Good engine run

How do yawl get consistent engine run for your stunt engines. It is always a guessing game when I’m adjusting the needle valve right before take-off. What is a good procedure for setting up a good 4-2 break on O.S. 40 FP and Fox 35’s. My engines always seem to lean out on outside maneuvers. Is it the tank height? Should I use a tach? Help!!

>How do yawl get consistent engine run for your stunt
>engines. It is always a guessing game when I’m adjusting the
>needle valve right before take-off. What is a good procedure
>for setting up a good 4-2 break on O.S. 40 FP and Fox 35’s.
>My engines always seem to lean out on outside maneuvers. Is
>it the tank height? Should I use a tach? Help!!
>
>Kevin B

yawl \yol\ A fore and aft rigged sail boat carrying a mainsail and one or more jibs with a mizzenmast far aft.

y'all \yol\ var of you-all

>>How do yawl get consistent engine run for your stunt
>yawl \yol\ A fore and aft rigged sail boat carrying a
>mainsail and one or more jibs with a mizzenmast far aft.

It's a yawl with the mizzen behind the rudder. It's a ketch with the mizzen in front.

And you thought model aeroplanes could get pedantic.

Richard

>>>How do yawl get consistent engine run for your stunt
>>yawl \yol\ A fore and aft rigged sail boat carrying a
>>mainsail and one or more jibs with a mizzenmast far aft.
>
>It's a yawl with the mizzen behind the rudder. It's a ketch
>with the mizzen in front.
>
>And you thought model aeroplanes could get pedantic.
>
>Richard

good ketch

to be even more pedantic I suspect it's "...with the mizzen mast stepped behind the rudder post..."

lol

Oh my...someone else here that might know a cutter from a sloop...and recognize my Little Harbor Admirals Cup Warhorse.

Curt
SV FREEDOM

If all else is ok except for the leaning out on outsides, adjust the tank down 1/16 at a time. But get it close first with equal upright and inverted lap times--then set for inside-outside same.

You are running a Uniflow venting arrangement arent you?

Also--40FP and Foz 35 are apples and coconuts for setup.

Is the 40fp stock? Props?, speeds etc?

FWIW

I’m flying a stock 40 FP with a uniflow tank setup, 11-4 prop on a 38 Special bi-plane. The tank is level with the venturi. I plane on using the engine in a Vector 40. Thanks for the reply.

The stock FP probably won't do much of a 4-2 break. Try a fat 2-cycle and let it rev a bit more. Perhaps try another head shim and/or a green Bru-Line air filter to tame it a little. My Neumann Tower 40 does a nice break, but it has the boost port blocked and some other fine tuning done.

Try the tank raised above the NVA center about 3/16" to start. This is a peculiarity of profile installations. then fine tune from there.

LAST EDITED ON Jul-02-03 AT 10:34 AM (CDT)
 
>If all else is ok except for the leaning out on outsides, adjust the
>tank down 1/16 at a time. But get it close first with equal upright
>and inverted lap times--then set for inside-outside same.
>
Normally, the correcting adjustment is moving the tank UPWARD when lining up with the engine center line, and trying to get rid of RICH inverted settings. My experience is that you will usually need an average of 1/8" for a Uniflow tank. In other words, your engines are doing something different from mine.

>You are running a Uniflow venting arrangement aren't you?
>
The older atmospheric-vented tanks don't seem to exhibit near as much need for an offset tank. Also, some engines need adjustment all by themselves to a greater or lesser extent than others. Fox CS Mk IV engines needed 1/4" of tank offset (upward) with GRW Chicken Hoppers.

>Also--40FP and Foz 35 are apples and coconuts for setup.
>
By which we separate "classic" breaking run engines from "high-low" engines. Back in the early dawn of using Schneurle engines for CL, I had one each of the first series of FP's, a 35 and a 40, with the iron piston and steel cylinder. There was no APC prop brand at the time, or else I just wasn't seeing them yet in any LHS. An 11-3 might've encouraged me back then, but I sold both to an RC flier after a short testing period when the FP's weren't slow enough for stunt, nor fast enough for combat.

.
Kiwi

I agree with Kiwi:

But I might have been unclear on the tank height adjustment. My experience (albeit limited) is the (profile mounted) tank will always end up ABOVE the NVA center. After you get equal upright and inverted speeds, fine tune the height by comparing inside/outside loops. If it is going faster in outsides, LOWER the tank--like 1/32 or 1/16 at a time. It wont take much. It will still end up ABOVE the NVA.

I havent done this in a while--and I'm easily confused now that I have my ARP card. Perhaps Leonard will confirm the direction of movement.

And Pauls comment about needle adjustments AFTER the flight is a good practice. I have seen some otherwise good flights ruined by fiddling around with the needle before flight.

Once you find a good speed to fly, the tach makes it easy to double check the pre-launch speed but after you have gained some experience with a particular set-up, you will refer to the tach less frequently.

