Author Topic: Foil and board R&D  (Read 5405 times)

blueplanetsurf

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Foil and board R&D
« on: May 28, 2017, 01:15:49 PM »
We have been working on foil and board design which requires re-thinking design concepts.  For a SUP surfing board, you want to maximize maneuverability and carving turns while still maintaining enough stability and glide to catch a wave.  On a foil board, the board design is irrelevant once you lift off and you basically want to minimize the swing weight and size of the board once you are off the water.  Turning and carving rail to rail are not a concern on a foil board design (assuming that all you want to do is foil on it, not a multi purpose board).  So the primary design concerns are minimizing board size while maximizing lift, glide and tracking to catch the wave and have enough stability to paddle back out. 

Watching this video testing 7'6x30 Foil board, I noticed that the tail of the board often touches the water when I'm pumping, increasing drag and making it harder to keep the foil flying. 
https://youtu.be/5QwH3XosP7I

The foil is mounted 20" from the tail and it seems like the last part of the tail was not doing any good, so I decided to experiment and cut 10" off the tail to make the board 6'8 long, making the distance from the tail to the foil 10".



« Last Edit: May 28, 2017, 01:43:18 PM by blueplanetsurf »
Robert Stehlik
Blue Planet Surf Shop, Honolulu
Hawaii's SUP HQ
http://www.blueplanetsurf.com

blueplanetsurf

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Re: Foil and board R&D
« Reply #1 on: May 28, 2017, 01:30:57 PM »
So far, I'm really happy with the shorter board.  With the straight outline and double concave bottom shape with hard rails, the board still tracks relatively well and creates enough lift and glide to catch the wave.   Once the foil lifts off, it is noticeably easier to control and is easier to keep flying without touching the water. 
I have been working on a new foil design and recently tested the first prototype which was CNC'd from a solid piece of G10 fiberglass.  Since the foil is quite thick, it weighs a TON, so I was doubtful that it would work at all, especially with the smaller board. Just getting the board with the super heavy foil to the water was a pain.  Surprisingly, once on the water, the weight was not a big deal.  The heavy Foil wing actually acts like the lead keel on a sailboat and makes the board more stable when paddling.  Since the wing is submerged, the weight is not that noticeable.   Flying it also felt stable and easy to control although I'm thinking that once we make the mold so we can build lighter composite construction foil wings for production, they will fly more quickly and longer and certainly be easier to transport.   Here is a video using the shorter cut off board with the new, super heavy foil prototype, riding waves that are not steep enough to surf on a regular board:

https://youtu.be/kSM6k2n0vRk
« Last Edit: May 28, 2017, 01:37:58 PM by blueplanetsurf »
Robert Stehlik
Blue Planet Surf Shop, Honolulu
Hawaii's SUP HQ
http://www.blueplanetsurf.com

p06781

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Re: Foil and board R&D
« Reply #2 on: May 28, 2017, 02:48:32 PM »
Awesome video!  This obsession with the lightest foil isn't needed. Great observation "   The heavy Foil wing actually acts like the lead keel on a sailboat and makes the board more stable when paddling.  Since the wing is submerged, the weight is not that noticeable"

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PonoBill

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Re: Foil and board R&D
« Reply #3 on: May 28, 2017, 06:27:13 PM »
Very cool Robert. If weight is an issue at all for prototypes, you might try CNCing the shape you want from plywood and then laying on a few layers of carbon and a couple of fiberglass sanding layers. I've done five foil wings that way so far. the weight is reasonable, the shapes are predictable, and the build is quick.
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.

blueplanetsurf

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Re: Foil and board R&D
« Reply #4 on: May 30, 2017, 09:15:59 AM »
Thanks PonoBill, yes CNC'ing a wood core and glassing over it like you are doing would have been a better way to build this prototype than using solid G10.  Our manufacturer is used to making thinner kite foils, which are only as thick as surfing fins, so they are set up to use only G10. For the thick foil wing we designed it is total overkill and way too heavy.   It is good enough for testing though and once we make a few more tweaks to the design we will be ready to make a mold which will use a CNC'd high density foam core pressure molded with pre-preg carbon, which is basically the same way a high performance paddle blade is manufactured. 

