smithcreek

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I just finished a Goldberg Sukhoi and flew it for the first time today. What a great flying plane, very happy. I was going to make a second flight but had engine issues. It has a YS 140 fz, and my best guess is that it was overheating. My question is to anyone that has built this kit, did you need to use any baffling in the cowl to keep the engine cool? I've read a lot of threads before and during the build, but I don't remember seeing anyone mention having to baffle the cowl. I assume everyone just uses the plastic or fiberglass parts as designed, with the air entering the front of the cowl and exiting the holes in the bottom of the belly pan, without cutting any extra exit holes.


Here's a picture of the real Sukhoi I used for my color scheme:



Here's a couple pics of mine, before the first flight just in case:

Pylonracr

You need exit area for the hot air. Figure twice the exit area as intake area. Your engine is overheating because the air can not get out.

Boomerang1

Pylonracr is correct, you have to get the hot air out and the hot air will have more volume than the cold air coming in because it's the same air expanded by the heat.

A baffle does two things, 1/ it cuts down the total amount of air coming in so there's less to try to let out &
2/ the air that does come in goes directly over the engine's cooling fins.

Are the louvres in the cowl actually cut out so air can pass through them? Might be a start if you can make them work.

This is a pic of my P-47 cowl baffles, basically the same thing you need. - John.

smithcreek

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Thanks for the responses. I'm pretty sure the air exit at on the belly pan is sufficient as it was designed, it's the air intake that's my problem, too much, not centered on the engine. The way it is now, it's right on the edge of not staying cool. First flight was fine, probably because the plane was moving. When I spent some time on the ground fiddling with the engine before the second flight it heated up. I'm going to make a baffle now and see if that solves the problem.

bigal126

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Awesome job on your Sukhoi! I just finished mine late spring. I have DLE 30 on highly modified kit. I don't believe I have a heat issue, but I did block off the top 1/3 of the cowl opening and put in some of what I'll call louvre / air dams underneath. Don't know if it's doing anything but it is what it is. I have no belly pan. The plane has two wing halves, with tube. A removable canopy on top. The wingspan is 78 (versus 72), lengthened the fuse to stay in proportion to the WS, and airfoiled stabilzer. Only gentle flying as the gasser isn't broken in (less than a gallon), but she flies and tracks really good. I would do what you said and maybe block off some of the intake where it doesnt' flow over the engine head. That cowl opening is so big, there's no way all that air can flow out efficiently.
BTW, if you don't mind I think I steal a page out of your book and do something like you did on my cowl. Mine is plain Jane and couldn't quite decide what to do with it. Also, nice touch with the wing fairings. Looks real scalelike. My plane weigh 11.8 lbs. What did yours come in at?

smithcreek

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Hey Bigal, your Sukhoi looks great! Was it a kit or from scratch? That's a lot of mods. Where did you lengthen the fuse? I was pretty determined NOT to do too many major mods while building. I was kind of in a hurry to get this done, started building it in early June. I have a couple other airplane projects going but really wanted a new "every day" flyer. I couldn't resist doing the wing fillets though. The one major mod I did consider was making an airfoiled tail, but ended up deciding not to. I did some small mods like cg located fuel tank, hatch in the fuse behind the wing where the elevator and rudder servos are located.

Your plane is practically begging for flames on the cowl. It will look great, post a picture when you get it done.

I put baffles in today, I'll test it tomorrow. If that doesn't solve the issue I'll open up holes in the bottom of the cowl like yours.

bigal126

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Mine was from a kit. Took all winter to build. One mod leads to another and another and another. Wasn't easy. I have the goldberg extra, (love that plane), but don't like lugging the one piece wing around. So after building the wing halves, decided to do the tube thing on the Suk. Came out much better than I thought. Very solid. Because the WS is 6" longer I just spliced in 2-1/2"" on the fuse just forward of the turtle deck. The gasser extends 1-1/4" longer with stock standoffs out front. The airfoiled stab was a royal PITA, but the plane tracks great, maybe better than the extra which is a great flying bird. Plus I heard the stab is a weak point on this plane with the big engines up front. Better keep an eye on it. Some put flying wires on. That 140 should pull it like a freight train. I got a YS 110 S on the extra and it's more than enough power on a only slightly smaller airframe. Some build pics attached.

smithcreek

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Yeah, mods are addictive and they add a lot of time to a build. You can frame the whole fuse and wings a few hours a night over the course of a week or two, then spend twice as much time on small mods, not half the size of the ones you did. Even just putting a baffle in my cowl today took six hours to design, cut, fit, install, paint and fuel proof. When I built my stab I made the trailing edge and trailing edge doubler out of spruce, red spruce to be exact, very strong stuff. I heard that was a problem with the stab, hopefully that will take care of it.

I changed the title of this thread so anyone can post pics or videos of their Goldberg Sukhoi, or any kit or plan built Sukhoi if they want. I searched but could not find any thread like that for the Sukhoi. The Extra and Ultimate have good threads with pictures of lots of different planes, but not the Sukhoi.

Gray Beard

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I agree with that statement 100%. I'm building the SU-29 from plans right now, a quick build until I started my mods. Just a couple more things left to do and I can start glassing.

smithcreek

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I should take that phrase, put it in one of those big red circles with the slash through the middle, have it framed and hang it in my shop. I'm scratch building an [link=http://www.rcuniverse.com/forum/m_9662771/tm.htm]Acroduster[/link] biplane and if you breeze through the thread I can't count how many time I said, just about done with something, then I can cover or glass or paint, etc. Months later and I'm still working on it.

Exactly why I was determined to do as few mods as possible to this kit. I wanted it up and flying before the season was done. I also have a goal of finishing the Acroduster and a P-26 I'm building from Royal plans before the end of the season. I just have a couple small things to do on both of those and they'll be ready for paint. (see, I can't help myself! maybe I need to get it tattooed on my arm so I stop saying it!)

