Flow chart for engine set up and prop ch

I have been thinking of doing such a chart and wondered if one has not been done. Just like PW's flight trim flow chart there is a definate procedure, flow chart if you will, that is used when I set up a plane and engine combination. I am thinking of doing one for Stunt News but feel that maybe Ted and Brett might articulate it better. How bout it Ted, Bret?

Ya, do it..

Maverick,
I have to agree with Bob Reeves, go for it...I think that would be some interesting information, and good reading......
Gil

Rich,

Oh, Yes, Yes, Yes, especially differences between windy and calm weather!!!

Now Guys you did read the part about Brett and Ted didn't you? I have been planning on doing it and just thought they would probably have something already in their heads that they could pen. Ted is such a good wordsmith that I would think he could get it much clearer than I could. I also thought I might do a video. I will get to work on the chart though.
RO

Wow, great idea. Between you, Ted, Brett, and other "gurus", I'm sure the info would be very helpful and appreciated. Makes me wonder why it wasn't thought of before. Is there anything I could do to help (besides staying out of it?)

Christ, Of course you can help. Your experience in how you do it can broaden the info to the chart as long as it is not redundant. Your definitions may suit the condition better than mine. The idea is to build the chart with flying experience and knowledge, not who is doing it.
RO

>Christ, Of course you can help. Your experience in how you
>do it can broaden the info to the chart as long as it is not
>redundant. Your definitions may suit the condition better
>than mine. The idea is to build the chart with flying
>experience and knowledge, not who is doing it.
>RO

Richard,
I'll take a stab at putting something down with what I know. then we'll go from there.

>I have been thinking of doing such a chart and wondered if
>one has not been done. Just like PW's flight trim flow chart
>there is a definate procedure, flow chart if you will, that
>is used when I set up a plane and engine combination. I am
>thinking of doing one for Stunt News but feel that maybe Ted
>and Brett might articulate it better. How bout it Ted, Bret?

I can't speak for Ted, but I don't know that I have it down to a flowchart level of detail. There's so many ways you could go, depending on the desired result, that I really don't know how I would go about describing it. I usually get what I want, in the end, but I couldn't say it's as algorithmic as one might like.

If you have a way, then by all means, go ahead.

Brett, It can be described more as a ritual than flow chart but the thought process is the same. I fly many different designs and engine combinations regularly and find myself going through this ritual every time with a new subject. Based on weight, size, and power there is a finite set of things that seem to work. Some times it is a search for a close to what is needed prop off the shelf or making one from available carbon props that can be tweaked. As you stated fuel becomes the next level, or one of, that is in the mix. Engine tuning is also in the mix which changes the other parameters, ergo the flow chart. If you are trying to run your engine in a style(4-2-4)this is also one of the starting points. I know I even do this on the day of a contest to a lesser degree to determine the right set up for the conditions. Wind, humidity, temp, air density all play a role. I see your group do the same at the nats when trying to get the set-up that suits the day and location.
RO

Richard,

I think you would be an excellent candidate to do a chart. You get to fly more than just about anyone out there. So you can put together a test subjec and run it through the chart. Then do the same with the another setup. You also have acess to many different engines and sizes. So going through the displacements and seeing if your charts plays out to each size engine.

Rich,

Off the top of my head I feel much like Brett on this subject. I've never really tried to narrow my thought processes to just the prop. All the other variables go into most of my decisions. This might be in large because I seriously limit my props (for "serious" projects) to a very narrow range of props with which I am intimately familiar. Thus, while making no disparaging remarks about other types, I work almost exclusively with Brian Eather's. I use just two basic types (now quickly being reduced to one) the flat back green three bladers and the UCT red ones.

This is almost a complete surrender on my part to the reality that props are sooooo different and the effects soooo varied that it probably isn't a good idea for someone who doesn't fly a whole lot to even get into the possibilities.

I know for a fact that these basic prop formats fly my designs exceptionally well. I know I can adjust almost exclusively the pitch on the basic blade to produce a change in performance in a predictable fashion. I will on occasion play with prop diameters but, with the PAs and RoJetts, I have never run up against a horsepower limitation that effects my propeller decision. Of course, like Brett I've never gone in search of a prop which would challenge the potential of these fine engines; preferring instead to run well within their capabilities. (Important to note that such is not the case with most engines in the classic range although the Aero Tiger is probably the closest thing to capable of any prop you would reasonably want to put on it).

