You might check with Al Rabe. I sold him a pair of ST G21 .51s back in the early '70s; he needed more grunt for the early Bearcat, and may still have them. Not a common engine; I really don't know how many were made, but they'd swing a 12-5 with ease.

Thanks Ralph but was looking for something more modern that I can get parts for. Heard Tom Dixon is importing a Double Star 50 or 51 that fits the bill but also heard it wasn't as powerfull as one would think it should be.. This is all rumor, anyone have any straight dope on the Double star?

What about the PA's or RO jets? Not that i can afford one but one can always dream..

Hi Bob,

The Double Star 50 is a direct swap for the ST 46.  I had a head strip out at Huntersville several years ago and bolted one of Tom's engines in my plane as a loaner.  It was pretty much identical in run characteistics.  I know that if more power would have been needed, a larger venturi and/or nitro would have done the job.  Stock it doesn't have any more (if as much) grunt, but the venturi is small.

Bill <><

Tom has a new DS .54
I'll be it's good.

On his Stiletto, Dan Banjock went from an ST .46 (very good) to a Double Star .51 (very disappointing) to an ENYA .46 4-stroke (phenomenal).

I mentioned the LA .46 because I have seen them haul some rather large airplanes with considerably authority.

Selling a used ST .46 on eBay will probably earn you enough to buy two LA .46s.

Also, the absolute best running LAs I've seen were completely stock.

Bob Z.

Bill Little is correct that the DS-50 is a drop in replacement for the ST-46.  In stock trim it might be down on power to the ST-46, albeit it will also use much less fuel.  I have found, as Bill will laughingly attest to, that if find your self down on power or the engine running hot, the DSs will respond well to a larger venturi.  I have a DS-40 on a Nobler that ran great, but had a tendency to go hot and slip into a two stroke during the square 8 and stay there.  Switching the original .275 venturi with a .314 supplied by Jim Svitko (who had already sorted out the same problem on his plane), I found that I could drop nitro back from 10% to 5%, have more power, still minimal windup even on a very windy day, and not have the slightest issue with the motor going over the hill hot.  4 oz of fuel gives me a 6:10 run at sea level, compared to 7:40 in stock trim.

One caveat is that, if you open the venturi up, open the exhaust as well.  This applies to pretty much all muffled motors, whether a DS, OS or Big Jim Greenaway ST.  On my DS, I (as suggested by Tom Dixon) drilled out all the holes on my tongue muffler to 1/8" diameter.

The DS-54 is most likely more powerful than the 50, and comes with a number of venturis when you get it, but I'm not sure the bolt pattern or dimensions match up with the ST-46.  Somebody else here probably has the info on that.

Steve

PS, Ron, we talked at length before about the DS/Nobler issues.  The venturi fixed it, Gorilla power with no overheat!!!!

One thing I have found with all the Double Star engines, in "STOCK TRIM" is that they are set up for FAI (no nitro) fuel, and they have itty bitty venturis for gas milage.  Open up the venturi, add a couple shims and go with 5% to !0% nitro and you will be surprised with the power and run they give.

I admit, I do not know anything about the "new" DS .54 or .40BB.

The .40 and .50 will be real decent stunt engines when they are allowed to breathe, and some nitro is used.  They will do the 4-2 excellently.

Bill <><

Another point......... even though the LA .46 is a nice engine for stunt use, I have not seen one as strong as the ST .46 or ST G.51.  They are good for what they are, but not comparable to a really good stunt engine.

   That sure isn't consistent with my experience and/or observation.   A *35FP* is comparable in in-flight performance to a very good ST46. I know, I had one of the best ST46's on the West Coast, and I flew it back to back in the same airplane. It wasn't a blowout, but it was at least even.  The FP flew the airplane  better with props tailored to the engine (11-12"  -  4-5") but  it would even give the ST a run for the money using some of the smaller ST props (11-5.5/6 or so). This was back in the mid-late 80's.

