a different kind of sandwich

General Discussion
1

(first post)

Hi, I hope I don’t have too many regulars shaking their heads in shame, but I am shaping my first board and would appreciate any advice from heads more experienced than my own. If not, hey, at least I’ll probably leave you entertained thinking about my bold (idiotic, and not-thought-through) ambitions! 

More info makes a more detailed picture, but I’ll try to keep this as short as I can.

I’m shaping a prone/kneeling board for use in surf lifesaving. Basically, it’s a 10’6’’ board of width around 20’’ and thickness around 7’'. They are used for competitive racing (buzzwords: LIGHT and RIGID), however I would like to focus on breaking the laws of physics and attempting to build a board that can be competitive AND durable (most competition boards get damaged quickly the way we race them here in Ireland). As for shaping, I’m pretty much set, thanks to the hours I poured into studying swaylocks instead of my honest-to-god science degree :wink: . The basics are: (probably best read bottom to top)

  • THE HEART - 1lb EPS foam core (Yeah, it’s a** BIG** blank… will have to stick two 8’ blocks together (using a bit of PU pour foam and ratcheting them until they’re stuck)

  • THE RIBCAGE - single-layer 4oz Carbon Fibre//epoxy, deck & hull (I want a nice rigid core here, my thought process being: ‘‘punchy’’ through waves/chop, instead of the waves causing flex through the board and losing momentum - correct me if this is a waste of time)

  • THE FAT - 1/2’’ thickness (when cured/set) of 2lbPU pour foam (maybe even 4lbPU pour foam) all over the board, coating the entire thing… like Mr.Whippy with the raspberry sauce on a good '99, (other references were decidedly removed due to their unholy nature).

  • THE CALLOUSES - patch reinforcement of Kevlar/aramid//epoxy on the tail rails,  (these boards get pretty abused from being dragged up the sand

  • THE SKIN - I want the outer laminate to be composed of 6oz Diolen//epoxy on its own, with a hot coat, MAYBE GLOSS, if I’m feeling groovy (I hear the veteran shapers smacking their lips at me, ready to take their bite - ‘’BUT WAIT,‘’ I cry, ‘’HEAR ME OUT! FOR AMUSEMENT, IF NOTHING ELSE!‘’)

To my understanding, Diolen is a material with properties of high elasticity, compared to most other laminate materials. ALSO, it is pretty resistant to abrasion, not quite on par with Kevlar/aramid, but much better than glass. Taking the Diolen-over PU pour foam as an outer ‘shell’, I propose that the board will be:

  • more tolerant of high impact/compression as the pliant, forgiving outer shell will (hopefully) flex/deform to absorb the force and (hopefully) bounce back to its original shape, instead of breaking brittly from brute stubbornness, not unlike a regular ol’ foamie.

  • more water resistant. In the event of the Diolen cracking, the closed-cell formation of polyurethane foam should localise/trap the leak and prevent the board from soaking out.

  • given the rigid nature of the carbon core, the high flex of the Diolen should maintain its overall ‘shape’, (OR should I thicken the Diolen with 1.5oz e-glass (or heavier??), and should the glass lay internal or external of the Diolen?)

 

That’s my food for thought - not quite a meal, more like a snack… just enough to make you want more. I suppose it’s just a different kind of sandwich.

Anyway, as far as I can tell, nobody has made a board like this (probably for good reason, possibly not). If you were in my position, full of mistakes yet to happen but willing to screw up as long as you dont have to peel off all that Diolen and pourfoam and go with the regular carbon-glass single lam instead

WHAT WOULD YOU DO?

(ANY THOUGHTS REALLY APPRECIATED HERE)

Thank you for your replies, I hope you’ve at least been entertained.

paudi.

