15's or 18's

[Bob Reeves]

Under the new rules I can fly my 54 ounce ST 51 powered Skylark on 15's. Been flying it on 18's and thinking if I went to 15's I could add a foot and still reduce the line drag by 0.8 sq/inches and line weight by about 1/4 ounce.

Thought this might be an intresting topic for discussion, wouldn't think I'm the only one that has an airplane that falls into the range where 15's are now an option.

[Ron King]

I changed my Cardinal from a Brodak 40 to an LA 46. I kept the same .015 lines and really didn't notice much difference in performance.

The nicest thing about the rule change for me is all my planes can fly on .015. Makes it easier to keep track. 

Ron

[Bob Reeves]

Yep, like my ST 46 powered Nobler, no question it will be 15's.

On the other hand my 64 ounce Saito 62 Latency will stay 18's even though I might be able to squeze by on 15's.

[john e. holliday]

It is amazing what the new rules have brought about.  My P-39 weighed out to 65 ounces.  Now powered with an LA 46.  The so called miracle prop did not like the weather we had.  Going back to Zinger 11-5.  Don't know what happened to all the stunt and racing pilots this past weekend.  Only complaint about the weather was no wind to speak of.   Where are the guys from the areas of contests we attend.  Don't want to start a fight, but, I know of one contest that has been rained out more, than having good weather.  Guess the Brother Hood of the Ring took the rest. 

By the way, under old rules would have  pulled 46 pounds.  New rules only had to pull 36.  Still using .018 lines 65 foot long.  DOC Holliday

[Howard Rush]

The resonant frequency of the .015s will be higher than the .018s.  Resonance is usually more of a problem when line size increases, so it's probably not a big deal.  The .015s are stretchier than .018s, although you could use Staystrates, available from PAW or Eric Clutton.  They are stiffer than seven-strand .015s.  I haven't compared them to seven-strand .018s, but maybe I should, because I'm now entitled to use .015s.   I'd try them and spend a few flights fiddling with trim before deciding which to use. 

[Bob Reeves]

The resonant frequency of the .015s will be higher than the .018s.  Resonance is usually more of a problem when line size increases, so it's probably not a big deal.  The .015s are stretchier than .018s, although you could use Staystrates, available from PAW or Eric Clutton.  They are stiffer than seven-strand .015s.  I haven't compared them to seven-strand .018s, but maybe I should, because I'm now entitled to use .015s.   I'd try them and spend a few flights fiddling with trim before deciding which to use. 

Interesting, mind expanding on how resonance of the lines effects our stunt ships?

Have read Brett and your comments on 15's being stretchier, could be interesting to try to find the magic point of line length and airplane weight where the reduced drag is offset by the lines being too much like rubber bands.

[Howard Rush]

Unless your airplane needs a lot of line force to deflect the controls, I'd guess you would prefer the .015s.    I am not sure that the .015s are stretchier than .018s, because .018s have more of a curve because of drag.   Does airplane weight affect the combined delta stretchiness?  This is on my list of stuff to think about. 

[Brett Buck]

Under the new rules I can fly my 54 ounce ST 51 powered Skylark on 15's. Been flying it on 18's and thinking if I went to 15's I could add a foot and still reduce the line drag by 0.8 sq/inches and line weight by about 1/4 ounce.

Thought this might be an intresting topic for discussion, wouldn't think I'm the only one that has an airplane that falls into the range where 15's are now an option.

     Mine, too. But I have already done that  - I can use whatever lines I want for the Team Trials, and tried it both ways. The .015s had less line whip as you would think, but I never got the same kind of precision control as I had with the .018s. The most noticeable effect was that I had to anticipate each corner entry by what seemed to be a huge amount of time. And I almost never managed the same kind of sharp transition from straight to turn - it was always smooth but indistinct. It particularly showed up on the squares and also the 4-leaf. GMA would have loved it (he took Ted and I to task after watching a videp of the 2000 Flyoff when we were 1st and 3rd (t), because we were making sharp transitions into and out of corners, and he wanted them to swoop. I pointed out that his own maneuver descriptions required *infinite* accelerations at these points) but it was going to be a sure loser. If nothing else it was going to require much larger maneuver sizes, since by the time the airplane got from level to vertical, it was already at 30 degrees. Having previously flown with a cable handle I know that was just ridiculously soft by comparison. With a hard-contact handle it was at least conceivable to use the wimpy lines.

