Author Topic: Vunderfoil  (Read 11349 times)

Admin

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Re: Vunderfoil
« Reply #30 on: December 12, 2022, 10:13:31 AM »
I think current foil manufacturers are missing an obvious bet. They sponsor kids with supernatural talents to showcase their expensive gear, that no kid could possibly buy without willing investment from Dad and/or Mom. The target audience is geezers and sub-geezers, and the marketing message should be simple: "Our wings are so great that even Bill can do this". Cut to a video clip of me wobbling through a jibe, blowing a tack, and straining to get to my feet during a knee start. Marketing magic. You're welcome.

Then again I'm not sure of Admin's ambitions but the thought of doing this commercially makes me gag. It will be great fun, and perhaps it can stave off the inevitable decline of my cognitive ability. Wait, what was I writing about??

My interest in foil gear is entertainment, edification and personal enlightenment.  This is a pleasure ride.

PonoBill

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Re: Vunderfoil
« Reply #31 on: December 12, 2022, 10:17:15 AM »
The CFD program to use is XFOIL.  This is a really simple 2D CFD for foil sections.  You can get lift and drag vs. angle of attack for various reynolds numbers (speeds). 

That sounds kind of promising, it would be nice to not just try stuff blindly. I've never completely understood Reynolds Number, but I don't generally equate it to speed but rather inertia--which of course includes velocity as a factor--and viscosity of the working fluid. Given the much higher mass and viscosity of water vs. air I wonder if CFD intended for airfoils is relevant to hydrofoils.
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.

PonoBill

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Re: Vunderfoil
« Reply #32 on: December 12, 2022, 10:20:16 AM »
My interest in foil gear is entertainment, edification and personal enlightenment.  This is a pleasure ride.

I assumed so, but good to know we are in complete alignment. You know very well I'm allergic to the actual responsibility involved in real business.
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: Vunderfoil
« Reply #33 on: December 12, 2022, 10:23:42 AM »
My comment was that what is being used by foil makers is already there, whether intentional or not, and that you can confirm this for yourself by reverse engineering (as in your image). 

What I am saying is that no, they are in fact NOT in those databases.  I already confirmed that.  Subtle differences in shape do make quite a difference

jondrums

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Re: Vunderfoil
« Reply #34 on: December 12, 2022, 10:30:37 AM »
I've never completely understood Reynolds Number, but I don't generally equate it to speed but rather inertia--which of course includes velocity as a factor--and viscosity of the working fluid. Given the much higher mass and viscosity of water vs. air I wonder if CFD intended for airfoils is relevant to hydrofoils.

You are right about the Reynolds number including viscosity of the fluid, and it also includes the approximate scale of the bodies under study.  But after that, higher speed -> higher reynolds number. 

For water, use a Reynolds number of about 0.8x10^6 for 15 mph and go up and down linearly from there.

And yes, XFOIL works quite well for both air and water - that's exactly what the reynolds number is there to compensate for.

tarquin

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Re: Vunderfoil
« Reply #35 on: December 12, 2022, 10:30:50 AM »
You need to use a program for hydrofoils.
 I have been lucky enough to meet people that have been involved in some pretty high end foiling sailing. They said the major break through was designing hydrofoils not just using existing NACA shapes.
 What you see doing is awesome and I love it. It will work and you will make some great stuff. But if you want to give it that little bit extra some proper CFD will make a big difference.
 It would be interesting to know if the Armstrong foils are different to other foils.
 
 

Hdip

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Re: Vunderfoil
« Reply #36 on: December 12, 2022, 10:41:22 AM »
I think current foil manufacturers are missing an obvious bet. They sponsor kids with supernatural talents to showcase their expensive gear, that no kid could possibly buy without willing investment from Dad and/or Mom. The target audience is geezers and sub-geezers, and the marketing message should be simple: "Our wings are so great that even Bill can do this". Cut to a video clip of me wobbling through a jibe, blowing a tack, and straining to get to my feet during a knee start. Marketing magic. You're welcome.

Isn't this what AXIS is all about already? Stiffest mast! The "standard" fuses with the mast position in a dumbed down position. Massive wings larger than almost any other manufacturer.

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Re: Vunderfoil
« Reply #37 on: December 12, 2022, 11:07:34 AM »
You need to use a program for hydrofoils.
 I have been lucky enough to meet people that have been involved in some pretty high end foiling sailing. They said the major break through was designing hydrofoils not just using existing NACA shapes.
 What you see doing is awesome and I love it. It will work and you will make some great stuff. But if you want to give it that little bit extra some proper CFD will make a big difference.
 It would be interesting to know if the Armstrong foils are different to other foils.

