FP .20 setup

I converted a steel sleeve RC FP .20 for a Super Clown by fitting the OS venturi (.260) and NVA (.135) and wondered if this was truly a good setup since I'm starting to fly in a more demanding manner. It seems that the venturi is used on various size engines which leads me to believe that it may not hit the mark for the little .20. Also, are there any other easy mods to dial this engine in? Stock muffler currently.

Also, with a 2.0 oz. GRW profile uniflow tank, there are two forward facing ports outboard on the upper and lower wedge panels respectively. I assume the upper one is the uniflow (no diagram). This location puts it right behind the engine. Run it like this? Route to clean air? Or use muffler pressure? I'm willing to experiment, but I'll take a hint from others with lessons learned.

The one I am running is box stock. I can't say that I have measured the venturi, so it's whatever it came with. Changed to a ST NVA and a tongue muffler. Run muffler pressure to a uni-flowed old Perfect tank. On a Ukey 35 and a Taipan 9-4, it runs a fat 2 cycle that is very steady, generally burps once and quits. Gotta measure that venturi if it ever needs to come apart.

LAST EDITED ON Feb-09-04 AT 08:39 PM (CDT)
 
Some local flyers are having good luck running a .228 venturi, I think with an OS NVA of .135 diameter.

My recommendation is what Elwyn mentions, a .228 venturi and stock OS needle. The stock venturi (for Kelvin's sake) is a .257. By changing to the ST needle he has reduced it to the equivilent of a .238 which still isn't bad, but better suited for the .25. If you change to the larger needle, you are stuck with it. If you change venturis, it is a simple thing to open it up or change again if you think you can find something better. Sometimes it is good to have several in your arsenal to dial it in. A lot will depend on the prop you use, fuel, muffler, etc.

Hi Len,
Are you suggesting a venturi in the .232ish neighborhood, then? If I am getting good fuel draw and plenty power, what would I gain besides fuel mileage from the smaller venturi? I'm flying at about 1700' MSL in mostly reasonable temps (90 is considered pretty hot, here) but high humidity.
As noted, a Ukey 35, stock except for 1/32nd ply doublers, 2 wheel gear, and a better pushrod. Taipan 9/4 prop and Sig 10% 50/50 fuel.
As always, appreciate your thoughts,
Kelvin

>My recommendation is what Elwyn mentions, a .228 venturi and
>stock OS needle. The stock venturi (for Kelvin's sake) is a
>.257. By changing to the ST needle he has reduced it to the
>equivilent of a .238 which still isn't bad, but better
>suited for the .25.

LAST EDITED ON Feb-09-04 AT 10:48 PM (CDT)
 
>I converted a steel sleeve RC FP .20 for a Super Clown by
>fitting the OS venturi (.260) and NVA (.135) and wondered if
>this was truly a good setup since I'm starting to fly in a
>more demanding manner. It seems that the venturi is used on
>various size engines which leads me to believe that it may
>not hit the mark for the little .20. Also, are there any
>other easy mods to dial this engine in? Stock muffler
>currently.

I don't know about the steel-liner motors. I do know that the ABN stockers, including stock .257 venturi and stock spraybar (and for that matter stock muffler with baffle in place), run perfectly well - in fact so well that I would strongly discourage anyone from significant deviation. It's more than satisfactory for me, and I'm pretty picky - I figure if I can get 540 point patterns with a 20FP and a Skyray, it's probably good enough for a Super Clown. I really like the silky-smooth power delivery.

This size venturi seems to work much better on the 20 than the 25, by the way. On the 25 its seems too large, on the 20 it seems just fine.

I would encourage you to try it with a 9-4 APC, and a good 10 or 15% fuel. DO NOT bog it down with more diameter or pitch - it will be very, very unhappy. If you must use oversized props, then maybe you do need a smaller venturi.

