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 Post subject: Carbon Foil Build
PostPosted: Wed Jan 01, 2014 8:36 am 
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Joined: Sun Jul 15, 2012 9:32 am
Posts: 87
Location: Tauranga, New Zealand
Hey guys,
After countless concepts designed in cad, researched and talked about, I thought that I would just design and make a semi normal carbon foil.

So being a poor uni student, the main foil was originally going to me made out of sh*t loads of 6mm mdf sheets. A 3 axis cnc would simply cut out the shapes out of a sheet of mdf, they would then be glued together to create a top surface and bottom surface, which would then be sanded and molds to be made from.
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this had a few disadvantages in terms of what shape of foil could be made for instance curving down and backwards was impossible. I ended up finding a cnc shop with a 5 axis that had enough time to cut molds a few days before Christmas and let me pick up on boxing day :D
the profile is a modified eppler profile that had its top curve and bottom curves scaled differently.
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~end result
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Day 1:
~A few of us spent the day figuring out the best way to mold the main wing, since it is a 1 off, went for the normal method of molding 2 halfs, routering/grinding flat then joining.
final result is a bulletproof 10 layers of carbon. (various types). maybe a bit overkill considering we did a test with a offcut of nomex that had 1 layer each side that could support 90kg and only broke when jumped on.

~the carbon was laid up and other than the first 2 layers, cut perfectly to fit.

~went for a solid carbon fuselage quite a bit smaller than regular... max width is 16mm but is crazy solid!
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Day 2:
~the main wing was vacuum bagged, mold didn't move or collapse on any of the corners which is a bonus.
~stabiliser will be shaped out of some nice 5mm solid carbon (also crazy stiff), just rough cut to shape.
fuselage was routed for join to fit in.
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Day 3:
~not much happened, the hungover vacuum bagging actually turned out all right. Foil got a rough cut around the edges, then more carbon! cut carbon to shape and layered both sides then chucked in the mold. A layer of glad wrap was in between each half so that they can be separated after and all voids can be filled up, sanded then finally glued together.
quite heavy now but I don't think it will have any flex what so ever :D

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Surface finish wasn't the best due to mold. MDF or a better foam would have been nice, but then that would have cost $1000 NZD :roll:

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*update

Day 4:
~simply glued the 2 halves together and did some prep work on the stabilizer support

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Will continue to update when anything happens!

Update*

has been a bit tidied up since these photos, but the general idea is there!
Stabiliser is roughly shaped by hand, no proper foil shape. )':
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Last edited by Bradn on Tue Feb 18, 2014 11:40 am, edited 3 times in total.

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 Post subject: Re: Carbon Foil Build
PostPosted: Wed Jan 01, 2014 10:46 am 
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Joined: Wed Aug 24, 2011 11:39 am
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Nice, keep up the good work


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 Post subject: Re: Carbon Foil Build
PostPosted: Wed Jan 01, 2014 11:03 am 
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Joined: Tue Jul 19, 2011 5:26 pm
Posts: 194
Location: Langebaan (Cape Town)
Very nice build! Thanks for sharing.

One tip I can give is to put the foil upside down and feel where it flexes. You should be able to put quite a bit of weight on any part of the front or back wing without it flexing more than a few centimeters. I do not know how stiff your fuselage is, but by the look of the diamter near the end my guess is that the fuselage is maybe a little bit too thin. It should be easy to add a bit of carbon over if you find it flexing too much.

Good work, well done.


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 Post subject: Re: Carbon Foil Build
PostPosted: Wed Jan 01, 2014 4:52 pm 
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:bravo:
seriously impressed, well thought out
Quote:
So being a poor uni student,


Engineering student I hope.....great project.


