I think it would make the already-difficult task of finding flying sites for contests harder yet.

Joshua
The correct measurement is from the centerline of the grip of the handle to the centerline of the model shall not exceed 70 feet.

Clancy

Jim

"I think that you may be looking at the use of larger scale models incorrectly."
"The selection of a subject that will perform properly under the current rules is probably more of an issue."

I did not say that the rules purposely discourage large models, I think that the 70 ft limit is un-intentional limiting factor. however, if one has to select a subject that will perform properly under the rules - does that not constitute a limitation?

 "The rules limitation to the line length does not really limit the use of larger models."

How is that? If I wanted to build a model with 100" wingspan that weighs 20 lbs and flys at 40 mph - I will still be subject to a line tension of 30 lbs! Do you consider this to be reasonable?

 "I saw the two four engine planes crash at the Nats last year. I don't know what they weighed, but both of them were of a scale that utilized a very high aspect ratio wing."

I have seen both models fly at Brodak. My impression was that the pilot was straining in the circle. If it was me, I think that I could hardly wait for the end of my flight, certainly would not enjoy it.

 "....but it takes a lot more speed and effort to keep them airborne."

My point exactly. Had the lines been longer - the pull would have been reduced considerably!

 "The most successfully flying scale plane that I have built weighed 13 pounds. However, it also had 6-1/2 square feet of wing area. It had great wind penetration because of its weight and it flew like a pussycat on 65' lines. Once in the air, I flew it at about 1/3 throttle with very little pull on the handle."

The wing area has nothing to do with the pull. The only parameters that affect centripetal force are weight, speed, and line length. If your model flew at say 40 mph than it pulled approx. 21 lbs. NOW: If you tell me that 21 lbs pull is comfortable, than I am really happy and relieved to hear this. I eagerly anticipate your assertion of this (seriously).

"It was not horribly heavy (about 5 pounds), but it had an extremely tapered wing at a rather small scale (48" wingspan). In retrospect, at such a small scale, I believe the extremely small wingtips on the model did not offer much to the flying ability, adding to its demise."

High taper ratio is not necessarily a formula for trouble. Low Aspect Ratio combined with small wing area and heavy model could mean high landing speed as well as relatively high cruising speed. I assume that with 48" span the wing loading was quite high which would entail rather high landing speed.

"The rules are what they are."

True indeed. However, if they were made so arbitrarily with no thought to encouraging variety - that may contribute to the sad state of affairs in CL Scale. I am curious: How many people under the age of 40 do you recall seeing participating in last year's Scale Nats?

 "Part of the secret to having a competitive scale model is to select a subject and scale that will perform well within the rules."

Again, this is what I see as limiting creativity. If this is indeed the key to success than pretty soon I would expect everyone to fly the exact same model.

 "A lot of us (me in particular) fall in love with a plane and build a model of it just because we like it."

This is how it should be in my humble opinion.

 "We find out after the fact that just because it was a good looking plane does not mean it will be a good performing model."

Or - could it be that had there been a better rationale to the rules, that model would not be at disadvantage?

 "I believe that larger models can be used as long as their wing loading can be kept within reason and they can be flown on 70' lines (or shorter. The 70' rule does not exclude larger models."

Again, wing loading has nothing to do with line tension. You can build a 48" wingspan model that weighs 20 lbs and powered by a 120 engine. The thing will fly like a bat out of hell on 65 ft. lines and pull 75 lbs at 60 mph. Would you care to try that?

To sum my thoughts up I would like to suggest this: Just as pull test is a function of airplane weight, why shouldn't the radius of the circle be a function of the model size, making it more condusive to different size models? I can and will build a 100" wingspan model that weigh only 15 lbs. Yes, I can handle the line tension, but: The circle will still look awfully crammed with such a big model. If the circle was say 90 ft radius, it would not hurt anyone wishing to fly 70 ft. lines or less, but, help those who like to fly something different and bigger.
Just my 2c

Joshua

Clancy

Can you explain please what you mean by "the centerline of the grip of the handle"? I have no problem understanding what the airplane's centerline mean, but, this is a little nebulous to me.