    The 46LA will swing the same props I used on the 35 (11.5-4.5 and 12-4.5 Rev-up) 1000 rpm faster if need be. I haven't done the LA  back to back with the ST46 but if A=B and C>B then  C>A.

     If you are trying run 13-5/6 Rev-Ups, then, maybe you have a point, the ST will probably out-turn the LA at 7300 ground rpm, and the LA will run away (i.e. produce more power) in the air.  But try them with 12.25-3.75 APC and watch that ST46 melt down trying to get to 11000 rpm. It will do it but it won't be happy, and it will be absolutely dead in the air. It takes A LOT more ponies to spin a 12.25-3.75 at the speed it needs to go than it does to spin a 12-5.5 Rev-Up at the speed it needs (8300 or so).

    In fairness, I *HAVE* seen some LA46's that wouldn't come close to the ST46, but these have been "reworked for stunt run", i.e. ruined, by overzealous aftermarket reworkers.

    I liked the ST46, won lots of hardware with the ST46, and was one of the last of the holdouts with the ST46. But let's not get crazy with nostalgia!

    I would agree with the topic on the ST51, at least the older versions, when modified (T&L, etc) and with a tongue muffler. It's stronger than the LA. A good one was about a match for the ST60.

    Brett

I can comment a bit about the LA-46 stuff, but ST-46s are before my time and I have barely even seen any fly, except for Bill's that did indeed melt down when it tried to turn 11,000 (!)

I would classify the LA as *pretty* good up to airplanes in the approx 50 ounce range, based on my experiences with them.  I ran my "good LA" for 250 flights in a 50 ounce Time machine 50 running the APC 12.25x3.75 cut down to 11.75", then later a Gator 10.75x3.75 three blade and Bolly 11x4 N three blade.  The engine was pretty good in that it "homed" on the RPM it like to run at (about 10350 ground launch) in the air and was pretty repeatable.  %5 Nitro in the winter and 10% in summer, no big deal.  I would characterize the overall performance of the plane as pretty good, and the plane scored three or four Advanced victories and a number of podium finishes.

This past summer when I put the same engine in the Avanti 50 (thicker wing, 600sq vs 580, 54 ounces ), I noticed I couldn't seem to prop it with anything that made it happy.  Virtually every prop I tried (APC 12.25x3.75, Bolly 11x4 3bld, Gator 10.75x3.75 3bld, APC 11x5, APC 11.5x4, Rev-up 12x5), and on fuel up to 15% nitro, launching at 11,400 RPM,  the engine seemed to "home" to the same (lower) RPM it liked to run on the other airplane,- which was not the direction I needed the power to go,  seemed to fade fractionally later in the tank, lacked vertical drive in the power maneuvers, had to be flown quick, 4.7 to 5.0 laps to have enough energy for stuff like the square 8, and had considerable windup in even a moderate breeze, and absolutely no braking on the backsides of maneuvers.  Adding pitch (like the 11x5 or 12x5), made it take off like a rocket every time a puff of wind got it, but seemed to give minimal help for the vertical punch or drive.  Maneuvers like the overhead 8 or clover could be a chore, and trimming the plane completely was difficult when chasing power.  The one thing I didn't do, and should have, was go much bigger on the venturi then the .285 already in it.  The plane was lost and the motor killed before I got around to it.
  The guys around here talk about flying 55-58 ounce airplanes on the ST-46; from my point of view, I wouldn't try that around here with an LA unless I put a big venturi on it and a pretty open exhaust system.  But even then, the lack of brake on the backsides would still be annoying.  If I had to do the project again, with an inexpensive motor, I would go the ST-51 route.  I've seen alot of those fly, and at least in these parts they seem to give a better stunt run, and can easily fly a bigger plane than the LA.  In stock format the LAs  run great on smaller, lighter planes, you see mobs of profile Cardinals, etc with the motors.  But my experience leads me to conclude 50+ ounces and thick wings might require some development to get the right kind of output you need....

