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 Post subject: Re: cheapo foil setup
PostPosted: Mon Dec 02, 2013 11:47 am 
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longwhitecloud wrote:
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

My 1/8" aluminum is only about 3mm wall thickness. Thanks for the info. I will need to reinforce the aluminum tube.


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 Post subject: Re: cheapo foil setup
PostPosted: Mon Dec 02, 2013 7:11 pm 
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longwhitecloud wrote:
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

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


A piece of 1" square solid 6061-T6 3 feet long only cost about $20. If going this route, the next weak link will be the heat affected zone on the part that it is welded to.

http://www.mcmaster.com/#standard-alumi ... ts/=pmvg4c

http://www.onlinemetals.com


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 Post subject: Re: cheapo foil setup
PostPosted: Mon Dec 02, 2013 8:22 pm 
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thx , can i get welder to anneal it by quenching in water after heating up weld area..? will that make it any stronger?

i know with absolute top range mountain bikes they weave very long carbon unis all around frame - will take ages but strengthen joins as well as tubes.. mind u i trying to avoid expense and time..

another idea is to fill upright with epoxy and a heap of chopped strand all chopped up - that would be easy as.. i think...

could make an easy mould out of upright too and then use a balloon on inside before filling

we c what happens - maybe i go to wood if ally fails - nice and healthy...


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 Post subject: Re: cheapo foil setup
PostPosted: Mon Dec 02, 2013 8:37 pm 
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And Ya got some data from your work before it broke ; that's Always good !!

If adding carbon to metal, then you will need
one layer of 4oz glass between the two to address that dissimilar-metals thing,
otherwise there will be corrosion in the metal part.


longwhitecloud wrote:
...

we c what happens - maybe i go to wood if ally fails - nice and healthy...


Wood is Good and Cheap ; and if Ya add a bit of carbon to , it would
be Way strong ; kinda don't think there's a Cheaper way to go , and still
insure a decent odds for success ! Ultimately, if a guy wanted to build a Cheap
hydrofoil for production, i don't think there is a better way to go than wood & carbon.

Shaping the same part from wood and repeating it 200 times , doesn't require
a lot of Expensive machine tools ; most of that equipment can be hand made , which
helps to keep the production cost down. Look at the tooling that --windfreak74-- made
on page 10 , in the thread : " DIY Home Made wooden Hydrofoil fins" .
about 1/2 way down here :
viewtopic.php?f=196&t=2382338&start=90

Hawaiis is responsible for my new way of thinking about wood ; i'm still adding
carbon though.


Bille


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 Post subject: Re: cheapo foil setup
PostPosted: Mon Dec 02, 2013 10:59 pm 
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Location: rhode island
longwhitecloud wrote:
thx , can i get welder to anneal it by quenching in water after heating up weld area..? will that make it any stronger?

i know with absolute top range mountain bikes they weave very long carbon unis all around frame - will take ages but strengthen joins as well as tubes.. mind u i trying to avoid expense and time..

another idea is to fill upright with epoxy and a heap of chopped strand all chopped up - that would be easy as.. i think...

could make an easy mould out of upright too and then use a balloon on inside before filling

we c what happens - maybe i go to wood if ally fails - nice and healthy...


for example.
if the center of your front foil is 6 inches in front of the strut and your rider weight is 200 lbs
tube moment at strut is 100 ft-lbs (1200 in lbs)
stress=M*c/I

stress for 1" square tube (1/8 wall) = 10, 500 psi
if your alloy is 6000 series, T-0 (butter) its probably started to go at 8000 psi
if the alloy was closer to T-6 and you bolted the tube to your strut, it would go to 20,000+ psi
and you'd still be riding.

stress for solid wood (1x1) = 7,200 psi.
lots of hardwoods have flexural strength of 10,000-12,000 psi
if the wood was 1 x 1.25 the stress would only be 4600 psi and you'd have the same factor of safety as the T-6 model

just food for thought.
-bill


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 Post subject: Re: cheapo foil setup
PostPosted: Mon Dec 02, 2013 11:39 pm 
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cooool , some interesting engineering stuff there. I fully encourage less expensive equipment and environmentally friendly technology - you cannot encourage youth into sport then stump them with the fact that 3 kite and a foil board costs over $10k..! kiteboarding is lucky - the performance offset of really expensive kite vs less expensive kit is not that great

not a market i really want to get into as so small, but i am considering asking one of the factories i used to work with in china to make a foil for me - so many potential f#$@ ups tho... i reckon abs injection moulded wings, wooden t bar with glass to keep cost down - or aluminium with glass maybe..

will need to c performance difference of thicker profiles - drag probably will be its downfall as i turn more fussy- those rush randle foils - thin metal wings are very fast my tow friend says (u need that for towing big waves -getting up to speed on tow) but a bit scary chop chop...

good measure is how hard you need to hold on behind a ski or boat - he can ride it with ski rope in teeth!!!


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 Post subject: Re: cheapo foil setup
PostPosted: Tue Dec 03, 2013 6:49 pm 
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longwhitecloud wrote:
thx , can i get welder to anneal it by quenching in water after heating up weld area..? will that make it any stronger?


This works for steel, but not aluminum. Steel is quench hardened using water, oil, or air depending on the alloy. Aluminum is precipitation hardened, which is an aging process at certain temperatures.

Like Bill showed, if you use 6061-T6 and bolt it on, you should be riding.

For strength purposes, you might want to cut off the heat affected zone on the part that the fuselage was welded to.

Keep going and you will be riding soon!


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 Post subject: Re: cheapo foil setup
PostPosted: Tue Dec 03, 2013 8:45 pm 
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Location: Miami, FL
What about g10 for the foils not upright it's strong stiff and not that pricy and easy to shape. Thats my thought anyway for eventually making a high aspect foil for the mhl once I learn to ride.


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 Post subject: Re: cheapo foil setup
PostPosted: Wed Dec 04, 2013 6:31 am 
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longwhitecloud wrote:
...

will need to c performance difference of thicker profiles - drag probably will be its downfall as i turn more fussy- those rush randle foils - thin metal wings are very fast my tow friend says (u need that for towing big waves -getting up to speed on tow) but a bit scary chop chop...
...


Yea ---Drag ; it's a Biggie !

It's one reason i don't agree with those 20% thick airfoils on the strut ; just Too damn Slow !!!

Bille


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