[DISCLAIMER: I AM NOT TRYING TO OFFEND ANY SURF GURUS IN THEIR SHAPING RITUALS. I ONLY WANT TO LEARN, MAYBE EVEN SPARK A BIT OF CREATIVE INNOVATION]

2

PU pour foam spread all around will give you a mess, don’t Ask how i know LOL. For this epoxy foam resin work better but denser…

Diolen must be cover by something sandable. For toughness i would put diolen under carbon that spread load reduce cracks. Diolen over is good to resist abrasion. First trick is to well seal your blank with an epoxy micro silica past. Use “exotics” materials can cost lot of money and need specific tech, some would say vac bag, i don’t know your skills but for a first build at that size and shape i would avoid it and stay with fiberglass, lam one layer at a time. Glass is a good material, cheap and tough and keep some stiffness, you can finish with layers of epoxy micro mastic easy to sand lightweight fairing then paint.

3

I agree with lemat.

Also combining different types of fibres effectively is very hard, you need to match the stiffnesses otherwise they just add weight without adding any strength.

If you need stiffness, some UD carbon under skin and (E or S) glass at 45-45 over skin is the best option IMO.

I advice you to watch the following two video’s before you order the exotic fibres:

 

4

EPS covered with cork skins would be more impact absorbing than pour foam, and would resist water absorption better (glass over cork).

10’6" is a lot of skin to lay flat…

5

I do get the idea of using the diolen on the outside. It’s hard to sand, so I came up with the idea to have small channels at the lapline to hide the cuts. Haven’t done it yet, so I can’t tell you if it’s good advice. I used diolen under glass with no problems.

There are old threads were Greg Loehr talks about using diolen under glass on his rails, so I think that alone makes it legit to try.

Every surfer used a flame/torch to get the fuzz of his nylon builds. 

Why you want to use pour foam instead of the sandwich stuff like airex etc escapes me. 

I would skip the carbon part too. Use a multi axial layup, and look for the Vulcan hotseat thread /corrugation. 

Id say 45 on the rail is important. 

I guess you want  to have hard edges, add them after lamination with epoxy spackle. 

From your writeup I’d say you already have a plan, so go for it. My thoughts are just what I had in mind when I was thinking of building similar stuff. Lemat and Hans gave good advice. 

 

 

 

 

 

 

6

By all means;  Proceed with pics of progress.

7

Ohhhhkay, a few thoughts. Never built one of those but I can assure you I have fixed more than a few. The vast majority sacrifice everything for light weight. 

Core, fine. You can actually use contact cement to glue that foam together, more than strong enough, do a dovetail at the joint if you want to be cute with it. Hot wire cutter is your friend here. 

I would inllay some Aerolite foam under your deck for paddling abuse and a decent sized block for where the fin box will go. Otherwise, the fin will break off the first time somebody gives it a dirty look. 

Then the carbon fiber, yeah, that will work and the rigidity is a good thing, like a rowing shell wants to be rigid. Umm, at this point in time I would give serious thought to a vaccum bag setup, for the best lamination of this stuff you can get.

Now, your proposed layer of pour foam. Nope. Bukkake is not for you. Besides which, real soon you will have that nice carbon coated core rattling around inside a loose skin lined with crumbled pour foam and a lovely if wrinkled glass job on the outside… Instead, with your vaccum setup, go wild with Aerolite. Various densities and thicknesses, it comes in a lot of 'em., I’d use epoxy to stick it to the carbon, you want the best bond you can get.

Next, the final lamination. Glass, okay, Kevlar or carbon, fine. Vac-bagged on there, excellent. This elastic stuff- you want to bear in mind  that you have gone to a lot of trouble and expense to put that first layer of carbon on there, and it don’t stretch worth a damn, that’s its main function in life. And you will remember that you want to prevent flex, no? This stuff flexes, well, it may well shear off where it joins whatever you have it stuck to, like getting the wax off an Edam or Gouda cheese…Instead, rigid carbon, rigid foam, rigid outer lamination, it’s more or less a monocoque structure with the innermost foam as a male mold.   

Tail and rails and finbox, yeah, I’d lay up additional patches of plain glass cloth, so when somebody does a Gidget and drags it up the sand you have a rail left. When his idiot buddy stads it up in the sand and doesn’t think about a rock in there, you have a tail left. Fin box I told ya about already. They make thin peel and stick HDPE plastic sheet material that helps for the incorrigable rail draggers too. 

hope that’s of use

doc…