Ohio RC 1/4 scale Sukhoi-Control throw?
 

Hello-My Sukhoi is 97% finished. It's taken 3 years and the company that made it is now gone. The manual has no information on recommended control throws. Right now I'm mostly interested in a safe first flight with no big surprises. Can anyone suggest some settings that won't get me in trouble but still have enough to get around the pattern and land? I can always dial in more later. The aircraft is 84" wingspan, weighs about 17lbs with a 300 Saito for power. Thanks very much for your input.

Ohio RC 1/4 scale Sukhoi-Control throw?
 

Hi JDHammer,

I have the same kit. The recommended GG is printed on the plan itself. If you do not have the plans, let me know and I will post the CG range (distance from the LE) for you.

Azhar

Sukhoi
 

Thanks for the reply Azhar. Actually, I have the CG information and it looks like the aircraft CG will turn out to be exactly as shown on the plans. What I'm really searching for is how much control surface movement I should dial in for the first flight. A club member suggested 1/2" up and down on the elevator and ailerons but he had no experience with this particular kit. What are you going to use? My manual has no information on this.

It's a great kit-a really nice canopy and cowl. Too bad they went out of business-this puts more pressure on the builder to keep it in one piece :D Is yours completed and/or how does it perform? Thanks for the info, JD

Ohio RC 1/4 scale Sukhoi-Control throw?
 

Do you have pictures?

Ohio RC 1/4 scale Sukhoi-Control throw?
 

JDHammer,

You must remember that the control surfaces are quite powerful, especially the rudder. 1/2" could be alot or not enough depending on your abilities. I would suggest putting dual rates and adding expo on your high rates. 1/2 sounds like a good starting point for high at the moment. I will be interested to hear about your first flight. BTW, what does your airplane weigh and what is your engine choice?

Azhar

Ohio SU-26mx
 

Just checking ... you're sure that's an Ohio, right ?

The reasons I ask are that

1) Ohio did not do an 84" Sukhio AFAIK - they did a 69" [kit number 140] and an 86" [kit # 130] (not being petty over 2" - just trying to be sure its the same kit).

2) You said you really like the cowl... I have the 86" Ohio SU-26mx, and the cowl was an abortion. I actually have more hours in the cowl construction than in the rest of the aircraft combined. It was three pieces of fibregalss that didn't even come close to fitting together, with a whole load of ABS louvers attached.

If you do have Ohio kit # 130, I may be able to help. I can get the rudder and elevator throws from mine, but can't get you the aileron throws - that's because the model is temporarily in storage, with the wings and fuz in separate locations. Depending on the RX battery status I may need to charge before taking a measurement, but if you are willing to wait a bit for the elev & rudder info, I'll do that.

BTW, you can see a couple of pics of mine in my member's gallery. It's G-62 powered.

Regs,
Gordon

Su26
 

Gordon, thanks for your reply. Your information has created a real mystery here-this is getting interesting. I went to the workroom and measured the wing-it is 84". Then I dug up the 1999 Ohio RC catalog I ordered it from. The specs are: Kit #130, 84" wingspan, 1360 Sq. Inches, 17 to 19 lbs. The cowl is one piece high grade fiberglass and cut to fit the firewall. I guess this means they changed it over the years. (Odd changes for a 1/4scale plane) :confused:

Anyway, yours looks great-high gloss, red, white and blue-nice job! I'm really interested in anything you have to say about it. In particular, as a matter of survival, the elevator travel, if it's not too much trouble. The reason is my experience level-22yrs flying RC but 0 in an unlimited aerobatic machine. The radio is a Futaba 8uap so I can dial in whatever is required to make a nice, easy first flight and progress from there. Really appreciate the help, JD

Ohio RC 1/4 scale Sukhoi-Control throw?
 

JD - My manual has a 1993 date on it - so you must have a newer one which has smaller wingspan and also (by the sounds of it) a much better cowl.

I will go check the elevator travel tomorrow.

Gordon

Ohio RC 1/4 scale Sukhoi-Control throw?
 

TJ,
I have the 84" version as well, been flying it for a couple of years. They changed the cowl from the three piece to a single piece because of all the complaints they received on the three piece. Mine must have been one of the first because the instructions still refer to a three piece. I'll check the throws for you and get back to you later this afternoon (plane is out in the garage). I'm using a 76 cc twin gas engine and the performance is phenomenal at 20 lbs. I use 20% expo on the controls. I wouldn't worry too much about the control throw - it's a *****cat to fly. It it's not too late I'd suggest adding a 1/4 inch break-away plate to the landing gear. With the kit design a really bad landing can mess up the wing pretty bad.

