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[jatkinson]

Hi,

I have just discovered this forum, and it seems to be a great resource.  I am in the planning stages of a board that I have not seen tried here or on sways.  I would like to attempt a fully hollow board similar to an Aviso, although I may keep the core on the first one and if it proves to be durable try another with no core.

My idea is to fabricate balsa rails & tail and cover them completely with carbon fiber sleeve to form a stiff one piece perimiter.  Then I will attach skins of (from outside in) 2 layers S glass 4-6oz , 2 layers of 1/8 balsa, 2 layers 6 oz carbon fiber.  I plan to vac bag the whole thing in stages over a foam form then once all the pieces are complete set the form aside and bond them all together with the final layer of glass wrapping completely around the rails both ways (top to bottom and vice versa).

I have attached a quick and dirty sketch of what i have in mind, which is not even close to scale but will hopefully give the general idea.

Has anyone ever attempted this before?  What are your thoughts on my layup?  Any obvious pitfalls that I should be aware of?

I have made a test panel of the deck/hull to see how strong it will be and will be jumping up and down on it to test it out once the epoxy fully cures. 

In order to keep this post reasonably short I have not gone into details on my plans for the order of events for shaping etc, but I believe that part will work.  My main concern is strength and if this is even a viable concept. 

Thanks for your feedback.

J

[Jarrod]

Cool idea!   Here's a thought...   How about build it in stages like a regular compsand without the added complexity of making halves that fit together.  Then, once it's complete, drill a hole in the nose and one in the tail, and pour in a solvent to melt the foam core out.  Viola, hollow surfboard!

[jatkinson]

I had thought of disolving the foam but dismissed it as being rather anti-green.  Although I will have a hole for a vent and perhaps another for a leash plug...

My test panel was a flop.  I think that the glass/carbon would have worked, but the two layers of balsa seperated severly weakening the structure. 

[soulvoid]

Hi,

While I think it's cool with coming up with new ways to build a board, I'd abandon the idea of core less board unless the goal is just to find a new way to build a board. A couple of reasons for this: The weight of the EPS core is very light for a shortboard at ~1lbs and the strength you get from it is hard to get from the same weight in the skins without using very advanced techniques and expensive materials(if at all). It's so much easier to build a board with a core than one without.

[Ray Maltby]

Hey Jatkinson
I'm a Hollow wood board builder who is trying to find common ground with the compsand method.
I'm toying with the idea of something like this:

Ray Maltby

[surfdad]

I did a lost foam hollow carbon and end grain balsa wakesurfer...shoot, at the end of 2007/beginning of 2008.

This is the build thread:

http://www.wakeworld.com/MB/Discus/messages/559019/524050.html

I used Xylene to dissolve the foam - definately not "green"   In short I shaped an EPS core, attached Balsa rails and a thin end grain Balsa skin top and bottom.  Laminated the whole thing with Carbon.  Just before the hotcoat the LOG weighed 8 pounds. 

I couldn't get a few layers Carbon to be stiff enough to support someone without either foam, or honeycomb, or balsa as a structural member.  It needed something as a skin or way too many layers of carbon to make it stiff enough. 

Maybe someone has the answer?

[Kit Sidwell]

I personally don't think a fully hollow board is gunna work. You could definitely build one that would hold together, and maybe even get the weight down a bit.
But I feel that the board would end up super stiff. The thickness/stiffness of the outer skins that would be required to span all that open space would also make it very rigid longitudinally.

That honeycomb core board by Kevincc is a really cool idea, I really admire the simplicity of construction. I went through a whole analysis of honeycombs when I was deciding what direction to take for my hollow (still in progress).
Honeycombs are definitely the lightest weight - highest strength option, but there's just one problem! They result in huge stiffness....
Making hollow boards flex seems to be the biggest challenge to me.
I don't know of anyone who has successfully made a sub - 6 pound hollow that flexes well.
Thats what i'm trying, not promising anything tho 

[Huck]

I started a thread under "solid wood rails", but my comments probably belong here!  I also am working on a couple of completely hollow boards.  In my case, I'm just experimenting with pushing the limitations of building technique.  I don't think my boards will be remarkably light.  But I'm trying for a practical, strong, sturdy board that is reasonably light, and surfs well for my needs (not a high performance surfer!).

[StrangeBrew]

if you wanna do a hollow board that'll hold up, you gotta look at the avisos. they use fairly thick honeycomb panel construction to distribute the load bearing forces from the deck to the rest of the structure.

took them a looooong time to get their layups right so that the boards weren't overly stiff, but still stood up to the abuse of "standing". From your preliminary sketches, I would say "won't work".

The benefits of using a superlightweight EPS core with *just strong enough* skins are multifold, not the greatest of which is having something to lay your exterior panels up on as a shape; most hollow boards are built in to female molds and then assembled in parts. Simply not an option for the homebuilder. The second and third benefits are distribution of forces by the core (spreading loads manes that you don't have to have the same kind of panel stiffness) and the internal dampening effects, making the board feel more like the traditional pu/pe we've all become accustomed to with the added benefit of being able to control the flex through panel stiffness as well as structural shape.

The common HWS construction being used these days STILL uses something to support the panel structure (ribs/stringers) and no matter what anybody tells you, those boards are heavier than a comparably sized, equally strong compsand...

[Huck]

I agree that if lightness is your goal, then a traditional compsand board will be lighter, i.e. wood veneer over foam.  My goal is to experiment with the limitations of my rail system - i.e., can the rails "carry" the structure?  And really, just a learning experience.

Your plan sounds very interesting.  I have no idea how or if it will work.  Are you still pursuing this?