Do I Have this Trimming Stuff Right?

[Tim Wescott]

The Waiex flies.  I got a tank problem sorted out.  It flies a good long time, with a good steady run, so now it's down to getting plane and pilot good enough to fly the beginner pattern.

Right now the plane seems to fly OK upright and in the inside maneuvers.  Flying outside maneuvers makes me lose line tension, flying inverted or outside maneuvers makes the engine sag.

So it seems that the first thing I want to do is to shim the tank up, to see if I can get it to run the same upright and inverted.  It's running a rich two-cycle on an OS 25S, so I take that to mean that it's running richer inverted.  And if I'm doing the visualization right, shimming the tank up should make it lower when things are inverted, and make it not richen up so much.

I'm not so sure about the second thing.  Assuming that getting the engine running nicely inverted doesn't help, what do I do and/or check about the problem with losing line tension on the inverted maneuvers?  I noted that the plane seems to lean in to the center of the circle when flying upright, but (dang it!) I did not check to see how it does when flying inverted.

Should I just tweak the flaps for a bit of roll to the outside while inverted, then correct any lack of line tension with tip weight?  Is there some other measure I should take, or some other thing I should check before I do anything?

Right now I can't do the outside maneuvers with confidence, and I want to at least be able to do something come Sunday at Salem.

[W.D. Roland]

Tim
I am close to same confusion boat....
Will help where possible.
Turn it into a 100mph combat plane, then it wont care and will fly perfect.

Going rich on outsides could be line tension problem.
Shimming tank up( toward top of airplane right side up) or tank vent. If top and bottom vented non uniflow fuel tubing cut at angle slipped over vents and the turned into and or out of slip stream can work.

If that does not cure outside line tension look for warp, remove, if no warp seen tweak flaps.
On my Chipmunk the flaps would not cure but tweaking the elevator did cure same problem.

Might add a little wing tip weight.

That's as far as I can go here and Expert help is now needed!

David

[Bob Whitely]

Tim, If the engine goes rich inverted raise the tank. If it is sagging or over lean inverted lower the tank.

Next you must get the plane flying level both ways. This is a real thing to get right.

Put in more tip weight til the outboard wing drops in the maneuvers both inside and outside
and then remove just enough to stop the wing drop.

Balance the plane at 25% at the root to start.

Put the leadouts 1" behind the balance point at the tip.

Make sure you have some outthrust on the engine.

Use just a little downthrust, about a degree.

Start with one to one controls and adjust from there.
You will need to do all these before the next flight.  RJ

[Tim Wescott]

Tim, If the engine goes rich inverted raise the tank. If it is sagging or over lean inverted lower the tank.

OK, I got that right

Next you must get the plane flying level both ways. This is a real thing to get right.

Put in more tip weight til the outboard wing drops in the maneuvers both inside and outside
and then remove just enough to stop the wing drop.

But if I get the engine running consistently upright and inverted, and get nice level wings upright but not inverted, don't I want to deal with that?

(This is a bit of a challenge, because my flying partners are all RC guys, so asking them to look for level wings is a bit hard).

Balance the plane at 25% at the root to start.

Put the leadouts 1" behind the balance point at the tip.

My leadouts are farther forward than that -- I will fix.  The balance point is about where you say, and the plane seems to fly just about right as far as fore/aft stability and responsiveness.

Make sure you have some outthrust on the engine.

Use just a little downthrust, about a degree.

Start with one to one controls and adjust from there.
You will need to do all these before the next flight.  RJ

I don't have any out thrust, or down thrust -- I'll address this.

[Bob Johnson]

I might help to know your line length and lap time. These will effect line tension. i.e. lines too long, flight too slow, poor line tension. A 5 sec. lap time should be a good starting place with 58 to 62 foot lines (eye to eye). Hope this is helpful.

Bob

[Tim Wescott]

I might help to know your line length and lap time. These will effect line tension. i.e. lines too long, flight too slow, poor line tension. A 5 sec. lap time should be a good starting place with 58 to 62 foot lines (eye to eye). Hope this is helpful.