Prop selection is first a foremost based on the engine and its capabilities. Gone are the days when we routinely stuck on a 10 X 6 Top Flite paddle blade and went flying for better or worse. It can still be an appropriate choice if running classic era engines like Foxes, K and Bs, OS S's, Johnsons etc., but, with modern engine they are less common and sometimes not even a very good choice.

If you're using a "modern" schnerle ported engine originally intended for use by our RC brethren it is almost certainly a better choice to go with the lower pitch props and allow the engine to rev up closer to its design power range. This has been discussed to death and probably doesn't need further amplification. I mention it only to make it clear that the appropriate prop is going to depend first and foremost on the engine that spins it and what that engines best operating RPM range is for our purposes.

Classic cross scavenged engines, on the other hand, are less comfortable spinning fast enough and might well be far beyond their power and torque peaks even if you can force them fast enough to fly a lap time you like. The bottom line with such a combination will be the desired lap time but tension and performance that feels gutless.

The trick is to find a basic prop that produces acceptable lap times at a point only slightly past its torque peak (and yes, you've got to be willing to juggle line length sometimes to balance torque peak, lap times and best prop). Roughly speaking that will be an engine that isn't strained to turn 10 to 11K for the modern iron spinning a prop of nominal four inches of pitch. (I'm less conversant on revs for the classics since I've always set them by ear ... the greater pitch required for proper operation with these engines makes them less critical of precisely the right revs.)

Once you've found an engine/pitch combination that allows unstrained level flight laps you like, adjusting the diameter will allow you to load and unload the engine to help adjust the ultimate performance in maneuvers ... technically, I suppose, helping you find the sweet spot on the torque curve that gives appropriate torque increase under load. IOW, if you spin essentially "suitable" props for an airframe at a given RPM, a larger or smaller prop of the same pitch at the same RPM will produce pretty much the same lap times. What will change is the reaction of the engine/prop combo to loads as when we maneuver.(remember to stick with the same brand and style as well since, as we've discussed in other threads, pitch is an ephemeral thing that may mean one thing with one brand and another with a different brand)

THE FOLLOWING DISCUSSION ASSUMES AN ENGINE CONDITION SUITABLE FOR THE ATMOSPHERIC CONDITIONS AND AN AIRPLANE THAT IS AT LEAST RUDIMENTARILY WELL TRIMMED. PROPS WILL DO WONDERS FOR SUCH AN AIRFRAME/ENGINE COMBO BUT CANNOT TRANSFORM YOUR PIG'S AURAL ORIFICES INTO GOSSAMER COIN RECEPTACLES ... OR SOMETHING LIKE THAT. IT IS ALSO TRUE THAT MANY ENGINE PARAMETERS WILL HAVE AN EFFECT ON THE PERFORMANCE PARAMETERS WE'LL DISCUSS. TOO DEEP A SUBJECT FOR THIS SPACE BUT, HECK, THAT'S WHAT YOU'LL GET WHEN YOU GET THE SECRET HANDSHAKE AND THE EXPERT PATCH!

First of all, do NOT start by determining what lap time is acceptable to you. What's acceptable to you is a secondary consideration. Much more important is to find the airspeed the airplane/engine/prop combination is happiest with. Once you've found that happy circumstance you can fiddle a bit with line length but remember, keep the airplane happy before you try to please preset expectations of the pilot.

For pilot's that are not yet expert I encourage you to find a way to be happy with lap times around five second or so a lap. Trimming an airplane to fly well at such speeds is monumentally easier than at the "fadishily popular" 5.5+ laps we all hear about. Up to you, but you can take it too the bank that you are making your flying life more difficult!

Once you've found, by trial and error under good conditions, the prop that produces the response you care for in maneuvers, use that prop as a standard from which you deviate in response to conditions. Specifically, you want a combination that produces consistent tension through the maneuvers to the greatest degree possible. Consistent tension is a sure tattle tail of consistent airspeed which, in turn, says you are operating on the down side of the torque curve so that when you load the prop thus trying to drive down the RPM the torque increases thus mitigating or limiting the rev drop and resultant speed loss.

If the airplane bogs down in maneuvers, loses speed and tension, consider reducing the diameter a quarter inch or so (total) at a time, readjusting the launch revs to retain revs appropriate for the desired lap times. This reduces the torque required to turn the prop and moves you further to the right on the torque curve. Thus, when you load the engine the next flight you should get a more positive response as the revs drop a little and the resulting torque increases.

