Analysis of the new F1D rules

From: <ykleetx_at_gmail.com>
Date: 16 Apr 2014 10:11:24 -0700

Here is the exact wording of the reasons for the rules change in the proposal to CIAM:

 Reason: The proposal intends to significantly reduce the flight times because of the decreasing availability of proper flying sites. Nowadays only two (!) large sites are available for world (Belgrade and Slanic) and one (Belgrade) for European championships! Both sites are facing privatization which might results the loosing of both because of the renting costs. The class has to be flown in smaller sites with shorter flights and shorter contests to survive.
 The proposal keeps the surface loading in order to keep the beauty of the F1D models’ flying style. Besides the shorter times the 0,2 g addition to the model weight eliminates the effect of the only available heavier covering material, as the lightest plastic film is no longer manufactured since years. helps to make reliable variable pitch or diameter mechanisms and apply new, but heavier materials. Existing models will stay usable with 0.2 g spacers.
 Hopefully these changes might encourage new flyers as it would be a bit easier to build down to weight. The top flyers might keep their chances to win but the gap could well be closed. Test flights were flown in Cat. II site (max. 15 m ceiling height) up to 23 to 24 minutes flight times which means about 30% reduction.
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 There are two parts here for discussion:
 A. The proposal intends to significantly reduce the flight times
 B. ... because of the decreasing availability of proper flying sites
 To be more specific, B is the reason for making the rule change. A is the means (reducing flight time) that addresses the B.
 Reasonable people will discuss reason B and come to different conclusions. I will come back to this point in a future post
 Let's look at A. The new rule reduces flight times by
 1. reducing the motor from 0.6 g to 0.4 g
 2. adding the reduced 0.2 g back to the airframe weight (1.2 g to 1.4 g minimum weight)
 It is clear that 1. reduces flight times. The motor now holds 2/3 the energy.
 For 2., what are the other options?
 2a. 1.4 g
 2b. 1.2 g
 2a. keeps the overall flight weight the same as before, at 1.8 g. This means that the model would fly at the same speed, have the same sink rate, and experience the same aerodynamic loads. In addition, the 2/3 reduction in motor weight would translate almost directly into a 1/3 reduction in flight times.
 2b. would decrease the overall flight weight to 1.6g. This means that the model would fly at a slower speed, have lower sink rate, and experience less aerodynamic loads. This is a higher performing model than before. The overall flight time would be reduced, but not by less than 1/3. (I will provide the prediction in a follow up post.)
 The longer term consequence of 2a would likely be:
 - similar model size
 - similar cross section motor, similar prop
 - more weight added to prop, VP.
 - more weight added to all other components to make them sturdier and stiffer
 The longer term consequence of 2b would:
 - model size (not sure)
 - thinner cross section motor (because of lower wing loading), prop size (not sure), VP (not sure)
 - No more weight added to make components sturdier and stiffer
 So, which is better, 2a or 2b, in terms of minimizing modifications?
 Reasonable people may come to different conclusions. I would go with 2a.
 Given objective A (to reduce flight times), the new rules achieves this aim in a reasonable way.

Received on Wed Apr 16 2014 - 10:11:24 CEST