Can anyone please tell me how much 63 feet lines would increase lap time as apposed to 60 feet.i have a scratch built cougar stunt plans by T . Stoker, which I crashed and rebuilt as a profile weighs 34oz fuelled . Running .35 Merco 10x5 prop and at the moment doing 3.8 sec laps way too fast for me,but my son loves it
The difference, to first approximation, would be about 5% (63/60 of 3.8, or to about 4 seconds a lap). It will be a bit slower in practice (maybe 4.1-4.2), but not nearly enough.
I am not familiar with the airplane (is this the familiar Kenhi design?) but a much more effective way to slow it down would be to switch to a 10-4 instead of a 10-5.
Having said all that, something doesn't sound right about this - with any reasonable airplane, a Merco 35 is *not* going to pull anything at 3.8 seconds on a 10-5, or at least, it will burn itself to a crisp trying to do it. It is either running *much faster*/leaner than is wise, or there's something wrong with the lap timing.
If anything, I would expect difficulty getting it fast enough to fly patterns with a 10-5, or at least, would have to run it nearly in a two-stroke all the time to get it fast enough. I think there is something else going on here that we are missing. 3.8 sounds like a meltdown.
Brett