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Old Jul 12, 2013, 11:14 AM
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Considering an EDF for Kestrel

I am hoping I can get some recommendations for this plane I designed and built. I call this the Kestrel. It has a 5 degree swept-back wing which is reinforced very strong. Both the leading edge and the main spar are carbon-fiber. I designed it to be a rocket-powered glider, and is sized for D or E motors. However, I also provided a method to launch it with a high-start, for just gliding around without a rocket motor.

The more I think about it, the more I think it would be a good idea if I designed an EDF pod to replace the rocket motor pod, underneath the wing. This wouldn't require a huge EDF. A small one would probably suffice. It just seems to be a natural for an EDF conversion. And the nice thing about it is, the rocket pod was designed to be modular. It can be removed. It would be nice to have the option for jet power too.
It's also because rocket motors without a parachute charge are hard to find, and I was told by a hobby shop that Estes doesn't carry the plugged line any more. If I have to buy rocket motors from abroad, then flying this airplane on rocket power could become expensive.

Some details on this airplane. It has a 48 inch wingspan and a 5 1/4" constant chord, giving it a wing area of 252 square inches. It has a Clark-Y airfoil, for good lift qualities. The airplane, as you see it, weighs 18 oz, which is not bad, considering how tough it was built (to withstand a rocket's thrust). The rubber bands holding the wing down are strictly for conventional gliding. Under rocket power, the wings get bolted down. (In fact I'm thinking of cutting off the pegs and leaving it strictly bolt-on).
As it is now, it has a wing loading of 10.3 oz/sf and a stall speed of 15.9 mph.

The EDF I'm interested in would preferably run on 3 cells, and I know flight times would be short, but they're not exactly long flight times under rocket power anyway.
What would be some good compact EDF options that would put out, say, at least 12 oz of thrust? Anything? Or am I better off leaving it rocket powered?

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Old Jul 12, 2013, 01:41 PM
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I've looked at a few EDF combos out there and I think I found one that might work. First I looked at the 40 mm GWS EDF, but it only put out about 8 1/2 oz of thrust, and might be underpowered in this airplane. I don't think I need a 1:1 thrust ratio, but if the plane weighs 18 oz, it should at least get a little closer to that for legitimate flight I think.
Also, the fuselage is only about 40mm in width. And there is limited room for air scoops.

I think the 50 mm GWS EDF would work a little better maybe. It's still compact, and would stick out beyond the sides of the fuselage slightly. I'd just have to complete an aerodynamic scoop for it. It puts out 400 grams of thrust, which is what, about 14 ounces? Uses an 11.2 V Lipo, 233 W, so that should work. Here's the link.

http://www.extremerc.com.au/estore/i...roducts_id=818

Or, considering I might increase in weight a few ounces if I convert this to EDF, I could use the 55 mm GWS. That's about 20 oz of thrust and 284 W.

http://www.extremerc.com.au/estore/i...oducts_id=1172

Thoughts?
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Old Jul 12, 2013, 01:57 PM
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To get a little more info on the smaller systems, you should check-out here:

Micro EDF Jets and Power Systems

http://www.rcgroups.com/micro-edf-je...r-systems-650/

That's all they run are these sizes fans, .
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Old Jul 12, 2013, 05:31 PM
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Thanks Cooler.
I've browsed through many of those threads on that link, and they all seem to be smaller jets than this one. Those are Micro-EDFs. 30mm and smaller for most of them. What I'm talking about is a 50 to 55 mm EDF. None of them are really very similar to what I've got.

Well, the 50 mm would fit better in my plane. But at 14 ounces of thrust, I wouldn't want to go any weaker than that. I think an 18 to 20 ounce plane would fly on 14 ounces of thrust, but I'm worried about it being underpowered.
The 55 mm would definitely make ample thrust for this plane, but I only have a 60 mm space for it, so it'll be a very tight fit if I use that. Hmmm...

