Line Length?

[Tim Wescott]

Span: 48", tip-tip
Area: 410 squares
Weight: probably 36oz, 32 if I'm lucky (I won't be).
Engine: OS Max 25

Line length?

[Brett Buck]

Span: 48", tip-tip
Area: 410 squares
Weight: probably 36oz, 32 if I'm lucky (I won't be).
Engine: OS Max 25

   Start with .015x60 (presuming it's a 25FP or LA).

    Brett

[Tim Wescott]

Nah.  It's an OS plain ol' MAX, bought in the early '80s before my kids started consuming all my available discretionary money.

Steel sleeve, steel piston with a baffle, just your basic hunk of metal to turn a prop.

I was thinking 52 foot lines -- you still think 60 is the way to go even if the motor's a bit milder than you thought?

[john e. holliday]

You can always try the long lines and then cut to suit.  Just be careful how you fly the plane.   

[Tim Wescott]

Just be careful how you fly the plane.

It took me a couple of near-misses and outright crashes to realize that with control line you have to sneak up on the hard maneuvers -- i.e., don't try for a square corner that ends up 5' off the deck on your very first wingover.  For that matter, don't try a wingover directly overhead until you've done it at 45, then 60, then 75, etc.

With RC you just get really high and try things out, because if you recover ten or twenty feet lower than expected it's no big deal -- only if essential lifting surfaces break do you have a real problem.  With control line, you just don't have that margin.

[Bob Whitely]

No more than 60' center of handle to center of plane. Change it later if you think it is too short or too long.   This will help to keep from destroying the plane on the first or second flight. Too long is BAD, too short is only too fast.  Kinda like a nose heavy model will fly ok just a little sluggish.  A tail heavy plane will only fly once.  RJ

[Brett Buck]

Nah.  It's an OS plain ol' MAX, bought in the early '80s before my kids started consuming all my available discretionary money.

Steel sleeve, steel piston with a baffle, just your basic hunk of metal to turn a prop.

I was thinking 52 foot lines -- you still think 60 is the way to go even if the motor's a bit milder than you thought?

   I don't recall ever flying my 25-s engine models on lines that short. But you are asking an awful lot of that engine with that airplane. Those are the dimensions of the airplanes we have been flying with 20/25FPs, 25LAs, and Veco 19s. Any of those has A LOT more power.

    Brett

[Allan Perret]

I fly all my .25 size planes with .012 cables.  The plane you describe I would start with with 56'~58' lines.   60 feet would be max.   but sneak up on it..

[Leo Mehl]

   Start with .015x60 (presuming it's a 25FP or LA).

    Brett

why 15 I would use 12. I beleive 12 are legal now for a 25 size engine.

[Tim Wescott]

But you are asking an awful lot of that engine with that airplane. Those are the dimensions of the airplanes we have been flying with 20/25FPs, 25LAs, and Veco 19s. Any of those has A LOT more power.

Now you tell me!  That plane was practically designed on this forum!

We'll see how it does -- if worse comes to worst I have a 20 FP, and a Fox 35 for that matter.

[Jim Thomerson]

My Jr Flite Streak with TD 09 was too fast, 3.8 sec laps, on 55 ft eyelet to eyelet 012 lines.  I put it on 57's and got it slow enough I could fly it almost all the time, instead of just some of the time. 

[Brett Buck]

Now you tell me!  That plane was practically designed on this forum!

We'll see how it does -- if worse comes to worst I have a 20 FP, and a Fox 35 for that matter.

I mentioned something similar before - on November 2009:

  I would put even 400 at the very top end of the scale and only from a master modeler like Keith. The baffle-piston 25 is not a very strong engine at all by current standards, and I don't even think it's enough to provide good performance even on an ARF Flite Streak (which is darn light). The last airplane I had my 25-S on was a Shark 15, and it was a decent performer and not overpowered. I would suggest something a little larger than that with a similar (pretty thin) airfoil -maybe 325-350 square inches and as light as you can make it.

    I may be wrong but I am consistent

   The good news is that you have designed a pretty good 25LA airplane.

   Brett
  

[Tim Wescott]

I mentioned something similar before - on November 2009:

Oops -- my bad.

