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Old Feb 03, 2012, 01:16 AM
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Build Log
Epic Win - 2m flying wing electric glider

I've been wanting a big flying wing for a long time now and have been developing techniques of folded foam wings so that one day I'd be able to build one. But after having looked at the newspaper covering threads I thought I could build one strong enough with foam core, newspaper and glue.

To offset the weight penalty of newspaper I'm using plain old styrofoam - the cheap beaded kind. Hopefully it will not warp when covered with newsprint. I have a few ideas that I think would minimise warping but since this is the first time I'm doing this I don't know if it'll work. To add to the complication, this is also the first time I'm building a wing with a hot wire cutter.

So I'm calling it Epic Win - which is what I hope it will be. Basic design is a simple constant chord wing with 2m span and 20cm chord. That should give us 40dm^2 so my weight budget is around 400 to 500g.

Here's a link to the CG calculation: http://fwcg.3dzone.dk/?wing_span=200...ow_mac_lines=0
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Old Feb 03, 2012, 02:47 PM
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OK, I've cut the cores and joined the wing segments. This will be a two piece wing since I don't have any practical way to transport anything 2 meters.

The airfoil is HS522 but it'll probably end up as a very inaccurate approximation of HS522. Still need to work out kinks in my hotwire techniques. I cut the wings with built-in twist but a quick glide test showed that it may not be sufficient. I'll most likely remedy that by cutting the elevons at an angle so I can add twist using trim.

I've temporarily marked flap and elevon locations to figure out how I want to do it. Still haven't decided on weather I want the elevons to extend all the way to the tips. My previous planes with elevons extending all the way had problems with the winglets being very fragile and prone to breaking off.
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Old Feb 03, 2012, 07:28 PM
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Use some 3mm coroplast/correx for the winglets... Nothing fragile about coroplast!!
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Old Feb 04, 2012, 04:00 AM
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Quote:
Originally Posted by jonesymj View Post
Use some 3mm coroplast/correx for the winglets... Nothing fragile about coroplast!!
Unfortunately that wouldn't really help. It was not that the winglet itself that is damaged but rather that they would break off because they were attached to too little surface area. Also the unattached part acts as a lever to tear the winglets off the wing when it snags on something.
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Old Feb 04, 2012, 07:30 AM
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I think I've convinced myself enough to go with the elevons extending all the way to the tips. I just thought that if I needed to add reflex using trim then it would be more effective.

Marked out servo holes. I think I'll cut them all the way through and then cover the bottom with thin 1mm balsa or 2mm depron. The servo covers will be on top of the wing and will be made from 1mm balsa.

Now I have to figure out where to install spars and wing joiners. Also need to figure out how to make hard points to screw the wing together.
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Old Feb 04, 2012, 08:01 AM
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Played around with photoshop a bit to figure out color schemes and this is what I ended up with. Should be simple to mask.
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Old Feb 04, 2012, 10:19 AM
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Cut out servo holes and marked locations for wing joiner and spars. I'm using fiberglass tubes for spars - cheaper than CF and I'm hoping would be more than strong enough once covered with paper and glue.
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Old Feb 05, 2012, 07:57 AM
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Spars, wing joiners and servo hole bottoms installed. Now waiting for the epoxy to cure. Tomorrow and Tuesday are holidays over here so I think she'll be ready for a maiden next weekend.
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Old Feb 05, 2012, 07:02 PM
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Epoxy has cured enough for me to continue working on the wings. Still need 12 hours more for maximum strength.

Cut out and beveled the control surfaces. I almost forgot about servo wiring so I think that will be the last major thing I need to do before covering her with newsprint. One bad news is I ran out of servo connectors. Will have to wait till Wedenesday for shops to reopen then I'll rush down to my favorite robotics/electronics store and get some - they sell cheaper than the LHS.

So here are a few pics of the build progress so far:
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Old Feb 05, 2012, 07:17 PM
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Nice build... it should fly slow and easy with the wingspan.
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Old Feb 05, 2012, 10:29 PM
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Quote:
Originally Posted by KenChin View Post
Nice build... it should fly slow and easy with the wingspan.
Thanks. That's the general idea. I'm not really aiming for slow and easy, rather I'm hoping that it will thermal with the fairly weak thermals we get around KL. I chose the HS522 airfoil because it can be made fairly fast and slippery with a little bit of reflex but slows down very nicely when flaps are added. At least that's what the German sites say.
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Old Feb 05, 2012, 10:42 PM
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BTW, the only thing I've managed to thermal here so far are my vector kites. But a couple of guys with high end 2m composite gliders have managed to stay up for 20 minutes. Which is why I'm building a 2m.
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Old Feb 05, 2012, 10:44 PM
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Hi bro;

I am from Singapore!

Your Epic Win is full of win.

Hopefully it would fly and we can have a look =)
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Old Feb 06, 2012, 03:40 AM
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Servo extension wires soldered up and installed. Just a little sanding and some minor repairs and she's all ready for covering. I'll leave soldering the servo connectors to the RX to later.
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Old Feb 06, 2012, 06:21 AM
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I've been racking my brain trying to figure out how to cover the wings without touching the wet parts. Then I realized that I can simply mount the wings onto fiberglass rods using the joiner tubes. She's all fixed and sanded and now that she's mounted she's ready to be covered.

I'll do the covering tonight. Partly because that's when the kids are finally asleep but partly because I think letting the wings slowly air dry will minimize the chances of it warping due to uneven drying.
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