I have a OPM 540 FF and I think the plane is tail heavy. It is very sensitive to elevator inputs. It will go up or down a little on its own. I just picked the plane up between my thumb and index finger along the top edge of the fuse to find the CG. I used Billy Hell's 5.5" from the leading edge as stated in his review. I did just notice that the manuel says 2" - 1.75" from the main spar. There is about a 1/2" difference toward the tail heavy side between the two CGs. Do you guys have any good methods for getting the CG of a profile? And do any of you have advice about a good starting CG measurement for the OMP 540 Edge?

So far the Bros have been stellar with helping get this first build bird in the air. THanks for everything.

Dick Pro Bro 757

I'm 757 and fly like a 757. Give me a little though.

I'll go down tonight and verify that cg. I'm pretty sure it's right but I'll make sure.

A quick and dirty way to find a happy CG is to trim your plane for level flight, hands off. Then roll your plane inverted and all you should need is a little hint of down or no down at all for level flight. If your plane starts to climb then your CG is too far aft.

Like I said that is a quick and dirty way of finding a starting point. Other things to check to see if your wings are warped, ailerons reflexed, stiffness of your control linkage. stiffness of one elevator to another etc.

5 and a half it is. I personally think it could go back a little more. Start at 4.5 and see what you think.

Thanks for the replies, and thanks for double checking the measurement Billy. I double checked also. When I measure from the leading edge of the wing 5.5" is equal to 2.5" from the main spar. The manual says 1.75" - 2" from the main spar. When I fly inverted the plane climbs with gusto. I'll try the 4.5" you suggested. I am also assuming the main spar is the spar that the trailing edge of the wing sheeting is glued to. If someone is wrong here I'm sure its me.

This plane is so responsive. I have it on low rates and it chases its own tail. By the time I fly off a few ounces of fuel the thing is a total squirrel. I just want to dial it in before I plant it in the ground. I haven't had such a good time with a plane before yet been so frustrated. I dared to try high rates and did my best blender ever on the first attemp. The guys at the field all wanted to know how I did that. Anyway thanks for the help. I'll keep at it.

Dick Pro Bro 757

Well keep in mind this airplane is meant to fly slow. With a little speed the resonse time go up HIGHLY. I flew airplanes for about 5 years before I reealized there is a left stick. You should not have to use very much throttle to fly around.

Remember keep the speed down and that should help a lot.

What is your skill level ???

I've have been flying about 2 years. I'm an expert cruiser(WhooPee). I built or should I say put together a SPAD PQHOR (Profile Quick Hell on Rails) just to make use of left over gear. If you know this plane it is a slow floppy flying plane. I realized also that there was a stick on the left side of the transmitter. And so my addiction has begun. I finally took the SPAD to its inherent limits Hover, Harrier, Elevator, loose flat spin). I hover at about 10 feet. Inverted tricks are a little down the road for me, and not within the SPADs reach. And thus the OMP 540. I did a lot of reading on RCU and found you profilers and Bros. Built my first kit, and I'm planning on growing into this plane. Maybe I could have just said "I'm an intermediate flyer". Anyway I'm hooked on learning 3D and profiles.

Here are my SPAD and 540

Dick, Pro Bro 757

Dick, very nice job on your OMP. I really like your covering scheme. I just went down and measured mine. My flying skills are still below your level so I really wanted to start conservatively and work into it. I measured the distance from the leading edge to the back of the main spar at approximately 3 3/8 inches at the fuselage. If you use the conservative 1 3/4 from the back of the main spar as the starting point for your CG, that translates to right around 5 1/8 inches from the leading edge. That's where mine is balanced and it flies great. It's a tick nose heavy right now. I also took OMP's advice and set my throws up on the conservative side. My low rates are around 25 degrees and my high rates are around 35 degrees. I have 50% expo in everything. Take offs and landings are a breeze, and it will perform most of the intermediate/advanced 3D stuff with ease. Rolls on high rates are a blur. Try yours around there and see how it flies. Actually, I'm going to have a problem moving my CG back any further-my battery is stuffed as far back in the compartment as it can go. Maybe I'll need a heavier battery.

Vince
Pro Bro #222

Thanks for the CG help Vince. I now have my battery stuffed as far forward in the wing as it will go and the CG is about an 1/8th aft of what you discribed. The squarrel characteristics are gone. Well almost. If I fly it down to fumes it gets twitchy. I like it like that though. I have about 6 planes and have never blown it on the CG like this before. Now I know what a very tail heavy plane flies like. I wouldn't reccomend trying it. I had a couple exciting takeoffs.

As far a the color scheme goes I have to credit Billy Hell for the original idea. He did an OMP much like mine. The two are different, but similar. Thanks for the complement. I really like the way it turned out. Billy's plane is on the OMP web site under the review of the 540.

Dick

Dick, glad it worked out for you. What motor are you using? I'm assuming that it's on the light side. I have a Saito 72 in mine. As I said, I had to move my battery as far back as possible to get that CG. I know my CG is about 3/8" from where most of the guys are flying, but I'm just a rookie and it works O.K. for me at this point. I'll move it back slowly as I get more comfortable. As it is, it won't flat spin very well at all, and I'm assuming that's because of the forward CG. Got to keep burning more fuel.

Are you using any expo in your Tx? That might help settle it down even more.

I knew that I had seen that color scheme before and I couldn't remember where. Of course, it was the airplane that Billy built and reviewed for everyone. I liked it when he did it and I like yours as well. Nice job.

Vince

Yeah, yours is a little more subtle, which is probably a good thing. It does look great. Mine is still flying and still looks great but that goes against all things Pro Bro. It really should be beat to h3ll or dead by now. I'm so ashamed.

Yeah Billy your plane is like a grand daddy to mine. It should have battle scares and be arthritic. Glad to hear it is well though.

Vince I'm running a TT 46 on the OMP. The plane is a bit on the heavy side (4lbs 11oz) according to the Bros. It will hover at about or a little more than half throtle, although I don't have the stones to bring it down to the deck yet. I have 40% expo on all surfaces and it still is very responsive. As long as I can get off the ground and back down smoothly I'm happy.

I can do upright flatspins with no problem. I was disappointed with how much altitude the plane lost per spin initially. I found if you finesse the plane just after you get into the spin and then go to full throttle the spin gets real tight and altitude loss drops dramatically. A nice spin. I was mainly hesitant to throttle up. Get enough altitude to work with and try it. Inverted flat spins are another story. I haven't really worked that out yet. I'm hoping it is a matter of throttle and good inputs by me like the upright spin. Also I'm still flying the plane on mild rates. I'm guessing that more elevator will help flatten the spin still. Do you know if the OMP will climb in either spin?

Dick