By "typical boat anchor with RC timing" do you mean an engine that's timed like the OS LA46*?

I know that 2-stroke "diesel" model engines aren't amenable to the sort of "stunt run" that you get from a glow-methanol-nitro engine.  There's something magic about the combustion chemistry of a glow engine that makes the whole "makes more power going uphill than down" stunt run possible.

So I rather suspect that without electronic aid**, a sparker would have the same issues.  I could be entirely wrong: it may be that rather than a glow engine being magic, a diesel is anti-magic.  Or it may be that with a pipe, a sparker would show the self-regulation you want out of a CL engine.

Someone just needs to try.

* poke, poke.

** I'm thinking active engine regulation, here.  Brett Buck, at least, thinks that this won't work on a glow engine because of the engine's slow throttle response.  I'm not going to argue with him on first principles, although I do have a back-burner project to take some measurements and see what the data says.  If he's right it probably won't work for a sparker, for the same reason.

Tim,
You are very much mistaken when you say that diesel engines are not amenable to a good stunt run. I have an OS 40VF on pipe, which is set up as per book and gives a great style of stunt run that I like very much. I also have an MVVS 49 diesel in a similar plane, guess what? There is very little between them in run performance. I actually prefer the MVVS because it doesn't accelerate out of corners the way the OS 40 VF does.
  There are few people that have gone the diesel route, diesels have always had a bad reputation in the US for stunt and people have simply not bothered with them. They run very well indeed and need a far lighter fuel load than a glow and hence there is less change in CG.
  You can all shoot me down if you wish, but have you tried both? I have and I know which works best for me.

Regards,

Andrew.

I stand corrected.

Andrew H., I've hard that the weight of the ignition and batteries isn't all that much in a modern gasoline engine.  But that's hearsay, not measured fact on my part.

Andrew T., I've had Cox engines with the diesel conversion head and loved them.  But you don't see many diesel engines on this side of the pond.

Hi Tim,
You don't see much in the way of diesels in the US because they got a very bad reputation in the early days (late 40s and early fifties). Randy, I know exactly what you mean about settings, but like everything, it is all a matter of experience. If you had sixty years experience in running diesels then I think you wouldn't have a great deal of trouble in setting them up .It appears that you don't have much trouble setting up glows for exactly the same reason . Smell what smell? I think the perfume of castor is great and you don't have to run kerosene or whatever you call it in the US. There are other basic fuel types that don't smell. I don't know the US terminology for those unfortunately.
  My diesels run more like a pipe than a 4 stroke, but I can see where you are coming from, you can't deny that they have an advantage in a smaller fuel load and hence less CG change and a diesel doesn't have to be heavy, viz the MVVS49 diesel is adapted from the glow engine, for little or no weight penalty.

Regards,

Andrew.
 

Fuel is getting to be more and more expensive

This is a little OT, but the rate of increase of fuel cost seems to be tiny in comparison to, say, gasoline. I was paying about $10/gallon for fuel when I when to my first contest in 1981, and it was the absolute cheapest I could get (home-brew, or back room of Lew McFarland's pharmacy-brew). I just got a new case of semi-custom fuel for a little under $17/gallon. That's almost exactly the inflation since then.   I could get conventional fuel for around $13.50, so I contend if anything, the constant dollar cost of a gallon of fuel is actually lower now.

   Gas was about $1.25/gallon in 1981, and about $4.25 now, way ahead of inflation, and it is definitely less effective than it was in 81.

 Th increase in glow fuel cost is offset further by using it more effectively. I was using about 5 oz/flight to fly an wimpy St46 on 5%, and close to 6 oz on 10% (to compare apples to apples), and a fair bit of it ended up gooped to the bottom of the airplane (increasing paper towel costs astronomically, like 1/2 roll per flying session) I now run about 6.4 oz/flight on the mighty piped 61 and use 3 sheets of paper towels. I could switch to something that was nearly as effective and runs 4.5 oz per flight and takes 1 paper towel per session.

     It is my considering opinion that my per-flight recurring cost of glow is probably less than it was in 1981 in absolute dollars, and could be reduced. Cost per "unit effectiveness" is much better now. Adjusted costs are certainly much lower. 

   Even further OT, since someone was complaining about it in another thread - engine cost. In 1981 I paid about $75 each for bone-stock ST46s (conventional units right off the big production line). Of course you can't just have one of them, because the ring tended to go over the hill at inopportune moments. So, say, carry 2 of them with you, and have the 3rd in reserve. That's $225, not considering the trick RPM or SST muffler (another $20-40) and the big box of props (say, 10 of them at $1 a piece but about an hour of labor reworking them, say at $4.25/hour, so $52 for your box of props). 10 years of an ST could be the same 3 engines, but maybe 25 rings, 5 sets of bearings, 3 dozen props, two head gasket sets, and maybe 5 venturis. Ignore the "fiddling-around-with-it-in-a-hot-field-for-hours-just-to-get-it-to-put-out-enough-power-at-the-right-time" time, that's part of the "fun".


 I can get a RO-Jett for around $400, and that was the about the same at the PA. I went about 5 years at the highest levels with no backup engine when I had the PA, with two pipes and two headers, for a total of about $600 for everything including the two props I actually needed (forget those I got and didn't need) since you can endlessly adjust them. That also is about a wash in absolute dollars and a bargain in constant dollars. And, it works MUCH better.

  For even cheaper, I got an engine/header/pipe from Alan Resinger for $125, and I ran that for about 10 years with no maintenance, with two Bolly fiberglass props I got for about $18 a piece, unfinished. That outright cheaper than trying to compete with ST46s (which, truth be told, I *wasn't* competitive in any way with an ST46).

   I think the cost of the equipment/recurring fuel, parts, etc, cost in stunt has, if anything, gone down since I started doing, and pretty drastically compared to inflation. Even if you ignore the fact that just about all of it is *far better* than we had in 1981. And compared to my personal resources, it has become nearly negligible. I got $440 a week when I hired into Lockheed in 1983, let's just say it's a bit more than 150% of that (roughly the inflation since 1983) now.

        Brett