Just curious but what engine would you use on a Tomahawk?
I would use something like a McCoy 19, OS 20or 25S (old baffle piston version), a 15FP, or something similar.
The 25LA is a stellar stunt engine but in general (running correctly) it needs to be on a larger airplane, like a Skyray 35, Flite Streak, Banshee, and airplanes like that, up to about a Nobler. And not the "Junior" versions, the regular full-size airplanes.
Part of your frustration is that the manufacturers are still listing airplane like the Tomahawk for "19-35 engines", which is what it was designed for - 60 years ago! The difference between a "19" in 1956 and a "20" in 2016 is massive, and there is absolutely no distinction made between a McCoy or OS 19 Pet and a Picco 21, or to a lesser extent, a 20FP. Even a cheapie RC sport engine like a 25FP or the "new" 25LA is plenty of power to replace a Fox or McCoy35 with a massive improvement in performance in almost all the old "35-sized" airplanes from the 50's. So, what it amounts to is that you can't really specify the engine by the displacement for a particular airplane without also specifying which specific engine you have.
There has been a very large, massive, voluminous, whatever you want to call it, discussion over the merits of these small engines, primarily as replacement for the old baffle-piston 35s, the dismal 40FP-S, and the many modified schneurle 40's that are even worse. The intent was to find an engine that would work properly on profile airplanes, as the Fox 35 doesn't, and *not require modifications*. This has been since there has been an internet in the current form starting in about 1993-94 when I did a series of experiments using all the small engines available at the time. As it turned out, they all worked pretty well and they all ran better than a Fox, as long as you ran them like other modern stunt engines (i.e. 4" of pitch) and not like "How I won the Podunk Internats and Chili Cookoff in 1954" type advice that tried to make them run with a 4-2 break at low revs.
The standout from that experiment, however, was the 20FP. You can take it straight out of the box, no modifications at all, bolt on an APC 9-4, and bolt it to a Flite Streak and have nearly a perfect run right off the bat without having to know almost anything about it, other than how to set the needle (peak out, then back off 5-6 clicks). It has a nearly perfect power change in the maneuvers and has the magic "slow motion" predictable feel even when it's going 4.5 second laps. It was a better runner than the 25FP, although it had less power, and a better runner than the "old" 25LA, which was a little down on power WRT the 20, and didn't run as nicely, although it would fly the same sort of airplanes mostly OK. It sounds and tachs very much like yours. That makes it workable (because the airplane is really small), but don't expect it to fly larger airplane or relate very well to the existing "new" 25LA.
Of course they discontinued the 20FP about 15 years ago, so I have been periodically suggesting that other people (who know what they are doing and are objective) take up the torch and repeat the same experiments with engines you could still get. I didn't do much of anything until Clint Ormosen invented the Stunt 25 event. I then got a couple of 25LAs, the "new" version, just to see what it would do. It, too, works perfectly straight out of the box with *no* modifications at all, and runs even better than the 20FP with even more power. Even the Skyray and Flite Streak are marginally too small for it, but close enough to make it OK with careful needling. At this point I have done a lot of testing on the ground and in the air
All you need to know about this topic, and about 10x more, can be found by searching for "brett 25la" and "brett 20FP" both here and on SSW (where a lot of this was discussed long after the fact, when the old RCO forum went away). Somewhere there is a 30-something page article by "Dirty" Dan Rutherford explaining exactly how to set up the 20 and most of it applies to the 25LA as well. Said setup being an APC 9-4 and the engine *exactly as it comes out of the box with no changes to any part in any way*.
Brett
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