Hi,
Interested in people's thoughts regarding wing board design - specifically bottom design. There are about to be a heap of new production wingboards coming out , and I am also considering a custom if I don't see the dims or features I like.

Specifically my question relates to double concaves in the nose and bottom. I am seeing boards coming through with these. Can anyone offer an educated view on whether bottom concaves help or hinder in the following two key areas , vs a flat nose / bottom profile:

- ease of unsticking from the water
- forgiveness in high speed touchdowns eg after dropping down a large swell / wave

I have read two totally different opinions on double concaves for foil boards - the first is that they make the board sticky which takes more effort to pump it up onto the foil , and the second is that it allows air under the board and helps it to unstick. Both of these cannot be right as they are opposite !!!

Similarly , does a simple flat bottom profile allow for more forgiving touchdowns ( touch and go without lurching) than a nose with double concaves?

Could be that there is a trade-off or compromise to be made between the two ie one design starts easier but the other is better for touchdowns.

My suspicion is that double concaves for wingboards may just be fashion, or might be drawn from prone foilboard designs (eg KT) which have the benefit of wave power to get them flying. This is not the same situation as using wind power to unstick a board from flat water. It might also be the usual board design voodoo where most things actually work to some extent and every board designer has their own slant, but I'm more interested in the science - I want a board that will unstick easily and be very forgiving in high speed touchdowns. Hard to compare and contrast different designs before you buy these days .

Interested in your thoughts .....

I don't think there is a ton of science involved. Experience. Fashion. etc

Yup, experimenting is key. From what I read from experimenters: (sorry cant find the pointers)

- forget concaves, the "air trapped under" story is just malarkey. Concaves in surfing bring control, and can bring speed by flattening the rocker along the stringer. But flat bottom is always the fastest. Use concaves if you want more directional control.

- shallow bevels, basically each taking 1/3rd of the width are the best to get unstuck on touchdowns

- narrower bevels help also mastering the row effect on very short boards, and are stabler. This is why you often see narrow bevels on SUP foil boards, but wide ones on kite & surf foil boards. On wing boards I have seen both.

- square noses are stabler, again useful on SUP boards, but rounded or semi-pointed paddle much faster

- whistle tails help pumping on a plane, but are less stable and work better if pushed by a wave/chop than on pure flat water for wing beginners.

For wing boards, I guess what is better depends on your ability: do you favor lateral stability, directional stability, ease of taking off, recovering from touchdowns?

Select to expand quote

mikesids said..
Hi,
Interested in people's thoughts regarding wing board design - specifically bottom design. There are about to be a heap of new production wingboards coming out , and I am also considering a custom if I don't see the dims or features I like.

Specifically my question relates to double concaves in the nose and bottom. I am seeing boards coming through with these. Can anyone offer an educated view on whether bottom concaves help or hinder in the following two key areas , vs a flat nose / bottom profile:

- ease of unsticking from the water
- forgiveness in high speed touchdowns eg after dropping down a large swell / wave

I have read two totally different opinions on double concaves for foil boards - the first is that they make the board sticky which takes more effort to pump it up onto the foil , and the second is that it allows air under the board and helps it to unstick. Both of these cannot be right as they are opposite !!!

Similarly , does a simple flat bottom profile allow for more forgiving touchdowns ( touch and go without lurching) than a nose with double concaves?

Could be that there is a trade-off or compromise to be made between the two ie one design starts easier but the other is better for touchdowns.

My suspicion is that double concaves for wingboards may just be fashion, or might be drawn from prone foilboard designs (eg KT) which have the benefit of wave power to get them flying. This is not the same situation as using wind power to unstick a board from flat water. It might also be the usual board design voodoo where most things actually work to some extent and every board designer has their own slant, but I'm more interested in the science - I want a board that will unstick easily and be very forgiving in high speed touchdowns. Hard to compare and contrast different designs before you buy these days .

Interested in your thoughts .....

Hi Mikesids
For the record I agree with everything Colas said - nice one Colas!!!!!!!!!
I've just had the good fortune to have Jimmy Lewis make me a custom foil board - primarily for SUP foiling but also to double as a light wind wing foil board. 5'9", 29" wide and about 115ltrs. We chatted a lot about design features before settling on the final design - he is adamant that double concaves are only good for directional stability pre-takeoff, but when touching down mid-flight they have a serious braking effect, not only because the water sticks to all those rounded parts, but because the concaves do such a good job of channeling the water that if you are turning when touching down, they force the board to go in a straight line which will throw the rider off balance. Check out this video - if you can take it through one frame at a time from the point where he touches down you'll see that the board brakes so much that he gets tipped 'over the handle bars' so to speak. The board in the video has a well defined double concave bottom shape - see pic.
drive.google.com/file/d/1lIFxhSl_ircaKeugNJeLF95o4ICfqPit/view
cdn.smfboards.com/caf/images/icons/clip.gif' />Both Jimmy Lewis and Dave Kalama design their boards to 'unstick' from the water as easy as possible - Jimmy has a slight 'V' to his hull (hence the name 'Flying V', and Dave makes his hulls like a racing kitefoil board - with the bevels so wide that they go nearly to the centre line of the hull. The tradeoff with such wide bevels is that they lack directional stability, which is why he has to have those keel fins at the front of his board or he'd be paddling in a circle! Not only do these hull designs unstick from the water well when lifting off, but the also allow the board to 'skip' (like when skipping a stone on the surface of the water) when touching down mid-flight rather than sucking down into the water which is what a double concave does.

