I'm currently running a naish 1400 and 1280 ha foils with a 280 rear wing which works well for me, but looking to switch things up a bit for my wife who is learning. I have a chance to get my hands on a 450 jet rear wing, thoughts on this working to help the learning experience? Is it going to make getting on the foil easier? Or will it just be a horrible match for the 1400 ha front wing.

I Know a dedicated Learning foil would be best, but the funds are not going to stretch that far.

Cheers

In general, bigger stabs provide earlier foiling and increased stability at the expense of top speed, and control at top speed.
So yes, but be sure she is not overpowered by too much wing size.

Bigger stabilisers are more stable and will make things easier. The other options for greater stability are a longer fuselage, or negative shim.

However bigger stabs do not promote earlier foiling, it's actually the opposite (they lift downward). For a given speed the total lift is the lift from the main wing minus the lift from the stabiliser. So with a bigger stabiliser you actually need to be going slightly faster to takeoff, and the stall speed will be higher.

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BritWindfoiler said..
Bigger stabilisers are more stable and will make things easier. The other options for greater stability are a longer fuselage, or negative shim.

However bigger stabs do not promote earlier foiling, it's actually the opposite (they lift downward). For a given speed the total lift is the lift from the main wing minus the lift from the stabiliser. So with a bigger stabiliser you actually need to be going slightly faster to takeoff, and the stall speed will be higher.

Thanks for that great explanation, so need to weigh up stability vs take off speed essentially. It's a good price so maybe worth experimenting

Shims is a great idea, I had an older naish rear wing where you could change the pitch which was handy.

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BritWindfoiler said..However bigger stabs do not promote earlier foiling, it's actually the opposite (they lift downward).

Disagree with that. They fly down which lifts the front wing, which is why they cause you to breach at higher speeds.

Takeoff speed is not going to be a huge difference between those two stabilisers, we're talking a very rough figure around 10%.

If you can shim at -2 degrees, you'll get the equivalent of a stabiliser that is about 20% bigger. You'll need to move the foil mast back in the track to compensate.

When I had a Naish set-up I was using the 1400, however these days I've got Armstrong foils. IMHO the 450 jet stab won't make things easier for a beginner using a HA foil. As Qtwind says the stab produces downforce, but this is a rotational force around the centre of lift on the front wing (it counteracts the weight of the nose of the board). The 450 stab will tend to induce early take-off which is bad for a HA foil (lift off, stall, slap back down). The 280 stab will allow greater take off speed, and a horizontal take-off which is important for HA foils.

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hilly said..

BritWindfoiler said..However bigger stabs do not promote earlier foiling, it's actually the opposite (they lift downward).

Disagree with that. They fly down which lifts the front wing, which is why they cause you to breach at higher speeds.

They do mean more forward foot pressure. However, the better way to achieve this is moving the mast forward in the track.

I fly commercial jets for a living and deal with stabilisers every day! This explains it (though note we set our stabiliser lift by adjusting the angle of attack, the same as shimming, as we can't change stabiliser size):

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BritWindfoiler said..
However bigger stabs do not promote earlier foiling, it's actually the opposite (they lift downward). For a given speed the total lift is the lift from the main wing minus the lift from the stabiliser. So with a bigger stabiliser you actually need to be going slightly faster to takeoff, and the stall speed will be higher.

Interesting point never thought of that. So as far as lift and stall speed the bigger stab just relates to the AOA. Not lift. I thought front foot pressure was a result of lift but maybe more about stab size or shimming... Wow this is kind of a revelation

I've never heard this but it does ring true.

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hilly said..

BritWindfoiler said..However bigger stabs do not promote earlier foiling, it's actually the opposite (they lift downward).

Disagree with that. They fly down which lifts the front wing, which is why they cause you to breach at higher speeds.

I have 3 stabilizers all set to the same angle. 12.5, 14.5 and 18 inches. The larger the stabilizer the easier I get going and the more glide I get; but with increasing speed the larger stabilizer gets harder to control. The small stab gives less lift but better turning and control at speed.

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Fishdude said..

BritWindfoiler said..
However bigger stabs do not promote earlier foiling, it's actually the opposite (they lift downward). For a given speed the total lift is the lift from the main wing minus the lift from the stabiliser. So with a bigger stabiliser you actually need to be going slightly faster to takeoff, and the stall speed will be higher.

Interesting point never thought of that. So as far as lift and stall speed the bigger stab just relates to the AOA. Not lift. I thought front foot pressure was a result of lift but maybe more about stab size or shining... Wow this is kind of a revelation

I've never heard this but it does ring true.

Front foot pressure is increased by four things:

1. A bigger stabiliser
2. Negative shim
3. A longer fuselage
4. Moving the foil mast forward in the track

The general downsides of 1+2 are: greater drag and more stability (harder to pump).


Overall upward lift has nothing to do with the amount of front foot pressure. It is simply Main Wing Lift minus Stabiliser Lift.

Think about it like this: if you had a stabiliser the same size as the front wing, would you get up on the foil? The answer = no, because overall upward lift is zero (well, at zero AoA anyway).

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BritWindfoiler said..

hilly said..

