Diy sup foil

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flexi foils is what we need! shaped with wash in at the tips for extra lift in the pump, then when your weight comes back on it will flex to have wash out.
this was the idea with my whale tail foil but i may have built it too stiff, stand by for results!

[PonoBill]

The geezer foil flexes like crazy. Trust me, that's not a feature. Some flex might be useful, but it adds some random variation in lift and lift vectors to a system that's already marginally stable.

One option that I haven't seen any company explore is laddered foils. It's common in high-speed boats--essentially a biplane wing. When the top foil broaches, the lower foil still provides some lift, which prevents crashing. In the middle of the speed range the lift isn't enough to sustain the top foil out of the water, so the foil settles back. At the upper end of the speed range the upper foil stays out of the water. This has the added effect of increasing the surface area available for lift without increasing span. You could have two high aspect wings, and even stagger them a little to gain some pitch stability. Making the top foil relatively small provides breaching control without huge lift variations. Just enough to settle the foil and extend the useful speed range.

[supuk]

I think the hole pumping thing could be really exploited and I intend to try a few ideas when I have a new working model. The wash in and out is a interesting idea but  you do need enuff stiffness for control.

I'm prity sure the curved foils you see on a lot of boats is for self regulating lift. The other one I have seen is called the crazy foil and it has the front foil sitting a lot lower than the rear with the idea that if the rear comes out you still have some lift from the front

[surfcowboy]

Have you guys noticed that surffoils over on Swaylocks has woken up and is discussing his foils again. Pono, he's done flat foils more like you were working on for years now. Did a boogie board that looked crazy fun. Mostly bent aluminum. It's  wild to see that strips of flat metal can lift like that.

Tired foils makes a ton of sense. Even a little wing up above the main one would boost you up.

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anything piercing the surface suffers a drag penalty, especially an adverse pressure inducing foil!

[PonoBill]

True, but the stability, self-regulation, and crash-proofing of surface piercing foils is probably worth the penalty. And the mast of a submerged foil is generally faired as a symmetric foil, and has roughly the same drag as one of the foil legs.

[supuk]

Have you guys noticed that surffoils over on Swaylocks has woken up and is discussing his foils again. Pono, he's done flat foils more like you were working on for years now. Did a boogie board that looked crazy fun. Mostly bent aluminum. It's  wild to see that strips of flat metal can lift like that.

Tired foils makes a ton of sense. Even a little wing up above the main one would boost you up.

been cheating to him off line for a while about things and about the open ocean stuff he has been experimenting for year on the wave stuff.

[supuk]

trying to go about trying to draw the mast molds in a different way

[dns]

It's probably worth noting that every single racing sailboat is using surface piercing foils now. Even the monohulls are going down the same road. The SUP and kitefoil guys are backyard tinkerers compared to the millions that are spent developing and optimizing the AC72 and IMOCA 60.

We should really be copying those curved foils and figuring out how to adapt them to SUP boards rather than following the kitefoil lead.

[supuk]

it definitely something I'm going to play with when i figure this hole cad thing out and cut moulds easily, i should be able to speak to someone involved in the vendee globe boats about them to get there view.

[surfcowboy]

DNS, Pono is ahead on that. Check the Geezer Foil thread. I just don't know how those would surf but for flat and downwind I'll be they are superior.

In a more hollow wave I'm not sure how you'd manage the three or four points of contact.

[dns]

You're right, I definitely don't think multiple points of contact is the answer. I was mostly referencing how the curved, surface piercing foils are self regulating with regards to lift. As the foil rises more of the wing is out of the water, reducing lift. re: PonoBill's post.

[blackeye]

don't know much about this but saw it on sailing anarchy... looks interesting.

https://www.facebook.com/SEAir.gravity/?fref=ts

[surfcowboy]

DNS, totally agree. Progressive foils make sense. Don't get Pono started, he'll have a sensor on there and servos to dial the aspect ratio up and down.

[yugi]

I think small very tucked in curved (C) lifting foils could be cool up front on a DW board. Not enough to completely lift you, not enough to be a drag, just enough to assist the board to get on a plane. Ideally very shallow V so that they no longer interfere once the board is planing, retaining classic planing and turning feel. Should be pretty stabilising while in the water. Win win.

Just earlier, way earlier, planing by foil assistance. That’s all.

Great foil reference (in french)
   https://foils.wordpress.com/tag/alinghi/
pdf downloadable english translation here
   http://proafile.com/multihull-boats/article/the-foil-alphabet