    In short, it just killed the responsiveness around neutral. I would have had to take off at least a few feet to get it back, but then I am closing in on 60 feet and the less room you have the worse the problem becomes.

     This was using conventional 7x1 .015 and .018's. The Laystrate 3x1 soldered .015s are probably stiffer and would be worth a try. I would be surprised if it was a completely different story, but it might be OK. I was actually interested in trying the .020 Laystrate instead, but I doubt that I will have the time or energy.

     But bear in mind also that you are almost certainly going to need to switch back if the wind comes up. In the 29 MPH wind at the 2003 NATs I could feel the .018s stretching at the bottom of the round loops. I wouldn't trust .015s in those conditions even with a piped engine (the PA61 was 16-stroking and sounded like it had a potato in the exhaust at the bottoms of the loops, to the point I though the plug was going to cool and the whole thing quit), with the kind of furious whip-up you get with 4-2 motors or 4-strokes, no way.


     Brett

    

[Howard Rush]

I flew with .015s at the 2003 Nats.  I didn't trust them, but there was only a beanfield downwind.

[Bradley Walker]

with the kind of furious whip-up you get with 4-2 motors or 4-strokes, no way.

I hear yah... 

Gordy's Saito 72 powered Tony sucked that year.

Constantine's high pitch/low RPM 4-2 motor was horrible in the wind too.

[Howard Rush]

Gordy didn't fly both flights that day.  In Open, only seven guys did:  three piped PA's, one piped RO-Jett, one piped OS .40 VF, Konstantin's, and whatever Dan Banjock was flying.  Dan, of course was laughing throughout both his flights.  The thing that impressed me about that group is that three of the top five built their own engines. 

[Brett Buck]

I hear yah... 

Gordy's Saito 72 powered Tony sucked that year.

Constantine's high pitch/low RPM 4-2 motor was horrible in the wind too.

     <<yawn>>

    Brett

[Brett Buck]

Gordy didn't fly both flights that day.  In Open, only seven guys did:  three piped PA's, one piped RO-Jett, one piped OS .40 VF, Konstantin's, and whatever Dan Banjock was flying.  Dan, of course was laughing throughout both his flights.  The thing that impressed me about that group is that three of the top five built their own engines. 

   Oh, there more than 7 that attempted both flights, just not more than 7 that completed both flights!  I crashed in level flight and still finished 10th.

    Brett

[Bradley Walker]

Gordy didn't fly both flights that day.  In Open, only seven guys did:  three piped PA's, one piped RO-Jett, one piped OS .40 VF, Konstantin's, and whatever Dan Banjock was flying.  Dan, of course was laughing throughout both his flights.  The thing that impressed me about that group is that three of the top five built their own engines. 

That last day is immaterial, really.  Who chose to fly on the last day (there was plenty of debate whether flying that day proved ANYTHING) does not diminish the fact that the wind blew horribly all week, not just on the last day, and there were many INCREDIBLE wind flights from people without pipes.  I mentioned Gordy and Konstantine right off the top of my head.

There were very few pipes at the Muncie WC's the next year where the wind blew 20 plus.  I did not notice the pipe rigs were superior, quite the contrary.  I do not think I was the only one who noticed...

[Howard Rush]

Now, 'Zilla, lets look at your argument.  People work hard to compete for the Nats finals.  The unpiped flew on the windy qualifying days and could have gone on to win if they'd wanted to, but had to leave early to get home to change the cat box or something?  I was there.  Anybody who thought he had a chance of doing a pattern on top-20 day attempted to fly.  On the qualifying days, a good flier could choose to forego his second flight if the wind came up.  Friday, which was windier, required two flights.    The guys who made the top five, including Konstantin, made it because they knew what they were doing.  Not surprisingly, it was the usual guys.  The one who impressed me most was Richard Oliver.  Earlier in the week, when it got windy after the official flights were over, Richard was out there flying and trimming.  The first couple of days, his airplane was going about Mach 2 in the fourth loop of his clover.  By Friday he had it working perfectly.  

You can use whatever you want, though, and show us how.  Alternatively, you can use actual facts to support your argument.  But if you tell us that four-strokes dominated the 2003 Nats, somebody's going to call you on it.  

I think you are correct that pipes are more popular in the US than elsewhere.  Looking at results from the last world champs, I see only two guys in the top 10 that I remember having tuned pipes, but perhaps there were more.  The guy who won had a pipe.  The same guy won the aforementioned 2003 Nats and the contest I went to last weekend.  He's pretty good.

