Forums > Stand Up Paddle Foiling

DIY tail wings/ stabs

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Created by wicka 1 month ago, 8 Aug 2020
wicka
VIC, 6 posts
8 Aug 2020 5:00PM
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Hey guys, seen a few posts on people making their own front wings but wanted to see how people have been making their own tail wings. As most would know it can completely change the feel of the foil. As such I have a few questions?

- Are you making them out of solid carbon? Then shaping after?
- simple lay up, or using Some sort of a mould?
- I've had a few ideas on how to make them but wanted to see what people have been doing.
- vac bag or poor mans vac bag?

cheers in advance.

jonescb
NSW, 12 posts
8 Aug 2020 6:57PM
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I foam cut a naca210 350wide 65 chord and wrapped in carbon and glass. Not bagged just sandwiched between eva foam. Its about 6mm thick. It took a massive amount of sanding and filling to make smooth. You would be better off shaping a tail with g10 or solid carbon.
Def worth it though I love the skatey feel and improved pump on my np med slim.


hilly
WA, 5579 posts
8 Aug 2020 6:03PM
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jonescb said..
I foam cut a naca210 350wide 65 chord and wrapped in carbon and glass. Not bagged just sandwiched between eva foam. Its about 6mm thick. It took a massive amount of sanding and filling to make smooth. You would be better off shaping a tail with g10 or solid carbon.
Def worth it though I love the skatey feel and improved pump on my np med slim.



Fark that is ugly. You are saying it is better than these?

jonescb
NSW, 12 posts
8 Aug 2020 10:01PM
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Ha,
The stock small stab is pretty thick. Even when comparing the small+shim, the diy flat stab feels quicker and more efficient so its staying on for me- despite looking ugly!

surfcowboy
64 posts
9 Aug 2020 12:18AM
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You can lay up a panel or start from G10 for testing (faster) and then if it's a good one, make it out of carbon (or not actually.) A coat of poly or acrylic spray paint will make it look more pro.

I'd try to find that NP aqua color and make everyone think you're a pro riding prototypes from Kane. Hahaha.

Keep hacking!

waterlife
VIC, 46 posts
9 Aug 2020 9:52AM
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You have me intrigued to build a stab now - where can you buy G10 from?

RichJam
WA, 29 posts
12 Aug 2020 2:32PM
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Gameco is where I got mine from.
otherwise use some rear quad fins.

RichJam
WA, 29 posts
12 Aug 2020 2:32PM
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Gameco is where I got mine from.
otherwise use some rear quad fins.

Relapse
VIC, 376 posts
12 Aug 2020 5:36PM
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Easy to shape out of Paulownia wood. One layer of 4oz/300 GM/m2 carbon is enough

Capdog
VIC, 5 posts
13 Aug 2020 12:36PM
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Heres a couple of tails I made from some carbon plate I purchased online. Wasnt this exact link but something similar. Cost less than $100 AUD and I could get 3 tail wings out of it: www.alibaba.com/product-detail/cheap-price-top-quality-customized-forge_62418592958.html?spm=a2700.7724857.normalList.85.7c9b77305uPYQ4

Used an angle grinder to cut the shape and then sanded the foils in. Didnt take too long, probably an hour or so. Feels super fast and a little skatey. The smaller one is a bit too small I reckon but I use the larger one all the time. A fun cheap way to experiment.

You can also see that I got a couple more holes tapped into the fusilage to shorten it. Definitely makes it a bit more manoeuvrable.







Capdog
VIC, 5 posts
13 Aug 2020 12:37PM
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Select to expand quote
jonescb said..
I foam cut a naca210 350wide 65 chord and wrapped in carbon and glass. Not bagged just sandwiched between eva foam. Its about 6mm thick. It took a massive amount of sanding and filling to make smooth. You would be better off shaping a tail with g10 or solid carbon.
Def worth it though I love the skatey feel and improved pump on my np med slim.



