Line Sizes Then vs Now

[Dick Pacini]

One significant change during my 36 year absence is that now lines are sized according to model weight instead of engine displacement.  Probably necessary because of electric power.

Planes powered by a ST 46 required .018 lines.  Today, that same plane can fly on .015 lines, as long as the weight is within limits, if I interpret the chart correctly.

To those who used to rock .018's, how do you feel about using the lighter .015's today, if the airplane is within the proper weight range?

[Brett Buck]

One significant change during my 36 year absence is that now lines are sized according to model weight instead of engine displacement.  Probably necessary because of electric power.

Planes powered by a ST 46 required .018 lines.  Today, that same plane can fly on .015 lines, as long as the weight is within limits, if I interpret the chart correctly.

To those who used to rock .018's, how do you feel about using the lighter .015's today, if the airplane is within the proper weight range?

   With something like an ST46, it's probably worth it. A typical good ST46 plane is in the low 50-oz range at most, and mid-40's ideally, so .018s were a serious limitation.

    I think for a piped airplane near the limit I wouldn't want to try .015s. It's probably safe in most conditions but I think the compliance limits the precision, and the airplane can handle the weight and drag.

   Brett

[proparc]

To be honest I NEVER flew my st46 on .018's. I always thought it was a stupid rule and I still do. That said, I never flew my Saito 72 on anything but .018's. Now listen, the 72 is NOT going to break high quality .015's ever. I would probably break my arm, or tear out the control system first. It actually pulls less than most LA 46 ships, (trust me I know). I do it because the .018's allow for stepping on lines etc. The psyche factor is better oriented for abuse.

The rule that makes sense to me, is the 10x the weight of the model rule. And let me decide what I want to use.

[Brett Buck]

To be honest I NEVER flew my st46 on .018's. I always thought it was a stupid rule and I still due. That said, I never flew my Saito 72 on anything but .018's. Now listen, the 72 is NOT going to break high quality .015's ever. I would probably break my arm, or tear out the control system first.

    Allen Goff's airplane broke both lines and crashed outside the circle at the 2003 NATs. His arm was not broken. Those were 0.018s and they had just survived a 45 lb pull test.  .015s are NOT strong enough for the average Saito 72 airplane under the full range of conditions that it can be flown in.

    Brett

[Howard Rush]

To an old combat flier who is used to seeing half a dozen flyaways a contest, you folks seem pretty conservative.  The old rule worked fine.  Now we have to go to the bother of weighing airplanes at each contest, just to be consistent between IC engines and electrics.  A simpler solution would have been to outlaw electrics. 

[Tim Wescott]

To an old combat flier who is used to seeing half a dozen flyaways a contest, you folks seem pretty conservative.  The old rule worked fine.  Now we have to go to the bother of weighing airplanes at each contest, just to be consistent between IC engines and electrics.  A simpler solution would have been to outlaw electrics. 

I know you weigh your slime-powered plane with the tank empty -- does one weigh ones electric sans battery?

[EddyR]

I still use .018 on my ST/46 powered "small version" Tempest. It pulls hard all the time. I have flown it in winds that no one at the field would fly in.  In the wing hard corners don't feel safe with .015's.
Ed

[peabody]

Howard has the right idea....

[PJ Rowland]

We flew my Bomber with 018 lines - 21's felt like rope, 15's felt a bit stretchy!

Having said all that, I flew the Gieseke Nobler / .61 on 18's and it was the best move I ever made, Trimmed out all my positive torque roll.

18's are fine.

[proparc]

I still use .018 on my ST/46 powered "small version" Tempest. It pulls hard all the time.
Ed

Send that Tigre to me!!!

[john e. holliday]

I too tried the .012 on my .25 size planes.   Went back to .015 as it gave me better control feel.   Maybe I need to make a set of .018's for my .46 powered planes.   Even my .40 size planes feel mushy at times.

[Trostle]

I know you weigh your slime-powered plane with the tank empty -- does one weigh ones electric sans battery?

Tim,

I am assuming you are asking a serious question.  The rulebook for CLPA is quite clear.  The table that specifies line length and diameters has the statement:

"Electric powered measured model weight includes weight of batteries."

[Chris McMillin]

I've never had a tank of fuel weigh as much as my 5or 6S batteries!
Chris...

[jim ivey]

does anyone know how many pounds centrifugal force a model pulls in flight?

[Brett Buck]

does anyone know how many pounds centrifugal force a model pulls in flight?

m*v^2/r

   

[phil c]

you need to get the units right to get a useful answer. It's easier to use a line pull calculator.

Just as a guide,  a 60 oz. stunter on 65 ft. lines will pull about 12 lb. in level flight.
A 48 oz. Nobler on 60ft. lines will pull about 9 lb.
Both are pulling well under half the yield strength of the lines, which is good.

A fast combat plane, about 1.5 lb(with fuel) will pull about 19 lb. at 110 mph.  It really ought to be using .021 lines, or get the weight down to 20 oz(with fuel) which is nearly impossible for a competitive plane.

[Tim Wescott]

you need to get the units right to get a useful answer. It's easier to use a line pull calculator.

Just as a guide,  a 60 oz. stunter on 65 ft. lines will pull about 12 lb. in level flight.
A 48 oz. Nobler on 60ft. lines will pull about 9 lb.

