RV-4 Aileron Trim

I'm at the point in my RV-4 construction process to decide whether or not to install electric aileron trim. Any suggestions?

Nope

You don't need aileron trim. Once you get the control surfaces bent just right you'll never really need to touch it even if you run down a tank too far. The servo is just extra weight and a band aid to not trimming aerodynamcally.

Put it in!

There are not too many perfect airplanes out there, chances are you will wish you had some sort of aileron trim.

Manual trim for all but elevator

i have the manual aileron trim and although not pretty, it is very functional. The manual elevator trim is bulky and has the added weight of the cable. Its the only one I wish I had electric; maybe electric rudder too...

I wish I'd put it in. By the time I got the ailerons set to fly the airplane strait and level, the ailerons didn't line up with the wingtips. I've got the electric elevator trim however, and really like it.

Wes,
I wouldnt waste my time with the trim. If you set your airplane up correctly durring the test phase of your airplane you wont need it. IE Rudder tab if needed and or aileron trailing edge sqeezed to compensate for heavy wing. I have been flying mine for years with no trim. I usually switch tanks every half hour and never have a heavy wing.
Ryan RV4

Aileron trim ? Electric ?

NO WAY !!! Save those stimulus dollars and put them toward a nice wing leveler...

We've talked about this before but... If you can feel a heavy wing, you need to change tanks.

John

Trim is your friend!

Wes,
20 years ago I started my RV-4 project when the RV3 and RV4 were the big boys and the 6 was brand new. Back then the thinking was light, simple and inexpensive. I stuck with that thinking, used only manual flaps and elevator trim and it came in at 925 lbs and it still flies great for it's new owner ("Demo") 1400 hours later. As mentioned above, if you have a heavy wing, switch tanks!
However comma, my Harmon Rocket has three axis electric trim and I have to say I love it. The Rocket however, is a very different machine, much heavier and wider speed range than the RV4 plus Safe-Air-One ER tanks. (both my 4 and HR2)
Would I install it on a 4 I was building now?

Absolutely

Smokey
HR2

My Vote is No

In my opinion, aileron trim would be a good idea for side-by-side seating aircraft where there is typically a lateral imbalance. However, for tandem seating, once you have your plane set up correctly, the only time you need to hold a little side pressure on the stick is when it's getting to be time to switch tanks. To me, that's a great reminder, and a good reason not to install aileron trim....but as you can see from the above posts...opinions vary.

Trim

My airplane is mid range in weight, 975 lbs, and an o-360. It has a change in trim from high to low speed. I might be the only one. I have always been a curious about why my plane is this way.

It also wants different trim from heavy to light. If I am heavy (gas, bags, and passenger), it seems like neutral trim most of the way throught the speed range. If I am light (me and less than half tanks) it is in trim only at cruise speed (165 Knots, 55% power). If I am wide open throttle, level flight, I have a heavy right wing. If I pull the throttle to idle, I have a heavy left wing. Neither is that annoying if you don't fly for a long time at those speeds. However, if you want to make a fast trip, burn lots of gas, at least in my plane, you will want trim. Whether it is electric or manual is personal preference, but I like having the ability to trim. I went without trim for several years, then installed the spring manual trim. it works, but if I had it to do over again I would probably opt for electric trim. If you fly IFR, you definitely need it for final approach where most likely you will be slightly out of trim compared to cruise speed.

I'm interested in what others have to think about the change in trim with speed. Mine is pretty drastic. It goes from full right trim at high speed to full left trim at approach speeds, and I could probably use more trim than is available.

I have the manual trim.

Its cheap and light and I cant see why anyone would leave it out. I cant say I have ever organised the geometry so that its most effective but the need is only slight. All the same I would recommend you go with it, and I do use it.

I have never noticed a need to retrim with speed.

I did it.

Thanks for all of the advice. After much deliberation I went ahead and ordered the electric aileron trim kit. I figured that it would be better to have it and never need it rather than need it and not have it. Thanks again.

131RB said:

Wes,
I wouldnt waste my time with the trim. If you set your airplane up correctly durring the test phase of your airplane you wont need it. IE Rudder tab if needed and or aileron trailing edge sqeezed to compensate for heavy wing. I have been flying mine for years with no trim. I usually switch tanks every half hour and never have a heavy wing.
Ryan RV4

Click to expand...

I believe you are saying to squeeze the trailing edge of the heavy wing to compensate for a heavy wing. Is that correct? Thanks. Fred

Don't bother

Hi

I fitted the manual trim, it was a complete waste of time. Changing tanks will reduce any out of balance due to loss of fuel, but the forces are so light you hardly notice them.


As other pe.ople have said you may need fixed tabs but save the weight and cash!

Fred. No you tighten the light wings aileron trailing edge. Not the heavy wing. It worked for me.

N999BT said:

My airplane is mid range in weight, 975 lbs, and an o-360. It has a change in trim from high to low speed. I might be the only one. I have always been a curious about why my plane is this way.


I'm interested in what others have to think about the change in trim with speed. Mine is pretty drastic. It goes from full right trim at high speed to full left trim at approach speeds, and I could probably use more trim than is available.

Click to expand...

Trim change with changing weight is the same as a trim change with changing speed i.e. it is a function of AOA. The trick is to narrow down the variables. It could also be a directional thing and therefore related to thrust.

For any tests you do you have to keep the ball centeredas that will cause a rolling moment if it isn't. Try flying at the same speed, but at low and high power with the ball centered. Then try different speeds, but at the same power setting so climbing or descending and again, keeping the ball centered with rudder inputs. Eventually you will eliminate all the variables. If it truely is a speed/AOA thing then you need to do a very careful inspection of the wing including the tips, ailerons/flaps including their alignment and gaps, trailing edge shape etc. But first ypu have to eliminate the other possibilities.