>Also, with a 2.0 oz. GRW profile uniflow tank, there are two
>forward facing ports outboard on the upper and lower wedge
>panels respectively. I assume the upper one is the uniflow
>(no diagram). This location puts it right behind the engine.
>Run it like this? Route to clean air? Or use muffler
>pressure? I'm willing to experiment, but I'll take a hint
>from others with lessons learned.

I have no idea about the GRW tanks, and which pipe is which. Assuming you do figure it out (it's easy enough to just fuel it up and see where fuel comes out at various angles), you can try using muffler pressure into the uniflow, but I found that it would work only about 80% of the time. The other 20%, it would go about half a tank and take off lean. Vented to air worked OK.

After Godzilla's valuable observations about clunk tanks at the 2002 NATs, I tried a pretty much stock Sullivan clunk on the 20FP, and it seems to work well. I set it up stock, with the exception of a third fill tube, as a suction tank. I put the muffler pressure to the vent. It seems to work quite well, and the tanks are both cheap and widely available. You have to be a little bit careful about not getting it too lean at the beginning of the flight, but it's not that hard. I think it's worth a try.

Brett,
Upon my return to C/L I quickly learned that the -6 props like we used on Foxes and Enyas make for some serious excitement (and dizziness) with the newer schneurles like the LA 15 and 25. I now use -3 (training) and -4 props to keep speed under control while letting the motors run closer to where they want to. I have yet to attend a meet and see how stunt planes really should fly, but my Skyray with the 25 seems to fly okay since it doesn't hiccup very often, climbs well, and usually doesn't run away in dives and level flight with a 10-4 Zinger. Still, I have to be really careful not to let it get even a little happy (lean) before takeoff or I'm in for pretty sporty ride on 52' wires (maybe I should fly on 60 footers and let her run a little?). So, consequently I'm not surprised by your success with the FP 20 on the Skyray "35". Do you pretty much "turn her loose" or do you still have to run it kind of wet to keep the speed right? The reason I ask is that I was hoping to have a more conservative motor to plane ratio this time around thinking that I could "let it run" so that it might "police itself" speed-wise by natural engine/prop limitations. But the Super Clown is significantly smaller and less draggy than the Skyray and it sounds like I could have a surplus of available power again.

Anybody:

Fuelwise, should I run this steel liner FP 20 on the standard 10% omega RC pink stuff (I think it's 18% oil 50/50). Or, my doctored up version with additional castor that I run in my Fox and Enya (somewhat less nitro content).

I think the "Pink Lemonade" fuel has a bit less than 18% total oil since they measure it by weight and not by volume and I'd bet the synthetic-castor ratio isn't anywhere near 50/50. For an iron piston non ball bearing motor I'd want at least 25% oil with at least 50% of that oil castor.

>I think the "Pink Lemonade" fuel has a bit less than 18%
>total oil since they measure it by weight and not by volume
>and I'd bet the synthetic-castor ratio isn't anywhere near
>50/50. For an iron piston non ball bearing motor I'd want at
>least 25% oil with at least 50% of that oil castor.

Omega stinketh as fuel for Iron piston engines. I would, personally, recommend using all castor, and then 20-25% oil would be fine (what we use.) Omega, as I recall, is about 3% castor, and *maybe* 18% total oil by weight. Use a lot of good oil and that iron piston engine will last longer than you (probably). Use poor oil, and you might only get one flight out of it.

>Omega stinketh as fuel for Iron piston engines. I would,
>personally, recommend using all castor, and then 20-25% oil
>would be fine (what we use.) Omega, as I recall, is about
>3% castor, and *maybe* 18% total oil by weight. Use a lot
>of good oil and that iron piston engine will last longer
>than you (probably). Use poor oil, and you might only get
>one flight out of it.

Of even worse one flight to mess it up, and then 100 flights before realizing it was messed up.

When I was doing all that fuel stuff, Omega was not way off in the purported vs. actual oil content - I got about 16% by volume, which is pretty close given the error in the method. I would be surprised if an Iron-piston FP would like that very much.

My experience has been entirely with the ABN versions, and they run like sewig machines, straight out of the box.