Continue cutting and flying until you get no further improvment. If performance in maneuvers is still unsatisfactory you are probably trying to get too much out of the engine rev wise and will have to try a series of props with more pitch. Again, if possible use the same brand and style of prop. Although a bit of a pain the absolute best way to play the prop game is with carbon fibre or glass props that can be repitched with hot water and a pitch gauge. This way you can use the identical prop for your experiments and know that the chnange in performance is the result of the changes you made to the prop. That is a huge asset when searching for the exact prop you need.

More later, dinner is about ready and I've got to open the wine.

Let me know if this is going to be helpful or if you get lost in the verbiage.

Well, I snatched/copied/gobbled-up this reply before the pixels were dry.

Thanks, and please keep it coming, Ted. By all means, enjoy the wine.

Great thread and great idea, Richard. Thank you too!

LAST EDITED ON Feb-04-04 AT 00:33 AM (CDT)
 
I think Ted is somewhat building the flow chart now! I think if the subject was discussed in a round table type situation one could definitely be drafted. I, unlike Ted, have not settled on only one brand and like testing as an excuse to burn more fuel. I have boxes(large) of props of all types and more ordered and more to be ordered. I have tried all types of engine set up's on all kinds of planes with the whole spectrum of weights. I seem to go through the same ritual every time to find the right set up and prop choice for the plane and engine combination being flown. Sometimes I hit it early and sometimes... well some of them I am still looking for! Since I produce engines for all types of flying I feel I should at least be able to point my customer in the right direction. My friends here look at sideways when they see me flying a profile as if I am wasting my time not practicing for the Nat's, but for me it is a fact finding session as much as anything. I was glad to have Dale Gleason down here for a few days, with his new plane and engine, so I could work him and try some things out on his plane and be outside the circle for a change. He got tired and left to early, darn it!
I will start compiling data and try to formulate a chart.
RO

"....got tired and left to (sic) early?" I thought we quit because Dee's car broke down! Well, I WAS too tired to shag Dee's golf balls. I think a "flow" type chart would be a great help for most flyers. Not being well versed in the "cause-result" aspects of tethered flight, I, for one, could use a little direction to avoid going down so many wrong roads. It could be a flow chart for a "generic" east coast/west coast all inclusive plane and once that was figured out, the knowledge gained could be applied to more specific planes with different design philosophies. Best regards, dale gleason, an English teacher endeavoring to become a wordsmith

Ted, I'm curious as to why the 5 second lap time would facilitate becoming an Expert. Would that apply to an older retired type whose reflexes are on the wane? Let's see now, you actually said the plane would be easier to trim. I can sorta' see that but I'm seeming to be gaining on it with my new "Impcat" with the pipe and all- but I'm most happy at 5.7- 5.8. Or rather I should say, the plane seems happier at that slower speed. This will all become moot as soon as I apply my new Fancher handle to the task. I used 4 coats of Sig clear with zinc stearate, one layer of Sig fibreglass cloth applied with Epoxy finish resin, then 4 coats Sig Fokker Red. Havn't buffed it out yet- it came in at just under two and a half oz. with lanyard and a thumb tack to tell "which way is up", a la the EZ-Just of yore. Very nice handle kit, by the way! Best to all,

>Ted, I'm curious as to why the 5 second lap time would
>facilitate becoming an Expert.

I really dont think so.

However the 5.0 lap was and is very hard for me to trim. Alot has to do with the design and how the model came out weight wise.

Dale I am with you. I have always had good luck as long as it was slower than 5.6. Even when many different people tell me the wing I am flying has to have a 5.2 or faster lap time to fly good...huh???

You cant really put a time on a design. All the times are really personal prefrence. I fully understand what Ted is saying about the 5 lap. There wont be any stalls or any funnys. The plane will be out there big time.

As long as the motor will put out the ponies get it as slow as possible without stalls or coners that fall out and the pattern will always be easier to really get precise. It is pretty much a fact. Trying to draw a loop fast or slow and the slow one will be rounder every time. As long as the motor is up to the task.

Brad's thread about high energy wings is a good one.

Always build it light.

