Hey guys I know this model has been drug through the coals already. I was hoping we could get the build info all in one thread.

I just purchased one and am thrilled with the tight covering and apparent good build. My intentions are as follows

Power: Saito .82
Servos: 4 standard, one with ball bearings I will put on the elevator
I also ordered the Kyosho Sukhoi Breitling stickers.


Everything else is up for discussion.

1. Do I need to glass the wing joint? If so remind me how. I haven't done this in forever.

2. Should I use pull-pull connections anywhere?

3. Should I split the elevators? If so how should I set them up?

4. What size prop will I be using?

5. Landing gear mount. Is it sturdy enough as is?(UcanDo keeps breaking) or should I find a way to strengthen?

Any thing else I need to know as a build?

TIA
Mike

I had good luck with my Sukhoi until I got out of sync doing rolls and munched it! I don't think you need to glass the wing joint; I put pretty high loads on mine, diving into loops etc and never had trouble. I didn't split my elevators and used the supplied pushrods; no problems with them. I used Futaba S3004 servos, you need 5 total, 1 elevator, 1 rudder, 1 throttle, and 2 ailerons. I used an old Fox Eagle 60 (first type, non schneurle) with a 12-6 K series Master Airscrew prop. Totally different from your setup; you'll sure have enough power!!

I used nylon bolts instead of metal bolts to hold on the landing gear. I made a 1/8" plywood plate, drilled holes in it to match the holes in the fuselage, covered it with red ultrakote, then sandwhiched the aluminum gear between it and the fuselage. It was long enough to cover both LG struts. I used 10 x 32 nylon bolts; the plywood helps to distribute the load. With metal bolts there is NO give and you'll tear out the bottom of the fuselage if you land too hard!

I replaced the factory engine mount with a Dave Brown composite mount. I thought the factory mount was too "spongy".

Spend time with your engine and tank installation; get the tank too high and you'll have flooding problems. Install a filling system that will let you fill the tank with out flooding the engine. Cut the cowl openings so you can fill the tank, adjust the high speed and low speed NVs, and choke the engine conveniently! I cut out the louvers to allow additional cooling air flow OUT of the cowl. You MUST be able to get rid of the hot air or you may have overheating problems. The plane looks great with the cowl, but if you don't spend time taking care of all these details, you'll spend time at the field workling them out there!!

See my "Spacewalker II) post for other ideas!

This Sukhoi is a super flier and a true bargain!!

I'm just now finishing mine. What I noticed during the week or so sticking it together:

The booklet sorta screws up the motor mounting descriptions. It says there is right thrust and no downthrust. And it shows the hole in the firewall as being the centering device for your motor mount. If you look at it for a couple of seconds, you will see that that hole is offcenter. It's moved over so the nose of the engine will line up in the center of the cowling (for the right thrust angle). Unfortunately, on mine, the hole is moved as if the firewall had right thrust and UP THRUST! I measured the incidences etc and measured about 3degrees of right thrust and almost 5 degrees of downthrust. If I'd used that hole to center my Dave Brown (I also thought the supplied mount was way too flexible) the prop would have been WAY off center. Best to always check these ARFs first.

I didn't think the wing joint needed glassing but then decided to run a short piece of fiberglass tape top and bottom around .25C and short pieces top and bottom at the trailing edge and CA'd it down. That's lighter than glass usually.

My cowling was a mess. Guess they pulled it from the mold way too soon. I cut some pink foam into discs (sort of big hockey pucks) that were round and fit tightly inside the cowl. I placed the first to sit flat against the firewall when the cowl was installed. Glued it to the cowl, then stacked a few more in. Needless to say, I had to leave room for the engine and pitts muffler, but after a little carving, the "filling" did 3 things. It made the cowl round again. It supports the heck out of the cowl (any forces from the front are transferred into the foam and from there into the firewall. And it does something real good for huge open front cowls that have tiny hot air exhaust vents that aren't anywhere near the engine.... the "packing" takes away the worthless open area and directs the air to the engine and muffler. (you'll never go wrong filling dead space in an engine compartment as long as you leave a front opening and cross sections from front to back that are about the size of your hot air exhaust's area)

They show the wing servos being installed in line with the wing ribs. The trailing edge and ailerons are swept forward quite a bit. I built the servos onto their trays to be square to the axis of the ailerons. The pushrods are at right angle to aileron axis. Easy to do. Should be this way anyway.