I am thrashing so hard on getting to Salem that I am flying on a set of lines that are just 50 feet eye to eye -- which makes any line tension problems all the more ominous.  I may be able to get a set put together for Salem, but it may not be wise to use them!

[Bob Johnson]

So what are your lap times and/or motor rpm? I'm thinking on 50 ft. lines your lap time would be around 4.2 sec. to have enough  speed for stunting (a bit fast for my taste). Rpm should be around 9000 for a lean 4 stroke. What size prop are you using? 9 x 5 or 10 x 5 might be a good starting point. Other variables will also figure in. Please keep us posted.

Bob

[Tim Wescott]

So what are your lap times and/or motor rpm? I'm thinking on 50 ft. lines your lap time would be around 4.2 sec. to have enough  speed for stunting (a bit fast for my taste). Rpm should be around 9000 for a lean 4 stroke. What size prop are you using? 9 x 5 or 10 x 5 might be a good starting point. Other variables will also figure in. Please keep us posted.

I need a tach!

I haven't had a chance to time the laps -- they're long enough that I'm not feeling crowded, but not so much that I'm bored.  That's probably exactly no help at all, particularly because I think there's a bit more speed to be had from the motor (and I think I need it).

[Bob Johnson]

OK, are you running sloppy rich, a fast 4 cycle, wet 2 cycle, on the break? your best guess? What size and make prop?

[Brett Buck]

I need a tach!

I haven't had a chance to time the laps -- they're long enough that I'm not feeling crowded, but not so much that I'm bored.  That's probably exactly no help at all, particularly because I think there's a bit more speed to be had from the motor (and I think I need it).

Several obvious things
    get the engine running the same upright and inverted - shim the tank up to speed up inverted, down to slow down inverted
    once you get the engine running evenly, if it's different on insides than outsides, tweak the flaps until it has equal line tension both ways.  If it has more tension upright than inverted, tweak the outboard flap down, if it's more inverted than upright, tweak the outboard flap up.
    Ensure you have enough tipweight. Just add 1/4 ounce at a time until it starts having obvious problems in square corners. Too much tipweight will increase the tension at the expense of "hinging" (right roll on insides (see the bottom of the airplane), left roll on outsides (see the top of the airplane)) but until you get everything else sorted out you can't get in too much trouble with excess tipweight.
    Time your laps, or get someone else to, and ensure you are not going too slowly. A 25s probably likes a 9-6 or 9-6 cut to 8.5, and you should have it in a wet two-stroke in level flight. On super-short lines, if you are above about 4 seconds a lap you are probably too slow.

    Note that external observers are invaluable for this sort of thing. I think I mentioned this before, but you really need to seek out someone with some experience to fly with, particularly in the trimming process.

    Brett

[Tim Wescott]

OK, are you running sloppy rich, a fast 4 cycle, wet 2 cycle, on the break? your best guess? What size and make prop?

On the break, I think.  I'm running a 10-4 Master Airscrew, with a same-size Graupner 10-4 in the wings, as well as some 9-5 Top Flight wood props.  Once I get things at least basically working I'm going to experiment with props to see what seems to fit best.

Several obvious things
    get the engine running the same upright and inverted - shim the tank up to speed up inverted, down to slow down inverted
    once you get the engine running evenly, if it's different on insides than outsides, tweak the flaps until it has equal line tension both ways.  If it has more tension upright than inverted, tweak the outboard flap down, if it's more inverted than upright, tweak the outboard flap up.
    Ensure you have enough tipweight. Just add 1/4 ounce at a time until it starts having obvious problems in square corners. Too much tipweight will increase the tension at the expense of "hinging" (right roll on insides (see the bottom of the airplane), left roll on outsides (see the top of the airplane)) but until you get everything else sorted out you can't get in too much trouble with excess tipweight.
    Time your laps, or get someone else to, and ensure you are not going too slowly. A 25s probably likes a 9-6 or 9-6 cut to 8.5, and you should have it in a wet two-stroke in level flight. On super-short lines, if you are above about 4 seconds a lap you are probably too slow.

    Note that external observers are invaluable for this sort of thing. I think I mentioned this before, but you really need to seek out someone with some experience to fly with, particularly in the trimming process.

