spd101

Going to do my first giant scale bird and i have a zenoah g-38, need suggestions from all the gas engine giant scale guys. I have flown for 13 years and biggest planes to date are 60 size warbirds. Thank you all in advance for your time.[*] [*] [*]
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w8ye

My Feedback: (16)

Mount it on a bench or something out side and run it some first so you can get used to it.

spd101

Very true, better to run it on test stand and get any bugs worked out, i usually break in my nitro engines on a test stand but i know it wont be able to stop the g38 lol i will definitely make sure i make something very beefy, any advice on a stand?

pe reivers

Gas engines dislike being run on a test stand. It is good to get to know your engine, but refrain from running full bore for longer than three seconds in a row. The engine will run too hot if you run longer.

spd101

This is why i like being a part of RC Universe, getting help from other people in the hobby that will give the advice from their experience to keep me from making a bonehead mistake Any and all advice is appreciated

a70eliminator

Ttotal weight would be my concern, thinking maybe about 15lbs max. Not sure what that 38 is capable of? I own a us41 and it starts and runs nice but I also have to put something together for it, I like bipes.

nh4clo4

My Feedback: (33)

you can build a Dynaflite Decathalon, I have a G38 in it and it flies great, This is also my first Gas bird.
ED

spd101

That does look good, does dynaflite still make it?

nh4clo4

My Feedback: (33)

thanks,

Yes, Great Planes bought them, so it is still readily available.

http://www3.towerhobbies.com/cgi-bin...LXYXJ7&P=0

It builds pretty fast, The g38 balanced it perfectly.

Ed<br type="_moz" />

skillet92

Second that one. Gas engines unlike glow do not need a ground break-in like glow. Set the nettles for a reliable idle, a good transition, and a consistent top end and get her in the air. Adjust a little bit after each flight. IT WILL CHANGE from the ground to the air, Especially if it is cowled. Good luck. And you did pick a good engine. I have a Ralph converted G-38 in an ESM Corsair that is a sweet running engine. My Corsair is pushing 19 pounds and it flies great on an 18x8 xoar!

jwrich

My Feedback: (17)

I have been flying Zenoah 38s for over 30 years. They are great for the right type of airplanes, they don't perform well in the 3-D airplanes or the fast movers, but they are great for the 1/4 scale Cubs and 1/4 scale Biplanes. Once you understand how to run them, they are very user friendly. I recommend the spring starter and the Carb. likes to be wet for easier starting. Some of my 38s, I have had for over 10 years. Just get with the guys in your club who fly gas engines for help. Here are pictures of some of my 1/4 scale airplanes; the Fokker D-VIIs are 24 & 25 lbs and the Cub is 19 lbs. The Cub I use for taking overhead pictures and towing banners & sailplanes up.


Rich

Whistling Death

G-38's are some of the best warbird and scale plane engines that there are. Heavy for the extra weight you need in the nose anyway and powerful enough to do the job.
I had one in an 18lbs. Hanger 9 P-47 150 and it was a great combination.

a70eliminator

Wow I didn't know the g38 was that capable, I built a 1/3 sacle bipe that weighs about 18lbs and didn't want to underpower it so the my US41 which i'm hearing is real close to what the g38 is still sitting on the shelf and bipe id powered by a a saito twin 300. I think the 38 would be fine for a slow flying easy cruising ship as you all already proved, but can it pull an 18lb plane vertical?

vertical grimmace

My Feedback: (1)

I know for sure it will pull my Fokker DVII vertical a little bit, but not much. I am wondering what the best prop is for this engine. I had run 20-8's and 19-8's, but I think even the 19 " is too much. Maybe an 18-8 is in order? I love this engine though, and recommend the spring starter as well. Mine has performed flawlessly for 4 years and has never not run or deadsticked. (other than the time my stopper came out of my tank and it did not get fuel. My fault).
I would not look to it for speed or as an aerobat engine, but a great, reliable power plant for scale models.

skillet92

I run an 18x8 and the engine runs up good and has a great top end. I believe I am going to go to an 18x10 this year for more speed.

Whistling Death

18X8 is a perfect prop for the G-38. 18X10 is a good warbird prop. I had an 18X10 on my ESM Bearcat (before I broke the landing gear out on one side) and that ran well and was fast. I don't remember the weight of hand but I know it was in the range of 16+lbs.

jwrich

My Feedback: (17)

On both my Fokker D VII's with the Zenoah 38, I run a 20 x 8 master air screw simatar . These are terrible props, the finish is bad and the balance is way off but I sand off the finish, balance, stain, paint the tips brass covers, then clear coat/balance them. They look great and they pull my 24 lbs. Fokker D VII very well, I can perform a loop from level flight. They work well for me.

Rich

w8ye

My Feedback: (16)

You still need to play with your gas engine some to get used to how it operates.

You are not going to harm it by running on a test stand.

