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Speed,Combat,Scale,Racing => Speed Talk => Topic started by: Paul Smith on June 07, 2024, 07:15:22 AM
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I have witnessed (and been involved in) four Perky line failures on models that passed the current pull test. Like other speed and racing rules, the Perky rules were written long ago before speeds reached the current levels. Speeds of 120 and 122 from a standing start have been reported. This implies a PEAK speed in the 125 to 130 range.
The current rule is 25 G's with a maximum model wright of 23 ounces, which calculates a pull of 36 pounds. It has been accepted practice to forego the weighing and pull them all at 35 pounds.
The "rock on a string" formula, VV/R, computes to 31 pounds of line pull for a maximum weight weight model at 130 MPH. Thus, 35 pounds of pull test is barely any safety factor at all. It is accepted practice in AMA Speed and Racing to adjust the pull test to the current reality. Therefore I have made an Event Director decision to go put to 40 pounds at this year's Brodak Fly In.
While this pull test could break some lines and planes, the failures will be less costly than the alternative. Without doubt, the current pull test has been proven to be inadequate.
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if we would eliminate the whipping ,actual speeds would be around 110 MPH as shown by two of the faster planes last year .if the pull test was actually done it would be more than enough. maybe if my Perkys stay in the car there wont be any need to whip
why dont we just pull them 50 lbs and the one that doesn't break wins RAD
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This year I plan to limit flying to Thursday when everybody can attend together and keep a close eye on whipping and pull testing.
I did not notice any whipping, but I did see some pilots having trouble keeping up with the airplane. Going this fast on 52'-6" it's hard enough to keep up, let alone get ahead of the plane. We're talking about 2-second laps.
We have all seen or experienced some line breakage. Something must be done.
In the future maybe it will be 60' x .014" lines or 52.5' x .014'.
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Paul, It will difficult for us to get up there as we are committed to the combat event. What about Wed. PM as well?
Also, why not get a scale so we can weigh them and pull properly to current spec? TS
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OK. We had the event on Wednesday afternoon as requested.
Everything went smooth enough. No crashing or failures of any kind. Five men with seven planes.
Bob Whitney 115.9
Tommy Schaefer 112.1
Al Ferraro 105.6
Dave Hallas 103.8
Paul Smith 98.4
Closest to Average Al Ferraro
For the season we have 13 names on the report with Paul Smith closest to average and Bob Whitney on top.