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Author Topic: 4-bladers  (Read 1222 times)

Offline rustler

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4-bladers
« on: December 04, 2007, 03:05:13 PM »
I hear the rule of thumb for 3 bladers is 1" less dia. than a 2-blader. Any ideas for a 4-blader?
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Ian Russell.
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Offline Ralph Wenzel (d)

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Re: 4-bladers
« Reply #1 on: December 04, 2007, 03:10:05 PM »
1" additional less diameter and/or pitch, depending on the plane/engine combination make a good starting point. Experimentation WILL be required!

Ralph
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Offline joe renfro

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Re: 4-bladers
« Reply #2 on: December 04, 2007, 09:24:13 PM »
And of course any increase in the number of blades increases proportionally the chance for the extra blade to
snap you very smartly on the top of your knuckle or 2....I can remember using a tri-bladed prop on an Enya many moons ago...I think I still have traces of that scar...But when you are young and foolish..one is also bulletproof..Now thats funny!
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Offline don Burke

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Re: 4-bladers
« Reply #3 on: December 05, 2007, 10:23:21 AM »
The definition of middle aged is when you realize you are no longer IMMORTAL! LL~

As far as finger strikes, that's why electric starters were invented.  HB~>
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Offline rustler

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Re: 4-bladers
« Reply #4 on: December 05, 2007, 04:47:37 PM »
Thanks guys. I think this may be the way to go for these larger engines now coming on stream. Otherwise it's going to be either ground clearance probs or v. tall u/c's.
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[I can remember the schedule o.k., the problem is remembering what was the last manoeuvre I just flew!].

Offline gary tultz

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Re: 4-bladers
« Reply #5 on: January 19, 2008, 06:29:05 PM »
Four bladed props. One more reason to learn the "Back Slap" starting method.  y1 H^^
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Offline RandySmith

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Re: 4-bladers
« Reply #6 on: January 20, 2008, 10:53:42 AM »
Quote from: rustler on December 04, 2007, 03:05:13 PM
I hear the rule of thumb for 3 bladers is 1" less dia. than a 2-blader. Any ideas for a 4-blader?

That is a good rule for props of the same  blade size area, however  it will depend on who makes the  3 blade, there are many 3 bladers that you can run the same  size as the 2 blades, some are higher aspect ratio blades  and turn pretty easy.
Best to try them first before cutting...you can always make the blades  smaller, but it's a little hard to make  them longer  ;D

Randy

Randy
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Offline Bill Little

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Re: 4-bladers
« Reply #7 on: February 01, 2008, 10:18:09 AM »
How about *4 bladers*, Randy? ;D
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Big Bear <><

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Offline Randy Powell

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Re: 4-bladers
« Reply #8 on: February 13, 2008, 02:22:22 PM »
I suspect that Randy's outlined rule for 3 bladers still applies. If you have a 4 blade that is long and narrow with a flat back, probably out to try it first before cutting it down. It will depend largely on the engine and the design of the prop. I've only used a 4 blade once and had some GP problems. I didn't fool with it long enough to sort it out, but I did like the traction it provided. Very cool.
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Offline RandySmith

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Re: 4-bladers
« Reply #9 on: February 13, 2008, 04:53:35 PM »
Quote from: Bill Little on February 01, 2008, 10:18:09 AM
How about *4 bladers*, Randy? ;D

HI Bill

Randy's post is correct, many 4 blade props are high aspect ratio and thin. People making 4 blades by just screwing  or milling slots and  putting  2  wood props together  are most likley going to need to go at least 1 inch down size, and maybe even up to 1.5 to 2 inches.  This will depend on how easy the prop turns.
Interesting , I have found 4 blades to drive very good and give a "turbine" like feel to the motor-plane..however they are very noisy. Some will really howl.
Stick with an odd number of blades if you want quiet! even numbers are much more noise

Randy
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Offline Bill Little

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Re: 4-bladers
« Reply #10 on: February 13, 2008, 07:24:44 PM »
I was just musing over the Parrott P-47 with a certain ST 46 that you know about.  It would be interesting to me to try a 4 blader on that one.

I didn't hear back from you about the message i sent..... ?? ?? ??
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Big Bear <><

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