TF Tutor lap times

I've been flying my 41-ounce, OS .30-powered more-or-less Tutor on 60' .015 lines as my return to c/l flying after a 40-year layoff. All flying so far has been with a 10x5 TF wood prop.

The model was built with a d-tube wing and a new fuselage (longer motor mounts, longer and thicker ply doublers, inboard balsa tripler).

I have no idea of what would be a 'target' lap time and a valid way to attain it. Related to the lap times, I do not know what sort of lap times this aircraft at its current weight needs in order to have decent line tension when I start working up to overhead maneuvers.

Last session out, the a/c was timed at a stubborn 6.1 seconds/lap, considerably faster for the last 4 laps. Line tension seemed good flying at 6' altitude, softening as I approached 45 degrees' 'up'.

Any comments and suggestions will be gratefully received.

Thanks.

6 second laps are WAAAY too slow. Although George Aldrich "claimed" to fly at those speeds, I don't believe it. Line tension is needed and at those speeds with 60 foot lines you don't have it. 4.7 to 4.8 second lap times are much more reasonable on 60 foot lines. You can get slower lap times if you go to longer lines, but you need to remember, it is not just line tension, but the fact that the airframe itself needs to fly at a certain speed or it will not be able to develop the proper lift.

Leonard, thanks for the perspective. But no good answer goes unpunished...my immediate notion to speed up the lap time is to lose some prop diameter and gain some pitch, as in 9x6 propeller. I can't see that putting a 10x6 on the OS .30 would be a particularly good idea, but I don't know the engine well enough to toss the idea a priori. I think I'm asking how much prop does an OS .30 tolerate?

(as an aside, I'm running a ST needle valve I bought from you and a nylon venturi you made up for me).

>my immediate notion to speed up the lap
>time is to lose some prop diameter and gain some pitch, as
>in 9x6 propeller. I can't see that putting a 10x6 on the OS
>.30 would be a particularly good idea, but I don't know the
>engine well enough to toss the idea a priori. I think I'm
>asking how much prop does an OS .30 tolerate?
>
>(as an aside, I'm running a ST needle valve I bought from
>you and a nylon venturi you made up for me).

It will definitely depend on the brand of prop that you use. You say Top Flite. Is this the new "Power Point" Top Flite? If so, these are a narrow blade but a thick blade which gives an effective higher pitch. If it is an old Top Flite, they are wider, thinner blades with less effective pitch. Even the old power props had thnner blades. These are not Schnurle engines and will run slower. Personally, I would try a 10 x 6. If it is too much, cut it down slightly. I wouldn't think you would have to take it down to a 9 inch diameter, but increasing pitch while maintaining diameter is one answer, and decreasing diameter in order to increase rpm is another answer. I would suggest going up in pitch first, and then down in diameter if you need to.

Any idea what RPMs you are turning before launch?

I'd intended to know that --- tach was dead when I tried to enlighten myself. All's I can offer at the moment is 'fast 4-stroke' at launch, breaking into 2-stroke for the last few laps.

I'd go ahead and give the 10x6 a shot then for sure.

Hi Peter,
When you say you are launching at a fast 4 stroke, is it doing the "cackle" where it is hitting a touch of 2 stroke as it sits on the ground? Just breaking back and forth, but mostly 4 stroke. If all is right, it should unload into a fast 4 stroke in a lap or so after take off, and then break into the 2 stroke under load. if you can set it like that and go with a 6 pitch prop, you can then go back to the 5 pitch if it is too fast. 4.8-5.0 should be good for a lap time, but the performance of the whole package is more important than lap times. We check our lap times as a reference once we get the plane flying where it's happy.
Bill <><

Bill, that's a very vivid description of a ground setting. I'd been running richer than that, solidly 4-stroke. I'll hold that thought, put a new battery in the tachometer, and do some observing.

Thanks for the suggestion.