BritWindfoiler said..However bigger stabs do not promote earlier foiling, it's actually the opposite (they lift downward).

Disagree with that. They fly down which lifts the front wing, which is why they cause you to breach at higher speeds.

They do mean more forward foot pressure. However, the better way to achieve this is moving the mast forward in the track.

I fly commercial jets for a living and deal with stabilisers every day! This explains it (though note we set our stabiliser lift by adjusting the angle of attack, the same as shimming, as we can't change stabiliser size):

Hi Brit, i fly the A320.
I was pretty sure that the stab always worked in "negative" lift mode but i have begun to wonder if this is actually true when close to stall speed, or better said, stall AOA.

Most plane wings stall around 15* AOA which is a very steep nose up attitude.I am assuming our foils do the same.

Do you think that the stab might be working in positive lift mode at AOA's close 15*?
It is a speed/AOA range (very draggy,well below L/D ) that we only use on takeoff,finishing a maneuver or maybe in the slowest phase of the pumping stroke.

I have heard many of the guys who pump well say that bigger stabs are "easier" to pump, but i am not sure if this is due to the added stability or because the stab is actually adding a bit of positive lift at some point.

Some airplanes can be flown with the tail lifting ,though in general is not a healthy thing to do :).

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BritWindfoiler said..Think about it like this: if you had a stabiliser the same size as the front wing, would you get up on the foil? The answer = no, because overall upward lift is zero (well, at zero AoA anyway).

Sorry but they do work.


Even this works:

I agree with Hilly.
I have 4 stabs for 3 foils, and largest foils soonest, and is most stable in it's range...low to mid.
Smaller stabs need more wind, bigger engine, or moved forwards, has great top end, but stutters in light to medium wind.
Obviously the right combination of gear to rider weight-skill is best.

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LeeD said.. Obviously the right combination of gear to rider weight-skill is best.

Yep.

At slow speeds you change AOA by pumping and back foot pressure to get the foil flying so the larger area will give you more lift. When at speed and flying all the theory comes into practice.

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hilly said..

Where did you get those graphs Hilly?.
Do you have a link?

www.nwkite.com/forums/t-35608.html

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hilly said..
www.nwkite.com/forums/t-35608.html

Thanks, this Java applet is pretty cool:

www.grc.nasa.gov/WWW/K-12/airplane/foil3.html

You can mess with positive or negative AOA and camber profile and see the resultant Lift&Drag.

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hilly said..

BritWindfoiler said..Think about it like this: if you had a stabiliser the same size as the front wing, would you get up on the foil? The answer = no, because overall upward lift is zero (well, at zero AoA anyway).

Sorry but they do work.

Even this works:

That's not the same as my hypothetical setup though. Both of those examples contain two upward-lifting wings (well actually the plates on the bottom one are symmetric so will do either)

As mcrt points out, if the board/plane nose tilts up, then AoA on the front wing increases, but it actually decreases on the stab as it's upside down.

In terms of the stall speed (and therefore takeoff speed) increasing with stabiliser lift, here is another diagram (forward CofG is akin to a stable setup with a large stabiliser). Because the stabiliser lifts down, the effective weight of the aircraft increases when it produces more lift:

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Hi Brit, i fly the A320.
I was pretty sure that the stab always worked in "negative" lift mode but i have begun to wonder if this is actually true when close to stall speed, or better said, stall AOA.

Most plane wings stall around 15* AOA which is a very steep nose up attitude.I am assuming our foils do the same.

Do you think that the stab might be working in positive lift mode at AOA's close 15*?
It is a speed/AOA range (very draggy,well below L/D ) that we only use on takeoff,finishing a maneuver or maybe in the slowest phase of the pumping stroke.

I have heard many of the guys who pump well say that bigger stabs are "easier" to pump, but i am not sure if this is due to the added stability or because the stab is actually adding a bit of positive lift at some point.

Some airplanes can be flown with the tail lifting ,though in general is not a healthy thing to do :).

Me too! Been flying them for more than 10 years now, Boeing before that.

Remember we trim the stab for slow speeds, so we shouldn't get to that situation. With the fixed stabiliser setup of a foil I'm sure it will occur.





I think the pumping is a little different. Certainly, a longer fuselage/bigger stab requires more effort to pump. A bigger stab however may be easier to use as a paddle to get you out of the water.


Yeah, fly-by-wire modern jets have an unstable setup, but the FCCs assist the pilot as it would be impossible to fly otherwise. It does make them very maneuverable though.

The Naish 80cm fuselage is great for reducing yaw and pitch instability, make learning to gybe and foot changes much easier. It's actually the only fuselage I use for winging, mainly swell riding as there is no need for tight snappy turns.

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BritWindfoiler said..

hilly said..

BritWindfoiler said..Think about it like this: if you had a stabiliser the same size as the front wing, would you get up on the foil? The answer = no, because overall upward lift is zero (well, at zero AoA anyway).

Sorry but they do work.

Even this works:

That's not the same as my hypothetical setup though. Both of those examples contain two upward-lifting wings (well actually the plates on the bottom one are symmetric so will do either)

As mcrt points out, if the board/plane nose tilts up, then AoA on the front wing increases, but it actually decreases on the stab as it's upside down.

