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General control line discussion => Open Forum => Topic started by: Fred Quedenfeld jr on July 05, 2017, 06:24:12 PM
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New primary force
with Brodak 40 and full muffler 10% nitro 21% oil
Engine well broke in
clunk tank with uniflow soldered to clunk
Upright and inverted seem the same
consecutive inside loops good
consecutive outside loops seems to go learn
does not seem to go lean on outside of lazy eight
Any suggestions
Fred Q
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I'd lower the tank 1/16" and try some insides and some outsides. The H8's don't seem (to me) to always have the same effect as 3 consecutive loops. I'm sure somebody will dispute this, and/or suggest converting your plane to electrons. n~ Steve
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I'd lower the tank 1/16" and try some insides and some outsides. The H8's don't seem (to me) to always have the same effect as 3 consecutive loops. I'm sure somebody will dispute this, and/or suggest converting your plane to electrons. n~ Steve
Is that a challenge or a comment?
Engines seem to react slowly to tank height, sometimes, so yes, I'd move the tank and see.
And if I switched to electrons I wouldn't know whether to move the battery up or down if it went lean on the outsides. So there.
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I've found that soldering the vent to the clunk is more trouble than it's worth. I use a third pipe bent towards the outside of the tank to work best.
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I've found that soldering the vent to the clunk is more trouble than it's worth. I use a third pipe bent towards the outside of the tank to work best.
Full disclosure: I'm not a frequent user of clunk tanks (got an all metal one on the old Doctor running a four stroke, the output of which doesn't change much with fuel pressure variations...it's a four stroke, for Pete's sake!) and have never like the concept of a movable uniflo vent in any tank as such is totally at odds with the intended function of a uniflo vent...which is to provide consistent pressure at the tank end of the tube until the fuel level uncovers the vent toward the end of the flight thus reducing/eliminating the gradual leaning of the engine as the tank empties.
Beyond that basic function it is also true that the location of the "tank end" of the uniflo tube "is" the tank as far as the engine is concerned. You can, for instance, trim a difference between upright and inverted lap times by changing the position of the uniflo vent vertically inside a fixed tanks location. On my tanks, all of which I make for myself (and almost entirely for inverted engine installations) I always solder the inside end of the uniflo vent above fuel pick up tube to largely insure I'll never have to "raise" the tank to correct an upright/difference in lap times. By having the tube above the center line of the tank I can all but guarantee I'll never have to "raise" the tank" (requiring the removal of significant engine bearing material) and any likely upright/inverted mismatch will be correctable via shims between the tank and the motor mounts.
The above is the reason the concept of a uniflo pickup free to move up and down in the tank due to gravity or g-force effects is anathema to me. I would no more want the uniflo vent to move up and down with G-forces than I would want the entire tank to do so. If some pilots want to increase the difference between the RPM/output in a 4-2-4 setup they might enjoy the extra boost which might result. In a modern low pitch/high RPM set-up less so.
Having said all that, I'm aware a number of excellent fliers are happy and competitive with such a set-up, however, so I could, once again, be all wet.
Ted
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Having said all that, I'm aware a number of excellent fliers are happy and competitive with such a set-up, however, so I could, once again, be all wet.
I think it works because the vent is either thunked against the upper wall of the tank or the lower, so you still control the run by moving the tank up or down. I dunno -- I never set up my tanks that way.
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Love this so much I gotta repeat it "And if I switched to electrons I wouldn't know whether to move the battery up or down if it went lean on the outsides. So there." Anyway, another thing to do is pick up a normal Uniflow Tank from someplace that still makes them and swap it in and see if it works better or makes a difference. You never know and you may end up ditching the clunk all together.