Can we see the profile view?

waterlife
VIC, 46 posts
13 Aug 2020 2:37PM
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Capdog - do you know the specs (length/width) of the smaller and larger tail?

Capdog
VIC, 5 posts
13 Aug 2020 4:12PM
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waterlife said..
Capdog - do you know the specs (length/width) of the smaller and larger tail?


Hey waterlife,

The larger one is 36 cm wide with a 7 cm cord in the centre going out to about 4 cm on the edges.
The smaller one is 30 cm wide with a 6 cm cord in the centre going out to about 4 cm on the edges

jonescb
NSW, 12 posts
13 Aug 2020 8:16PM
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This is the section I used, I like it flat with zero angle of attack
airfoiltools.com/airfoil/details?airfoil=naca63a210-il


Capdog: they look great nice work, how thick are they?

Capdog
VIC, 5 posts
14 Aug 2020 11:01AM
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jonescb

My tails are 5mm thick.

wow looks like you took a much more technical approach. I kept the top of mine pretty much flat and then sanded out a foil on the bottom.

I generally have it flat but have tried shimming with a washer (probably 2mm) and a slice of credit card (maybe 1mm). I liked how giving the rear wing some angle of attack seemed to make it feel like the tail was really holding in and you could push turns a bit harder and it didnt feel like anything would breach. Downside was a definite speed reduction, feels like someone has a vacuum cleaner sucking on the rear of the foil, keeping it in the water but slowing it down. If the wave was decent this was actually helpful to keep you more in the pocket while doing turns but nobody foils to go slow.

Also cut an old credit card out and have it between the carbon wing and aluminium fuselage to reduce corrosion.

Dommo49
97 posts
14 Aug 2020 12:43PM
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Select to expand quote
Capdog said..
Heres a couple of tails I made from some carbon plate I purchased online. Wasnt this exact link but something similar. Cost less than $100 AUD and I could get 3 tail wings out of it: www.alibaba.com/product-detail/cheap-price-top-quality-customized-forge_62418592958.html?spm=a2700.7724857.normalList.85.7c9b77305uPYQ4

Used an angle grinder to cut the shape and then sanded the foils in. Didnt take too long, probably an hour or so. Feels super fast and a little skatey. The smaller one is a bit too small I reckon but I use the larger one all the time. A fun cheap way to experiment.

You can also see that I got a couple more holes tapped into the fusilage to shorten it. Definitely makes it a bit more manoeuvrable.








Counter sink the bolt head holes if you can - you'll really feel the difference in drag

danish
19 posts
14 Aug 2020 1:52PM
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Capdog - How do you transfer the Naca profile to the foil? Cut our cardboard templates?

juandesooka
374 posts
14 Aug 2020 2:51PM
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Keeping it simple...i made a rough copy of gofoil 18n stab with plywood and a sander and a few layers of cloth. Probably cost $10 in materials and worked great for 20 sessions or so until I cracked it torquing too hard with the screw gun a few more layers next time at connection point). These are flat and pretty simple design, far as I can tell. I added some down curve just at the tips.

Have also made wings with g10...pretty easy as you just sand or grind it then it's done, no worries about glassing. Material is expensive and hard to find though (at least in Canada). But for a small stab you wouldn't need much at least.

Capdog
VIC, 5 posts
14 Aug 2020 5:41PM
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Dommo49 - I counter sunk them a little bit on the larger wing but was worried about the wing being too thin and weak. Could probably go a little deeper.

Danish - Youll have to ask jonesscb as he did the naca thing

Mokuleia
47 posts
10 Sep 2020 3:02AM
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As promised, here is my take on DIY foil parts manufacturing. I hope this long post will give some of you idea on how to make your own parts and maybe start some collaborations on foil development. Grad yourself a nice drink and enjoy!

