Crazy4Flight

My Feedback: (540)

try a samll o-ring between the wheel and the wheel collar

jimcork1

My Feedback: (4)

I assume you are on a paved runway?

Otherwise your engine should idle down enough to not be moving. If on paved runway you might consider wheel brakes. I have tried the tighten wheel collar trick and you will never get them even. This will cause take off and landing issues. Balanced braking is the way to go. Most jets r/c use wheel brakes and they are available.

cam425

My Feedback: (1)

That would work very well but I would have to upgrade from my DX7 to another radio and I can't afford a more exspensive radio and reciever right now. If my engine would idle at 1600 like its supposed to I would have no problem. I am working on the setting for my engine to try and achieve that.
I have an O.S. 160 twin four stroke that's brand new and I wanted to know, do you think that would be enough power to hang on the prop and do just about everything the plane is capable of? The reason why I ask is because I could use that on the suhkoi and save the 30cc for another plane I hope to get in the future(A pilot rc green and black extra 260 found at chiefaircraft.com).

jimcork1

My Feedback: (4)

I would expect the OS 1.6 twin to have about the power of a OS 1.2 single cylinder and I would expect it would fly the sukhoi well.

I would recommend cool power 15 % Green for the OS and add 1 oz castor only.. just 1 oz..

Use os F plug and you will have to lean out the low speed a LOT to get it to idle. I have been working this week on a OS 5 cylinder 300 and we have gotten the idle to about 1600 rpm but we are using glow drivers on each cylinder at least until break in.

Best of luck.

cam425

My Feedback: (1)

Two more questions for you, what is the best way to break in the 1.60 and do you think it will hang on the prop with that motor?

jimcork1

My Feedback: (4)

Hang on the prop.. Don't really know until it is flown. Probably won't hover,, mine won't hover with 1.8.

However breakin. I would use coolpower 15 % fuel 1 oz castor added.

Crank set needle about 4 turns open, ( 3 is probably enough). Crank the engine and leave the glow lighters on. It will drop a cylinder if you remove them.

Open the throttle to full throttle and lean the engine using a tac until peak rpm then drop 200 to 300 rpm and immediately pull the throttle back to about 1/2 full. Run it about 3 minutes shut down and cool off.

Repeat the start run about 3 to 5 minutes at 1/2 throttle. Cool down. Do this for 30 minutes run time. (NOTE glow drives on all the time.)

Now after 30 min crank, warm about 1 minute at 1/2 throttle and check top end again with tac. Now lower rpm to idle and let it idle about 30 seconds. Rapidly advance the throttle to full and if no smooth acceleration lean the idle mixture screw about 1/4 turn. Let engine cool and repeat until nice transition is sustained from idle to full.

NOW after cool down restart let it run to 1/2 throttle remove lighters and see if it will keep both cylinders on line. After breakin both will stay on line but prior to breakin it may drop a cylinder. If the idle is still good recheck the top end for the 200 to 300 rpm drop off peak.

This is the way I would break it in. Others may do it different but this worked on the OS 300 5 cyl and the Saito's

Note you probably want the prop full throttle rpm to be around 8000 rpm. But I am not sure what the OS manual specs state on this part.

lrod

Hi Jim.

Could you please let me know what's the recommended CoG position?

I finally got the time to put it together and found out to my chagrin that it came without manual!!! [sm=confused.gif] (I'll send an email to the seller asking about it...)
I think I can get by ok without the manual. Except for the little detail of the position of the CoG.
I already partially ran my 40cc gas engine on the bench and mounted it on the plane, including the cowl openings (which were a pain to do...).
I've mounted the engine as much aft as possible, since this one is clearly on the heavy side (hope it's not too much, though...).
Unfortunately due to this I had to mount the cowling almost an inch back from it's regular position, for proper propeller clearance. This disrupts the continuity of the paint scheme... not very pretty... but, all in all, I'm quite happy with the results.
The cowl is big enough to contain the engine head. Half the carb is outside (which is ok and allows access to the choke lever).
I also made some extra holes for cooling purposes... hope they're enough.
Also... I've already mounted the throttle servo with a long GF rod (we can't be too careful about RFI with these gas engines).
I'll post some pictures as soon as possible.

