How to build your own surfcraft hydrofoil.

This should be easy, very cheap and simple to build and result in a hydrofoil that fits on any shortboard, longboard or solid craft.

I’m glad you started this thread.

What I’m aiming at is a beginner foil for use in really small and mushy high tide summertime conditions. Conditions similar to what the trimboard guys ride, like Skip Frye and Tom Wegener. So as I see it the first step is to build a test mule with the intent to test different wings and masts.

So the first question I have is what these wings do the paddling characteristics of the board? If I start off with a 9ft longboard is the wing going to add to or detract from the effort it takes to get it going fast enough for the lift to kick in?

My second question goes to masts. I know that the SUPs and kayaks and some of the smaller sailboats use vertical masts, but in terms of fin design we use vertical double foiled surfaces to produce drive and directional stability at the expense of hold when we’re on rail, whereas we use cant for hold at the expense of drive. So the cant on a regular side fin in a shorboard cluster is 4* or 6* and a bonzer runner is 12+*.

So if the mast surface area, leading and trailing edges act like a fin at all, will using 2 of them mounted closer to the rails and with a little outboard cant add to the hold and drive when the board comes off of perpedicular? And if so, at what cost to the lift of the wing?

Forgive me for having basic questions but I’m literally starting at zero.

I’m interested in the mounting system, even though Surffoils has said on more than one occasion that it’s simple to make, I’m not wrapping my head around the best way to go about it.

A most interesting thread!

I think it’s best we split the system into 3 parts to discuss.
The board.
The foil.
The Struts, (The connection between board and foil.)

Please ask questions because everything is worth asking and discussing but some things wil be easier to experience than explain but it all works and I’ve consistently built and ridden foils for 11 years and a few earlier years of going over the theory with Terry Hendricks from here at Sways.

At the end you should have a safe and simple foil board that will get you foiling on small waves and hopefully whet your appetite for more speed. All included this should cost you between $0 and $50 based on the amount of stuff you should already have in the shaping shed.

I agree - there are several main considerations and a lot of ways to go wrong.

We could just use a cheapo Wavestorm to start with. I’m just not sure how well that length would paddle (with the wings) when trying to run down a 2ft swell.

The foil board has only a few functions quite different from a normal shortboard, it’s simply a paddling and standing platform and holds the foil.
The minimum is a short piece of ply or paipo that you can prone, DK or stand on. The practical maximum is a longboard around 8 foot. As the board gets longer it’s nose weight starts to impact on balance and manouverability.
it’s completely possible to use any shortboard as long as you’re already confident paddling on it so that’s the cheapest way to go.
If you’re in a mood to do a custom board I think a Simmons-esque board with less length and more width and thickness will be the most suitable. A longboard is fine but by keeping the length down and volume compact it’s just going to be easier to ride.
Overall somewhere between 6 to 8 ft or any shortboard / funboard will do perfectly well.
There’s no need to get hung up on finding the perfect board because you’ll soon obsess over the foil more than anything else.

Here’s where some foil boards have gone and it’s pretty much perfect as a foilboard with the Simmons influence and nothing extra.

Sounds like a potential marriage made in heaven for one of my 8ft McCoy Nuggets…one of them had an unfortunate encounter with the rocks at Lennox, a good candidate for reinforcing the bottom while filling the dings. Could be good for kite-foiling too, I guess.

I have a 7’8" displacement hull that catches/paddles well but doesn’t ride how I want. That’s going to be my foil donor board. I’m stoked for pictures!

I have a beater 6-10 retro egg I built 15 years ago that will work for a mule.

This is going to be good. I’m in.

All the best

Pulling up a seat!

thanks, surffoils. Looking forward to making one.

Gdaddy, let’s do this!

I’ll do one with you and show pics.
So here’s my mule, drone, foil-board. 5’10" poly, single concave square tail, not that any of that makes any difference. But it’s good to recycle.

Now find the flattest area in the tail rocker.
I’ve taped an area that’s from 15-29 inches from the tail. It also falls within my ususal stance.
What numbers did you guys get ?



This thing is a singlefin so the rocker is pretty flat (4"N, 2"T on a 6-10 length) and we normally surf these pretty far forward - the trailing edge of the fin is usually at 9" or so - that’s way further forward than a thruster. So I ended up with 24" and 42". Should I move it back?

I guess what I’m asking is if I normally use an 18" stance on a singlefin (more hula, less pumping) do I want to put the wings fore and aft of that or right under it? We normally move forward a step to trim and move back a step to turn. I’m trying to suss out the balance and leverage compromise.

Surffoils, what are your thoughts on having a fuselage? I saw that the foil companies build them with holes running fore/aft for wing adjustment. I imagine I’m going to want to play w the placement, especially initially.

Thanks again for your time and sharing your knowledge.

Gdaddy, to answer your questions.

"So the first question I have is what these wings do the paddling characteristics of the board? If I start off with a 9ft longboard is the wing going to add to or detract from the effort it takes to get it going fast enough for the lift to kick in? "

Gdaddy this is why weve chosen this flat section and mount the foil directly on top.
The foil will be parallel to the hull and there’s almost no paddling difference with the foil. Your foil is going to be light and tight under your board and a lot unlike the commercial ones that are up to 1.5 inches thick and 3 feet away creating drag.

Your second question about cant I’ve never looked into but let’s get the parts together and then see if can’t could be incorporated.

Once you lift up on a foil its all yours to control from the air, so there’s no stepping fore or aft. . Putting the foil in this flat area is for flow, where you stand will be directly over the foil. Those numbers are perfect fo that board, now put a mark directly in the middle of that area. For you that’s at 33 inches up.
so you’ve found a mark in the middle of that flattest section on the board and it moves with the board length so everyone’s numbers are going to be different by a few inches.

Bookmarking this one!!! Onto the ever growing to do list!!!

Ghostshaper, I’ve designed out the fuselage but this foil I’m showing you will be infinitely variable.