I have first experimented with all 3D printed parts, vacuum laminated with carbon fiber. The entire foil system came out relatively good, yet the mast was not rigid enough for my taste, despite the 10+ layers used on each side. Getting the mast not to twist during vac lam was also a challenge, and I quickly abandoned making my own masts until I find a better technique (more at the end of this post).


So, I recently grabbed a mast and fuselage from Blue Planet and I am building my front wings, stabs and mast plate adapters around it. These parts are done using a combination of 3D printed molds, silicone molds and 3D printed skeletons.

For the mast plate adapter, I basically design the part in a CAD software using the dimensions of the Tuttle. Then I 3D printed it, made a silicone mold of it and then used carbon fiber chopped strands and precisely cut patches along with epoxy resin. Finally I routed the back side of the harden part and voila!




One of the main advantage of the Blue Planet design is that it uses a "keyed" connection to secure the wings in place (a la Armstrong), providing a super secure and strong coupling. However, that created a challenge on my end, as I could not just 3D print the "female" part of that key for the wing. That's where silicone molding helps again, as I can make a CF/epoxy version of that part, glue it with the rest of the 3D printed wing and vacuum laminate everything with CF. Below is an example my HS1850 copycat I recently made with this approach.









I am leaning now toward full carbon parts and used the tail to test some "new" concepts. Basically, I am making 3D printed molds of the tail and then add CF panels with epoxy and epoxy/filler mix in it. It works fine, however, not destroying the mold is pretty difficult, as the plastic can easily delaminate and break apart. Using the same technique as described above for the front wing female key part, I have made a tail wing adapter so I can change its the AOI with shims.





So were do we go from there? After a year of experimenting with 3D printed parts, I can safely say that it is not an option for the mast for sure. It works fine for the wings, especially if you want quick prototyping, but full carbon parts are obviously far better. This brings me to the new tool I am putting together in order to make my own molds (first in MDF and eventually in aluminum): the big CNC. I hope to get my first mast be the end of the year. Stay tuned!




Piros
QLD, 5983 posts
10 Sep 2020 9:29AM
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Wow that is insanely good re the M8 NP titanium-plated bolts sticking up out of the thin rear stabs , just use std S/S ones the actual head size is smaller and they sit flatter with a lower profile, those NP heads are pretty chunky.

PrfctChaos
WA, 42 posts
10 Sep 2020 8:31AM
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Select to expand quote
Mokuleia said..
As promised, here is my take on DIY foil parts manufacturing. I hope this long post will give some of you idea on how to make your own parts and maybe start some collaborations on foil development. Grad yourself a nice drink and enjoy!

I have first experimented with all 3D printed parts, vacuum laminated with carbon fiber. The entire foil system came out relatively good, yet the mast was not rigid enough for my taste, despite the 10+ layers used on each side. Getting the mast not to twist during vac lam was also a challenge, and I quickly abandoned making my own masts until I find a better technique (more at the end of this post).


So, I recently grabbed a mast and fuselage from Blue Planet and I am building my front wings, stabs and mast plate adapters around it. These parts are done using a combination of 3D printed molds, silicone molds and 3D printed skeletons.

For the mast plate adapter, I basically design the part in a CAD software using the dimensions of the Tuttle. Then I 3D printed it, made a silicone mold of it and then used carbon fiber chopped strands and precisely cut patches along with epoxy resin. Finally I routed the back side of the harden part and voila!




One of the main advantage of the Blue Planet design is that it uses a "keyed" connection to secure the wings in place (a la Armstrong), providing a super secure and strong coupling. However, that created a challenge on my end, as I could not just 3D print the "female" part of that key for the wing. That's where silicone molding helps again, as I can make a CF/epoxy version of that part, glue it with the rest of the 3D printed wing and vacuum laminate everything with CF. Below is an example my HS1850 copycat I recently made with this approach.









