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Old Dec 20, 2010, 12:00 PM
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FlyingW's Avatar
Long Valley, NJ, USA
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Turbo Bee

Let's start a Turbo Bee thread, since the Lazy Bee and Speedy Bee threads can surely stand on their own.

We proposed to construct a Turbo Bee, starting with drawings and plans kindly produced recently by Gary Anderson also known as gaexcaliber on the Ezone:

http://www.rcgroups.com/forums/showt...rbo+bee&page=6

We've concluded that making one from scratch without the complex laser-cut parts would be challenging. Here is where we stand with a simpler approach to building a Turbo Bee. I had an idea for the fuse tube involving rolled poster paper inside cardboard rings left over from Mud Duck wheels. Dereck suggested cutting circular annuluses from foam.

I began investigating the foam circles approach and found a coffee can in the garbage with metal rims just about the right diameter around which to hot-wire the foam. Then I realized that the can itself is cardboard and two or three them glued together might be perfect! Java city!

The other tool being made is a compass-like knife holder to cut circles in lite-ply. I saw that idea in an old issue of Quiet Flight International in a series of articles by Manfred Malten on designing ducted fans.
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Old Dec 20, 2010, 01:24 PM
Visitor from Reality
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Idly wondering if wrapping the cardboard cans in some kind of release agent, then GF and finishing epoxy might be lighter...

If this gets bad, one of my ancient, should have done it at the time, slimer projects that will now be much better for electricity's invention, could come out the depths of the 'filing system'

D
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Old Dec 20, 2010, 02:19 PM
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FlyingW's Avatar
Long Valley, NJ, USA
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Hmmm. Could try a mold. Would have to wait for warmer weather; no way am I doing that inside.

Unless anyone has tried a water-based resin?

Even with the release agent the tube it may be hard to get off the mold, but it would probably be ok to cut a slit and take it off. Then glue it back later. Don't think you'd lose much strength.

Here's a sample blue foam circle section. Very light and surprisingly stiff, but hard to do. Would have to make eight of them for sufficient length. My compass-razor lasted just long enough to make the two templates.

Maybe I'll try making a block of foam 5" square and 16" long and cut the tube in one shot. The downside of that is that the glue holding the foam block together resists the hot wire...

Nobody said this would be easy.
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Old Dec 20, 2010, 03:04 PM
Visitor from Reality
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Hows about tacking foam squares together with glue that doesn't get in the way of the hot wire? Okay, have to figure out how to keep them together long enough to make the entire cut, but that should be feasible. Yes, I can do hard sums - that's 8 off 2" thick squares.

Then you get to glue the lot together...

Or maybe a tapered foam plug - only tapering 1/4" or thereabouts. Smooth up the exterior, lay up a FG outer on slippery stuff, slide it off when done. Would WBP do the business here, I wonder?

Andy C's issue was finding tooobs in quantity - one or two off would be a lot easier?

D
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Old Dec 20, 2010, 04:08 PM
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I once spent less than an hour to make a lathe for cutting EPP foam rings with a hot wire.

I drilled 4 appropriately sized and spaced holes in a 2x4 to take the end brackets from a prop balancer. The Dubro one would work just fine http://www3.towerhobbies.com/cgi-bin...&I=LXD712&P=ML but I used my old High Point, then I put an aluminum arrowshaft on the rollers.

Next I secured a couple bar clamps near the edge of my bench and used a couple more clamps to provide a rest for my hot wire bow. A couple scraps of pine and some sheetrock screws made quick work of two posts to hold the cutter arms the desired OD radius above the arrow shaft.

The last "building" step was to tape a piece of string to the arrow shaft and put a few wraps around it before tying on an ounce or two of weight. Finally I jammed a piece of foam over the arrow shaft, put it on the balancer wheels, and turned on the hot wire.

It worked a treat with the weighted string providing motivation for it to rotate as the wire cut through the foam. Once I had the outer diameter cut I shortened the support posts by the thickness I wanted for the ring and did it again. The wire made a sloping kerf to the i.d. which I glued up with a little CA once done.

If you can't get foam block big enough, just glue a few together near where the center axle will go. As long as the wire misses any blobs it will cut just fine.

Thayer
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Old Dec 20, 2010, 04:48 PM
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FlyingW's Avatar
Long Valley, NJ, USA
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Eureka! Got a good fuse blank. Thanks for the tips Thayer. Found an old can of 3M77 to tack three 2" thick blocks together. Did the cutting free-hand in an operation I would never publish, however; it came out workable and I have enough blue foam left for only one shot at the wings.

