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Windfoil alternative (maybe)

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Created by mark62 8 months ago, 19 May 2017
mark62
WA, 199 posts
19 May 2017 5:32PM
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Just read about a new fin from Virus fins. The describe it as mid-way between a conventional fin and a windfoil. Lots of fin lift, giving a ride slightly above the water line so feels like a windfoil, but not as extreme. Full planing in 6 knots and easy gybing.
They say its perfectly safe to use on regular boards, no special fin box. Virus say it will be ready in a few weeks and will be much cheaper than a full wind foil.


www.facebook.com/theviruscarbon/photos/a.1707107396242761.1073741828.1706278012992366/1916607861959379/?type=3&theater


Imax1
VIC, 952 posts
19 May 2017 8:44PM
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This could be possibly friggin awesome.
Imagine a fin with huge lift in light wind and still having that skimming feeling and
Thats it ,I'm pulling out the tools
If I have an adjustable angle for the foil so that you get just enough lift to plane earlier in light wind rather than start flying...............mmmmmmm ?
scrounging tinkering garage noise

Imax1
VIC, 952 posts
19 May 2017 9:45PM
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I wonder if the foil people will tell me the angle of attack their foils have ?
i have the answer,......
go home or I'll call the cops

Imax1
VIC, 952 posts
19 May 2017 10:38PM
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Ok I'm going to sneak into a windsurf shop with a ruler , protractor and a camera,
stay tuned........
or I could buy the virus fin.
or develop Imax mk1

mark62
WA, 199 posts
20 May 2017 8:04AM
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Apparently it's 380 euros, expensive compared to a regular fin, but cheaper than a windfoil......

col5555
WA, 264 posts
20 May 2017 8:37AM
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Looks like they beat me to it and I can stop working on this concept




waricle
QLD, 538 posts
21 May 2017 9:59AM
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Don't some of the other foil manufacturers sell their foil parts separately?
I shouldn't be too hard to buy the wingy thingy and fit it to a fin....

boardsurfr
376 posts
21 May 2017 8:31AM
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Now add a couple smaller and thinner foils further down the fin/mast. As the wind increases, the board gets higher out of the water, leaving only the 2 lower smaller foils in the water, and finally just the lowest foils. Resistance decreases, speed increases. You'll have a system that planes in 6 knots, but with much higher top speed.

For simplicity, the three (or 4 or 5?) foils could be the same size. Now that so many companies have jumped onto the foil wagon, maybe someone will develop this to stand out from the crowd.

Imax1
VIC, 952 posts
21 May 2017 5:28PM
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I'm going to try to make something like this.
I have a cut down Drake formula fin to 600mm that didn't work , horribly stiff and strong , just yuk.
Ill use this for the main fin.
I also have a 400mm Drake shallow water fin that I don't use. I'll modify this for the foil.
I can make things fit and strong and angle adjustable.
This is where I need help , I'm thinking like col5555 idea.
1 , should the wing be a fin shape ( same foil top and bottom ), or more like an aeroplane wing creating lift ?
Im not trying to fly but create some lift to get even lighter wind planing. I'm worried the thing will create more drag than it's worth.
and 2 , how far down the fin should I mount this ?
Ill be using this on an old 90cm wide Starboard GO
Ill be in mad scientist mode tomorrow ,
Help

mark62
WA, 199 posts
21 May 2017 7:47PM
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I reckon the main key here, is to mount the wing nearer the fin base, not the fin tip. If the wing is too near the tip, it starts to step into full windfoil territory.

Near the base would give you that extra lift, but extreme lift. Plus, its less likely to break your fin box, have easier control........

Having said that, I am just guessing!!!

joe windsurf
1212 posts
21 May 2017 9:56PM
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In August 2016 in a fin discussion on iwindsurf U2U2U2 posted this picture:

forceten
241 posts
22 May 2017 12:19AM
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Yea I also made this..
[URL=.html] [/URL]

RichardG
WA, 1095 posts
22 May 2017 12:54AM
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www.cheynehoran.com.au/starfin.html


Invented by Cheyne Horan and Ben Lexcen.

Mastbender
1546 posts
22 May 2017 1:38AM
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Even though I don't want one, I like all those fins, we could use many of those where I sail. We have a lot of seaweed, kelp, and eel grass in my area, and those things work really well for cleaning out all that stuff from the water, leaving it clean for us who prefer normally design fins. Foils also, bring 'em on!

waricle
QLD, 538 posts
22 May 2017 7:26AM
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How well did the above versions work?

olskool
QLD, 421 posts
22 May 2017 7:49AM
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Late 80s early 90s i had the green fin on right on a Bombora for a short stint. Not a fast fin or board. Fin may have been better on surfboards. (Lower speed). Fin was grippy though, stabilised board through choppy water.