>Ted, I'm curious as to why the 5 second lap time would
>facilitate becoming an Expert. Would that apply to an older
>retired type whose reflexes are on the wane? Let's see now,
>you actually said the plane would be easier to trim. I can
>sorta' see that but I'm seeming to be gaining on it with my
>new "Impcat" with the pipe and all- but I'm most happy at
>5.7- 5.8. Or rather I should say, the plane seems happier at
>that slower speed. This will all become moot as soon as I
>apply my new Fancher handle to the task. I used 4 coats of
>Sig clear with zinc stearate, one layer of Sig fibreglass
>cloth applied with Epoxy finish resin, then 4 coats Sig
>Fokker Red. Havn't buffed it out yet- it came in at just
>under two and a half oz. with lanyard and a thumb tack to
>tell "which way is up", a la the EZ-Just of yore. Very nice
>handle kit, by the way! Best to all,

Hi Dale,

Naw, I'm mostly aiming comments like that at the average guy who is flying his Twister or NoblerArf and has the mistaken notion the way to do it is at 5.5 second laps. By far the simpler approach is to fly at airspeeds that make tension and adequate stall margin non issues. Once you refine that condition and have a handle on what does what with all the components you can start a program to see if that happy circumstance can be extended without detriment to the handling qualitities of the airborne package.

Boy, your handle sounds a lot prettier than mine. Can't wait to see it with all the rivets and panel lines and after the clear coat is buffed. I assume your hat and belt will match?

Dale and Dougie,

I guess I needed to make it clear those comments weren't direct to accomplished stunters who already have a good grasp of trim and props and engines etc. Doug clearly doesn't need any help from me in that regard and I couldn't really help Dale all that much. You are both starting from a point much further along the bell curve than what my comments are directed at. Neither of you needed me to tell you what prop you needed to start out with on your state of the art ships and powerplants.

Gotta realize how far ahead of the game you are compared to probably the largest percentage of readers of SSW or Stunt News.
Ted

Ted,

I gotcha now. Sorry to intervene there. You are so very right about a twister or the likes. They need to scoot along pretty good. And a newer flyer would be much advised to get it going and not worry to much about the clock and all that stuff. You need all the speed needed to keep it tight in all spots to keep it safe.

Write on Ted, write on...I always like to read.

Thanks

>Ted,
>
>I gotcha now. Sorry to intervene there. You are so very
>right about a twister or the likes. They need to scoot
>along pretty good. And a newer flyer would be much advised
>to get it going and not worry to much about the clock and
>all that stuff. You need all the speed needed to keep it
>tight in all spots to keep it safe.
>
>Write on Ted, write on...I always like to read.
>
>Thanks
Shoot, doug.

No need to apologize. It should have been said up front.

Ted

P.s. Very nice evaluation on the WC/Billy/Randy/Al thread. Can't disagree with much if any of your analysis. I'll take another look at it later and maybe post some thoughts but I doubt if they'll be much different from what you posted already. Good work.

When I considered panel lines for my Fancher handle, I realised that they were a bit much. I'm going the "rivet" route on this baby! Thanks, Ted, for your timely reply re the lap times. I was almost ready to cut some cable. Speaking of which- I think that the power I'm experiencing with big RO Jetts and PAs negates the need for solids. With my ST 60 ship I needed every aid possible to help it out as it was quite portly. The solids have a deserved niche on Richard's flow chart, but they've proven to be quite a bother to me. Hope that didn't take the thread off on a tangent. Best regards,

>When I considered panel lines for my Fancher handle, I
>realised that they were a bit much. I'm going the "rivet"
>route on this baby! Thanks, Ted, for your timely reply re
>the lap times. I was almost ready to cut some cable.
>Speaking of which- I think that the power I'm experiencing
>with big RO Jetts and PAs negates the need for solids. With
>my ST 60 ship I needed every aid possible to help it out as
>it was quite portly. The solids have a deserved niche on
>Richard's flow chart, but they've proven to be quite a
>bother to me. Hope that didn't take the thread off on a
>tangent. Best regards,

Dale,

You may or may not have noticed that you'll not find solids on my airplanes either (with the exception of some of the Classic stuff I fly which is only because they were the only ones I had that were the length I wanted. Too lazy to make new cables for a handful of flights a year.

Someone of some prominance told me solids were the way to go but they were only good for 40 or fifty flights before needing replacing. Well, that would be a whole year on a set of lines at my old FOP (frequency of practise). However, I've seen RO's practise schedule and he would need a new set of lines every 1.5 days! He even retreads his tires every two weeks or so! So I guess that completes the torpedoing of this thread. But what else can one do on a dreary day such as this one- other than get on SSW? RO would go flying, of course, since it's a balmy 38 degrees! Best regards all,