Trimming planes - RC Groups
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Aug 26, 2013, 12:26 PM
"Get off the runway!"
Da Big_G's Avatar

Trimming planes

Trimming my Airoso. Looking for backup on my procedure....making sure I have the order right. The problem is my power off down lines the plane pulls slightly to the canopy. Also climbs a bit on full throttle and dives slightly inverted. I will start adding weight to the tail until inverted flight is almost hands off. Then if it still pulls a little to the canopy add a little up-thrust to the motor. Do I have this right?
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Aug 26, 2013, 01:50 PM
Registered User
Take a look at your elevator position after you've trimmed the plane for hands-off level flight. If it's too nose heavy, it'll likely be carrying some up trim.
Adding up thrust may help, as you'll have to feed a little down trim to keep level flight. The down trim will help the power-off down lines.
I would add a bit of weight to the tail first. You could also reduce the wing incidence, but you definitely want to get the C.G. where you want it first.
The trouble with trimming is that each little change will affect many other things, it's easy to start chasing your tail (or the planes)
Aug 26, 2013, 07:38 PM
KE your cub.
Curare's Avatar
I don't necessarily agree with that, but then again trimming is an interesting thing, some say one thing, others say another.

First things first, I don't trim for straight and level flight, for the simple reason that I'm rarely in that position for long, and trimming for that means that every other position is affected by that trim setting.

I set mine for 'zero G' flight. That is: straight down. I trim the plane until it flies exactly vertical, no push, no pull. I then turn around and fly straight up, if the plane pulls to the canopy, add upthrust, and if it pushes to the belly, add downthrust.

After that you'll find that you need to fly holding the nose up, either upright, inverted, or knife edge or a combination of two. How much you have to pull is determined by your cg, the more forward it is, the more you'll be hanging on the up stick. As for determining the correct cg, that's a matter of taste and to a certain extent spin entry, and knife edge flight.

For a slightyl different approach, try using the trimming chart from Peter Goldsmith, it's the bible for most guys wanting to start trimming their planes out.

Here's the link to it.
Aug 26, 2013, 08:26 PM
"Get off the runway!"
Da Big_G's Avatar
Thanks guys...I've seen those charts. Looks like I'm on the right track. Can't wait until Saturday comes to do the final trimming.
Aug 27, 2013, 12:07 AM
KE your cub.
Curare's Avatar
Hehe, in pattern it seems you stop trimming the aicraft when you total it.

Even after hundreds of flights, I still end up tweaking my planes, a little at a time, then go too far, mess it all up, and start right back where I began knowing that wasn't the way to do it LOL!
Apr 12, 2015, 04:29 PM
Registered User
ABC_Aero's Avatar
Is it even possible to trim for a "straight and level" flight
and have a fine same trim for "straight down" (with motor at idle)
with CG around around 25-35%?
Apr 12, 2015, 08:51 PM
AMA 97737
ltc's Avatar
I have a folder in my shop file cabinet dedicated to as many online trimming/setup guides for pattern as I've been able to find... I like to read them instead of normal things like magazines or books.

I recently purchased Bryan Hebert's Triangulation Trimming Guide and I think it's the most direct, easy to read (4 pages total) guide I've come across.

With the snow finally almost melted, I am hoping to apply it this year at the field and see how a plane should fly.
Apr 14, 2015, 02:31 AM
Registered User
Basic trim chart here:-

I'm sure I found the Herbert trimming guide online somewhere which I printed of free gratis, but damned if I can find it now.
Apr 14, 2015, 10:16 AM
Registered User
Sounds as though you have a little down thrust in the motor.

Rick H.
Apr 15, 2015, 02:08 PM
Registered User
Trimming is a very personal thing. Try several methods and see what works for you. I follow Hebert's method mostly and fine tune for my taste and airplane. I consider a plane that doesn't need down elevator when inverted very tail heavy. A few more degrees of down elevator throw and expo will give a similar feel to the elevator in either direction. Most will use a slight down elevator to low throttle mix for down lines and a little more down thrust to prevent the ballooning with full throttle.

I agree with Curare but am slightly more optimistic. The day you stop trimming is the day you sell it!
Apr 15, 2015, 10:58 PM
KE your cub.
Curare's Avatar
Perhaps I should rephrase my statment to 'a pattern aircraft stops being trimmed when it's totalled'

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