Engine/lines for Top Flight "Score"

[donchandler]

 :Took  flights on 4 different airplanes today. One was my Top Flight Score. I have a ST. 51 in it and have been using a Zinger 13/5 on it. But with  the 13/5 the engine never really seemed to run like it needed to, that is it always seemed like it was working hard but not really getting anywhere. I'm on .018 lines at 65 ft. Soooo, not really knowing what to do I put a 12/6 on it and put up a flight. The engine started easy and defiantly  was not working hard. Taking off at 8500 rpm on my tach the airplane flew fine but pulled like crazy and a little fast.

I've seen on blogs etc. where guys are flying this plane on a .46 and even .40's.

I'm interested in some feed back as to what different engines, props and line lengths you have been using and to what degree of success.
Thanks, Don Chandler

[Dan McEntee]

   I have been using the ST.51 since 1994 in a Shark 45, Tom Dixon "Charner" (modified from his Charisma) and a SIG Magnum that weighed 72 ounces. Out of all the props that I have tried over that time, I have liked the APC 12.25/3.75 the best and got the most consistent and repeatable performance from that prop. Depending on the model size and weight, take off RPM is any where from 9800 to 10,000/10,200 range. I also use tube type mufflers, GlowDevil R/C long plugs, and SIG Champion 10% fuel mixed 50/50 with SIG All Castor 10%. This combination was the first that I experienced that worked well in the wind to reduce wind up also. If you need to try an off the shelf three blade prop, try the Master Airscrew 12/6. I went to that one my second Shark 45 to have clearance for a set of shorter landing gear, and clipped it down to 11". I experimented wit re-pitching it, but in the end, the stock prop left alone and cut down gave me a run and performance similar to the APC 12.25/3.75. Line lengths on all models were in the 65 to 68 ft range from handle to fuse center line. I have a Score with a Saito .56 in it, and from what I have observed so far from flying that model, the ST.51 should do well in that air frame also, with similar set ups. Your mileage may vary, but give this a try and see how you like it.
   Type at you later,
   Dan McEntee
  Florissant, MO

[peabody]

What Dan says....the ST 51 (square head) likes to spin up....

There is also a ST 51 that lives in a ST 60/56 case, that would NOT be so happy with the APC...
Have fun

[donchandler]

OK-Then what about fuel? Sounds like the .51 is a popular choice. I have been using Sig 5%-1/2 and 1/2. Cool here in North Calif right now so low nitro working well. For some reason this engine just seems like it needs a kick though, I haven't gone up in nitro mainly because I've been listening to advice.

[Balsa Butcher]

Hi Don, feels doggy in the verticals?, Nitro is the answer.  Go up to 10%. In the heat of the Red Bluff summer you may want to switch to 15%. Others have it right, the ST-51 will not be happy at that low of an RPM, it is not the torquer that the ST-60 is. My current set-up is an RSM 12x5.5 prop, launch rpm 9,200'. Engine runs a nice 4x2 break. I have used other props as well. With an Eather 3 blade CF engine was happy at 10,200 rpm launch, held a solid 4 cycle. set-up. These are good engines but they seem to take more "fiddlin'" than some to get right. 

[Dan McEntee]

OK-Then what about fuel? Sounds like the .51 is a popular choice. I have been using Sig 5%-1/2 and 1/2. Cool here in North Calif right now so low nitro working well. For some reason this engine just seems like it needs a kick though, I haven't gone up in nitro mainly because I've been listening to advice.

     In your original post, you didn't mention what brand of 12/6 prop. The only 12/6 prop I liked at all was the B,Y,&O. I used those and their 12/5 for quite a while . I never had much use for Zingers, and I'm surprised that you had any success with the 13/5. Just too much prop. For fuel, I use SIG 10% Champion like I mentioned in my first response. I mix it 50/50 with SIG Champion All Castor to have a higher castor content. The synthetic Klotz that they use is one of the best in my opinion, and having some on that in the mix helps keep rings free and keeps varnish build up down. On the ST.51 I had in my first Shark 45, I'll bet I had some where over 1000 flights on that model, and it's still on it's original ring. I add a head shim or two on my engines also, and all but one that I have currently in airplanes are stock out of the box, with the one in the Charmer being a Tom Lay rework. If you would like to try the rework route,  I would recommend Tom Lay to any one.
    It's starting to thaw out here in the St. Louis area, and all this engine talk is making me itchy to do some serious flyin'!!!!! Might try to get out this week one day before work, now that the circles at Buder Park don't resemble ice skating rinks any more!
   Type at you later,
    Dan McEntee

[PerttiMe]

It is a bit fast and the engine would like to run at higher RPM? Less prop pitch?

[Andy Whitam]

I am building one now and have a fox .51 to put in..what prop and lines do I use. I am sort of new to this. I have purchased 70 ft lines. Are these to long?

[donchandler]

Thanks Dan and Pete. I'll go up to 10% and see. Pete your right about the Red Bluff summers, I have been using 15% in the .35 to 46's. This size of stunt plane and engine is a little new to me, definitely not my scale and carrier stuff.

Perfect weather yesterday, wind and rain today so I'll get out there in a few days and try the higher nitro and play with a prop or two. Yes, sluggish in verticals.

[Bill Heher]

I flew mine 1st with an LA .46- flew OK but even I could tell it neded more ooomph. Also controls were funky, tighter outside turns than inside- culprit was the chesy stock elevator push rod. replaced it with a carbon fibre tube / ball link assy from CLC.

Big improvement- solid control no more "oh crap- almost didn't pull out" stuff anymore. Then I put a ST  G .56 , big difference- plenty of power- no sag / slow down on the veritcals and good tension overhead. Using .018 by 60' eyelet to eyelet. The .56 is kinda thirsty- I get the beginner pattern + maybe another minute- but it is running a real rich 2 cycle and never really leans out, just chugs along. More time / prop changes may get the run time up to finis the whole pattern.

[Bill Little]

Hi Don,

I have never tried Dan's 12.25X3.75 APC, but he has been talking about that set up for a long time, and it really must work well!

I use a Rev Up  (Govt. Surplus) 12-5, (usually around 4 1/2-4 3/4 pitch on the Prather gauge) and a 12" Bolly 3 blade cut to 11 1/2" and pitched around 4 1/2.  With 63'-64' eye to eye ,018 lines.  Generally getting about 5.3-5.4 lap times.

The ST G.51 (square head) does like to turn more rpm than the old light case ST V.60, and it's variants.  Not as much torque as the older ST's either, but good HP.  The G.51 seems to run best from 9500-10,000.  I run it closer to 9500 and it is a great "high rpm" 4-2 engine like that.  I have used them in competition in a 64 oz. SV 11, and a 54 oz. USA-1.  Neither plane suffered from a want of "power".

I think much of the problem when the engine first came out is that a lot of guys tried to run them like the old light case V.60.  It doesn't work well that way from all I have seen.  Plus, the "pipe" craze hit about the same time as the G.51 came out, so it never really caught on with the National level pilots.  I did talk with Henk De Jong at the 2004 World's about his G.51 in his "Pearl".  Sweet combination!

Ol' Dan has done well with his, so that set up is one I would try if I didn't already "know" how mine works. LOL!!

Big Bear