Steve

Bill the answer is very simple get the replacement ABC piston and liner for the ST/46.They need no break in and you can run them fast or slow. They use less fuel and start one flip. 4.5 ounces to do the pattern.They can be set up to produce more power than a stock motor if you need it. Brian in Australia sold me the first two he had.He sells a low compression head but you can run the stock head and get power like a ST/51 from it. Cost me $75 for a set.
Ed Ruane

Bill I didn't mean to address that to just you I should have said anyone needing a replacement for the old and worn out ST/46. A ST/.51 can be forced into ST/.46 holes but the shaft is 3/8 inch longer. The nice thing about the ABC version is the motor runs the same everyflight which the ringed version didn't. Also less vibration.
Ed

Hi Brett,

Thanks for your input.  Maybe I didn't use the right terminology when I included the ST .46.

As to your point on the ST G.51, my experiences with that one (maybe the engine I have really flown the most contest flights with) are all T&L .51s and I have not seen an LA .46 even come close to the same performance.

     Oh, definitely not. the St46 and the 51, particularly very  lightly modded ST51, are in two different time zones as far as performance goes. The LA doesn't come close, either.

    My point of (mild) contention was the 46LA vs. ST46.  We could only dream of 46LA levels of performance and consistency back in those days. Not to say that its some great powerhouse, or, for that matter, a super-good stunt motor. But it is significantly more powerful than the average ST46 and more than a match for really good STs.

Your FP20 tune up impressed me more than the LA 46 or LA 40.  I know it will not fly as big an airplane, of course, but the run was much better.  Ask Steve Fitton if he liked the power delivery of a good LA .46 in his late Avanti 50.  A plane that should have been "just right" for this engine.

     I don't know what an Avanti 50 is so I would hesitate to comment.

     Of course, the 20FP has a much better run quality than the LA46. The run quality of the 20FP is just about as good as any other stunt motor currently available, at least for my money. Assuming the other stunt motor you are comparing it to is properly set up. The REAL beauty of the 20FP is there *is* nothing to set up, and anyone can get the same run even if they don't have the experience to  know what they want.

     Brett

Good morning, have been in Memphis just now managed to get back to this thread..

First, I have a few ST 46's, two with Ausi Plasma P&L and three with fresh Bowman rings. Have found the Plasma version to be noticeably stronger than the ringed version but a little harder to tame.

 The airplane in question is a Skylark 46 (614 sq in) that weighs 54 ounces. Either version of the ST 46 will fly it just fine, if I were content with a good "Classic" performance package I would stay with one of the plasma engines and just fly it.. Problem is I have experienced the difference between "Classic" and "Modern power and guess one could say I am spoiled. Almost wished I had built the smaller version of the Skylark paying special attention to keep the weight down but stayed with a ST 46 for power.

If I could cram a ST 51 in the nose of the Skylark I would do it in a heart beat but sadly it won't fit without extensive modifications which I don't care to do. I have an LA 46 but don't feel this would be any improvement over a plasma ST. The PA 40 might be an option... food for thought.

Thanks for the info gang, will probably just stay with a plasma St and plan the next classic ship around a modern power package.

Robert, what is the wing area and weight of your Ares?

I have seen LA46s and FP40s pull Cardinals, a Gieseke Nobler, P40s and other planes to winning and high place finishes at Brodak and local East Coast meets in Advanced PAMPA and Expert Profile. These engines, with a minimum set up, are powerful, reliable and repeatable. Practise, familiarization with the run characteristics of a given engine/plane combination, matter most. IMHO.

Robert, what is the wing area and weight of your Ares?

I do not know the area? but it weighs 40 oz..

I do not know the area? but it weighs 40 oz..

If I remember the Ares isn't much larger than a Nobler with a fairly thin airfoil.. Different ball game compaired to a 50+ ounce Skylark 46. Looking like the only choice I might have is the Double Star or just stick with a plasma ST 46 and pump up the nitro..

