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New marginal wind weapon: Kruiser Lightwind

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Regis-de-giens
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Re: New marginal wind weapon: Kruiser Lightwind

Postby Regis-de-giens » Sun Apr 21, 2019 11:23 pm

That is a very nice review and thank you for the dedicated test.
Seems indeed a very good choice for me, if not so expensive, i have to count my centimes ...

Back to lower end : i understand you have a better upwind angle, but would you say that you are sure to foil-up earlier just after the waterstart phase or us 1200 sooner ? Compared to ketos easy, 1200 foil up sooner (i.e. ar lower speed)

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Re: New marginal wind weapon: Kruiser Lightwind

Postby PullStrings » Sun Apr 21, 2019 11:57 pm

Do you think these efficiency results will change in July and August when the air is much warmer and the water temperature reaches 71F compared to what you have now at 46F ?

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Re: New marginal wind weapon: Kruiser Lightwind

Postby tallakt » Mon Apr 22, 2019 7:02 am

Flyboy wrote:
Fri Apr 05, 2019 10:42 pm
Can someone explain the difference characteristics imparted by the shapes? Anedral, dihedral, polyhedral & flat?
besides the more practical issues (anhedral will make the tips touch bottom before the center), anhedral and dihedral have an effect when the wing is subjected to a sideslip, ie. the wing is not pointing directly along the water flow.

A dihedral wing (or a wing in general with wingtips facing up) will cause the wing to apply a moment of rotation so that it will face into the turn. For a foil, if the effect has a practical effect, it will cause the wing to move slightly outward during the turn, all by itself. The turns would probably be smoother.

anhedral has the opposite effect. Anhedral wings are used for aircraft to make the plane more agile. when you initiate a turn, the plane is unstable and amplifies the motion.

Im not sure how this all translates to foil wings.

Sweepback of the wing (wingtips further to the rear compared to center of wing) will have the same effect as dihedral. So a anhedral wing with sweepback could be considered "neutral dihedral effect" etc.

My guess is that for a hydrofoil you would probably want some degree of dihedral effect in your wing

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Re: New marginal wind weapon: Kruiser Lightwind

Postby Peter_Frank » Mon Apr 22, 2019 7:19 am

Regis-de-giens wrote:
Sun Apr 21, 2019 11:23 pm
That is a very nice review and thank you for the dedicated test.
Seems indeed a very good choice for me, if not so expensive, i have to count my centimes ...

Back to lower end : i understand you have a better upwind angle, but would you say that you are sure to foil-up earlier just after the waterstart phase or us 1200 sooner ? Compared to ketos easy, 1200 foil up sooner (i.e. ar lower speed)

I can not say for sure, but even if 8 % smaller, it definitely seems it goes at least as early, maybe earlier - and once up for sure I can go lower.

Think it lifts a tad more, the profile, as it feels like I need a tad more kitepower to go as fast on down or halfwind.

Myself, not in doubt at all, for marginal wind the Kruiser anytime over the 1200, I can ride in less wind :D


And no Pullstrings, these angles and startup speeds wont be affected by water temperature.
Going from 8 to 20 degree water, the water density only drops 0,2 % which is virtually nothing, and it wont affect the angle even if it dropped a lot more, only the startup speed.

They are just rough practical tests, which can change hugely by so many other parameters too, and the water termperature is negligible.
Only air temperature changes kitepower somewhat, going from 15 C to 30 C you need 5 % more kite.

8) Peter
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tegirinenashi
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Re: New marginal wind weapon: Kruiser Lightwind

Postby tegirinenashi » Mon Apr 22, 2019 3:43 pm

Flyboy wrote:
Fri Apr 05, 2019 10:42 pm
Can someone explain the difference characteristics imparted by the shapes? Anedral, dihedral, polyhedral & flat?
It's just BS and loss of efficiency. Look at the aircrafts, they have straight wings for a reason. Oh, yeah, unlike kitesurfing industry they test their stuff in wing tunnel.

Speaking of stability, just use a rudder, or a wider mast.

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Re: New marginal wind weapon: Kruiser Lightwind

Postby jakemoore » Mon Apr 22, 2019 4:06 pm

tegirinenashi wrote: It's just BS and loss of efficiency. Look at the aircrafts, they have straight wings for a reason. Oh, yeah, unlike kitesurfing industry they test their stuff in wing tunnel.

