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roll stability of foils?

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abel
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Re: roll stability of foils?

Postby abel » Wed Aug 16, 2017 8:04 pm

gmb13 wrote:
Wed Aug 16, 2017 6:38 pm
....
But hey. What do I know about foils? ;-)
--
Gunnar
I assume a bit or two compared to one that doesn't have the possibility to change/test different wings and manufacturers
Not too much choices on the Silente and single foiler on my spot :cry:, so I try to learn as much as possible form the experienced guys before taking any decisions,
that eventually will cause me losing a lot of time (as it already is happening), not to mention the cost.
Thanks!

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abel
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Re: roll stability of foils?

Postby abel » Wed Aug 16, 2017 8:10 pm

plummet wrote:
Wed Aug 16, 2017 7:37 pm
I agree with Gunnar. I've been playing with my aoa lately to try and find the optimal angle between stability and reduced roll resistance. For wave riding I want a lively fast to react foil. But that makes so I back the aoa off and get a lively beast that will roll easily. But man its twitchy. Still trying to find that magic spot. I think i'm almost there.

So note. For my testing I'm shimming using ducttape. 2 slithers of ducttape makes a huge difference!
Are you talking about shimming the AOA of the rear wing?

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Re: roll stability of foils?

Postby Blackrat » Wed Aug 16, 2017 8:24 pm

By changing the angle of incidence you are changing where the cg of the foil is which in turn changes the stability of the whole hydrofoil
More down thrust on the rear forces cg forwards creating stability

The front wing angle (from dihedral to anhedral) has the highest influence affecting JUST roll sensitivity and not the whole foil's stability

So yes you need to differentiate between hydrofoil stability and roll sensitivity

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Re: roll stability of foils?

Postby Rufusz » Wed Aug 16, 2017 9:09 pm

gmb13 wrote:
Wed Aug 16, 2017 12:28 pm
...
That aside, the stability and resistance are controlled more thought the back wing than the front. You will notice how a more active back wing (higher angle of attack or size) will give you more roll resistance.
...
So shimming the stabilizer could make a foil more "beginner friendly"? For example when learning foot changes?

Have you tried it yet? I have a Fluente 550/330 and would not hesitate to use any unfair advantage to learn gybes :)

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Re: roll stability of foils?

Postby Pedro Marcos » Wed Aug 16, 2017 10:16 pm

Rufusz wrote:
Wed Aug 16, 2017 9:09 pm
gmb13 wrote:
Wed Aug 16, 2017 12:28 pm
...
That aside, the stability and resistance are controlled more thought the back wing than the front. You will notice how a more active back wing (higher angle of attack or size) will give you more roll resistance.
...
So shimming the stabilizer could make a foil more "beginner friendly"? For example when learning foot changes?

Have you tried it yet? I have a Fluente 550/330 and would not hesitate to use any unfair advantage to learn gybes :)
The 550/330 its more then good enough to learn gybes, if you want to change something change the mast, for the 101cm instead of 91.

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Re: roll stability of foils?

Postby alexrider » Thu Aug 17, 2017 1:56 am

gmb13 wrote:
Wed Aug 16, 2017 6:38 pm
...When you switch out front wings (for example Zeeko Freeride wing to Speed wing) you will notice no huge amount of change in roll stability. But if you reduce the angle of the tailplane (shim) you will have a major change.
--
Gunnar

That's interesting, but I don't understand the reason at all. Can you explain and say which way the angle of the stabiliser improves roll stability, i.e. more or less tailplane angle of attack?
Incidentally (sic), one thing I noticed when switching from the Zeeko Freeride W&G (with anhedral) to the Carver (flat) is better pitch stability, and I attribute it not to its wider chord but to its different angle of attack relative to the tailplane. The board also rides flatter relative to water surface than with the definitely Freeride wing (=> nose up stance).
I want to experiment changing the tailplane angle with the Freeride, will a plastic shim do, or a wedge be better. I wish all the manufacturers offered the option to change the angle of attack of front and back wings to suit preferences and conditions. I did so when I was learning with the Cab Double Agent, by increasing the stab angle of attack with a shim in order to reduce the pitch up tendency leading to porpoising. When the yoyoing was under control, I removed the shim after I noticed I needed too much back foot pressure when edging hard to windward.

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Re: roll stability of foils?

Postby TomW » Thu Aug 17, 2017 5:29 pm

Pedro Marcos wrote:
Wed Aug 16, 2017 10:16 pm
Rufusz wrote:
Wed Aug 16, 2017 9:09 pm
gmb13 wrote:
Wed Aug 16, 2017 12:28 pm
...
That aside, the stability and resistance are controlled more thought the back wing than the front. You will notice how a more active back wing (higher angle of attack or size) will give you more roll resistance.
...
So shimming the stabilizer could make a foil more "beginner friendly"? For example when learning foot changes?

Have you tried it yet? I have a Fluente 550/330 and would not hesitate to use any unfair advantage to learn gybes :)
The 550/330 its more then good enough to learn gybes, if you want to change something change the mast, for the 101cm instead of 91.
Pedro, I have the 2016 Fluente 93cm mast. You think the longer vorace is better to learn gybes on??

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Re: roll stability of foils?

Postby Peter_Frank » Thu Aug 17, 2017 5:44 pm

No Tom, use whatever mast length you prefer, it does not really matter for jibing IMO so don't think about that, just use some time learning, might take years but this is pretty normal :D )

8) PF

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Re: roll stability of foils?

Postby Pedro Marcos » Thu Aug 17, 2017 7:07 pm

TomW wrote:
Thu Aug 17, 2017 5:29 pm
Pedro Marcos wrote:
Wed Aug 16, 2017 10:16 pm
Rufusz wrote:
Wed Aug 16, 2017 9:09 pm


So shimming the stabilizer could make a foil more "beginner friendly"? For example when learning foot changes?

Have you tried it yet? I have a Fluente 550/330 and would not hesitate to use any unfair advantage to learn gybes :)
The 550/330 its more then good enough to learn gybes, if you want to change something change the mast, for the 101cm instead of 91.
Pedro, I have the 2016 Fluente 93cm mast. You think the longer vorace is better to learn gybes on??
I don't know the part of the gybe that you have problems with, is the the carving and changing direction or the actual change of feet ?

To practice changing feet try it several times in the same tack without any change of direction.

The setup you have is really good to carve around and change direction, there is more " stable " setups that will make changing feet easier, but the change of feet it's much more about speed and timing then anything else.

The 550/330 it's great , I've all the Moses wings now , and the 550 is my overall favourite, I use the others in more specific situations.

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Re: roll stability of foils?

Postby plummet » Thu Aug 17, 2017 7:35 pm

abel wrote:
Wed Aug 16, 2017 8:10 pm
plummet wrote:
Wed Aug 16, 2017 7:37 pm
I agree with Gunnar. I've been playing with my aoa lately to try and find the optimal angle between stability and reduced roll resistance. For wave riding I want a lively fast to react foil. But that makes so I back the aoa off and get a lively beast that will roll easily. But man its twitchy. Still trying to find that magic spot. I think i'm almost there.

So note. For my testing I'm shimming using ducttape. 2 slithers of ducttape makes a huge difference!
Are you talking about shimming the AOA of the rear wing?
yep


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