I am very interested in that.  I will do more digging when we get closer to complete.  If anyone knows of an option offhand that accepts common export file types, I would love to know.  My gut is that we stand to gain a lot more efficiency and usability from the non section related adjustments than from any potential improvements to sections, but of course that is all hot air at this point.  There is some funny stuff looking back at this vid.  https://youtu.be/wvy2OzfH4N4?t=1143

Hdip

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Re: Vunderfoil
« Reply #38 on: December 12, 2022, 11:20:49 AM »
These guys do a lot of computer analysis. Might be able to get some tips from them. This is the only thing I could find of it with an easy search. The designer has posted on other forums talking about it though.

https://www.indefoil.com/foildesign/mast-thickness-drag

PonoBill

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Re: Vunderfoil
« Reply #39 on: December 12, 2022, 11:41:50 AM »
The Armstrong video is pretty cool. I like their stuff. the only reason I went for axis initially was the connection of the fuselage to the wing--I knew I could reproduce that connection in wings with my primitive capabilities.

Every youtube video I look at these days offers me all kinds of Autism information in the sidebar videos. Somebody has been ratting on me.
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.

Califoilia

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Re: Vunderfoil
« Reply #40 on: December 12, 2022, 12:18:47 PM »
I think current foil manufacturers are missing an obvious bet. They sponsor kids with supernatural talents to showcase their expensive gear, that no kid could possibly buy without willing investment from Dad and/or Mom. The target audience is geezers and sub-geezers, and the marketing message should be simple: "Our wings are so great that even Bill Califoilia can do this". Cut to a video clip of me him wobbling through a jibe, blowing a tack, and straining to get to my his feet during a knee start. Marketing magic. You're welcome.
Fixed it for you, because I know of one company that has done that for a couple years now...and that same "geezer foiler" has demos on the beach for folks to "try before they buy". :-X ;D
« Last Edit: December 12, 2022, 12:20:56 PM by Califoilia »
Me: 6'1"/185...(2) 5'1" Kings Foil/Wing Boards...7'10 Kings DW Board...9'6" Bob Pearson "Laird Noserider"...14' Lahui Kai "Manta"...8'0" WaveStorm if/when the proning urges still hit.

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Re: Vunderfoil
« Reply #41 on: December 12, 2022, 11:37:16 PM »
These guys do a lot of computer analysis. Might be able to get some tips from them. This is the only thing I could find of it with an easy search. The designer has posted on other forums talking about it though.

https://www.indefoil.com/foildesign/mast-thickness-drag

One interesting thing that I have found is how many sections are in use on a foil kit.  We tend to think wings and mast, but foil sections or partial foil sections are also being used for pedestals, bulbs and connections.  In the link he is not only testing mast width, but also a completely different section.  Not a criticism, just a note of interest, because there is no perfect way to test there.  This is actually very easy to do by mistake in software and great care needs to be taken to maintain your section (at least to remain intentional).  He is testing two NACA sections, not that they would use those :)
« Last Edit: December 13, 2022, 12:08:18 AM by Admin »

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Re: Vunderfoil
« Reply #42 on: December 12, 2022, 11:49:24 PM »
As mentioned in the OP we can now hot swap sections (downloads, scans, tweens, morphs, banana) and export to all common file types, so if we have software we can simulate.  I put in a ticket with Autodesk regarding their CFD.  It appears to be windows only??  but I still have a windows machine here if needed:).  Fusion has built in simulation features which are excellent but not applicable for wind or fluid.  I found a Fusion app store extension but it is goofy.  Fusion has a simulation extension https://www.autodesk.com/products/fusion-360/simulation-extension?term=1-YEAR&tab=subscription , which I now want for other uses but it doesn't do wind or fluid AFAICT.  I see them moving towards a unified cloud based platform for everything (which is what Fusion 360 is becoming) so hopefully the CFD will become tightly integrated soon.  I know that I would spring for the simulation extension pack if this were there.  Here is there CFD.  It looks extremely fiddly, even by Autodesk standards and I think it would be a great job for Bill.  Hah!

https://www.youtube.com/watch?v=nS9SfKLdkw4
« Last Edit: December 13, 2022, 12:11:07 AM by Admin »

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Re: Vunderfoil
« Reply #43 on: December 13, 2022, 12:49:09 AM »
Oooh, my printer and a buttload of CF filament (PA-CF and PC-CF) plus goodies shipped today.  Should be ready to rumble soon...

PonoBill

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Re: Vunderfoil
« Reply #44 on: December 13, 2022, 10:58:38 AM »
Here is their CFD.  It looks extremely fiddly, even by Autodesk standards and I think it would be a great job for Bill.  Hah!

Yikes, that looks like at least a three Concertatm job.
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.

 


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