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General control line discussion => Open Forum => Topic started by: Scott Richlen on June 21, 2018, 06:15:34 AM
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I set up the stooge and got 2 flights yesterday. It is surprising how much time it takes to get everything on a new plane set up and checked.
So, here is the challenge:
Neptune P-51B
52 ounces 54 ounces
Cardinal wing Similar area, but more volume
12-4 Pro Zinger 12-4 Xoar
9000 RPM 8850 - 9000 RPM
6+ sec. lap time 5.15 sec. lap time
Dang! I thought that I would get similar lap times. Not at all. If nothing else, I figured that the Neptune would fly a little faster. Nope!
The other difference is:
.281 venturi .305 venturi
5% nitro 7.5% nitro
So, today I'll be changing props and testing.
I think a 12-5 would be a little much, so I'm looking at:
12-4 Xoar
11.5 cut down from a 12-5 Pro Zinger
11-5 Xoar
11-5 Pro Zinger
11-6 RSM (from Dave R. who uses it on his Pathfinder)
Any prognostications from you prop wizards?
At 6+ second lap times the plane flew nicely and did most of the pattern. But at that lap time it slowed way too much on corners and got too dicey.
We'll see what happens today. By the way, it was stunt-heaven air yesterday!
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Scott I’d try the Goldielocks approach, go with the 11-6. If it’s too much back off to the Xoar 11-5. I’m not much on going for large diameter. More trim issues and could cause the engine to run hot.
Dave
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The Xoar 11x5 pulls my Brodak P40 arf perfectly with the .46LA on it. Not sure what rpm it's running at launch, but it's 4 cycle in level flight and 2 in nose up attitude. Runs the pattern on 4oz of 8% nitro. At near sea level (Whittier Narrows).
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What was interesting is that replacing the 12-4 ProZinger with a 12-4 Xoar got me to 5.15 second lap times at the same RPM. That is a significant difference in prop efficiency! I also flew a 11-5 Xoar and that was pretty nice, but I think I prefer the 12-4.
I tried a flight with 7.5% nitro but that was an "off to the races" flight. So, I'll stick with 5%. This is a new motor, so I'm sure it will settle down as I get more flights on it. I need to make a few changes before I fly next: move pressure tap on muffler, shim tank downward (inverted laps were faster than upright), and shorten tail wheel wire (too tall and affecting take-off).
On one flight the fuel line came off while inverted so I had a fun time doing an upside down landing. Happily, no damage at all.
I did some handle adjustments moving attachment points inward and also moved lead-out forward. Helped.
But 6 flights today so now I am up to 8 on it. I'm happy with how it is flying at this point.
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What engines?
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You're right, I should have mentioned it: LA-46.
Granted, they are no PA or Ro-Jett, but they are so easy to live with and so reliable and fit in so many designs, what more could you want? :)
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FWIW I've had good luck with both Zinger and Pro-Zinger 11x5's on the LA.46's.
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Try 10% nitro or even 15% LA 46 really like it.
Gordy
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FWIW I've had good luck with both Zinger and Pro-Zinger 11x5's on the LA.46's.
Try and 11.5-4 APC and launch at about 9500 RPM. Listen to Gordy.. The LA46 loves NITRO! Here in Tucson (Hot and High) I run 18-20% and a couple of guys have great success with 25%.
Another setup that works very well is to run an APC 12.25-3.75 at about 9800-9900 RPM launch speed! Really solid performance from the LA46.
Don't try to run it like a ST46...the LA power curve is a bit higher up!
Randy Cuberly