOW it moves nice! That was it… All it took was that first wave! THIS IS THE BEST MOVING BOARD I HAVE EVERY BEEN ON! I’m not only HOOKED back to surfing but I think every fall I’ll HAVE to make another board…more experimenting!

Well, I liked the board SOOOO much that I figured my daughter or a friend would want to use my board and I couldn’t have that so I’d have to make another one. I #2 before Thanksgiving. Soon as it was dry enough out I went to compare…(the only difference, I thought, was #2’s nose was concave to slow it down) It WASN’T THE SAME!!! :frowning: It rode like my very first board (1965) 10’ Hobie nose rider, ie… long slow turns, VERY stable. I went home took out the tape measure and checked EVERYTHING! Now I think I know how to reproduce #1, be MORE exact in every measurement, ie…check every 6".

So now fall is getting closer, Ive been thinking of more ways to experiment, reading all the info here about EPS, XPS, carbon fiber, Paul Jensen’s boards (friend from longtime ago), light weight boards, stiffness, etc. AND…

the plan is:

9-10’ XPS foam, shape then cut two hyperbolic (?) curves trisecting the length of the board for carbon fiber ‘I’ beam stringers coming together about 14" from the tail to encompase the fin box, with two layers of 5oz carbon fiber top and bottom. Drill a hole in the deck, pour acetone in to desolve the foam, patch the hole, go surf!

I have a few more months before I begin so please post your thoughts, insights, knowledge and help… BUT don’t tell me it won’t work!

Thanks, Les

2

Sounds good. I must admit though, you lost me on the hyperbolic trisecting the length of the board I-Beam stringer idea. Would these be all the way through the blank? I think I might carve several grooves in the deck foam (not all the way through) and fill with carbon strands and epoxy before final lamination layers. This would leave partial stringer-like “ribs” inside that would help support your weight. Carbon is strong stuff but 2 layers of 5 oz might “oilcan” under your feet.

3

Lets see, Les - I think I’m following you, though I have a few thoughts on the subject - serves me right for dozing off in front of the tube and waking up in the middle of the night…

First off, putting the acetone to the styrene foam ( plain styrene might be a better choice, by the way, though still… ) is gonna be a leetle problematic: my experience with inadvertently dissolved styrene foam is it doesn’t dissolve so much as turn into a kind of marshmallow fluff kind of glop which is gonna be no fun to remove. It has the consistency of used chewing gum, in my experience. You’ll use a helluva lot of solvent and still not get it all. And what’s left will undoubtedly be in corners and crevices and the oddly placed weight won’t be especially good for the balance of the thing. As an experiment, take a glass mayonnaise jar, put a block of styrene foam in it that fits tight, pour in some acetone through a small hole in the screw-on top and see what happens.

‘Parabolic’ might be closer to the curve you’re describing, or simply ‘fair’: a smooth curve that runs, say, halfway between the rails and the centerline at the midpoint?

Anywho - let’s tackle this idea piecewise. For starters; carbon fiber, being kinda dark, might not be the best choice for the outer skin. Plus something with a skin that’s just laminate, no foam or intermediate material, well, it’s gonna be a bit flexy, y’know? Take and make up a double lamination of 10 oz glass cloth ( to approximate the stiffness of lighter carbon fiber) and set it on top of a couple sticks of wood, step on it and you’ll see what I mean. It bends quite nicely. While you might be willing to accept this on the deck, you want to bear in mind that on the bottom you’re gonna get a lot of concavities that you don’t want.

How to deal with that? Well, if you go with a thin sandwich construction for the skins, say fiberglass cloth plus a light colored pigment for the outer skin, a quarter inch sheet of relatively dense foam, then your carbon fiber on the inside, you’ll have something there that’s gonna do what you want it to do with minimum weight and maximum stiffness. Same for the stringers.

As I noted above, getting the foam that you’re using to form the critter out isn’t going to be a barrel of laughs once it’s all together. So, there’s a few approaches you can take. The first and well proven move is to do like Paul does, make up a framework and apply your skins to it - lots of details here if you give a quick search. What he’s done with wood you can adapt to thin foam plus laminate - in fact, Paul is doing just that now, see his The experiment continues thread . Though I should note that it takes a high degree of skill and ingenuity to accomplish which Paul is rather modest about.

Another option might be to shape a blank undersize, vaccum bag or otherwise form your laminate skin sandwich to it ( top and bottom halves), take 'em off and then shape and attach stiffeners, framing or reinforcements to the undersides, then glass it together. Whittle your reinforcements from foam, then laminate them to the underside to tie it in and stiffen 'em up.

Anyhow, that’s a few thoughts on the subject, hope they’re of use

doc…

4

There have been many many attempts at hollow surfboards.