I am leaning now toward full carbon parts and used the tail to test some "new" concepts. Basically, I am making 3D printed molds of the tail and then add CF panels with epoxy and epoxy/filler mix in it. It works fine, however, not destroying the mold is pretty difficult, as the plastic can easily delaminate and break apart. Using the same technique as described above for the front wing female key part, I have made a tail wing adapter so I can change its the AOI with shims.





So were do we go from there? After a year of experimenting with 3D printed parts, I can safely say that it is not an option for the mast for sure. It works fine for the wings, especially if you want quick prototyping, but full carbon parts are obviously far better. This brings me to the new tool I am putting together in order to make my own molds (first in MDF and eventually in aluminum): the big CNC. I hope to get my first mast be the end of the year. Stay tuned!





Very impressive work!!!

What process do you use to select your front wing profile? Also if you want to look at new profile options, give me a shout, I run optimisations over a couple of thousand airfoils to select the best one for a given weight / speed range / area / wingspan combination.

And here is a wing photo, since this is a DIY wing tread.




Mokuleia
47 posts
10 Sep 2020 12:00PM
Thumbs Up

Select to expand quote
PrfctChaos said..

Mokuleia said..
As promised, here is my take on DIY foil parts manufacturing. I hope this long post will give some of you idea on how to make your own parts and maybe start some collaborations on foil development. Grad yourself a nice drink and enjoy!

I have first experimented with all 3D printed parts, vacuum laminated with carbon fiber. The entire foil system came out relatively good, yet the mast was not rigid enough for my taste, despite the 10+ layers used on each side. Getting the mast not to twist during vac lam was also a challenge, and I quickly abandoned making my own masts until I find a better technique (more at the end of this post).


So, I recently grabbed a mast and fuselage from Blue Planet and I am building my front wings, stabs and mast plate adapters around it. These parts are done using a combination of 3D printed molds, silicone molds and 3D printed skeletons.

For the mast plate adapter, I basically design the part in a CAD software using the dimensions of the Tuttle. Then I 3D printed it, made a silicone mold of it and then used carbon fiber chopped strands and precisely cut patches along with epoxy resin. Finally I routed the back side of the harden part and voila!




One of the main advantage of the Blue Planet design is that it uses a "keyed" connection to secure the wings in place (a la Armstrong), providing a super secure and strong coupling. However, that created a challenge on my end, as I could not just 3D print the "female" part of that key for the wing. That's where silicone molding helps again, as I can make a CF/epoxy version of that part, glue it with the rest of the 3D printed wing and vacuum laminate everything with CF. Below is an example my HS1850 copycat I recently made with this approach.









I am leaning now toward full carbon parts and used the tail to test some "new" concepts. Basically, I am making 3D printed molds of the tail and then add CF panels with epoxy and epoxy/filler mix in it. It works fine, however, not destroying the mold is pretty difficult, as the plastic can easily delaminate and break apart. Using the same technique as described above for the front wing female key part, I have made a tail wing adapter so I can change its the AOI with shims.





So were do we go from there? After a year of experimenting with 3D printed parts, I can safely say that it is not an option for the mast for sure. It works fine for the wings, especially if you want quick prototyping, but full carbon parts are obviously far better. This brings me to the new tool I am putting together in order to make my own molds (first in MDF and eventually in aluminum): the big CNC. I hope to get my first mast be the end of the year. Stay tuned!





Very impressive work!!!

What process do you use to select your front wing profile? Also if you want to look at new profile options, give me a shout, I run optimisations over a couple of thousand airfoils to select the best one for a given weight / speed range / area / wingspan combination.

And here is a wing photo, since this is a DIY wing tread.





Beautiful piece dude! Have you tried it yet?

I glanced over the NACA library but got overwhelmed very quickly, so I ended up drawing something that was not too extreme with harmonious contours. I've been just scaling this profile to accommodate for different cord lengths or wing thicknesses.

I am curious about your profile selection approach. Are you running and fluid dynamic simulation (in water) for these profiles? What figure of merit do you use to decide which profile is best?