We'll see how it does.  If it ends up a hanger queen -- it's still a nice looking aircraft!

[Brett Buck]

Oops -- my bad.

We'll see how it does.  If it ends up a hanger queen -- it's still a nice looking aircraft!

  No hangar queen- easily solved for $75:

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXPUE2&P=FR

    Brett
 

[Chucky]

For top performance, I'd go for 58' .012 lines to minimize drag.  Just take care of them as they are more fragile than .015's.

[SteveMoon]

That's a sweet looking plane. Plans?!?!? I would think about 55' lines if you're
using .015s and maybe 58' lines if you go with .012. I started flying my TT36 powered
G Noblers with 60 x .015 lines and it was a bit sluggish. Bob G told me to go to
59' lines, and it came alive. That's why I'm thinking around 55' if you go with .015s.

Later, Steve

[Tim Wescott]

That's a sweet looking plane. Plans?!?!? I would think about 55' lines if you're
using .015s ...

"Plans?!?!?" just about sums it up.

I've got some rough sketches -- granted, they're on CAD, but they're rough sketches.  In fact, the span is 2-3 inches more than I intended because I built the wing in the air, using a yardstick to establish the rib spacing.  I didn't take the size of the wingtips into account, and there you are.

If it flies well I'll make plans, maybe.  So watch this space -- if it flies well I'll brag about it, and you can remind me that I'm gonna make plans.

[Kim Mortimore]

Tim.
I'm curious about the wingtips.  Would you like to post another picture showing a tip more clearly?  Thanks.  Very cool plane.

Also, regarding Steve's comment about Bob G's advice, our club recently discovered the same thing--that sometimes shortening the lines a mere foot can wake up a plane with marginal performance.  I recall reading this same advice probably more than once in the past, but often it takes actually trying a fix to become a believer.  Carrying this thought one step further, if you start with lines that are too long, it may be easy to incorrectly attribute performance limitations to factors other than line length.  Just a speculashun.  

[Tim Wescott]

Disclaimer 1: The tips are a compromise, part of a desire to retain enough of the design elements of the scale prototype that I could call it a "Waiex" and have it recognized.  I'm sure they'll make it more sensitive to gusts; I just don't know how much.

Disclaimer 2: The reason you don't see leadouts sticking out of the wing is because I have to cut the slot in the Ultracoat and finish them off.

Yes, I think I did a good job with the aesthetics of the plane.  It really fulfilled its promise as soon as I got that canopy painted on.

[Bill Little]

Hi Tim,

If it easily done (I don't know if the OS 25S and the OS 20FP have the same mounting pattern), Put the OS 20FP in it.  Use Brett's set up for the .20FP and you will be dead solid on the set up, engine wise.

If not, go with 56" eye to eye lines (will be about 60' center to center like Alfadawg said).

I have found out, over the years, that many of the top NATS and World's guys do not use the maximum line length.  While 70' center to center is allowed, many are 2-3 feet short on that with the big engine stunters.

Mongo

[Brett Buck]

I have found out, over the years, that many of the top NATS and World's guys do not use the maximum line length.  While 70' center to center is allowed, many are 2-3 feet short on that with the big engine stunters.

    I have it on good authority that the 2006 NATS was won (with a very close second in 2008) by a guy using 63' (eyelet to eyelet) lines on a piped 61. Similar with the 2008 WC (close second in 2006) and some guy with a piped 75. Of course they have no problem pulling max-length lines (about 66' 6' or so), but that's not where it has the most precise control.

     Brett

[Bill Little]

   I have it on good authority that the 2006 NATS was won (with a very close second in 2008) by a guy using 63' (eyelet to eyelet) lines on a piped 61. Similar with the 2008 WC (close second in 2006) and some guy with a piped 75. Of course they have no problem pulling max-length lines (about 66' 6' or so), but that's not where it has the most precise control.

     Brett

HI Brett,

That was kinda the hidden message in my post.  A lot of guys seem to automatically think that you should use the longest lines allowed.  It has been proven to me that the longest lines are not the answer, 99.999% of the time. (just leaving the .001% as a possible! LOL!!)  Almost everyone I have talked to have said the same thing.  In fact, I don't know of anyone, off hand, that uses the full 70' center to center. ??

