Safe rpm limits, Cox gray props

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    Hi All : Is there a published chart for safe limits for the molded gray Cox range of props? I remember having run up a 7×3.5 on a .15 T/R
    engine, at around 19k and finding later that,that was a bit beyond their safe limit. I’m mainly concernd now, with sizes for 1/2A and the .061 “D.” TIA
    Cheers: deezildon


    Just saw this….

    I used to run the cox grey 7x 3.5 on my K&B .15’s and Super tigres and constantly turned them up to about 23K. Would I do that now? Probably not. They were a great design but a little brittle and you needed alot of them because of breakage after landings or DT. Fiber glass look a likes are probably available from the older FAI flyers as many were made and they are no longer being used….

    As far as the smaller props, go for it. I still use them on my 1/2A and let them turn up. Again, whoever designed them did a great job…

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