GP Fling E-Powered build - RC Groups
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Oct 12, 2005, 01:52 AM
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GP Fling E-Powered build

When I saw the new Fling from Great Planes one of my first thoughts was "Small electric powered park sized sailplane", so here goes: Step one, gather the various bits and pieces.

Motor: Medusa Research 4000rpm/V 12mm
Gearbox: 5:1 planetary from Aeromicro
Esc: CC10
Receiver: Berg 4dsp
Battery: Polyquest 10C 600MAH 3S pack
Prop: Small carbon folder from MTM International
Servos: Cirrus 101 STD 4gm. (2)

Total weight of all the above components: 3.5oz.

The above components should provide approximately 11oz. of thrust at 3.6A. well within the abilities of the Polyquest pack.

Model capabilities: Hotliner, Not, but should give a reasonable snappy climb.
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Oct 12, 2005, 01:56 AM
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Step Two: Will it fit??

YES with room to spare.

Next step, The Fling itself.
Oct 12, 2005, 02:56 AM
Master of Fun
Jeff85's Avatar


Please give us MORE! Looks like a fun project.
Oct 12, 2005, 05:36 PM
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thermal's Avatar
Great idea, will be interesting to see how it flies and thermals.

Oct 13, 2005, 10:56 AM
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FWFlyer's Avatar
Let us know what you have to do to get the proper CG.
Oct 14, 2005, 03:32 PM
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e_gadgetgeek's Avatar
Can't wait to see the results. I've been flying my Fling for about 4 weeks now and was wondering how to approach putting power to it. Getting tired of all the exercise walking out to pick up the mini hi-start ring.
Oct 15, 2005, 01:55 AM
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Here are some more photos. (As you can see from photo 2, I really need to figure out the focusing of the camera). I'm from the "old" SLR days when you actually had the option of manual focus. I just discovered that the photo descriptions didn't make it to the post, so here are some brief descriptions:

1. Balsa temporary mount to determing actual shape of 3/32 ply mount.
2. Plywood mount epoxied in fuselage, 1/64 ply spinner ring and gobs of lightweight spackle.
3. Another view of the spackle buildup.
4. Sanded front end with prop and spinner in place.
5. Tail feathers stripped and re-covered with SoLite, the thin black lines are vertical pieces of .007 carbon fiver to add stiffness to the stab. note added rudder area.

I'm planning to add a couple of air inlets just behind the motor mount former. Hopefully it can be done and still have them not looking too obtrusive. I also plan to mount the wing with a dowel in front and nylon bolt at the back. It will look a lot better then rubber bands.

I still haven't decided where to put the cooling air outlet. I'm thinking of coming out of the non structural area in the wing center behind the spar and on either side of the center rib. It's kind of an odd place but the fuselage would be weakened by cutting any functionally sized holes in it. Any suggestions??

I also strengthened the rear of the fuselage boom where the cable outlets are with a wrap of .007 carbon lenghtwise and sanded smooth. I've also added additional rudder area as it seems from other threads that this model needs more turning authority. This is probably due to the short tail moment and the considerable side area of the fuselage in front of the wing.

To Answer the balance question: I don't think there will be too much of a problem as the battery will fit in the fuselage even as far back as the CG point.

I was planning on using the Cirrus 101 4gm servos, but when I saw how small they are I started having second thoughts. Has anyone out there had any experience with these servos? Again I'm open for suggestions.

More later
Last edited by Oian; Oct 15, 2005 at 02:04 AM.
Oct 19, 2005, 01:38 AM
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A couple more pictures and some comments concerning the wing:

Picture 1. Inlet vent on the underside of the nose.

Picture 2. The air exit vent in the top of the wing, and the nylon machine screw atachment for the wing.

When I looked over the wing after the original covering was removed I discovered about 1/8" of wash-in in the left tip panel . Possibly OK for a free flight but NOT for an R/C model. This was too much to remove with heat only. Had to slit the upper and lower D-box sheeting, hold in opposite twist and CA the slit shut to provide a little Wash-out. I would advise anyone who builds one of these planes whether it be as a glider or electric to carefully check the wing warps. That much wash-in would make the model difficult to trim and probably lead to tip stalling problems! The only warps I want to see in a model like this is a little equal wash-out in each tip panel.
Oct 19, 2005, 10:04 AM
JimNM's Avatar
I really like the scoop - how did you do that? and.... it is on the bottom? I've had no luck with scoops placed there - too much dirt inside. I guess I could fly where there is grass.... if Icould find some

Oct 19, 2005, 10:13 PM
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Here is how I made the one in the photo. Yes it's in the bottom of the fuselage, I would have preferred it elswhere for the same reasons you state, I live in an area that is known for dirt and dust but it's the only place where I could justify it structurally. I guess I'll just have to learn how to fly well enough that I can catch the plane.

