3M Comp-ARF Extra 260 - C/G

[Jaketab]

Hello,

Getting ready to make my 1st flight with a 3M Comp ARF Extra 260. Plane built with DA-150, MTW 110 cannisters, and 28.5 x 12 Mejelik. The recommended (manual) C/G balance on the plane is 120mm in from the leading edge on the wing tips. I've read other threads that indicate the 120mm point may be tail heavy.

Hope a few others flying this plane will chime in regarding the C/G measurement and the range of balance from nose to tail heavy ????

Thanks - Jaketab

[Hector]

Well I got a DA-150 on Stock muffler and got the CG about 120, probably further back. It flies fine. Trust the Manual. You'll see that after proper trimming you can move the CG further back without any problems.

I don't know the exact measurements in mine, but I remember using the further back CG recommended in the manual, and I found out (While in the trimming process) that I could move it further back, so the plane will perform the way I like it.

Regards,

Hector

[Bunky F. Knuckle]

The manual is right. Try the CG at 120mm. I can pretty much assure you that it will be nose heavy. I have the CG behind the 120mm mark on each MX2 and they are nose heavy. You can go back as far as 1" for freestyle. Anything further back than that 1" and you will be REAL tail heavy...... Try something around the 120-130mm mark.........

******EDIT*****

MX2 #1 has a 3W 170 with mufflers--- 28.5x12S = SPACE SHUTTLE!!!!

MX2 #2 has a shiny engine on it with canister mufflers--- Fuchs 30x11 = Not flown yet. But VERRRRRRY close!!! Will fly within 2 weeks!!!!

[chrisbchips]

My Freestyle 260 is currently setup at 100mm from the leading edge, and my IMAC plane is setup at 95mm from the leading edge. My first 260 was at 120mm, whilst it flew fine, moving it to 95mm completely changed the plane.

[Imac Kiwi]

Chrisby flew my Comp-Arf 3M 260 at the Waharoa Rumble in New Zealand with the c of g set at 95mm from the leading edge at the tip. Frazer Briggs has also flown it and likes the c of g at 95mm. I am no expert and compete at Intermediate level and at 95mm the plane feels great to me.

[TorkRollN]

I can't give you a measurement but I can tell you where things are located in my 260 and how I like it.

My experinece with building the 3.0 meter Comp-Arf 260 is that it would be almost impossible to get it too tailheavy.

Saying that, I like my plane to have a neutral balance. That is, if you roll it inverted, it should maintain level flight without having to "push" down elevator on the control stick.

I have DA-150 stock mufflers with a Mejlik 28.5X12 THREE bladed prop. I have used cannisters before, it just make is more nose-heavy. This is with a carbon spinner. An aluminum would just make it more nose-heavy.

I use all JR 8711's in my 3.0 meter 260. ONE on each elevator half. TWO on each aileron. Three on the rudder, using pull-pull. The batteries, receiver, Smart-Fly EQ-10 are mounted aprox. 6 inches behind the wingtube.

The only wayt to get it too tailheavy, I would think, is to put TWO servos in each elevator or a VERY heavy tailwheel !!!

This is one THE BEST IMAC planes you could wish for !

Barry

[Borries]

3M Comp ARF Extra 260. Plane built with DA-150, Geeve Tune pipes, and 28.5 x 12 Mesjelik. The C/G balance on the plane is 100mm in from the leading edge on the wing tips.

BB

[Jaketab]

Thank you all for responding.
The previous owner of this plane flew IMAC, and thus forward C/G. With the canisters in place, it will be difficult to bring the C/G back to 120mm. Based on your responses, I believe a C/G of around 100mm will be OK.
My preference on the C/G would be similar to TorkRollN. Would like to have plane neutral at any attitude and one that would make nice flared landings.
Anyone else please jump in and report on your C/G preference for the 3m C-ARF Extra 260.

Thanks - Jaketab

[Dan767]

Mine is set at 100mm. IMAC plane. Flies close to neutral.

[lazyboyflyer]

I fly IMAC with mine set at 95mm.

[Jaketab]

It was great!!! Flew the 3m 260 for the first time this weekend. After flying this, it will be hard to go back to a lessor plane.

The C/G was between 105 and 110mm. The elevators were set at neutral before the 1st flight. It jumped off the ground quicker than I expected and required about 8-10 clicks of down elevator trim to fly level. As a result, knife edge requires up elevator to prevent pitching to the belly.
It also took a longer landing then I expected even with the idle RPM at 12-1400. The plane has to slow substancially before it will quit flying.

My question is now one of needing downthrust in the motor???
However, the manual calls for 0 to .05 degrees of upthrust.

Has anyone adjusted the up or downthurst to correct habits of the plane?????

Thanks - Jaketab

[cesar781]

That is funny !!! becouse my krill did the same thing . It was 6 click down elevator and in knife edge pull up elevator
yes I did but just a wash in the lower stand offs but I culdn't fly yet to see what happend
will be looking for the others opinion about it !!!!!!
Cesar

[Hector]

	Quote: Originally Posted by Jaketab
	It was great!!! Flew the 3m 260 for the first time this weekend. After flying this, it will be hard to go back to a lessor plane. The C/G was between 105 and 110mm. The elevators were set at neutral before the 1st flight. It jumped off the ground quicker than I expected and required about 8-10 clicks of down elevator trim to fly level. As a result, knife edge requires up elevator to prevent pitching to the belly. It also took a longer landing then I expected even with the idle RPM at 12-1400. The plane has to slow substancially before it will quit flying. My question is now one of needing downthrust in the motor??? However, the manual calls for 0 to .05 degrees of upthrust. Has anyone adjusted the up or downthurst to correct habits of the plane????? Thanks - Jaketab

Well Jaketab, I don't have the C/G Measurement for mine, but if I remember correctly I left it close to 115mm-120mm, It only took 2 clicks (at the minimum for trims which in a Futaba 12Z is 1, default is 4) of down trim thats almost nothing. And it took no down or up thrust but it need right thrust for the Mejlik 32-10 on a DA-150 on stock mufflers. About 3.5 degrees.

I got my RPM set @ 1,000- 1,050, and without wind my bird is fast (400' roll out) but I guess thats the problem of a clean airframe. With head wind 5-12 mph it stop in about 300', if I bring it close to stalling in about 175' not bad. In a cross wind is tricky since my runway is only 22' wide with holes to one side of the runway, so we need to fight it, but you get the used to it and you learn to anticipate your plane.

My advice is to lower your RPM to 1,000 to 1,100 max, then practice the slow flight up high so you know what the airplane might do if its stall.

Don't be afraid to bring it low and slow, but be ready to bump the power if you notice the control of the airplane sluggish.

Good Luck,

Hector

P.S.

I have attached the Trim Table that it would help you answer all your questions about C/G, Thrust angles, Mixing, during your trimming process of your aircraft. Be sure to follow the order so you can make the best of it.

[Jaketab]

Thanks for the trim chart Hector.
Anybody else on adjusting up or down thrust on the 3M 260 C-ARF.

Jaketab