Diy sup foil

[Beasho]

more negative incidence on the back foil= more stable in just about every aspect, even turning.

Is there anything else MANMADE that is designed like these "Surf Foils?"

I ask because what we are essentially doing is putting a Traditional Fuselage Based Airplane (less vertical stabilizer) underwater.

Most other Hydrofoil designs rely on the Boat for the fuselage and only extend Struts underwater for the Main Lifting wing and Horizontal Stabilizer.

This leaves us with the Shortest Wheelbase ever attempted.  The only thing more extreme would be a single flying wing, and that might be crazy/interesting/eventually possible . . .

The Short wheelbase allows for the Rocking moment around the 'Pitch' axis that people love to use to continue flying. 

My question is:  Why the Negative incidence on the tail?

I realize it works, empirically, but WHY WHY WHY?

PS: Great Demonstration Video SUPUK.  My comments was sparked by the fact that SUPUK's design CLEARLY WORKS.

[Surfside]

Hi folks. Great thread! I am concerned with possible injury from the wing tips and saw this video with a box wing. What do you think? BTW....this is some awesome work!

[supuk]

the reversed rear foil is basically working in the same way a airplane uses a positive incidence between the front and rear wings. In a plane adding positive incidence along with changing the centre of gravity makes them more stable in pitch, this is tested with a dive test and making sure the plane slowly pulls out without any input from the pilot. There is no reason you couldn't use a conventional rear foil set up but what it would be like I'm not sure, I'm guessing there is a reason most are like this I will however try flipping the one on my takuma over as it is fairly easy to do. 

Back out on the new board today and this time experimenting with a ventral setup. I think it was a little to small to really tell the difference so I will make myself something a little larger over the weekend to try.

As far as the board goes I'm tempted to take it back into the work shop and add some tail rocker, as I though the wide tail helps get the waves but it does get a bit sticky when you want to pump.

[Newps]

Hi folks. Great thread! I am concerned with possible injury from the wing tips and saw this video with a box wing. What do you think? BTW....this is some awesome work!

That's an incredible build.  So many trick details incorporated into it.  Thanks for sharing.

[PonoBill]

Got dragged around by Dave Kalama on the GoFoil today--a real eye opener. I need to digest and process all the thoughts running around in my head. I would have had an easier time of it if my boardshorts stayed up. Hard to get your back foot into the strap when you shorts are tieing your feet together.

[PonoBill]

My question is:  Why the Negative incidence on the tail?

I realize it works, empirically, but WHY WHY WHY?

PS: Great Demonstration Video SUPUK.  My comments was sparked by the fact that SUPUK's design CLEARLY WORKS.

Negative feedback loop. If you had positive incidence the foil would respond to rear foot pressure by running away--the stabilizer would pull the tail down.

[surfcowboy]

Windwake, if you've been following most of the guys on this thread who are foiling I think you'll see that the great foil apocalypse of 2017 isn't really happening.

I agree that they seem dangerous but I'm not hearing much and if you're watching the wrecks, it's not looking any more dangerous than a long board fin when your board upends in a close out. I've become way more scared of that than foils. The wing in the water does a pretty good job of being a drag anchor too.

That box foil is cool, but man, what would that cost? Seems crazy hard to build.

[supuk]

There are defiantly dangers there but there are ways to minanize them when learning. Specific sup foils are extremely stable compared to kite foils or flat wing style foils like I first built. Learning the basics on a short 400mm mast stops the big and dangerous crashes when learning and there is also lots of info out there now on what to do and what not to do. A year ago when I started ridding my first one when kai video had only just cone out and the go foil was not available was a very different story.

The main thing is still learn how to crash and get away from the foil as soon as it starts to go wrong.

[supuk]

Trying adding a little more tail rocker the quick way, cut the glass with the multi tool then hot wire it back.

[Area 10]

That's funny. You'd be a useful person to have in a cheese factory

[supuk]

So while the board dries I thought I would have a play making a diy foot hook. I have been finding foot position so critical literally a inch off the correct spot and it can throw you all out. Up until now I have been using a tail kick and ridges in the deck pad to guide me on the center line but now also looking for something for the front foot and while I want to stop my foot moving I still want to keep things nice and unristricted. The price of a kite foot hook style strap was something like $80 so thought better to that and 30 mins later with a donor windsurf strap and a strip of Ali and some eva I have a nice little thing to test, just got to get the wife to  sew the end up nice, all for the sum of about $2 of scraps

[supuk]

Quick jobs to do on a wet weekend

Modify tail✅

Adjustable kick pad ✅

Foot hook ✅

Done

[PonoBill]

Very cool, and probably ideal for the application. I like the raised centerline in the kick pad.

[supuk]

Very cool, and probably ideal for the application. I like the raised centerline in the kick pad.

The raised center line is the most important stupidly I was in a rush when I did this board and forgot to put it under the main pad but there you go. Having your foot bang on the center every time helps a huge amount!

[Surfside]

Thanks for the replies and input. Going to start creating a foil and I was going to use an old windsurf fin for the mast and divinycell foam for the core of the forward wing. This will be my third glass related project. 1st was a surf board and then a carbon/innegra SUP...always an adventure. All input is appreciated