Author Topic: SURFFOILS Hydrofoil Design  (Read 3840 times)

PonoBill

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Re: SURFFOILS Hydrofoil Design
« Reply #60 on: March 14, 2017, 09:48:18 PM »
Pono, first thing, get better man.

Still seeing double, but the MRI says nothing deadly. Just a PIA. I'm going to check in with a neuro-ophthalmologist and see if there's something more aggressive I can do rather than just wait.  In the meantime it's a good excuse to work on GF2.

The old wings of GF1 should work well as the angle bits with a bit of modification. They're very strong.


Cut them off the joints rather than try to salvage the whole wing. I don't need it all.


Squared them up and trimmed them to the length I want. These will eventually have a 30 degree bend in them.


Here's the cross section of the wings and why they are so strong. An aluminum plate on the bottom with corrugations to make them stiff enough to resist straightening when I bagged them. Then a layer of 1/16 spruce ply. Then two layers of 6OZ carbon top and bottom, and a layer of 4oz S-glass for a sanding layer. A bit of bondo and some paint, Not as heavy as they sound, and I stood on these 22-inch-long sections bridged across two buckets--just to be sure I wasn't kidding myself.
« Last Edit: March 14, 2017, 09:55:43 PM by PonoBill »
Ponohouse is for sale: http://www.ponohouse.com
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

SURFFOILS

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Re: SURFFOILS Hydrofoil Design
« Reply #61 on: March 14, 2017, 09:55:24 PM »
Good idea to look for answers or get another opinion.

 Once you try the flat wood foil and see that it works you'll never waste time foiling foils again !

Admin

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Re: SURFFOILS Hydrofoil Design
« Reply #62 on: March 15, 2017, 03:47:31 AM »
Pono, first thing, get better man.

Still seeing double, but the MRI says nothing deadly. Just a PIA. I'm going to check in with a neuro-ophthalmologist and see if there's something more aggressive I can do rather than just wait.  In the meantime it's a good excuse to work on GF2.

The old wings of GF1 should work well as the angle bits with a bit of modification. They're very strong.


Cut them off the joints rather than try to salvage the whole wing. I don't need it all.


Squared them up and trimmed them to the length I want. These will eventually have a 30 degree bend in them.


Here's the cross section of the wings and why they are so strong. An aluminum plate on the bottom with corrugations to make them stiff enough to resist straightening when I bagged them. Then a layer of 1/16 spruce ply. Then two layers of 6OZ carbon top and bottom, and a layer of 4oz S-glass for a sanding layer. A bit of bondo and some paint, Not as heavy as they sound, and I stood on these 22-inch-long sections bridged across two buckets--just to be sure I wasn't kidding myself.

Looks great.  Please start a GF2 thread so we can track your progress and stay organized.

PonoBill

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Re: SURFFOILS Hydrofoil Design
« Reply #63 on: March 15, 2017, 10:26:37 AM »
Good idea to look for answers or get another opinion.

 Once you try the flat wood foil and see that it works you'll never waste time foiling foils again !

I get the flat foils for surfing and higher speeds, but for this project I need to lift at 4-5 MPH and manage up to perhaps 20 mph--Downwind SUP. Also needs to be low drag to get rolling. This will be surface penetrating with a shape like the boats above.

Admin--sure, makes sense.
Ponohouse is for sale: http://www.ponohouse.com
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

SURFFOILS

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Re: SURFFOILS Hydrofoil Design
« Reply #64 on: March 17, 2017, 01:46:12 AM »
Does anyone have any questions about foil design or construction, AOA, lift, profiles,arrangement of foils, riding, chords,leadingedge profiles, concepts, progression, future, submerged Vs surface piercing...?
 Whatever you like...
« Last Edit: March 17, 2017, 01:52:01 AM by SURFFOILS »

PonoBill

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Re: SURFFOILS Hydrofoil Design
« Reply #65 on: March 17, 2017, 09:08:14 AM »
Absolutely. I don't know how to calculate lift for a flat foil and how to determine and build in the right AOA.  How to size it, how to determine the best arrangement of the foil under the board. Have you used any of these designs in a board for standing?

