I know it's a stupid question, but did you set the c/g dry, or wet?

Ok.... I'll see if I can explain this in an "understandable" way. (cause I usually do things the hard way) I have the "C/G machine" from great planes or some company, and I modified the pads that the plane would sit on to accommodate a larger airplane by making a 3" x 3" square piece of 1/8" plywood with foam on one side- the 1/4" thick weatherstripping stuff you would normally use on a wing saddle. hopefully you'll know what I'm talking about- it's like neoprene almost- on the other side of the 3 x 3 piece, I epoxied an old female ball link pushrod end to it so that the ball link on the "c/g machine" would "pop" into the ball link and retain the 3x3 plates.
one thing to note, I also drew a line on the side the ball links were epoxied onto that was right through the center. this line represents the balance point as the ball link is on it as well.
now that that is done I took the wings, and drew out a couple of FINE lines about 4 to 6 inches from the root along the center of the wing tube on the bottom of the wing- both wings were on the tube so that I could use a straight edge and make sure the line that I was drawing was true.

assemble the plane ready to fly minus fluids, and use the help of at least someone else to position the plane on the "c/g machine" making sure the lines on your 3x3 plates are parallel to the index lines that you drew on the centerline of the wing tube. this should be the ideal starting C/G mark and then you just move components around and back until you have the "real c/g" trimmed from subsequent flights- Then, if you care to, you can go back and put it on the c/g machine and find out where the c/g really is-

Sorry- I know that could have been explained a lot better, but it's the best I could do to explain it-

** another note- I feel this is a much more accurate way to measure the c/g, but everyone has their preferences- tom suggests to put both wings on the tube and take a string from tip to tip parallel to the wing tube in the center of the tube and mark the tips in that location. then assemble the plane and support it with your fingers (one person on each tip) to find the c/g. nothing wrong with this method, but my fingers are like 3/4 of an inch wide, and its a bit cumbersome to move things around in the plane to adjust the c/g... just a bit more leg work.

Anyway- my 2 cents..

Sorry about the broken gear. Regarding balancing this what I do, it was posted earlier:

************************************************** ********
Mark the cg location on the flat surface that the canopy sits on.
Drill a small hole on each side of the fuselage on this flat surface
Screw a small cup hook or eyelet into each hole.
Tie a string between the two hooks.
Hang the plane by attaching a rope to the string.
Tape the canopy to the side of the fuselage in its correct location.
Put a small bubble level on the stabilizer/elevator.
Move your battery around to get the plane balanced.
************************************************** *

I've learned a heck of a lot in the last week from our 3D pro on setting up airplanes. I've been chasing the cg all over the place, raising questions, looking for any help to get the plane to fly really decent. The guy flew the plane and recommended a few changes, specifically, reduce the up thrust, increase the aileron throw, and slow down the elevator servos. All great improvements, but it still rocked badly in an upright harrier and was real snappy regardless of where the cg was when trying to harrier. He worked on it a little more and found that I didn't have equal throw on the elevator halves. Wow what a difference!!! Now instead of fighting a poorly set up plane, I can now learn how to fly a little 3D. There still needs to be more done with the elevator linkage to get the geometry equal on both halves, but it will have to wait a few weeks. We are leaving for a two week cruise around South America tomorrow.

Happy New Year!

Chuck

Hey Texaspyro, how did YOU check the cg? Tell us that and we'll help ya get it right. Sorry the maiden didn't go so well but it sounds like it could have been alot worse.

Sounded like my maiden but we got her back down safely I moved my engine out a 1/4 of a inch CG was on the forward edge of the wingtube!!

