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Building a hydrofoil

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don pitcher
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Re: Building a hydrofoil

Postby don pitcher » Wed Oct 30, 2013 2:22 am

Hawaiis wrote:Don:
The Titanium front wings were tested first without anhedral, they were very unstable, after adding anhedral, they are performing better than the MHL Lift wing. the frontal area is reduced to 1/3. very smooth and vibration is less than the MHL lift wing. The limitation right now is the flexing and twisting of the MHL T-Bar. I am working on a replacement T-Bar to replace the MHL lift.

I was thinking about welding two sheets of titanium to form the vertical strut of the Tbar. I need to find a welder who will weld titanium.

Helicopter Wings are subject to less force than Hydrofoils, they may not be able to cope with the stress.

Good to know the wing is working well. Keep up the good work!

In stead of welding two pieces together, could only one piece be used? One piece could be formed at the leading edge around some object, then welded the trailing edge. There would be half as much of a heat effected zone if only welding the trailing edge.

With regard to stress on the wing, you guys are making this harder than it needs to be. It is as simple as this video shows.

http://www.youtube.com/watch?v=pRLV5oeim74

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Hawaiis
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Re: Building a hydrofoil

Postby Hawaiis » Wed Oct 30, 2013 8:09 pm

"In stead of welding two pieces together, could only one piece be used? One piece could be formed at the leading edge around some object, then welded the trailing edge. There would be half as much of a heat effected zone if only welding the trailing edge."
Don: that is a great idea.

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Bille
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Re: Building a hydrofoil

Postby Bille » Wed Oct 30, 2013 10:15 pm

Hawaiis wrote:"In stead of welding two pieces together, ...

Don: that is a great idea.


Actually -- that's a Seriously DUMB idea ; carbon is a LOT better
choice for materials than metal. It's Easier to work with , and the
ultimate tensile strength is double that of Titanium . ALSO -- even with
a limited amount of knowledge, a guy can still expect some reasonably
decent results because the Carbon -- is so Damn Strong !!!

Basically, if you can understand how to laminate fiberglass, then
you can do carbon with a little extra care, (like don't breath it )
when Ya sand it. I use water, even when i saw or file or sand on the stuff.
Now i don't need a mask.

Bille

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Re: Building a hydrofoil

Postby FrederikS » Wed Oct 30, 2013 10:41 pm

Bille wrote:
Hawaiis wrote:"In stead of welding two pieces together, ...

Don: that is a great idea.


Actually -- that's a Seriously DUMB idea ; carbon is a LOT better
choice for materials than metal. It's Easier to work with , and the
ultimate tensile strength is double that of Titanium . ALSO -- even with
a limited amount of knowledge, a guy can still expect some reasonably
decent results because the Carbon -- is so Damn Strong !!!

Basically, if you can understand how to laminate fiberglass, then
you can do carbon with a little extra care, (like don't breath it )
when Ya sand it. I use water, even when i saw or file or sand on the stuff.
Now i don't need a mask.

Bille


CFRP is easier to produce, but with hand lay-up and directional mismatch taken into account the specific yield strength of the design is probably not better than a titanium piece milled to shape.

Best case scenario is perfectly aligned twill weave mat in a laminate with 60% volume fiber fraction (low porosity, VIP process) only gives you around 750 MPa yield strength (High TS quality twill weave mats used) in the 0 and 90 degree direction. The yield strength of titanium alloys is around 1000 MPa, plus it is isotropic.

don pitcher
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Re: Building a hydrofoil

Postby don pitcher » Thu Oct 31, 2013 1:56 am

Good point Frederik!

I would add that metals are easier to work with if you already work with metals or know someone that does. Also, the mess and toxicity of resin is a huge negative for some.

I am a firm believer that there is a place in this market for a low cost aluminum hydrofoil. The T-bar is the challenging part to find a way to manufacture it at a low cost.

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Bille
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Re: Building a hydrofoil

Postby Bille » Thu Oct 31, 2013 2:35 am

FrederikS wrote:...
CFRP is easier to produce, but with hand lay-up and directional mismatch taken into account the specific yield strength of the design is probably not better than a titanium piece milled to shape.

Best case scenario is perfectly aligned twill weave mat in a laminate with 60% volume fiber fraction (low porosity, VIP process) only gives you around 750 MPa yield strength (High TS quality twill weave mats used) in the 0 and 90 degree direction. The yield strength of titanium alloys is around 1000 MPa, plus it is isotropic.


