Author Topic: Ultralight Board Designs  (Read 24153 times)

Beasho

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Ultralight Board Designs
« on: January 09, 2023, 11:05:16 AM »
Let’s Make a Sub 10 lbs SUP Foil board. 

I have run the numbers and this should all be possible.  There are Pros and Cons

Background:
•   Board designs are changing so fast you might pay $1,500 or more and get a board that is obsolete in 6 months
•   Figure out how to minimize the investment in ‘Unnecessary’ infrastructure.  This includes 1) Material 2) Cost and 3) Weight
•   The board does NOT have to last 10 years.  The objective might be to have 30 sessions on this board. 
•   Invest in the Foot area and the TRACKS.  BUT Don’t over index on the TRACK reinforcement.  I have been a Tuttle advocate since Day 1.  For 30+ years Tuttles were the only boxes that wouldn’t rip out of windsurfers.  Tuttles go Deck-to-Deck.  There has to be some substantial material extending from Deck to Deck.  BUT there could be a very light Matrix of foam and carbon rod, with solid top and bottom carbon layer for example that would suitably hold the load for dual tracks.

Estimated Weights of Final boards.  This matrix shows the estimates for a board with:
1)   Dimensions will be similar to a Barracuda shape 7’ 6” x 22” x 6” around 120 liters
2)   XPS Foam:  1.5 lbs per Cubic Foot.  Water Proof and therefore MINIMAL intrusion of water from Dings.
3)   1 Layer of 6 oz of Carbon around the entire board.  Estimate using a 60% fiber to 40% resin ratio.  It will be vacuum bagged.  No final gloss coat.
4)   Dual Tracks will be added.  Ideally 1 lbs of additional weight for the Tracks and necessary structure.

Total IDEAL weight:  8.8 lbs.  It will NOT be pretty.
« Last Edit: January 09, 2023, 12:03:06 PM by Beasho »

Beasho

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Re: Ultralight Board Designs
« Reply #1 on: January 09, 2023, 11:05:55 AM »
Additional thoughts:  XPS is closed cell foam.  It will NOT absorb water. It weighs 1.5 lbs per cubic foot.  EPS is lighter but when you get a ding it will absorb water quickly. 

There have been several prototype boards in the neighborhood made with XPS.  One board did NOT even cover all the XPS but left exposed foam in Non-Critical areas.  After 2 years the foam, with little care, started to flake off from chips and/or dings. 

I have been testing another approach that would be to GORILLA glue the DRY fiber to the XPS.  The objective would be to provide a lightweight jacket to the foam.  It would carry load in TENSION only, leaving the fiber attached to the foam but NOT fully wetted out. 

Advantages:
1)   Ding Prevention.  The exposed XPS dings with a fingernail.  A test piece of foam with carbon was very durable.  Another test piece with 2.7 oz fiber glass also worked very well and was resistant to puncture but much lighter than the carbon sample.  (Video to follow).
2)   Added stiffness.  The thought being to have a light wrap of fiber on the nose and tail to carry load in tension only.  Compressive loads would have to be carried by the XPS foam.  But the shell of fiber would still be stiffer and more resilient than foam alone
3)   The skin material is porous.  Some people have experienced delamination related to XPS foam.  Because the foam is closed cell ANY moisture that is trapped between the foam and an impermeable skin is at risk of evaporation and delamination.  IF the fiber is porous this would significantly reduce the risk of delamination. 

Sample XPS with 6 oz CARBON Gorilla glued and vacuum bagged.  Pretty slick looking final product.  AND pulling out a single fiber was VERY difficult.  Meaning the gorilla glue was adhering very well to the closed cell foam.
« Last Edit: January 09, 2023, 11:57:58 AM by Beasho »

Beasho

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Re: Ultralight Board Designs
« Reply #2 on: January 09, 2023, 11:06:10 AM »
Here is a sample of XPS wetted out with Gorilla glue and then laminated with 2.7 oz fiberglass.

The theory is that Fiberglass may be MORE resistant to puncture than carbon.  This sample was 2.7 oz so LIGHTER than a 6 oz Carbon for example.

The block of foam weighed 4.81 grams
Fiber added                       2.16 grams
Total                                 6.96 grams

Added a micro layer of gorilla glue and squeegeed off as much as possible. 

Final weight:                    7.74 grams.

