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fuselage fabrication

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downunder
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Re: fuselage fabrication

Postby downunder » Wed Jan 24, 2018 2:28 am

^
Talking of what? Snow? ;)

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Re: fuselage fabrication

Postby TomW » Wed Jan 24, 2018 3:24 pm

Ive been searching around for tubes and doing some CAD modelling.

R&G composites in germany sells a 20x14 ( 3 mm wall) Plain Weave outside, and unidirectional inside. It has stated straightness of up to 2mm off straight, but they state the parts are usually way under that. (The off straight longitudinal could be aligned vertically and compensated for, but a hassle.)
1 meter costs 41.75 €
https://shop1.r-g.de/en/art/740908

Based upon what you guys are saying this should be adequate.

alternatively i can get the tubes from Easy Composites and glue several together to get it thicker than 1mm wall which is standard with them.

Anchor Inserts in UK sells really good blind M6x15 hex stainless inserts : https://www.anchorinserts.co.uk/parts/B ... p?src=tree
1.15 £ each plus shipping of 20£ ( !!)

May approach is to 3D print a mold for the wings- attach molds to backing boards, and do poor-mans prepeg into each mold half putting that into a v-bag. Then after cure de-mold them. Do any clean up if neccesary, and Put parts back into mold halves and put them together bonding halves together with epoxy- probably clamp it together. - then remove from molds again.
Once the wings are made ( big step), fabricate the fuselage from the tube . adding filler and M6 inserts using some jigs.

My fear is the mast to fuselage connection. But on other hand the LF products just bolt through the fuselage onto the flat Alu strut end. So it seems that could be done with a CF tube that is filled at that area from behind the strut all the way past the front wing.

All of this is planning- Its what i normally do to think it through before actually doing anything.

Right now i have the CAD for the front wing done, the materials to mold the wings, access to a 3D printer for making the molds.
So my first step is to make the wing molds on the printer.

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Re: fuselage fabrication

Postby Foilsnowsurf » Thu Jan 25, 2018 1:01 am

Hey, great posts and exchange of ideas here, and sources, thanks.

Just my experience, I could never get within 0.030" doing 3D printing for my wings, plus the cost of consumables. I switched to making my moulds out of corian, the scraps from counter shops are nearly free and mills really well with normal bits. By milling index points, both halves reliably join, and you can load the bottom and top shape carbon and resin, then vacuum. No extra resin, and near flawless finish in one shot. I am a diy amateur, but it works for me.

Would anyone care to comment on my fuselage plan after reading all the other ideas. I started with a LF, and still have it, but it is heavy. I want to turn a fuselage wood core on my lathe, then add the titanium flange nuts while it is easy to index perfectly, then wrap 24k tow with a 4mm build up from the front wing past the mast and tapering the build up toward the tail wing. Once wrapped, vacuum the assembly to complete it. My calculation is 20 dollars worth of tow applied under tension should do it. Anyone see a fatal flaw in this plan? I watched the video of mast making and this would allow me to apply the tow at 45 degrees with some higher degree wraps instead of uni. A minor touch up of the unloaded tips which can't be wrapped would finish the job. Would be at least half a kilo lighter than the solid aluminum LF fuselage.
Comments? Thanks, Robert

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Re: fuselage fabrication

Postby downunder » Thu Jan 25, 2018 4:49 am

Rob,

sounds ok. But, since you have a lathe it is easy to test a few pieces for you. I would just wrap it with biax in 45/45. Way, way easier than tow carbon. Tow carbon is a fcuk to work with because it needs to be slightly wetted before applied onto the surface. And that is a mess. What we do not see on the vid is how they apply epoxy. Is it industrial secret? Are they using a prepreg? Duno.

No need for 4mm walls unless you're building an indestructible torpedo :) Remember to position the wood grain properly for bending. Plenty of layers around the mast area.

Not $20, but $5 worth of carbon. The complete mast/fuselage/wing in my build is not more than $60.

Ultra light. Target is 3.5-4kg with the board.