In terms of the stall speed (and therefore takeoff speed) increasing with stabiliser lift, here is another diagram (forward CofG is akin to a stable setup with a large stabiliser). Because the stabiliser lifts down, the effective weight of the aircraft increases when it produces more lift:

That's my point you are using high speed air theory on foils. They do not work the same. At slow speeds a bigger stabiliser will get you out of the water easier and be more stable. That is what this thread is about.

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That's my point you are using high speed air theory on foils. They do not work the same. At slow speeds a bigger stabiliser will get you out of the water easier and be more stable. That is what this thread is about.

Honestly, they are the same in the speed regions we're talking about (I'm not talking about high airspeeds with planes).

I totally agree that bigger stabiliser will make the whole setup more stable, and better for a beginner. I just want to contest the minor point it makes you foil at a lower speed because it doesn't, it's the opposite. It's relatively minor though.

A bigger stabiliser will result in more front foot pressure. In the same way, a lot of manufacturers write "more lift" on the forward bit of the foil track. What they actually mean is "more front foot pressure"/"nose up pitch".

With aircraft, we get better takeoff performance with less stabiliser lift, as you'd expect given the stabiliser lift is downward and adding to the overall weight, and it's exactly the same with foiling.

Anyway, I'll leave it there!

Well, smaller is not always better in my case, I seem to feel some kind of balance with size of front wing in my opinion and a smaller stab is not a clear cut faster. On 2 sec spike, not always on my gps...on an average for 1 hour ride yes....so I cruise a little bit faster...it feels faster, but when I look my watch, sometime I have some shocking results. I'm not racing and trying to bust 40knts also, but test with a GPS and let us know your result.

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BritWindfoiler said..

Honestly, they are the same in the speed regions we're talking about (I'm not talking about high airspeeds with planes).

I totally agree that bigger stabiliser will make the whole setup more stable, and better for a beginner. I just want to contest the minor point it makes you foil at a lower speed because it doesn't, it's the opposite. It's relatively minor though.

A bigger stabiliser will result in more front foot pressure. In the same way, a lot of manufacturers write "more lift" on the forward bit of the foil track. What they actually mean is "more front foot pressure"/"nose up pitch".

With aircraft, we get better takeoff performance with less stabiliser lift, as you'd expect given the stabiliser lift is downward and adding to the overall weight, and it's exactly the same with foiling.

Anyway, I'll leave it there!

IMHO the big difference with foils and planes is that foils use a movable CG and a fixed tail,opposite with planes.

So maybe in a foil takeoff the max AOA of the front wing is putting the fixed tail well into upwards lift mode,even though it is an asym camber profile.

I think i remember a KDmaui interview in which he said something about this positive stab lift, will try to find it.

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IMHO the big difference with foils and planes is that foils use a movable CG and a fixed tail,opposite with planes.

So maybe in a foil takeoff the max AOA of the front wing is putting the fixed tail well into upwards lift mode,even though it is an asym camber profile.

I think i remember a KDmaui interview in which he said something about this positive stab lift, will try to find it.

The other huge difference is that planes normally have the centre of thrust very close to the centre of drag from the wings. With winging the thrust from the wing is probably 2 meters or more above the foil wings. That creates a rotational torque forcing the nose down at speed that needs to be counteracted by the stabiliser. I believe that's why the stabiliser size and shimming has to be carefully matched to the front wing and the rider's weight to get fairly stable front/rear foot pressure as speed changes.

I would get the bigger 310HA stabilizer instead. It has a faster foil section than the Jet Stabs and will make the setup rock solid. But if you really want her to have a stable setup to learn on, the 80cm fuse is the answer. It'll really help w her jibes as well. I've played around w/ all the options.

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mcrt said..

IMHO the big difference with foils and planes is that foils use a movable CG and a fixed tail,opposite with planes.

So maybe in a foil takeoff the max AOA of the front wing is putting the fixed tail well into upwards lift mode,even though it is an asym camber profile.

I think i remember a KDmaui interview in which he said something about this positive stab lift, will try to find it.

Yeah, foiling is like hang-gliding in terms of controlling pitch by moving the CofG.

I think the stab could well produce upward lift at extreme AoA, but I don't think you don't get anywhere near max AoA on takeoff. Max AoA is very draggy due to the induced drag. Maximum Lift:Drag occurs around 5-6 degrees (depending on the foil), so I think that is where the target pitch is. If you watch most people get foiling, the board is fairly flat, especially so for beginners not pumping


As has been said, another way to increase stability is get a longer fuselage.

And don't forget, 1400 HA is considered big for anyone around 70 kg in weight.
1400 HA has low end lift similar to i76 at 1550, considered big even for 85 kg riders.
Longer fuse IS more stable, but wing has more stable lift than sails for windfoiling.
I have the 310. Good early lift and too much at any speed, for me at 72 kg.
I'd get the Jet 450 for low end and stability.

In this old vid I was using the HA1400 and the big 310 stabilizer that normally is paired with the HA1800.

I later got the correct 290 rear and to be honest I didn't notice much difference.