AusMoz
QLD, 894 posts
22 May 2017 9:17AM
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Select to expand quote
olskool said..
Late 80s early 90s i had the green fin on right on a Bombora for a short stint. Not a fast fin or board. Fin may have been better on surfboards. (Lower speed). Fin was grippy though, stabilised board through choppy water.



TheVirus states:

It's been a while... but we were working on something totally new that is going to change your windsurfing experience. We are at the very end of testing and developing performance to the next level. Fully demountable wing will make it easy to pack and change sizes to smaller/bigger one.

Early planning and jibing hasn't been that easy ever before ! More surface underneath the water let you "foil..." easily through choppy water. You can forget about catching a spin out, it won't happen again :)

You will have this kind of "foil" feeling which is pretty special but you can still push the board as much as you want and it will fit your current equipment, no doubts about that.

No flex option because all the lift that normally comes from stiffness, now is delivered from the wing. Basically it's working like an airplane wing with winglets. Winglets are set downwards, thats why all the air bubbles that are creating under the board and cause spin outs are now gone



My Opinion


It was hard enough to come to terms with using a fin over 40cm long. Then foiling came along - stuff that! My local sailing area cant support a foil unless I'm in open water.

To be honest I hate sailing and thinking "Will my fin scrape the bottom"

How ever I can be persuaded by Viruscarbon (or Col5555) fins if it works. We all seen the 80's and 90's wing fins and knew they were nothing more than a novelty idea with not much to offer for windsurfing except future ideas (recycling the past).

Hopefully we are not seeing a fin that is 50-60 cm long being used on a 125 litre board (Tabou Rocket or similar).

seanhogan
2689 posts
24 May 2017 12:54PM
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From Virus :

So as promised we did some testing here in Costa Brava. We couldn't ask for more experienced windsurfer than Steve Allen who was testing it competing with guys on normal foils. I have to say we didn't expect he will do that good. He managed to qualify to both winners finals ! :) Congrats to Steve Allen and thank you for your input ! :) Tomorrow I will post a little interview with Steve and ask about first impression, stay tuned


Imax1
VIC, 952 posts
24 May 2017 3:20PM
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It will be interesting to see if it actually foils or just creates lift . Both would be great.
Looking forward to his review with great anticipation

Sputnik11
VIC, 829 posts
24 May 2017 8:39PM
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Select to expand quote
Imax1 said..
It will be interesting to see if it actually foils or just creates lift . Both would be great.
Looking forward to his review with great anticipation


Have to be just lift right? Not deep enough to fully foil.

Parked
NSW, 169 posts
24 May 2017 9:39PM
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Select to expand quote
Sputnik11 said..

Imax1 said..
It will be interesting to see if it actually foils or just creates lift . Both would be great.
Looking forward to his review with great anticipation



Have to be just lift right? Not deep enough to fully foil.


Isn't the purpose of the longer foil mast so that the foil wings and fuselage remain submerged and the board doesn't hit or touch down on the chop or the foil cavitation? i.e. giving almost 1 metre of chop clearance. Once the board over comes the resistance of the attachment to the water surface, the board gains elevation and minimal drag = the submerged foil component only.

boardsurfr
376 posts
24 May 2017 9:35PM
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Select to expand quote
seanhogan said..
From Virus :

So as promised we did some testing here in Costa Brava. We couldn't ask for more experienced windsurfer than Steve Allen who was testing it competing with guys on normal foils. I have to say we didn't expect he will do that good. He managed to qualify to both winners finals !


"He managed to qualify to both winners finals !" would be quite impressive for a slalom race, where the top 8 of 30 or more racers are in the finals, so racers have to be in the top half of the field for 4 or more races. It's a bit less impressive in the foil races, where it seems they have 12 boards in the finals, and only 22 starters. The PWA result page at nor.pwaworldtour.com/Foil_results_costa_brava_2017.htm shows Steve Allen placing 12th and 10th in first 2 foil races, for a 12th place overall. It looks like the winds are so weak that they have problems foiling consistently. Even Albeau, who is one of the best foilers, broke his board when running into a sandbank today.
I'd definitely love to hear what Steve Allen has to say, though!

yoyo
WA, 1519 posts
25 May 2017 7:29AM
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Judging by Allen's munted fin , Albeau was not the only sailor to hit a sandbank.

