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Wing profile info for backyard hydrofoil builders

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PrfctChaos
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Re: Wing profile info for backyard hydrofoil builders

Postby PrfctChaos » Wed Sep 23, 2020 2:14 pm

Some upgrades have followed.

-The number of airofoils being considered has been expanded by adding more databases. Now up to about 2500 airofoils, covering quite a diverse range.
-Have added lift induced drag (the classic version for a Elliptical lift distribution). This isn't important for airfoil selection (which is the main goal here), but interesting to look at none the less. So the drag given is now the sum of profile drag and induced drag.
-Made a comparison tool to show the drag effects of a range of wingspans and surface areas for the wing design being considered (example below). Can be used to find the surface area sweetspot or to help decide if its worthwhile increasing or decreasing wingspan.
Typical example below:
Capture.PNG
Capture2.PNG
Capture2.PNG (23.03 KiB) Viewed 471 times
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ericmsil (Wed Sep 23, 2020 3:11 pm)
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ericmsil
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Re: Wing profile info for backyard hydrofoil builders

Postby ericmsil » Wed Sep 23, 2020 3:10 pm

PrfctChaos wrote:
Wed Sep 23, 2020 2:14 pm
Some upgrades have followed.

-The number of airofoils being considered has been expanded by adding more databases. Now up to about 2500 airofoils, covering quite a diverse range.
-Have added lift induced drag (the classic version for a Elliptical lift distribution). This isn't important for airfoil selection (which is the main goal here), but interesting to look at none the less. So the drag given is now the sum of profile drag and induced drag.
-Made a comparison tool to show the drag effects of a range of wingspans and surface areas for the wing design being considered (example below). Can be used to find the surface area sweetspot or to help decide if its worthwhile increasing or decreasing wingspan.
Typical example below:

Capture.PNG
Capture2.PNG
hi PrfctChaos.

what tool do you use to do these calculations?

this calculation is only relative to the naca profile for the front wing and back wing? What about the shape of the wing and the dihedral angle of the wing as it proceeds in the choice?

best regards

Eric

nemoz
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Re: Wing profile info for backyard hydrofoil builders

Postby nemoz » Wed Sep 23, 2020 3:27 pm

well the Aquila93 I'm using is absolutely not the best for high speed, but because i'm using for surfing or for winging and i will never reach more than 25 km/h speed, the lack of performances but the easy building still push me to use it even for the next foil i will build soon...

PrfctChaos
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Re: Wing profile info for backyard hydrofoil builders

Postby PrfctChaos » Wed Sep 23, 2020 11:28 pm

ericmsil wrote:
Wed Sep 23, 2020 3:10 pm
PrfctChaos wrote:
Wed Sep 23, 2020 2:14 pm
Some upgrades have followed.

-The number of airofoils being considered has been expanded by adding more databases. Now up to about 2500 airofoils, covering quite a diverse range.
-Have added lift induced drag (the classic version for a Elliptical lift distribution). This isn't important for airfoil selection (which is the main goal here), but interesting to look at none the less. So the drag given is now the sum of profile drag and induced drag.
-Made a comparison tool to show the drag effects of a range of wingspans and surface areas for the wing design being considered (example below). Can be used to find the surface area sweetspot or to help decide if its worthwhile increasing or decreasing wingspan.
Typical example below:

Capture.PNG
Capture2.PNG
hi PrfctChaos.

what tool do you use to do these calculations?

this calculation is only relative to the naca profile for the front wing and back wing? What about the shape of the wing and the dihedral angle of the wing as it proceeds in the choice?

best regards

Eric
Hi Eric,

The tool that was used for the profile lift / drag calcs is called Xfoil. Ive doublechecked results with more than one other sources and happy that it all checks out. The program managing the data I wrote and the final display / interface is in excel, for its usefull graphing.

Yes, only trying to help with profile selection mainly (of front wing), because it looks like the main area where many DIYers just play russian roulette instead of doing the calcs. So I'm offering to do the calcs for any DIYer.
But can also help with area selection (there is usually a sweetspot for a given speed range / weight and wingspan).
For the plan shape (wing shape as seen from above), each designer can decide for themselves really. I would just recommend a elliptical area disttibution, since clasically it minimises lift induced drag, but there is still lots of freedom here for wings to end straight at the trailing edge, or curve back or forwards, whatever the designer feels like. Also notable that a 40% straight taper is basically very close to a elliptical lift distribution, so has been used for a long time for its ease of fabrication.
Regarding dehidral or anhedral or wingtip shape, this is for each designer to play with.

