Two control lines must be used. Each line shall have a minimum
thickness measurement of 0.38mm for both stranded & solid wires.
Stainless steel solid wires are allowed. Stranded wire must only
be 1x7 strand uncoated stainless steel stranded wire.
A minus tolerance of 0.011 mm is allowed.
My views:
NOW THE MOST FAR-REACHING F2C RULE CHANGE IN 38 YEARS HAS BEEN TAKEN
(The tank was reduced from 10 to 7 cc in 1967.)
Was this done with the eyes open to the consequences?
To me it seems NOT.
I find it therefore likely that this quite significant consequence was not discussed as widely as its importance mandates.
I do not mind a proposal stating that speeds have become unmanageable, and that something is needed to tame the event. A line increase taken after carefully considering all the ramifications would be fine with me. But it wasn't done this way.
As it is now, this grave change was sneaked in through the backdoor, the true consequences not declared.
Besides, the argument that solid wire is unsafe in wet conditions is invalid, as a good remedy is found: Applying silicone oil.
As the change in line diameter is roughly 75% of the one I assumed, reduce the figures to 75%:
A model doing 10 laps in 17.50 seconds on .30 mm will do it in 18.43 seconds. This is after everything is balanced for the new situation, range kept, and so on.
We will see heat times becoming at least 9 seconds slower. This will be after people have gone down the learning curve with existing equipment, suitably modified. But note the prospects for radical model design changes, mentioned below!
Wire is standardized in .1 mm increments, with the exception of mainly one country, USA, which uses inch standards. (Some manufacture to inch standards is still going on in some British Commonwealth countries as well.) The smallest wire available to most people of the world in compliance with the new rule is .40 mm. At a 5% line drag disadvantage! The specified dimension falls quite close to .015". An undue favour to the inch countries!
Some manufacturers might offer wire of the specified dimension, but the suitability is totally unproven. The links provided (in the clracing forum) have not shown that a suitable line material is available.
It is incorrect to refer to F2D multi-strand lines (.385 minimum), since the lines of choice for F2D competitors are those that don't break in line tangles, not the ones fastest. The ones in common use are of a diameter of .40 mm or more. Such an oversize is of course unacceptable to a F2C competitor. Further, if the rule mandates stainless, the only F2D line type I know of is the one that (probably) caused the outbreak of flyaway-itis in Sebnitz 2002. :-( I most certainly hope the rule makers didn't refer to this type!!
Although there exists grades of stainless that approach the tensile strength of piano wire, the commercially available stainless C/L wire has about half the strength.
*** SO WIRE TO THE NEW SPECIFICATION IS LIKELY TO BE LESS SAFE THAN .30 MM PIANO WIRE! ***
.30 mm piano wire will withstand at least 147 N = 15 kilogram force = 33 lb. Better check that the new wire isn't worse!
With .30 mm lines, the models have settled on a low aspect ratio, as this is the lightest configuration. This in spite of a larger portion of the lines being exposed than for a high aspect ratio. With .38 mm lines, it is possible that the balance will shift in favour of high aspect ratio designs, as the gain in covering the lines becomes higher. At the same time, competitors will stretch the limits of how much asymmetry can be housed under the "semi-scale" rule. Maybe we'll see 1.5-meter wingspan flying wings! -And our usual D-shaped wings being regarded as out of touch as tailplane models today...
Göran Olsson