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 Post subject: cheapo foil setup
PostPosted: Sun Dec 01, 2013 7:51 am 
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about $5 for each wing (tried on other tbar - bit draggy but fine - 15mm ply) aluminum $60 welding $70 ?

didnt get a chance to ride it before it broke but friend got up on it but it slowly started to bend...

aluminium square section thickness too thin - choppin it off and adding a solid bar or greater wall thickness.

went for spin behind ski on another one - i was like a yoyo lol
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2013-12-01 18.28.36.jpg
2013-12-01 18.28.36.jpg [ 1.51 MIB | Viewed 1014 times ]


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 Post subject: Re: cheapo foil setup
PostPosted: Sun Dec 01, 2013 8:32 am 
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What wall thickness is too weak?
I bought some aluminum square tubes with1/8" wall thickness.


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 Post subject: Re: cheapo foil setup
PostPosted: Sun Dec 01, 2013 7:13 pm 
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Location: rhode island
longwhitecloud wrote:
...

aluminium square section thickness too thin - choppin it off and adding a solid bar or greater wall thickness.




or you could position the vertical strut on top of the front wing/foil while you work out other design details.

how much does your friend weigh?
that should help with sizing components for the future


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 Post subject: Re: cheapo foil setup
PostPosted: Sun Dec 01, 2013 9:26 pm 
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Location: Miami @ 6" Flat Butter!
Nice set-up :thumb:
But isn't the front foil has Excessive Angle Of Attack :?:

DrLW


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 Post subject: Re: cheapo foil setup
PostPosted: Sun Dec 01, 2013 10:25 pm 
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No, the picture is (must be) taken AFTER it broke/bent :wink:

8) Peter


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 Post subject: Re: cheapo foil setup
PostPosted: Sun Dec 01, 2013 11:07 pm 
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Peter_Frank wrote:
No, the picture is (must be) taken AFTER it broke/bent :wink:

8) Peter
You right, I didn't realize it was after :thumb:


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 Post subject: Re: cheapo foil setup
PostPosted: Mon Dec 02, 2013 1:51 am 
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gave it a good shot at this aoa anyway lol - fail...

gotta check wall thickness still will do then off to aluminium welders again


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 Post subject: Re: cheapo foil setup
PostPosted: Mon Dec 02, 2013 2:00 am 
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Not bad for your first prototype! Your next prototype will be much better. Here is what I think will help.

The heat from welding has annealed (weakened) the aluminum. With aluminum, this is a big change in the strength of the material.

If welding aluminum and not heat treating afterword, 5086 is nicer than 6061 because it has a much higher annealed strength.

6061-T6, 40,000 psi yield stress

6061-O annealed, 8,000 psi yield stress

5086-O annealed, 17,000 psi yield stress

From this you can see that:
* it is best to have aluminum heat treated after weld so it can be strengthened (added cost)
* or design around annealed aluminum
* or find another way to attached rather than welding

Also, I believe the aluminum from HomeDepot is 6063-T5 (21,000 psi yield stress) that is annealed to 7,000 psi yield stress at the heat affected zone of the weld.

www.matweb.com is a nice reference for material strength, but your material supplier should be the best reference.

I think if you found a way to bolt the fuselage on, it would work as you intended. Also, if you want to continue using the square tube in stead of a square solid, it might be worth getting 6061-T6.

I hope this helps.


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 Post subject: Re: cheapo foil setup
PostPosted: Mon Dec 02, 2013 2:43 am 
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thx


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 Post subject: Re: cheapo foil setup
PostPosted: Mon Dec 02, 2013 11:00 am 
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was pretty thin 2.5mm? got some 3.5 4mm? or try solid would be super strong but dont really want to buy this... expensive

gonna maybe lay down some carbon uni on strut and upright and wrap it up with glass round and round like hockey tape - make it nice n easy. i hate epoxy but might actually have to touch some , well with gloves anyway...

might add some super sized aluminium fillets at top to reduce torque too if welder doesnt decide to create a huuuge invoice..

really concentrating on cost - 2k on a foil inc postage to nz is ridiculous to me


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