brancing bipes

[Daniel Z]

I would like to build a cdrom powered bipe but, to keep it light I want to brace it to use no carbon; can anyone have a diagram or tutorial to do it right?

Thanks

[matchlessaero]

Daniel, unless you plan to use Kevlar thread instead of Carbon(or some other replacement material), I don't see it happening.

[Pistolera]

Daniel,
I think you could easily do this with Kevlar thread. Attached is a very simple drawing showing where I would run the thread in the wings. You'd basically end up with "X" bracing when looking from the front and also from a plan view.

With a needle and thin Kevlar thread you can go through your foam and around or anchored to either a small piece of toothpick or through small plastic grommets you can easily make with a paper puncher.

bTW - good and cheap Kevlar thread (called K-thread) can be found in a sporting goods store catering to fly fishing. I just bought several 50' spools for $1.99 each....various colors too :rolleyes:

Earle

[racerxky]

The Aito and Phaser biplanes use this technique. You can see the diagram of how to do it in their manuals online:
Aito Manual (http://www.donuts-models.com/notice_aito.pdf)

Look on page 4. The text says (according to google translate):
"The staying wire is done according to diagram opposite. It is carried out in two stages (once for quantify and once for els letters). Do not tighten wire during the staying. once it finished staying, pose the wing flat and tend slightly so to have a total flatness of the two wings. Point each passage of wire with a small drop of cyano."

This results in a very stiff wing. They dont cross the threads like the previous diagram. So now you have two suggestions.

[Pistolera]

The Aito and Phaser biplanes use this technique. You can see the diagram of how to do it in their manuals online:
Aito Manual (http://www.donuts-models.com/notice_aito.pdf)

Look on page 4. The text says (according to google translate):
"The staying wire is done according to diagram opposite. It is carried out in two stages (once for quantify and once for els letters). Do not tighten wire during the staying. once it finished staying, pose the wing flat and tend slightly so to have a total flatness of the two wings. Point each passage of wire with a small drop of cyano."

This results in a very stiff wing. They dont cross the threads like the previous diagram. So now you have two suggestions.
Anyone know where to get a complete English translation of this manual?

[Trisquire]

I would do the bracing as follows:


Design the interplane struts and/or CFGs so they are as wide as the wings
Glue on thin plywood "hard points" at the thread attachment points
Put the plane in a makeshift jig
Secure the thread to the starting point with glue
String the thread around the wings in one continuous loop
Secure the thread to the ending point with glue


Tom

[Bryan Davison]

My question is ....WHY?

Your only gonna save at most about 6g by leaving out the carbon spars.

A better option would be to switch from the 3mm strip to a 2mm rod. It should save a few grams, and then you can use kevlar thread to brace everything. The Radix 3d uses 2mm rods for the wing spars and this is on 1.3mm depron. Now that Ive built mine, its plenty rigid. It came in at 165g.

I think Im gonna use this technique in my next plane. Im hoping to have a sub-150g plane in the next few months.

[racerxky]

Anyone know where to get a complete English translation of this manual?

I just copy and past bits into translate.google.com (http://translate.google.com). I don't know of a full english version.

[Daniel Z]

I dont have depron in my location, so I build with EPP, an it is not a bad thing because 10mm epp is lighter than 3mm depron and have more body (and drag), I can make a very stiff wing ( no flex) with balsa "T" shaped spar reinforcement but it can´t avoid twisting and I want a solution to use less glue, if it saves me 6 gms I think it worth

[Daniel Z]

thanks for your answers!

[racerxky]

I can make a very stiff wing ( no flex) with balsa "T" shaped spar reinforcement but it can´t avoid twisting and I want a solution to use less glue, if it saves me 6 gms I think it worth

That is very cool! I have been thinking about building with a mix of Depron & EPP. You beat me to it, you should do a writeup!

[flypaper 2]

I use dental floss for flying, landing wires. 1/2 in sq. of 1 /32 ply for hardpoints. Very tough stuff.

[Pistolera]

I use dental floss for flying, landing wires. 1/2 in sq. of 1 /32 ply for hardpoints. Very tough stuff.
I have too, but also find that it gets slack with changes in humidity. Kevlar thread does not seem to be affected in this way.

[flypaper 2]

Don't seem to have a problem with humidity. This is the waxed stuff. Don't know whether that makes a difference or not. I found after the first few flights it will stretch. So I tighten it up and they stay tight after that. This weighs 168 grams and 30 in. wingspan. I scratchbuilt it to fly in a sportsdome in the winter. I call it *catsas* Little Screamer to haul it around.

[Pistolera]

I've used the unwaxed floss, which ties nicely and glue sticks well. Does glue stick to the waxed stuff???

[matchlessaero]

Another material worth trying is Spiderwire fishing line. The 50lbs test with teflon coating is tough and does not stretch too much. You can secure it with CA- using some accelerator does make it hold better.

[flypaper 2]

At the time I started using it I didn't know there was a difference. Someone mentioned that it wouldn't stick. but CA works fine on it. When I tighten them I have to break them loose with a bit of persuasion, then reglue.

[theKM]

The kevlar flying wires on my Troll is the only thing keeping it straight and flyable. She's been an abused machine, but the flying wires manages to keep the whole thing strong enough for flight. Anyone playing with their own designs need to note that the flying wires also rely on the interplane struts to keep the wings separated. I've just used a single line of the thinnest thread, and it's stood up well without slacking.

A great place to get the thread is on ebay. Many auctions, with some cheaper by length than others. The thread without the wax is most preferred as it'll soak up the CA better.

[Daniel Z]

hummm that`s an issue... I`ve thinking on a way to re tight without much persuasion ;)

[flypaper 2]

What I meant by a bit of persuasion was that it won't break loose on its own. :p Not hard to pull it off the mounting plate and reglueing it.

[avianaut]

I can vouch for the kevlar fishing line. I use it with 1/64" ply anchors and I have no spars at all, and no wing bending problems. I'm thinking of using it on mono wings as well, and I've seen it used to brace the fuselage to eliminate twist.

Cheers.