slowing lap times

[Ed Carlaw]

I have a Super Clown with a .25fp running a 9X6 prop on 60' lines. It's running sub 5 second laps. I want to slow it down to a 5.3 to 5.5 second lap. Any advice on prop diameter and pitch?

[Brett Buck]

I have a Super Clown with a .25fp running a 9X6 prop on 60' lines. It's running sub 5 second laps. I want to slow it down to a 5.3 to 5.5 second lap. Any advice on prop diameter and pitch?

    APC 9-4. 6" is *way* too much pitch - and at 25FP it *way* too much engine to easily handle on a Super Clown.

   I will also note that you aren't going to get very good performance on a Super Clown going that slow, which is OK, because you will have a lot of trouble getting it that slow. Running properly you may get 4.5-4.6, but it will seem slow in the maneuvers because of the predictability.

     Brett

[Ed Carlaw]

Thanks Brett. Any suggestions on an engine?

[Brett Buck]

Thanks Brett. Any suggestions on an engine?

  If you already have this combination, I would suggest just trying a conventional (3-4" pitch) prop and experiment. The key to getting these engines to run smoothly is unloading them so they can spin at the speeds they want without generating excessive speed. But your target range is on the lower end of full-house competitive stunt planes - I usually fly my piped 61-powered 4 pound airplane at about 5.2-5.3 seconds.

    Alternative engine would be a 15FP with something like an 8.5-4 of 8.5-5.

   But, while you might get some engine backed off enough to go your target lap times, it would likely only be good for level flight or gentle maneuvering. It's not going to perform very well at those speeds regardless of the engine.

     Brett

[Ed Carlaw]

Thanks I will try a lower pitch prop. Just basically using it for training purposes so straight and level is basically what I'm looking for right now. I will tinker with things as time goes on. Ed.

[Brett Buck]

Thanks I will try a lower pitch prop. Just basically using it for training purposes so straight and level is basically what I'm looking for right now. I will tinker with things as time goes on. Ed.

  Then, by all means, just put a 9-4 on it and have at it!  This will be perfectly good for straight and level. If it is still too fast, until you get your legs under you, put the prop on backwards.

    Note that while the Super Clown will never be confused with an Impact, get it straight, get the controls set up correctly (very very slow elevator movement) and it has potential to be a very good and easy-to trim stunt trainer that will get through patterns, if it lasts that long. Overkill power just makes it fast, but the experience is that even at pretty good speed it is very easy to handle.

     Brett

[Steve Helmick]

100% agree with Brett, but would note that all 6" pitch props are not 6" pitch. Master Airscreweds are typically under their rated pitch by a fair amount. APC's are MUCH better propellers, but some folks don't like the looks or the color or some such rot. Don't be one of those guys!  Steve

[Tim Wescott]

4" or even 3" pitch 10" diameter prop, like Brett said.

If you can't get a smaller engine, or feel it's too much trouble, then you can make the engine act smaller by putting a smaller venturi on it or restricting the one you have. 

Or, if you have the RC throttle for the engine, slap that on and set it to part throttle.  It'll make starting weird (because it'll be an air bleed carb -- you'll need to prime it by squirting fuel in the carb, not choking, or close up the air bleed all the way).  The nice thing about this approach is that you can easily set the speed -- just remember to adjust the needle after each change in throttle setting.

Restrict your venturi by carving a bit of balsa and shoving it into the space on one side of the needle valve.  Or get some fine nylon mesh from a florist's shop (maybe wrapped around some flowers to give to someone).  Cut those into squares, and pile them on the end of the venturi.  With as much restriction as you probably need, you'll need an insane number of layers -- so, start carving.

[john e. holliday]

I am still convinced that lap times are over rated.  Fly the airplane at the speed it is happiest at.  Then when you are satisfied after a half dozen flights, then then time you lap speeds.    In ll the pnes I have they have a happy medium ffr each one for me.   

