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Old Mar 29, 2004, 09:37 PM
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Winter Park, Florida, United States
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The RealMcCoy's Sterling Sukhoi Su-26 Conversion

Well my hands are sore now and about one and a half hours and three exacto blades later I have finally cut all of the wing ribs for my little baby Sterling Su-26 Sukhoi free flight rubber band conversion.

It is a project that I started awhile...quite awhile back and never could get past the flat bottom wings. At first I thought it was just going to just be a little novelty of a plane that was cute but after I began building it I realized that it had very good scale lines and I feel it is going to be a great flyer. This is why I could never get past the flat bottom wings from the kit. I started to think about ways to make the wings removable so I could finish it and then build symetrical wings later but that was making it more complicated with two servos and wing bolt and such. Well about a week ago I found a website Erik's Website which has plans of an awsome scratchbuilt electric Sukhoi Su-26 with about a 58" wingspan. Check it out it is artwork. It is to bad the guy says he lost intrest in R/C and maybe will get back into later. He is a real craftsman.

Well to make a long story shorter I basically used his autocad plans and scaled them to the size of my baby Sukhoi and am now building the symetrical wings that stalled me before.
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Old Mar 29, 2004, 09:38 PM
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Here is the airframe so far and I will begin to build the symetrical wings shortly. I also will be doing some sheeting on the fuselage to make it look more scale and cleaner when covered.
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Old Mar 29, 2004, 09:39 PM
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Here is the scaled down plan with the flat bottom wing on top of it to show the scale. The symetrical wing will be slightly larger but just barely.
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Old Mar 29, 2004, 09:40 PM
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Here is the difference in the airfoil on the bottom of the wing.
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Old Mar 29, 2004, 09:40 PM
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Here is the difference on the top of the wing.
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Old Mar 30, 2004, 09:54 AM
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I know some of you guys had done this conversion before because I had read the threads a long time ago. All of the threads just seem to end unfinished or without much flight information.

Any flight info would be appreciated.

I was wondering what power setups were used and what AUW or airframe weights...more so the airframe weights so I can calculate my wing loading with my intended setup.

Right now I am considering the Typhoon-6 outrunner which weights 1.5 ounces and a 2-cell LiPo. There will be 3 Hitec HS-55's, Phoenix-10, GWS Naro or Hitec Electron-6 receiver in my setup so my weight for elec. componets will be somewhere around 6 ounces. Covering will be Micafilm. Thanks, Earl
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Old Mar 30, 2004, 10:26 AM
Balsa Flies Better!
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That seems a bit heavy to me. Oz are critical on these airplanes- I'd look for lighter gear. There are certainly lighter motors, covering, servos and rxs- at least drop down to HS-50s. Might check out Micro Rotex or similar motors, but I wouldn't be surprised if an IPS on a 3 cell Kokam 340 pack wouldn't do the trick. It's cheap, light, and apparently powerful- I run the IPS on a Guillows 17" FW 190 on 2 cells, and that does fine.

Sam
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Old Mar 31, 2004, 01:22 PM
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I don't have much experience in these smaller aircraft so what would be an ideal wingloading and what would be an acceptable wing loading for this size and type of aircraft.

I have a 6lb. Sukhoi that has 561 sq. in. of total wing area which would give me a 24.6 ounce wingloading and it flys like a dream. No it is not a funfly aircraft and is not what I would call 3-D. But is a scale aerobatic plane and that is what it flys like. It will jump up and bite you when you become complacent and think you have it whipped. If you panic and/or over do the controls she will snap and scare the crap out of you.

I know that the relative size of the aircraft with the air molecules all being the same, that this has something to do with it and that high wingloadings on a larger aircraft may be okay I'm not sure. I just know that there is alot of emphasis placed on a light wingloadings for these conversions to work. However, realistically this Sukhoi is not too far off in size from a speed 400 aircraft like Jim Ryans models or GWS warbirds which are around the 17-20 ounce range.

Please correct me if I'm thinking the wrong way. I know lighter is better and by all means I am going to watch every bit of weight I can. But a Sukhoi is not a Piper Cub. But for an aircraft that is highly aerobatic of this size...26" or so what would be an acceptable wingloading?

My calculations show a possible weight of around 10 ounces with a Typhoon-6 outrunner and a 2-cell E-tech 1200 LiPo. Giving me about an 11.5 ounce/Sq. Ft. wingloading. This setup would be about 1 ounce heavier than an IPS setup and a 3-cell Kokam 340 but give much more thrust. I am getting this info assuming the airframe will weigh 4 ounces so I don't know how far off this will be lighter or heavier. Earl
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Old Mar 31, 2004, 02:21 PM
Balsa Flies Better!
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Earl

Comparing wing loadings will get you into trouble- wing volume is more useful, but much harder to measure.

There are two areas of concern- flyability and landing loads. While I think your proposed airframe would be flyable at those loadings, I don't think it will survive it's first landing. (and the wings might fold) Previous attempts at a Sukhoi posted on this board wound up with something that flew, but the batteries took out most of the airframe upon landing. The structure was designed to handle loads of some 2 oz as a rubber powered airplane. As such, it has reasonable survivability in a landing- even the less than graceful ones that sometimes happen to rubber powered aircraft. You are proposing increasing the weight by 5X. I doubt the structure can even come close to handling that. If you want to fully sheet the airplane, that's one thing, but this type of open structure just isn't intended for those kind of loads. If you elect to beef things up, you run into the vicious spiral of weight and power. Mind you- I happily fly a Wren biplane- 20" span- Astro 010 3 cell li-poly- 80 watts or so at 10 oz? (around there- might be up or down a smidge) so I certainly agree that an airplane with sufficient structure can work in this size range with lots of power. But at that point- you have to throw out the parts and just build from the outline.