Thanks Dommo and Colas, appreciate your input. Am going to go simple bottom shape rather than overthink it and make it too complex

Here are the production Jimmy Lewis and Kalama boards:

2 very different bottoms on recently released Wing specific boards, the Fanatic Skywing and the F-One Rocket Wing. Hard to see but the Rocket Wing has some small side bevels, more aggressive tail bevel but otherwise pretty smooth. Which is better for winging?

Select to expand quote

Dommo49 said..

The tradeoff with such wide bevels is that they lack directional stability, which is why he has to have those keel fins at the front of his board or he'd be paddling in a circle!


Dommo49,

You overlooked one important point. Kalama corrected for that lack of directional stability by NOT shaping the rails. His totally square rail and square template make it a wash. The nose fin has nothing to do with your point. The nose fin helps any and all boards that are super short.

Jimmy Lewis gives away directional stability with his pointed nose!

They both have managed their design compromises well.

Not sure I agree with Colas' "forget concaves" comment. There must be some benefits (and yes drawbacks) otherwise you wouldnt get brands like KT, Freedom foilboards, Sunova etc. etc. all deciding on them. This wont have happened by accident. They'll all have had two models-one with concaves, one without- lined up on the beach and gone back and forth. Kai Lenny is a fairly obsessional tester... he's settled on concaves.

There are 2 types of 'touch down'... very gradual touch down followed by gentle release back into the air and also a great big slam down and bounce back up. It's logical that flat/concaves will both be better for one of these and not the other.

We have played with a bunch of concaves on the foil boards but still keep coming back to the flatter bottom. We still have some double concave boards oit the back of the shop that funny enough no one ever chooses to ride which kind of tells me that they just are not quite as good. I found them super sticky for lift of and also very sticky when touching down compared to the flat bottom board I ride everyday.

A lot more advantages can be made when playing around with outlines and rockers if you ask me at the moment. Below are two new protos which are quite different again.

See new Armstrong wing board designs review from real water sports

Select to expand quote

mattllew said..
Not sure I agree with Colas' "forget concaves" comment.

Actually, it was more a knee-jerk reaction to the common fairy tales of "concaves trap air and provide a hovercraft-like air cushion, concaves accelerates water because of this guy Venturi" that "it allows air under the board and helps it to unstick" triggered.

I should have said "forget the hype about concaves".

Select to expand quote

colas said..

mattllew said..
Not sure I agree with Colas' "forget concaves" comment.

Actually, it was more a knee-jerk reaction to the common fairy tales of "concaves trap air and provide a hovercraft-like air cushion, concaves accelerates water because of this guy Venturi" that "it allows air under the board and helps it to unstick" triggered.

I should have said "forget the hype about concaves".

BUT
Concave correctly designed provide benefits.
E.g. stability plus easier directional paddling.
I have a concave and flat bottom boards ranging from 5 ft 7in to 6 ft 11in.
Yes flat bottom boards for me but in comparison skill adjusts to help the concave.
My preference is flat bottom for windwing however as a beginner for SUP foing with the help of a wave face concave helps for my lack of paddling skills on short boards and balance waiting for a set.

Looks like the Armstrong boards don't have a handle on the bottom in front of the foil boxes like the F-One and the One....? Seems one of the obvious additions to make carrying board and wing at the same time easier and keep the foil away from the wing.

I'll be waiting on the sidelines for a while longer while basics like these get sorted out. Many companies releasing new stuff for the hell of it and the hype of it.

I like the idea of one board to do both so will stick with my 6 6 sup. Having kite foiled a prone board (4 10) I found there was not a massive improvement in performance. Yes it felt better but not enough to have to carry an extra board and move the foil from one to the other. So easy now all the gear (board with foil attached, paddle, wing) fit inside my landcruiser.

I would like double length foil tracks in board, able to move way forward for light wind and then move back as wind increases. May work?

Yep, double length tracks starting to appear - will be great I reckon.. no matter what board I have used so far I always end up max forwards in the slot.. So makes sense to have more range.

Select to expand quote

willow75 said..
Yep, double length tracks starting to appear - will be great I reckon.. no matter what board I have used so far I always end up max forwards in the slot.. So makes sense to have more range.

I guess this is a photo shop joke thing.

