If I am not mistaken the general rule of thumb is that bigger front wings are best in lighter wind and tend to become a bit of an handful when the wind become stronger.
So was wondering in stronger wind if you use a smaller (wind) wing with a large front wing shouldn't it result in the same power than a bigger (wind) wing in lighter wind and therefore the same front wing should be able to handle both scenario.
I have a feeling it is not right but can't pinpoint why. Be nice if someone could enlighten me :)
Thanks.

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panpanace said..
If I am not mistaken the general rule of thumb is that bigger front wings are best in lighter wind and tend to become a bit of an handful when the wind become stronger.
So was wondering in stronger wind if you use a smaller (wind) wing with a large front wing shouldn't it result in the same power than a bigger (wind) wing in lighter wind and therefore the same front wing should be able to handle both scenario.
I have a feeling it is not right but can't pinpoint why. Be nice if someone could enlighten me :)
Thanks.

You aren't wrong, but there is really no rule of thumb and there are a lot of factors that people take into account (mostly just preferences). I know there are a lot of generalities (lift isn't just related to size) and oversimplifications here, but here's a stab...

1) The foils lift depends on power input and a larger foil needs less power input to lift than a smaller foil.

2) There is a point at which a larger hand wing becomes impractical, so you need to have a larger foil to get up - this point differs for people of different height and different skill levels.

3) Smaller foils are generally faster and more maneuverable (more fun for many)

Not always, but I think this decision often comes down to what size hand wing a person finds cumbersome. Usually this corresponds with height. I'm tall and I don't mind riding a light 5m wing - so I can size down my foil a bit sooner than a short person (of similar weight) who wants to get onto their 4m. I don't really like riding an overpowered foil and would rather ride an overpowered wing because I like the feel of a smaller foil and can modulate power in the wing more than I can modulate the foil.

I think a lot of people just get a bigger foil to get up in light wind situations when they are maxed out on wing size and size down to a sweet spot foil as soon as they can.

foils can also take some getting used to and also some tuning (where the foil sits in the box, shimming, etc...) - potentially more so than just changing size in a hand wing. As such some people just take a set-it-and-forget-it attitude to the foil, and adjust the wing size accordingly.

Many schools of thought. None are right or wrong.

Well,you asked for it :)

If we use exactly the same design foil in different sizes (and we forget nitpicky things like scaling to simplify):

-The foil lift force depends on foil surface,speed and angle of attack.

-Maximum AOA is stall, (say around 15* in general ).This angle is constant...but the speed at which you reach it is variable, it depends on Wing loading (how many kg the foil is carrying divided by its surface).

-The higher the wing load (smaller foil,bigger rider, G's in a turn) the higher the speed at which you will reach max AOA and stall.

-As speed increases we lower the AOA to maintain the same lift (otherwise we rise and breach).At "cruise" speed all the lift is being generated by the central 50-30% of the foil.The tips have twist (always lower AOA than center) and are working only as endplates,preventing the water flow travel from bottom (high press) to top (low press).

-Go even faster and you get control problems,even with an stab that was not pushing down at all the foil becomes twitchy and very demanding in pitch control, very small changes in AOA result in big surges/drops in lift.The foil is working out of its design parameters (AOA too small),the tips will probably be working in negative lift mode (pushing down) and only the very root near the mast will be producing all the lift.

-Solution: get a smaller foil (increase wing loading) that will require higher AOA at all speeds to lift you.
Carrying ballast will also let you ride the same foil at faster speeds.

Rider skill and water conditions are huge factors too but any foil will crap out eventually if you push it fast enough.

As for sail size,i always feel faster and in better control when my wingsail size lets me sheet in vertical without directing much sail power upwards (makes you lighter and decreases your wing loading).