Joshua

Joshua,

I think you have brought two issues to this thread:

1.  The first was regarding the maximum length lines allowed by the AMA CL Scale rules.  I think it has been mentioned already on this and other threads is that most control line venues are set up to handle models that are flown on lines no longer than 70 feet.  And most dedicated venues have a safety allowance beyond that 70 foot radius.  In "most" CL events, 70 feet is a "practical" limit, though some may argue that Class C Speed and Jet Speed would be more safe if longer lines were allowed as well as comments similar to yours that "large" CL Scale models could also be more practical (and safer) if allowed to use longer lines.  Regardless of those arguments, the fact that most dedicated CL sites are set up to handle no more than 70 foot lines and the current rules reflect that fact.

This does not mean that a logical rules change proposal could not be submitted to provide for longer lines for larger models.  Such a proposal would have to be carefully crafted to satisfy all safety considerations and would recognize that lines longer than 70 feet would be reserved for models of some sort of minimum requirements based on weight, power, wing area and maybe wing loading.  (In my opinion, without very carefull considerations of these factors in such a proposal, that proposal would have some difficulty in passing the Scale Contest Board and any AMA safety review.  Yes, I know the argument could be used that longer lines for large CL scale models would be safer than the current 70 foot limit (given space is available), but the entire safety matter must be addressed.  Even if longer lines were approved, there would still be a "practical" limit, say 90 feet,  for any CL model.  Lines longer than that increase the risk of a line snagging on takeoff, or maybe require somebody to hold the lines at mid length while the model is released which means there is a person in the circle between the model which he has no control and the center -- not a good thing.  (Yes I have seen models flown on 100 and even 150 foot lines.  It is kind of neat with lap times in the neighborhood of 15 or 20 seconds.  But there are safety issues involved with this.)

The CL Scale rule book line length does not eliminate the possibility to run a contest with special rules, published in advance, that space is available and that longer lines would be allowed.  Such a deviation would probably have to have some sort of AMA safety technical review and approval before a sanction would be given.

2.  You asked about what is meant by "the centerline of the grip of the handle".    The CL General rules explain it this way:

"5.2. The length of the control system is measured from the center point of the grip part of the control handle (device) to the fore and aft center line of the model." 

So, regardless of how wide that grip part of the handle is, how long (the distance between the line clips) that grip part of the handle is, or how much bias/angle there is in the way the handle is formed and/or held, there is a center point on that grip part of the handle.  That is the basis to measure the lines.  (The amount of overhang or material in front of the grip, and the length of cables if used, and the length of the connectors between the lines and the handle attach points have no bearing on the position of that center of the grip part of the handle.)

Hope this helps.

Keith

Yes, "centerline of the grip" is a bit nebulous, especially with an irregular grip shape.  For that reason, I pushed through an F2D rule change to reword it to "inside face of the grip".  Thus, they can put the handle on a fixture with a couple of pegs and it's automatic.  But in F2D, there's total tolerance range of only 2-5/16".

The inside face of the grip is a more accurate way of measuring the maximum extent of the lines and it effectively shortens the lines about a 1/2" vs the centerline method. None of this means a thing unless absolute top speed is the goal.

In Scale all you have is a 70' maximum, not exactly rocket science.  I guess you could manipulate an extra 1/2" but fiddling the handle if you're that serious about it.

Here's a picture of a man flying a LEGAL model by current rules. Do you really want bigger and heavier models?  I sure don't.  Personally, I'd prefer going back to the old FAI limit of 5 kilograms (or 11 American pounds).  Then a few people wouldn't feel the need to spend a ton of money on huge planes and the tractor trailer rigs to transport them.  We can have a fair and equal contest with any limit we chose to impose.

I didn't order him to build an 18-pound airplane with four powered 25's.  The 70-foot line length has been around since the beginning of time.   We have to draw the line someplace.  Don't hold your breath waiting for bigger circles to be built to accommodate even bigger and heavier models. 

The existance of even a few ultra-heavies makes it harder for all of us to (honestly) sell the idea of safety to site owners. 

I don't know if you've been to the nats site, but there's no way any longer lines could be used where we fly scale and be safe.  I've flown at many, many sites in the midwest and can think of no place where longer lines could be used safely.  Even the old Columbus, Ohio site at the stadium couldn't have accommodated much longer lines because of the light poles.  So where do you want to fly?  Do they hold contests there?

Have you actually tried this?