PrfctChaos
WA, 42 posts
10 Sep 2020 1:42PM
Thumbs Up

Select to expand quote
Mokuleia said..





PrfctChaos said..






Mokuleia said..
As promised, here is my take on DIY foil parts manufacturing. I hope this long post will give some of you idea on how to make your own parts and maybe start some collaborations on foil development. Grad yourself a nice drink and enjoy!

I have first experimented with all 3D printed parts, vacuum laminated with carbon fiber. The entire foil system came out relatively good, yet the mast was not rigid enough for my taste, despite the 10+ layers used on each side. Getting the mast not to twist during vac lam was also a challenge, and I quickly abandoned making my own masts until I find a better technique (more at the end of this post).


So, I recently grabbed a mast and fuselage from Blue Planet and I am building my front wings, stabs and mast plate adapters around it. These parts are done using a combination of 3D printed molds, silicone molds and 3D printed skeletons.

For the mast plate adapter, I basically design the part in a CAD software using the dimensions of the Tuttle. Then I 3D printed it, made a silicone mold of it and then used carbon fiber chopped strands and precisely cut patches along with epoxy resin. Finally I routed the back side of the harden part and voila!




One of the main advantage of the Blue Planet design is that it uses a "keyed" connection to secure the wings in place (a la Armstrong), providing a super secure and strong coupling. However, that created a challenge on my end, as I could not just 3D print the "female" part of that key for the wing. That's where silicone molding helps again, as I can make a CF/epoxy version of that part, glue it with the rest of the 3D printed wing and vacuum laminate everything with CF. Below is an example my HS1850 copycat I recently made with this approach.









I am leaning now toward full carbon parts and used the tail to test some "new" concepts. Basically, I am making 3D printed molds of the tail and then add CF panels with epoxy and epoxy/filler mix in it. It works fine, however, not destroying the mold is pretty difficult, as the plastic can easily delaminate and break apart. Using the same technique as described above for the front wing female key part, I have made a tail wing adapter so I can change its the AOI with shims.





So were do we go from there? After a year of experimenting with 3D printed parts, I can safely say that it is not an option for the mast for sure. It works fine for the wings, especially if you want quick prototyping, but full carbon parts are obviously far better. This brings me to the new tool I am putting together in order to make my own molds (first in MDF and eventually in aluminum): the big CNC. I hope to get my first mast be the end of the year. Stay tuned!










Very impressive work!!!

What process do you use to select your front wing profile? Also if you want to look at new profile options, give me a shout, I run optimisations over a couple of thousand airfoils to select the best one for a given weight / speed range / area / wingspan combination.

And here is a wing photo, since this is a DIY wing tread.








Beautiful piece dude! Have you tried it yet?

I glanced over the NACA library but got overwhelmed very quickly, so I ended up drawing something that was not too extreme with harmonious contours. I've been just scaling this profile to accommodate for different cord lengths or wing thicknesses.

I am curious about your profile selection approach. Are you running and fluid dynamic simulation (in water) for these profiles? What figure of merit do you use to decide which profile is best?










Thanks mate, yes that wing does go very well. It is a small wing made for fast kite foiling on the river and it has seen some really good sessions. Replaced it a few months ago with a racefoil unfortunately (mainly because the race foils come with such excellent masts). My surf wings still see quite a bit of action though, but this fast foil was one of the prettier ones I somehow managed to make. It is about time to make one or two more good looking ones again though I think, instead of just utilitarian.

I wrote a bit about the airfoil selection process here: and it shows one or two examples of what info the results show:
kiteforum.com/viewtopic.php?f=107&t=2407467

Have been adding more airfoil databases for evaluation over the last few weeks. By next week it will be finished with calculations for over 2500 airfoil sections from different databases.