A "real" NACA inlet has very precise dimentions. for all the details check the following: (if you don't use a capital "R" in resources you won't get there). When the site opens click on NACA inlet article from Sport Aviation 12/2001.

It seems from what I've seen in other sources that the inlet can be shortened and the angle increased from the optimal 7 degrees with some loss of effeciency. It also seems that the airfoil shape at the rear of the inlet is VERY important. But I think that at the sizes we use it may not be all that important and it still makes a really good looking inlet.

Here's how I did it:

1. Cut a piece of 1/32 ply to the shape of the bottom of the inlet.
2. Glue 1/64 ply sides to the base to make a "U" shaped piece. The width of these pieces should be higher than the depth of the proposed inlet. cut with the outside grain of the plywood vertical for easier bending.
3. Cut a hole in the fuselage where the inlet will go using the base of the above piece as a template.
4. Epoxy the inlet into the opening with the foreward top end of the 1/32 ply base flush with the outside of the fuselage and the back end at the depth you choose for the opening that you want.
5. Sand flush with the outside of the fuselage.
Last edited by Oian; Oct 19, 2005 at 11:00 PM.
Oct 19, 2005, 10:55 PM
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Here's a photo of the completed airframe with the electric modifications and new covering. Now comes my favorite part (yeah right!) installing the radio etc. The bare airframe without prop and canopy weighs 5oz. Covering is SoLite, AKA Nelson Light Film, It looks like I might need some red paint for the fuselage.

As for getting the right CG, as it stands with the motor and battery in the nose the balance point is about right so I don't think there will be a problem with a nose heavy model.

I think that the estimate on the box of a ready to fly glider being just under 7oz. may be a little optimistic. It seems that the total weight of this electric version will come out around 8.5oz,that's still a pretty respectable wing loading of about 5oz/sq.ft. .
Last edited by Oian; Oct 20, 2005 at 09:47 AM.
Oct 20, 2005, 08:28 AM
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e_gadgetgeek's Avatar
8.5oz should be fine. When I first flew my Fling, I used a 600mah AAA 4 cell battery pack and my AUW was 8oz. It flew great. I had the battery under the wing and balanced at 2.75" from LE on the wing. So, it can handle the extra weight.
Oct 20, 2005, 09:46 AM
JimNM's Avatar
Veeerrrryy Nice. Thanks for the tip on the NACA scoop. I've been toying with casting some in resin - but haven't yet overcome my own inertia to git'r'done - as the kids say.

I painted my canopy gloss black on the fling - and I reccomend it highly

Go fly it!
Oct 21, 2005, 12:47 AM
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Jim NM:

Thanks for the suggestion on the black canopy, The white fuselage and grey canopy just looked out of place with the red and yellow covering. I found a can of red Krylon paint that was a pretty good match to the red SoLite (*when it's put over yellow SoLite). and an old can of gloss black and this is how it came out

* I sure wish the manufacturers of SoLite would come out with a better formulation for their translucent red covering. As it comes it's a very strange pinkish color that does not go well at all with the yellow (or any other color for that matter). If however it is put over the yellow the result is a very nice bright red as seen on this model. I suppose that if they mixed the red pigment they use now with an equal amount of the current yellow pigment they would have the nice red that you get by putting one over the other without all the problems of the minute annoying bubbles one gets when one tries to put a translucent color over another translucent covering. Anyone from SoLite listening???

Before I get too far into mounting the radio equipment I have a servo question: I was planning on using the Cirrus 101 4gm servos. They seem a little small, has anyone had any experience with them? It would only add a few grams to go up to one of the 6 or 9gram servos. Any thoughts or suggestions or specific recommendations?
Oct 21, 2005, 06:39 AM
JimNM's Avatar
That is one HOT looking little plane


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