It appears to me that a diesel has some desirable characteristics for c/l stunt. Particularly OTS where you get a bonus for diesel. I've been reading the internet for info on how to operate a diesel but these articles seem to be written for R/C or C/L racing where high rpm is desired. Perhaps not what I want for C/L aerobatics: I'd like to try a larger diameter prop at lower rpm and higher torque. Assuming I get the engine running, how do I adjust for best torque for a given prop? How do I know if the engine is under or over compressed? Step by step procedure anyone?
Thanks,
CRH

I know a guy that had a PAW 29 on a profile and that thing ran really good.

If you can adjust it to run on song on the ground you'll find it to be under compressed in the air. When it's set right to fly you can start it up and it will sag off over heat in about 30 seconds depending on variables.

Also, if you use starting fluid for ether your oil will run black under any setting so don't go by oil color unless your ether is pure.

MM

Join the Barton Control Line Forum and ask this question there.

It's based in the UK and plenty of members there use diesel regularly. They're also good blokes.

Hello Charles. There a few big diesels for stunt. I run an MVVS 49 and it gives me excellent runs time after time. Choose your fan. just as if it were a glow! By that I mean trial and error, as most folk do.
You soon get to know the feel of the compression screw, too low and you get a bur, bur noise. Too high and it sounds strained. Just right and the exhaust oil is honey shade, too high and it goes black. Aim to run just very slightly undercomressed.
You need to warm a diesel, so run it before you go into the circle to get it hot.
Use a timed fuel cut off because small variations can have large effects on run time Best to sidemount a diesel for equal running inverted to level. Most diesels give you a constant speed sort of run, without the kick out of the corners that piped run can give.
Finally you are wasting your time running diesel stunt! The US doesn't believe in diesels !

About diesels: If you need help in person, it may be difficult to get. One of the problems is getting diesel fuel at a reasonable price. The problem is that ether is used to make METH, so it's tightly controlled. It's also very flammable, and tends to "go away" pretty quickly. It's said that there's a difference between the fuel components Andrew and his buds use and the stuff we can get. Ours smells terrible. Theirs is not supposed to smell nearly as bad. It may also be difficult to find somebody willing to launch for you. It's embarrassing to go to a walk-in restaurant after flying, because other customers will be holding their noses. The waitress may refuse to serve you. Maybe you can borrow or buy a used one to bench run, buy a pint of fuel and see how that works out for you?  Steve

Aways wondered about using a constant speed engine in a variable pattern as the goal should be having the engine speed vary to suit that pattern so that airspeed is constant.

But a diesel  (or indeed a fourstroke) does seem to 'dig' in or resist change during manevours better than a glow engine.
I put this down to the ability to accelerate after a manevour slow down back to where it was more rapidly than a similar glow .

I was told to use 7" of pitch and the same diameter as an equivalent glow as a good starting point for a prop, so a PAW 40 likes an 11x7 prop as against an Enya SS 40 that could use an 11x4 - the extra pitch  does not result in extra airspeed.

There seems to be a lot of personal preference. Since I'm only a beginner I can only speak to my struggles and what seems to make things easier for me. One of my (many) problems is speed "wind up" in consecutive maneuvers and speed increases on the "down hill" side of maneuvers like the squares. When I do get a 4-2-4 break the airplane seems to keep getting faster and faster in consecutive maneuvers and on the down hill side of wing overs making control inputs too much and too late. I was flying a profile with a PAW 19 and it seemed to me not to have the tendency to speed up. I was using a larger diameter prop same pitch as a glow engine. What I would call a "climb pitch" prop. I have a Brodak Oriental with an OS 25FP that I'm running at a rich 2 stroke (no 4-2-4 break) setting with a low pitch prop to control the speed.  I tried a Saito FA-30 for the same reason.  A lot of the info on the internet is from the R/C guys who want as much speed as possible and have the ability to throttle the engine. They go for as much pitch as they can. I've been trying to use as much prop diameter as I can and use lower pitch to get the lap times down to the 5 sec range. Maybe it's just wishful thinking or maybe I'm  slowly learning the control input timing, but it seems to be working.  It's a bit different direction from what the C/L "4-2-4 break" guys are doing.  So far, my best over all luck is the OS 25FP. It's easier to start. and easier to get consistent performance from flight to flight. It just seemed to me that the high torque, more constant rpm of a diesel turning a large diameter prop would be a good thing: more thrust going up, more resistance to acceleration going down, more constant speed overall.  I can see that there are some pretty significant issues with using a diesel here in the US: getting the proper fuel is one... but it may be worth playing with for OTS since there is a points bonus for diesel. I suspect that many of you experienced folks are chuckling and thinking, "been there, done that, got the T shirt". Don't waste your time and money. You're probably right. But, it's fun to try different things and learning is never a waste of time.

I was flying a profile with a PAW 19 and it seemed to me not to have the tendency to speed up.

You may find this of interest, I have a yet to be used stock standard PAW 40 and a factory tweeked one as well.

Looking down the throat of most standard PAW's you could be forgiven in thinking that the venturi diameter looks asthmatically small and yet the factory tuned stunt version is even tinier!

The advice from the factory is that they have no idea as to the intended use of the engine (could be free flight, control line racing/stunt or whatever) so they are set up to produce reasonable power and restarts.

So, your PAW 19 may work even better with a smaller venturi insert than what comes standard, that and give the higher pitches a try out, say a 9x6.
The model should pull better in the overheads.

Good Luck and Barton is a good place for info!

Now this diesel smell business can be a bit of a myth. if you use paraffin (kerosene), then yes it smells. I now use white spirit from the decorating store. It is a far more consistent product than my local kerosene and it doesn't give rise to the "diesel smell" loathed by US flyers. if you want to be really smart, use scented lamp oil and smell great!

Andrew.

White spirit = Turpentine?

P.S. From that indisputable fountain of knowledge that is Wikipedia -
"Although not normally marketed as a fuel, white spirit can be used as an alternative to kerosene in portable stoves, since it is merely a light grade of kerosene.[citation needed] It cannot be used as an alternative to white gas, which is a much more volatile gasoline-like fuel."

White spirit = Turpentine?

P.S. From that indisputable fountain of knowledge that is Wikipedia -
"Although not normally marketed as a fuel, white spirit can be used as an alternative to kerosene in portable stoves, since it is merely a light grade of kerosene.[citation needed] It cannot be used as an alternative to white gas, which is a much more volatile gasoline-like fuel."

I think mineral spirit is the same as white spirit... and pure Diethyl Ether Anhydrous can be obtained on ebay 500 ml (about 17fl oz) for a mere $40.00. Ouch.

Sorry Steve, I should have been more explicit - Mineral Turpentine which is white spirit, solvent naptha etc.

At least that's what I think today .....

Eric Clifton (Dr. Diesel) has stated that John Deere starting fluid has sufficient ethef to be useful in model diesel fuel.  I have not tried this myself as I have a small stash of ether I acquired from a TR guy.
fred

I use small diesels for some OTS planes because they were designed using diesels.  This group of OTS planes was designed by Ron Prentice in England.  The engines are PAW, Elfin 2.49, Elfin 1.5, and a 020 Elfin reduced from the Elfin 1.8.

With this kind of plane, I don't worry about the diesel goo on the planes, which is hard to remove.

Floyd