Barry

Control throws
 

Okay, JD, here's what I have on my beast:

Elevator:
High : 1 3/4", 35% expo
Med : 1 1/4", 30% expo
Low : 7/8", 25% expo

Rudder:
High : 2 3/4", 35% expo
Med : 2 1/4", 30% expo
Low : 1 5/8", 25% expo

I fly with more expo than most folk, so you may want to use less than the above. Mine is also flown on medium rate most of the time.

As Barry noted, it's an easy plane to fly. Landings too are a breeze - when I first started flying mine I enjoyed the landing characteristics so much that my first dozen or so flights consisted of a buddy & I passing the TX back and forward to see who could do the sweetest touch & go. It was ages before I remembered that I should let this aerobatic aircraft do some aerobatics ! Personally, I found that the nicest landings came from neither a three-pointer or a traditional 'wheel' landing (tail high), but inbetween - tail just a little low on touch-down. YMMV.

Last but not least, if you get a deadstick, don't forget how big that cowl is... because of the low wing loading some folk expect the aircraft to float forever - but that great big cowl creates more drag than the Extras, Edges, etc. I'm not implying that it's a brick when dead - far from it - just saying that compared to the sleeker giant-scale aerobats, you should expect a little steeper glide.

Good luck,
Gordon

Ohio RC 1/4 scale Sukhoi-Control throw?
 

Here's mine

Elevator: high rate 2" 20%
low rate 1 3/4 "

Rudder: high rate 2 3/4 " 50%
low rate 2"

Alerion high rate 3/4" 20%
low rate 1/2"

Thanks
 

Wow! You guys are amazing and I can't thank you enough. There would have been some real pucker-factor on that first takeoff without these measurements. :eek: Now I can relax, finish the rest of the building and have a good time with it. Gordon-you read my mind with your description of the landing technique, I was going to ask you about that but you covered it nicely. Collinba-You're 100% correct about the landing gear plate. I noticed that setup after it was already bolted and enclosed in the belly pan :disappoin . Oh well. Thanks to all for their assistance, I'll be sure and keep you posted with some pictures later. JD

Ohio RC 1/4 scale Sukhoi-Control throw?
 

JDHAMMER

How did the first flights go??? I picked one of these up last monday and am putting the finnishing touches on her tonight and should have her ready to go by friday evening or saturday morning. Any thig to look out for in flight... Tip stalls on landing etc. Thank for any advice you can lend.

Re: Ohio RC 1/4 scale Sukhoi-Control throw?
 

Its 28% not 25%

Randy
http://www.RCmodelgraphics.com

SU26
 

akflyer-Hasn't flown yet, still working on control and cowl details-I'm too slow :sleeping: . Also, my Hobbico Accucycle acted up while trying to charge the 6volt receiver battery. Never had trouble before but with this new 6v it stayed on fast charge, never went to trickle. By the time I caught it, the battery was very hot! May have toasted a brand new SR battery.

On the flying performance- I've communicated with 4 Ohio Sukhoi flyers. There was one fellow from Michigan (picture of his aircraft in Model Aviation Nov 2001) who experienced difficult stall characteristics. He had a landing mishap due to a tip stall and urged caution learning the aircraft. However, note that his SU weighed 25lbs with a smoke system and other options! The other 3 flyers, who seem to be around 20lbs, have no trouble at all (note Gordon Mc's comments). I guess like any other airplane, the lighter the better.

I'll be very interested in your comments on flying it. Please post if you get a chance. JD

Ohio RC 1/4 scale Sukhoi-Control throw?
 

I put the maiden voyage on my sukhoi today. I have the CG set exactly as shown on the plans and the beast flew like it was way tail heavy. Every time I would get on the elevator it would try to snap. I have the high rate set at 1 3/4" 50 % expo and low rate at 3/4" 28% expo. I will move the battery pack forward and see if that will help tomorrow.

If anyone has a measurement on the CG from the leading edge on a plane that flys good please post it

Thanks
Leonard Perry

Sukhoi CG
 

akflyer-Sorry to hear about your wild first flight, it must have taken some superior airmanship to bring her back in one piece.