Now to choose an airfoil. Hopefully I have some usable shapes already in the foam stuff box. It's time for glass of wine.

(Dereck - we had a party this weekend so I got my ping pong table back. It's only temporary though as Diane's shirt-painting has a few busy last days before Christmas.)
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Old Dec 20, 2010, 05:21 PM
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Thayer
Sounds like a home-made version of something much more pricey that I have memories of reading about somewhere in the hobby.

A little more 'Red Green' and this could be adapted to make tapered cylinders too.

With a new tailless sports aerobatic design, a repeat three channel low winged cruiser and a desire to finish off my replacement for the dear old 4*40 kicking around my bench, last thing I need is what I can't stop thinking about...

D
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Old Dec 21, 2010, 08:36 AM
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Here is the airfoil proposal (yet another idea borrowed from Dereck's vault of knowledge):
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Old Dec 21, 2010, 10:29 AM
Editor - Flying Models
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Dereck,

Definitely homemade, but it worked perfectly. It can definitely be used to cut tapers. In fact, one of the parts I cut was a circular airfoil. OD was cut with a piece of bent wire heated to approximate the top curve of an airfoil.

FlyingW, that part looks very serviceable. A few strokes with some 220 should clean up that swarf rather nicely. Working with foam is pretty easy once you aren't scared of trying.

Thayer
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Old Dec 21, 2010, 06:13 PM
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FlyingW's Avatar
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Wings next. Thayer, agree that some sanding will get the tube in good order.

Soon I have to decide on a motor. Looks like 100 watts should do it. A prop trimmed to about 4.875 inches in diameter will fit in there.
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Old Dec 21, 2010, 10:02 PM
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maybe I need to get me some of that foam stuff...

For use in my spare time, right now that would be between a new 32" span tailless and a re-make of my dear old rudder/ele/ motor low winger. And maybe a smaller Ford Flivver...

D
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Old Dec 23, 2010, 05:30 PM
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Got the wing cores cut. They are a little rough, but they'll be fine though after a careful sanding. I opted for full-sized cores out of which I will cut the elevons instead of the balsa elevons envisioned earlier. The blue foam seems stiff enough.

My plan to rig her up with two HS-55 servos for the elevons and make a chuck-glider to figure out the CG.

Then I have to figure out a motor. I'm currently looking at a Himax 2025-5300, the same size and weight of a speed 400. The 2mm shaft worries me a bit though. The prop will be something like a 3-7/8 x 4 APCE, cut down from a 6x4.

If I could get a "Rocket 400" I would use that. Had a few of those babies in the past with 3.8:1 gearboxes that aptly hauled a 70" glider to altitude.

Merry Christmas everyone. Be well.

Paul
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Old Dec 23, 2010, 07:11 PM
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A chuck glider sounds good! You could just put this together, ballast it to CG and use it as the test platform off a short bungee.

Smaller diameter prop shaft shouldn't be an issue with the prop inside the tube, or as Sue would say it in her southerly style - 'tooob'.

Regards

Dereck
who has half a wing put together on a new OD...
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Old Dec 26, 2010, 07:12 AM
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Hi Dereck,

Let's see a small preview of that OD.

Hope to design the wing attach today. Glide tests are not likely with a foot of snow and 30mph+ forecasted.

Ordered the Himax 2025-5300.

Here's a cool Christmas present. It flies well too. Of course, I can't leave it alone and will move the CG slightly aft later.
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Old Dec 26, 2010, 12:52 PM
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Alright, you asked for it.

This is off the build plan. I finally stopped diddling around with the drawing and have most of the wing's primary framework together.

Span's 34", power is a spare gold coloured motor on 3S and a prop. UC could be based on the Bee/VSP unless I can find an alloy UC that nearly fits. Control will be elevons, rudder, motor. Covering will be cheap and light, though with a little more colour than Doculam.

The model's style follows my VSP low winger in many respects, though the wing has my usual tailless structure of a symmetrical D box with low AR.

Question from you at the back? You thought that designing model aircraft was difficult?

Sorry...

W - your Crizzie Prezzie - a very small prop, couple of seriously bent paper clips and a suitable office rubber band, a little ingenuity of which you're quite capable of and you wouldn't have to toss it so hard. When's the IMAA legal 400% full size coming out? You already have the documentation

D
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