From vids and posts i have seen, generalizing for an 80kg rider:
-To get 20kt you will want a 1000cm2 foil
-25 kt an 800-900cm2
-30kt a 500-600cm2 (what the top racers use in comps).

hehe, short of acronyms and algebra:

-- on a light wind small wave day you probably need a big foil (most lift), big wing (most wind power), big board (most float and stability)

-- as wind increases, you go smaller on one or more: smaller foil (faster, more maneuverable), smaller wing (lighter, easier handling), smaller board (more maneuverable)

-- as waves get bigger, you'd likely change foil, as wing and board are maybe more wind dependent

I usually try to only change 1 variable at a time. From the kiting days, relaunching was a hassle, so I tended to switch boards to deal with wind changes. With winging, I often have 2 wings pumped, easy switch off as needed ... as we tend to have pretty variable wind

As wind strength increases you always have the choice of dropping a wing size or dropping front foil size (or both). Which you do first can depend on how steady the wind is - if the wind is very steady in strength, keep the wing the same size and go for a smaller foil. If the wind is gusty and variable in strength, go for a bigger foil and a smaller wing, as you will be able to get up on foil in a gust and will then be able to tolerate big gusts or keep foiling through lulls

Lots of good insight and lots of personal preferences too. Just remember which fluid induces more drag. Water is denser, so you should try to be as slippery as possible, a smaller foil will do this. To compliment this, racers will run a 6-7m wing up to 20 knots with the absolute smallest possible foil they can get up on. This was done last season with the FOne riders winging the Escape 530 through all conditions.
This setup isn't the most comfortable or easiest by any measure. A 6m wing at 75kg is just hard work yet these guys love it.

Some really good insights here, thanks everyone. So many variables to play with.

Select to expand quote

mcrt said..
Well,you asked for it :)

If we use exactly the same design foil in different sizes (and we forget nitpicky things like scaling to simplify):

-The foil lift force depends on foil surface,speed and angle of attack.

-Maximum AOA is stall, (say around 15* in general ).This angle is constant...but the speed at which you reach it is variable, it depends on Wing loading (how many kg the foil is carrying divided by its surface).

-The higher the wing load (smaller foil,bigger rider, G's in a turn) the higher the speed at which you will reach max AOA and stall.

-As speed increases we lower the AOA to maintain the same lift (otherwise we rise and breach).At "cruise" speed all the lift is being generated by the central 50-30% of the foil.The tips have twist (always lower AOA than center) and are working only as endplates,preventing the water flow travel from bottom (high press) to top (low press).

-Go even faster and you get control problems,even with an stab that was not pushing down at all the foil becomes twitchy and very demanding in pitch control, very small changes in AOA result in big surges/drops in lift.The foil is working out of its design parameters (AOA too small),the tips will probably be working in negative lift mode (pushing down) and only the very root near the mast will be producing all the lift.

-Solution: get a smaller foil (increase wing loading) that will require higher AOA at all speeds to lift you.
Carrying ballast will also let you ride the same foil at faster speeds.

Rider skill and water conditions are huge factors too but any foil will crap out eventually if you push it fast enough.

As for sail size,i always feel faster and in better control when my wingsail size lets me sheet in vertical without directing much sail power upwards (makes you lighter and decreases your wing loading).

From vids and posts i have seen, generalizing for an 80kg rider:
-To get 20kt you will want a 1000cm2 foil
-25 kt an 800-900cm2
-30kt a 500-600cm2 (what the top racers use in comps).

I don't really get the vertical sheet in, I tend to put my wing up when I am already overpowered.
And if not overpowered then I hold the wing in front of me and sheet in horizontally.
Am I missing something @mcrt?

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Pacey said..
As wind strength increases you always have the choice of dropping a wing size or dropping front foil size (or both). Which you do first can depend on how steady the wind is - if the wind is very steady in strength, keep the wing the same size and go for a smaller foil. If the wind is gusty and variable in strength, go for a bigger foil and a smaller wing, as you will be able to get up on foil in a gust and will then be able to tolerate big gusts or keep foiling through lulls

This is when I would use my larger foil with small hand wing in gusty cross off winds. Other than that I would down foil size before hand wing.

