Hydrofoil Wakesurfer

Ok, so I'm ready to start this project. I am hoping that it will actually lift the board above the water and not destroy the board during the start.

Preliminary discussion is here.

Following Brett's recommendations, I'm going with a foil that is in the area of 200 sq in. I roughed out the required dimensions, but I'll change the shape to be more in line with the finished shape that Brett has used.

Awesome! I forgot about this, can't wait to see how it turns out!

Me too! I'm hoping that it stays together long enough to get above the water.

Quick cut out, of the foil and three supports.

Applying hydrodynamics I can't imagine that rounding the corners on 3/4" ply will help much, but it can't hurt.

I've also marked the location of the struts include the marks for the pilot holes.

I used a 3/32 bit for the pilot holes.

No pictures, but what I did was drill all the pilot holes through the foil. Then held each strut up and aligned it and drilled one pilot through the foil and into the strut. Next I screwed the strut down with a 2" wood screw and did the second hole for that strut.

Quick visual of what the foil and struts look like. I still need to hit the leading edge with the belt sander.

Cap strips that will "hopefully" spread the load from the struts to the board.

thats so cool that you are making that ...... i know a guy who offered me to buy his sit and ski foil thing for $50 ...... i cant get ahold of him untill may .... maybe those parts could be put to good use

Thanks Frank, I'd love to get the measurements off the foil part of it, but I think the rest is too heavy for our purposes. The foil boys strap in so that the 50 pound sharp edged foil doesn't hit them if they fall! If I can get this prototype to work, I'll have to fashion one out of foam and some carbon.

I decided to use an old school Calibrated that has been damaged. This board has a divinycell core (I think H100), which is closed cell, so if I get some water intrusion, I'll be safe.

I still need to paint the foil, but I want to laminate it to the board itself to given me some extra strength.

So...foil attached, leading edges "rounded" and ready for glass and paint.

did you foil the supports?

Yeah some, not much though. The really need to be 1/8" aluminum.

I see Judy is taking Wolfy on an evening walk

The dogs always follow Judy out to the back pasture - looking for grain or some type of snack.

First carbon patches to help keep it all together.

ive got lots of 1/4" aluminum plate ..... 48" x 48" ..... just tell me what you need if you want to use any of it

Hey Frank,

Do you have anyway to weld it? The struts really beg to be 3" x 8" with facings at each end set at right angles - maybe 2" x 5".

i used to have a tig welder but not anymore ..... i think a friend has one at his house ...... if he doesnt i have access to any welding equipment ...... just email me a drawing ..... i think i know how you want it but lets amke sure

Jeff, on the standoffs for the foil you'll want to shape them airfoil shaped. Especially the trailing edges need a significant taper.
There will be significant drag with the smoothed flat shape you currently have. Even if you rasp the back to a taper over the stern 2/3 of the standoff.
A full airfoil shape has only 1/10 the drag of a tube the same diameter.

Thanks Art. I think for this first test, I just want to see if we can get it to actually lift. If it's function at that, then I need to do the job right Carbon everywhere!

You get good enough with that carbon and you might start thinking you need a tuned Honda or Scion.

Yes! I want a tuner! With a CF hood!

Frank, I know you'll marvel at my drawing skills, no doubt, wondering how it is that I'm not an engineer! 3" x 5" feet on a 3" x 8" strut. Can you manage that for me 'bro?

i can cut that up tomorrow and maybe have it welded by wednesday ...... ill also give you a piece of the plate big enough for your foil if you want ...... youll be able to file or wetsand the edges however you want them ..... ill even run them up to you with the nano stuff if you can help me out with what i asked james tonight and i could get that at the same time

Thanks Frank! I just sent you an email.

I love my Honda. Yes. That is real CF too.



Mario-

Sweet! Carbon is a great look.

Speaking of which, I ran out of Carbon scraps and had to use 2 layers of 6 oz on the leading and trailing edges.

Paint it white!

Ready!

Water test this weekend?

Yes! We're heading out Sunday, hopefully, I'll be able to report back that the thing generated some lift!

It floats! Check how high the tail is out of the water!!! Something to consider for Hydro #2, if I make that out of aluminum. The wood has some positive bouyancy and the tail is a good 1" higher than normal.

We tested it today! Great fun! We decided to test it out at the end of an 80 foot rope, I was concerned that the foil would separate from the board sending James into the swimdeck. Which, amazingly enough, didn't seem fun to James.

Lots for float! James said it felt weird.

The foil I shaped wasn't really foiled very well, plus I mounted it parellel to the bottom of the board. The foil was 200 sq in. Those three things prevented it from generating lift at 10 mph...but it didn't come apart!

However! Somewhere between 14 and 15, it generated lift!

A few more - the speed was too fast to wakesurf and the orientation of the foil needs to be changed to allow the board to ride flat, but I'm sure it's doable to free surf behind the boat with one.

Nice! Cool to see that it did work. Look like yall had some fun with it

thats so cool .... congrats on it working ..... everythings cut but the welding is coming slow at the moment

When you get rid of some drag and run the foil with a better shape it will lift a lot more but you may still need more surface area if you have to travel 15 to get it up. The lift you're getting at 15 is more than double that at 10.5.
When the next generation you might want to build the standoffs so you could shift the foil forward or back to find the best balance point while riding.
Looks like a fun project Jeff.

Thanks Art! My goal is to be able to get adequate lift to allow the board to be freesurfed at around 10 mph. Once the foil comes out of the water, it loses speed drastically. The standoff's at a 6" depth made it really hard to control the depth of the foil - just a tad back and the foil popped out of the water. Good point on the standoff location. I'm not sure about the placement of the standoff's lengthwise on the board. It "seems" like they need to be moved forward on the board, but might just be the crappy shape of my foil.

I am not sure that what we had yesterday was planing surface not lifting surface. I think the board planed on the bottom of the foil and not lifted from the foil. Just my observation.

Hey BK, the lift was generated at around 15 - when we were above that, it quickly went to the surface and it's just skimming across the top The minimal depth of the "standoff's" or struts make the transition short! There is a point though, where you can see the lift. I think as we talked yesterday, it needs a different orientation of the foil - upwards - the front standoff shorter in relation to the rear standoffs - a more efficient foil and then some reduction in the drag of the standoff's.

Question,

When you are creating your foil are you designing the foil portion with the same concept as an airplane wing ie. basically flat on the bottom and a thick curve at the front tapering to a point at the back? I am assuming the same principles apply in the water as they do in the air?

Well...I should have, but no I didn't do a good job, desoto. I foiled it a bit, but mostly it was just a slab of 9 ply plywood. As Dennis pointed out on the boat, it needs to be shaped more like an airplane wing - and from what I can tell, with that "lump" on the top of the foil, it causes the water to move faster and, as such, creates less resistance thereby allow the lift. My foil had some of that, but not as much as needs to be done. I didn't start my taper at the tail until just a few inches from the end.

The planned wakesurf hydrofoil redux will be a bit larger than 200 sq in, will have an effect foil and will have a slight incline - for want of a better term - where the foil is pointed up so that it has a tendency to ummmm climb?