I know I need live help, the problem is shaking enough time loose to make it happen.  In the mean time I'm going to do what I can with what I have rather than moping around wishing for something that isn't going to happen.  Then when I do get some help, I'll have maximum leverage.

[Kim Mortimore]

I would like to add that it would be good to check for stab tilt when viewing the plane from the front, and viewed from the top, make sure that the flap hinge line and elevator hinge line are exactly parallel by measuring the distances from the elevator hinge line at each elevator tip straight forward to the flap hinge line to see if the two distances are equal.  You said, "....the problem with losing line tension on the inverted maneuvers....I noted that the plane seems to lean in to the center of the circle when flying upright...."  These together sound to me like a possible combination of problems, one of which might be a structural misalignment. 

It may be that the best thing you can get out of going to Salem Sunday is to ask for advice from an experienced stunt flier there.  That would definitely be doing "something" as you say.  I wouldn't sweat the Beginner event too much at this point.  Hope this helps.  Keep us posted on your progress.  There are plenty of Stunt Hangarites who can also benefit from your experience.

[Tim Wescott]

I would like to add that it would be good to check for stab tilt when viewing the plane from the front, and viewed from the top, make sure that the flap hinge line and elevator hinge line are exactly parallel by measuring the distances from the elevator hinge line at each elevator tip straight forward to the flap hinge line to see if the two distances are equal.  You said, "....the problem with losing line tension on the inverted maneuvers....I noted that the plane seems to lean in to the center of the circle when flying upright...."  These together sound to me like a possible combination of problems, one of which might be a structural misalignment. 

I made my life difficult by building a v tail (but it's purty).  I did assemble it with even angles between the V and the wing -- if I got it right.

It may be that the best thing you can get out of going to Salem Sunday is to ask for advice from an experienced stunt flier there.  That would definitely be doing "something" as you say.  I wouldn't sweat the Beginner event too much at this point.  Hope this helps.  Keep us posted on your progress.  There are plenty of Stunt Hangarites who can also benefit from your experience.

I'm actually hoping to get some pick-up coaching from Salem, as well as whatever I get from actually competing in the beginner's pattern.

[Tim Wescott]

Note that external observers are invaluable for this sort of thing. I think I mentioned this before, but you really need to seek out someone with some experience to fly with, particularly in the trimming process.

Which reminds me:

If there's someone out there who's closer to Estacada, OR than either McMinnville or North Portland, who doesn't mind flying off of grass, and who wants some congenial (and maybe even grateful) company flying control line -- c'mon down!  We're mowing this great big control line circle for two guys, one of whom only has 1/2A stuff (but with a .19 sized plane in the works), we need more folk to populate it.  You'll certainly get flying time.

[W.D. Roland]

Tim
When timing laps  do times for 5+ laps and then divide by laps timed for 1 lap times.

Makes starting and stopping the clock error less.

If timming it yourself use a tree or light pole or something for marker.

If someone outside the circle times use you for the marker(Marker = start/finish line)

David

[Randy Powell]

Tim,

I'll be at Salem by 12:00 noon or so on Saturday. I'll be glad to take a look. Others will be there to help too.

[Tim Wescott]

I'll be at Salem by 12:00 noon or so on Saturday. I'll be glad to take a look. Others will be there to help too.

If I am really really lucky with my family commitments (or really insensitive) then I'll be able to drop a kid off in Portland at 1:30 and head down to Salem.  If not, I'll only make it there on Sunday, more's the pity.

But getting there Sunday morning, with bells on, is my goal.

[Kim Mortimore]

I made my life difficult by building a v tail....

The technical term "eegad" springs to mind.  Even more alignment parameters to get right.  Also free, smooth control movement can be an issue with the more complex elevator horn setup.  A friend of mine built a v tail, and when he first put it together, the elevators wanted to spring back to neutral from one direction (can't remember if it was from Up or Down).  Here's an idea for a new contest trophy:  the Glutton for Punishment award.   

I was thinking Salem, Mass.  Salem, Oregon should provide you with oodles of major league expert help.  Now I'm really curious how it turns out.  Happy trimming!