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I don't really get the vertical sheet in, I tend to put my wing up when I am already overpowered.
And if not overpowered then I hold the wing in front of me and sheet in horizontally.
Am I missing something @mcrt?

Ok,i did not explain that well.

We all put the wing up when overpowered, do the "umbrella".
But this directs the sail power upwards and does not make you faster.

The sail is most efficient when you hold the leading edge vertical , gives you max forward drive.

This is very similar to the kiters power window,only we do it at arms length.

Wingfoil racers can carry big wings because their tiny foils can handle that speed in control.
On our bigger foils we eventually have to chicken out and shed excess sail power up, which has the unwanted effect of making you a bit "lighter" ,it reduces the load your foil carries.

So my point is, if you cannot fully sheet in your wing with the leading edge vertical or very close to vertical you are going to be slower.A smaller sail will be faster,less drag,better control.

We tend to ride overpowered for our foil size because our big hurdle is getting up on foil.

To answer your original question:

Big foil and small sail will work fine in stronger winds, but it will be slow.
The foil size is what sets your "speed limit".
Adding sail is useless here because your foil cannot handle any more speed.

Select to expand quote

mcrt said..

I don't really get the vertical sheet in, I tend to put my wing up when I am already overpowered.
And if not overpowered then I hold the wing in front of me and sheet in horizontally.
Am I missing something @mcrt?

Ok,i did not explain that well.

We all put the wing up when overpowered, do the "umbrella".
But this directs the sail power upwards and does not make you faster.

The sail is most efficient when you hold the leading edge vertical , gives you max forward drive.

This is very similar to the kiters power window,only we do it at arms length.

Wingfoil racers can carry big wings because their tiny foils can handle that speed in control.
On our bigger foils we eventually have to chicken out and shed excess sail power up, which has the unwanted effect of making you a bit "lighter" ,it reduces the load your foil carries.

So my point is, if you cannot fully sheet in your wing with the leading edge vertical or very close to vertical you are going to be slower.A smaller sail will be faster,less drag,better control.

We tend to ride overpowered for our foil size because our big hurdle is getting up on foil.

To answer your original question:

Big foil and small sail will work fine in stronger winds, but it will be slow.
The foil size is what sets your "speed limit".
Adding sail is useless here because your foil cannot handle any more speed.

Thanks @mcrt, that makes sense.
Speed is fun once you master it, so I 'need' a smaller front wing when the wind is 18-20+ knots, I am only 70kg and I am learning with an Axis PNG 1010 which is about 1400cm2

Select to expand quote

panpanace said..

mcrt said..

I don't really get the vertical sheet in, I tend to put my wing up when I am already overpowered.
And if not overpowered then I hold the wing in front of me and sheet in horizontally.
Am I missing something @mcrt?

Ok,i did not explain that well.

We all put the wing up when overpowered, do the "umbrella".
But this directs the sail power upwards and does not make you faster.

The sail is most efficient when you hold the leading edge vertical , gives you max forward drive.

This is very similar to the kiters power window,only we do it at arms length.

Wingfoil racers can carry big wings because their tiny foils can handle that speed in control.
On our bigger foils we eventually have to chicken out and shed excess sail power up, which has the unwanted effect of making you a bit "lighter" ,it reduces the load your foil carries.

So my point is, if you cannot fully sheet in your wing with the leading edge vertical or very close to vertical you are going to be slower.A smaller sail will be faster,less drag,better control.

We tend to ride overpowered for our foil size because our big hurdle is getting up on foil.

To answer your original question:

Big foil and small sail will work fine in stronger winds, but it will be slow.
The foil size is what sets your "speed limit".
Adding sail is useless here because your foil cannot handle any more speed.

