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 Post subject: Re: Building a hydrofoil
PostPosted: Sun Nov 03, 2013 11:12 pm 
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Why are you using a symmetrical foil ?
It is by far the least effective foil during lift, even low lift.
It will work fine, yes, but only disadvantages compared to a slightly cambered foil.

Depending on the speed and it's size.

The torsional forces will be a bit larger, but that's why we have a tail wing.

There are other methods to decrease the force and get less drag, if wanted.

8) Peter


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 Post subject: Re: Building a hydrofoil
PostPosted: Sun Nov 03, 2013 11:44 pm 
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Peter_Frank wrote:
Why are you using a symmetrical foil ?
...

8) Peter


I'm building the Pylon, (tower), ((supporting structure that ties the body and foil
assembly, to the bottom of the surfboard)), usually 95cm in length.

I need the length of the airfoil of the above part, should be around 110mm
from the Le to the TE.

Bille


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 Post subject: Re: Building a hydrofoil
PostPosted: Mon Nov 04, 2013 4:09 am 
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Location: rhode island
Bille wrote:
...... I need the length of the airfoil of the above part, should be around 110mm
from the Le to the TE.

Bille



so..
Fasta, Christoff and you have chosen a 12% foil
Fasta is willing to sell you a 100mm chord length to do the job.
Christoff suggests a thickness of 14-20 mm resulting in chord length of 116-166 mm.

All will work, assuming your layup does not exceed the material properties.
At least Fasta has given you a goal for wall thickness, weight and resin content.
Perhaps they will provide some details to all the fiber orientations?

Everyone has said what can happen, few have said how to guarantee success.
copy your favorite recipe or see if the math supports your own concepts.

depending on your level of uncertainty, go bigger if you need to.
dont fill the center with carbon because your not sure what the stress is.
you will buy more by moving material to the outside.
imo


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 Post subject: Re: Building a hydrofoil
PostPosted: Mon Nov 04, 2013 3:54 pm 
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Bille wrote:
Peter_Frank wrote:
Why are you using a symmetrical foil ?
...

8) Peter


I'm building the Pylon, (tower), ((supporting structure that ties the body and foil
assembly, to the bottom of the surfboard)), usually 95cm in length.

I need the length of the airfoil of the above part, should be around 110mm
from the Le to the TE.

Bille



Billie,
not entirely sure how your doing your mold from your earlier description, but I found the easiest way to make a two piece mold is to start with 2 matched pieces that are foiled on one side and flat on the other, this way you can lay them up on any flat surface. I was a little concerned trying to get a clean parting line would be difficult especially with a thin leading and trailing edge.

You definitely have more mold making experience than me. So you probably have this sorted. But this worked very well for me with NO mold making experience

viewtopic.php?t=2375299&p=784435
I made a NACA 0010 with 10cm chord and 1 cm thickness. x 50 cm long.... So pretty much the same dimensions just shorter.....You could get the foam cutters to make you 2 mirrored bits of foam (your desired foil cut in half) ..........

The thicknesses we're dealing with are REALLY thin though. EPS would be difficult to work with so maybe starting with the completed foil is the right way to go.

bugger I didn't think to make my mold longer coulda used the mold for a pylon ......got the raceboard 1/2 finished....now they're outdated.

I'll definitely use those foam cutters in the future....cutting the foam accurately was the hard part. Thanks to whomever posted the link.


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 Post subject: Re: Building a hydrofoil
PostPosted: Mon Nov 04, 2013 4:39 pm 
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Johnny Rotten wrote:

......You could get the foam cutters to make you 2 mirrored bits of foam (your desired foil cut in half)

...
bugger I didn't think to make my mold longer coulda used the mold for a pylon ......got the raceboard 1/2 finished....now they're outdated.

I'll definitely use those foam cutters in the future....cutting the foam accurately was the hard part. Thanks to whomever posted the link.


That is Exactly what i'm going to do ; get a foam cutter to make me two 1/2's ; then
stabelize the foam with (3) layers of 3oz glass , and tie them to a stiff wood box.

