It should go without saying but I’d like to also thank you sharing with us. I’m taking EVERYTHING you’re saying very seriously and giving the info and your efforts the respect it’s due. It’s apparent that you also have the undivided attention of other regulars here.
As for the angled struts that’s a possibility we can explore later, after we’ve sussed out the other big variables.
Without knowing much about the subject it seems intuitive that maintaining balance and control will be easier with a “tight” gap between wing and board vs an elevated gap. It strikes me as being similar to learning how to walk on stilts - easier on shorter stilts and harder on longer ones that will be more sensitive to control inputs.
Thank you Gdaddy, I’m very happy to share too.
Yes keeping the foil closer to the board reduces the weight and paddling drag but increases the safety and response time when riding.
Some other foils have a single lifting foil with the trailing foil digging in to keep a +Ve AOA and then the rider stands in front to balance the digging in of the rear foil. Does that sound less than effective ?
The foil shape is up to 1.5 inches thick and is on a 3 foot mast which gives excellent low power lift but drags due to the volume, distance and weight ( up to 11 lbs for some retail foils ) and costs $1500 for the foil alone.
I guarantee we can make an improvement on most of that.
You’ve ended up with a single mark on the stringer in the middle of your flat area.
Now draw a parrallel line on both sides of the stringer. It has to be exactly 4 inches away from the stringer and for 12 inches Up from the mark and 12 inches Down from the mark.
Just 2 lines 24 inches long, but do it carefully please.
Any problems or questions ?? because that’s it for the board until we install the foil.
If i were to shape a board just for this. Most likely a simmons type shape with 0 tail rocker, as i have heard this is best since the board is just a paddling vessel until the foil engages. Would my marks and measurements be the same?
On a McCoy 8ft Nugget, there is a small flat spot on the bottom, but it is located around the centre of the board, not in the tail area. But the board is surfed from the tail.
I’m not sure how to find the right spot for the centre of those parallel lines, yet.
Deez, If you have a very flat tail rocker, then position the foil anywhere along the flattest part that suits your regular stance. If its all equally flat then there’s no specific flat section to align the foil. For a flat tail rocker put a mark in the middle of your regular stance on this board. So even if you made a specific foil board, the marks would be about the same because the dynamics of surfing would stay the same…You’ll always need more nose than tail and need to stand nearer the tail.
For boards like MrMik is saying that has a continuous rocker and a smaller defined flat area nearer the middle ( usually on single fin boards) then use the smaller flat spot as the front limit and draw the lines from that point back towards the tail.
The McCoys have a great advantage of being thick and squat.
My best advice is that if you run into a problem it’s just easier to pick another board and move on.
You know, the comparison that comes to mind with the single mast vs multi-masts is the technical difficulty of riding a unicycle vs a bicycle or tri-cycle. Of controlling a singlefin on a steep drop vs a twin or thruster. Only exaggerated when using a long mast.
Robin Mair uses the term “center of effort” with his fin designs, which is kind of self-explanatory. A single fin array has a different center of effort that a twin or thruster.
And speaking of masts, they’re basically fins or keels as far as directional stability goes, right? So, no need for additional fins.
I too want to thank Surffoils for sharing with us. If I go through with this project (hopefully) I feel I will need to put an “inspired by Surffoils” label somewhere on the thing. Or maybe Surffoils™
Edit: I just thought of a dumb question. Do you need to have a fin in the actual board once you’re out in the water? Does that help with paddling or is it not needed?
It’s interesting that you both mention fins at the same time, I went through the same process.
I put fins on the board, then fins on the foil and now no fins with foils for years.
It’s true what you say that the mast / struts act like a wavegrinder fin anyway and adding more fins didn’t add to the control.
But add them as you wish just to see. They don’t seem to give or take much but they are another thing to bother about and I prefer the simpler version.
I thought about the fin issue and the first thing that came to mind was what happens when you’re “up” - particularly at an angle - and a fin catches when you’re least expecting it. That can’t be good.
So we’ve done the Board, and you’ve got two lines 8 inches apart, doesn’t sound like much but it’s a start.
If you’re ready lets move on to Foils ?
This is where a bit of creativity comes into play.
The Foil, or Foils.
You know that the foil lifts by using both Bernoullian and Newtonian theories, it’s both the shape of the foil and the wave itself that creates lift. The theory is endless and a lot of the aero/ hydrodynamics don’t apply to a spinning wave.
But the basics are that The dims of a foil dictate it’s balance, so a long foil is more stable front to back.
Much like a surfboard, a wider front is more stable at the front so foil design is similar in that way. Reduce the width, you get less lift and balance… So an easy foil to ride is going to be a wide long foil.
Heres a few of mine over the years.
Do you have any ideas of what type of foil shape you want to ride ?
Is weight of the board an issue?
The first board i ever made was a timber veneer comp sand mini sim kinda thing.
A touch over 5’2" and 21.5" wide, bulk volume and a single concave all the way through.
it has two layers of 2mm veneer on the deck and 2.7mm hoop pine on the bottom.
it may be good due to its low rocker and good paddle, and its structural strength.
BUT its about 4kg just epoxy painted over the veneer not glass cloth?
So around 8.5 pounds…
Any thoughts?
I’m going to focus on Gdaddy wanting a foil for marginal conditions but it’s all useful knowledge.
Generally I can stand on a foil that’s 23 inches long, but for a beginner let’s take that out to maybe 26. I gave the first foilboard to a guy who stood up instantly but he has martial arts training and doesn’t ride conventional craft. That foil was 23 X 16.
Why is the width only 16 " ? Because like a bike or a surfboard, it gains balance as it moves forward.
So now we’ve got a foil area 26 long by 16 wide. And I just happen to have drawn out a template for you. It’s 26 x 16, @ 350 sq inches., so long and wide enough for easy balance and @350 sq in it will lift in the slightest of waves. In fact probably too easy, so I’m expecting that as feedback.
Have a look at these other foils I’ve ridden extensively…
The black bullet shape is 23 x 13 @246 sq in. It lifts quickly and the minimal width and tapered nose allows for easy rail to rail transitions, the wide square tail keeps the tail lifting for drive. It’s great for small waves. Having a tapered template is just what you want Monkstar.
The fenestrated foil or donut foil is 26 x 14 @ 232 sq in. It’s a medium wave foil where I’ve added length to the rail but reduced the overall area because there’s no shortage of lift when you’re on OH waves.
Foil design is about finessing the foil to the wave, you’re chasing control not lift.
I had been considering your earlier comments on longer foils vs wider as well as pondering the difficulties of managing a twitchy fore/aft balance. Since I’m looking for a longboard style trim/glide this could be right up my alley.
I also like the idea that it would take more roll for a narrower wing to break the surface than a wider one. And I had been sweating the prospects of trying to paddle the board without smacking the wing on my downstroke so these dimensions and placement don’t put my anywhere near that, either.
So I’m all over the basic design. I guess my next step is to get some ply and get to fabricating. I’m slow as fark so that’s going to take a while. What kind of thickness should I be looking for?
You saw all the foils I made before and they are made of Aluminium, polycarbonate, polypropylene, fibreglass and resin, lots of different cloths, corflute, solid pine, laminated veneer and even 3 ply. Which is my favourite Foil material.
So grab any piece of material that’s big enough and draw that template on. But also draw a clear centreline on both sides of the foil.
And draw a line on both sides of the centreline that’s 4 inches out on both sides. Just like the lines on the board you did before.