I agree that longer lines will reduce the angular speed and reduce G forces at high speed.  But wait until you throttle down and try to land.  Those 80 or 90 footers will be dragging in the weeds or snagging flaws in the asphalt.

I am not suggesting that every site will be upgraded. Where I fly I could use 200 ft. lines if I wanted to. I do think that the AMA could afford a 90 or 100 ft. circles to encourage more participation in the the NAT's. Just my 2C.

I do not think the AMA would be interested in investing any money to enlarge the existing areas at Muncie for CL to accommodate larger circles or even one circle for the small chance of maybe having one or two models show up any given year where the pilot would like to use longer lines.

And has just been mentioned, there is a problem if the taxi option is used with a model hooked up to long lines.  There is an increased risk that a line or the lines will snag on some irregularity on the surface of the circle resulting in very serious complications regarding the airplane and safety.  I speak with some experience with this and have been chased around the center of the circle when one line snagged on a pebble embedded in the asphalt.  Yes, it is easier to keep the lines off of the circle if a big heavy airplane is hooked up to the other end, but the stopping and slow speed in the taxi maneuver can result in the lines draggin on the circle surface.

For most who do decide to build very large and very heavy CL Scale models, they should have contemplated the difficulty in flying such a model within the current restrictions of the CL Scale events. The 70 foot line limit found in the several CL events has been around for more than 60 years.  Yes, people have problems flying large/heavy models on 70 foot lines but that should have been considered before the time was invested in building such a model.  

With all due respect to those who fly large scale models and I have seen some of the best as built and flown by Fred Cronenwett and Grant Hiestand, I personally feel there is a practical limit for the size of a CL Scale model given the 70 foot maximum line length. What that limit is is something that the builder will have to personally evaluate by what he thinks is approaching just too much machinery flying around in the confines of a 70 foot radius hemisphere from a practical mechanical consideration and from a visual appearance perspective.  I think there is a problem flying any CL scale airplanes around in a visually small appearing circle and have what could be termed "realism in flight". The larger the airplane given the 70 foot line length limit, the less "realism" is a result. The limit for "acceptability" is simply something the builder has to establish in his own mind.

(I have seen a 4-engine Lockheed Electra that would pull its pilot, feet firmly planted and actually have his shoes slide on the paved surface of the circle. He later used a leather harness contraption with straps behind his shoulders so a helper could help anchor him in the center of the circle.  It was an impressive model and an impressive accomplishment, but hardly realistic unless the fact is blanked out in the mind of any observer/judge that it is turning in an improbable unrealistic short radius unbanked turn.)  

Now, if you want to have some fun, go fly Class II Carrier with a 3 or 4 pound airplane at 120 mph plus on 60 foot lines without the use of a pylon.  That becomes extreme and some enjoy doing it.  (I will not turn my back if I am near that circle.)

Keith

The biggest model I have built & flown is pretty small by Scale standards.  But let me throw this into the mix.

Line sizes and pull tests are computed via the "rock on a string" formula.  This formula ignores the downwind force on a BIG model on the downwins side of the circle.  Without numerical proof, but based on experience with my profile Bearcat (only 4 pounds with a strong .40), I can say the downwind force is significant.

Assuming the originator plans to build something BIG and in the 20 pounds plus weight range, the length of the lines will not relieve the lateral wind load on the downwind side of the circle.

In my opinion, the RCers have compromised modeling safety in general with their oversize overweight overpowered models.  I don't want Control Line to go down the same route.

RC clubs have been forced to buy or rent large fields out in the wilderness.  In return they often resort to high membership fees and dues.  In RC it is accepted that planes crash all over the place due to pilot error and equipment malfunction, thus those who practice "big RC" accept the need to travel to the free fire zone.

Control Line, on the other hand, operates on the assumption that all crashes will be physically contained within the arena.  Speed & Racing even supplement their hefty pull tests with a safety cage.

Are you willing to PERSONALLY pay for a big circle and a cage in which to fly your BIG CL project?

If you don't plan on entering a contest nobody will care how long your lines are.

But I don't think the length FOR CONTESTS will be increased within your lifetime.

Well, there will definitely be no change unless a proposal to do so is submitted.  And as suggested before, that proposal will have to be very carefully crafted to have any chance to be approved by the Contest Board.

Keith