Since i break stuff kinda Easy compared to most other people, i thought
110mm cord
wasn't gonna give me a thick enough pylon, (mast) to guarantee success, so i decided to go with a
120.6mm cord length.
That gives me a 14.4mm thickness, or 0.56". Now i can use 1/4" Nomex-honeycomb core
if i want ; and just happen to have a Bunch of it.

I'll make this mold 111cm long, so i have a Lot of options as to length.
I Absolutely wanna make this thing modular, so all the parts can be interchanged ; meaning
that i Could go to the lake with Two different size pylons like 60cm and 95cm. Might
be good to learn on a shorter mast length anyway ?

Bille wrote:
...

I'm building the Pylon, (tower), ((supporting structure that ties the body and foil
assembly, to the bottom of the surfboard)), usually 95cm in length.

...

Bille


Anyone ever decide on the actual Name of that part ?
Pylon
Mast
Tower
Shaft
Support structure ------------------other.

Over on that thread :
Post subject: Re: Can a hydrofoil be shorter than current design?
C A R A F I N O called it a Shaft ; but the topic starter called it a Keel.

It is Definitely NOT a Keel ; the Keel of a boat runs lengthwise down
the hull, and is usually the lowest part in the hull, and runs Horizontal, or
parallel to the water surface.

Bille


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 Post subject: Re: Building a hydrofoil
PostPosted: Mon Nov 04, 2013 7:38 pm 
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Location: Langebaan (Cape Town)
I agree, we have to find a good name for the mast/keel/pylon/shaft. I think it is new enough to deserve a new word, maybe the military hydrofoil ship developers had some name for that part from decades ago?

For now I actually prefer to stick to the word keel. If I look at the wikipedia definition http://en.wikipedia.org/wiki/Keel then I think it is probably the closest word to describe it although not 100% the same. It is part structural, part hydrodynamic, see similar forces (although opposite direction) and sits in the same position as a boat keel. I think the word keel fits it well enough unless anyone has a much better suggestion?

I am happy to use the word keel, give it a slightly new meaning, but use the same word. Most people would know what you are talking about if you say keel, whereas most other words are not so obvious.

Just my thoughts.

On another note: what do we call the main body between the wings? I'm going with the word fuselage for now. I am happy to be corrected if anyone has some evidence to support whatever new word they propose.


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 Post subject: Re: Building a hydrofoil
PostPosted: Mon Nov 04, 2013 8:55 pm 
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Mast (or keel)
Fuselage
Front wing
Tail wing

:thumb: Peter


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 Post subject: Re: Building a hydrofoil
PostPosted: Tue Nov 05, 2013 12:43 am 
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In the fabrication world, it would be called a riser. The ski-boat hydrofoil world uses the word T-bar.

People use hydrofoils on windsurfers. They can't have two different parts with the same name, mast. :o

I don't think it is a mast (like in sailing or windsurfing) or a keel. It is a riser. :D


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 Post subject: Re: Building a hydrofoil
PostPosted: Tue Nov 05, 2013 1:41 am 
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ChristoffM wrote:
I agree, we have to find a good name for the mast/keel/pylon/shaft. ...

...

On another note: what do we call the main body between the wings? I'm going with the word fuselage for now. ...


Yes for the fuselage !!!


Peter_Frank wrote:
Mast (or keel)
Fuselage
Front wing
Tail wing


:thumb: Peter


Yes for the Front, (or Main) Wing ; like they call it in an airplane.
And the vertical thing-ie in the rear ; that would be the Rudder !!

Yes also for Tail wing.

don pitcher wrote:
...

I don't think it is a mast (like in sailing or windsurfing) or a keel. It is a riser. :D


I Like the name Riser ;
Tower would work also . And your Correct about it NOT being called a Mast ; too
many parts by the Same name .

C A R A F I N O called it a Shaft ; so i may refer to it as a , "Riser-Shaft" from now on,
just out of Respect !!

Bille


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 Post subject: Re: Building a hydrofoil
PostPosted: Tue Nov 05, 2013 2:09 pm 
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On boats with hydrofoils it is called a strut.


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