You mean an 0.12 slug stunter on 65 foot lines, traveling at about 88 ft/second?  Why, that's as easy as pi!

(Clearly the world needs some demented individual to come up with a nomograph)

[Chris McMillin]

You fly fast!
Chris...

[Dan Bregar]

To an old combat flier who is used to seeing half a dozen flyaways a contest, you folks seem pretty conservative.  The old rule worked fine.  Now we have to go to the bother of weighing airplanes at each contest, just to be consistent between IC engines and electrics.  A simpler solution would have been to outlaw electrics. 

Another solution would be to outlaw OLD combat flyers till they learn to  weigh their airplanes.  

[Trostle]

(Clip)

(Clearly the world needs some demented individual to come up with a nomograph)

Bill Netzeband generated those nomographs in his series of articles "Control-Line Aerodynamics Made Painless", American Modeler, Jul/Aug 66, Sep/Oct 66 and Dec 67.  Bill expanded on information gathered by others, some of the most significant from Pete Soule.  With the information and nomographs Netzeband published that essentially encompasses all types of CL models,  Reynolds Numbers of the lines can be calculated, a coefficient of drag for the lines and the drag of the lines determined, centrifugal force determined and then the appropriate leadout position relative to the CG.  There are computer programs available now to do this, but I would venture many of those programs are based on the work laid out over 40 years ago by Netzeband and Soule.

Keith

[Paul Smith]

I know you weigh your slime-powered plane with the tank empty -- does one weigh ones electric sans battery?

To be fair about it:

We weigh ours with an empty fuel tank.
You are welcome to use an empty battery.

[Brett Buck]

Bill Netzeband generated those nomographs in his series of articles "Control-Line Aerodynamics Made Painless", American Modeler, Jul/Aug 66, Sep/Oct 66 and Dec 67.  Bill expanded on information gathered by others, some of the most significant from Pete Soule.  With the information and nomographs Netzeband published that essentially encompasses all types of CL models,  Reynolds Numbers of the lines can be calculated, a coefficient of drag for the lines and the drag of the lines determined, centrifugal force determined and then the appropriate leadout position relative to the CG.  There are computer programs available now to do this, but I would venture many of those programs are based on the work laid out over 40 years ago by Netzeband and Soule.

   Certainly, although the nomographs were not very accurate, if not outright wrong, at least the first versions. Pete Soule's website (formerly Geocities, but who knows now) had the full results with correct data, and the same results were correctly calculated by LINEII which Bob Reeves then ported as LINEIII.

    What LINEII does is calculate the offset angle of the lines for a given line, speed, air characteristics, and weight. As it turns out, it is a *very weak* function of speed, that is, the line offset hardly changes with speed. That might be counter-intuitive but the drag and centrifugal force both rise with the square of the speed so it tends to cancel out. In all fairness, using it to set the leadout position is not the original intent, and it certainly debatable and not everybody even buys the underlying principle. *I* think it's the right way to go but it presumes that you want to trim the airplane like I do, and to fly tangent to the circle.

     Brett

[50+AirYears]

Hey, a fuel powered plane gets lighter as the flight proceeds.  An electric stays the same weight for the entire flight.
Funny the difference line size can make.  For years, I flew 1/2As on 32 to 35 foot Dacron.  Then one day, buddy at Wheelus AFB offered to let me use a set of 42' .008 stranded.  Now, I dont even use Dacron for lead-outs.  Planes were faster and more manueverable.
Heaviest lines I ever used was a bit unusual.  Also at Wheelus, I joined a pair of Sterling Oak weight balsa P-51 Profiles to make an F-82, sort of, and put my pair of Fox .35s on it.  For some reason, I decided I wanted to go to 70' lines.  BX only had .012 stranded in that length.  So, I used 2 sets.  I think it was the right choice.  Also, I don't think I ever got more than 3 flights on any given day wih it.  It was quite a load for somebody 5' 7", 145 pounds.  Kind of also wished I had available 2.5 or 3 ounce tanks instead of 4 ounce.

[PJ Rowland]

" *I* think it's the right way to go but it presumes that you want to trim the airplane like I do "

You mean correctly...

[Howard Rush]

There are computer programs available now to do this, but I would venture many of those programs are based on the work laid out over 40 years ago by Netzeband and Soule.

Or over 300 years ago by Newton.

[Brett Buck]

Or over 300 years ago by Newton.

   I expect that Newton missed the Reynolds number effects (that changes radically over the radius), given that Reynolds didn't invent it until 1883. That's what they missed in the original version of the analysis upon which the nomographs were based, from what I am told. Later they got that right and that was reflected in a later paper and then LINEII.

    A lot of the history was on Pete Soule's old Geocities site, but I that one is dead and I can't find anything that looks like it was migrated somewhere else. It was really great!

    Brett

[Steve Helmick]

I know you weigh your slime-powered plane with the tank empty -- does one weigh ones electric sans battery?

If you'd showed up at Thun field...oh, wait, you did. But anyway, it's common practise to accept the flier's statement about the weight of their plane, so you really don't often have to weigh it at a contest. If you do have to weigh it, it's a minor inconvenience. As far as weighing with/without the fuel/battery, it's in the rules. You are not required to load the electrons prior to weighing, just the container.    Steve