[Brett Buck]

Veering away from Brad's diversion, the bottom line is that is you are near the edge on the line size, I think it's worth trying both ways, trimming for the optimum each way, and seeing for yourself. But I think I have convinced myself for models near the edge that the .018s are the way to go. Someone else might come up with a different answer.

      Brett

[Bob Reeves]

Unless your airplane needs a lot of line force to deflect the controls, I'd guess you would prefer the .015s.    I am not sure that the .015s are stretchier than .018s, because .018s have more of a curve because of drag.   Does airplane weight affect the combined delta stretchiness?  This is on my list of stuff to think about. 

Ya lets get back to the subject... I'm talking about a 54 ounce classic airplane with a 4-2-4 engine not a 60+ ounce piped PA 60+. As I said I wouldn't even concider 15's on my PA ship at 64 ounces. Guessing due to the old rules nobody has any data one way or the other as to the break point where 15's might be an advantage over 18's.

Now lets throw another fly in the ointment.. Does it make a difference with 7 strand or 19 strand cables..

[Bradley Walker]

You can use whatever you want, though, and show us how.  Alternatively, you can use actual facts to support your argument.  But if you tell us that four-strokes dominated the 2003 Nats, somebody's going to call you on it.  

I never said any of that...  that is ridiculous.

All I did was address Brett's comments.  Something to the effect that only pipes do not wind up... "I wouldn't trust .015s in those conditions even with a piped engine (the PA61 was 16-stroking and sounded like it had a potato in the exhaust at the bottoms of the loops, to the point I though the plug was going to cool and the whole thing quit), with the kind of furious whip-up you get with 4-2 motors or 4-strokes, no way" which is load of you know what, and he knows it.  

In fact, the vast majority of stunt competitors wind up in the wind.  Pipes included.  I have seen piped ships that take off like a rocket when hit with the slightest wind (there is nothing worse than a poorly set up pipe ship in the wind), and I have seen both 4 strokes and 4-2 break 2 strokes that bucked the wind remarkably well.  Joe Parisi's Aussie 4 stroke in the 2004 WC's was very impressive for example (as was Gordy's Saito 82 in the 2003 Nats).  Conversely, the Chinese 4 strokes SUCKED in the wind at the WC's.  

Many of the European 4-2 break motors are incredible in the wind.  There was plenty of proof of this in 2004 at the WC's where the wind went from 0 to 20 MPH several times.  The current Nats champ does not have a pipe, in fact and he has won twice at Muncie so I am sure he does not manage "furious whip up".  I would hazard a guess that Brian Eather would put his Stalker 61 up against anything out there when the wind gets frisky.

As far as the 2003 Nats final, there were lots of people who chose not to fly on that last day, many with pipes.  I believe there was a huge blow up on SSW after wards about the final being a "survival contest" (I had to leave but if memory serves me Bob G. flew in that final and fell down).  Len was particularly upset as Matt chose not to fly (if I remember correctly) and Len asserted this was a wise decision.

PS:  I got the EXACT same run Brett described with my PA 65 *without* the pipe using nearly 6 pitch.  In fact, I wrote extensively about it in my last CLW article.  Bob G used to do it with a Fox 35.  Bill Wilson could hang with anyone in the wind with his Johnson 35 powered Panther...  It has little if anything to do with a pipe...  

[Scott Jenkins]

Guys,
If you are worried about stretch affecting control why not go with .015 solids and eliminate the stranded stretch problem. Just keep them clean and rust free and they will work just fine.

Scott

[Brett Buck]

All I did was address Brett's comments.  Something to the effect that only pipes do not wind up... "I wouldn't trust .015s in those conditions even with a piped engine (the PA61 was 16-stroking and sounded like it had a potato in the exhaust at the bottoms of the loops, to the point I though the plug was going to cool and the whole thing quit), with the kind of furious whip-up you get with 4-2 motors or 4-strokes, no way" which is load of you know what, and he knows it.   

 
     OK, Brad, everyone is paying attention to you again!  I hate to dignify yet another delusion-of-grandeur hissy fit with a sensible response, but hopefully everyone else will learn something even if you are incapable.

