Author Topic: Hollow foil board construction method  (Read 6077 times)

jondrums

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Hollow foil board construction method
« on: December 16, 2022, 04:49:47 PM »
This post is to get discussion going on how to build a super lightweight "barracuda" style foilboard.   I'm sure such a thing could be built with female molds but shapes are evolving so fast now that we need a method with minimal upfront investment.  I'm thinking of a method that just requires a cnc router and typical wet layup vac-bag techniques.



The blocks of PVC foam are going to be seriously expensive, but the foam density could be varied for the hull vs. the deck.  We might even get away with using a 2-3lb EPS.    If the board is designed with a fairly simple deck that could be done with a sheet of PVC, or go with denser PVC underfoot and lighter PVC everywhere else.

Thoughts? Perhaps someone has tried this kind of method before?

tarquin

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Re: Hollow foil board construction method
« Reply #1 on: December 16, 2022, 08:01:44 PM »
Skip to about 2.30 if you don't want to watch all of it.

https://youtu.be/BvxwVmVNhFI


surfcowboy

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Re: Hollow foil board construction method
« Reply #2 on: December 16, 2022, 09:03:09 PM »
I wonder. Will the skin required to hold you be heavier than having a core?

I estimate yes. Blanks are light. They get heavy when laminated. But I don't know squat really. But a damn expensive experiment to potentially end up with a heavy board. I'll for sure watch and support ya.

Why not just hollow out or cut cores out of an eps blank like guys do with chambered balsa or redwood boards? Easy and you can make it as hollow as you dare.

burchas

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Re: Hollow foil board construction method
« Reply #3 on: December 16, 2022, 09:27:34 PM »

Thoughts? Perhaps someone has tried this kind of method before?

I had few projects that were done that way, not boards though. The reality was the end product didn't weigh a lot less than its eps counterpart and the cost was 2-3 times more.

Then there is the reality of dealing with one-offs which most likely won't yield the best result on a first go.

If you take a look at the weight and strength of production hollow boards from leading factories you won't see much if any weight difference between a hollow and and the EPS version.

These super light weight autoclave OC1 and race kayak you refer to are the result of a substantial investment and even boards that are made in those facilities like the Nelo made Speedboard  https://speedboardusa.com/product/speeder-gs/ aren't lighter than the equivalent eps sup due to the nature of the beast.
in progress...

PonoBill

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Re: Hollow foil board construction method
« Reply #4 on: December 16, 2022, 10:36:42 PM »
How do you plan to release the board from the PVC? If the mold isn't smooth and highly polished how will the board be finished? Filler and paint? That's heavy.

In essence, you're just planning to make a mold in a different way. There's nothing much wrong with that, but the general notion of traditional molds is very similar and the major source of the cost and labor of building them is ensuring that the part can be released.

Burchas is correct, there isn't going to be a huge weight difference. The most significant benefit of hollow boards like the SIC downwind boards is that you can drain them if they spring a leak. We all know you never get a waterlogged EPS board completely dry, they gain weight with every leaker.

You also need to figure out how to bag it without distortion. Not simple. you'd certainly have to use a perimeter bag instead of bagging the entire thing since the foam would get crushed or at least distorted in a full bag. I don't know how you would seal a perimeter bag to the foam.

But what the hell, give it a go.
« Last Edit: December 16, 2022, 10:53:26 PM by PonoBill »
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

jondrums

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Re: Hollow foil board construction method
« Reply #5 on: December 16, 2022, 11:25:43 PM »
I think you may be right that the end result isn't lighter than EPS foam construction.  It sure as hell will be more expensive and labor intensive

But I am certain that if nomex honeycomb is used as the core, it can be lighter.    I have no idea how to build something like that without a mold, but there might be a way

Hdip

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Re: Hollow foil board construction method
« Reply #6 on: December 16, 2022, 11:31:43 PM »
Isn't a hollow board what Marcus Tardrew built for James Casey for a M2O and swore off every doing that construction again?

tarquin

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Re: Hollow foil board construction method
« Reply #7 on: December 16, 2022, 11:34:48 PM »
You really need to use prepreg with nomex or all the resin runs into the cavities. Which means an oven as well.
 