Thanks @mcrt, that makes sense.
Speed is fun once you master it, so I 'need' a smaller front wing when the wind is 18-20+ knots, I am only 70kg and I am learning with an Axis PNG 1010 which is about 1400cm2

Learning on a good size like that will help develop your skills. Don't jump to too small a foil before you've mastered tacks, gybes and anything else you want or you'll stagnate.

You can then look at getting a HPS 830. ART range could be something else to look at, but they have a few special traits which need a bit of skill to enjoy.

Select to expand quote

King Crash said..

panpanace said..

mcrt said..

I don't really get the vertical sheet in, I tend to put my wing up when I am already overpowered.
And if not overpowered then I hold the wing in front of me and sheet in horizontally.
Am I missing something @mcrt?

Ok,i did not explain that well.

We all put the wing up when overpowered, do the "umbrella".
But this directs the sail power upwards and does not make you faster.

The sail is most efficient when you hold the leading edge vertical , gives you max forward drive.

This is very similar to the kiters power window,only we do it at arms length.

Wingfoil racers can carry big wings because their tiny foils can handle that speed in control.
On our bigger foils we eventually have to chicken out and shed excess sail power up, which has the unwanted effect of making you a bit "lighter" ,it reduces the load your foil carries.

So my point is, if you cannot fully sheet in your wing with the leading edge vertical or very close to vertical you are going to be slower.A smaller sail will be faster,less drag,better control.

We tend to ride overpowered for our foil size because our big hurdle is getting up on foil.

To answer your original question:

Big foil and small sail will work fine in stronger winds, but it will be slow.
The foil size is what sets your "speed limit".
Adding sail is useless here because your foil cannot handle any more speed.

Thanks @mcrt, that makes sense.
Speed is fun once you master it, so I 'need' a smaller front wing when the wind is 18-20+ knots, I am only 70kg and I am learning with an Axis PNG 1010 which is about 1400cm2

Learning on a good size like that will help develop your skills. Don't jump to too small a foil before you've mastered tacks, gybes and anything else you want or you'll stagnate.

You can then look at getting a HPS 830. ART range could be something else to look at, but they have a few special traits which need a bit of skill to enjoy.

Thanks, yeah definitely some way to go before mastering gybes :)
I feel that I am progressing well with my current gear so will keep at it.

Select to expand quote

panpanace said..

mcrt said..

I don't really get the vertical sheet in, I tend to put my wing up when I am already overpowered.
And if not overpowered then I hold the wing in front of me and sheet in horizontally.
Am I missing something @mcrt?

Ok,i did not explain that well.

We all put the wing up when overpowered, do the "umbrella".
But this directs the sail power upwards and does not make you faster.

The sail is most efficient when you hold the leading edge vertical , gives you max forward drive.

This is very similar to the kiters power window,only we do it at arms length.

Wingfoil racers can carry big wings because their tiny foils can handle that speed in control.
On our bigger foils we eventually have to chicken out and shed excess sail power up, which has the unwanted effect of making you a bit "lighter" ,it reduces the load your foil carries.

So my point is, if you cannot fully sheet in your wing with the leading edge vertical or very close to vertical you are going to be slower.A smaller sail will be faster,less drag,better control.

We tend to ride overpowered for our foil size because our big hurdle is getting up on foil.

To answer your original question:

Big foil and small sail will work fine in stronger winds, but it will be slow.
The foil size is what sets your "speed limit".
Adding sail is useless here because your foil cannot handle any more speed.

Thanks @mcrt, that makes sense.
Speed is fun once you master it, so I 'need' a smaller front wing when the wind is 18-20+ knots, I am only 70kg and I am learning with an Axis PNG 1010 which is about 1400cm2

I weigh the same. I use a Cabrinha H1200 (90 wide). I've never felt overpowered even in 25 knots. I just feel like "I should be going faster" as the wind gets stronger. I just learned to gybe on it. No way am I going smaller until I can do all the transitions.