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Old Jan 23, 2013, 10:43 AM
slopehunter
Joined Dec 2008
4 Posts
Help!
need opinions about my Layups

Hello

Since i have to produce a couple of wings and don't like the conventional way with wood covered foam cores, i decided to bag them. I ordered and carefully studied Phil Barnes DVD and think i am ready to give it a try.

Since my understanding of the whole composite stuff is very basic, i am a bit lost what layups will work for my wings. I will definitely start to learn more about it, but building this wings is more important at the moment. I should build them as long as the weather is cold and snowy and allows long nights in the workshop.

I experimented a little with the bagging layup spreadsheet of Jay Decker which i found here: http://www.rcgroups.com/forums/showthread.php?t=1213427

I decided to build with carbon and glass because i wont use kevlar until i am more familiar with the bagging method. I also want to avoid anything below 160g/m2 (4,72oz/yd2) carbon since ist too expensive, especially if something goes wrong with the bagging. I will describe the planes and the intended layup and hope for some input and opinions. I have absulutely no feeling what it really needs. My flying style is rather smooth, i like to fly fast but donít like to paint corners in the sky at Vmax.

Ah yes the foam is something like blue Roofmate. Very hard.

1)Minius
Its an old little 1,5m (50") glider that was sold as a small hotliner. The wings are beaten up, so i will build new ones. I think they are perfect for my first bagging project. Airfoil will be an MH43.
I put a weight of 2,2kg (70oz) and a max speed of 40m/s in the spreadsheet and came up with a layup (equal on both sides) of

-49g/m2 (1,45oz/yd2) Glass Bias surface layer
-160g/m2 (4,72oz/yd2) CF Bias
-capped CF-spar 0.5mm x 10mm

opinions? I think its more common to use 25g/m2 (0,75 oz/yd2) Glass for the surface, but the other is simply easier to work with. The spreadsheet thinks the spar is necessary, but i think it would also work without. The original wing is very basic, just balsa or abachi covered styrofoam without spar.

2)Hotliner
Kind of a 15 year old RG15 F5B plane wing with 1,8m (60") wingspan.
I put a weight of 2,2kg (70oz) and a max speed of 40m/s in the spreadsheet and came up with a layup (equal on both sides) of

-49g/m2 (1,45oz/yd2) Glass Bias surface layer
-160g/m2 (4,72oz/yd2) CF Bias
-capped CF-spar 1mm x 10mm

I shredded the original wing by trying a roll too low. It has a thin layup with carbon and a layer of 0.5mm balsa. No real spar but kind of a shear web. Just a carbon hose around a 10x10mm piece of foam.

3)Jart
Should be a well known lead sled type glider for the windier days. 50" wingspan. One wing will have a S6062 and the other an Ayers DA7017 airfoil with just 7% thickness. it's going to be very heavy and should be very stiff.

-49g/m2 (1,45oz/yd2) Glass Bias surface layer
-160g/m2 (4,72oz/yd2) CF Bias
-160g/m2 CF straight
-capped CF-spar 1mm x 10mm

4)Rebuilt of an old F3B wing (Tragi 702)
I loved to fly this ship but lost it because the thermal ghosts went to coffe break while i was flying. I still have a set of V-Tails and an easy to repair fuse. I just need to rebuild the wing. The construction is probably 15+ years old. The wing was quite heavy, approx. 1500g (50 oz). Wingspan is 3m (100")

The spreadsheet tells me :
-49g/m2 (1,45oz/yd2) Glass Bias surface layer
-160g/m2 (4,72oz/yd2) CF Bias
-capped CF-spar 2.5mm->1mm x 12mm
Opinions ? How would you layup a wing like this ?

Since iím not looking forward of soaking miles of rovings for all those spars, are there any alternatives ? Probably a layer of UD carbon in addition?

Thanks for all suggestions! I hope my weight conversions are correct...
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Old Jan 23, 2013, 01:06 PM
Entropy is happening!
Jim.Thompson's Avatar
Bellingen NSW Australia
Joined Aug 2008
6,466 Posts
Carbon.

My first thoughts are: put your carbon in the cupboard and do your first dozen or so vac bag jobs with glass fabric!
Good strong wings can be built with all glass except for the carbon tow spars.
Carbon is expensive and is more difficult to use correctly than glass. Plain weave glass is a fraction of the price. My favourite is a tight weave 76 gsm and a 100gsm. A good wing can be vac bagged over foam using two layers of 76 gsm glass, one only on the bias. Not two! With or without a veil layer.
My favourite LE for slope gliders is Aussie hardwood. I don't know where you are, but you will find something equivalent most places.