Hey, texaspyro;
I assume this is your first "big one", correct? Now, although the proper CG location is important, it is not that critical. I'd say +/- 1/2" is a good range for this Sukhoi (Tom, correct me if I am wrong). But what you really need is "Expo" on low and high rates. In the beginning dial in mor eexpo on the low rate until you get used to the airplane's behavior. This Sukhoi is rather sensitive, especially on the elevators. The are very effective. In order to find out if the CG is right on do this: In level flight roll her on her back and fly inverted. If she drops slightly she is nose heavy, if she climbs she is tail heavy. If perfect she does not require any input. Mine flies like that and the CG is centerline wing tube. Also fly her half throttle first, that will reduce her "touchiness". Good luck

I think he better get the CG right while its still on the ground! Also if his elevator is only deflecting about 2 degrees and he's doing loops he better be a 3D pro even with 100% expo, the CG is probably off by a few inches! Then he can fine tune it in the air by slowly moving his CG back from an initially slight nose heavy starting point. Just IMO.

The small Sukhoi has a reasonably wide CG range but once it gets to the aft edge of the wing tube the plane becomes rather "exciting" to fly. It sounds to me like the CH may be aft of the wing tube.

Tom's method of pulling a string along the center of the wing tube and marking the tips works just fine. If you happened to have a couple of roller stands laying about you could slide the wings off the tube just enough to set the tube on the roller stands. That would easily permit balancing on the center of the tube. A couple of folding saw howses with a half round of pvc pipe on top would work just as well.

I don't but the 2 degree deflection stuff at all but if that's what he says....

Thanks for all of the input guys! This is my first "big one" although I do have a 1.20 size Edge thats logged 50 plus filghts! That thing is a dream to fly. Ill recheck my cg when I get back in town and get her patched up. Once again thanks for the input.

P.S. I did find that one of the lead weights I had epoxied the nose was gone. I have no idea when it fell off but it very well could have been before I even took off.... I know, I know... I should have zip tied them as well....

This plane needs NO dead weight strapped to it! You should post pictures of your set up, that will help your situation. With a TOC 53 in the nose my reciever battery ended up behind my rudder servo and she's still a touch nose heavy. We need to see what's going on with your set up. LEAD in the nose ! No way! Not in this plane!

Now wait a little, Ruski. You have your receiver battery behind your rudder servo [X(]? I know the TOC is slightly heavier than my DL-50, but I didn't realize it was that much. I have my two receiver batteries and the ignition battery all the way up front and I am just about alright with my CG. I do agree, this airplane does not need any dead weight.

I have my ign batt up on the firewall and my rx batt right beside my rx well on the other side of the fuse and could use to move it back a bit but flys good now. I say move the engine forward first then start moving batterys aqnd I concure No dead weight!!

On my first flight I had both my RX batteries and ignition batteries strapped to the engine box. I know have my ignition battery next to my fuel tank and my RX batteries strapped to the receiver tray just in front of the rudder servo. I am running a DL 50 and have set up my standoffs so that I have more than a inch of clearance between the cowl and prop.

I have read a lot of different and advanced ways to get your CofG correct on this thread so far bit I just followed Toms method for marking the CofG range on the wingtips and got a friend at the field to help me using our fingers to lift the plane. For the first flights I would really recommend that you set the plane in the forward section of the CofG range and then after that start to adjust as you feel comfortable. I made every CofG change one small step at a time until I got to where it is set know and I have never bothered to remeasure the CofG.

I also only set the throws that Tom recommends as my high rates and set my low rates at half that and something inbetween for my mid rates. I do not fly 3D and have used this plane primarily as an IMAC plane and have since reduced all my rates to even lower, including changing the servo arms to smaller arms. I think my current high rates may even be less than my original low rates.

All these recommendations are only to help you find a starting point. According to some of the top IMAC/F3A pilots it takes +- 100 trimming flights before you can get your plane properly trimmed out, so do not worry about not getting it right on the first go.

Cheers
Pupmeister

I had three oz of weight on the firewall. I didn't realize it was that big of a deal. It seemed like a relatively small amount of weight for as big as this thing is. I wanted to keep the electronics bay really clean and mount everything to it just in front of the rudder servo. When I get back Im gonna recheck things and move the batts around so I dont have to use any dead weight. I have flown much smaller planes with a lot worse cg problems than this, this one seemed unique though. I was just curious to see if this thing should be this sensitive to control inputs. Much more than my Edge?

hey everyone, I to have a dumb question. What is the best battery to use on the SU. Li-Ion with the redundant system hook up. or should I use the normal battery set up?? I am new to this part of the hobby,been flying nitro for ever. thanks flyboy12

Hey Virginian, I used 1.25" long stand offs for the motor, that put my prop almost an 1" away from the cowl, makes clean airflow at slow speed. But any way thats why he needs to post some pics so we can have a look cause even something as small as I just mentioned can make a big difference.