The tail wheel assembly had some problems. The big ugly, un-aerodynamic support tray that sticks out like a lump of wood (chuckle, which it is) covered in Ultracoat like that'd hide it, positions the axis of the tail wheel at an angle to the axis of the rudder. Not sensible. And the angle of the wire is way off (no biggie). So I cut out the big lump and inlet it and trimmed it to fit and ironed some Ultracoat on. Bent the wire to match the new angles. The tail wheel now tracks ok and nothing binds the rudder (the way it was shipped would have caused lots of servo load).

I'll be flying it within a few days. Gotta run the new .46AX a few times on the stand first.

oh yeah.... I wound up putting the rx battery beside the tank just behind the firewall. It's a flat pack and the slot to the side is perfect. And seems putting it opposite my 90degree motor would make left-right balance sense. And had put the motor servo forward (instead of in the 3-hole servo tray that's built in), no reason to have it behind the cg instead of on the cg or ahead. If I assemble another one of these, all three will be more toward the front. A servo tray is dead simple and quick to make.

Mine balanced right on the suggested cg. It's a pretty decent model. Looks like it oughta fly decent. It does need some more "designs" in the paintjob. Oughta take another hour or two and slap something flashy..... nah.... time to fly the sucker....

Hey, GWILLIE, that gear mount idea sounds great. I never liked big open gaping holes anyway and the original design leaves one. I was thinking about using nylon bolts, but the split gear provided sorta kills a simple retrofit. That plywood plate solves the problem nicely.

And if the sucker flies good, I plan to swipe your paintjob! Already pulled a copy of the pictures.... chuckle.... I was figuring that the thing was really going to look the same top and bottom and something might need to be done if only for that. Thanks for the good ideas.

Gwillie,

I am having a hard time visualizing your landing gear modification. Could you show a photo or drawing for me?

thx

Here is a picture of the gear mount I described. It's on my Seagull Spacewalker II, but I used the same system on my Sukhoi.

I forgot to mention on the Sukhoi that it balanced as per instructions with no added weights. Also, I used the recommended throws to start with. Soon I increased the rudder throw to about all it would take to get nice snaps maneuvers and Hammerheads. I used about 3/4 of the aileron throw; I'm not a fan of rolls too fast to see; I like smoooth maneuvers.

See my Spacewalker II post for other ideas.

How bout a fuel tank? I am using that large 4 stroke and it will most likely drain the tank in a hurry. What size fuel tanks have been used?

And here is a picture of the modification I'm making using GWILLIE's idea. The pink foam is going to be glued to the plywood and then fuelproofed. It'll fill the void the gear attachment makes right behind the lower firewall. I'm guessing that the improved aerodynamics ought to give the a/c maybe 30 or 40mph more top end.... at least.... chuckle

Oh, the other two pictures in the group are of the cowl "stuffing". You can see from the front pix how round it's become and from the rear pix a hint of how warped it was overall. The out-of-shape at the rear is pulled out by the fuse.

The fuel tank is going to be a quest. My Sukhoi had a bulkhead that looked like it was cut for the tank that came in the box. And that bulkhead is inside another bulkhead, inside the nose. Unless you want to try cutting that sucker through the wing opening and fuselage bulkhead, you're going to be constrained by the dimension in there. I measured the "hole" in there, came up with some guesses as to what might fit, decided I wasn't going to try and get into that nose to trim the existing opening and looked around at the LHSs for anything else in that "range". And went with the supplied tank.

What did you guys use to connect the tail surfaces?

The supplied control rods for the ailerons sux. My z-bend pliers broke it in half.

I've got a stash of very small diameter arrow shafts I bought years ago when an archery shop went out of business. I'll be using them until gone.

