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McCauley Prop Info Needed

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  • #16
    Scott, I found the McCauley application guide paired with the McCauley TCDS for the hub series you are considering to be the key to figuring it all out. I'm willing to help if you want...though I'm far from an expert.

    The counterweight arrangement doesn't matter with wood core props because wood doesn't have a natural frequency like metal does. The counterweights are their to prevent the prop/engine combo to achieve a resonant frequency that will cause a blade failure. This frequency is dependent on the engine and prop blades. Simply changing the blade length will change the resonant frequency. A resonant frequency won't happen with with a wood prop.
    Scratch Built 4-place Bearhawk. Continental IO-360, 88" C203 McCauley prop.

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    • #17
      Originally posted by Scott View Post
      1. What is the real world advantage of a 3 blade prop?
      I’d go about 80” so quieter than an 84” two blade? More ground clearance? Quicker deceleration? What are the performance advantages/disadvantages? My understanding is slightly better static pull but slower cruise. Obviously 2 blades are less expensive, weigh less and are not as smooth.
      There are some HUGE threads about this over at the BCP forum. You know the key points already ^.

      Long story short, this discussion revolves around:

      Somewhere between 250 to 300 hp you pass the point where three blades become necessary to lay down the horsepower (transfer it to the air).

      + At 250hp, the benefits of three blades are appear to be less noise, much less vibration, more acceleration from standstill, more drag when you close the throttle, and more ground clearance.
      ~ There is more weight on the nose can help or hinder. Cruise speed will be more or less the same. We tested it and found it was 1kt slower - within the margin for error.
      - The big minuses are cost to purchase, cost to overhaul, and prop inertia i.e. slow throttle response time with a metal 3-blade.

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      • #18
        Three blade metal props on the front of a Bearhawk with a 540 result in a too forward CG which can be compensated for. But for me it is not the best way to go. Mark

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        • #19
          It is approaching time to buy a prop. I have been looking on a few sites for a good used Hartzell or MT for quite a while. I also tried to get info on the CATTO blades for a Mac hub but have never found anything on the subject other than this forum.

          Any update on the CATTO blades? It is not mentioned on their website that I can find, and googling only references this forum.

          I was thinking of going for a similar Mac that came on a late C-182 with a Lycoming, but not sure what counterweights I have on my Bob 540. It might just be too hard and I just buy a new Hartzell.

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          • zkelley2
            zkelley2 commented
            Editing a comment
            If you have a 2 or 3 blade MacCauley hub sitting around whirlwind can put their blades in it and save you a lot.

            I'm fairly sure the only hub that you really need to worry about the counter weights with is the compact Hartzell(all modern Hartzell hubs from what I understand). Or I guess I should say, I know that the C2XX seiries MacCauley can go on all the A-D 540s and I know the compact Hartzell requires a different counterweight arrangement for the A series than comes on then. I have the STC number for that written down somewhere.

          • svyolo
            svyolo commented
            Editing a comment
            I have a 540 and I think they only rate their 2 blade models to 210 hp.
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