Hi Guys,

 I'm just looking for a benchmark to start with for my 1st forray into tuned pipe setups for a P.A .61.

 I read the Stunt news article written by Brett and David a while back but embarrassingly can't find it since we moved house.

 I have an r.e version and a muffler to suit but would like to make the model as consistent in windy weather as possible, hence the move to a tuned pipe set up.

 Plans are to fly at the Aussie Nats at Christmas/ new years with this set up so I need to order props and a pipe shortly. The model I'm using is a kit built Strega. Only started construction a few days ago but my best work is always done in chaos.

 Thanks in advance, Rob.

Hi Rob

You can use a 13 x 4.25 2 blade or 12 x 4.3 3 blade with a 17.5 to 18 in pipe length, Launch just as it approaches the fastest 4 cycle it will run on teh ground, or is just beeping 2 cycle on the ground, It will drop to a solid 4 cycle after launch within 1 lap. Start with 5% nitro and go up as needed. If you read the pinned article at the top of this forum it will help your setup

Randy

In a nutshell:
Remember the needle is for setting the fuel mixture, not for setting the plane speed.
The prop pitch is for setting the speed of the airplane.
The prop diameter is for loading the engine properly and getting maximum thrust from the motor.
Nitro is for controlling how much or how little break you have, this is to say how strong the motor will come on in the maneuvers. The other 2 items that work with this are compression and venturie size. This is not all there is to getting perfect engine runs. Many things work in
conjuction with each other to achieving this goal, and most everything I am going to mention affects the others to some degree or another. Please do not think of the following as an oversimplification, it is not. It would take a volume of text to try to explain all the relationships that one item has to another, this is just to try to add a little clarity, and to give you a place to start.
The 8 basics to helping yourself to a better engine setup are:
1. Engine: Pay careful attention to matching the engine to the airframe. Don’t overpower or under power your plane. Make sure your power plant is an acceptable weight for the ship it is in and matches well with it
2. Correct Fuel: Fuel is one of the most important things in tuning an engine. You must make sure that you have the correct oil type and percentage for the engine your using. For example Fox 35s, OS 35s, older McCoy’s and such need high oil content fuels 24 to 29% are common percentages.
Modern ABC and AAC engines will use much lower oil, 18 to 22 % percentages are the norm here. Nitro percentage is also key to getting the best from your power plant, There are so many ways to run stunt engines it is impossible to print anything but guide lines.
I have written many times about fuel. You can get a copy of my Care and Feeding of a Stunt Engine from the PAMPA archives
Typical stunt engines will use 5% nitro in cold weather going to 10 or even 15% in hot months. You can get in trouble using, say 15% in January, this setup would need 25% or more to be the equivalent in August. So unless you really have this working it is best to setup your engine for lower nitro in cold months and higher nitro in hot months. This will help keep the run constant thru out the year. Also it will help control power in your motor.
3. Correct Props: Props are also critical for achieving good engine runs; a prop needs to “load” the motor correctly without over or under loading the motor. It also needs to be the correct size and pitch to pull the airplane. This is an over simplication, but generally the diameter will be what you use to “load” the engine and the pitch will be what you pick to set the plane speed
Some of the things you will run into when over propping an engine are; hard to set the needle on the ground; the engine will unload a lot and go rich in the air; the engine will run hot, or not cycle very rapidly.
When under propping generally you will notice the engine will also not cycle correctly. They at times will just 4 stroke thru everything, sometimes going into a 2 cycle at weird times.
A properly loaded engine will use a prop that if running a 4-2 break, will come onto a 2 stroke a 10 O’clock and back to a 4 at 2 O’clock. There are variations on this; You can have a strong motor just beep 2 stroke at the tops of maneuvers, but you shouldn’t have one that 4 strokes uphill and switches to a 2 stroke on the downhill parts of maneuvers.
4. Needle setting: Don’t try to use the needle to set the speed of the airplane; the needle is for setting the fuel-air ratio that goes into the engine. Typical settings are so the motor will be in a very fast 4 stroke when in level flight. If you set the needle too rich it will delay the engine switching and make the engine come on late in the maneuvers. If you set it too lean, you can sometimes run the risk of too much 2 stroke and going sagging lean in the tops of maneuvers, killing your drive and over heating the engine. Once you get this set, you will have a little leeway in tweeking the needle in or out for conditions.
5. Airspeed: Most all planes like to fly at the airspeed they work best in, even exact or what is supposed to be the exact same design , will a lot of times want to fly at different lap times. Example: I have flown many SV-11s, at the same weight that fly at different speeds. Try to find the optimum speed for the plane your flying. This will depend a lot on the weight of the plane and also the power of the engines
6. Compression: Setting the correct compression for you motor isn’t a simple thing and will vary with nitro and prop size. Try to set the compression so when your engine hits into a 2 stroke it doesn’t come on too hard or too soft. This will work in conjunction with nitro and venturie size. Generally you will use higher compression for low nitro and lower the compression when using higher nitro fuels.
7. Venturi : Venturi size is one of the keys to get a proper switching 4-2, while not coming on too hard or too soft or too late or too early. If you are constantly accelerating too much when your engine cycles you may need to go down on venturi size. If you are not cycling much or have too soft of a break or a late break , you may need to open the venturi up a size or 2. This will work in direct relationship to nitro and compression.
8. Fuel Tanks: A large portion of engine problems I see are really not engine problems. They are fuel delivery problems that many times relate to fuel tanks, Tanks are maybe the most critical component of your power train. Make sure you have a solid mount, and a tank with no leaks or cracks in the tubing, inside or out. When in doubt I suggest trying a new tank, if there is a difference, you may have bad tank. Don’t forget to use a good filter and make sure there are no holes in the fuel tubing. It is also advisable to try to keep the tank as close to the engine as possible
These are just basic suggestion to help you tune your engine, and by no means covers it all. There are literally thousands of engine setups that would take volumes to cover.