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Re: fuselage fabrication

Postby Foilsnowsurf » Fri Jan 26, 2018 6:35 am

Hey, thanks for the input. Have you seen the Ron Gijzen windfoil build videos, I just found them. His method of shaped wood core and 200gm uni top and bottom, then all 4 sides 200gm uni, then a wrap of bias finished with a 100 gm of glass to have a sanding coat yeilded 570gr fuselage with a 22x44mm cross section. Way lighter than my 1160gr aluminum fuselage!
What size section have you been able to get down to without getting excessive flex? Tapering the tail gets limited by enough material for the wing fastener?
Does 22x26mm sound possible with an extra uni top and bottom?

First I just wanted to learn to foil, then after I could gybe and finally tack I built wings to go fast, but once I surfed thats all i want to do, the weight of fat wings and mast fuselage is a bugger to get through big shore break, so that is my incentive to get my board foil weight inertia minimized.
Comments appreciated, Robert

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Re: fuselage fabrication

Postby downunder » Fri Jan 26, 2018 8:00 am

On target;
IMG_0580.JPG

One carbon tape layer all around the wood, 5 different layers, diff angles around mast. Bolts for mast under the carbon, the idea was to be removable but epoxy went in and bonded the mast :angryfire:

Needs 45/45 biax and a stab...28mm front, 20 back diameter.

Can stand on it np...

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Re: fuselage fabrication

Postby Foilsnowsurf » Fri Jan 26, 2018 4:06 pm

Cool!! Thanks!

TomW
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Re: fuselage fabrication

Postby TomW » Mon Jan 29, 2018 3:28 pm

Have another idea, more work. How about a rectangular wood core 22wide x 26 high. Taper to ends. I'd make the wood core from laminated layers of 1,5 mm abachi, layers vertical. Rounded corners with R5. Put in inserts.
Then lay up 250 g uni D carbon on each side, 2 layers all sides. The carbon would not be wrapped, but each side. Then put 1 layer 200g plain weave over one side onto top and bottom, then on other side to top and bottom. Could look at getting a CF sleeve instead.

TomW
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Re: fuselage fabrication

Postby TomW » Mon Jan 29, 2018 3:37 pm

Yes, I'd use the sleeve as last layer.

TomW
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Moses Fluente 548/550/590/330/325
North Mono 7, 9, 12
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Location: Sweden

Re: fuselage fabrication

Postby TomW » Mon Jan 29, 2018 3:43 pm

Foilsnowsurf wrote:
Thu Jan 25, 2018 1:01 am
Hey, great posts and exchange of ideas here, and sources, thanks.

Just my experience, I could never get within 0.030" doing 3D printing for my wings, plus the cost of consumables. I switched to making my moulds out of corian, the scraps from counter shops are nearly free and mills really well with normal bits. By milling index points, both halves reliably join, and you can load the bottom and top shape carbon and resin, then vacuum. No extra resin, and near flawless finish in one shot. I am a diy amateur, but it works for me.

Would anyone care to comment on my fuselage plan after reading all the other ideas. I started with a LF, and still have it, but it is heavy. I want to turn a fuselage wood core on my lathe, then add the titanium flange nuts while it is easy to index perfectly, then wrap 24k tow with a 4mm build up from the front wing past the mast and tapering the build up toward the tail wing. Once wrapped, vacuum the assembly to complete it. My calculation is 20 dollars worth of tow applied under tension should do it. Anyone see a fatal flaw in this plan? I watched the video of mast making and this would allow me to apply the tow at 45 degrees with some higher degree wraps instead of uni. A minor touch up of the unloaded tips which can't be wrapped would finish the job. Would be at least half a kilo lighter than the solid aluminum LF fuselage.
Comments? Thanks, Robert
I don't have access to a cnc mill, but realise that cnc is the best way to mill a mold. The 3d printing will take 10 parts x 10 hrs to print.... Not a sustainable process.
So I could buy a large format Fdm printer from China for 750€ and try to do it in fewer pieces, or spend 1500-2000 € on an OX cnc kit that would do a lot more. But then have to spend a whole season building it.
I'm still thinking about it.


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