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Author Topic: narrow prop  (Read 1051 times)

Offline bob whitney

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narrow prop
« on: June 22, 2018, 11:33:33 AM »
Got my BMJR SUPER CHIEF done 4 days before leaving for Brodaks.i put a K&B 4011 ,40 in it .set it up with a custom fit ring ,.215 venture and a Hemi Head and 3 head shims ,not sure of the thickness. with the reg wide blades I could not get it over 5 sec at where the engine wanted to run on 64 ft lines.  I installed a 12x5.5 narrow blade prop copied from a Randy Smith prop and instant a rich 2 stroke run with 5.2 laps and no rev up .it was good enough to get me a 2nd place in expert old time phase 2. we have been using the same prop on everything from LA 40's to ST 46's with good results but had to get slapped up side the head to try it on the K&B  HB~>
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Offline Air Ministry .

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Re: narrow prop
« Reply #1 on: June 22, 2018, 07:34:34 PM »
Gotta Picture ( of the prop ) . Regularly ran the old 70 torpedo ( same engine ) unmuffled on a 11 x 5 in the SM 72 . unless you got it a turn lean ,
One Turn instead of TWO on the needle ,  ??? it was fine .
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Offline bob whitney

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Re: narrow prop
« Reply #2 on: June 23, 2018, 12:22:42 PM »
for some reason my pictures are too big to post here
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Offline Dennis Toth

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Re: narrow prop
« Reply #3 on: June 23, 2018, 12:27:48 PM »
Bob,

What prop/pitch were you running before the change? I have run the APC 11x5 on my K&B 40 in the YAK YAK and it liked it. I am running the stock head no extra shims, 0.250 venturi, ST NVA, 10%N, 23% (50/50) oil, tongue muffler, set for a rich 2. 

Best,    DennisT
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Offline bob whitney

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Re: narrow prop
« Reply #4 on: June 24, 2018, 08:34:48 PM »
tried rev up 12/6w and a rev up 13/5
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Offline Dennis Toth

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Re: narrow prop
« Reply #5 on: June 25, 2018, 07:50:22 AM »
Bob,
When Les McDonald used the K&B 40 I believe he wound up running a 10 1/2 x5 in a 4-2-4. I think as a stock engine pulls better in a rich 2 with a lower pitch prop like the 11 x 4.5 ish. Also can take higher nitro in this setup.


Best,    DennisT
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