Imax1
VIC, 952 posts
25 May 2017 12:55PM
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Why not go this high ?

Chris 249
ACT, 1293 posts
25 May 2017 1:45PM
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Select to expand quote
boardsurfr said..
Now add a couple smaller and thinner foils further down the fin/mast. As the wind increases, the board gets higher out of the water, leaving only the 2 lower smaller foils in the water, and finally just the lowest foils. Resistance decreases, speed increases. You'll have a system that planes in 6 knots, but with much higher top speed.

For simplicity, the three (or 4 or 5?) foils could be the same size. Now that so many companies have jumped onto the foil wagon, maybe someone will develop this to stand out from the crowd.


The aerodynamic and hydrodynamic guys who design the America's Cup boats say that the problem with having multiple foils is that their span is too narrow compared to the area. It's the same reason why gliders have one long skinny pair of wings instead of having three pairs of stubby wings. So while your top speed may be OK on the small bottom foil, you may have big issues getting going.

racerX
NSW, 362 posts
25 May 2017 9:07PM
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Interesting thread, had a similar idea recently, I think the trick is sizing the lifting foil so that it provides just enough lift to get the board fin combination into a region where increasing speed reduces drag, but no more, and to have the most minimal effect on handling of the board.

To be honest, I prefer to find somewhere windy... nothing new under the sun.

forceten
241 posts
25 May 2017 10:34PM
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I have always felt that aerodynamic input in regard to windsurf fins is overrated .
seldom do aircraft use water, Sully and Malaysia , noted.

the forces between water and air are different.

Indeed interesting thread read and I see no other that approach it.

simple is mostly better

Mastbender
1546 posts
26 May 2017 1:39AM
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I've always wondered why the tunnel fins haven't been expanded on ever since foils have become popular again, but maybe they are?
But instead of making them half round, square them out so that the bottom acts like a shallow water foil, to be used on smooth water. Thinking about it makes my mind explode, the top pic makes me think of the America's Cup boats.





boardsurfr
376 posts
26 May 2017 5:38AM
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Select to expand quote

Chris 249 said..
The aerodynamic and hydrodynamic guys who design the America's Cup boats say that the problem with having multiple foils is that their span is too narrow compared to the area. It's the same reason why gliders have one long skinny pair of wings instead of having three pairs of stubby wings. So while your top speed may be OK on the small bottom foil, you may have big issues getting going.



It's interesting to look at America's Cup boats, and foiling sailboats in general. Many foiling sailboats, including the former record holder Hydroptere, have foil shapes that reduce the wetted area of the foil as the boat gets faster. There are many shapes used here: V-shapes as in the Hydroptere, L-shapes, J-shapes, S-shapes, and more. Speed is not the only objective here, though - some of the curve shapes are designed to give better upwind ability, a very important issue in racing.

America's Cup boats have an L-shaped rudder in front, and two T-shaped foils (which are similar to windsurf foils) in back. Reducing the wetter area does not seem to be a big issue here - why? Well, the America's Cup catamarans are wicked fast even without the foils; we're talking about something like 30 knots without, and 50 knots with foils.

Compare that with the typical foil windsurfer. In the videos I have seen, they typically go from non-planing mode straight into foiling mode. Now that's going from about 6 knots to 20 knots. That's a much bigger difference. When you try to go a lot faster than that, the foil just has too much resistance. When windsurfing without a foil, you can get faster by reducing the wetted area by all kind of means, including switching to a speed board. With a given foil, you're basically stuck. You can switch to a smaller foil with a lower resistance, but you'll loose the low-wind foiling.

All I'm saying is that this does not have to be so if you change the foil design to multiple foils. The lowest foil would be a high-speed foil - let's call it the 40-knot foil. On it's own, it might need a takeoff speed of 20 knot to generate enough lift for foiling. Theoretically, you could put that on a slalom board, start planing to get to 20 knots, and then start foiling. But there are a few problems with that idea; for example, an abrupt transition to foiling at high speeds would be very challenging.

So let's help the high-speed foil out by adding a second foil higher on the mast, like the "Virus foil". The combined lift from both foils will get you foiling just above the water in light winds. As the wind picks up and you get faster, you reach the point where the lift from the lower foil is enough. You rise higher out of the water, and you can start going faster since your foil now has a lot less resistance. The transition is less dramatic than with just a "40-knot" foil, since you just go from "low foiling" to "high foiling". Going to more than 2 foils will give you even more gears, and smoother transitions (like a 9-gear automatic car transmission).

