mswify

Guys,

I'm having difficulties with my CG, the plane is really tail heavy and I added around 900gm in the front to balance at 95mm as said in the catalog, I think something is wrong, because I'm using DA100 and I have 2 batteries on the CG and one in the front, please I need your help with this one, cause adding 900gm to the original weight of the plane will make it really heavy.

Lnewqban

A heavier plane is better than a tail heavy one.

For a plane motorized by 100 cc, extra half a pound is not excessive.

Note that the reference for measurement in this case is the wing tip's LE.

You can always verify the proper location for the CG, using the on-line calculator listed in the Aerodynamics forum.

Damo260

Are you using the new DA 100L or old DA100 the new is a bit lighter I was running in mine was the old DA100 with KS 1060 tuned pipes with all my batteries up front and did C/G off the wing tube.
Damo

Zeeb

My Feedback: (41)

Not 'gonna work unless you put all your batteries as far forward as possible e.g. inside the engine dome. If your pull pull rudder servo setup is in back where the manual shows it for a twin install, that'll cause you a problem as well.

What engine are you running?

If you're using a DA-85 or the like, consider yourself lucky to get away with what you've got for ballast.

The problem stems from the fact that the Comp-Arf 2.6 Extra 260 has a totally different fuselage, stab, rudder and gear mounting than the other 2.6 size models. The manual was essentially taken from the 300 Extra and even some of the pictures and parts are for that model not the 260. Since the 260 has a bigger rudder and stab as well as the fact that I think it's actually longer, the standard equipment locations won't work to get the model balanced.

Mine has a DA-120 in it which is even lighter than the DA-100L, it also 1/4" shorter than the 100L so it fits that much further ahead and I moved it out another 1/4" trying to get it to balance. The pull pull rudder servo tray is mounted way forward just behind the landing gear block like the manual shows for the DA-85 install. Two of my batteries for the rx along with the engine ignition are installed inside the engine dome. The ignition battery and throttle/choke servos are on top of the landing gear block and it has a carbon fiber wing tube which is about 1/2lb. lighter than the factory tube.

With all that and 5" wheels, I still had to add 6oz. of lead on the backside of the firewall to make the 95cm measurment for the Maiden flight. It was a bit nose heavy so I changed out the wheels to 4 1/2" wheels which cut 10oz. from there and the balance is now just about perfect for me. If you flip it inverted on a 45 degree upline and let go of the sticks, it'll just keep going.

It still has the 6oz. of lead on the backside of the firewall....

carlosmalone

My Feedback: (25)

All good advice here.
I fly mine on a DA120 with my CG at 4.25” or 108mm and it is really nice so you can save some nose weight there.
Also, I used only one servo per aileron with good results. As stated before, rudder tray must be forward just behind the gear mount and mount the battery forward.
It’s a great plane…your gonna love it!

mswify

Thanks a lot guys for all your help, I extended my motor mount and moved all batteries to the front, but still needed 500gm to balance at 95mm, this will make the total weight 13KG, is it much?

carlosmalone

My Feedback: (25)

The plane should fly fine at 13 kg/ 28.66lbs
Most builds seem to come in around 12.7 kg/ 28lbs
I’d fly it and find where you like the CG. You may find that you can remove some of the nose weight.

After that the easy stuff would include going carbon fiber on the wing tube and changing to a water bottle fuel tank.. It all adds up. Have fun and be sure and report back. :_)

Zeeb

My Feedback: (41)

I think you'll find as mentioned, that you can pull some additional weight out of the nose once you get it flying as the suggested CG for a Maiden flight is forward of what I'd say most will wind up with when flying the model.

Up until the release of the 2.6 Edge 540, the 260 was the heaviest of all the 2.6 size models and if you look at the specs on the website, it'll show a KG heavier than the other models. When I asked my rep about why, he didn't know. What disappointed me was Andreas didn't even know or was unwilling to answer the question.

I found out about the fuselage and stab/rudder changes when I tried to install the SWB tray with a 4 1/4" arm which is what all the other 2.6 size Comp-Arf's use. With the wider rudder, the center to center on the pivot points for the pull pull rudder on the 260 is 4 7/8" so the SWB arm wasn't going to work. I tried all sort of options since I put dual horns on everything and I couldn't find a set for the rudder. The closest I came was a set for the 3.0 meter model which fit the width of the rudder, but the pivot point measurement was only 3 7/8", too short for the SWB arm.... I wound up building two horns for the rudder to get it to fit the rudder width and have the 4 1/4" pivot point measurement. That's when I started chasing the rudder servo tray placement and found the completely different landing gear block install from what you see on say a 300 Extra. The pictures in my manual as well as a couple of parts were for/from the 300 and useless.

Shorter story, the fuselage is the reason the 260 is heavier. I used three 2300mah A123 batteries which weigh 6oz. each, the previously mentioned carbon fiber wing tube which cuts almost 1/2 lb. and mine also has the dual servos per wing on the ailerons with dual horns. The weight as it sits with the smaller 4 1/2" wheels and the six ounces of lead on the backside of the firewall is 28.0 lbs. (sorry, you'll have to do your own metric conversion....) and with that DA-120 on the thing it's just a blast to fly. Not only is there all the power you could ever want, but it fly's quite nicely and you wouldn't suspect it was 28 lbs. from the way it fly's.