[Tim Wescott]

The technical term "eegad" springs to mind.  Even more alignment parameters to get right.  Also free, smooth control movement can be an issue with the more complex elevator horn setup.  A friend of mine built a v tail, and when he first put it together, the elevators wanted to spring back to neutral from one direction (can't remember if it was from Up or Down).  Here's an idea for a new contest trophy:  the Glutton for Punishment award.

But it just looks so nice.  Besides, I was modeling a Waiex, and a Waiex has a V (actually a Y) tail.  So I'm just stuck*.

It's not too bad -- it's got lucky boxes that are as free moving as any other control horn that I've used, and you verify alignment by putting a stick across the tips of the V.

I was thinking Salem, Mass.  Salem, Oregon should provide you with oodles of major league expert help.  Now I'm really curious how it turns out.  Happy trimming!

Or Salem, Alabama, or one of the two (!) Salems in Arkansas, or Salem, Connecticut, or Salem, Florida or one of the other 30 or so Salems that I counted on Wikipedia: http://en.wikipedia.org/wiki/Salem.

* Modeling a Sonex would be right out, of course.

[john e. holliday]

Hey, it sounds like you are having too much fun with this plane.  Just don't rush it and bruise the grass.

[Tim Wescott]

Hey, it sounds like you are having too much fun with this plane.  Just don't rush it and bruise the grass.

I flew again today, leaving the grass unbruised but for a few wheel marks.  It looks like I'll be making it down to Salem tomorrow, unless I come down with the kids' cold in full force or it's raining full force when I get up.

It does about four second laps on 50' lines.  I know those are short lines, but it's what I have now and the contest is tomorrow -- so I'll fly there with the short lines, and I'll be experimenting with longer lines (and a different handle) afterward.  The motor runs consistently, and the same upright and inverted.  The plane has good line tension upright and inverted -- I think most of my loose lines when inverted problem was due to the engine sagging, but I suspect I'm masking a differential bank angle between upright and inverted with tip weight and leadout position.

So -- yippee!  I can even get through most of the beginner's pattern, although I bailed out of the horizontal eight due to low tension as a consequence of really bad flying, and I didn't even try an overhead eight -- one thing at a time here!

[Kim Mortimore]

You can fake overhead 8s by flying more horizontal 8s, just as much higher as you are comfortable with, and get at least a few points, maybe more if they are using pattern points there as they are here.

[Tim Wescott]

Even if I don't do that tomorrow (I'm coming down with this cold, and may not even attempt the horizontal eights) it sounds like an excellent way to sneak up on the overhead eight in practice.

[Russell Shaffer]

Tim, the weather won't be too bad.  Just clouds and maybe some drizzle, so come on down.  We had a good day today with only one minor crash (mine) and everyone had a good time.  Come on down, be here by 9:00 to sign up.  It's a great experience and you will learn a lot and have a good time. There should be two other beginners and maybe three intermediates plus the more advanced fliers in the higher classes. Russell

[Bob Reeves]

Several obvious things
    get the engine running the same upright and inverted - shim the tank up to speed up inverted, down to slow down inverted
    once you get the engine running evenly, if it's different on insides than outsides, tweak the flaps until it has equal line tension both ways.  If it has more tension upright than inverted, tweak the outboard flap down, if it's more inverted than upright, tweak the outboard flap up.
    Ensure you have enough tipweight. Just add 1/4 ounce at a time until it starts having obvious problems in square corners. Too much tipweight will increase the tension at the expense of "hinging" (right roll on insides (see the bottom of the airplane), left roll on outsides (see the top of the airplane)) but until you get everything else sorted out you can't get in too much trouble with excess tipweight.
    Time your laps, or get someone else to, and ensure you are not going too slowly. A 25s probably likes a 9-6 or 9-6 cut to 8.5, and you should have it in a wet two-stroke in level flight. On super-short lines, if you are above about 4 seconds a lap you are probably too slow.

    Note that external observers are invaluable for this sort of thing. I think I mentioned this before, but you really need to seek out someone with some experience to fly with, particularly in the trimming process.