If you want to keep to the kit structure- then I'd shoot for 4-6 oz or so- this is double the rubber powered model at least- so beef up the landing gear- but you'll probably have enough. My FW 190 weighs in at around 3 oz- can't tell if it's got landing issue- I've had servo issues, and each time it's dorked. Nice to fly before that though- and rather fighter like- not rubber powered airplane like.

For gear- don't know if I'd pick Cirrus servos- I'm having issues- I think. Others have also reported problems. I'd go with the little FMA jobbies- they're lighter than the HS-50s which are very nice. Use Solarfilm Lite- Micafilm will warp that structure in a heartbeat and is way too heavy. Airspan or tissue are other alternatives.

You can get away with ailerons on this airplane- try the Wattage strip setup- nice and light and adjustable. I might put on a rudder just for ha'has. I'd pick an IPS 50B with 3 cell li-poly swinging a 7-8" prop.

Sam
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Old Mar 31, 2004, 03:48 PM
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Sam,

Thanks for the input I will put some more thought into my setup.

My structure will be significantly stronger than the original kits design. Right now the only thing I have used from the kit were the fusalage formers. The balsa stringers were crap and I used bass stringers throughout. I have 1/32" sheeting to be installed on the top turtle deck and the top of the round fuse in front of the cockpit. Also I plan on sheeting the bottom of the fuse where it is round from nose to tail. The sides will be left open. The wing is entirely new and different in design from the kit. Fully symetrical and will have the front D tube sheeted and the center section to the second rib the rest will be open structure. So my airframe is nothing like the kits so to speak and I'm sure it is heavier as a result.

When I first started this kit it was going to be as light as I could possible get it. I felt it was just going to be a novelty and I would be happy just to get it to fly around the field. Then comes my Herr Stearman which I felt the same way about. Well that Streaman is probably my favorite flying electric aircraft right now and I have been flying it almost 4 days a week for 6 months in an average of 10mph winds. She is full four channel and snaps quicker than my 58" Kyosho Sukhoi. She will do the aileron rolls, loops, avalanches, hammerhead stalls, and the prettiest spins. I land her in the grass and asphalt and do touch and goes all day. I can chase the combat wings around because she is fast but she slows down and I can fly her at half throttle and she fly very scale like.

The Stearman is getting close to 13 ounces....maybe more as I have changed power systems a few times but she has alot more wing area than the Sukhoi. She is powered with a Himax 2025-4200 in a GWS EPS-400 gearbox at 6.3:1 turning an APC 8x6 slofly prop with a E-tech 1200 3-cell LiPo and a Phoenix-25. This setup pulls around 7 amps. This motor is way overkill but I wanted to be able to run a larger plane with it in the future and didn't think the Stearman was going to last very long. I also use this motor in my Jim Ryan Bearcat with a 3.2:1 planatary GB and a 3-cell Thunder Power 2100 pulling around 17 amps.

This Herr kit is excellent and is built just like the kit calls for with very few additional reinforcements internally for radio gear. When I first started flying her I had a bad receiver and she got dorked in and the wings ripped off and the landing gear mount broke but she had impacted at a 30 degree nose down attitude. I fixed her in one night and had her flying the next day she was banged around that day a few times while trying to get the CG right. Since then I have pranged her a few time cartwheeling and flipping over but she is hardely ever broken. I once had a mid air collision with a GWS Tigermoth while talking on my Nextel(I know I now leave my phone in the car while flying) and the top wing ripped completely off in flight. Thankfully, I hadn't installed the flying wires and the wing separated clean and floated down like a leaf. Well my new monoplane Stearman nose dived for about 30 feet and I pulled her out and she turned into a pylon racer and I flew her around the field and landed in the middle of the field at about 30 mph. It was dark and I couldn't see how she ended up only that she had flipped over on landing. When I got to her she was sitting there right side up looking like a PT-19. All that was wrong was that she had a stress crack in the wing that was easily fixed. I am probably the only person that has taken off with a PT-17 and landed with a PT-19.

I flew her this past Saturday in 10-12 mph winds and flew her for 42 minutes continuous.

As you can tell by my novel I love her and I am hoping to have a similar experience with the Sukhoi. This is why I started to rethink things and decided to redo the wing and make it symetrical and beef her up a bit. But you have brought up a good point and she does have about half as much wing area however, my Sukhoi setup will definately be lighter than my Stearman.
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Old Mar 31, 2004, 03:51 PM
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Here is my Stearman awhile back at a reunion where she saw her mother for the first time. Earl
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Old Mar 31, 2004, 03:54 PM
Kansas is windy.
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Stearman

To complete the scale effect you need a little oil stain underneath yours!
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Old Mar 31, 2004, 03:55 PM
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Here is a close up with her new Navy scheme.
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Old Mar 31, 2004, 03:57 PM
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One more. Here is a rather funny action shot that was captured as some pictures were being snapped of my buddies Kyosho Super Stearman as it was being given a preflight and I tried to sneak in the picture. What got captured was the dork of a landing.
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Old Mar 31, 2004, 04:01 PM
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I forgot the oil.
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