NICE Reply !!!! :thumb:


Replace the Twill with, Stitched Biaxial +45/-45 Degree Carbon Fiber Fabric/Cloth 50"
12k, 815gsm. All straight fibers. The tensile strength of the Aerospace T-700 fiber
is up around, 512KSI !

Then Add some GRAPHLITE carbon rod from a pultrusion machine, down
the CG of the wings airfoil. The rod is good for tensile strengths exceeding 320,000 psi
(2070 mpa) + ,
and 275,000 psi compressive strength. Also not that bad a price for each rod.
the #'s go off the chart for a home-builder, over what he is capable with normal hand lay-up procedure.

Nothing Secret here, technology's bin around for a decade. They purposefully coat the rod
with this special ,"unobtain-ium rare-ite", so it will accept wet Epoxy .

Maybe a 1.7oz skin of Kevlar on each side for the
ding resistance. The best part is the cost is still relatively in the ball-park, for
what your getting.
AND
you can bend the caul-plate to the desired Anhedral , before making the part
(no more bending titanium).

I'm Serious here guys, this stuff ain't even a Little complicated , if you
can fix a surfboard with glass, AND fix a cabinet door ,
THEN
"You can do this" !!!!

Bille

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Re: Building a hydrofoil

Postby FrederikS » Thu Oct 31, 2013 9:15 am

Bille wrote:
FrederikS wrote:...
CFRP is easier to produce, but with hand lay-up and directional mismatch taken into account the specific yield strength of the design is probably not better than a titanium piece milled to shape.

Best case scenario is perfectly aligned twill weave mat in a laminate with 60% volume fiber fraction (low porosity, VIP process) only gives you around 750 MPa yield strength (High TS quality twill weave mats used) in the 0 and 90 degree direction. The yield strength of titanium alloys is around 1000 MPa, plus it is isotropic.


NICE Reply !!!! :thumb:


Replace the Twill with, Stitched Biaxial +45/-45 Degree Carbon Fiber Fabric/Cloth 50"
12k, 815gsm. All straight fibers. The tensile strength of the Aerospace T-700 fiber
is up around, 512KSI !

Then Add some GRAPHLITE carbon rod from a pultrusion machine, down
the CG of the wings airfoil. The rod is good for tensile strengths exceeding 320,000 psi
(2070 mpa) + ,
and 275,000 psi compressive strength. Also not that bad a price for each rod.
the #'s go off the chart for a home-builder, over what he is capable with normal hand lay-up procedure.

Nothing Secret here, technology's bin around for a decade. They purposefully coat the rod
with this special ,"unobtain-ium rare-ite", so it will accept wet Epoxy .

Maybe a 1.7oz skin of Kevlar on each side for the
ding resistance. The best part is the cost is still relatively in the ball-park, for
what your getting.
AND
you can bend the caul-plate to the desired Anhedral , before making the part
(no more bending titanium).

I'm Serious here guys, this stuff ain't even a Little complicated , if you
can fix a surfboard with glass, AND fix a cabinet door ,
THEN
"You can do this" !!!!

Bille

Yes they have a very high tensile strength in the fiber direction.

The load scenario is complex and dynamic for both the keel and the foil section, therefore you need a quasi-isotropic layout with multiple directions.

This is how much fiber directional effects compressive strength from 2500+ MPa to 600 in approximately 3 degrees offset:
Image

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Hawaiis
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Re: Building a hydrofoil

Postby Hawaiis » Thu Oct 31, 2013 9:40 am

FrederikS wrote:
Bille wrote:
FrederikS wrote:...
CFRP is easier to produce, but with hand lay-up and directional mismatch taken into account the specific yield strength of the design is probably not better than a titanium piece milled to shape.

Best case scenario is perfectly aligned twill weave mat in a laminate with 60% volume fiber fraction (low porosity, VIP process) only gives you around 750 MPa yield strength (High TS quality twill weave mats used) in the 0 and 90 degree direction. The yield strength of titanium alloys is around 1000 MPa, plus it is isotropic.


NICE Reply !!!! :thumb:


Replace the Twill with, Stitched Biaxial +45/-45 Degree Carbon Fiber Fabric/Cloth 50"
12k, 815gsm. All straight fibers. The tensile strength of the Aerospace T-700 fiber
is up around, 512KSI !

Then Add some GRAPHLITE carbon rod from a pultrusion machine, down
the CG of the wings airfoil. The rod is good for tensile strengths exceeding 320,000 psi
(2070 mpa) + ,
and 275,000 psi compressive strength. Also not that bad a price for each rod.
the #'s go off the chart for a home-builder, over what he is capable with normal hand lay-up procedure.