Speaking of stability, just use a rudder, or a wider mast.
Durr....

https://aviation.stackexchange.com/ques ... o-aircraft

http://www.aviation-history.com/theory/ ... hedral.htm

https://www.aircraftnerds.com/2017/01/D ... Wings.html

Image

Image

Image

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tegirinenashi
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Re: New marginal wind weapon: Kruiser Lightwind

Postby tegirinenashi » Mon Apr 22, 2019 4:45 pm

The airplane wing angle is dictated by engineering decision to have wing mount point high or low. For example, harrier can direct its thrust down Image, so they attached wings at the top. And why did they angled the wings so much? Is it for stability, or simply because if the wings were horizontal, the chassis post would have been ridiculously long?

Returning to the foil world, there is no longer a variable of the wing mounted above or below the center of gravity. Wait a minute, actually the wing is so ridiculously below the center of gravity, that following the aircraft example they should universally be dihedral?

Once again, the presence of the huge mast rudder dwarfs any stabilization effect that you achieve by bending the wings. We all know: those fancy hydrofoil wing shapes serve no other purpose other than tempting the buyer. But the sexier looking foils are not necessarily the ones that ride better.
Last edited by tegirinenashi on Mon Apr 22, 2019 5:15 pm, edited 3 times in total.

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Re: New marginal wind weapon: Kruiser Lightwind

Postby jakemoore » Mon Apr 22, 2019 5:06 pm

tegirinenashi wrote:
Mon Apr 22, 2019 4:45 pm
Come on, we all know, those fancy hydrofoil wing shapes serve no other purpose other than tempting the buyer. But the sexier looking foils are not necessarily the ones that ride better.
I wonder if sex appeal helps Mikes lab foils win races?

I have a flat foil with G-10 wings. Its cool but it rides different than my foil with shaped wings.

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tegirinenashi
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Re: New marginal wind weapon: Kruiser Lightwind

Postby tegirinenashi » Mon Apr 22, 2019 5:28 pm

I admit, I learned something from this aircraft parallel. The stability of aircraft is better when the center of mass is closer to the center of lift. (This is just an elementary law of mechanical leverage). Therefore, if the wing is mounted at the top of fuselage, they angle it downwards, and when it is mounted at the bottom, they angle it up.

For hydrofoil, however, aligning the center of lift force and the center of mass ... not a chance. And even assuming for a minute that the goal were raising or lowering the center of the lift force, it would have trivially been achieved by lengthening, or shortening the mast.

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Re: New marginal wind weapon: Kruiser Lightwind

Postby slowboat » Mon Apr 22, 2019 6:15 pm

Peter_Frank wrote:
Mon Apr 22, 2019 7:19 am
Regis-de-giens wrote:
Sun Apr 21, 2019 11:23 pm
That is a very nice review and thank you for the dedicated test.
Seems indeed a very good choice for me, if not so expensive, i have to count my centimes ...

Back to lower end : i understand you have a better upwind angle, but would you say that you are sure to foil-up earlier just after the waterstart phase or us 1200 sooner ? Compared to ketos easy, 1200 foil up sooner (i.e. ar lower speed)

I can not say for sure, but even if 8 % smaller, it definitely seems it goes at least as early, maybe earlier - and once up for sure I can go lower.

Think it lifts a tad more, the profile, as it feels like I need a tad more kitepower to go as fast on down or halfwind.

Myself, not in doubt at all, for marginal wind the Kruiser anytime over the 1200, I can ride in less wind :D


And no Pullstrings, these angles and startup speeds wont be affected by water temperature.
Going from 8 to 20 degree water, the water density only drops 0,2 % which is virtually nothing, and it wont affect the angle even if it dropped a lot more, only the startup speed.

They are just rough practical tests, which can change hugely by so many other parameters too, and the water termperature is negligible.
Only air temperature changes kitepower somewhat, going from 15 C to 30 C you need 5 % more kite.

8) Peter
Back to the foil in discussion and practical characteristics. Maybe I missed something but are you saying this foil is better in light wind, can go slower, has better upwind angles and is just as good as the 1200 wave wing in waves? So it replaces the wave wing, right?


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