The "glider" argument you bring up kind of misses the point. The glider is always completely surrounded by air, so there's no reason for going to multiple lifting surfaces. But with a two-foil windsurfer, raising the first foil out of the water as wind and speed increase would cut drag resistance by 50% or more, so you'd be able to go 50% faster. But maybe nobody wants to go that fast quite yet, anyway - crashing a foiling windsurfer at 20 or 30 knots looks pretty scary already.

Imax1
VIC, 952 posts
26 May 2017 11:04AM
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Select to expand quote
boardsurfr said..



Chris 249 said..
The aerodynamic and hydrodynamic guys who design the America's Cup boats say that the problem with having multiple foils is that their span is too narrow compared to the area. It's the same reason why gliders have one long skinny pair of wings instead of having three pairs of stubby wings. So while your top speed may be OK on the small bottom foil, you may have big issues getting going.




It's interesting to look at America's Cup boats, and foiling sailboats in general. Many foiling sailboats, including the former record holder Hydroptere, have foil shapes that reduce the wetted area of the foil as the boat gets faster. There are many shapes used here: V-shapes as in the Hydroptere, L-shapes, J-shapes, S-shapes, and more. Speed is not the only objective here, though - some of the curve shapes are designed to give better upwind ability, a very important issue in racing.

America's Cup boats have an L-shaped rudder in front, and two T-shaped foils (which are similar to windsurf foils) in back. Reducing the wetter area does not seem to be a big issue here - why? Well, the America's Cup catamarans are wicked fast even without the foils; we're talking about something like 30 knots without, and 50 knots with foils.

Compare that with the typical foil windsurfer. In the videos I have seen, they typically go from non-planing mode straight into foiling mode. Now that's going from about 6 knots to 20 knots. That's a much bigger difference. When you try to go a lot faster than that, the foil just has too much resistance. When windsurfing without a foil, you can get faster by reducing the wetted area by all kind of means, including switching to a speed board. With a given foil, you're basically stuck. You can switch to a smaller foil with a lower resistance, but you'll loose the low-wind foiling.

All I'm saying is that this does not have to be so if you change the foil design to multiple foils. The lowest foil would be a high-speed foil - let's call it the 40-knot foil. On it's own, it might need a takeoff speed of 20 knot to generate enough lift for foiling. Theoretically, you could put that on a slalom board, start planing to get to 20 knots, and then start foiling. But there are a few problems with that idea; for example, an abrupt transition to foiling at high speeds would be very challenging.

So let's help the high-speed foil out by adding a second foil higher on the mast, like the "Virus foil". The combined lift from both foils will get you foiling just above the water in light winds. As the wind picks up and you get faster, you reach the point where the lift from the lower foil is enough. You rise higher out of the water, and you can start going faster since your foil now has a lot less resistance. The transition is less dramatic than with just a "40-knot" foil, since you just go from "low foiling" to "high foiling". Going to more than 2 foils will give you even more gears, and smoother transitions (like a 9-gear automatic car transmission).

The "glider" argument you bring up kind of misses the point. The glider is always completely surrounded by air, so there's no reason for going to multiple lifting surfaces. But with a two-foil windsurfer, raising the first foil out of the water as wind and speed increase would cut drag resistance by 50% or more, so you'd be able to go 50% faster. But maybe nobody wants to go that fast quite yet, anyway - crashing a foiling windsurfer at 20 or 30 knots looks pretty scary already.


Good points , so wouldn't a V shaped foil be the smoothest rising and possibly the fastest ?,
but.....
I would presume multi wings or V shape foils going over chop would vary the resistance and feel catapulty. Is that why they only use one wing , to foil or not to foil . ???
The old Sydney Harbor ferries used V shape foil ideas but they cant catapult.

evlPanda
NSW, 8220 posts
26 May 2017 5:38PM
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boardsurfr said..
Well, the America's Cup catamarans are wicked fast even without the foils; we're talking about something like 30 knots without, and 50 knots with foils.


Yeah... Well the difference between 30 and 50 knots is like the difference between "Woohoo!" and "Fuuu-uuuuu....!"

Good points though man : )

I gotta say there is suddenly a jump in technological development again. It's been a while!



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"Windfoil alternative (maybe)" started by mark62