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Easy way to set thrust angles?

Old 11-11-2006, 04:35 PM
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packyj
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Default Easy way to set thrust angles?

Being ill-equipped to measure such a thing, I was wondering if there was some sort of short cut to setting thrust angles when mounting a brushless motor....

Anyone have any tricks up their sleeves?
Old 11-11-2006, 05:42 PM
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cyclops2
 
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Default RE: Easy way to set thrust angles?

Yes.

First remove the prop and toss the plane with all surface at 0 degrees. Rudder,elevator ,ailerons.

Do this in TALL grass. +2 feet is great.

Shim the wing and adjust the battery till it glides perfect at any hand toss speed.

THEN.

Start the engine for a flying speed. ALL surfaces are still at 0 degrees.

Put shims, from cut up old playing cards, as needed to angle the engine to the direction that causes the plane to fly straight and level. Keep increasing the speed till it is straight and level at 0 degrees and full power. Chop the power and it should slow down to a glide with almost no changes to the 0 degree setup.

Yeah, it will take some time on the first plane to get a system of your own shortcuts that work faster and just as well.
Old 11-11-2006, 06:06 PM
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packyj
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Default RE: Easy way to set thrust angles?

lol tossing my balsa 330 without a prop is a little more than scary
Old 11-12-2006, 09:41 PM
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Default RE: Easy way to set thrust angles?

I hand tossed a 82" blue foam A-10 to get the COG & AOA dead on.

Weed rash and scratches beats power testing at my skill level.


EDIT
I forgot you are probably way heavier than my 1#/ sq. ft. I doubt you can toss her fast enough.

Need another 330 owner to fill you in.
Old 11-13-2006, 09:57 PM
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Matt Kirsch
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Default RE: Easy way to set thrust angles?

Is this a kit? A scratch build? Your own design?

Best thing to do with an established design is to start with the default thrust angles. Don't worry, the plane won't be unflyable if the thrust angles are off by a couple of degrees. There's a trim guide on the NSRCA website, http://www.nsrca.org/trimA.htm, which will tell you how to trim your plane out for aerobatic flight, including thrust angles.

If you're working from scratch, you really need a means to measure the angles. It's not difficult if you know a little trigonometry. A flat stick or plywood disc installed in place of the propeller makes a good basis to take measurements. The measurements are a little difficult to describe in words; maybe someone has a link to a diagram? Worst case, start with the motor at 0 degrees. Again, the plane won't be unflyable.
Old 11-14-2006, 09:57 AM
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critterhunter
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Default RE: Easy way to set thrust angles?

Here's how I check it on pushers. Trim at neutral and COG set properly. Fly the plane and get it up high and flat and level in no wind or directly into any slight wind. Keep flying flat and level (trim it out on the TX to get it there) at full throttle and then instantly kill the motor. Does the plane nose slightly up? If so then you have too much downward thrust (the motor is too low in the back by the prop and was forcing the nose down when the motor was on). If the nose goes down when you kill the motor then you have too much upward thrust (the motor is too high in the back and was forcing the nose up with motor on). Now try the reverse. Fly flat and level with the motor off and then instantly go to full throttle. Does the nose go up? If so then the motor is too high in the back and is forcing the nose up when on. Does the nose go down? If so then the motor is too low in the back and is forcing the nose down when the motor is turned on. Left and right thrust is a little more tricky. If at neutral trim the plane tends to pull left or right first check the plane for one side being heavier than the other and use a weight or otherwise to compensate. If that's not the problem then the motor is pointing slightly left or right. Adjust as needed. The goal should always be to get trim at flat and neutral because otherwise you waste speed and power. Use COG and thrust angle to correct. If you still have a problem then resort to trim to get it flying straight.
Old 11-15-2006, 04:17 PM
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packyj
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Default RE: Easy way to set thrust angles?

Thank you for the responses. I haven't been online for a while so I apologize if there has been a delay.

The disc idea is fantastic... beats me spinning the prop around eleventy million billion times trying to get measurments.

Once I get the little guy up in the air (and then again when the air it finds itself "up" in cooperates) I'll use your little guide critterhunter.... I've flown planes with no thrust angle so it shouldn't be disasterous like Matt had mentioned... Now just to get in gear and finish this thing up before the snow starts falling.

Thanks again,
Patrick

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