Since the posts above indicate some changes made by Ohio during the production run, maybe we should start with making sure your plan CG agrees with ours. The plan measurement I show is 5 and 7/16" behind the leading edge of the wing. This is for kit #130 1999 version with the 84" wing. The other thing I noticed while constructing the tail- the horizontal stabilizer lower cradle was precut to the wrong incidence angle. It took alot of reshaping to get it at 0 degrees to match the wing.

How much does yours weigh? That Michigan fellow had trouble with tip stalls when loaded to 25lbs.

Haven't flown mine yet so can't help you with a good CG. Really interested to see how yours turns out though.

Ohio RC 1/4 scale Sukhoi-Control throw?
 

akflyer, the plans call for 6 inches back from the leading edge along the fuslage side. The 76 cc engine I'm using is a little large for this plane, I added about 4 oz of lead in the tail to get it to balance 5 inches back from the leading edge. That's where I'm flying it. It's a little nose heavy at that location but is very stable in flight.

Barry

Ohio RC 1/4 scale Sukhoi-Control throw?
 

I bought this plane ARC and it looked like pretty good craftsmanship and I was in such a hurry to get it covered and in the air for a flyin this weekend that I did not even check the incidence..... what a boner. I will check them in the morning then try it out again.

Did you have to cut out the cowling and the louvers for airflow or are they just for looks ? I cut out a few in the bottom set of louvers and am going to cut out the rest as it does not seem to have much place for the air to exit and it may be packing up on me???? Just thinking of what could cause it to fly the way it did. I have the CG set at 5" so that should not be the problem.

The plane is 23 pounds so that could be a contributing factor.

Unwanted Snaps
 

akflyer-Seems like we're narrowing it down to a possible incidence problem. The kit I got from Ohio had a wing jig with it that gave you less incidence at the outside compared to the wing root (Better tip stall protection). Maybe if you take measurements at both wings (root and tip) plus the stabilizer mentioned before it might give you a clue to this frustrating problem.

On the cowl- I've had trouble in the past with engine cooling on scale planes. My T-28, with a huge front opening entrance, overheated due to very little exit. So on this Sukhoi I cut out only a small opening directly in front of the cylinders. Then I cut out all the square exit openings where the louvers go plus another exit out the aft bottom where it doesn't show. Haven't run it yet but I hope this does the trick.

Let us know how it goes. JD

Ohio RC 1/4 scale Sukhoi-Control throw?
 

You definately have to cut out the louvers. The instruction book that comes with the kit makes this clear. I also cut a good size opening in the bottom of the cowl. Normally overheating will make the engine sag. This could effect the flight characteristics if it get a surging action. I wouldn't thing the incidence being off would make the aircraft unstable, just a little hard to trim and difficult to get tracking properly.

On my first flight I used metal bolts in the plywood blocks to hold the wing on. I "zapped" the holes after tapping to harden them. I found out later that using metal bolts in tapped wood is a no-no. They vibrated loose partway through the first flight throwing the incidence off. It was a handfull let me tell you.

Barry

Ohio RC 1/4 scale Sukhoi-Control throw?
 

Duhhhh... Checked the incidence today.... only 3 deg. off on the tail. I noticed that I had a little up trimmed into it from the one flight and that was enough to cancel out the positive incidence. It would be a major pain to bring the tail in now so I will try shimming the trailing edge of the wing and try her that way.

Ohio RC 1/4 scale Sukhoi-Control throw?
 

Changed the incidence, opened all the louvers set the CG at 4 1/4" got rid of 1# worth of muffler and lead, changed from a 22-8 to a 22-10, made a mouse can muffler and gained 550 RPM even with the higher pitch prop. Will try it in the morning if the wind calms down a little.

Let us pray
 

That should do it akflyer-we'll still keep our fingers crossed for you. :thumbup:

Ohio RC 1/4 scale Sukhoi-Control throw?
 

Flew much better and was much more stable. Still lacking in power but this has now become a test bed for mufflers and props. kinda fun trying new combinations to see just how much performance you can get out of something.

Vertical ran out quickly but it cruised around ok.

Landings were a breeze. Just keep the power on till about a foot off then chop the power and set it on the mains, run out was true with no tendency to ground loop even with a 10-15 mph cross wind.