stunthanger.com
General control line discussion => Open Forum => Topic started by: Paul Taylor on February 28, 2014, 08:53:46 PM
-
Ok contest day.
Early morning:
First flight - air is cool, not Tee shirt weather. Claim winds. Little over cast.
Fuel up, start the engine, and first flight is over. No issues.
Round two is after lunch.
It has now warmed up to tee shirt weather. Wind has picked up a little - just about right for flying.
What do you change before you next flight if anything?.
Turn the needle in a few clicks?
Maybe a prop with more pitch?
Ok lets have a yak about it.....
-
First, I change my shirt.
If you're flying some little thing with an FP 20 an E2030 muffler and an APC 9-4 prop*, you adjust the engine by ear so that it's running in its sweet spot. You can do that because it's an FP 20 with an E2030 muffler and an APC 9-4 prop.
If you're flying something like an LA 46, you set the launch RPM with a tach to whatever you've determined is right for that airplane. Messing around with the prop is for getting the combination working in the first place, not for dealing with temperature changes.
I dunno what the guys flying Foxes or PAs or piped engines do -- probably they either set the thing by ear to the right depth of 4-stroke, or they set it to a certain RPM.
If you change altitude a great deal you may want to mess with the prop and/or fuel.
As winter turns into summer you may want to go to higher nitro fuel.
This is all out there in prior posts, much of which I am regurgitating. In my personal experience, sticking close to the Pacific Northwest, I just launch at 9050 RPM** and fly.
* The Brett Buck Tuneup.
** At least nowadays -- I had been launching at 9300, but I like 9050 better. I may get skeert by the first really windy day and change my mind back.
-
Launch at the same rpm, whether by NV if slight, or nitro if significant. Use the tach, that's what it's for! H^^ Steve
-
Launch at the same rpm, whether by NV if slight, or nitro if significant. Use the tach, that's what it's for! H^^ Steve
Steve flies piped, if I recall correctly.
If you're flying electric you should also always launch at the same RPM, no matter how much nitro it takes.
-
I take the snow blower and the tire chains off and put the mower deck back on I can't wait ;D T.J.
-
Yeah, I've watched guys get out early in the day when the sun has barely gotten over the horizon and put up test flights. Usually changing the needle or fuel on each flight until the pilots meeting. Then here we stand with our jackets on and listen to the Event Director give his speech. Then we look and see when we fly and go sit. Then after the first round flight we wonder why the plane didn't fly like it did earlier in practice after the temp has raised about 15 to 20 degrees. This is early spring meets. I don't think Tuscon has that problem. During lunch break they put up another practice flight and hopefully fly soon after, because the temps will change again. Myself I learned from Bigiron(Marvin Denny) and Siverfox(Lew Woolard) to burp the engine with primes until it runs the prime out. I don't like fiddling with the needle on contest day unless it is really far off setting. This is my way and observations. H^^
-
My last CL competition was at the 2010 VSC. I flew two practice flights each on Sunday and Monday. Flew near last on Tuesday, flew near first on Wednesday. I flew with the same needle setting I had been flying with at about 800 ft altitude near Austin. Because I was flying a Fox stunt 35, I could not tell any difference in how the engine ran under different conditions. I did over prime it in the cold morning. It started backwards three times, but that was not the engine's fault. This was with a 27 oz airplane, of course. With a 48 oz airplane, I would probably have made slight needle adjustments.
-
As the temperature rises you will always have to go in on the needle and/or up on nitro to get the same performance as you do in cooler weather. You should always shoot for the same rpm to get the same lap speed and if the same rpm does not give you the same lap speed or performance that you are use to you need to add nitro. I usually run 10% Sig Champion year round. On cool mornings the engine does make more power but I have learned to deal with it because I like to use the same fuel all day and the 10% is good for warm-hot weather with my setup.
Now with electric you can obviously set the rpm to be the same no matter what the temperature but that does not mean that the same rpm will work all day if there is a big shift in temp. I would assume that they also have to add a few rpm to get the same performance as they do in cooler weather, everything else being equal. The hotter the air, the thinner the air, so you have to make up for it somewhere...
Derek
-
As the temperature rises you will always have to go in on the needle and/or up on nitro to get the same performance as you do in cooler weather. You should always shoot for the same rpm to get the same lap speed and if the same rpm does not give you the same lap speed or performance that you are use to you need to add nitro.
However, as you note, if you have to change nitro during the course of the day, you are probably to close to the edge of something. The setup should probably be changed to permit anything from maybe 55 to 100 degrees with no changes on the same fuel, since that is clearly possible.
Having said that, I had to mix in a bit of 5% with my 10% the other day (in the syringe), but that was not because it wouldn't run right. It was because I couldn't get through the whole flight on RO-Jett 10% when it was 47 degrees.
That's the way to do it, if you have to - suck up the required quantity of 5% in the graduated syringe, then the rest of the first syringe of "normal" fuel. That way you can change it on the fly easily. I know of a certain national champion who shall remain nameless who does that INSTEAD OF moving the needle during the day. I can't say I would recommend that myself (since it takes to much experimentation to figure it out, and you have no way to change it "on the fly") but it's viable.
Brett
-
Steve flies piped, if I recall correctly.
I haven't noticed any difference in this between muffler/Magnum XLS .36, muffler/OS .46LA and PA.51/pipe or .46VF/pipe. As the day warms up, you either need to lean the NV or add nitro to get to correct launch rpm. Maybe next year, I'll try the nitro change route, but I probably still won't use a syringe. D>K Steve
-
I haven't noticed any difference in this between muffler/Magnum XLS .36, muffler/OS .46LA and PA.51/pipe or .46VF/pipe.
It's what I suspected, but I had made a statement that "I dunno piped" -- so I wanted Paul to know that what you said was valid for piped engines, too.