I was surprised how well it worked despite the heavy weight and my takeaway is that the weight of the foil is not a big concern for performance and making a foil too light could actually be detrimental.  The board weight and size on the other hand has a big influence on how easy it is to fly and control the foil.  The reduced swing weight of a smaller, lighter board makes a big difference .
Robert Stehlik
Blue Planet Surf Shop, Honolulu
Hawaii's SUP HQ
http://www.blueplanetsurf.com

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Re: Foil and board R&D
« Reply #5 on: May 30, 2017, 12:52:28 PM »
That second video with your cut down sized foil board is spot on. Love this video shot from a drone too.
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PonoBill

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Re: Foil and board R&D
« Reply #6 on: May 31, 2017, 06:33:03 AM »
KeNalu paddles are made with a molded core instead of a CNC one, you can use a simple fiberglass mold instead of precision metal molds. But then your blade mold has to be very precise and handle high pressures without distortion. If you're aiming for production you might consider this direction instead of CNC, though that all depends on expected numbers.

I think masts could be made with mylar wrapping a mandrel rather than molding there would be some safety and strength benefits in using a wrapped mandrel instead of a two-piece mold with the inevitable thinned edges. I doubt the drag would be increased with a slightly rounded leading edge, especially at any angle of attack other than straight on.
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.

blueplanetsurf

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Re: Foil and board R&D
« Reply #7 on: May 31, 2017, 02:49:09 PM »
KeNalu paddles are made with a molded core instead of a CNC one, you can use a simple fiberglass mold instead of precision metal molds. But then your blade mold has to be very precise and handle high pressures without distortion. If you're aiming for production you might consider this direction instead of CNC, though that all depends on expected numbers.

I think masts could be made with mylar wrapping a mandrel rather than molding there would be some safety and strength benefits in using a wrapped mandrel instead of a two-piece mold with the inevitable thinned edges. I doubt the drag would be increased with a slightly rounded leading edge, especially at any angle of attack other than straight on.
Carbon construction masts are usually made of solid carbon, there is no foam core inside.  We will probably use an anodized aluminum mast and fuselage on our foils.
Robert Stehlik
Blue Planet Surf Shop, Honolulu
Hawaii's SUP HQ
http://www.blueplanetsurf.com

LM

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Re: Foil and board R&D
« Reply #8 on: June 07, 2017, 06:12:21 AM »
KeNalu paddles are made with a molded core instead of a CNC one, you can use a simple fiberglass mold instead of precision metal molds. But then your blade mold has to be very precise and handle high pressures without distortion. If you're aiming for production you might consider this direction instead of CNC, though that all depends on expected numbers.

I think masts could be made with mylar wrapping a mandrel rather than molding there would be some safety and strength benefits in using a wrapped mandrel instead of a two-piece mold with the inevitable thinned edges. I doubt the drag would be increased with a slightly rounded leading edge, especially at any angle of attack other than straight on.

Our paddle cores haven't been molded since the first generation (nearly 5 yrs. ago) which we had a ton of problems with. Since then they've been CNC cut PVC foam cores. The dimple problems in the beginning were caused by molded foam. It turns out the problems happen most often with thicker items being molded (but still quite a bit thinner than a hydrofoil wing) so I wouldn't recommend trying it, it'd likely be a nightmare.


blueplanetsurf

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Re: Foil and board R&D
« Reply #9 on: June 07, 2017, 05:45:07 PM »
Thanks for sharing that insight Lane, good to know!
Robert Stehlik
Blue Planet Surf Shop, Honolulu
Hawaii's SUP HQ
http://www.blueplanetsurf.com

 


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