In part, the success of the polyurethane blank has been its imperviousness to changes in temperature, and poor absorption of water in dings.

Hollow boards have problems with temperature changes. Gordon Clark goes through this in much detail in his little pamphlet. The cold water/hot board problem is solved only by a non-porous blank and non-porous skin. Otherwise you need a vent plug, and you need to remove the plug several times after paddling out, etc. Better to just use a core that works like polyurethane.

Dissolving polystyrene foam with acetone is going to be a horrendous mess - do it at someone else’s place.

5

Thanks to each of you for your help!

John - carbon stringers would attach to deck through board to same spot on bottom. I thought of T beams attached top/inside and bottom/inside to help stiffen the deck. “oilcan”, I made a carbon bike box of 2x10oz that is 2’x2’ and tried standing on it. The deflection is about 1/2 to 3/8". The most distance between stringers would be 7". The 5oz cloth I think would be to thin also.

Doc - I tried a 1" square piece of XPS before my first post, it desolved fine, leaving just a little goo. Today I pushed a 3"x5" piece into a can and poured Acetone over… YES! there is a lot more GOO than I thought there would be. A 9’ board would mean way too much and no idea where all that stuff would end up, tail, nose, left side?

Parabolic, ya, I think that’s it.

Sandwich construction… that would be like the paddle boards my dad made in the 50’s or modern like what Paul is doing. Paul, I think, is MUCH more of a maticulus craftsman than I am.

Carbon/Heat/Warping

The boards I made have 3/4 deck of carbon. My daughter and her boyfriend used the boards a few weeks ago and left them in the sun deck down in the sand! I hate sand in my wax! So, set them in the sun, just for a little while…well… it ended up being 4 hours! The first board (twill weave carbon) had 2" to 3" ‘bubbles’(delams?). The second made board (plain weave, maybe better glassing?) had no bubbles. The front part of the boards now have 1 or 2 very small ‘heel’ dimples (single layer 6oz. S glass) and the S glass/carbon areas are perfect. The bubbles went away after a few hour in the shade (sucked back in?)

So… still thinking of a hollow board but maybe my next one I’ll try EPS and carbon, I’m stuck on the strength/weight of carbon. Just have to keep it out of the sun unless it’s in the water.

Les

6

I dont know jack about building surfboards. but, i do know a tad about composites. I am a marine in school to be a crew chief on a ch-46 helicopter. I started surfing a little while ago and i came across this post and it grabbed my attention. On 46 our rotor blades are made up of a fiberglass shell over a honeycomb material. i remember from mechschool how this shit would flp and flop but when you stood on it, it could support un-holy amounts of weight. Have you thought about you this, in combination with your stringers, to provide the strength and hollowness you seek? as far as you delam. just think, carbon is black it absorbs the heat at a much higher rate. When I was in high school I used carbon to build a robot, I remember that you could buy different resins for different temperatures and different flexes. check out the attachment allong with this link.

www.advcomposites.com.au

7

Honeycomb boards were around at one point. According to Gordon Clark’s brochure, they were the most colossal business and engineering flop in surfboard history. Bad delam problem.

If you haven’t read the brochure yet, an old version is in the book Essential Surfing. It details a lot of things that DIDN’T work in surf design history, explains why surfboard cores and skins are non-porous, the difficulties with hollow boards, why small dings are tolerated in design but big delams are not, and so on.

There’s a cool story of the problems Tom Blake had with hollow boards when they were state of the art, the honeycomb boards, etc.

8

Checked out a couple of the new carbon fiber longboards that I saw in last month’s Longboard Magazine. I can’t remember the brand name. There was an ad and the brand was featured in their Buyer’s guide…

I’m pretty sure they’re hollow. At least they felt (and sounded) hollow to me. The ones I saw appeared to be carbon bottom and carbon/kevlar(?) hybrid on top. There was a fairly obvious paint job covering the seam between deck and bottom. I could squeeze the board and feel the top and bottom flex (oilcan).

Pretty sure that if you punctured one, it would fill with water. Maybe better to just leave the EPS foam in place? It doesn’t weigh very much.

9

Hydro Epic

http://www.hydroepic.com/technology.html

They are hollow and light and strong, with a vent plug. The inside can fill with water, but it is non-porous, so you can dry it out easily - you remove the vent plug and empty it. It patches with epoxy.

They have some top pros doing beta testing of newer models now.

Still, I’d bet you need to paddle out, and then open the vent plug and let it equilibrate, and then surf.

They’re based in the East Bay. One of their reps test-rode the rotating fin system. Thought it was really cool, but the board wasn’t the right size for him…

10

Yes, that is the company. They had a couple of the longboards at the Beach House in S.B. Thanks for the back up.