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Extruded Aluminium hydrofoils

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grob
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Extruded Aluminium hydrofoils

Postby grob » Tue Jun 27, 2017 8:59 pm

Hi,

Not sure how the forum works, so I hope this post is Okay.

I am a builder of aluminum hydrofoil extrusions and I have had a lot of interest from kitesurfers in the last few months asking for a smaller foil.

As a result of that interest I have just created a new product called the Full Foil 13 which is a 13cm chord foil.

Image

It can be seen on my website www.windknife.com

Is this likely to be useful for kitefoilers?

Cheers
Gareth

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Re: Extruded Aluminium hydrofoils

Postby BWD » Wed Jun 28, 2017 3:25 am

Interesting. Looks smaller than what is common.

Kitefoil masts need lots of torsional rigidity -- webs/tubes inside that also solve another problem --they can be threaded to attach to other components.
Looks like you may need a die mod for that...?

Max thickness is usually at 40-45% for good performance.
The picture in your post looks more like 25-30%.
Need a different die for that.....?

In other words your picture looks more like some propeller/rotor/HG section than a hydrofoil as I know them.

Also, don't know where you're at but kitefoil mast skin thickness is usually uniform and probably 2mm-ish.

I am not an engineer just an enthusiast observing trends in these things for a few years....

Finally the proof is in the pudding -- if itworks well and doesn't break, great!

Work something up and trial it for a 100 hours or so --things are very empirical in kitefoiling.

And shoot for a chord 15-20cm --27 sounds like huge extra wetted surface.

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Re: Extruded Aluminium hydrofoils

Postby rynhardt » Wed Jun 28, 2017 9:30 pm

Awesome concept!

I like the fact that you can reshape the profile a bit but still retain a smooth curve.
You could probably even create a delta fairly easily by cutting the trailing edge at an angle and simply clamping the edges together.
There are radii on the inside already so you could probably bond a tube into it as extra reinforcement or as a big dowel to join two sections together.
Fill with some PU foam for additional compression strength.

:thumb:

grob
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Re: Extruded Aluminium hydrofoils

Postby grob » Thu Jun 29, 2017 10:08 pm

Thanks for your feedback.

You are correct the foils are designed to take reinforcing tubes in the radii, the FF13 is designed to accept a tube or rod with an outside diameter of 1/2" or 12.7mm,

Larger diameter rods can be inserted to alter the width, here is an example.

Image

The foil is a NACA 0012 section and is 2mm thick.

The FF13 foil has a 13cm chord the FF27 has a 27cm chord which is probably a little large for this forum but they can be shortened as shown below.

Image

I was thinking about adding some additional design tools to the web site like a lift calculator and a strength calculator, if you can think of anything that would be useful I am very open to suggestions.

Cheers

Gareth

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Re: Extruded Aluminium hydrofoils

Postby BWD » Fri Jun 30, 2017 2:48 am

If you look at the French forum kitefoil.forumactif.org you can see a lot of info from development of different designs - both professionally made and homemade.
Most of the good info there is in French. Google translate helps if you don't speak it. Also try reverso for translation when google isn't doing it.
There is lots of info for example comparing torsional rigidity - a key property. Examples of metal, composite and hybrid foils, different aero sections etc....

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rynhardt
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Re: Extruded Aluminium hydrofoils

Postby rynhardt » Fri Jun 30, 2017 9:15 am

grob wrote:
Thu Jun 29, 2017 10:08 pm
Thanks for your feedback.

I was thinking about adding some additional design tools to the web site like a lift calculator and a strength calculator, if you can think of anything that would be useful I am very open to suggestions.

Cheers

Gareth
The price point and possibly the ease of use of working with readily available aluminium profiles is attractive.
However, for a DIY guy like me, it still represents a time and cost investment before I get a finished product.
And even then it will need additional refinement to make it perform adequately.

But if you could design a reasonably performing foil and show us how to build it with your profiles, it becomes an easy sell.
I.e. What do we use for a fuselage? Aluminium square tube? How do we attach the foils to the fuselage? etc.

So, a beginner's kit, with plans and a bill of materials, would be incredibly useful.

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Re: Extruded Aluminium hydrofoils

Postby NYKiter » Sat Sep 16, 2017 1:07 am

I have been trying to get these guys to create 4" foil for some time now.....and the only vendor in the USA sells them at odd lengths....they dont seem to get it....and shipping from the UK where they are made is outrageous....

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Re: Extruded Aluminium hydrofoils

Postby coffeeking » Sat Sep 16, 2017 1:24 am

Don't worry, in the UK we find shipping from the US to the UK outrageous too!

I found these a while ago and to be honest I was considering using it as mast.


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