Conclusion:  Ratio of Fiber to Resin = 2.16  : 0.78  = 73% Fiber to 27% resin

For the None-Structure / Critical-Heavy-Load-Bearing parts of the board: Outer rails, tail and nose this material could further reduce weight. 
« Last Edit: January 09, 2023, 11:59:04 AM by Beasho »

Beasho

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Re: Ultralight Board Designs
« Reply #3 on: January 09, 2023, 11:43:32 AM »
I put a test sample in a bucket of water for 24 hours.  Weighed the sample before and after. 

It took ~ 1 hour for the sample to dry out to weigh within 1% of the original weight suggesting that the absorption of the closed cell foam was VERY low.
« Last Edit: January 09, 2023, 11:45:58 AM by Beasho »

PonoBill

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Re: Ultralight Board Designs
« Reply #4 on: January 09, 2023, 03:30:02 PM »
Very cool ideas, as usual, a sharp left turn from the direction everyone else is taking though that's how things actually progress. Though you're basically reinventing the boogie board. Mr. Morey made some surfboards about 15 years ago that were actually pretty good though they had a hell of a lot of flex. That reminds me, I have to find out where Sol Morey is. Super nice guy, the son of the inventor of foam boogie boards. Sol has the most astonishing balance I've ever seen. Soul Surfer to the tenth power.

I think it's provable that mast tracks glued to light plywood stringers that go top to bottom are as light and strong as any tuttle box. I did a fairly serious test of that when I ran smack into the bunker at Ka'a, flat out. Bent the shit out of an Axis mast base but the board (by Dave Mel) was undamaged.

I think stringers like that complement your idea of all the reinforcement under your feet and around the mast and the rest of the board can be mega-light. I've been thinking that myself for the 8' Kalama-style board I asked Mark Raaphorst to build for me. The long nose and deep canoe hull should be as light as possible. There is XPS available that's lighter than 1.5#, but you have to order it--it's not what they stock at lumber yards. Not cheap, but neither are shaped boards. Greenguard is very strong EPS, I got a 4" X 4' X 8' for about a hundred bucks when I was thinking about building a foil board. It's a bit heavier than some lightweight EPS but it's silly strong even just bare. Not as strong as PVC foam, but in the spectrum between 1.5 EPS and whatever PVC it's probably 1/2 of the way: https://xps.supply/product/kingspan-greenguard-4-x-4-x-8-square-edge-board-insulation-21/
« Last Edit: January 09, 2023, 03:46:30 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.

Beasho

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Re: Ultralight Board Designs
« Reply #5 on: January 09, 2023, 06:59:14 PM »
Here is a ding test on the XPS foam.  Using a mechanical pencil on the bare foam vs. the foam with 2.7 oz Fiberglass cloth that has been glued DRY to the surface of the XPS.

The pencil easily dings the bare foam. 

But you will see I had to push pretty hard to get the pencil to pierce the material with just 1 layer of fiberglass.

https://youtu.be/xY4QMltT-ZU

Beasho

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Re: Ultralight Board Designs
« Reply #6 on: January 09, 2023, 07:09:22 PM »
Things are coming together FAST. 

My shaping Amigo JOSH said "Come over and Check it out."  Josh and KYLE(our local Downwind leader) have a template made out of Masonite.

Thank you!  Thank you!  Thank you!!!!!!

They are a bit sour on XPS after one of their XPS boards melted in the sun. They are making their versions out of EPS.  This one is XPS with SQUARE super boxy rails.

I may just leave it BOXY.  They are going to add more chines.  I might just round the bottom a little bit and the top for better laminate adhesion (square edges bad).

The current dimensions are:

7' 10" X 21" X 6" Thick

Current Weight 6 lbs 13.8 ounces.  Estimated Volume 130 Liters  (before any more trimming)
« Last Edit: January 09, 2023, 07:34:08 PM by Beasho »

Beasho

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Re: Ultralight Board Designs
« Reply #7 on: January 09, 2023, 07:39:37 PM »
Potential weight with CLEAN build is estimated at 8 lbs 14 ounces (No deck pad, no handle, leash plug).

All Talk at this point.  Feedback Welcome!

You can see the idea is to have 30" of 6 oz Carbon WRAPPING the entire structure.  2X Layers on the top, under foot (I might economize based upon Goofy stance).

Then 1 Extra Layer running Rail-to-Rail from the front to the Back of the Tracks.

More on the Track reinforcement later.  But I will be using 1/4" carbon Arrows to handle vertical compressive load.  Thinking is 6 arrows biased towards front, and outside each track.  3 on each side of tracks.  I have done a version of this with wooden dowels so far without failure.   

surfcowboy

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Re: Ultralight Board Designs
« Reply #8 on: January 10, 2023, 06:43:26 AM »
I like a lot of these ideas.