I've read some papers on the high drag associated with surface piercing foils, but haven't experienced the kind of drag mentioned--any thoughts on that?

Do you foil the leading edge of your designs symmetrically?
Ponohouse is for sale: http://www.ponohouse.com
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

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Re: SURFFOILS Hydrofoil Design
« Reply #66 on: March 17, 2017, 12:53:44 PM »
Question-" I don't know how to calculate lift for a flat foil and how to determine and build in the right AOA."

Bill, I'm sure you've seen the lift equation lurking on various sites, but the best way is to test various sizes. The same area in different shapes gives different lift, including anhedral/dihedral and in my case where Ive split the planing area into different sections and that's totally different again. My advice, don't get caught up in the numbers. There's no substitute for getting wet.

AOA should be parrallel to the hull. When your hulls in the water you don't want the foil to be creating drag by trying to lift. And when you start to paddle into a wave you want the board and the hull working together not fighting to lift at different angles.
Remember as you take off on a wave you don't need to lift the AOA because the angle of the wave goes from flat to angling up so planing will occur naturally. Popping just makes it happen quicker.
« Last Edit: March 17, 2017, 01:24:49 PM by SURFFOILS »

SURFFOILS

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Re: SURFFOILS Hydrofoil Design
« Reply #67 on: March 17, 2017, 01:25:09 PM »
Question-". How to size it, how to determine the best arrangement of the foil under the board. Have you used any of these designs in a board for standing? "

Can you explain more about what you need for sizing  and  arrangement ? Do you mean individually or as a set ?

Even though I started riding foils prone, I moved to DK ( dropknee) and then standard shortboard surfing foils. Any foil will work on a longboard, sup or a pack of Oreos. Which would be interesting to see !
You mustve seen the pic I posted before ? It's the same foil used to shortboard that also is in the prone foiling videos on Vimeo and on several tow boards.

You know I don't use lateral foils anymore but once you change to long foils you'll stay with them. I had never seen long foils before, even if you Google longitudinal foils there's no precedence prior to mine in 2004.
 
« Last Edit: March 17, 2017, 01:35:46 PM by SURFFOILS »

PonoBill

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Re: SURFFOILS Hydrofoil Design
« Reply #68 on: March 17, 2017, 01:40:39 PM »
Question-" I don't know how to calculate lift for a flat foil and how to determine and build in the right AOA."

Bill, I'm sure you've seen the lift equation lurking on various sites, but the best way is to test various sizes. The same area in different shapes gives different lift, including anhedral/dihedral and in my case where Ive split the planing area into different sections and that's totally different again. My advice, don't get caught up in the numbers. There's no substitute for getting wet.

AOA should be parrallel to the hull. When your hulls in the water you don't want the foil to be creating drag by trying to lift. And when you start to paddle into a wave you want the board and the hull working together not fighting to lift at different angles.
Remember as you take off on a wave you don't need to lift the AOA because the angle of the wave goes from flat to angling up so planing will occur naturally. Popping just makes it happen quicker.

So here's where we diverge a bit. I'm trying to foil downwind. on unbroken swells. I'd like to do the wave stuff too, but first things first.

I know how to apply the formula for lift for a foil: Lift = velocity squared X area X foil coefficient. But everything I've looked at the includes AOA includes foil coefficient. The foil coefficient for a flat plane is 0, so that doesn't work. I suppose I could just toss in some small value, but having done that I come up with silly values--like 20,000+ square inches for area.

I doubt that long foils will work for the low speeds and non-critcal waves I'm trying to fly on. But I'll give it a go.
Ponohouse is for sale: http://www.ponohouse.com
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

Beasho

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Re: SURFFOILS Hydrofoil Design
« Reply #69 on: March 17, 2017, 01:42:46 PM »
I had never seen long foils before, even if you Google longitudinal foils there's no precedence prior to mine in 2004.