Basically the optimisation program does calculations for your selected weight, wingspan, wing area and selected speed range (in water using the 2D lift/drag program called Xfoil),for the front wing at the required angle of attack for each speed. As a result it will give you a short list of 5 profiles, showing which will give you the least drag and the necessary lift over that speed range. It will also tell you the expected minimum stall speed.

If you are thinking of doing a new wing, just send through the below info and I can send you a airfoil suggestion and some results. (This would normally be quick on my end, but since I'm adding new profiles I'll only be able to send the results next week):
- The speed range you want to use the foil for. (Min and Max speed). For example20-40km/h possibly fastish surf wing. Anything goes here, but remember selecting a very low minimum speed (compared to wing area) might mean fat profiles get selected to get that low speed stall). It is a bit of a balancing act, but I can run a few options.
- Your selected wingspan. Shorter wingspan generally turn faster, wider wingspan can help to make a more efficient faster foil. Its a bit of a tradeoff (Lower induced drag for crappy turning). Lol, don't take it too seriously, I know the surfers love their High aspect wings these days.
- 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.

danish
19 posts
10 Sep 2020 8:18PM
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Sounds awesome @PrfctChaos!

Still courios on how you transfer profile to the design. How do you decide on the taper? and outline? What CAD program do you use?

@Mokuleia: manufacturing-wise: How do you use your mould for such thin/delicate structures as stab wing? Pour in expandable epoxy foam and lam over that afterwards?

Mokuleia
47 posts
11 Sep 2020 1:58AM
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Select to expand quote
danish said..
Sounds awesome @PrfctChaos!

Still courios on how you transfer profile to the design. How do you decide on the taper? and outline? What CAD program do you use?

@Mokuleia: manufacturing-wise: How do you use your mould for such thin/delicate structures as stab wing? Pour in expandable epoxy foam and lam over that afterwards?


Excellent point. Right now I am using epoxy/filler mix that I poor precisely in the mold after applying the layers of CF. That being said it is hard to gauge how much to use, so it is still trial and error for now. Full CF wings are usually made with prepeg CF with are precisely cut such that all pieces fit the mold entirely. Adding expandable foam is an approach I have considered also. However, I would add this between the CF during lamination.




PrfctChaos
WA, 42 posts
11 Sep 2020 7:13AM
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Select to expand quote
danish said..
Sounds awesome @PrfctChaos!

Still courios on how you transfer profile to the design. How do you decide on the taper? and outline? What CAD program do you use?

@Mokuleia: manufacturing-wise: How do you use your mould for such thin/delicate structures as stab wing? Pour in expandable epoxy foam and lam over that afterwards?



Once you know the name of the profile you want to use. Then the co-ordinate file for that airfoil can be downloaded from websites like airfoiltools.com/ and m-selig.ae.illinois.edu/ , and then just put that into you cad program of choice. (The format of the co-ordinates is usually a .DAT text file. Which is a list of X and Y co-ordinates for a chord length of 1 unit, so you would just scale it up to the chord length you need) Or print it out and cut out templates for hot wire cutting or a guide for hand-sanding or whichever manufacturing process of your choice.

For my process I usually 3D model in Inventor, then setup g-code in Fusion. Use the g-code to CNC out the wood or foam blank, that then gets vac-bagged with the laminate schedule of choice. But the guys getting good results from moulds (like Mokuleia) are making it look very tempting to experiment with that approach as well, especially for stabs at least.

Regarding wing outline (view from the top basically). I usually stick to a elliptical area distribution (The classic theoretical optimum case). But keep in mind that even straight wings with a 40% taper is basically 99% a elliptical lift distribution as well, which is easy to fabricate, that is why planes have been using that plan shape for so long, instead of elliptical.

It should also be noted that my profile selection program helps to select a good airfoil. Which makes up the part of drag called Parasitic drag. And it is not very dependant on the outline shape, but if you have a very special outline shape, let me know and ill use that in the calcs instead of assuming elliptical.