Several years ago I was talking with Billy about my newly finished USA-1.  I found out that the 64" lines I was using was the length he used on his.  Figured that I was good to go!  And the plane was very, very good at that length.  It seems that you have a better possibility of flying more precise if the plane is closer, I guess.  Right now, with no practice, I should just hook the handle to the lead outs, then I could just put it where I wanted it to be! LOL!!

Bill

[Tim Wescott]

The last two weeks of September were a thrash to get 'i's dotted and 't's crossed (plus a fuel system problem) so I could make it to Salem, and I just didn't address line length at all.  I ended up flying on a set of .018 x 50' lines that I (or my cousin) bought over 25 years ago.  I'm sure it was because of the lines that I forgot what I was doing and crashed...

At any rate, I made up a set of .015 x 58' lines last night and just tried them out.  That's long, but I figured that I could always shorten them, but lengthening them would be a challenge.  Between high winds and a nasty cold that I'm recovering from I only did one flight, and that was fairly conservative, with just a wingover and some practice climbs with 90 degree corners.

But things felt nice, with good solid tension in the level laps, and only slightly diminished tension during the wingover.  So now I guess I just need some calmer weather to try out the setup so I can tell the difference between the plane flopping all over the sky because of wind, and the plane flopping all over the sky because of me.

[Bill Little]

HI Tim,

Trimming the plane is extremely important for best performance.  One thing off the bat is to try a couple props to see what they do to the plane.  A prop can make a big differrence, along with how the engine is running.  Once you can get it inverted, you can really start on trimming, such as getting the wings level.  If you have adjustable lead outs, then you can work on tension between level flight and high flight.  If tension is lost up top, moving th elead outs forward is the proper cure.  Move them only 1/8th" or so at first.  If, when you get inverted, the outboard wing is high both ways, more tip weight is needed.  If the outboard wing is high up right, but low inverted, then you will need a trim tab on the outboard wing to level it out, if you do not have coupled flaps.  That is just the basic start to trimming.

Big Bear

[Kim Mortimore]

HI Tim,

Trimming the plane is extremely important for best performance......If the outboard wing is high up right, but low inverted, then you will need a trim tab on the outboard wing to level it out, if you do not have coupled flaps.  That is just the basic start to trimming.

Big Bear

Hi Tim,
In my experience it is very common to get a mix of a warp and incorrect tip weight.  This shows up as, for example, the outboard tip a little out of level upright and a lot out of level inverted.  Or vice versa.  There are several possible combinations.  This can be confusing at first.  If you're good at visual geometry, you can figure out what combination you have.  Another option is to post what you have here and we can help you figure it out.  Once diagnosed, I'm curious whether Brett would recommend correcting both conditions to a first approximation at once, or working on them one at a time, possibly correcting the more serious problem first. 

[Tim Wescott]

Trimming the plane is extremely important for best performance. 

Yup.

One thing off the bat is to try a couple props to see what they do to the plane.  A prop can make a big differrence, along with how the engine is running.

Yup.  I mix & match props on any plane I fly; even on a casual sport RC plane with a throttle there's often a huge difference between the first prop and the best prop.

So getting a handful of props from ye olde Hobby Shop and trying them out is definitely on the agenda.  I suppose I should also get some oversize ones and experiment with whacking bits off, but I don't know if I'm up to that much optimization just yet -- maybe after I can stagger through the pattern reliably.

Once you can get it inverted, you can really start on trimming, such as getting the wings level. 

It flies nicely inverted, although with less tip weight it was OK with tension in inside maneuvers and not OK in outsides -- so twist is on the agenda to check.

If you have adjustable lead outs, then you can work on tension between level flight and high flight.  If tension is lost up top, moving the lead outs forward is the proper cure.  Move them only 1/8th" or so at first.  If, when you get inverted, the outboard wing is high both ways, more tip weight is needed.  If the outboard wing is high up right, but low inverted, then you will need a trim tab on the outboard wing to level it out, if you do not have coupled flaps.  That is just the basic start to trimming.

