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Old May 17, 2004, 05:33 PM
Registered User
Tempe, Arizona
Joined May 2004
34 Posts
Scratch built fuselage

I am building my first scratch built electric plane and I have a few questions about the fuselage construction as well as a general question. I have included a few pictures of my partially built wing and some of the ribs that I plan on using for my fuselage.

1) What is the line of thrust and how should it be determined?
2) How should I determine the angle of (incidence? ) of the wing?
3) Should the motor be mounted at an angle to account for the rotational effects of the motor? If yes how much and which direction?
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Old May 17, 2004, 08:50 PM
Registered User
Ithaca, NY USA
Joined Oct 2000
617 Posts
Hi Erik,

Congratulations on designing your own model, and very nice looking construction too.

In general, the thrust line and wing incidence depend on what kind of model you are building, and how you intend to fly it. The airfoil looks pretty thick and symmetrical, so I would guess this is going to be an aerobatic or fun flyer? They often fly with very little angle difference between the wing and horizontal stabilizer. Trainers might have three degrees of incidence.

Are you drawing plans to build from? Typically you would draw a profile and a top view of the fuselage. In the profile view, the motor thrust line would usually be angled down two or three degrees. This helps offset the tendency of a model to climb strongly under power. From the top, the motor is usually pointed two or three degrees to the right. This helps offset the torque effect you asked about.

Will your fuselage be built with sheet sides? You might consider square stringers at the corner of your fuselage formers (ribs) to strenghen the joints between the fuselage panels. And if your formers are cut from sheet, you might add reinforcing sticks to strenghthen them across the grain. And finally, depending on the expected weight and type of flying, you might want to add shear webs between the spars instead of the diagonal braces.

Hope this helps, and again: good for you on designing your own plane.
-Bob
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Last edited by Bob Chiang; May 17, 2004 at 08:54 PM.
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Old May 17, 2004, 09:38 PM
Registered User
Punta Gorda, FL
Joined Apr 2002
4,952 Posts
Flight testing is a time honored way of perfecting a new design. In general, I believe that all prototypes of new designs should make provision for easy adjustment of the CG, the decalage (angle between the wing and tail) and the thrust line angle. Then the results of flight testing should be reflected in the plans if they are to be distributed to others.
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Last edited by Ollie; May 17, 2004 at 09:43 PM.
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Old May 17, 2004, 09:52 PM
Registered User
Tempe, Arizona
Joined May 2004
34 Posts
Thanks

Thanks both for your information. As for the plans for the fuselage I have yet to finalize anything so i am still designing it. I had planned on adding stringers to the corners of the fuselage formers, but I haven't thought about adding reinforcement to the formers. Since they are cut from sheet I will definatelly do that.
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