Also note, the other important drag component is Induced drag. This does not have a lot to do with the airfoil selection, but it does have a lot to do with aspect ratio, wing outline shape, and other forms of voodoo such as wingtip design. In my calcs I just consider the classic case of a elliptical wing, just to include the effect of reduced drag from increased aspect ratio. Feel free to get fancy with CFD or whatever to reduce induced drag some more after the profile is selected.

surfcowboy
64 posts
11 Sep 2020 10:47AM
Thumbs Up

Charlie over at Grey Paddleboards had a great Fusion360 tutorial on modeling wings. His site is down right now but I'll try to find it elsewhere. Keep an eye out for that.

There's this guy too. www.easy3dcomposites.com/pages/ebook

Hack on guys, I love this thread so much. It especially got good when the home made stuff started looking better than pro offerings. Haters gonna hate but even the manufacturers make prototypes so never be ashamed of your ugly quick prototypes. As was said, that's how we all move this forward.

surfcowboy
64 posts
11 Sep 2020 10:52AM
Thumbs Up

Also forgot to mention this. If you aren't 3D printing you can print those profiles on paper and cut out plywood templates. Screw/nail those into the ends of your foam piece and hotwire cut the profile. Then you can sand the tips and glass it. This works for flat wings and tails and you can put a curve in when you glass.

Mokuleia
47 posts
11 Sep 2020 11:50AM
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Select to expand quote
PrfctChaos said..

Regarding wing outline (view from the top basically). I usually stick to a elliptical area distribution (The classic theoretical optimum case). But keep in mind that even straight wings with a 40% taper is basically 99% a elliptical lift distribution as well, which is easy to fabricate, that is why planes have been using that plan shape for so long, instead of elliptical.


If you have access to a CNC I would say go for it and make you own molds. My CNC is still under construction but once done, my first attempt will be to route the mold in MDF and then vacuum laminate a single layer of fiber glass around it to protect it.


Select to expand quote
surfcowboy said..
Charlie over at Grey Paddleboards had a great Fusion360 tutorial on modeling wings. His site is down right now but I'll try to find it elsewhere. Keep an eye out for that.


I think this is the method I used. Basically, you create the wing outline and curvature first, then "intersect" both sets of curve to get the true curved outline of the wing and finally "sweep" the wing profile along this path (see below). This method is super simple, however it does not allow for variable AOI between the wing center and the tips. For this you need to create all the ribs individually and then connect them with a "sweep".

On a side note, it would be awesome if Seabreeze could create a DIY channel. Right now this thread is confined to SUP foiling, but I am sure many others in the kitefoil and windsurf foil channels would be interested to share their creations and ideas. Any idea how we do that? Should we make a petition or something?




Pacey
WA, 288 posts
11 Sep 2020 12:33PM
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PrfctChaos said..
Also note, the other important drag component is Induced drag. This does not have a lot to do with the airfoil selection, but it does have a lot to do with aspect ratio, wing outline shape, and other forms of voodoo such as wingtip design. In my calcs I just consider the classic case of a elliptical wing, just to include the effect of reduced drag from increased aspect ratio. Feel free to get fancy with CFD or whatever to reduce induced drag some more after the profile is selected.



I think focusing on aspect ratio is a bit deceptive, it's really overall span and then area that determine overall drag. For example for a given span, increasing the area for a given lift distribution will reduce the lift coefficient, and therefore the induced drag, but increase the parasitic drag, and vice-versa.

Within the range of aspect ratios you commonly see with foils, these trade-offs roughly balance one another i.e. for a given span you can increase or decrease the chord a fair bit without the overall drag changing much.

So the design process would ideally be to choose area based on the speed range you want, then select the maximum span you think feasible given the level of maneuverability you want. At the same time being aware that a high aspect foil will have a steeper lift slope, and as a result will be more sensitive in pitch, so its handling may be less forgiving.



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"DIY tail wings/ stabs" started by wicka