Admin

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Re: Hollow foil board construction method
« Reply #8 on: December 17, 2022, 02:55:46 AM »
I have been thinking about this.   With a 18 x 18 inch printer, you could 3D print the board in carbon in five hollow sections with extra carbon struts and integrated foil boxes as part of the print (boxes are one with the shell and can be additionally ribbed out to all walls).  Alternately you could print in scanned wells for existing boxes and glue in boxes at those exact dimensions.  The sections walls (every 18 inches) would act as additional ribs.  The sections could interlock if needed.  You could then glue and laminate the whole thing in carbon. 

Essentially a home builder version of this, but for use as a lightweight core vs a finished hull.

https://www.youtube.com/watch?v=9U1UbMmNywA
« Last Edit: December 17, 2022, 03:50:46 AM by Admin »

EastCoastFoiler

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Re: Hollow foil board construction method
« Reply #9 on: December 17, 2022, 03:42:11 AM »
So the end result is a heavier skin(trade a thin laminate for something more substantial) and a lighter cavity/core(trade EPS for air).  This means the ratio of surface area to volume is a big driver of viability.  Bigger, more cavernous boards are a better fit while smaller/skinnier boards are worse. 

In this way this high $$$ construction method is better suited to lower performance shapes(thick, wide, flat is good - skinny, pointy, thin is bad)

Aviso made it work on some pretty small short boards though

burchas

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Re: Hollow foil board construction method
« Reply #10 on: December 17, 2022, 03:59:11 AM »
If I read it right the weight saving was the motivation for you?
When I was looking into the hollow construction, my motivation was a stronger construction with the ability to drain the board and never think about it again, just like Bill said. His reputation of destroying boards (and foils) is well documented so he would know.

I had few hollow boards, still have the SIC Standamaran. It's a 28 pound beast. I once dropped it from 3 feet onto concrete with barely a scratch.

Admin makes a good point with 3D printing. Not sure what the weight saving will be but there are already products on the market under this category: https://www.wyvesurf.com

Seems like a promising direction with 3D becoming more and more accessible.
in progress...

lazymodo

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Re: Hollow foil board construction method
« Reply #11 on: December 17, 2022, 05:27:42 AM »
I contacted the company in that 3d printed boat video a few years ago with questions about using the technology for race boards and at the time he said the tech wasn't there yet. He was printing work boats for the navy with .5" minimum wall thickness and he didnt think 2-3mm was possible yet. But now, who knows.
And for downwind i think a lot of people who have tried both a hollow channel board vs a foam cored one would agree the foam core feels better out in all that energy.
« Last Edit: December 17, 2022, 05:31:10 AM by lazymodo »

tarquin

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Re: Hollow foil board construction method
« Reply #12 on: December 17, 2022, 05:48:13 AM »
3D print a male plug. Don't leave it in the board. Like the vid I posted of the catamaran construction.

PonoBill

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Re: Hollow foil board construction method
« Reply #13 on: December 17, 2022, 10:11:02 AM »
3D print a male plug. Don't leave it in the board. Like the vid I posted of the catamaran construction.

I agree with Tarquin, in this kind of application 3d printing is most suitable for making molds or very thin components--like foil wings. The plastic used (PLA, ABS, PETG, PC, Nylon or carbon-reinforced versions of some of the above) in current heat-extruded 3D printing is heavy. Unless you used a lot of infill you really can't bag it usefully without distortion or simply crushing the print. I've been making a lot of low- or no-infill parts for Faux Drives (homebuilt Foil Drives) and most of the parts have about the same volume-to-weight ratio as hockey pucks.

The weird thing about Tarquin's video is the misconception of the people who filmed it that the carbon hull requires filling, sanding, and painting because it's not fiberglass and doesn't have a gel coat. It doesn't have a smooth, void-free finish without filler because it's made over a male mold instead of inside a female one, where the gelcoat can be sprayed into the mold against a highly finished, polished surface. You can still gelcoat a male molded or EPS-cored part. But the finish quality will depend on filling, sanding, and polishing the surfaces. Gelcoat is just a thick polyester resin--essentially just thick paint--no magic there.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

finbox

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Re: Hollow foil board construction method
« Reply #14 on: December 17, 2022, 05:39:53 PM »
Here is a airplane wing construction video - I uses CNC mold & infusion with lots of bonding of parts together with a post cure oven. https://www.youtube.com/watch?v=74KQ7Rne48k Perhaps some ideas may be used from this?

 


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