This isn't really about racing, but I figure that if anyone knows the answer it should be you guys.

For the Ringmaster Fly-A-Thon I had the notion that I'd just put in as many consecutive flights as I could manage with one guy on the handle: short-tank, start, fly, shag the plane, repeat.  But with an FP-20, it turned into: short-tank, start, fly, shag the plane, go shoot the breeze with the RC guys until the engine cooled enough to start, repeat.  Instead of my imagined "lots" of flights, I think I managed about six in the two or three hours I had available.  I'd like to do better next year.

I have, in my collection, an FP-20, a couple of LA-25's, and a couple of old OS 25Ss.  They all bolt onto my Ringmaster, and I've got at least one good engine of each type.

Which one would be best for my imagined flight scenario, and what should I be doing with fuel, plug, battery, whatever, to make sure that restarts are as quick and as sure as can be managed, and that I don't damage anything?

TIA.

A racing trick for starting hot engines is to pour some water on them to cool them off quickly. Seems like it shouldn't be getting that hot, though. What prop are you using?

Tim, i too have an FP-20 on a flite streak that lacks a lot of compression, runs great when started, but is hard to start and really hard to restart hot. I would suggest the la 25, slow combat fliers restart them hot quite easily!

Tim here is a "tip" I have used many times hen I was able to race.  Get a clean rag, saturate it wiuth alcohol while the plane is in the air.  Catch the plane with the rag in your hand, covering the motor with the rag.  Then remove it fuel up and in most cases you will find the engine cool enought for a re-start at once.
Joe

In all honesty here, if you REALLY want hot restarts why not try a Davis Diesel conversion head for the LA 25 or if you simply must stick with the glow what about one of those clamp on heli cooling rings for the head?

If the LA won't start hot as a glow then it's not going to start any better hot as a diesel.

The crucial variable is piston and liner fit.

 

Yes, it's using a muffler.  And, it'd be for flying in a state park that's pretty sensitive to noise issues.  The club works hard to stay on their good side, so the muffler needs to stay on.

Thanks for thinking of that issue -- I'm not sure if I can find a way around it, but it's certainly something I'll need to keep in mind when I weigh folks' answers and try things out.

I myself don't think the LA's will take the punishment of be dieselized. 

Ah, yeah they will.

If the LA won't start hot as a glow then it's not going to start any better hot as a diesel.

The crucial variable is piston and liner fit.

 

Yep, and the mechanical reason is that the use of kerosene as a fuel base as compared to methanol will result in far less latent heat loss from evaporation effecting the piston's fit.
(The piston shrinks rapidly and well before the liner when presented with a rich fuel charge upon restart.)

I would still put my money on a diesel starting better after a run than a glow - all other things being equal.

If that did happen wouldn't the outside of the liner be cooled first by the fresh charge before the piston, thus shrinking it onto the latter?

Isn't the Ether even easier to evaporate than the methanol? What role would it's latent heat of vapourization play in cooling the p/l in a diesel?

The ether content is what - 33% at most and the diesel stoichiometric ratio is about half of what a glow is so while ether may be the better choice the amount available for the task is far, far less.

Are you confusing heat and temperature?

No, are you? I mean, what a question, for this application they are the same thing.

Wouldn't the loss of heat be insignificant c/w the overall heat energy of a warmed up engine?

No, the incoming charge will hit the inverted cup of the pistons cavity long before it hits the liner and further the piston eclipses the liner totally on part of its stroke thus blanketing any effect.
Plus the liner has the benefit of being cooled by the outside world, the piston has no such luxury.

Why don't you bring your LA 25 with DDD diesel head out sometime to Whalan and we'll see how long it lasts on an APC 7 x 7, it's a normal racing prop for 25 class engines..

So many questions!

 

Don't have one mate and even if I did racing bores me.

The ether content is what - 33% at most and the diesel stoichiometric ratio is about half of what a glow is so while ether may be the better choice the amount available for the task is far, far less.
No, are you? I mean, what a question, for this application they are the same thing.

No, the incoming charge will hit the inverted cup of the pistons cavity long before it hits the liner and further the piston eclipses the liner totally on part of its stroke thus blanketing any effect.
Plus the liner has the benefit of being cooled by the outside world, the piston has no such luxury.

Don't have one mate and even if I did racing bores me.

For heavens sake Chris get a life!

This is just BS and nonsense with no connection to reality.