acdii

I have this plane that was given to me mostly complete. I made some changes to mistakes made by the previous owner and have it just about ready to fly. Still have to run the tank vent line, fix the combing on the canopy, adjust the rates on the Ailerons, and balance it. I ran up the engine today, its first time running and it fired right off. Have a question about the idle that I will post in the gas forum..

What I need help with is balancing this big bird. With the huge 104" wingspan I dont have a clue how to balance it.

speedracerntrixie

My Feedback: (29)

Usually on a Comp ARF you would start at the front of the wing tube.

acdii

The manual tells me where to balance at, but not how to balance it. It a wee too big for my balance jig. It also looks like they want it balanced at the wing tips.

speedracerntrixie

My Feedback: (29)

Put the wings and stabs on it and with 2 fingers wrapped around the front of the wing tube pick it up. It will either sit level or tail low. If tail low you need to move the CG forward. Most will be slightly tail low.

acdii

I take it thats with the canopy off. This plane doesnt have a wing tube, but a spar box and the spars are attached to the wing and slid into the box, a first gen C-ARF Extra 330L. If I cant slip my fingers around it, I can probably make some hooks from stiff wire to achieve the same results though.

Thanks for the tip.

Zeeb

My Feedback: (41)

Well that was kind of a "rule of thumb" deal and isn't bad until it is....

Suggest that you get a friend to help you and just mark the wing tips and pick it up just like you would a smaller model. If it does not give you the wingtip measurement (which I think Comp-Arf does IIRC) you can just slid the wings onto the spar/tube and use a string to stretch out to the wing tips.

It MIGHT be wise to weigh that puppy as some of those older Comp-Arfs built with that spar were in the 30lb. weight range while they built a "competition" model that only came in the fantasy scheme, had the rould wing tube and was 4lbs. lighter than the other models. When the general public found out about it, Andreas was forced to lighten up all the models and got rid of the spar or "I-beam" for wing tubes.

Since tail heavy can be a real handfull if not fatal to the model on it's Maiden flight, I'd balance the thing the way they say to do it and most will be somewhat tailheavy depending on assembly technique and equipment placement.

Just a thought.....

acdii

so picking it up by the wingtips wont hurt it? That was my fear. It doesnt seem that heavy, but I will give it a weigh in on a scale, if I can find one, the one I have is only good for 9 pounds. Thanks for the tips, I will get to it this weekend.

Zeeb

My Feedback: (41)

Nope, that's the way I did my Comp-Arf Extra 260, my H9 33% Edge, my AeroWorks 1/5 scale Mustang, my, well you get the idea.....

speedracerntrixie

My Feedback: (29)

I'm not a big fan of supporting a composite airframe by the wing tips. I have seen a couple leading edges DE-laminate this way. I have always balanced my Comp ARF airplanes by picking them up by the tube or blade spar. Remember this will most likely not be your final CG position, the goal here is to verify it is at a safe starting point.

Zeeb

My Feedback: (41)

If you cannot pick the thing up by the wingtips, best not to fly it as air loads are not distributed evenly across the wing in flight, particularly in aerobatic flight....

speedracerntrixie

My Feedback: (29)

Picking up a 30 lb model by the tips places more bending loads on the wing then anything you can do to it in flight.

acdii

OK I followed the directions to the letter, it does say to balance 90-100 mm from the leading edge at the wingtips, so thats what I did. I made a rig to support the wiptip at that spot and the bugger balanced exactly at 93 mm. I rigged up a pivot similar to my Great Planes CG rig using CPVC pipe and foam pipe wrap so it could swivel, and it came out balanced in specs. Batteries are charging, Fuel tank vent is done, balancing is done, throws are set, and canopy is glued. Too bad it is calling for rain tomorrow. Aside from the rough idle, I think I will leave the carb setting now until I have a few tanks through it so it breaks in well, then lean it out until the idle is smooth.

speedracerntrixie

My Feedback: (29)

Sounds like you are just about ready to give it a go. Don't be afraid to adjust the idle if it is running a bit fat. I'm not familiar what your experience is with these big airplanes but usually you would be working the throttle a bit while on final approach so a nice responsive throttle is good to have. I'm a bit envious. I have been working on a 3M version of what you have. Just finished painting it but it will be a few months of saving before I can get the electronics. It's been a 5 year project though so I suppose a few more months won't kill me. Enjoy yours, they are sweet flying airplanes.

acdii

Thanks. The throttle seems pretty responsive compared to the DLE20 I have. I will make 100% sure the throttle is OK before I even taxi it. It only has about 8 or so ounces of fuel through it so far. Today would have been a perfect day for it too, but I had other things to do, and looks like tomorrow is rain, so maybe next Sunday, have a swap meet on Saturday to visit to hopefully find a few things to add to my collection for winter.


I cant beleive how fast this summer went an I have yet to burn through a gallon of either Glow or Gas. Last year by now I went through 2 gallons glow and one of gas. Hopefully a slot will open up at the nearby club so i can fly there more often, and not worry about high corn in the way.

speedracerntrixie

My Feedback: (29)

I finished up applying some vinyl on mine so I thought I would share a few pics.

acdii

Looks nice, what size wheels are on yours? The ones that were installed look a bit small. I need to find out what I can clean it with, it has some dirt and marks that I can get out with Windex. I also have to polish the canopy, its dull and scratched up. Did you paint yours gray?

Mine is in the background.

speedracerntrixie

My Feedback: (29)

The canopies for this airplane are no longer available. They make the smaller SC canopies but that would require a new canopy frame too. I borrowed a friends airplane and pulled a mold to make a fiberglass canopy. Because mine is 3M I have 4" wheels. For the 2.6M we were running 3.5" wheels. The wheel pants from Comp ARF are the same for both airplanes so the 2.6 ends up looking like it has clown feet. Lots of guys were going to smaller wheel pants, ends up saving 6 oz or so being that they are smaller and can use 3" wheels.

acdii

That is exactly what mine looks like, it has 4" wheels and they look small with the pants.

Well it's raining like they said it would so, push that bird to the back and go back to finishing the paint job on my CG Chipmunk. Have to do the rest of the red on the fuse and wing, then I can put the gear in. Speaking of molds, I still have to make one of the cowl for the chip. Since I have to get the mold making material for that, might as well make a copy of the canopy since they are no longer available.

flycatch

My Feedback: (26)

Buy yourself a commercial grade balancing stand. Next contact the manufacture and find out here they recommended the starting location should be. This measurement should be at the root rib leading edge going back toward the trailing edge. Normal starting location is 27%.