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The New 2018 Airush Core Foil Series Out Now

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davesails7
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Re: The New 2018 Airush Core Foil Series Out Now

Postby davesails7 » Thu Dec 07, 2017 9:51 pm

tegirinenashi wrote: two of them are too close to the leading and trailing edge to have the same effect.
Isn't area farther away from the center exactly what you want if you are trying to increase torsional stiffness? Area away from the center of the area increases the polar moment of inertia.

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Re: The New 2018 Airush Core Foil Series Out Now

Postby jamescarlyle » Thu Dec 07, 2017 10:02 pm

Would be interested to see a proper analysis of this, but torsion results in shear forces around a central point, doesn’t it? And for shear forces, more material away from the centre will result in lower stress and therefore lower strain. Compare the torsional displacement of a solid rod compared to a cylinder of the same mass per unit length.

So it’s not obvious to me why the 3 bolt design is worse - it may be better.

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Re: The New 2018 Airush Core Foil Series Out Now

Postby tegirinenashi » Thu Dec 07, 2017 10:10 pm

Let's remove possible confusion and clarify that we are talking about the same couple of spars:
profile3.png
What I'm saying is that these two spars are so close to the leading and trailing edge that their effect is dubious. If you are not convinced, imagine moving those spars even closer to the edges; would it increase or decrease stiffness? Certainly it can't increase stiffness, because if you move them too close to the edges, they would disappear. And if you have some college degree, then you should have an intuition that the stiffness is a continuous function of the spar location.

P.S. And I'm not even considering those thin walls compromizing the structure...

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Re: The New 2018 Airush Core Foil Series Out Now

Postby Peter_Frank » Thu Dec 07, 2017 10:38 pm

I think the 3 screw option is at least the same, but more likely both stiffer and stronger than 2 screws :thumb:

Knowing that stiffness is "height" cubed, and strength is "height" squared, then if we say the bolts are a lot stiffer and stronger than the mast, a quick calculation say 0.5*0.5'0.5*2+1.2*1.2*1.2 = 2.0 for stiffness of the 3 bolt mast if bending the alumast just at the screw ends versus 1.0*1.0*1.0*2 = 2.0 for the 2 screw option, so same stiffness.

Strength is 0.5*0.5*2+1.2*1.2 = 1.9 versus 1.0*1.0*2 = 2.0 almost the same in terms of strength.

But as the screws are a lot less diameter eventhough stiffer material than alu, they will also bend and be weak, so they are 50 % stronger and stiffer with 3 screws, compared to 2 screws.

All in all the 3 screw solution would seem somewhat both stronger and stiffer IMO, at first glance and a fast mental approximate arithmetic calc.

Having said that, I prefer a 1 screw solution, riding so often and changing masts/boards a lot :rollgrin:

8) PF

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Re: The New 2018 Airush Core Foil Series Out Now

Postby tegirinenashi » Thu Dec 07, 2017 10:53 pm

What are those numbers: 0.5, 1.0, and 1.2?

Speaking of screw strength, the 2-screw solution allows thicker ones. The profile image above featuring 2 screw LF design is M8, while Airush looks like M6. This difference squared implies 77% more strength for M8, cubed is whopping 137%!

Or yeah, don't forget the thread pitch. It requires less turns to screw M8 in :jump:

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Re: The New 2018 Airush Core Foil Series Out Now

Postby wingnut » Fri Dec 08, 2017 3:54 am

Yah! Nuff about that minor design gripe bullshit.We got bigger fish to fry, Yo. How about that foil design huh. Looks great, always wondered if that V tail would have a good effect, both being out of the wing turbulence and providing some additional yaw stability. wot say u ?

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Re: The New 2018 Airush Core Foil Series Out Now

Postby Toby » Fri Dec 08, 2017 7:59 pm

https://www.youtube.com/watch?v=0FW10JqKMpI

phpBB [video]

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Re: The New 2018 Airush Core Foil Series Out Now

Postby rightguard » Sun Dec 10, 2017 7:42 pm

What about the board, it looks cool.

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Re: The New 2018 Airush Core Foil Series Out Now

Postby Schmidy » Sun Dec 10, 2017 9:25 pm

rightguard wrote:
Sun Dec 10, 2017 7:42 pm
What about the board, it looks cool.
The Kiteboarder Magazine did this full overview of the foil range with one of the designers, Clinton Filen.
Gives you a bit more close-ups and insight on the design. :thumb:

phpBB [video]


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