We got it.  We are with you.  But for the love of GOD your snapshots are like the infamous Patterson Gimlin Sasquatch photographs.

We need some updated material to work with.  A GoPro would do wonders.  Maybe I can find an extra one to send to you.  Maybe Clay will offer to come do a video shoot.
« Last Edit: March 17, 2017, 01:50:52 PM by Beasho »

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Re: SURFFOILS Hydrofoil Design
« Reply #70 on: March 17, 2017, 01:48:02 PM »
Question - "I've read some papers on the high drag associated with surface piercing foils, but haven't experienced the kind of drag mentioned--any thoughts on that?
Do you foil the leading edge of your designs symmetrically?"

With the lateral foils you're out on the shoulder looking for the fine line of speed, balance and lift. When you come back closer to the breaking wave, the most critical aspect is trying to off wash of all the lift and power that's under you. Closer to the break the water moves up the wave, the LIFT is massive, there's no shortage of lift, the inside foil in the tube pic above is 60 square inches and they are SP (surface piercing) foils.
 With a surfboard you're skimming on the surface, with a foil you're trapped inside the rising wave trying to drop not lift.
Yes I foil the LE symmetrically becuase it splits the amount of water deflection.

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Re: SURFFOILS Hydrofoil Design
« Reply #71 on: March 17, 2017, 01:55:53 PM »
Bill, For sure the DW will be different and I haven't done that but from what Ive seen if a lateral foil works then a long foil will too. The only exception would be very low speed, low power waves. Lateral foils have the advantage in low lift.

Beansho, I'd love to have a catalog of HD pics and videos but I only got a few pics for fun and that's not me riding. I had to ask a friend to ride while I took pics and this was his first wave of the foils.
 Believe it or not I have a GoPro, somewhere.
« Last Edit: March 17, 2017, 01:58:18 PM by SURFFOILS »

Beasho

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Re: SURFFOILS Hydrofoil Design
« Reply #72 on: March 17, 2017, 01:56:25 PM »
Pono: For starters can you work with these two graphs? 

The angle of attack is Very specific, second photo.  A cambered "Cessna" style airfoil at ZERO degrees has a Coefficient of lift of 0.3.  To get that from a symmetric foil takes 8 degrees. 

The caveat of the "Foils of the same family" is a bit vague BUT I am going to argue that given the density of WATER stalling is very difficult.  Yes it could happen at 3 mph, but outside of that we will not be as concerned with stalling as lowering the drag in the 10 - 20+ mph range.  Hence the reason to go with a symmetric foil.
« Last Edit: March 17, 2017, 01:59:19 PM by Beasho »

surfcowboy

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Re: SURFFOILS Hydrofoil Design
« Reply #73 on: March 18, 2017, 01:23:02 AM »
Pono, I think you're going to need an UGF (ugly geezer foil) to experiment with and bolt in some different size foils.

I'll try to get this thing in the water soon and start hacking away.

I'm trying to envision a test rig for your foil style. I may have to build some weird plywood and eps SUPP (standup paddle platform) to test your type of foil with so I can hack on it at the beach/marina. 2" of eps between some 1/4" ply would be a good test "board" for me.

PonoBill

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Re: SURFFOILS Hydrofoil Design
« Reply #74 on: March 18, 2017, 08:11:17 AM »
The formula used is the same as the one I'm using for my calculations. You can eliminate the density term (which is a lot more complex than you might expect) since we're in water and it's both invariant and resolves to about .9. The problem is that I can't find any value for lift coefficient for a flat plate other than 0.

Obviously, I could fake it, I was hoping there was something better defined than that.

A lateral foil will be easy to make and easy to experiment with. I'll make a holder and test one. Seems like there would be problems holding the AOA steady so the lift would be consistent, but I'll try it.
Ponohouse is for sale: http://www.ponohouse.com
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

 


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