I'm leaning towards the 50 mm and see how it flies. If I'm not happy with it, I can retrofit a larger one, or maybe just use a 4 cell lipo in the 50mm and it should be fine. (Provided I choose a motor that can handle that).
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Old Jul 12, 2013, 06:04 PM
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Sorry, not to knowledgable on the smaller fans, hard to keep up on the 90mm ones. Check out some of D_Fast's threads, or even sloperjoes. Someone will chime in soon.
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Old Jul 12, 2013, 10:22 PM
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Thanks. Yeah there's time.
This is way cooler with a rocket motor, but there will come a time when I know I'm going to wish I had an EDF on it. It will probably be a little bit of trial and error, actually.
I'm thinking the 50 mm fan is what I need, preferably with a motor that is compatible with either 3 or 4 cell lipos, so that if 3 cells won't quite do it, I just get a bigger battery.
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Old Jul 13, 2013, 06:21 AM
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55mm fan your best bet 16 oz plane will fly nice on 8 oz thrust try GREAT PLANES HYPER FLOW 55MM FAN
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Old Jul 14, 2013, 09:28 AM
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Thank you very much. I will look into that.
I still do want to fly it with the intended rocket pod, but I am having a lot of trouble finding any plugged D-sized rocket motors. And the cost of each flight would get a little expensive. So I am going to go ahead and design an EDF pod to go underneath.

My fuselage is about 40 mm in width and 60 mm tall right where the power pod is underneath the wing. It is limited by a carbon fiber rod that doubles as both a skid and a guide for a rocket launcher. So a 55 mm EDF might fit underneath, depending on what the exterior dimension is, but it'll be tight. It would definitely stick out on the sides by maybe 10 mm on each side, considering the exterior dimensions of the fan case. But that's okay. That can be incorporated into the scoops. And I'll have to create a thrust tube for it.

They're not very expensive, so I'll order the EDF and then evaluate how it'll fit. If it doesn't fit, I can always build another plane to stick it in, and then go for the smaller 50 mm EDF.
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Old Jul 16, 2013, 06:21 PM
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I found a source for D-sized plugged rocket motors. I think I might buy a 3-pack and see how the glider flies. It's quite a punch of power though. An Estes D11-P puts out 5.64 pounds of thrust for an initial spike lasting less than half a second, levelling out to a steady 2 pounds of thrust for just shy of 2 seconds.

In an aircraft weighing 18 ounces, that's a LOT of power. About a 5:1 thrust to weight ratio to launch, and then a 2:1 thrust to weight ratio for up to 2 seconds. Someone who is good at physics could probably predict the altitude, but I'll bet it would be 200 to 500 ft.

I am still looking at EDF options too, for a much more "gentle" flight envelope. 50 mm fits better, but they only seem to get a max of about 15 oz of thrust. That would still fly something weighing what this plane weighs, which would be more like 20+ ounces with larger battery and motor.
The 55 mm EDFs really are just barely too large.
I found a 7 bladed 51 mm EDF, sans motor, for around $15 bucks. I may play around with getting a pod built around that, and then find a good inrunner motor for it.
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Old Jul 17, 2013, 08:32 AM
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Have u looked into a performance 50mm edf? Wemo and a don.s wicked puts my 19oz f16 vertical and out of sight. i havnt done any thrust tests. But she will spin on the ceiling a t2/3throttle.
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Old Jul 17, 2013, 10:49 AM
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To tell you the truth, I am having a VERY hard time researching and finding EDF systems. What I really need to do is find a good book on the subject and study it. Then I need to gather my sources, which is what I'm doing here.

Thanks. I'll look into Wemotech. However, Don.S I don't know about. Do you have any links?
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Old Jul 17, 2013, 02:34 PM
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I think if you ck AMA out lawed rocket power RC air planes
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Old Jul 17, 2013, 04:02 PM
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Quote:
Originally Posted by space 1 View Post
I think if you ck AMA out lawed rocket power RC air planes
That's funny. Because just a month or two ago, I picked up an RC magazine (forget which one) that showed a rocket-powered glider going ballistic, straight up, and that was at an RC meet.

Well, if it's AMA-outlawed, then I'll have to have some decals made for this Kestrel calling it the Outlaw as nose art, and then fly it away from an AMA-sanctioned field.
What they don't know won't hurt them.
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Old Jul 17, 2013, 04:03 PM
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I will, however, proceed with the EDF idea, as I think that is a much more practical use for this great little plane...
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Old Jul 18, 2013, 11:11 AM
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??

Quote:
Originally Posted by space 1 View Post
I think if you ck AMA out lawed rocket power RC air planes
I dont think there is a problem with rocket powered.Just no rockets launched from rc planes.
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