Peter J has worked on the box thing. Carbon arrows, or use 1/4" pieces of balsa laminated with carbon like I did. If you want light and not as many dings use 4oz glass everywhere but structural places (nose/tail for example.) Fill it like Peter (and the SF wing guys do) with microballoon paste instead of hot coat. Super light.

There are skinning methods that help waterproof eps (epoxy slurry like Kings, etc)

Don't tell your hippie bay area friends you're building big foam things that may not last long. But yes, this is doable. It's basically a race car construction.

Surfside

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Re: Ultralight Board Designs
« Reply #9 on: January 10, 2023, 09:33:56 AM »
Keep it simple on the shape....love it! 8oz for the tracks? What tracks will you be using? 16"?

Beasho

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Re: Ultralight Board Designs
« Reply #10 on: January 10, 2023, 10:35:04 AM »
Peter J has worked on the box thing. Carbon arrows, or use 1/4" pieces of balsa laminated with carbon like I did. If you want light and not as many dings use 4oz glass everywhere but structural places (nose/tail for example.) Fill it like Peter (and the SF wing guys do) with microballoon paste instead of hot coat. Super light.

There are skinning methods that help waterproof eps (epoxy slurry like Kings, etc)

Part of the idea here is that The SKIN will be Porous.  IT does NOT have to be waterproof.  This eliminates and need for additional fill layers, or microballoons.  Finishing a board adds weight, time and cost.  Eliminate all 3 with a quick Gorilla glue and Fiber matrix that lets the fabric breath and therefore is LESS likely to delaminate.  In theory.

JonathanC

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Re: Ultralight Board Designs
« Reply #11 on: January 10, 2023, 12:41:20 PM »
Can you please explain the ‘carbon arrows’ concept
Thanks

SUPeter

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Re: Ultralight Board Designs
« Reply #12 on: January 10, 2023, 01:28:53 PM »
I love this thread. When I'm out of the OR, I will read it letter for letter. 

Carbon fiber arrow shafts are ultralight , very strong carbon tubes designed to withstand compression quite well. They are also pretty strong when flexing and twisting forces are encountered. First, I use them to both attach the boxes to both hull and deck by coring them straight through board(alongside track boxes) and using carbon fiber tow to attach ends to hull, deck and boxes. I use about 3-4 pieces along each track box.  Second,  Using full length shafts(3-4) run along boxes and forward onto hull prevents that compression failure just in front of track boxes. I only do this on hull since carbon cloth alone does not provide enough compression resistance and creasing can develop from the high cantilevered force. Gotta go back to work. I hope this quick explanation helps.

BTW- Is anybody using Innegra?  I love it! It's a very light weight fiber with exceptional strength for ding resistance. 1, 4 oz layer of Innegra cloth covered by 1, 4 oz layer of glass is far more ding resistant than 1 layer of carbon cloth.

One more thing, hollowing out(chambering) structurally insignificant areas (nose, rails, tail) will also decrease weight. I cut out 1.5 lbs of foam from a DW board recently.
« Last Edit: January 10, 2023, 01:49:38 PM by SUPeter »

PonoBill

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Re: Ultralight Board Designs
« Reply #13 on: January 10, 2023, 03:03:23 PM »
One more thing, hollowing out(chambering) structurally insignificant areas (nose, rails, tail) will also decrease weight. I cut out 1.5 lbs of foam from a DW board recently.

There's a lot of opportunity for hollowing out sections since the most readily available XPS is 2" glued and stacked sheets to achieve the desired thickness.

I've never seen black XPS like that. What's the source?
« Last Edit: January 10, 2023, 03:06:47 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.

surfcowboy

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Re: Ultralight Board Designs
« Reply #14 on: January 10, 2023, 03:40:39 PM »
Beasho, I get the POUROUS!!!!!!!!!! part. It's done all the time in the Crissy wing crew as you know.

Just contributing an idea for others who might follow this path. I no longer finish my boards with hot coats. I use Peter's slurry method. They still get sealed. They are light as hell. They don't delam. Sanding isn't a pain. Try it guys.

One thing to test. Although the foam won't absorb water, check the weight when you get out. Water retained under the carbon will still likely add more weight than a few grams of resin and microballoons. Would love test results on that if you build one.

Pro tip. Gorilla Glue foamed up can replace K-Y jelly and it's lighter.

 


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