I hope the two Jart wings are two pairs of wings and not two wings of the one set!

Jim.
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Old Jan 24, 2013, 05:23 AM
slopehunter
Joined Dec 2008
4 Posts
Thanks, Jim

wood is not an option since it's hard to get good(!) wood in Switzerland and its also damn expensive. Even carbon is a bargain compared to quality wood in the size of a wing. In addition, the cores are already cut for covering with thin fabrics instead of thicker wood. I know that wood covered wings are much more rugged than carbon or GF wings, but this time i want to try composite.

CF is in fact expensive, but not unaffordable. For what plane size would you recommend the described GF layup?
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Old Jan 24, 2013, 03:20 PM
Entropy is happening!
Jim.Thompson's Avatar
Bellingen NSW Australia
Joined Aug 2008
6,466 Posts
Quote:
Originally Posted by Horbach View Post
Thanks, Jim

wood is not an option since it's hard to get good(!) wood in Switzerland and its also damn expensive. Even carbon is a bargain compared to quality wood in the size of a wing. In addition, the cores are already cut for covering with thin fabrics instead of thicker wood. I know that wood covered wings are much more rugged than carbon or GF wings, but this time i want to try composite.

CF is in fact expensive, but not unaffordable. For what plane size would you recommend the described GF layup?
There may have been a misunderstanding. I did not mean to cover the wings with wood. I was referring to a thin strip (typically 9mmx9mm dressed), which is glued onto the LE after cutting a small amount off to accommodate it. Then it is shaped. Start with a power planer, then hand plane followed by long sanding blocks. Finally, strips of folded sand paper in crossed diagonal directions. Can be done quite quickly with some practice. Check on the price and availability of 9mmx9mm dressed hardwood in your local hardware store. I would be interested to know actually. From memory, it costs about $5 for a 2.4 m length here. I'll check next time I'm in the store.

What size plane?
I have used that light layup on a 1800 mm span slope glider, but with a doubler of the same cloth for approx. one third to half span. This glider has flown for years and gets some hard flying on a big air slope. It has graduated carbon tow spars though. I cut a slot for them in the foam with my little router. Cheap and durable. The hardwood LE have proved there worth after several encounters with foam and harder planes.

Just to re-iterate. The fibre orientation of the cloth layers are usually alternated. ie.: One 0/90 deg. and the next 45/45 etc.
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Old Jan 25, 2013, 02:17 PM
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Tehachapi Jim's Avatar
United States, CA, Tehachapi
Joined Jul 2004
1,344 Posts
Another technique that was passed on to me was to used thickened epoxy (splooge) over two layers of bias cut aramid on the LE. I just used a plastic baggie to put the splooge in and cut a corner of it to apply it. I tried it on obechi Elf wings and it works far better than I thought it would, if done right it requires minimal sanding too.

I realize its probably not as shock resistant as a good hardwood LE, but it is a nice middle ground and easy to do, FWIW.

I will try to post some pics of the finish sanded wing later if you want.

Jim
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Old Jan 25, 2013, 02:48 PM
Master of the Wind
G Norsworthy's Avatar
United States, CA, San Jose
Joined Sep 2008
1,151 Posts
The Tragi wing I would do like this.
http://www.rcgroups.com/forums/showt...hlight=triniti
I suggest you study the Supra plans in detail and make something in between the Supra and what I did, which is overbuilt for big air, man on man slope racing.
A bagged 60" should not need a spar if you include a uni layer. Just make sure you have a good design to support the wing tubes. If there are servo cutouts in the wing, these are weak spots and for that reason a spar is not a bad idea to carry the stress.

The heavier glass skin coat should be fine, especially if you are painting the mylars first.
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Old Jan 29, 2013, 07:33 AM
slopehunter
Joined Dec 2008
4 Posts
Hello G Norsworthy, thanks for the link! I just overflow it, have to read it more carefully later. Just one question: What does E-Glass and S-Glass mean?
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Old Jan 31, 2013, 10:15 AM
Composites guy
North OC, Ca.
Joined Jun 2005
1,172 Posts
E= "electrical" but is the most common grade of fiberglass cloth in production today.

S="structural",(typically S-2) high strength/stiffness compared to E and C glass but more $ and lower availability. I use it when I can get it.

Glass fabrics have high strain to failure( up to 7%) which helps spread load and reduce fiber fracture ( for comparison carbon is 1.4%- no flex and then, snap).
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