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SALKAN said..

Grantmac said..
The SB fuselage lenght is to allow huge sails and it gets pretty miserable under 7.0 apparently, I don't think Moses is chasing the same market.

That is an interesting perspective. If the longer fuselage performs poorly, I rather stick with a shorter fuselage and go to large foil wings to keep a small sail as a recreational foiler.

My understanding (no direct experienece with this one!) is that a long fuselage goes together with a "race" set up. If you are using a wide board with 7.0-9.0 sails and you are going deep up- and down-wind then you might benefit from the extra stability that a longer fuselage gives you. But there is no free lunch, you'll loose in maneuverability ...

90 long seems plenty. My Taaroa Noe works well with a 75 fuselage (plus change for the wings).

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duzzi said..

SALKAN said..

Grantmac said..
The SB fuselage lenght is to allow huge sails and it gets pretty miserable under 7.0 apparently, I don't think Moses is chasing the same market.

That is an interesting perspective. If the longer fuselage performs poorly, I rather stick with a shorter fuselage and go to large foil wings to keep a small sail as a recreational foiler.

My understanding (no direct experienece with this one!) is that a long fuselage goes together with a "race" set up. If you are using a wide board with 7.0-9.0 sails and you are going deep up- and down-wind then you might benefit from the extra stability that a longer fuselage gives you. But there is no free lunch, you'll loose in maneuverability ...

90 long seems plenty. My Taaroa Noe works well with a 75 fuselage (plus change for the wings).

After almost a year of foiling, I had only used the 115 fuse out of my SB team set until two days ago. The 75 fuse definitely has less power to point and is less stable. On the upside, it is much faster, happy to sail fully powered on a reach and is easier to gybe. Under 15kts I still prefer the long fuse though.

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Boston! said..

duzzi said..

SALKAN said..

Grantmac said..
The SB fuselage lenght is to allow huge sails and it gets pretty miserable under 7.0 apparently, I don't think Moses is chasing the same market.

That is an interesting perspective. If the longer fuselage performs poorly, I rather stick with a shorter fuselage and go to large foil wings to keep a small sail as a recreational foiler.

My understanding (no direct experienece with this one!) is that a long fuselage goes together with a "race" set up. If you are using a wide board with 7.0-9.0 sails and you are going deep up- and down-wind then you might benefit from the extra stability that a longer fuselage gives you. But there is no free lunch, you'll loose in maneuverability ...

90 long seems plenty. My Taaroa Noe works well with a 75 fuselage (plus change for the wings).

After almost a year of foiling, I had only used the 115 fuse out of my SB team set until two days ago. The 75 fuse definitely has less power to point and is less stable. On the upside, it is much faster, happy to sail fully powered on a reach and is easier to gybe. Under 15kts I still prefer the long fuse though.

That's good hands on information to know Boston

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lakeeffect said..
There are three ways to handle pitch stability. The first you mentioned which is a longer fuse. The second is a longer foil mast as a longer foil mast as LeeD mentioned. And the third is a larger stabilizer.

I do not believe that long mast would help with pitch stability. How?
The first and the third, yes will do.

In airplane theory there is definition of Tail Volume Coefficient.
Simply speaking Tail Volume Vt = St * Lt
Where St is Tail Area (horizontal in our case) and Lt is distance from tail's aerodynamic center to the aircraft c.g.

Tail Volume Coefficient Cvt = St * Lt / (Sw * bw)
where Sw is wing area and bw is wing span.

Optimal Cvt for airplanes are found time ago and they are ~ 0.5 - 0.8

The more Tail Volume is, the more stable is airplane, in our case a foil.
But if it is too big, it will require more efforts for pitch control. Tough to take off, impossible to jump, etc.

It is more effective to increase Tail Volume by increasing Lt, because increasing St will add drag.

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mm7 said..

lakeeffect said..
There are three ways to handle pitch stability. The first you mentioned which is a longer fuse. The second is a longer foil mast as a longer foil mast as LeeD mentioned. And the third is a larger stabilizer.

I do not believe that long mast would help with pitch stability. How?
The first and the third, yes will do.

In airplane theory there is definition of Tail Volume Coefficient.
Simply speaking Tail Volume Vt = St * Lt
Where St is Tail Area (horizontal in our case) and Lt is distance from tail's aerodynamic center to the aircraft c.g.

Tail Volume Coefficient Cvt = St * Lt / (Sw * bw)
where Sw is wing area and bw is wing span.

Optimal Cvt for airplanes are found time ago and they are ~ 0.5 - 0.8

The more Tail Volume is, the more stable is airplane, in our case a foil.
But if it is too big, it will require more efforts for pitch control. Tough to take off, impossible to jump, etc.

It is more effective to increase Tail Volume by increasing Lt, because increasing St will add drag.

I agree with you in the fact that a longer foil mast in and of itself doesn't decrease pitch instability. But when comparing a 15 in long training foil mast with a 30 in long one; The longer foil mast give the foiler more time to adjust his stance more front footed or back footed before he breaches the foil or starts slapping the chop. Experienced foilers don't have this problem because they instinctually feel how high they are flying. However for beginners like myself it a different story. I don't have the judgement and intuition of an experienced foiler.

On a different topic my foil with a wing area of 2066 cm sq and span of 84cm. My foil mast cross section area is about 9.12 cm sq. Using a tail volume coefficient of .65, I get too large of a number of the optimal foil mast depth in the water. Where am I going wrong?

No. 1, 3, and 4 US Course Race Foilers were on long fuze Starboards.

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LeeD said..
TOW.... time on water...crucial.

Now it's time over water

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lakeeffect said..

mm7 said..

lakeeffect said..
There are three ways to handle pitch stability. The first you mentioned which is a longer fuse. The second is a longer foil mast as a longer foil mast as LeeD mentioned. And the third is a larger stabilizer.

I do not believe that long mast would help with pitch stability. How?
The first and the third, yes will do.

In airplane theory there is definition of Tail Volume Coefficient.
Simply speaking Tail Volume Vt = St * Lt
Where St is Tail Area (horizontal in our case) and Lt is distance from tail's aerodynamic center to the aircraft c.g.

Tail Volume Coefficient Cvt = St * Lt / (Sw * bw)
where Sw is wing area and bw is wing span.

Optimal Cvt for airplanes are found time ago and they are ~ 0.5 - 0.8

The more Tail Volume is, the more stable is airplane, in our case a foil.
But if it is too big, it will require more efforts for pitch control. Tough to take off, impossible to jump, etc.

It is more effective to increase Tail Volume by increasing Lt, because increasing St will add drag.

I agree with you in the fact that a longer foil mast in and of itself doesn't decrease pitch instability. But when comparing a 15 in long training foil mast with a 30 in long one; The longer foil mast give the foiler more time to adjust his stance more front footed or back footed before he breaches the foil or starts slapping the chop. Experienced foilers don't have this problem because they instinctually feel how high they are flying. However for beginners like myself it a different story. I don't have the judgement and intuition of an experienced foiler.

On a different topic my foil with a wing area of 2066 cm sq and span of 84cm. My foil mast cross section area is about 9.12 cm sq. Using a tail volume coefficient of .65, I get too large of a number of the optimal foil mast depth in the water. Where am I going wrong?

I see your point. Totally agree. Long mast gives more space/time for maneuvers.

I do not think mast should be used in calculations of tail volume (horizontal one).
To get tail volume use stab area and length between hydrodynamic centers of wing and stab.
What are you trying to calculate?