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