    I actually believe EXACTLY what I have said, based on observation (having flown about  10x the number of 4-2 break fights in competition and practice than you have). Most of the 4-strokes I have seen were even MORE prone to whipping up, with high-pitch props and no feedback from the engine, it's inevitable.  That has it's good point and bad points - the reason that Konstantine made it was that while his model whipped up like the worst of the ST60 planes from the good old days, the exact same effect also allowed it to carry momentum through the upwind side. The biggest problem on the day in question was maintaining level flight.

   The piped planes tended to have more problems because of their superior airspeed stability. Too stable, in fact. That's why my airplane, even thought it handled the places where it whipped up better than most, it also lost a bunch of groundspeed as it nosed into the wind - because it was trying to maintain a constant airspeed. The solution, found on the guys who made it, was to either jack the speed up to even at a constant airspeed it was sufficient, or to have reduced speed stability, live with the whip-up (and compensate for it where possible) and take advantage of the ability to maintain the momentum around the upwind side. I would have made it had I been running pipe pressure even at the speed I was running - I had ram air and that greatly enhanced the airspeed stability - thus I was getting 25 (55-30) mph groundspeed nose into the wind, and Konstantine was getting 45 (55-10) since the airplane didn't maintain a constant airspeed. Gieseke's was even worse than mine, he just stayed ahead of the whipping better than I did.

    I just got caught out on that day, but the basic concept that it's possible, with piped engines and low-pitch props, to get *too much* airspeed stability for ideal wind performance, is well known from the early 90's. It's fantastic in ideal conditions, and it doesn't whip up, but they can lose penetration in some maneuvers and in extreme cases, level flight. That's why the setups changed from the late 80's to the mid 90's - Paul Walkers VF system being the first I know of to recognize that.

     It's my opinion that a 64 oz 4-stroke model on .015 lines is quite marginal in these sorts of extreme conditions. It will probably do better as far as penetration goes than some piped systems but it will have a tendency to whip up if you don't get exactly the right maneuver bias. I wouldn't do that.

   And I might note that I didn't say anything about 4-strokes being overall better or worse than anything else- just that they whipped up more in some conditions. You know, the part *relevant to the question asked*. This was not nor intended to be another forum on 4-strokes VS piped engines. Competition will answer that question .

      Brett

 

    

[Howard Rush]

Back to line stretch, has anybody calculated the effective stretch due to the lines bowing back from drag compared to the elastic stretch of the material?  I kinda suspect that the .015s would compare more favorably for stretchiness to .018s for light airplanes.  Relating this to the 2003 Nats, I wonder if the reason you crashed and I didn't was because I was using .015s.   

Yes, Bob Gieseke fell down.  We worried about him, but then we noticed that he never let go of his pipe.

[Brett Buck]

Back to line stretch, has anybody calculated the effective stretch due to the lines bowing back from drag compared to the elastic stretch of the material?  I kinda suspect that the .015s would compare more favorably for stretchiness to .018s for light airplanes.  Relating this to the 2003 Nats, I wonder if the reason you crashed and I didn't was because I was using .015s. 

     No I think it was a lot simpler than that - I just lost too much airspeed coming around into the wind because engine was putting on the brakes. And I was too slow to begin with - 5.5.

      Brett

[Howard Rush]

5.5 was a little pokey that day.  I was screwing in the needle valve. 

Now that I think of it, I'll bet Bob Reeves is chuckling at this four-stroke-in-the-wind discussion.  He's been flying four-strokes in Tulsa for years, and, as I remember, Tulsa isn't exactly the Horse Latitudes.

[Dennis Moritz]

Dan flew a piped PA 61 in 2005. Constantine was the most interesting to me. Because his plane appeared to be slow, almost Classic (like a Supertigre 60?), yet got good air penetration. That is how the flight appeared to me. I have no idea of his actual lap time. The fuselage of Constantine's plane was very slim, his high rudder appeared almost aerodynamically balanced by a high canopy, dunno if that had an effect or not. What was that airfoil. Did Constantine design and build his engine or was he flying a Russian make, designed by someone else. What happened to Constantine? He was masterful that day IMHO. No pipe on the Constantine engine. Dan was laughing, in part, because our home field in Neshaminy Park PA blows every which way, most of the time. Shifting at random, swirling, etc. Tress, breezes off the Delaware, thermal pockets and downdrafts. In a way Dan felt like he was back home.

[Bradley Walker]

    OK, Brad, everyone is paying attention to you again!  I hate to dignify yet another delusion-of-grandeur hissy fit with a sensible response, but hopefully everyone else will learn something even if you are incapable.