It is you that needs to be broken in more so than the engine.

vertical grimmace

My Feedback: (1)

I guess the biggest problem for me is that I fly at over 5000' altitude. I do not get the performance you will at sea level. My Fokker really needs all the G38 has to offer at my altitude. Definitely gonna try the 18-8 this summer.

jwrich

My Feedback: (17)

Vertical, I come to Denver at least two times a year, my daughter lives there. This year I thought I would try to make the big war bird event in September. I am worried that engine would pull as well. You think just changing props will be ok?


Thanks
Rich

flyboydale54

Running all engines on a test stand for me is the best thing I can do to make sure the engine gets broken in some before trying to fly it in any of my RC Airplanes.  However, I have come up with a method that works flawlessly and will keep the engine from running too hot.  First and foremost, I leave the engine rich on the high speed.  While I am breaking it in, I do not care if it idles well, as that is not my purpose on the first few tanks of fuel.  Secondly, I have learned from a pro that the best way to break in any engine is to run it for 1-2 minute durations at full throttle.  Then shut it down and let it cool completely, followed by repeats of this for a couple tanks of fuel minimum.  Then I increase the time and let it run for 3-4 minutes, shut it down, and let it cool between runs for another 2-3 tanks of fuel.  For reasons I believe in very much, I then increase the time to 5 minute runs for an additional tank or two.  Then and only then do I put the load on the engine by putting it into the model airplane.  The reason for this is because the engine crankcases, cylinders, pistons, rings and bearings all get hot when the engines are new.  The other reason is the metal expansion and cool down is what breaks it in best and I have seen a major difference when I use this cool down method of limiting the time run before shutting it off and allowing the engine to cool.  By using this method I have experienced more powerful engines consistently, as well as not overheating them during the break-in which is very important.  The cowl does not need to be on the airplane the first few flights.  I prefer to run without the cowl for at least 3-5 tanks of fuel.  I have seen several people insisting on breaking their engines in on the airplane in the air, or worse yet, on the ground with the cowl in place.  I need not convey the huge cloud of smoke coming off the engine and what this does to the engine.  Bottom line, it ruins it permently, in my opinion and in my experience.  Once you overheat the crankcase, cylinder and piston ring to that point, the engine is junk and will always have tuning issues.  I use another neat tool to make sure the engine is getting plenty of air blowing across the cylinder and head.  Many people have told me how unsafe it is, but with a little forethought, there is no danger in using a box fan turned on high in front of the engine.  Naturally you can not expect the fan not to be pulled into the prop if you just set it in front of the engine.  But, if you anchor the box fan down in a rigid frame structure, this will never happen and you will not smoke the engine as long as you are running the engine rich.  As the engine loosens up, I then lean the engine just a litte at a time on each run after that until I feel it is breaking in some.  It is at this point that I lean the low speed and the high speed just enough to achieve a reliable idle and smooth throttle transition.  My personal preference of using this break in method will achieve consistant breaking in of the engines.  Hey, try it and see the difference it makes.  I know one thing, you will not smoke the engine using this method and it will consistently achieve stronger running engines that will last far longer than the smoke-um, fly them method.  Leaving the cowl off the first few flights in the air will definitely make for a cooler running engine to get it broken in enough that heat is no longer a big issue.  Way too many people are leaning their engines far leaner than they should.  You should not try and achieve maximum RPM by leaning it down too far.  But it should not run rough either from being too rich.  Don't forget to check the nuts and bolts often to make sure they are not loosening up and leaking air, which makes the engine run lean.  Oil is an engines best friend, and over leaning the engine to the point you see gray colored fuel all over the plane near the exhaust means your wearing the metal out of your engine.  It does not hurt to run a little extra oil in the fuel during break in.  This will save your engine.  Engines are expensive, so treat them with the above care and you will see a big difference in the reliability during  your flights.  You do not have to bother using my method, but if you do, you will not be sorry you did.  Hey, in my early years of flying when I was a teenager and probably until my 20's, I smoked my share of engines too, but not anymore since I use the above method, I am very happy.  I read a lot about how touchy the Super Tigre Engines are to tune, but I do not have that problem, no matter which size engine I have bought.  Mine run great since I use my method of breaking them in now.  They last for years of flying too.  For example, I love my Bridi Super Kaos 60, which I have had for about 40 years, and I have only had 3 engines in it, a Super Tigre 61ABC, ST-75, nice little step up, and recently changed that to a ST-90 for unlimited vertical performance.  The heads turn when I yank it straight up after the wheels leave the ground and climb out of sight, :-).  As for gas engines that are 2-cycle, I believe running them rich and keeping the runs short along with the cool down procedure, they break in nice and remain strong throughout their lifetime.  It does not matter if it is Weed Eater, Chainsaw, or any other air cooled engine, the procedure works very well.  Hope this helps those not so experienced in engine breakin and tuning.  

vertical grimmace

My Feedback: (1)

That would be great to see you there. That event is something special. I am building a new Fokker DR1 right now. I try not to fly my DVII too much anymore, but might have it there this year, we shall see.
I would recommend having a 19-8 at least, but like I said, I wanna try an 18-8. I am running the stock muffler though, and am going to also try a Bennett muffler this year. I think the stock muffler kills a lot of power.