[Brett Buck]

If you can't get a smaller engine, or feel it's too much trouble, then you can make the engine act smaller by putting a smaller venturi on it or restricting the one you have. 

    Exactly - what you need for flying around level and not getting dizzy is a lot different than trying to learn stunts with it, so there is no need for swapping engines, etc, to try to optimize the power, it just has to be slow enough to not fall down for a few minutes, until you get over being dizzy, etc. Just use the nice, very reliable and easy-to-handle engine you have and worry about doing it "better" later.

     Brett

[Brett Buck]

I am still convinced that lap times are over rated.  Fly the airplane at the speed it is happiest at.  Then when you are satisfied after a half dozen flights, then then time you lap speeds.    In ll the pnes I have they have a happy medium ffr each one for me.   

   If by that you mean, don't chase a particular lap time, of course. Lap times are only to inform you on how the airplane is flying, and whether whatever change you just made  (tipweight, leadouts, etc) feels different because of the change, or because you are flying .05 seconds a lap faster or slower.

    Same thing with RPM, you don't screw the needle in and out trying to get a set speed, you adjust it in small increments around a known working needle position, and then use the RPM to see how much it affected it. If it is way faster or slower than you expected, then, you know something else has changed as well. Or, for making a gross change, you can see what it did - then fly it, get the speed you need, and see what it  is now.

     All these "advanced tools" (like the always-exotic stopwatch and tachometer) are there for are to give you more information with which to sort out the same old changes you always had to make. You take out 4 grams of tip weight, you fly it, it feels a little light on the lines. Is that because of your 4 grams, or because it happened to be 1/10 sec slower? That sort of thing.

    Brett

[Tom Luciano]

Ed,
  it was mentioned on the hangout that you are located in New Jersey.  If so, where are you located? We can get you some help between Middlesex, South Jersey guys and Philly Flyers. I'm in Hunterdon County

Tom

[Ken Culbertson]

I am still convinced that lap times are over rated.  Fly the airplane at the speed it is happiest at.  Then when you are satisfied after a half dozen flights, then then time you lap speeds.    In ll the pnes I have they have a happy medium ffr each one for me.   

[Dan McEntee]

I have a Super Clown with a .25fp running a 9X6 prop on 60' lines. It's running sub 5 second laps. I want to slow it down to a 5.3 to 5.5 second lap. Any advice on prop diameter and pitch?

   If you are flying on 60 foot eye to eye lines, try a set of lines that are 2 feet longer and keep your current engine settings, and get an accurate lap time. For that airplane, as it has been stated, you may not be able to slow it down with the needle to a 5 + second lap and still have the airplane perform like it should. If the engine sounds happy and you are in the 4.8 second range or so or even a but less, try 2 foot longer lines. The model will still be flying at a speed it needs, and the engine will still be happy but you will be turning slower for more comfort. Experiment from there. Try different props and such, but since you are just simply flying around with an occasional loop, prop won't be too critical, but you can at least get some experience in seeing how different props run on the same engine. All props are not equal even if they are the same diameter and pitch. You won't know how they work until you try it.

   Have fun,
   Dan McEntee

[Tim Wescott]

I am still convinced that lap times are over rated.  Fly the airplane at the speed it is happiest at.  Then when you are satisfied after a half dozen flights, then then time you lap speeds.    In ll the pnes I have they have a happy medium ffr each one for me.   

Well, yes but with caution.  If you're flying something on 60 foot lines and the slowest it'll be happy with is 4.75 second laps, then chances are it's a dog and you're papering over all sorts of trim problems with the extra centrifugal force (or, it's a Ringmaster and it's acting as expected).  Ditto 5.1 or 5.2 second lap times on 70 foot lines.

It may not be optimal, but when I'm trimming a plane I do try to bring the lap times down to or below what's considered sensible for that line length, then try my darnedest to get the plane happy at that speed.  Then I bump the speed up a bit to make sure it'll still be happy in a wind or if I have a bad engine run or whatever.