Yah, Brett, I am throwing the hissy fit...

[Howard Rush]

Konstantin was missing for awhile because he fell off a ladder and did significant damage to his body.  He was at last year's world champs. He was the Lone Canadian in F2D. 

[Bob Reeves]

5.5 was a little pokey that day.  I was screwing in the needle valve. 

Now that I think of it, I'll bet Bob Reeves is chuckling at this four-stroke-in-the-wind discussion.  He's been flying four-strokes in Tulsa for years, and, as I remember, Tulsa isn't exactly the Horse Latitudes.

It is kinda ironic that the engine that gave me the confidence to make the jump from being afraid to fly in anything over 10 MPH to competing in almost anything anyone else will fly in was a Saito 56 turning a 13-7. This was after a solid year trying to get a Stalker 61 working in all conditions without success.

[Chris McMillin]

Speaking of control lines and their stretchiness, I flew two seasons with .014 solids because I was told that they were "better" than cables for heavy models. I replaced them with .018 7 strand cables and found a whole new world; a lot of instant input transfer that was not there with the solid .014's.
Ever since then I have used .018 cables and put up with a little whip but have had instant input results like Brett was mentioning above. The hard point handle made it just that much more precise.
Chris...

[john e. holliday]

I just wonder if Big Art is reading any of this and getting cramps laughing at it.  DOC Holliday

[Steve Fitton]

I switched to .015s on my 50 powered classic ship at the spring Huntersville contest.  I went a foot longer than the '18s, which helped get the lap times in a better speed than before, based on where my motor/prop combination wants to run.  I can't say I noticed huge differences, but, it did help a bit in the overheads, which is where I was looking for improvement.
My pampa plane weighs 62 ounces, so I could run 15s, but I'm chicken to try it, especially since my non piped 60 will promptly launch my plane into orbit if the wind blows...

[Robert Zambelli]

I don't know if this has been accessed before but there is some very good information regarding cable construction, materials, breaking strengths, etc.

                            Try this:   www.savacable.com

Access the sections on cable construction as well as miniature cables.

             Bob Z.

[Larry Cunningham]

Gentlemen,

I'm always amazed at how sensitive top fliers are to various parameters. Looking at the site
referred to by Mr. Zambelli, I was curious as to the practical range of stretch for small diameter
steel cables. I've attached that graph.

As a simple rough, conservative estimate, using the "normal" (vs low stretch) cables, after 2 million
cycles, they are stretching less than .02 inches/foot. Say, 65' lines would stretch up to 1.3" (half that
or less for the first 600,000 stretch cycles). So, you guys are sensing the difference in stretchiness,
which amounts to less than an inch over 65' lines? And, is line tension anywhere near sufficient enough
to get into these areas of maximum stretch?

I'm guessing that your senses are not quite that fine - but what I think you might be viewing as stretchiness
is a side effect of the amount of drag - lines bowing, which we can all easily observe - and subject to change
as line tension and wind conditions effect the model. The reduced drag seems to be a major reason for using
solid lines in spite of their care and maintenance needs.

Of course, never having flown at such competitive levels, I'm not in a position to say anything about it, just
stroke my engineer's beard (which sometimes has a prune in it) and wonder "Hmmm..".

Just sayin'. ;->

L.

"If the Earth really were your mother, she would grab you with one rocky hand and hold
you under water until you no longer bubbled." -Kathleen Dean Moore

[Howard Rush]

That stretch seems to be how much longer the cables get over time.  Yes, it's imperceptible.  The stretch that affects us is the elasticity of the lines, measured in units of 1/force.  It determines how much incremental handle deflection it takes to compensate for incremental hinge moment due to airspeed or line tension.  This problem became obvious to me when I was trying to guess how much control input it would take to do square eight corners in the wind with a 68-oz. airplane on 70' .015" lines.  It's easier to guess with .018s.  Flap tabs oughta help, too.  I have a device (a bellcrank with a pointer on it) to which I connect a pair of lines and pull.  I usually use it to duplicate line lengths when making spare lines, but I also use it to compare line elasticity. 

[Alan Hahn]

One thing to think about is that we are probably talking about a few inches of actual line movement during a maneuver (how much the bellcrank can rotate). Now I would have to think carefully to figure out how much extra tension I am applying during a maneuver, but at nominal max, all tension on both lines could be transfered to a single line. This does not include actual radial acceleration of the plane due to "jerking" it inward.