    Brett

There are some jewels in this that many need to print and keep in the flight box.

[Tim Wescott]

Last week the mantra was: "it's good enough, don't mess with it until after Salem".

This week the mantra is: "darn this weather".

I knew I was a little tail heavy at Salem, but it was good enough and I didn't want to mess with it.  And the lines were way too short (and heavy), but it was good enough and I didn't want to mess with it.  I think the engine was too fast, but it was good enough and I didn't want to mess with it (etc.).

Last night I bolted a 1.4oz weight on at the bottom motor mount screws under the muffler, and made up a set of .015 x 58' lines ('cause I can shorten them if they're too long, but it's more of a challenge to un-shorten them).  I got to the flying field this morning to be greeted by high gusty winds and even the bravest of the RC guys sitting around talking and drinking coffee.  So I sat around and talked for a while, and when the wind died down a bit I went out and managed one flight.  The weather report is for rain this weekend .

I should have given one of the idlers my stop watch, but I didn't think of it until it was too late.  I counted lap times of around four seconds, but that's probably anywhere between 3.8 and 4.5.  As near as I can tell I've smoothed the level flight out considerably (as well as I could tell when the plane wasn't being smacked by the wind).  I did a few vertical climbs, and a wingover, and the plane seemed to be handling well.  I didn't want to push things between my cold and the wind, so I left it at that -- I don't know I would have been able to tell if a shaky loop was my problem or the wind's, but smacking into the ground is always pilot error if you're the one who decided to stunt.  So that's what I know.

What sort of lap times should I be looking for with a 405 square inch plane, 35oz empty weight, on 58' lines (about 60' from handle to fuse center)?  I gather that four seconds is really too fast, and the engine will slow down nicely if I richen it up.

Note: 9 x 5 prop, it's running in the neighborhood of 11000 RPM, probably a tad less.  I tached it at 11000 on a 10 x 4, but I need to head down to the LHS and get a handful of those...

[Mark Scarborough]

Tim,
I would really encourage you to try the APC 10x4, probably around 10600 or 10700 rpm. your lap times should be knocking right around 5 seconds or so, a bit faster wont be horrible, but with that cute little bugger of yours, I dont think I would want to see it any slower than 5.0.
Glad you didnt hurt it when you pancaked it at Salem, it was great chatting cars, and airplanes with you. Look forward to more of the same next spring at a contest near you,,

[Tim Wescott]

My LHS carries APC and at a reasonable price.  The 9 x 5 woods are left overs from an RC plane I have (as was the Master Airscrew that was on it when I showed up).  So I'll get a handful of APCs and get them balanced up -- they're a nice prop.

At least one person mentioned how cramped my pattern was on Sunday.  What little flying I did today with the longer lines certainly felt much less crowded and nicer from inside the circle, and I got a nice comment from one of the RC guys who flew CL in his youth.

So I'm keeping my fingers crossed and hoping I get some flying time in between now and next June!!

[Randy Cuberly]

(SNIP)
[So I'm keeping my fingers crossed and hoping I get some flying time in between now and next June!!
[/quote]

Tim...You want to get some flying between now and June, move to Tucson.  In the "winter" we can usually fly all day every day while most of the country is buried in snow.
In the summer it's a little more limited.  We can only fly about 3-4 hours every day (early morning) then it's too hot!
You want help?...We have 4 past Nationals Champions here.  And a lot of "Good" guys.

Randy Cuberly

[Tim Wescott]

There were Wescotts in Clackamas or Multnomah county since at least 1927, AFAIK the Elliots came in when the trains came through after the civil war, but there've been Bohnas around here since the 1840's.

So I think I'll stick around.

[Brett Buck]

Tim,
I would really encourage you to try the APC 10x4, probably around 10600 or 10700 rpm. your lap times should be knocking right around 5 seconds or so, a bit faster wont be horrible, but with that cute little bugger of yours, I dont think I would want to see it any slower than 5.0.
Glad you didnt hurt it when you pancaked it at Salem, it was great chatting cars, and airplanes with you. Look forward to more of the same next spring at a contest near you,,

  Wow, a 10-4 seems like A LOT too much for this engine. This is not an FP, it's a 25S. Short of 40% nitro, I can't see it making it to the necessary RPM, and if it does, it will likely break the crank, like mine did.

