Stuka Stunt Main Forum · 22 of 22 known posts recovered
Jake
Think of it this way. Running a low pich prop at high speed is like running in low gear. For constant air speed.
Robert Storick
AMA 12366
Saint Louis,MO.
Jake
Constant 2-stroke is definitely not "constant speed". A properly running piped or low pitch/high rev system DOES NOT run at a constant speed. Far from it, in fact. Just because it's running in a 2-stroke doesn't mean it's not varying up and down - it's just varying up and down in a 2-stroke. The "phase change" from 4 to 2 and back is not necessary.
The fact is that even running in a constant 2 or a constant 4, but varying speeds, can be FAR TOO effective, far more effective than a 4-2 break motor running perfectly. One of the things I have fought is getting TOO MUCH boost and break from various piped "constant 2-stroke" or "constant 4-stroke" systems.
If you have the engine set up incorrectly, it will indeed do just as you describe. I'm not sure why your's did that - possibly too lean, possibly too much pitch or diameter, or not enough venturi. But that's just a matter of setting it up wrong, I think.
And I might add, on those engine you mention, you very likely won't have much luck with high rev systems. The power falls off too much with RPM at the revs that you need to run. I've tried it with several engines like the ST46, and no chance. Replace that with something like a Magnum 36, same prop, and it's sparkling.
Brett
p.s. I might also note that you note that "some" like it. Truth be told, "some" means "virtually all". 4-2 break motors have been rare in high-end competition for at least 10 years or more. There are multiple reasons for this, but performance, reliability, and availability (ST60 was discontinued something like 20 years ago) are way up there. I flew in both eras - and there's no comparison.
Hmm, I think the Chinese and Russians can be pretty competitive.
Hmm, the Chinese were using Satio 56s, and any resemblence between a Yatsenko or Belko motor and an ST60 is pretty weak indeed.For instance, they run in more-or-less constant 4-stroke.
I'm not trying to ruffle any feathers. People can enjoy whatever they want.
Brett
I was thinking about a classic run, but you're right, there aren't may Fox 35s (or ST 60) being used by top competitors now. Some, but not much.
You can run 4-2-4 or 2-2-2 or just plain 4 with the modern pipe engines just vary the nitro content and get just about what you are looking for. I used to do 4-2-4 with my piped PA .51 powered Intrepid. with a PA .61 or RO Jett 61-77 you can use enough nitro to run in a full four stroke all the time. Doung Moon favors that type run and has had great success runing his engine that way.
Jim Pollock 
Jake
I would probably start with something having a little more background of success. The 40FP, in particular, is notoriously evil to the point of manageing to sustain an entire industry of reworking.
I suggest a 40 or 46VF. I can pretty well guarantee that can be made to work.
Brett
This summer I had a chance to fly a VF-40 powered ship that belonged to a friend and lets just say that it was a real eye opener.
The VF was easy to start, had gobs of usable horsepower, and flew the plane at a reasonable speed with great tension everywhere.
It also, because of the available power, pulled clean corners with great off-corner drive. I mean it just turned the corner without drama and kept going. The flat prop and the pipe also helped control the speed on downsides and really cleaned things up.
I know that my description makes it sound as if the pipe plane is some kind of Magic Bullet, it isnt, but it is MUCH BETTER in most ways, than what has gone before.
Once you add in the fact that the pipe engines can be so easily tuned for power output and run characteristics, there is simply no comparison.
As far as price goes, the pipe stuff IS more expensive but you won't be doing nearly as much maintainance so you won't need as many engines. (Remember, most of us Tigre fans own them in multiples of 3, into the teens. Meanwhile, most pipe guys just buy a new one when they NEED one! LOL!!!)
While I havn't sold off all of my Super Tigres, I am looking for a good deal on another 40-VF for next years planes. I'm going to build one Buso Jaguar, as designed, with an ST-46 and one with a 40-VF.
This should be interesting!
BIGS
Also an engine out of production, but can still be had. And run very well.
If I were to try again maybe my nobler might be my best bet to re-power with a magnum 36. Is that a good choice since they are not hard to get, or priced so high?
Jake
When the character of a man is not clear to you, look at his friends.
Japanese Proverb
The superiority of a tuned pipe run comes to the surface in high heat and wind.
Yes, the ST .60 type is a wonderful and easy to set-up piece, and certainly capable of making the Open cut for a Friday flight....Bob Baron won Open and the Walker Cup within the last decade using one. Windy used an ST for a series of fifth placings, too....but I believe that these were more the result of exceptional flying rather than "motor run".....
See Ya
Peabody
The Old OS engine line all have the dreaded Boost ports cut into the engines. These are the single most deterents to a 4-2-4 run. Why?, Beacuse they were engineered to be flown R/C, higher speed more RPM. this port will chanel more fuel to the combustion chamber at higher RPM's, thus the dreaded run away during control line use.
Jake the new OS line of engines will suit you better, they have no boost ports to fool with which make them a good stunter right out of the box, 4-2-4 break and all. The new OS LA 40 & 46 are outstanding engines without any up grades. However there area few guys that do offer tune ups & blue printing for these engines, if you want it.
I do not know what ability or what class flyer you are so for right now stay away from the piped ships unless there are a lot of good upper class flyers, in your area that can help you get started. You'll know when it is time to make the jump to Hyper Space and I do mean Hyper Space.
I have been flying on and off for 8 years and I believe after the new year, I will purchase my first PA61. I have been told that the rear exhaust can be fitted with a muffler. I want a great competition engine for my new ship but do not want to give up on my 4-2-4 run.
Mike Clark
"Chance Favors The More Prepaired Person."
I've seen the OS-LA 40 & 46 engines run and work with them. I have lots of better 2-4 braking engines. I may trade or sell some of my super tigre 60's and 46's, or some others I have, and try to get an OS 40 VF or a 46 VF for a new plane.
Phil C
Hi Phil,
Not much was made of it when Juri Sirotkin won the Worlds in '64 using a MVVS (in '62 he ran it on bladder), in a 2 stroke and a 10-4 prop on his Spacehound. That was 40 years ago. Nothing is ever new is it?
Bill <><
When the character of a man is not clear to you, look at his friends.
Japanese Proverb
Goes back much further than that - Wild Bill talked about lowering the pitch, for pretty much the same reasons, back in the 50's. The problem was always getting enough control at higher revs.
Brett
Jimmy Jacobs
Maybe an old dog can learn new tricks with all this help!