Using a tach as a beginner will definitely bring better consistency to you efforts tho...just MHO.

FWIW

>How do yawl get consistent engine run for your stunt
>engines. It is always a guessing game when I’m adjusting the
>needle valve right before take-off. What is a good procedure
>for setting up a good 4-2 break on O.S. 40 FP and Fox 35’s.
>My engines always seem to lean out on outside maneuvers. Is
>it the tank height? Should I use a tach? Help!!
>
>Kevin B

something no one has mentioned so far but you did is a tach. On a Fox 35 you can set the engine just before the break. Set it so it 4-cycles while sitting on the ground but breaks when you raise the nose to about a 45 degree angle. You may need a different needle in the critter, though. I have learned Fox needles give three settings: 1) too rich. 2) too lean. 3) won't run.

On the FP and most others use your tach. Some of this will be trial and error until you find your set up. But with the tach you can go back and get consistent settings (or at least very close). You will eventually find that one click leaner or righer will be just right from a previous run, but you will be in the "ball park". Without the tach you are mostly guessing.

And as to tachs, there has been a bunch said about these. Many of the cheap commercial tachs are not accurate. However, if they are consistent they will work for you if that is the only tach you use. Set it to your tach and take notes (keep a log) so you know where to set it and when. Just be advised that if you use your tach one day and someone else's another, well...??

If my tach reads 11500 rpm for example and I launch the plane at that reading and have a good engine run. Would I consistantly have a good engine no matter what the humidity, temp. or time of year. What I'm asking is can I rely on a tach. to assure me a good engine run.

Thanks,

Kevin B.

Kevin,
I have had fairly good luck using the readings that I obtain at my home field elsewhere in the country (I live in Michigan and have flown as far east as PA and west as IA). About the only thing that I change the engine speed for is the wind conditions. The things that I keep constant are my fuel and the propeller. As Len has mentioned, keeping a log of your engine runs helps a bunch. When I do switch fuels for a particular airplane, I usually have a very good idea of how much to put in for a specified run time and any variation that I may need to make to the ground RPM.
My tach is a $20 special that I acquired some years ago for flying RC. There is nothing special about it other than it is the one I use and it has worked well for me. Does not matter if my reading of 8700 rpm is really 8900 as long as the engine performs the way I want it.
As for your original question, do as Len has suggested and keep a log of your activity. At the beginning, you may want to record launch speed, type of fuel, amount of fuel, type of prop, lap times upright and inverted and total run time. Also make notes about what the engine/airplane do during a flight. Takes the guesswork out of the adjustments when you get home. When things become more consistent you can probaby drop the amount of information that you jot down, but it is still a good idea to keep the log running. I find that it helps with fuel load adjustments to prevent any potential overrun conditions.
Good luck. Hopefully some of my ramblings can help.

> On a Fox 35 you can set the engine just before the break.
>Set it so it 4-cycles while sitting on the ground but breaks
>when you raise the nose to about a 45 degree angle.

Really? Thought it needed to be at least on the edge of a fast four breaking into a rich two on the ground, or a rich two breaking four. How much nitro to be in a dead four at launch on a Fox 35?

LAST EDITED ON Jul-02-03 AT 09:47 PM (CDT)
 
>> On a Fox 35 you can set the engine just before the break.
>>Set it so it 4-cycles while sitting on the ground but breaks
>>when you raise the nose to about a 45 degree angle.
>
>Really? Thought it needed to be at least on the edge of a
>fast four breaking into a rich two on the ground, or a rich
>two breaking four. How much nitro to be in a dead four at
>launch on a Fox 35?
>
The correct "sound" for an unmuffled Fox 35 at takeoff used to be described to be when it hiccoughed into a two-stroke for 2-3 beats, every 40-50 four-stroke beats. You can also run a few of them slower than the break, on a light, or small plane, and those engines chug along neatly right to the overhead stuff where if they DON'T break, you can forget the rest of a pattern. I had a 25 that would do that with a TF Peacemaker, and a 35 I acquired in a Magician did so pretty well also. Not many Foxes can run that "granny gear tractor" style; but all three of my G21-46's, and my first Max-H 40 were happy to run that way.

I don't think fuel choice directly affects whether or not you can run any 4-2-4 engine that slowly, although it surely has some effect, but a good HOT plug is definitely in order.

.
Kiwi

Hello,

In our club in Herentals, Belgium, we don't adjust the engine before take-off. We adjust it after the landing. Was the run too lean? We open a few clicks before starting the engine again. Adjusting a running engine is always a gamble because the temperature of the engine at take off is NOT the temperature during flight. And engine temperature defines for a big part how the run will be.

FWIW.

Regards,
Paul

Generally speaking I adjust based on how the engine ran last time. A tach is good for baseline when you havn't run the engine in a while. I think the ideal is to have enough HP that you can let the needle alone and not have to tweak to the exact adjustment.