Engine thrust angle  
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Engine thrust angle - 3/29/2002 9:25:11 AM   
MiL



Posts: 281
Joined: 1/22/2002
From: Bend, OR, USA
Status: offline 		I'm working on my first design/scratchbuild and am not sure what to do about the engine thrust angle.

The plane is a 35" span fun fly for a .25 FP engine. The wing and stab incidence is 0 deg. to the horizontal.

Do i need to add any right thrust, or down thrust? Due to the nature of the engine mount, it will be difficult to adjust once the plane is built. Right now i'm thinking that the thrust line could run perfectly straight with the plane, but like i said, i dont really have any experience with this so let me know if i'm off base.

Here is a pic if it helps. Thanks in advance for any advice.

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engine thrust offset - 3/29/2002 12:27:34 PM   
majortom-RCU


 

Posts: 1583
Joined: 12/11/2001
From: Merrimack, NH, USA
Status: offline 		With engine and wing on same line, and stab not far above that line, I doubt you will need any downthrust. I'm assuming you will have landing gear hanging down. Vertical thrust offset is more or less a matter of having the thrust line of the engine extend back through the vertical center of drag. With a mid-wing mount and engine on same line as the wing chord, you normally don't need downthrust.

Your drawing looks like a profile. If so, side thrust, should any be needed, is easy to add with a couple washers under the front holes of the mounting lugs. If it's a boxed fuse with firewall, and if I don't trust the kit mfr's recommendations (or if I'm building scratch) I like to use a removable firewall to which the engine is mounted, then mount that to a fixed firewall that is permanently attached to the fuselage. The fixed firewall is almost just a rim big enough to hold the t-nuts. The little added weight is worth it for the convenience. You do have to shorten the nose to accommodate the extra firewall thickness.

(in reply to MiL)
       Post #: 2

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