I hope I can fly it in a couple of weeks... maybe sooner.

Thanks in advance.

jimcork1

My Feedback: (4)

I will check cg later this week. Just got back from being out of country for 3 weeks.

viper1676

My Feedback: (14)

Per the manual- the CG is 100MM(4") back from the leading edge of the wing. Measured at the Fuselage Sides.

Kostas1

Any pictures available ?

jimcork1

My Feedback: (4)

Pics attached and my cg was also the 4" point. With the gas burner you might have to add some tail weight. Also consider larger wheels.

lrod

Thanks, Jim and Viper!

4"... hmm... that's quite a lot...
At the moment, my CG is roughly positioned at the wing tube, with all the surfaces and servos installed and the RX batt at the rear tray.
I don't know, at the moment, the position of the wing tube from the leading edge (I don't have the plane with me right now) but I guess it's less than 4"... although not too much, I hope...
I'd like to avoid adding extra weight but... since moving the battery back is not very feasible, I guess I'll have to add some lead weight at the tail.

BTW, I'm installing the gas tank above the wing tube, closest to the CG as possible.

Yes, Jim: I considering bigger (and tougher) wheels. Thanks for the advice.
I was considering it from the beginning, mainly to add extra clearance for a bigger prop and to deal with the rough surface of our runway.
Now that I had a look at the included wheels, I'm even more convinced... since they don't look tough enough to handle the weight of my engine.
I don't have a good opinion about these foam "tires"... I've seen them get deformed and worn out very easily on other planes.
Also, a bigger set of wheels would allow me to go for a 19" prop. Currently, I have a 18/10... I guess it'll be hard to hover with it.

Will keep you posted on any developments. Currently, I'm only able to dedicate 1 or 2 hours daily to this project. So, keep your expectations low...

Looking forward to more news, photos and videos on this thread.

jimcork1

My Feedback: (4)

How are folks doing with this bird.

Update.

Saito 1.8 keeps shaking muffler loose forcing landing.

Tail wheel bends easily and will need replacement.

Covering pealing off the wing from the front of the blue cover to the trailing edge of wing.

I installed 1/4x20 nylon wing bolts from inside the fuse vs the wood screws that hold the wing on.

Landings aren't a happy time. Either it stalls and drops nose straight even hard into ground or hotter than a pistol and floats to the end of the runway.
I think the elevator position behind the wing is resulting in loss of control in slow flight when trying for a 3 point touch down which results in total loss of up
authority and the nose drops.

Flying faster gives smooth airflow and good lift but uses the entire field. There should be enough lift from the wing given area so my $$ is on the blocking
of airflow to the elevator. Haven't figured out how to solve it other than flaperons.

Any other thoughts.

Would I buy this plane again. Nope! My Extra 300 flies better.

jimcork1

My Feedback: (4)

Update on the Sukhoi. Don't know if anyone is reading but this is the latest.

I solved the Saito 1.8 muffler loosening issue by replacing the muffler with pitts style muffler that has extra support by attaching to engine mount lug. This solved the problem.

The CG was dead on the plans so I moved 4 oz from 8" in front of the CG to 8" rear of CG. (Battery moved to just infront of trailing edge of wing from leading edge of wing.

Dang if it didn't fly and land much better. I actually got it to spin for the first time. Landings are now 3 point so my guess is the CG on the plans is too far forward trying to be conservative.

The tail wheel is !@#$ and keeps bending so I added a bolt / nut through the coil to stiffen and straightened the tail wheel. Might need a new tail wheel.

While flying and finally flying nice I did a quick pass over the field and saw the ailerons flutter. I am using digital servos with 4x40 linkage and ball links with sealed controls. There should be no flutter much less flutter I could hear. Landing discovered that the aileron servo screws had worked loose allowing the servos to move enough to have about 1/4" of play way too much. That ended the flying for the day.

Got home and inspected the plane and found the flutter had cracked the fuselage behind the trailing edge of the wing at the bulkhead where only the plastic skin held it together.

Fiberglass and resin for the patch on the inside so it doesn't show. I made a gussed from marine resin and baloons filler for both side. Now it is repaired and much stiffer.