Randy Smith

 Thanks Guys,

 That's certainly given me a decent place to start, obviously it will take some time to sort properly but at least I'll be able to mitigate any real bad traits early on.

 Randy, what pipe would you recommend? I only have a muffler setup for this engine so will be in touch shortly. I have a Jett pipe slated for another project that's 14.75" long x 1.5" diameter which will at least allow me to dummy up the pipe tunnel whilst I wait for one to arrive.

 Thanks again for your help, Rob.

Thanks Guys,

 That's certainly given me a decent place to start, obviously it will take some time to sort properly but at least I'll be able to mitigate any real bad traits early on.

 Randy, what pipe would you recommend? I only have a muffler setup for this engine so will be in touch shortly. I have a Jett pipe slated for another project that's 14.75" long x 1.5" diameter which will at least allow me to dummy up the pipe tunnel whilst I wait for one to arrive.

 Thanks again for your help, Rob.

Hi , you can just buy my 61 pipe, I sell them in either aluminum back High Torque, or Carbon back Ultra Quiet, both work the same

Regards
Randy

 Awesome, Thanks guys.

I think I'll opt for the quiet pipe, though noise is not a real problem where I usually fly.

As a matter of fact we are having issues with a neighbour at present so maybe I should be running an open header, straight out.

Thanks for the pics Steve, I'm just starting on the fuse so this gives me the chance to get it right without having to change anything later.

 Randy, I'm on night shift this week so I'll give you a call at an appropriate time. I'd like you to hook me up with a decent (starting point) prop and a 2" 3 blade spinner to suit as well as the pipe.

 Thanks again, Rob.

Dennis

The setup above, is a general setup for ..ANY.. engine , not just a PA, it really is not that complicated. and it does work, take things step by step.
If setting up a PA 61 for example, I have a prop, pitch, pipe lenght, fuel etc setup that works most all over the world. You will have to vary some things like nitro or pitch to make up for variables like plane drag, plane weight, weather altitude. But again , it is not that complicated and will get you very close very fast.

" I was told just use Randy's set up. In a tone that implied "what do you know." Condescension dripping from every sentence. Well. There is Randy's set up."

As far as your complaining here about "someone" who told you the above statement, you need to take that and your hurt feeling up with them, not me and not here, this is not a forum for that, and it adds nothing to the thread and questions asked.

Randy

Dennis

To your point, the setup works for over 90% of people, But we, as most do know some or 1 person who can never make anything work, I know people who cannot make a ST 46, FOX 35, or Electric setup work.
  The article I wrote and the one which part of is posted here, is for general setup of most any stunt engine, When it comes to PA Merlins  Aero Tigers, they are even easier since they will run in many different ways, and my setup for them works very very well for over 98% of people I have sold them to. They work in fact so well with my setup that I have many 100 or 1000s of people who just flip n fly. They work so well that the engines and my setup have won many National Championships all over the world in many countries, Including a large amount here, and have won many World Championships. BUT...there is no engine that someone cannot screw up. For Example I had one pilot take one of my engines in dead 100 plus summer heat and stop up the very poorly flowing tongue muffler, against my advice, and had screaming lean burn down type runs from the very choked off and very hot engine, he had no clue as to why or what was happening. Removing the many screws  he had used to plug up the exhaust made a night and day different run.
I had another pilot who too a PA 61, removed all but an .005 shim from it, drilled out the true venturie to a size that was 8 steps too large (ruining it) and the use a tiny 11.7 inch 2 blade, and ran 15% nitro fuel, his runs were crap, they engine charged and wound up, accelerated going uphill and was terrible, He had no clue that he caused the problems and  argued adamantly his setup should work, When it was returned to stock, it worked well enough to finish very high at the NATs.  I have also changed several peoples setups, at the NATs, under the veranda, in front of many people, and the first test flight was about a 1000& better than what they had, and the before setup was complately unflyable.
So this just goes to show that you cannot get every setup perfect for anyone anywhere.  For example If you are a  person telling other that, say a FP, for example is easy to setup just use the add 1 extra shim, this 10% fuel, and the magic plastic prop and it will work perfect...that is FALSE. it may work somewhere, but it will NEVER work all over the U.S., Too many differant planes, weights, drag coefficient etc...
Thus my article trying to help pilots out with tuning their motors.

Randy

Yes. Right. I agree. What you said about the FP40s applies in our experience to the FP20s and 25s. Usually significant variances  especially so for assembly line engines. Piston fit, other tolerances, even size of venturis, not as close, engine to engine, as carefully hand fit custom builds. Issues with elevation, air pressure, humidity, wind condition. Which is part of the point I was making. There is not one setup that instantly works every time. Wind condition at home field play a part as well. If the wind at your field is weird, hard to predict, blowing one way bellow 45 degrees, another way up top. You will get into the habit of running your engines faster, probably with a different break, than the folks who tend to experience straight air, blowing mild.

Exactly , and I never said there was one setup that will work everywhere..ergo the article I wrote   

Randy

You make great engines. I hope, as many do, that you find the way to make them again.   Yeah. I'm kissing up. But it's an honest opinion.

Hey, I'm harrassing him about making those motors again also. Theres no, if and or buts about it. Randy made the worlds best stunt motors-period.
Lots and and lots of people are harrassing Randy no end LOL.
The problem is that, we are talking about the absolute BEST of something. You just can't make something like that anywhere.