I've got coupled flaps, so I can tweak them (actually I noticed at Salem that I ended up mounting one flap high and one low, in just the right way for them to be aerodynamically tweaked even if the actual pieces of wood are straight -- so that may be my problem, and I hope I can compensate for it without having to rip hinges out by their roots for a re-do).

And it's got adjustable lead outs (and it's a bit light in the overhead with these longer lines), so that's another thing I can address.

When I get chances to fly I'll be alternating between getting my flying abilities up, and getting the plane trimmed, sure thing.

[Howard Rush]

Your airplane looked like it was straight.  The wing was parallel to the lines when it was upright, anyhow.  If you have different line tension in normal-size (unstalled) inside and outside maneuvers, I would suspect that either the vertical CG is off, or the engine is running at different speeds in inside and outside loops.  You can check vertical CG by hanging the airplane by the leadout wires adjacent to a vertical wall. 

If you do have a twist in the wing, the best way to fix it is to untwist the wing.  It will be easy if you don't have a closed D-tube leading edge structure.  Just iron it while holding in a canceling twist as we did with the Ringmaster Sunday.    If it's the flaps that are twisted, fix the flaps.  Add-on trim tabs are bad because superposition of the aerodynamic effects of the warp and the trim tab only applies for a narrow range of angle of attack. 
 
I mentioned unstalled maneuvers because you were pushing the airplane a bit beyond its linear range.    Merely doing bigger tricks might make it behave nicely.

[Tim Wescott]

The jury's still out on whether it's got a problem or not: until Saturday I had not gotten the tank sorted out, and it was richening up severely in inverted flight.  I fixed the tank, added 1/4 oz of tip weight, and changed the leadout position, then it flew OK and it was time to quit flying so I could get all the at-the-house stuff done so I could be gone all day Sunday.

It is a closed D-tube wing, but as near as I can tell (and I double and triple checked before the shear webs went in) it's not twisted.

As far as I could tell it flew just fine on Sunday -- or at least any problems were on the other end of the lines from the plane!  Line tension felt just fine on both insides and outsides Sunday and again yesterday when I was doing 90 degree "school climbs*" to feel out the performance at the least risk to the plane from wind gusts and virus-induced brain fades.

I had short tanked it in case the line length was a Really Big Mistake, and by the time I was comfortable with going inverted I didn't feel I had the time -- and given how badly the wind was gusting I felt that going for Round Two with the turbulence would have been a Bad Idea.

So now I just need some time with the plane to figure it all out.  Longer lines should help, as should actually getting up to 45 degrees.  I just need some half way decent flying weather, and time to get out and play.

* a 90 degree inside corner from level flight up to 45 degrees, then a 90 degree outside corner to level flight, descend gradually, repeat.

[Scott B. Riese]

The plane is way cool in the air. WISH I would of known that you needed lines at SALEM....I had my line tying kit with me and lots of wire.

.015x60' is your starting place
I would fly it with .015x58'
Try a 10x4 APC Prop. You had some line tennision issues on your loops.
ANYWAY It was great to meet you and If you need anything you can always e-mail me

[Tim Wescott]

I wouldn't have changed anything that dramatically at the contest, although I certainly appreciate the thought.  I actually considered making up lines Saturday night, but I didn't want to find out that it was a bad idea on my first flight Sunday, over asphalt. 

I'm starting with 015 x 58 lines, I'll see how they do once I get some decent flying weather (maybe next Wednesday, if I get enough work done Monday and Tuesday).  I may have to go shorter, given what Buck says about my choice of motor & plane.

(and I'm going to save pennies for a 25LA or similar).

[Tim Wescott]

Ahhhh.

I don't know if the plane is flying well in absolute terms (I need to break loose and get down to Salem or Delta Park, and get it into the hands of someone competent).  But I do know that it was flying pretty well today.  I put it on .015" x 58' lines, with a Fancher-style handle that I built for myself over the (rainy) weekend.  'cause it's a weekday and 'cause I had to recruit launches from the RC crowd at my field and 'cause I had some other commitments (pictures for an RC plane for Flying Models) I only flew twice -- but it seems to like the 58 foot lines; it certainly maintained good tension in the wingover and the loops that I did.

