Thanks for the reply Brett, I only used the FP-20 because I scored it on the Bay for $20.00. I flew it three times and the FP was plagued by runaway. I know there are a few tricks to cure this problem, it has the small O.S. venturi and an O.S. needle valve I also use a chicken hopper tank. I read in an article to turn the hole in the venturi to the 4:00 o'clock position use 5% fuel and restrict the venturi to get a smoother run. How about the prop?
Rich
P.S. If it turns into a project i'll just use an LA-25
I don't know what "tricks" you are talking about, there are no tricks, and I certainly don't recommend rotating the needle valve or 5% fuel! The trick is to use a tank that is no more than 1.5" wide, and use an APC 9-4. Use at least 10% fuel, 15+ is OK.
From 15 years ago:
Stock 20FP ABC
Stock Muffler
Stock Venturi
Stock Spraybar
APC 9-4 or MK-Custom 8.5-4.5
Low-profile Uniflow hard tan, no pressure
or Sullivan SS-4 clunk tank, set up per instructions (except third tube for overflow, convenience only), suction with muffler pressure
Thunderbolt 4-cycle or R/C plug
Sullivan "Crap Trap" 2-stage filter
Sig 10% Champion fuel
Skyray/Flite Streak-size model
60-62 foot .015 stranded lines
lap time will be between 4.6-5.0. Can be slower or much faster if desired
Ringmaster will be flying about 3.8-4.0 -second laps on 60' lines at proper setting with 9-4.
No break-in required, two-three tanks on ground desirable. to stabilize fuel consumption
Set at about 11,300 on the ground, or peak out and then back off about 5-6 clicks until its noticably off-peak. First flight may sag on hard outsides, will fix itself in a few flights. Fuel consumption will be close to 3.5 oz on first run, will decrease to about 2.4-2.5 oz after about 15 flights, then stabilize.
In-flight setting in level flight should be a rich-medium 2-stroke. If airplane is too fast, reduce venturi with Bru-Line "fine" air filter. If too slow (very unlikely), lean out, or move to 15% nitro. Can be run near peak with little chance of damage. Speed can be tweaked slightly with needle, but running a 4-stroke in level flight will likely result in excessive speed variation in flight. In extreme cases (Ringmaster), speed can be reduced with ST needle, but this is not necessary for run stability, just power reduction. Use 15FP on Ringmaster instead.
The engine will spin much more prop. But don't. When in doubt, add less prop.
Things NOT TO DO:
modify muffler
replace muffler
modify venturi
run more load than APC 9-4 prop
run hard tank with pressure
run excessively wide hard tank
add head gaskets
modify timing
plug up boost port
Brett
Topic: what prop to use? (Read 1743 times)