Gray Beard, I know you've got a thread going on your Sukhoi, I've been watching it, but feel free to post any pictures here also.

eroc144

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Smithcreek - Absolutely love the finish! Did you paint or use plastic?

EG

smithcreek

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Thanks! The covering is polyester dress lining material from JoAnn Fabrics, dope finish with Klass Kote epoxy clear on top.

Gray Beard

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I have never tried to cover with the polyester, that came out beyond great.
Really, I'm getting close!! Been saying that for two weeks or so now. Today I have monitor duty at the wood working club, not many members there this time of year, everyone here summers someplace else. I will be taking my plane with me and instead of reading a book I will sand.
I thought I was finished with glue last week but after I made the belly pan I had to make a cut out for the LG. Now I have to make up a piece that can be removed then screw back down over the gear.
I wish I had some talent, I would love to flame mine but anything to do with any form of art is beyond me. I can use a air brush a little but can't draw a flame to save my life. I'm going to be using Latex paint.

357ross

Bigal126, how did you select an airfoil for the stabilizer, and did it do anything for the flight characteristics of the plane? I have often wondered about this, and almost all kits and plans call for a flat fin and stabilizer. It does look like a straightforward modifacation to do.

bigal126

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I chose Bigal airfoil #1. I wanted to beef up the strength of the stab because history showed it to be a weakness with big engines up front, and I like the look of the airfoiled stab. All I did was build the stab as per the plans, and then made my own ribs. They are identical throughout the length of the stab. I split the ribs lenghwise and glued them to the top and bottom of the stock stab, added a balsa square for the leading edge, and some flat balsa stock for the trailing edge, then sheeted it with 1/16 balsa. Sanded it all into shape and that's it. Frankly, making the elevator mate up to it was much more work, especially the counter balance portion.
Because I have only flown the plane very gently to this point, I can only tell you that the plane tracks really well. As good as or better than my Goldberg Extra, and better than my QQ 69" yak.

eroc144

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Didja brush or spray? Brushing dope drives me nuts, and taping / masking drives me almost as nuts...

EG

smithcreek

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I brushed on the nitrate dope to fill the weave, then sprayed the butyrate. Lots and lots of masking tape. By the time I had finished pulling off the tape for the checkerboard pattern I had a ball of masking tape the size of a basketball.

Gray Beard

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It was well worth the time and effort!! That is perhaps the best looking CG Sukhoi I have ever seen.
Because I'm a lazy ass I was going to do an air foil tail feather treatment on mine, then I changed my mind. Then I was going to add wing fillets but changed my mind. Then I saw yours and decided it was well worth the effort, they really are cool. I was just out in my shop making up the template for the wing fillets. Then I noticed that dumbass married to my wife did the cut outs for the two switches right where I wanted the fillets to go. Best laid plans and all that!!! If i could just keep that dumbass out of my shop!!

chrisp32

Is that on old kit I have never seen on listed by goldberg. You did a nice job of it

smithcreek

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Thanks Gray Beard. The kit has been discontinued quite a while, not sure exactly when. It's still fairly easy to find, but not as easy as the Goldberg Extra. On RCU classifieds you should be able to get one for $200 or less, on ebay usually a little more. One just went for over $300 on ebay, but I've never seen one come close to that before.

Gray Beard

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The kit was discontinued before lanier bought CG. {as i recall} it's been a number of years anyway. I wanted to build both the CG Extra and th Sukhoi, sort of a pair thing going on. When I was ready for the Sukhoi it had just been dropped. That was a long while ago.Even then both the CG Extra and Sukhoi kits were getting close to the $200.00 mark. I think it was $189.00. Then you were going to buy the glass parts for them from FGS so they came out over two bills.
Smith, I posted a photo in the scratch for you, I just started the first part of the glass work today. I should be laying the glass on Wednesday or Thursday. My wife starts her weekend tomorrow and I hang with her so nothing will get done for a couple of days.
Gene

AmishWarlord

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Very nice SC. Love it!

RICKSTUBBZ

Smithcreek,

I just want to add one more compliment to a job well done. Fantastic looking plane. You found an excellant example to model yours after as well.

bipeguy03

Smithcreek, That is a fine looking Suk!!!

As for your heating problem I built a baffle system from .010 6061 aluminum. two peices, veary simple, and enlarged the opening in the bottom of the cowl around the tail pipes.. I am running a Super Tigre 2300 on mine and never had a cooling issue.

Here is the link to my build 5 years ago, on page 7 is a picture of my baffle.. hope it helps!!

http://www.rcuniverse.com/forum/m_51..._1/key_/tm.htm

smithcreek

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Thanks guys. Bipeguy, I read your thread a couple times before and during my build. I went back to it after I had the overheating issue and saw you did use a baffle. On mine I was able to fix the overheating issue. First I tried just a baffle, that didn't work. It may have needed a baffle, but that wasn't the only problem. I used an oversize spinner on, 4" and that might have been blocking too much air from entering so I got a new 3" and put that on.

On top of that I bought that YS-140 used on ebay for $200. I bought all the parts to overhaul it but thought I would try running it first to see if I could wait until this winter. I happened to be adjusting the valves on another engine, so I pulled the valve cover off the YS and the exhaust valve was WAY out of specs. Supposed to have clearance of .004 - .010, it was .025. I adjusted that. Took it to the field and it runs great, I also got about 700rpm more. So I'm not sure what the cause of the overheating problem was, may have been a combination of those things. I put about 12 flights on it this weekend and it's a nice plane. Tracks nice and does some great aerobatics. I'll post a video when I can get someone to run the camera.