I believe in KISS standard set up with switchs and batterys Oh well opitc ign cutoff and no reg on the ignition 3MM Li Ion handles the volts and for some reason will not run on 4.8 volts

Flyboy12, the easiest set up is 1 A123 pack 2200mah with 2 output leads going to 2 seperate HD switches and each switch plugs into a seperate channel in the reciever. No regulators, No crazy computer boards, none of that is needed. For ignition I just used a 1500mah 4.8volt NMHD pack with a HD switch to turn ignition on and off. All my switches have charge jacks built in. For an extra kill switch on the motor I just put a servo to the choke. The best part of this set up is that Tom has all this stuff available and he won't sell you something you don't need.

How many of you are using the wheel pants? I think that having them on or not having them on makes a big difference. They are located quite a bit ahead of the CG. I am not planning to and find that I need to put the batteries way up front to make the CG work out on the front 1/2 of the wing tube. Think if I had the wheel pants on, then I would have the batteries back in a more central location. Using 3 A123 - 1 - 1200 for ign and 2 - 2300 for rec. Have TOC 53 with 1 1/4 standoffs. Using all the rest of the equip that Tom supplies - spinner etc.


Bruce

Wow Skyriter, stange I only have one A123 pack and it's way back and I never put my wheel pants on. With the stock muffler it was nose heavy, then I put a canister on and I still moved the battery back some more! The wheel pants wont make much difference if I put mine on I wouldn't even check the CG. Also it's OK if the CG is more on the back of the wing tube I don't find this plane so CG sensitive, planes with thin leading edges and thinner chords are more sensitive in my opinion.

Wheel pants are always an option. On rough fields they don't last very long so many don't install them. Typically they weigh in around 4 ounces for the pair but the weight is close enough to the c/g not to have much of an impact.

50cc battery set ups are real easy. Many like to "over indulge" and throw extra money and parts at the system thinking it will make it safer or better. One 2,500 M1-A123 with one switch will handle all the power needed and more. I can understand where someone wants redundancy with a second battery and switch. In that case a pair of smaller A-123 batteries and 2 switches works just fine. With any 50cc plane it will be a very rare day to pull more than 3 or 4 amps. Hitting 4 amps would mean the servo linkages were binding up somewhere. Use an amp meter, not your ears, when setting up digital servos. Know what is happening with flight controls, don't guess.

Ignition power works very well and reliably using nicd, nimh, or eneloop AA battery packs. 1,000 mAh is all you need for a full day of flying with a single cylinder engine. Cheap, simple, no concerns about regulating. 4.8 or 6v is dependant on the ignition type. To date I have not had an ignition that did not work well using a well charged 4.8v battery in good condition, but some have reported that their ignitions won't work on less than 6v. I don't know what to say about that.

Keep it simple and keep it light. The combination will provide a great flying plane with plenty of juice to keep it in the air. It will significantly lower cost and complexity .

T.O.M, Could you explain a little more about the eneloop batteries? I haven't been able to find much info on these. Can they be soldered to make a pack, or do you need a 4 cell holder? How about charging and chargers? The little that I have seen about them they should make great ignition batteries.

Ruski, here is my Sukhoi with the DL-50 installed. the motor protrudes about 14mm measures from the rim of the cowl. That's the back plate of the spinner.

[link]http://www.batteriesamerica.com[/link] for more about eneloop batteries. Not a lot out there yet about them but they seem to be working out well.

Thanks Ruskie31 for the info. How do I contact Tom? thanks

Thanks T.O.M I also found this link
http://www.stefanv.com/electronics/sanyo_eneloop.html