     Brett

[Mark Scarborough]

Brett,
My bad, I thought he had an FP on it when I saw it in Salem, yes you are most likely right on the 10-4 being to much for his motor,, now and LA 25 or FP would be fine IMHO

[Tim Wescott]

You worry me.  Unless my new Hangar 9 tach is lying to me it was turning a 10x4 prop at somewhere around 10500 in my driveway when I was adjusting the tank level.  That's on about 15% nitro fuel.  The only thing that's not stock about the engine is that I turned the venturi myself, and I know it's a bit bigger than the recommended area of displacement x .045/inch.  But it's drawing fuel just fine with no pressure and with just a slight change in engine behavior between nose level and nose up.

I'll keep my fingers crossed, and hope I don't break the crank!

Could this be a different engine than what you're thinking of?  This is the 25 that OS sold in the early 80's as the "OS Max 25" (no "S" in the name from OS), and if it makes any difference it's an RC engine that I've made a venturi and spraybar for -- this is not an engine that came from OS intended for CL.  

And it's not some strange fluke, either -- I've got two of them.  The other one is clapped out with little compression and won't run through a tank, but when it is running it runs as strong as this one.

[Brett Buck]

You worry me.  Unless my new Hangar 9 tach is lying to me it was turning a 10x4 prop at somewhere around 10500 in my driveway when I was adjusting the tank level.  That's on about 15% nitro fuel.  The only thing that's not stock about the engine is that I turned the venturi myself, and I know it's a bit bigger than the recommended area of displacement x .045/inch.  But it's drawing fuel just fine with no pressure and with just a slight change in engine behavior between nose level and nose up.

     I am sure it can turn it, it's a matter of how close to the edge it will have to be. I am pretty sure mine could turn the prop that fast but there's no breathing room and I would expect it to feel like a dead fish in the air. A 25fp, for instance, would be pretty deep in a 4-stroke at that speed on that prop and fuel.

     Please post a picture of the engine so we are sure we know what we are dealing with.

     Brett

[Tim Wescott]

I am sure it can turn it, it's a matter of how close to the edge it will have to be. I am pretty sure mine could turn the prop that fast but there's no breathing room and I would expect it to feel like a dead fish in the air. A 25fp, for instance, would be pretty deep in a 4-stroke at that speed on that prop and fuel.

That's the difference, then -- at that speed it's pretty close to topped out.  But it also does four second laps with a 9x5 and 58 foot lines, so maybe there's room to slow it down to five second laps & see how it goes.

There's a picture in the plane in Flying Lines that shows the engine: http://flyinglines.org/Follies.10.html, and I've attached a couple more.  None were taken with the intent to really show the engine, but it says "OS Max" on the side, with "25" in a circle underneath.

[Brett Buck]

That's the difference, then -- at that speed it's pretty close to topped out.  But it also does four second laps with a 9x5 and 58 foot lines, so maybe there's room to slow it down to five second laps & see how it goes.

There's a picture in the plane in Flying Lines that shows the engine: http://flyinglines.org/Follies.10.html, and I've attached a couple more.  None were taken with the intent to really show the engine, but it says "OS Max" on the side, with "25" in a circle underneath.

   That's the engine I thought it was. A 25S that was first available in the early 70's (which is about when I got mine). There's no way that's going to work well with a 10-4. As mentioned before, try 9-6, maybe cut down a bit, or at most a 9-5. Shoot for laps around 4-4.2 seconds on the short lines. Don't bother trying to go any slower because it will have significant line tension issues, particularly when you start trying vertical or overheard maneuvers. Or go get a 25LA, which I think will be a far more satisfactory powerplant for this size airplane.

The only airplane I ever designed for this engine was around 350 squares, and about 20-25 ounces. It was also the first airplane I designed, but it worked pretty well as far as I could tell at the time. And it still looks about right to me even 35 years and about 20,000 flights later. Some of the design decisions were merely lucky accidents, of course, since I really didn't know what I was doing.

     Brett