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Old Feb 23, 2016, 05:28 AM
nicolelc is offline
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Help!
Need help with dual EDF placement on glider and control surfaces.

I am adding dual 28mm EDF's to a Hitec Hawk Eye glider/MPX Fox and I need a little help because I may be over thinking this.

My worries are because I am not going to be using a rudder, I do not want to build the plane so it will have adverse yaw in turns because of how the wing is shaped.

I want to mount the EDF's under the main wing if that would be a good place for them in your guys opinion. The problem is that if I add ailerons to the inner flat part of the wing, it is going to partially block/deflect the thrust from the EDF as the aileron comes down. I am stuck on this worry of if I put the ailerons on the polyhedral portion of the wing that they will 1. cause adverse yaw. 2. I am not sure how well they will work, or if they will try to put the plane in an awkward attitude when rolling/turning that I will not be able to correct because of the lack of rudder.

I have attached pictures of the plane, wing, and the different places I've considered mounting the EDF's.

I plan on just using an elevator and ailerons, but since the tail is a bit flimsy already, and I will be adding a servo to it, I am not sure about the far rear mounting of the EDF's.

Any input would be greatly appreciated. I have never used EDF's before, so I am not sure exactly what could affect them, or even the best placement for them.

AUW should be around 140g
Wingspan: 24"
Fuselage: 19"
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Last edited by nicolelc; Feb 23, 2016 at 06:22 AM.
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Old Feb 23, 2016, 05:34 AM
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I guess to simplify the mess in my head, the questions are.

1. Where would you cut the ailerons in the wing?
2. Where would be optimal placement for the two EDF's?
3. Is there any other changes or recommendations you would like to offer?
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Old Feb 23, 2016, 06:43 AM
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An itch?. Scratch build.
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Quote:
Originally Posted by nicolelc View Post
I guess to simplify the mess in my head, the questions are.

1. Where would you cut the ailerons in the wing?
2. Where would be optimal placement for the two EDF's?
3. Is there any other changes or recommendations you would like to offer?
1. Where they do most of their work, in the outer part of the wing.

2. In the For Sale/ Wanted forum, (or maybe in a proper looking jet model at a pinch, I don't do EDF, or want to ).

3. Have a total rethink.

3a. Your 2 EDFs will use up amps at a high rate, so short flight time.
3b. They will weigh more than a single prop version, and increase the stall speed, so handling could deteriorate.
3c. If you go to a larger capacity battery, as above, you're just adding weight, a bad thing.
3d. If the tail is already 'flimsy', it will probably tear off in any higher than usual 'G' maneuver, that weight again.

But other than that , you can always do whatever you want, and there is sure there will be others who will say, "cool, go for it".

You did ask

Ray.
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Old Feb 23, 2016, 07:13 AM
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I have the newer version of the plane(with very close to the same size tail) that is conventional 10g motor/5x3 prop(114 AUW) with 1 servo in the tail and it handles everything I can give to it. It is EPO, but hanging an extra 25g with 2 EDF's I think that is going to be pushing it at the smallest portion of the tail. If it turns out that is the best place to mount the EDF's, Ill put some carbon in the tail of the new plane; But I am trying to figure out from someone with some experience with EDF's the best place to mount EDF's on a tailed plane. I know they are in the very back with a jet, but I have also seen other planes when I searched with them mounted everywhere from molded on top of the wing, all the way back to an A-10 Warthog twin style. I am not even sure the back of the plane is the best place for them, that is part of my question. I have trial fit them all over the fuse/wing and attached the pics to the first post.

I have attached a pic of the other Hawk Eye fuselage tail section that is complete. I will be making the new tail almost identical.

Red is the completed plane.
White is the new fuselage getting the twin EDF's.
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Old Feb 23, 2016, 03:15 PM
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Have a look,or ask in the -Jets EDF forums ---

http://www.rcgroups.com/aircraft-electric-jets-375/


Ray.
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Old Feb 23, 2016, 03:22 PM
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I tried a quick search in there, same plane ? ---

http://www.rcgroups.com/forums/showt...e#post28896254


Ray.
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Old Feb 23, 2016, 03:26 PM
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Build straight - Fly twisty
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Eflightray speaks words of wisdom and I agree with his recommendations.
However if you really wish to go ahead with this, some things seem obvious.
Firstly the ailerons should be on the outer panels. Rig then with differential to counter the adverse yaw problem.
Secondly, mounting 2 EDF units aft of the CG will require a lot of weight in the nose to counter balance them. Therefore the choice is above or below the wing root adjacent to the CG position. Below the wing would look neater but the EDFs would ingest grass and rubbish during powered landings.
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Old Feb 23, 2016, 03:30 PM
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I think I am going to give up on it and put a motor and prop on it.
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Last edited by nicolelc; Feb 25, 2016 at 02:45 AM.
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Old Feb 23, 2016, 11:05 PM
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"Delta V-180 or similar thrust?" In micro edfs....
You could do your control surfaces, rx, batt(light one) get that balanced nice for flight. Then experiment with the fan positions. Balance accordingly around cg. It might be fun.
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Old Feb 23, 2016, 11:11 PM
nicolelc is offline
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The brand new EDF's are listed in classifieds, I took another route with the project.
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