Now I just gotta practice, practice and practice some more.

[Jim Kraft]

Wow Big Bear; In post #21 you said  you flew the USA-1 on 64 inch lines? I am impressed. Well, you did say you should just hook the handle to the leadouts. You are getting pretty close, LOL. Sorry; I just couldn't help myself.

[Mark Scarborough]

Tim, Salem was good times, good to meet you and glad to see your interest.
Howard makes a pretty solid reccomendation too, same thing I did, (do?) at times. cramp my manuevers. the airplane , she doesnt like this,,
keep flying and enjoy it,,

[Tim Wescott]

I am working really hard on opening up my maneuvers, I've just about gotten over being amazed at how much of a difference it makes, and now I need to work on always getting up to 45 degrees and always getting down to a base line (I'm taking someone's recommendation and going down to 10-12 feet for now, and working down to 5 feet as my loops get rounder and my confidence grows).  I'm thinking that I need to build a protractor in my driveway that's big enough to stand inside, so I can learn to gauge where 45 degrees and overhead really are (the overhead line is easy, as we have track lighting in the family room, but straight overhead, I suspect, eludes me).

I have yet to do an overhead eight.  I did a (single) vertical eight today, and a few overhead loops, to see if the plane seemed up to it.  I think it is -- the lines loosen noticeably when I'm diddling around overhead but control stays positive and the plane seems to do OK if I manage to keep things smooth.  I need to fiddle with the leadout position a bit, I think.

[jim ivey]

In my day an os max was a 35 there was an os 19 an os 15 deisle and an os 60 but they weren't called maxes as i recall. If its a 35 you need 60 foot lines. 52s will be to short for any airplane with a hot 35 on it, and maxes were hot combat engines.    jim

[Tim Wescott]

In my day an os max was a 35 there was an os 19 an os 15 deisle and an os 60 but they weren't called maxes as i recall. If its a 35 you need 60 foot lines. 52s will be to short for any airplane with a hot 35 on it, and maxes were hot combat engines.    jim

It's a 25.  Documentation says "OS Max 25".  Plain bearing, front rotor, cross-flow (baffle piston) scavanged mild sport motor.  I think it's the predecessor to the FP, I know that it came in a number of sizes.

I've been told it's not enough engine for my plane, and don't know enough to know by flying the thing if that's right!  At any rate, it's better than nothing and I'm learning with it, so I won't complain.  (If I find a 25 FP at a rummage sale I won't complain either).

[Bill Little]

It's a 25.  Documentation says "OS Max 25".  Plain bearing, front rotor, cross-flow (baffle piston) scavanged mild sport motor.  I think it's the predecessor to the FP, I know that it came in a number of sizes.
(snip)

Hi Tim,

The "S" series (your .25) came in .10, .15, .20, .25, .30, .35 (and I don't know what after that.)    The OS Max .35S was an extremely popular stunt engine in the late '60s-early'70s with many top fliers using them.  The "S" series do not have the raw power of the "FP" series, but were all real decent 4-2 stunt engines.  Possibly the most diverse in displacement series of OS engines made.  If your .25 is not worn out, you can use it in your plane (as evidenced by the fact you are) with some of the *old* methods of energy management.  Everything needs to be smooth to not kill off airspeed and overload the engine, etc..  Using the *old* standards, everything would be classified as underpowered today, I suspect.  Planes originally flown on Fox .35s are even getting PA 65s now! 

Big Bear

[Tim Wescott]

Someone showed up at our mostly RC field yesterday with an OS 10S or 15S on a plane that had just a bit too much hanger rash to really be flyable.  I almost offered him $20 for the thing less radio, just for the engine "for later".

[Tim Wescott]

If your .25 is not worn out, you can use it in your plane (as evidenced by the fact you are) with some of the *old* methods of energy management.

That makes me feel a bit better -- part of the rational for choosing the airplane size was scaling down from a Nobler with it's 35, and up from various 19 powered ships in Flying Models.  They mostly had about the same number of square inches/motor displacement, so I thought I was safe.

And a plane that forces me to fly smoothly may not be a bad thing at this point -- smooth is definitely one of the goals of my current training program!