ST .46

Leonard Neumann

>Who among our community of engine
>builders has a special talent
>for stunt tuning the Super
>Tigre G21/46? I just
>aquired one of these NIB.
> It looks clean and
>feels good, but after 30
>years of laying around, I'd
>feel better if someone knowledgeable
>has a look. Thanks
>in advance for your help.

I highly discourage anyone modifying an ST46. As long as the ring is in good shape (and 30 year old rings are the ones everybody used to seek) it will work just fine as is. If you want a modified motor, trade/sell the ST to purchase a different motor.

My recommendation is to oil it up with air tool oil, run it for 45 minutes-hour with a 10-6 prop for break-in, then go fly it. It's one of the best classic 4-2 break motors ever, straight out of the box. The only ones I saw run poorly had been modified or had a worn-out ring.

pma
Here is one time I am not going to agree with those who said leave the ST/46 stock. About two years ago Tom Morris ran an article in Stunt News on reworking the ST/46 that I had written around 1989-90. I had done a lot of research and testing in the late 80's and talked with Tom Dixon ,Big Jim, GMA and Gean Martine. Tom starter this all around 1984 when he told me how rework the FOX 40's
At the 88 NATS I met Brian Eather and he noticed that I had very shallow cooling fins on the head and he told me he had all the cooling fins removed from his ST/60s. I have built several motors with no fins to get the weight down and they ran fine. I live in Florida and I don't have cooling problems with my ST?46's.
The one mod I would do on all 46's is take the head fins down to 3/32 and as long as you are reworking the head you might as well make it a hemi. The ST46 and some ST/60 run to COLD . Some people put the ST/60 on the inboard side on profiles to try and get rid a stumble at low RPM with big props. I believe that removing fins would have taken care of the problem. I think it was Frank William's that started that trend.
In 1987 at a stunt clinic put on by Tom Dixon in Atlanta ,Big Art & Archie were there and Art kept telling me how well my ST/60 ran. Later in the day I showed him that is was a 46 and he could not believe that a 46 could pull such a large plane so well. 720 sq in. thick foam wing and it was heavy at 63 oz. A stock 46 will run fine but it cane be made better. When I wrote the article I continued to rework the46's up till 1993. I no longer do motor work for others. When Tom ran the reprint article I got a huge number of e/mail's about reworking all types of motors. So please don't e/mail me about the 46's. If you have any questions after reading the article put them here and I will try and answer them here for all to see.
I am sure this will raise a great deal controversy but that's how we all learn new things.

Are you comming to ATL in Nov.? If so I would like to know how and what you do to make the heads into Hemi's. The only experience I have had with a hemi head was with the one on the FP .40 I was flying on my Cream Gold and Metallic Turquoise Cavalier at Huntersville in Oct 97. That engine quite after doing a hard inside square, then acted like it was going to start again, and when it didn't I was too high nose up vertically to recover the airplane. Needless to say that made me very dubious about making anything else into a hemi! If you will be there I will bring my ST .46 with me so that you can demonstrate what's proper to me.

Thanks,

Hi Jim
The article on the " HOW TO REWORK YOUR ST/46 " was in the
July/August 1998 Stunt News page 89.There are pictures showing the sleeve and the head rework.I had to build a very powerfull engine for my USA/1.I flew this plane at Huntersville one year ago with a stock engine and it was underpowered.I came home and rebuilt the spar as it was to weak My Fault and got out one of my old reworked motors and it pulled tha plane with ease. I didn't use the Hemi head I came up with a better head for use with the lowered sleeve when one is looking for max power.The only stunt plane I have crashed in over ten years was the USA/1 with that great motor at Jacksonville this spring.The crash broke the motor case in half. Bad fuel and I had a flame out up wind.I am going to try and get to Huntersville this month but Atlanta is a maybe,If I can get the time off.