How to accurately trim plane?

18jeichs
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How to accurately trim plane?

Postby 18jeichs » February 22nd, 2016, 8:08 am

I am apart of a very new team, and we are going to our state competition. We have been semi-successful in wright stuff and have been doing lots of research and testing to get a good plane for state. In our research we have found the term trimming used by several sources. We have a general idea of what it means, but we are not sure how to do it accurately to achieve the best results. We have been a little under a minute in our testing for an invitational meet, and we have created a new plane where we would like to get around at least a minute and a half. If anyone can point us in the right direction or give us an idea on how to accurately trim it would be greatly appreciated!

bjt4888
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Re: How to accurately trim plane?

Postby bjt4888 » February 23rd, 2016, 5:22 pm

18jeichs,

Welcome to the forum and congratulations on your efforts so far. In order to give good specific advice, it will be necessary to have details on your airplane. Is it built from a kit? Is it built from a plan that is available on the internet? Please give all dimensions and specs, including: weight overall with propeller and without rubber motor, wing span & chord, Stab span and chord, wing weight, stab weight, dimensions of wing and stab components (leading edge material, trailing edge material, rib material), motor stick dimensions & weight, tailboom dimensions & weight, propeller weight, fin (if any) weight, Propeller type & pitch & propeller thrust bearing type, wing & stab airfoil, wingpost length, thrustline offset, tailboom &/or rudder offset, stabilizer tilt, wing offset, left wing washin (if any), rubber motor length and thickness and weight (and what types of o-rings, if any), center of gravity location (with motor installed, distance from the wing trailing edge.

Also, describe your rubber motor winding technique, flying specs and procedures and describe your current flights in detail.

The first step in trimming is to know all of the above and have all the built-in settings in a reasonable range.

bjt4888
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Re: How to accurately trim plane?

Postby bjt4888 » February 24th, 2016, 11:26 am

18jeichs,

If gathering all the info I listed below seems a little overwhelming, you could start by including as many of the details as you can. If you want to learn more about the terminology I am using and learn a significant amount more about Wright Stuff, you should read the entire wiki from last year. This may look like a lot of pages of material, but it is not. Many posts are very basic and can be skimmed over till you get to a substantive post from one of the knowledgeable contributors. I spent quite a bit of time on last year's forum (as did a number of others) posting plans, pictures and even videos and detailed descriptions of all aspects of this project.

If you spend even an hour reading last year's material, you will advance from novice to very advanced in knowledge about the project.

This year airplane should fly very comfortably above 2:00 and with a little knowledge, should fly at least in the 2:30 range in a typical gym.

Brian T.

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daydreamer0023
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Re: How to accurately trim plane?

Postby daydreamer0023 » February 24th, 2016, 6:29 pm

Hey, I'm also a rookie this year to Wright Stuff. ;) I would also suggest taking the time to read through last year's wiki - I gleaned a lot of advice from it.

My partner and I got the Freedom Flyer's kit plane and built it to fly for 2+ minutes, but it had a constant problem of flying too high (accompanied by a steep ascent, which would be ideal in a higher gym) and nearly missing the upper beams of the gym (which is about 30 feet high), where it could have easily gotten stuck. We've tried some dewinding on the 3/32 rubber band I'm using (about 40 dewinds from the initial 1200 I wound), and it's helped some. How much dewinding is recommended for this year's plane? If there's no set ideal amount for all planes from the same plane, how do I find the ideal amount if dewinding without risking a crash into the ceiling? Also, would decreasing the angle of attack help any for this?

Also, since we got the stock plane this year and are interested in probably experimenting with creating a design of our own in the future, since Wright Stuff probably won't be around next year in Division C, what would be our next steps with that?
"I am among those who think that science has great beauty. A scientist in his laboratory is not only a technician: he is also a child placed before natural phenomena which impress him like a fairy tale." - Marie Curie

bjt4888
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Re: How to accurately trim plane?

Postby bjt4888 » February 24th, 2016, 8:09 pm

Daydreamer,

Try about 150 backoff turns for an initial flight in a 30 ft ceiling gym. This should give you a launch torque of about 0.30 in oz and a flight to about 20 ft. Reduce the amount of backoff turns about 30 at a time for each subsequent flight till you are as close to the rafters as you want.

A standard technique to reduce climb rate for low ceiling (30 ft. is low) flying is to increase propeller pitch a little. You have probably seen recommendations to do this in other sections of last year's and this year's forums. Also, 3/32" rubber is quite thick. Have you tried the .087" rubber? Ikara propeller pitch range that we have tested is 12" to 15.6" (measured at the 3" radius location).

Rather than trying to create a design of your own, I would suggest that you build from published plans designed by an experienced and successful indoor modeler and learn to select and grade wood. Designing airplanes as a novice that fly better than designs developed by experienced modelers is not likely to be a successful endeavor. Maybe you could start with a successful design and add a little creative variation to make it feel a little like your own.

Brian T.


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