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Wing profile info for backyard hydrofoil builders

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fluidity
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Re: Wing profile info for backyard hydrofoil builders

Postby fluidity » Fri Aug 21, 2020 4:20 pm

PrfctChaos wrote:
Wed Aug 19, 2020 12:10 am
<cut>
I think Fusion 360 is without a doubt the best free (Free for hobbyists) modelling software around. Airfoiltools.com is a excellent resource for finding info on the airfoil shape (Once it is known which airfoil to look for on there).
<cut>
You're likely right for the majority of hobbiests.
I come from a different angle, some fairly intense programming experience at times in my life and I've made my own custom programs in OPENSCAD shape programming language. For me it's easier. It's self documenting if you make enough descriptive notes as you go and it offers a very direct way to apply maths. It's not for everyone, I dabbled deeper than most to create a cylinder drawing program when it's already an included primitive operation but by drawing a cylinder a triangle at a time in automated series to mathematically selected coordinates it gives me the power to intricately manipulate surfaces. This is an example. And it finally got me up in a couple of short glides while kneeling today.
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nemoz
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Re: Wing profile info for backyard hydrofoil builders

Postby nemoz » Fri Aug 21, 2020 5:35 pm

I used aquila9.3% in my monofoil, super easy to build due to the flat bottom profile so i can vacuum it on a curved flat mould to obtain the final foil without even sanding it. For sure is not the fastest profile but, the easiest to replicate manually in my opinion.

PrfctChaos
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Re: Wing profile info for backyard hydrofoil builders

Postby PrfctChaos » Fri Aug 21, 2020 10:07 pm

nemoz wrote:
Fri Aug 21, 2020 5:35 pm
I used aquila9.3% in my monofoil, super easy to build due to the flat bottom profile so i can vacuum it on a curved flat mould to obtain the final foil without even sanding it. For sure is not the fastest profile but, the easiest to replicate manually in my opinion.
Good point. It might be worthwhile me throwing a flat bottom wing profile database into the mix as well. Certainly has fabrication perks.
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dirk8037
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Re: Wing profile info for backyard hydrofoil builders

Postby dirk8037 » Sat Aug 22, 2020 10:05 pm

Hi,

this is quite interesting but does not really solve the problem of foil selection in the first.

As you stated out most people take something the read about (Speer H120, Eppler) or something that appeals to them.
Or they seek special aircrafts with high glie numbers or known for their robustnes
So did I H120 to be on teh save side, Fx60100 because curiosity kills the cat
(still in Build, I have next Sunday a CNC course at our fab lab....)

But it is full on stabbing in the dark.
Given the fact that air most likely can not scaled to water (is it in you model?) and plain flight behaviour does not relay compares to eg pump foiling. And the differences between those 2 foils are so vast, same eg with Onda foil side by side with a Gong that thickness and apect ration are second to that.

Did you ever thought of testing different concepts against each other on a wider basis just to get hold of that?
I guess it comes down to low speed glide vs resitance at higher speeds. Agility and adaption to wight then can be handled by template parameter as aspect ratio and sweep.

If I would ask for your services than I would choose half a dozen different ones with may be 2 different thicknesses (eg. 2 and 3 cm) and let the run.....

Dirk

PS found also this here
https://www.dropbox.com/s/gf6x7xn9ik2zrvf/lift.xls?dl=0

PrfctChaos
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Re: Wing profile info for backyard hydrofoil builders

Postby PrfctChaos » Sun Aug 23, 2020 12:09 am

Hi Dirk,

The flow medium being water is covered in the calculations (I think I have 20°C seawater shown on the example at the top). These sorts of lift/drag calculations are valid for flow in incompressible fluids, which covers air (at speeds well below speed of sound) and normal speeds in water (before ventilation or cavitation causes problems).

Also, I am only optimising over NACA series profiles at the moment, they cover the basic shapes well in my opinion. Will add a few more databases over time.

Happy to help, the info I need from your side to do some runs is:
- The speed range you want to use the foil for. (Min and Max speed). I show 20-40km/h in the example at the top for a fastish surf wing.
- Your selected wingspan. Good idea to see what typical wingspans are for the type of foil you are going for. Shorter wingspan generally turn faster, wider wingspan can help to make a more efficient faster foil. Its a bit of a tradeoff.
- Foil area, I can also make some suggestions for the area based on the calcs, but if you have a area in mind let me know.
- Your weight.

Cheers
-

PrfctChaos
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Re: Wing profile info for backyard hydrofoil builders

Postby PrfctChaos » Sun Aug 23, 2020 1:16 pm

Update: Have thrown the profiles listed below into the mix as well. It Includes the Aquila 9.3%, fx60100, the ag series, clarky series and sd70 series among others, will see how they perform. So future optimisations include these as well as NACA4 and NACA5 series.
Capture.PNG
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downunder
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Re: Wing profile info for backyard hydrofoil builders

Postby downunder » Mon Aug 24, 2020 9:06 am

PrfctChaos wrote:
Tue Aug 18, 2020 6:29 am
Maybe some pics will get more DIY'ers motivated to make wings... Here is a fast Wood and Carbon wing, made to fit a Neil Pryde fuse.

Capture.PNG
Capture2.PNG
Yes we do make it ;) Plus the rest.
IMG_0580.JPG

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downunder
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Re: Wing profile info for backyard hydrofoil builders

Postby downunder » Mon Aug 24, 2020 12:31 pm

Chaos,

Im puzzled with your build tho, which wood is it? And how thick are the strips?

PrfctChaos
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Re: Wing profile info for backyard hydrofoil builders

Postby PrfctChaos » Tue Aug 25, 2020 12:04 am

downunder wrote:
Mon Aug 24, 2020 9:06 am

IMG_0580.JPG

Very nice. That spread tow finish is looking great.

Might have to order a few meters for a future project...

PrfctChaos
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Re: Wing profile info for backyard hydrofoil builders

Postby PrfctChaos » Tue Aug 25, 2020 12:09 am

downunder wrote:
Mon Aug 24, 2020 12:31 pm
Chaos,

Im puzzled with your build tho, which wood is it? And how thick are the strips?
That is Merbau. It is very strong and tough. It is possible to get a variety of shapes of laminated posts or beams, used for exposed architectural members in houses.

That section is about 12.6 mm thick at its thickest.


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