Covering. The blue covering on the right wing is pealing off as it has the leading edge of the cover OVER the red. IT should have been covered from the rear to the front of the wing so the leading edge would have air flow pass smoothly over vs pulling up on the covering lip and pealing it off as it has done. This repair has not been done yet.

There is hope for the plane as it was finally flying nice with rear CG. I haven't actually measured or confirmed the cg but if you have one on CG consider about 4 to 8 oz rear to the wind trailing edge.

Best of luck I would be interested in anyone else flying this bird.

BTW the wheels are a bit small for grass field and firm with little cushion for landing resulting in bouncing.

viper1676

My Feedback: (14)

I was actually going to have to do some fiberglass repair too. When I dropped it from the deadstick, the seam directly in the middle of the belly is split. It's right on the seam, so you can barely notice it, but it is split and will probably vibrate like crazy. This might be something I play with over the winter along with a switch to the DLE 30. The 1.20 was ok, but it seemed a little under powered to me. I got a Yellow aircraft Edge from buddy of mine late last year that I put a Saito 1.50 in. That's my plane of choice right now, plus I'm almost done with a Slipstream Sbach that I'm putting a DLE 30 in. Should be a rocket with that engine.

jerrya

My Feedback: (4)

jimcork........ I would appreciate knowing the new CG measurement on your plane if you get the chance to measure it. I enjoy following the information that you post on the Sukhoi.

jimcork1

My Feedback: (4)

Next time I take it out I will check the cg. Moving it to the rear makes it fly much better. It was a dog with cg at plans recommended.

But note,, I fly all my planes tail heavy so they spin better. You may not want to fly where mine is.

I plan to move the CG further to the tail after my next flight.

ya33a

Hi Guys,

I've been following this thread for a few months now, I bought the ASM SU-26M Sukhoi a couple of years ago with the thought of putting a 26cc 2 stroke or my new FG20 Saito 4 stroke in it. Luckily for me I didn't do either and after moving house and building a modelling shed I finally got the room to assemble this plane, I bought the Sukhoi because I love the lines, I bought the ASM kit because I thought the shape was closer to the scale shape than most of the others on the market, I'm not into 3D flying and love the way the plane preforms zoom flybuys and large loops without building up a lot of airspeed in the dive. So I waited and waited to be inspired to to get started on a build.....THen as it should happen I was presented with an opportunity too good to refuse and secured a brand new Saito 325 R5 a 54CC 5 cylinder radial engine, which I just had to have, so after promising the minister for finance and making all sorts of promises I secured the engine, (I'm still grinning)...

So now my dilemma how do I fit the engine to the airframe? Will it be to big? What size prop? How will I run it in? Can I afford the fuel bill?

I can't wait to get started.....

Will post a few photos soon of progress.

ya33a

Oh,

Just some spec's on the Saito 325 R5 engine, the prop is a 20x8 'Classic' with a Kelio exhaust ring, I have the separate pipes and the flexible exhausts as well, I need to look at whether or not to cut the fire wall off the plane and fit the engine directly to the front or to use the existing engine box and fix the engine to the box with a flexible mount to reduce vibrations. From what I've read the engine doesn't vibrate as much as the gas engines, so I might not need any extra dampening, any feedback would be appreciated.

jimcork1

My Feedback: (4)

I use a Saito 1.8 in my sukhoi and it is now flying great. Finally got the flat spins down.

I would be concerned on the weight of the 5 cylinder. I have flown the same engine on a Great Lakes Trainer. The first flights were white knuckle due to dropping cylinders. Then with glo drivers able to keep the cylinders lit and lost a plug. After about 2 hrs running and dialing in the engine it is better, (don't read I am satisified yet).

If it were my sukhoi I would not put the 5 cylinder due to weight and not fitting the cowl.

If you want a fun flying plane use the 1.8.

Best of luck. Remember this is only my opinion never having mounted the 5 cyl to the sukhoi.

ya33a

Here's the preliminary fitting of the engine and sizing for further refinment, I will be fiting rocker cover fairings once I cast them and fix up the split cowl flaps by opening them up. I used a 4" grinder to cut the cowling up to size, it looks fantastic just sitting inthe plane

jimcork1

My Feedback: (4)

Let us know how it works out. Best of luck flying.

ya33a