Standup Zone Forum
General => The Shape Shack => Topic started by: jondrums on December 16, 2022, 04:49:47 PM
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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.
(https://i.imgur.com/eShpBzJ.jpg)
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?
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Skip to about 2.30 if you don't want to watch all of it.
https://youtu.be/BvxwVmVNhFI
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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.
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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.
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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.
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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
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Isn't a hollow board what Marcus Tardrew built for James Casey for a M2O and swore off every doing that construction again?
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You really need to use prepreg with nomex or all the resin runs into the cavities. Which means an oven as well.
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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
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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
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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.
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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.
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3D print a male plug. Don't leave it in the board. Like the vid I posted of the catamaran construction.
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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.
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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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Good choice of video, I watch all the Dark Aero videos. Those guys are amazing. There are three YouTube videos I watch religiously: Dark Aero, Easy Composites, and Welding Tips and Tricks. That wing structure is astonishing. Rigid enough to handle the flight characteristics of a high-performance aircraft and serve as a huge gas tank as well. The only thing I find a little odd is that the leading edge is formed as part of the support structure. I would have thought they would make the structure boxed and added the leading edge as non-structural.
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Technically speaking blanks are already "hollow" as in 90 something percent air. The Mike's Lab guys are using light density foam, like 1lb, for sub 10 pound SUP foil boards.
I have been playing around with lighter density, to me this seems easier (cheaper and faster) than hollow or chambered.
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Clay's on track. But I'll add that a blank made of pieces might be best. Central piece of 1.5lb and the nose and rails from ultralight or chamber them. Strong, light, minimal extra work.
Also I'll add that PeterJ and the SF crew's method of microballoon filler with no hot coating is the way. Far less resin, far less weight.
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Spend money on good products. Spread tow carbon, the right epoxy and maybe some innegra. A wet out table.
As others have said I don't think you can easily make a hollow board lighter than an EPS core without spending quite a bit of money and experimenting.
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Thanks for all the great comments. I'm running a bunch of different math on this, and I agree with so much of the points people are making - this type of construction is really best for high ratio of volume to surface area.
Looking at the numbers - nomex honeycomb core is really incredible stuff - 3lb/ft3 but holy crap is it expensive. And yes, it would have to be done in a mold with prepreg.
check this out:
https://www.catsailingnews.com/2020/04/windfoil-tech-patrik-air-inside-the-carbon-nomex-hollow-board.html
https://www.youtube.com/watch?v=7ihSg_9s7Qw
Looks like a great way to make a $10k+ board that might be a little lighter
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I agree with Surfcowboy. Foam is lightweight in comparison to laminate. I've been making "hollow' boards for some time now and am satisfied with the results. Any density foam will do as long as you use divinicell/carbon in the standing/kneeling areas. Basically, I hotwire cut the board in 3 longitudinal sections( left,right and center), after 90% of shaping is done. Using a hot wire gouge to remove matching chambers of foam along entire length of board in each of these 3 sections. Chambers are approximately 4-6" wide, leaving about 1" of foam on both hull and deck. Columns between chambers are approx. 1.5" thick. All should be done being careful not to cut chambers into foil box area as well as leaving a bit more deck thickness in standing area, say 2". After chambers are completed, I use a hot steel rod to open communications between adjacent chambers. There is only one communication hole between chambers on left and right sides, at the tail. In essence, the foam along the stringer line is solid except for that one hole at tail. Hope that makes sense. I then insert 2 Gortex vents in the very nose, a left and a right, into the forwardmost chambers. When completed, I can then blow air into the left vent which travels down the complete left side of board to tail, crosses over to right side of board, and travels all the way up the right side of board to second vent in nose. This allows me to dry the board out completely should I get a leak. Total weight savings when removed foam blocks are measured, 1.5 lbs.(8' x 20" Barricuda style downwind board). When using a hot wire gouge or hot steel rod to make cuts or hole, you are simultaneously sealing those portions of foam by melting its surface. should water ever enter the chambers, it is far less likely to soak into the foam. Skinned with 1 layer of 4 oz Innegra, 1 layer of 4 oz fiberglass. Vacuum Bagged. Carbon cloth under where necessary (standing area, foil boxes forward). This technique has reduced the nose/swing weight quite effectively. Is it a stupid amount of extra work for 1.5 lbs.? Maybe, but not for me.
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The Dave Brewer balsa board sitting over my head (hanging on my wall) is chambered. That board has never been wet and probably never will be. Expensive for a board but as art goes, it's cheap, and it is definitely pure art though a lot of the artwork is inside and invisible.
