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Holes in aluminum mast

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pj sofine
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Holes in aluminum mast

Postby pj sofine » Mon Sep 03, 2018 3:11 am

Just some musings! How much stress is actually exerted on a foil mast? Are the aluminum masts way over engineered as far as strength is concerned? What if the mast had a series of holes drilled through it to get rid of unwanted weight? Then it could be covered with a thin adhesive film. Seems like swiss cheese has about the same strength as a slice of American.

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tegirinenashi
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Re: Holes in aluminum mast

Postby tegirinenashi » Mon Sep 03, 2018 4:30 am

Masts are hollow, therefore it is not much weight savings that you'll get there. For comparison, fuselages of at least three vendors: Can Lf asd SS are designed sloppily -- they are just solid rectangular bars of aluminum. The foil designers were probably unaware of the fact that the tail section of the fuselage is under much less stress than the front one, and unlike the front wind, the stab is never exerting the full force of lifting the weight of the rider. 1.2 kg for the fuselage (LF "hydrodynamic" fuse), give me a break. There are some companies that seems to be competent doing their job; Mozes alum fuse looks OK. (How much does it weigh?)

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Re: Holes in aluminum mast

Postby gmb13 » Mon Sep 03, 2018 9:38 am

This is what happens when you underestimate the forces on the mast when you design foils.
Bent mast 2.jpg
Bent mast.jpg


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pj sofine
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Re: Holes in aluminum mast

Postby pj sofine » Mon Sep 03, 2018 3:03 pm

gmb13 wrote:
Mon Sep 03, 2018 9:38 am
This is what happens when you underestimate the forces on the mast when you design foils.

Bent mast 2.jpg

Bent mast.jpg



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Gunnar
Thats quite the "lever"! So it looks like the further you get from the wing the stress increases. I've got the ss masts,maybe I'll sacrifice one for the sake of science! Maybe fill the holes with the lightest foam hmmmm

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Re: Holes in aluminum mast

Postby pj sofine » Mon Sep 03, 2018 3:08 pm

tegirinenashi wrote:
Mon Sep 03, 2018 4:30 am
Masts are hollow, therefore it is not much weight savings that you'll get there. For comparison, fuselages of at least three vendors: Can Lf asd SS are designed sloppily -- they are just solid rectangular bars of aluminum. The foil designers were probably unaware of the fact that the tail section of the fuselage is under much less stress than the front one, and unlike the front wind, the stab is never exerting the full force of lifting the weight of the rider. 1.2 kg for the fuselage (LF "hydrodynamic" fuse), give me a break. There are some companies that seems to be competent doing their job; Mozes alum fuse looks OK. (How much does it weigh?)
Good point. Maybe Ill experiment on the fuselage.I'll be moving on soon to another foil if my riding continues to get better,right now it doesn't matter what I ride,just need time on water.

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Re: Holes in aluminum mast

Postby Lokihel » Mon Sep 03, 2018 5:47 pm

pj sofine wrote:
Mon Sep 03, 2018 3:03 pm
Thats quite the "lever"! So it looks like the further you get from the wing the stress increases. I've got the ss masts,maybe I'll sacrifice one for the sake of science! Maybe fill the holes with the lightest foam hmmmm
If you can't calculate moments you won't understand much of your experiments. The further you are from the point at which the force is exerted the bigger the bending moment, the bigger the stress.

Foam inside a hollow mast will do very little to increase stiffness.
The problem is that it is actually quite hard to accurately estimate the forces acting on a hydrofoil. People always think the hydrofoil has to lift the weight of the rider to take-off. This is wrong; the kite can help quite a lot if you need to take-off at low speed. The foil will lift (as near as makes no difference) the weight of the rider only when you have the kite very low, at which point you will be going quite fast anyway.
When racing upwind, how much lift must the foil provide? Quite sure it is a lot more than the weigh of the rider?

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Re: Holes in aluminum mast

Postby pj sofine » Tue Sep 04, 2018 1:20 pm

Lokihel wrote:
Mon Sep 03, 2018 5:47 pm
pj sofine wrote:
Mon Sep 03, 2018 3:03 pm
Thats quite the "lever"! So it looks like the further you get from the wing the stress increases. I've got the ss masts,maybe I'll sacrifice one for the sake of science! Maybe fill the holes with the lightest foam hmmmm
If you can't calculate moments you won't understand much of your experiments. The further you are from the point at which the force is exerted the bigger the bending moment, the bigger the stress.

Foam inside a hollow mast will do very little to increase stiffness.
The problem is that it is actually quite hard to accurately estimate the forces acting on a hydrofoil. People always think the hydrofoil has to lift the weight of the rider to take-off. This is wrong; the kite can help quite a lot if you need to take-off at low speed. The foil will lift (as near as makes no difference) the weight of the rider only when you have the kite very low, at which point you will be going quite fast anyway.
When racing upwind, how much lift must the foil provide? Quite sure it is a lot more than the weigh of the rider?
My problem is I have an over active imagination without the knowledge, initiative and concentration necessary to actually accomplish anything! :boring:

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Re: Holes in aluminum mast

Postby irwe » Tue Sep 04, 2018 5:50 pm

Gunnar what was the length of the F1 mast?

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Re: Holes in aluminum mast

Postby gmb13 » Tue Sep 04, 2018 8:05 pm

irwe wrote:
Tue Sep 04, 2018 5:50 pm
Gunnar what was the length of the F1 mast?
65cm

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Re: Holes in aluminum mast

Postby DAnderson » Tue Sep 04, 2018 8:14 pm

pj sofine wrote:
Mon Sep 03, 2018 3:08 pm
Maybe Ill experiment on the fuselage.
I've seen alloy fuselage bent as well fyi


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