Haven't thought completely about the issue. So how much line stretchiness matters isn't obvious to me at this stage. Another point is that maybe I don't have the "touch" to feel the difference---a skill level issue.

[Howard Rush]

Sure you do.  Do some square eights in the wind.

[Bradley Walker]

It is kinda ironic that the engine that gave me the confidence to make the jump from being afraid to fly in anything over 10 MPH to competing in almost anything anyone else will fly in was a Saito 56 turning a 13-7. This was after a solid year trying to get a Stalker 61 working in all conditions without success.

That won't work, it will whip up ferociously... a guy on the Internet told me.

[Bob Reeves]

That won't work, it will whip up ferociously... a guy on the Internet told me.

Ya I heard that someplace, sure glad my Saito's don't read the forums. I am expierementing with a lower pitch prop right now. A 13-5.5 three blade CF. It doesn't wind up any worse than the 13-7 but it is slowing down in the square eight.

Anyway that's another subject... I made a set of 15's for the Skylark this morning, 1 foot longer than the 18's I am running, today or tomorrow I'll fly it with the 18's then switch to 15's and see what it does.

[Busby]

I fly a TEOSAWKI with an LA46 on .015s and its quite comfortable.
Of course its a 37 oz plane on 64 eye to eye at 5.6  laps , almost no like tension at all.
It probably doesn't pull more than 10/15 lbs.
My Shrikes are 50 oz planes PA 40 on pipe 63 ft lines 5.3/5.4 and they are about all i would be comfortable with on .015s,
Any thing larger or heavier are on .018s.
Busby

[Brett Buck]

Yah, Brett, I am throwing the hissy fit...

     I don't know Brad, some people don't appreciate being called liars - over and over - in public. A couple of times this month, actually. I would ask you to stop, but I already did and yet here we are again. I asked you to respect the fact that I could have an opinion different from yours. You subsequently went apesh*t over a mostly unrelated comment on another topic, then claimed I was lying for expressing it. That about cover it? And that's just in the last month.

    Here's an idea - should I run any comment on on topic for which you assert dominion by you first for approval? Just so I don't say something you don't agree with and therefore propagate more "lies"?

    Got anything rational to say about speed stability for 4-strokes that might actually help someone?

     Brett

[RandySmith]

Gordy didn't fly both flights that day.  In Open, only seven guys did:  three piped PA's, one piped RO-Jett, one piped OS .40 VF, Konstantin's, and whatever Dan Banjock was flying.  Dan, of course was laughing throughout both his flights.  The thing that impressed me about that group is that three of the top five built their own engines. 

I think the main reason may people did not fly was they had never flown their ships in winds that high,  so they just didn't want to venture into the unknown.
I did not have any problems with the high winds (except the backwards rolling shear from the revial tent) as I had flown the plane in the before and knew it would go thru them.
 I wasn't using muffler pressure either ,but we use a  90 degree  plastic angle tube on the uniflow vent.
This stops the speed up - slow down from the high winds changing the pressure in the tank. This little unit stays on the plane always.
My setup that day was to use more nitro and let the plane speed up a little more in the manouvers and just steer it thru.
If you do fly in this type of winds , a rearward CG is much much better, and pull the overhang on your handle back toward your hand.
I would not ever dream of flying a forward CG setup with a lot of handle overhang in high winds...that would be a recipe for diaster. I do know for a fact that a couple of people who did not fly had more nose heavy ships, and would have had a very tough time getting enough pressure on the handle to make their plane turn.

I would never use .015 on anything that is over about 55 ounces as the .018s  are so much more of a rock solid feel.
I can tell in the pull test how much more the .015  stretch  as opposed  to the  .018.  The seven strand 018 also seem to stretch less than the 19 strands do .


Regards
Randy

[Kim Doherty]

Arden Zhang's (Zhang Xiang Dong - W/C 1988, 1990) original SkyWriter weighed 53 ounces. A very nimble bird it was in most any weather condition with a hand built .60 engine. One of the first things he suggested I do after he arrived in Canada was to never use .015 lines as they stretch too much in the wind. One day at a pretty large contest I ignored the advice and the rest as they say is history. Ouch!

I will say that if you are going to fly on .015 lines that the Russian high carbon combat lines with brass plating have little stretch and are very smooth against each other.