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 Post subject: Re: Carbon Foil Build
PostPosted: Wed Jan 01, 2014 10:54 pm 
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Joined: Tue Mar 23, 2010 1:16 am
Posts: 325
Location: Chile/Brasil
Wow!!impressive!
Please keep posting pics as you advance :thumb:


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 Post subject: Re: Carbon Foil Build
PostPosted: Thu Jan 02, 2014 7:47 pm 
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Joined: Sat Dec 29, 2012 2:59 am
Posts: 161
Nice work. Looking forward to seeing more. I'm especially interested in how you join the two wing halves. I've been wanting to get a similar mould made, but I'd love to make a "solid" or single layup wing and can't quite work out how to do it. Model glider builders use a bladder to push the two skins apart, but I was thinking of a compressible core that you wrap and put into the mould. Anyone tried anything like that before?


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 Post subject: Re: Carbon Foil Build
PostPosted: Sun Jan 05, 2014 12:19 am 
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Joined: Sun Jul 15, 2012 9:32 am
Posts: 87
Location: Tauranga, New Zealand
ChristoffM wrote:
You should be able to put quite a bit of weight on any part of the front or back wing without it flexing more than a few centimeters.
Good work, well done.

How much loading is on the stabilizer? surely it's nothing compared to the front?
So you mean once it is fully assembled, stand on it and check for flex?
It's surprisingly stiff, so hopefully it doesn't need any reinforcement, otherwise a few strips of uni should help it out. :thumb:

Johnny Rotten wrote:
Engineering student I hope.....

Spot on :mosh:

ozchrisb wrote:
I'd love to make a "solid" or single layup wing and can't quite work out how to do it. Model glider builders use a bladder to push the two skins apart, but I was thinking of a compressible core that you wrap and put into the mould. Anyone tried anything like that before?

1; The bladders aren't the best at getting any decent pressure on the inside of the mold, also the wings are quite small, so wouldn't be able to get to the ends or edges too well.
2; we thought about the foam core option, but it might not get even pressure on all parts of the wing, perhaps if you cnc'd a slightly scaled wing out of foam somehow, (e.g 2 foam halves flat then glue and curve to shape) or made a scaled mold to fill with a softish expanding foam.?
3; option we wanted to do (but were limited with foam mold) was laying up all the carbon and infusing - the epoxy would reach everywhere and the carbon could expand to put a little bit of pressure on molds.

anyone have any bright ideas on how to join the stabilizer? easy option is making it solid, but would ideally like to change the angle of it on the beach. hard when the section it is on top of is only 5mm wide :o

Also looking for ideas on how to make the mast, preferably without use of a cnc (no moneyz)


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 Post subject: Re: Carbon Foil Build
PostPosted: Sun Jan 05, 2014 5:24 am 
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Bradn wrote:

Also looking for ideas on how to make the mast, preferably without use of a cnc (no moneyz)


I built a 50cm foil this way would do it again for a 1m mast.

http://www.kiteforum.com/viewtopic.php?f=107&t=2375299&p=784435&hilit=making+fins#p784435
No serious investment other than the tooling gel coat. which you can hopefully beg borrow or steal from somewhere.

another dude made a nice wood foil mast using a router sled here.


other guys take a chunk of G10 a hand grinder get the initial profile right and then try to keep the lines straight.


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 Post subject: Re: Carbon Foil Build
PostPosted: Tue Feb 18, 2014 4:08 am 
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Joined: Sun Jul 15, 2012 9:32 am
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Location: Tauranga, New Zealand
Hey Johnny,
thanks for the mast ideas, I will hopefully have access to a cnc machine soon so might be able to make a good mould up, Thought that since it will use quite a bit of carbon ($40) it may as well be the correct shape and be useful in other builds.

does anyone know what a good mast profile would be?
thinking naca 63 010a , 1cm thick, 10cm wide. maybe tapering as it gets higher for strength + curving to stop ventilation all the way up the mast. any thoughts would be appreciated. :D


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 Post subject: Re: Carbon Foil Build
PostPosted: Tue Feb 18, 2014 7:59 am 
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Joined: Thu Jan 16, 2014 9:28 am
Posts: 31
Location: Ukraine
for my hydrofoil I use Eppler e836


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