Cheers

PrfctChaos
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Re: Wing profile info for backyard hydrofoil builders

Postby PrfctChaos » Wed Sep 23, 2020 11:36 pm

nemoz wrote:
Wed Sep 23, 2020 3:27 pm
well the Aquila93 I'm using is absolutely not the best for high speed, but because i'm using for surfing or for winging and i will never reach more than 25 km/h speed, the lack of performances but the easy building still push me to use it even for the next foil i will build soon...
Still happy to run the calcs for your own speed range, weight, area, wingspan combination. To look athow other profiles might compare against aquile93. Aquila might come up looking good for the application, or maybe the calcs might persuade you to try another. In anycase, I have seen a few other profiles that i think would also be well suited to your fabrication technique, that will sit well on a flat surface. Will show a picture of the one that comes up highest in the list, when running calcs for your wing.

nemoz
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Re: Wing profile info for backyard hydrofoil builders

Postby nemoz » Thu Sep 24, 2020 8:13 am

I will upload here my foils details soon.. but talking about weight, I'm sure my weight plus the board plus the wing is not the correct amount because a part if it usually is taken by the lift of the wing... talking about speed I saw Naish reaching 27 km/h and Kai Lenny reaching 34 if I'm not wrong... I think that 27 as maximum for me it is reasonable. Talking about weight 63 kg plus 5kg plus the wing (no idea I have to weight it), I think 70 kg in total make sense. In the next 2 week I will start building the next 2 foils I would love to follow your proposals on profile.

ericmsil
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Re: Wing profile info for backyard hydrofoil builders

Postby ericmsil » Thu Sep 24, 2020 3:05 pm

onofoil in instagram make 3 videos about hydrofoils:

wing thicknes and profile:



high vs low aspect wing:



tail angle:


best regards

Eric

PrfctChaos
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Re: Wing profile info for backyard hydrofoil builders

Postby PrfctChaos » Thu Sep 24, 2020 11:09 pm

nemoz wrote:
Thu Sep 24, 2020 8:13 am
I will upload here my foils details soon.. but talking about weight, I'm sure my weight plus the board plus the wing is not the correct amount because a part if it usually is taken by the lift of the wing... talking about speed I saw Naish reaching 27 km/h and Kai Lenny reaching 34 if I'm not wrong... I think that 27 as maximum for me it is reasonable. Talking about weight 63 kg plus 5kg plus the wing (no idea I have to weight it), I think 70 kg in total make sense. In the next 2 week I will start building the next 2 foils I would love to follow your proposals on profile.
I think those peak speeds for Robby and Kai were in MPH, 27 MPH and 34 MPH, but that was just peak speeds so wouldn't worry to much about that in anycase (Probably using kite foils and very powered for a top speed run). I think the maximum average cruising speed is more important. I've read that 10 Km average speeds of just under 30 Km/hr is considered very fast in winging, so have gone with the 10-35 Km/hr normal design speed range in this case. Let me know if you would like to change it.

Have chosen a 1050 mm wingspan. Let me know if you think it will be too wide for winging. But I think it is reasonable since guys are using the 1150 axis and having a good time.
Area of 1500 cm^2 looks to be a sweet spot for this setup. Results below, RG1495 profile comes up top.
Capture.PNG
Capture2.PNG
Capture2.PNG (21.66 KiB) Viewed 272 times
For construction techniques, are you using a similar method to RichR2, shown here?
viewtopic.php?f=107&t=2407327

Even with this fabrication technique, I thin it is possible to do it with any profile. When making the wood templates, one just needs to include a little stand on the trailing edge, to set the angle of attack, so that the template will stand on a flat surface with the correct AOA. Simple sketch below:
Capture3.PNG
PS: The other flat bottomed profiles, Aquela93, Clarky did not feature in the top 100 of the list of results. Neither did the wings that were cambered enough to stand by themselves on a flat surface.

nemoz
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Re: Wing profile info for backyard hydrofoil builders

Postby nemoz » Fri Sep 25, 2020 7:19 am

Not so sure if I can do something similar with my actual technique, because I'm used to laminate top and bottom in the mean while over a flat bottom mould. I can think to laminate it in 2 times and have not a flat bottom... I wi kindly ask you one last test... talking about kmh or mph I think yes I was just thinking in an european standard..

ericmsil
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Re: Wing profile info for backyard hydrofoil builders

Postby ericmsil » Thu Oct 01, 2020 3:24 pm

Hi PrfctChaos.


I'm trying to make my wing high A.R to wing. I was thinking about a 1.0 m wide wing with 16 cm of chord. That she could have a good head forward / good glide ratio after reaching her cruising speed I thought something between 10 km/h min. and 20 km / h max. I imagine using the shape of the image attached.

Which profile would be most suitable for this condition?


My weight is 90 kgs

Best regards

Eric
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