They are available from Mejzlik Models:    http://www.mejzlikmodellbau.com/


Kim.

[Richard Grogan]

Gentlemen:
This thread is about choosing line sizes with the new size rules, and issues of those decisions.Stay on topic. If name calling is your thing, hit the "CHAT" button and take it over there.Remember, this is Stunt Hangar. If you want to discuss 4stroke v/s 2 stroke/w pipe,or who knows more than you,or whatever,then start your own thread. Same rules apply there as well.Good lard,we're talking toy airplanes here, for heavens sake. Certainly not worth starting a flame war over.Opinions vary(often), thats human nature. Keep it clean folks, ok?

[Larry Cunningham]

When I build lines on my back fence, I do a really hard pull test on them, say >50 pounds, and
I have observed a very small stretch (.015 braided, 7 strand), some fraction of an inch. A
matter of sensitivity for me, I'd never be able to detect any stretch in flight, getting nowhere
near the line tension required. However, I accept that seasoned fliers can tell the difference.

My natural question has to be, if the control system sensitivities can be felt for line stretching:
why isn't everyone doing everything possible with their control system geometry to linearize it?
I think I know why, my theory is that whatever the transfer function is for the particular
ship's control system, the pilot adapts to it, adjusts, and eventually linearizes the controls in
his brain/reflexes The ship is also unlikely to respond linearly to control surface deflections - the flier
has to compensate for it all to get the final control product. The non-linearities are mostly fixed.

Now, if we add in something like line stretch or bowing of the lines or whatever muddies up
the control function, the flier is indeed able to feel it. Whatever minimizes such effects would
be desirable. At least that's my theory. ;->

L.

"Man invented language to satisfy his deep need to complain." -Lily Tomlin

[Bradley Walker]

    Got anything rational to say about speed stability for 4-strokes that might actually help someone?

I think I have done plenty on that front already, Brett.  

----------------------------
For all 4 cycle users, NOW HEAR THIS:

Put the engine on its side.  The engine can be run exceedingly rich, and when it starts to wind up it floods the engine, and the engine slows down.  GOOD ENOUGH?  This EXACTLY what Bob Reeves is doing AT MY INSTRUCTION...and it works.  This is the same technique used by Joe Parisi in the 2004 WC's and he did not wind up in the wind.

---------------------

The Yatsenkos are doing the same thing, as is just about half of all the good FAI flyers outside of the US.  They are doing the same thing with the Retro in the Shark.  Kaz Minato is doing the same thing with his engines, and has for decades.  

There is more than one way to skin the cat, Brett.  I did not call you "a liar" either, here or anywhere else.  I just said you were wrong...  

I also never insulted your pipe rig in anyway or diminished its performance.  David and yourself are definitely "doing it right" in many ways when it comes to the way you run your engines... I believe I *specifically* mentioned your engine performance in my last CLW article as the benchmark of the 4-4 / 4-8 / 4-16 cycle run.  That being said, I think your statement about windup was ridiculous (or *wrong* if you do not understand that) so I commented on it.   I still think it is wrong.

Deal with it.

[Steve Fitton]

My Shrikes are 50 oz planes PA 40 on pipe 63 ft lines 5.3/5.4 and they are about all i would be comfortable with on .015s,
Any thing larger or heavier are on .018s.
Busby

Whoah!  Your Shrike only weighed 50 ounces?

[Howard Rush]

Now, if we add in something like line stretch or bowing of the lines or whatever muddies up
the control function, the flier is indeed able to feel it. Whatever minimizes such effects would
be desirable.

Igor's flap linkage does this.  Here's what I did:

[RC Storick]

I'm still watching

[RandySmith]

""why isn't everyone doing everything possible with their control system geometry to linearize it""""

Hi Larry

That really is not the problem people think it is, as long as your control system is consistant, and doesn;t change pilots adjust easy to the loss as the bellcrank move thru at harder angles.
 Also I only use about 10 degrees of control in the round stuff, and the squares  that are hit harder don't seem to suffer at all from a declining rate at the extremes.
 I think this would be much more of a problem for small bellcranks using all of the range to turn the ships

Regards
Randy

[Steve Fitton]

I'm still watching

Watching what?

[RandySmith]

Whoah!  Your Shrike only weighed 50 ounces?

Yep  BUZ's  plane  weigh 50 ounces...Curt's weighed  48 ounces...someone else  had a 60 ouncer