kine length/4-2-4

Isaw a comment in another thread about an os40 fp using an unfamiliar prop doing a 4-2-4 break on 60 foot lines. Not too amazing but I got the feeling from reading it that the auther implied that it would only do that run on that particular length of line.
Now this is a new phenomina for me and i was unaware that such a thing could happen. So my question is , Can you have an engine set up that it will 4/2/4 only with a particular line length. I didn't think so but ?

That was me. Line length is merely another tool used in trimming. Most people like to fly at lap speeds at which they are comfortable, and usually you want to stay under 5.5 seconds. We usually shoot for around 5.3 to 5.4 unless it is an extremely windy day. That 11.5 x 4 APC prop mentioned was a lot lower pitch than the 12.5 x 5.5 Bolly, although the APC has a thicker airfoil which compensates some and the smaller pitch allowed the engine to wind up a bit faster. Still, the plane would fly slower on that prop, but lap speeds would be fine on the shorter (in comparison) lines.

You are right, however, line lengths have nothing to do with engine characteristics unless people try to compensate and set an engine differently in order to compensate for desired lap speeds.

Leonard Neumann

>
> ... Can you have an engine set up (so) that it will 4/2/4 only
>with a particular line length. I didn't think so but ?

Leonard answered, and I had to have a comment. My internet routing today is cooperating and I got a fast response to my attempt to respond, first time in a lo-ong while.

When the FP line was fairly new, and already being offered in a C-L version, Riley Wooten got in a bunch to sell at fairly heavily discounted prices. I got both a 35 and a 40 at the time (1988, maybe?)

Mine didn't respond well to the kinds of minor tuning efforts I made (added head gaskets, venturi from the 25 size FP, low pitch props). At least, neither would perform in a 4-2-4 manner for me. But I did find props for the 35 to allow it to rev some and run in a rich two cycle that was relatively acceptable. I could not get the 40 to "stay" at the needle setting I wanted. It was going to rev faster than that no matter what. It seems to me I had APC's and those weren't the right ticket, but not any of the "11 1/2" diameter APC's.

I thought at the time I needed different 11-4's, or perhaps some 12 by 3 1/2's, but I was able to pass on both of my early FP's to RC fliers, selling them without financial loss. At some later point, I acquired another 35 FP, still NIB, and more recently another 40 FP (not so unused) - yet to test in any depth. My one-time shop area remains in use to store garage- type stuff while the process of enclosing what formerly was the carport stretches on forever.

I still have one of the planes I ran the old FP's on, but can't recall what lines I used (64's, I think). I suspect that the FP's I once owned were still of the iron piston, steel cylinder type, like the early FSR's and SF's were. As such, they might have been more radically timed than the ABC (ABN) FP's ended up being. The FSR's are quite certainly timed for much higher rpm's than today's FP's are.

I remained doubtful of the usefulness of any of the larger FP's, without custom retiming, for C-L sport and stunt, until the surge of popular opinion in their favor ran over me. But it has been my usual practice to put 40-powered planes on 62-64 foot (handle to centerline) lines, until I began playing with Max-H 40's.

Incidentally, in spite of the doubts of certain FP promoters, the official printed horsepower claims made by OS for the Max-H 40 and FP 40 were in favor of the Max-H by a fraction. My fun-fly Slow Combat plane with a Max-H 40 on it is a trifle fast on 60' lines, but still a kick to fly. Corners on square stuff come just a bit too quickly one after another for "precision", however.

I will have some longer new lines again, soon, if I still don't locate an older set, but when Leonard refers to 11 1/2 APC's, that size is something I've not seen on the shelves, and the 12 1/2 Bolly is a prop that I refuse to try paying for. I suspect that he would've been using an SSW 40 rather than a stocker, too.

According to some of the engine advertising circulars that came with some NOS engines I've obtained, there once were Max-SF 40's and 46's offered with C-L intakes, but neither of those seem to be common on eBay, nor particularly broadly known to have been available. I wonder if any owners of those went through what I did and gave up on them also.

I do know that the idea of trimming a foot or two at a time off a set of lines was not mentioned as part of "trimming" when I was first flying patterns. We ended up with odd length lines sometimes, but from cutting off factory eyelets to put new ones on, or just bad measurements on ready-made lines. It certainly is a handy way to deal with mismatches between a plane's setup speeds and its pilot's response speeds.

K.

Just to sort through some confusion, the timing on the iron piston versions is exactly the same as on any of the newer ABN versions. They ran a little different, however, but they are still my favorites in modified form. They run forever, and are easier restarted when hot. Do use all castor on them, hoever. I think this, more than anything, is the reason for going to the ABC or ABN versions. They make these primarily for RC flyers, after all, and most of these guys don't like castor oil.

I still have 8 new iron piston/cylinders squirreled away. Enough to keep these running for my life time and probably Matt's, too.

Leonard Neumann