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I ordered a sharpened and balanced 40 mm prop, what I got is a s&b 38.5 what is the acceptable + - tolerance in the hobby. I have about 20 sets of props and this is the only one that’s not close to what it should be. Attachment 162921Attachment 162922
When a prop is s&b the diameter is reduced slightly, depending who does the prop and the size of it depends by how much. I have a 1457 that is actually 55.6mm but is exceptionally fast of my 45 rigger.
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40mm is as cast. By the time you balance it and then sharpen it. 1.5mm on the Diameter is not much, only 30 thousance of an inch per side.
If you wanted a prop finished to 40mm, you should have told them that, they would have started with a 42mm.
Larry
Even with the original casting the measurement is a nominal value. An actual measurement may show a slightly different value. Combined with the metal removed when sharpening a small difference in diameter is not uncommon. I remember a 60mm prop I ordered which measured 58.5 mm when received.
Of perhaps greater importance is a change or removal of much of the original prop’s trailing edge cupping. This may - or may not - greatly impact the prop’s effective overall pitch and thus performance.
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I see in your photo the prop is an octura and I don't know why but they all seem to be that way. I have quite a few of them and all measure smaller than the stamped diameter. All my prather, grim racer, or CNC props measure exactly as advertised. I wouldn't worry about it, it's just kinda the way they are and octura makes good props, probably the most popular brand by far.
Thanks guys now I understand how sharpening works. I thought that when you order a 440 you would get a 40 mm. But I get it the casting is 40 mm so by the time you sharpen it it’s smaller.
Is there a way to build a prop that will not over amp a system? I’ll keep it simple :doh:
Makes soo much sense now a caveman can do it !! lol :sinking-guy:Quote:
Originally Posted by royalcasa