I've been looking at carbon fiber tubes for pushrods (to save that final quarter ounce for park flyers) but been told that CF rods might cause radio interference since CF conducts. Whatever the truth of that, I weighed a fiberglass arrow shaft versus a CF rod and decided that the CF wasn't worth the minute difference in weight versus the monumental difference in cost.

BTW, the fuselage exit holes for the elevator pushrod and rudder pushrod are located perfectly if you plan to run the rods to those two surfaces' control horn's innermost hole.... which is a really bad idea for this a/c if you want to come close to the suggested rudder and elevator throws. I wound up with the rods connected to the servos' inner hole and both surfaces' horns' outer hole and still have more than suggested throws.

Is anyone out there having problems with the tail droping out on the landing approach. The plane balanced according to the manuel. Any thoughts out there on this topic. I am thinking of moving the CG. If anyone is also have a problem like this please let me know how you corrected the problem. Flying with a os .61

Azrcflyer

I have put tons of flights on mine with a Saito 50 4 stroke.
It will do almost anything with that motor surprisingly.
The Sukhoi will do just about any trick in the book.
I have done some very, very violent maneuvers with this aircraft and it did not stress any part.

It does get touchy at lower speeds though. It's good to keep up the power on aproach and chop the throttle over the runway threshold. It slows down quickly.

mine has a saito .82 also and that plane is the biggest piece of junk i have ever tried to fly. It acts like it is tail heavy and does not want to land without ballooning up with little elevator input. My friend put a os .46. The same exact thing happened but he wrecked his and mine is still hanging. Does this sound like a familiar problem with yours ? If not can you tell me how yours went.

my tail drops on mine . Can you help me with mine

The two Phoenix that I saw fly both flew very well. One was being flown by a 6 year old. One was mine.

Tail heavy airplanes give the elevator all the power it'll ever have. Most people diagnose tail heavy when they experience an elevator that feels too quick. If your elevator feels too quick, first thing to do is dial in some exponential. Second thing to do is move the elevator horn connection to the outer holes in that horn. It's actually better to move the pushrod connections on the elevator servo in to the inner holes in the servo arm. THEN check out the CG location in flight.

There are a couple of different ways to check the CG location of an airplane that work good. They are done while flying, so obviously you preceed them by verifying on the ground that the CG is where the mfg suggests before you take off. The other thing you do before flying is check to see that your elevator throw is roughly what the mfg suggests. You've done those prep things, right?

A powerful elevator isn't a bad thing (unless the CG is too far back). It's dead simple to adjust the servo-to-elevator connections and you'll have a better flying airplane than it'd be noseheavy. But check first to see if it's tailheavy.

Fly the airplane upright and inverted. Top speed works. Slow is a little risky. If the airplane tends to climb when inverted or you have to hold "up" to keep it level when it's inverted, you're using the elevator to carry the tailheavy CG. You can also do a dive test that works about the same way.

Trim the airplane for level flight at about half throttle. Use the TX trim to get a hands-off level flight at that speed. Do this at a decent altitude. Once you've got it flying level on it's own at half throttle, point the nose down between 45 and 60 degrees and let go. It will naturally pick up speed. As it does, the trim you set for half throttle will become more effective. If that trim pushes the nose down and the dive gets steeper, you've got a tail heavy airplane. The trim was having to carry that "tail heavy" CG in level flight at that slower speed, and now that the airplane is going faster (without help from the prop) the trim is doing even more trimming and that's tucking the nose under. If the nose comes up in that dive, you've got a noseheavy airplane.

That Sukhoi comes from Phoenix with a lead weight "hidden" in the nose. Phoenix did that instead of making the tail out of lighter wood or with less structure. That ought to tell us something about Phoenix and that model. Nonetheless........

CG location is really our responsibility. It's sensible to expect ARF manufacturers to do a good job of building, but keep in mind that most of them are really just toy manufacturers who've found an expansion market. CG location is still our responsibility. And installing our radio equipment is also our responsibility.