But a longer than 10" fin box does seems like it could have some strength advantages. Could also be good for some of those angled type foils that are here and there.

Select to expand quote

scotty100 said..
I would like double length foil tracks in board, able to move way forward for light wind and then move back as wind increases. May work?

Get mast tracks put in front of the ones you have now.

haha , not a photoshop joke... pacificpaddlecompany.com/product/wing-sup-foil-board/

The long tracks seem a great idea - means you can use different foils/wings/fuselages and really take the swing weight out of the board if you want - or go track back and make it stable for learning..

Select to expand quote

willow75 said..
haha , not a photoshop joke... pacificpaddlecompany.com/product/wing-sup-foil-board/

The long tracks seem a great idea - means you can use different foils/wings/fuselages and really take the swing weight out of the board if you want - or go track back and make it stable for learning..

Plus - do this to simplify mast installing

Good idea what sort of tracks are they I need to replace a couple of finbox foil tracks because they cracked and leaked water into the board

Yeah huge difference between USA fin box to Chinook style box . You'll get away with std fin boxes on your prone but not on your Sup . These Slingshot Ride Engine boxes are the bomb .

Select to expand quote

warwickl said..

willow75 said..
haha , not a photoshop joke... pacificpaddlecompany.com/product/wing-sup-foil-board/

The long tracks seem a great idea - means you can use different foils/wings/fuselages and really take the swing weight out of the board if you want - or go track back and make it stable for learning..

Plus - do this to simplify mast installing

Will not work on a sup. Too close to tail. Good idea though.

There are three forces involved and each of them has a centre point in the longitudinal axis in a foilboard.
These are gravity (down), lift (up) and buoyancy (up).
One of the biggest reasons why sups fly badly and pump badly is the center of lift is too far back. As @willow75 suggests, the best position almost always ends up being the front of the tracks. Even then it's still not optimal.
For a board to be in balance while flying, the center and gravity and the center of lift should be in the same place, or almost exactly. With a well balanced setup when unweighting both feet the board will carry on flying level. Pumping is much easier, 2 foot pumping is possible, and turning is much easier and smoother.
When on the water you want the center of buoyancy to in the same place as the center of gravity, or even slightly forward - this gives more stability on the water. A lot of SUPs tend to have quite a lot of volume further back. This means you have to stand further back to be stable while standing, which means you have to pull the foil further back to get stability while moving on the water. This lead to the center of lift being behind the center of gravity. So even smaller, minimal volume SUPs end up being unbalanced.
Rather a slightly longer bigger perfectly balanced board than a shorter board that's out of balance in this way.

Select to expand quote

StephenZ said..
the best position almost always ends up being the front of the tracks. Even then it's still not optimal.

The hate posts I got when I stated this 2 years ago... :-)

Select to expand quote

colas said..

StephenZ said..
the best position almost always ends up being the front of the tracks. Even then it's still not optimal.

The hate posts I got when I stated this 2 years ago... :-)

Interesting.
Yesterday I (A beginner) had A few SUP foil attempts on a board with the mast closer to the back than my friends.
We swapped boards as he is experience to check if my set up is ok.
I got on his board and the mast track is considerably further more forward.
First wave I took off much easier up on foil and nicely balanced for my longest controlled flight.
Tomorrow I will move my mast forward to the max which is another 40mm which is still less than my friends.

Less swing weight with mast forward.

For me a pointer nose area is way less affected by wind. I see a well known brand just brought out a board with concave top and bottom, what a joke, good luck with that. Balance and volume forward and back is critical, you want your volume balance point the same as your foil balance point ( but a prone board needs volume aft so your not dragging the foil underwater when you paddle hard for a wave)

Borrowed this idea from gliders.
The aim was to create another point for the water to more readily separate from the board, which has a fairly large flat bottom (sunova 6'8 downwind foil).
It is simply 2 layers of Bear All weather tape (Bunnings) cut into a zig zag pattern running down the centreline, from the nose to the start of the foil box.
I'd like to be able to say it makes x% difference, but I don't know how to compare. My gut feeling is that it isn't any worse and is probably beneficial. A couple of times since adding the tape I have been caught out by the board skipping when I was expecting it to stick. When wing foiling in light conditions my success rate of getting foiling seems to have improved.
Either way, it's staying on my board for now. Will leave it up to you if you want to try it.

Select to expand quote

Stingersup said..
Borrowed this idea from gliders.
The aim was to create another point for the water to more readily separate from the board, which has a fairly large flat bottom (sunova 6'8 downwind foil).

Then what you should do is find a way for the water to wet the hull in "sheets" rather than droplets.
Basically sand at 400 or 600 grit your hull. See "the board lady":
boardlady.com/fast.htm

"In tests I was involved in for an America's Cup boat, we found that simply sanding a glossy bottom with 600 grit paper, reduced the surface friction by about 5% at ? hull speed, i.e. at about 4.5 knots."

Bad:

Good: