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Author Topic: 20fp  (Read 1454 times)

Offline big ron

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20fp
« on: July 28, 2015, 07:42:43 PM »
What is the size of the bore on a 20fp venturi
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John Blanchard
Brusly, Louisiana
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Offline Brett Buck

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Re: 20fp
« Reply #1 on: July 28, 2015, 07:51:23 PM »
Quote from: big ron on July 28, 2015, 07:42:43 PM
What is the size of the bore on a 20fp venturi

  6.5 mm/0.257"
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Offline big ron

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Re: 20fp
« Reply #2 on: July 28, 2015, 07:57:38 PM »
Thanks
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John Blanchard
Brusly, Louisiana
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Offline big ron

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Re: 20fp
« Reply #3 on: July 28, 2015, 07:59:40 PM »
Also is the thrust washer on a 25la the same as  the 20fp
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John Blanchard
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Offline Bill Johnson

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Re: 20fp
« Reply #4 on: July 29, 2015, 05:05:46 AM »
You might try a 6mm venturi. I used a 6mm on a 25FP last weekend. Mounted on a Ringmaster on 59' lines, I was getting 5.3 second laps with a perfect 2-2-2 run.

http://stunthanger.com/smf/index.php/topic,40075.0.html
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Offline Brett Buck

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Re: 20fp
« Reply #5 on: July 29, 2015, 08:58:29 AM »
Quote from: Bill Johnson on July 29, 2015, 05:05:46 AM
You might try a 6mm venturi. I used a 6mm on a 25FP last weekend. Mounted on a Ringmaster on 59' lines, I was getting 5.3 second laps with a perfect 2-2-2 run.

http://stunthanger.com/smf/index.php/topic,40075.0.html

   It might well be a good idea because even a 20FP is too much power, stock, for a Ringmaster. 6 mm might be a bit small for the 20, however. You need a smaller venturi on the 25 than the 20, since you can get more air/power through it with 25% more displacement, and you can't possibly use the full power of the 20 or 25 on a Ringmaster. We tried the 20, and running correctly with all the stock parts and an APC 9-4, it goes about 3.8 sec/lap on 60 foot lines.

     Brett

 
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Offline Tim Wescott

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Re: 20fp
« Reply #6 on: July 29, 2015, 10:23:32 AM »
Quote from: Brett Buck on July 29, 2015, 08:58:29 AM
We tried the 20, and running correctly with all the stock parts and an APC 9-4, it goes about 3.8 sec/lap on 60 foot lines.

I'm going to have to try mine again now.  It didn't seem that fast to me, but when I built it I was in the habit of going pretty quick.

Brett probably knows better than me, but on the bigger engines you can get the same effect of a smaller venturi by piling layers of nylon mesh onto the venturi intake.  This allows you to tune the "venturi size" fairly easily at the field when you're getting a new plane dialed in.
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Offline Akihiro Danjo

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Re: 20fp
« Reply #7 on: August 01, 2015, 12:10:42 PM »
Quote from: big ron on July 28, 2015, 07:59:40 PM
Also is the thrust washer on a 25la the same as  the 20fp

If you mean the drive washer, not the thrust washer, the answer is NO.
FP drive washer outer dia is slightly larger than LAs. This is the reason why APC 10 inch prop does not fit well on LA25.
Aki
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