Nothing Secret here, technology's bin around for a decade. They purposefully coat the rod
with this special ,"unobtain-ium rare-ite", so it will accept wet Epoxy .

Maybe a 1.7oz skin of Kevlar on each side for the
ding resistance. The best part is the cost is still relatively in the ball-park, for
what your getting.
AND
you can bend the caul-plate to the desired Anhedral , before making the part
(no more bending titanium).

I'm Serious here guys, this stuff ain't even a Little complicated , if you
can fix a surfboard with glass, AND fix a cabinet door ,
THEN
"You can do this" !!!!

Bille

Yes they have a very high tensile strength in the fiber direction.

The load scenario is complex and dynamic for both the keel and the foil section, therefore you need a quasi-isotropic layout with multiple directions.

This is how much fiber directional effects compressive strength from 2500+ MPa to 600 in approximately 3 degrees offset:
Image

:thumb:

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Bille
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Re: Building a hydrofoil

Postby Bille » Thu Oct 31, 2013 8:22 pm

FrederikS wrote:...

The load scenario is complex and dynamic for both the keel and the foil section, therefore you need a quasi-isotropic layout with multiple directions.
...



That is actually an Easier lay-up , but not necessary on the lower AR foils because
we already know that 4mm thick plate of carbon will work here. Get Rid of the
carbon-rod and go with :

Stitched Biaxial +45/-45 Degree Carbon Fiber,
then add
Stitched Biaxial +0/-90 Degree Carbon Fiber, on every other layer.
Now you have Quad ; need more then arrange a third on the bias between
both, and now you got 6 directions covered. A high AR wing should
absolutely consider that carbon rod though

Do you know how much strength there is here, when i said Aerospace T-700 fiber
is up around, 512KSI ?

512KSI = 512,000-psi in the T-700 fiber.
titanium starts bending at LESS than 1/5th of those numbers.
This is a LOT stronger than your titanium, and you can do this lay-up in under an hour
but i'd make 2 or 3 at one time.

The parts will come off the caul-plate with there nice symmetrical looking bend already
in place and the holes pre-made because of the waxed pins Ya took out before
removing the part. Cutting the carbon will be easier than cutting titanium with
a band-saw.

Metal fabricating is Fun , (But) i would just as soon Leave my 38" gap-bed lathe
and drill press unplugged.

And just for a reference here :
If a Metal foil was Better, then the AC-72 would have use metal instead of carbon.
Each team had a 100-million dollar budget, and could afford Anything they wanted.
There was a Reason they went with Carbon, it's Better.
How fast does the AC-72 go ? 45kts + ; and they weigh How much ?

Bille

zfennell
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Re: Building a hydrofoil

Postby zfennell » Thu Oct 31, 2013 11:25 pm

Bille wrote:................There was a Reason they went with Carbon, it's Better.
How fast does the AC-72 go ? 45kts + ; and they weigh How much ?
Bille


I believe they said the AC-72 weighs close to 30,000lbs
pretty impressive!

Bille,
overall, I tend to agree with your choice of materials.

But i am having trouble, following the 'analysis'
Hawaiis has followed his intuition and hard work to develop a product that suits him.
You have also followed you intuition and considerable experience with composites to develop an approach that suits you.

However, despite the fact that i support your choice, i find much of the logic and math questionable.

The fiber strength of T-700 is actually quoted as high as 700 ksi (in tension)
In compession the strength drops to 350 ksi. (every tensile load in this beam example will be balanced in compression)
All these fibers need resin to tie the matrix together. A 50% ratio of 10 ksi epoxy (nominal bag process) is going to dilute the 350 ksi to 180 psi net in that particular fiber direction.
Now that you chosen to orient the fibers in an additional 5 directions the max compressive and tensile strength will be reduced even further. < 100ksi ( all because you've attempted to make this stuff isotropic?)
And none of the above addresss the shear strengh between laminates which is effectively limited by the epoxy again at 10ksi.

The benefit of the fibers is you can put them where you need them. They do very little if pointing in the wrong direction. I bet those smart guys on Team Oracle do something like that.
Iso-tropic makes the math easier, but i doubt thats a good enough reason to take a fancy composite layup and turn it into a lump of coal.

Hawaiis has covered a lot of ground on his own and so have you.

Personally the best technical advice i have to offer is:

GOOD, FAST, CHEAP.
-Pick any 2


carry on kids.


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