Some art is also inspirational. In my wall hanger, a lot more weight was removed since the medium was Balsa, and the chambering is longitudinal like SUPeter's method. Dave cut the rough-shaped board along its long axis, though the cuts were along the stringers rather than in line with the tracks. If I were building a Kalama-syle board I'd chamber the nose, tail, and any other non-weight-bearing areas. I'd do Dave Daum's trick of using door skins for the stringer, maybe two skins for the track reinforcement dropping to one skin in the nose and tail, or maybe light plywood or honeycomb all along the board with cutouts to match the chambers. The chambers in the balsa board are rectangular with corner filets and were cut with a router, but the shape and the cutting method should suit the core material and be strong enough for bagging. The chambers are blind for the outer two sections but run all the way through the center section. Add stringers to reinforce the tracks and the standing area of the deck and glue it back together. 1 1/2 pounds is worth the effort if you're doing it for yourself. That's probably about 25 percent of the foam weight and 20 percent of the total weight. More importantly, the weight is removed from the nose, where any weight gets slung around at the end of a long lever and is therefore more critical to performance.
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I had called JonDrums to talk about some other ideas when he posted this.
I have worked up some ratios on the weight of foam vs. lamination. Here are my assumptions and resulting matrix.
- Foam Density 1.6 lbs per foot cubed
- Lamination = Carbon Single Layer 6 oz per square yard
- Carbon to Resin Ratio: Layed up on plastic and placed on blank 60% Carbon : 40% Resin
- No weight for TRACKS nor Stringer or beefing up the deck area - NAKED Blank Only
- Shape of Board is Downwind 7' 6" x 24" x 6" for example
Using Volume of a Rectangular BLOCK vs Final board shape (~ 52% reduced) and then estimating the Surface Area:
--> 120 Liter Board would weigh 8.2 lbs with 1.6 lbs foam
Add ~ 2 or 3 lbs for the installation of TRACKS and deck reinforcement.
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Different FOAM Densities would result in the following weights. Blank and Lamination only.
This shows the influence on foam weight to final board weight.
Do these look roughly accurate?
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I haven't personally seen a 120L board that is sub 10lbs - but those are all more like surfboard shapes with a lot of surface area. I agree with your math though, its similar to what I was calculating.
My conclusion is that the only way to really win on this is to build it with pre-preg (30/70 resin cloth) and nomex honeycomb - one shot in a two piece female mold = $$$. It'll be bombproof but niggling issues like how to get the boxes installed really well will really make it a nightmare. I'm super impressed by those formula windsurf boards I linked up above. Seems like they nailed the process.
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I love the ideas here and the desire to innovate.
Meanwhile I'm on board #9 and have a 8.8lb 4'9" wing board with 6oz carbon and 6oz glass, boxes and a handle.
It's not done but I'm doing Peter's barely filled microballoon method so I think I'll be good.
It cost under $200 in new parts since I used all my leftovers. Y'all boys need to go to the garage and get sticky and dusty. It'll all work out.
If you wanted to get crazy I'd follow Peter's crazy carbon tow reinforcement path. Shape the bottom and rails on a blank like a canoe, leave the top off. Lam a top on a thin sheet of eps. Cut out all the foam from the bottom "canoe" and then put in the carbon tow superstructure. Glue the top on and ride.
You're welcome. But thank Peter, he paved that road.
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Different FOAM Densities would result in the following weights. Blank and Lamination only.
This shows the influence on foam weight to final board weight.
Do these look roughly accurate?
Did you use true weights for EPS? EPS always comes in right at the legal minimum. See this chart. https://carpenter.com/wp-content/uploads/2022/04/TypicalPropertiesC578.pdf
So 1.5# actually weighs 1.35#
1.25 is 1.15. This is the ideal EPS for wing, when you can find it. The factories don’t make much of it. Low demand.
1.0 weighs 0.85#
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If you wanted to get crazy I'd follow Peter's crazy carbon tow reinforcement path. Shape the bottom and rails on a blank like a canoe, leave the top off. Lam a top on a thin sheet of eps. Cut out all the foam from the bottom "canoe" and then put in the carbon tow superstructure. Glue the top on and ride.
You're welcome. But thank Peter, he paved that road.
Yes, that's a very clever approach to Kalama-style canoe boards. It's really the weird design that sparks all this innovation. For a common surfboard shape it wouldn't be practical. I'd jump in and get all sticky and dusty, but the last thing I need is another project.
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. I'd jump in and get all sticky and dusty, but the last thing I need is another project.
That comment was pure Pono bait to see if you'd do it. 😆 Hope someone does.
I'm literally in a cold sweet trying to not start a DW SUP right now. Gonna do a tow boogie if I can stay away from the foam and carbon for a minute.