My Sukhoi flew noseheavy to begin with. If you read my first posts in this thread you'll see that I started off placing my batterypack up in the nose. It took that to balance the airplane where the mfg suggested. After flying it, it was obvious that I was flying a noseheavy airplane. (The dive test and the inverted test work.) I kept flying it like that simply because the airplane still would snap and do everything I wanted to do with it back then. Then I decided to get everything I could out of it. So I moved the battery pack back. It really came alive.

When it did, I also got an elevator that didn't need to move but about half as much as before. So I moved the elevator horn connection out. I wound up with the same feel as before when it had been noseheavy. It was no more or no less stable an airplane. Stability comes from the size and location of the tail, not much else, and it doesn't change when you move the CG. What changes is the power of the tail. Adjust the elevator to match it's new power and you got the best of all worlds. You get less drag out of that tail with less movement and the same movement from the airplane. And adjust the linkages, and your TX stick feels just as "slow" or "safe" or whatever...... win, win, win.......

When I moved that battery pack back in the fuselage, I wound up with a great flying airplane. Only problem with it was it was on the heavy side. But I made a mistake when I built the supporting structure to hold that pack. It was back in the fuselage behind the TE of the wing. Darn that airplane flew good though. But the battery wire just reached the wiring harness connector. And one day.........

The battery slipped back a bit.

It pulled the connection loose. That SNAP ROLL at speed turned into a real SNAP..... and BOOM........

I really had liked the way that airplane flew, but was really not happy with Phoenix. I'd just found the lead weight they hid in the nose and that told me one thing loud and clear. Them guys didn't understand much about building airplanes. You don't add weight, dead weight to make up for other mistakes. No way was I going to mess with them again. But dang I wanted another Sukhoi.

Well, it's been a year........ And I just flew my new Sukhoi 31. And is she sweet. Excellent isn't a good enough word to describe this one. It's Hobbico's 60size Sukhoi31. It's excellently sweet...... Put three flights on her yesterday. First time out for the engine too. both of them were good. Just about the best flying ARF I've had in a year and a half of getting back into the hobby and it's ARFs.

Lined everything up in the shop, balanced it by the book, throws by the book, and searched high and low to make sure Hobbico hadn't hidden any lead in there somewhere.......... She flew with a couple of clicks of elevator trim. Just a hint of tuck on the knife edge. Will snap inside, outside, in-out, and out-in so quick I'm still shaking. Couldn't get her to settle into a flat spin, but then I can't do them worth spit yet, anyway. A honey baby.........

It sounds most like you need to move your CofG forward or slow down your late final approach, quite possibly both.

Start by moving the CG forward to max. limit of suggested range. Use temp weights on firewall or inside cowl. Test fly, including approach config stall characteristics at height, land and adjust as necessary. And as Darock mentioned, mechanical differential (outer holes on control horns, middle to inner holes on servo arms to start), rates and expo should all be dialed in and set up for the individual model type.

do not use the nylon engine mounts that come with the phoenix suhkoi or you will have engine vibration problems. i had a enya .50 cx on mine and i had to mount the engine on the extreme end of the mount for proper cowl fit and i had vibration problems. i later used a dave brown 4-stroke mount. i thought my sukhoi was a little heavy but my enya .50 had plenty of power to haul it around. warning!...do not do medium to slow tight turns with it ,...she'll snap out !, that's how i lost mine.

Mine was just under 6 pounds. That's about the weight limit for a 46size aerobatic airplane. I've built over a dozen 46size ARFs this past year and only one of them was heavier.

I think it'd be a good candidate for the new OS55AX.

Thank for the help guys . I guess I will take it back out and recheck every thing and try again with expo and very little throws .

Hello, Did you ever get the sukhoi to fly good and balance out with the saito .82 ? That is the same setuo mine has and the only reason that its still alive is because it hangs from the cieling after 3 flights of hell trying to get it to come down and land like a normal plane. Dont want to wreck the new engine so i was thinking of puting a .61 or .46 that i have laying around the house. I would like to here how yours went if you dont mind.