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Bill Evans Shooter CG

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Old 01-26-2015, 06:48 PM
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CLBetten
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Default Bill Evans Shooter CG

I am just finishing a Bill Evans Shooter. It is one of his tailless designs from the Scimitar series. It's time to balance it. It has a slightly tapered wing. Using the CG as is is on the plan it's only 1 5/8" from the leading edge in a chord of 11 1/2" at the root and with the taper measuring out from the root at 90 degrees puts the CG exactly on the wing tip. Using the formula from April 2012 "Flying Models" written by Greg Moore and using 25% of the Mean Aerodynamic Chord puts the CG at 2 7/8" from the leading at the root. That's a difference of 1 1/4 " in a 11 1/2" chord. The second as according to the formula "looks" better. On the other hand Bill flew/ flies the heck out of his planes. Not sure what to trust? Looking for advice please.
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Old 01-26-2015, 07:34 PM
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All Day Dan
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Always use the one on the plans. That 25% MAC is for a normal airplane. A tail less plane has the CG much further forward. Dan.
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Old 01-26-2015, 10:03 PM
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I've looked at several of his plans online. They all appear to follow his same formula. I've built a lot of airplanes. This is the first without a tail that isn't an obvious delta. All of the articles I've seen that included pictures he had tailless planes in the air. I'll trust his success. Take care, Cliff.
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Old 01-27-2015, 10:24 AM
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I have built and flown three of Evans designs over the years. Follow his instructions for the CG and you will be rewarded with a fun to fly airplane. He knows what his designs are all about.
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Old 01-27-2015, 04:49 PM
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Thanks you guys. For all the research I've done these planes are wonderful flyers and simple to build. I'm surprised they weren't and aren't more popular. Of course the trend where I fly is 3D electric ARFs also.
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Old 01-25-2017, 03:01 PM
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I have built MANY of Bills planes, I flew with Bill in Bishop, CA for many years. Build and balance your plane as per the plans!!! Add 1/8" reflex to the elevons and set the nose gear up about 5/16" above level. These planes can be flown very fast, so don't overdo the aileron throws. Don't be afraid to slow it down on landing, if properly balanced, it will land at just over a fast walk.
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Old 02-01-2017, 03:46 AM
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What IS this CG formula you mentioned
"Using the formula from April 2012 "Flying Models" written by Greg Moore"

Please quote it here so that we can judge whether or not it is valid.
A photo or even drawing of the model would be nice too.

I have my own simple formula, but for flying wings I start with the CG at 15% of MAC

There are some online calculators that look reliable if you search on RCU.
For example, look at the "sticky" above, especially post #'6 by adam one
that leads to this site
http://rcplanes.000webhostapp.com/index5.htm read right to the bottom of the page and click one of the links there to get a useful calculator.
I generally treat a flying wing as a wing without a canard, rather than without a tail. I.e. I set stability to 10% as for a canard, rather than 15% as for a tailed aircraft.

Last edited by alasdair; 02-01-2017 at 04:06 AM.
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