Tom Martin from our club loaned me a new ST 51 so I could do a little look see.. It will go but is going to require a little grinding.

Front mount holes to prop drive washer are the same, looks like if I use a sprinkler venturi the needle will be fairly close and the exhaust stack looks to fall withen reason. Bottom of the case is wider even though the mounting holes are the same width. Will have to drill another set of mounting holes in the engine lugs for the rear bolts, stock holes are too far back. 51 is almost exactly 2 ounces heaver than a 46, can save about 3/4 ounce by changing the muffler and don't feel the extra nose weight will be a problem.

Will need to grind a little off the inside of the motor mounts and aluminum pads so the case will drop in. I built the crutch with cross pieces of MM stock and one is too close to the rear, in order for the engine to fit I will need to cut back into the cross piece about 1/4 inch, although I don't feel this will be a big problem. Of course I will have to cut the head opening in the cowl large enough for that big ugly square head but again, don't think that will be a big problem.

Now all I have to do is conger up the nerve to start cutting on the airplane Good thing is other than the cowl I won't have to do any refinishing on the outside.

Hi Bill,

Was hoping someone with DS 54 experience would jump in. What was it they use to say "no substitute for cubic inches" or something along those lines..

Problem is I have to go with my gut and it's telling me no one has ever raved about the Double Stars ability to produce power, unlike Randy's 40 or ST 51's flying airplanes that have been flown with Good ST 60's.

Not trying to be controversial just trying to show where I'm comming from... I have several GOOD ST 46's so someone saying this or that engine is a tad better than a good ST 46 doesn't excite me a whole lot. I have seen first hand a ST 51 in a 70 ounce Magnum and it wasn't having any trouble, thinking a ST 51 in a 56 ounce airplane should be a killer.. I hope...

Problem is I have to go with my gut and it's telling me no one has ever raved about the Double Stars ability to produce power, unlike Randy's 40 or ST 51's flying airplanes that have been flown with Good ST 60's.

Bob,

Ouch, that hurts. I consider the Double Stars to be incredible workhorses - when set up properly.

You can set up the 54 so it has a "tad" more power than the ST 46, or you can use another of the FIVE venturis they give you to dial up the grunt close to any older 60. There is an awful lot of "wiggle" room available with any of the DS engines.

Steve Fitton and I had some overheating issues with the DS 40 stuffed into tight Nobler cowls. This was corrected by opening the venturi (and the muffler) and letting the engine breathe better.

My DS 50 was also choked down too much with the stock venturi and I had to open it up.

The DS 54 has cured the stock problem with a multitude of venturis and plenty of head shims. This should allow anyone to dial the engine to their liking.

It's been mentioned on this thread several times, but bears repeating: the Double Stars are made to run with FAI fuel. In order for them to perform properly with our "standard" U.S. nitro fuel, we have to lower the compression and open up the air passages. The engine's combustion timing is fine for CLPA.

The DS 54 is just slightly larger than the LA 46. It's drilled the same as the ST 46, but is 1/8" longer and the cylinder is slightly larger.

I've seen Randy's reworked ST 51 run and consider the DS 54 to be just as good. I just haven't had the time to build that Shark 45 I was planning to fly it in. Maybe this winter. 

Take care,

Ron

Hi Bob,

I have been fortunate enough to find good USED engines a lot of times.  2 DS 40s are in particular.  With a good venturi and the correct head shims the DS 40 becomes a great 40 size Classic stunt engine. 

As to the ST 51, Super Tigre has always made high quality engines, and even though they are currently assembled in China, they are still great.  IMHO, I would rather have a T&L St 51 or an Aero Products ST 51 than any other engine in that category, and I have seen the "great" set ups run at our meets. 

Of course, none will touch a PA 51, but it's a whole different animal!

Bill <><