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  • October 28, 2021, 02:38:49 AM

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Author Topic: .21 Sport Speed fuel tank style?  (Read 324 times)

Offline Dave Rigotti

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.21 Sport Speed fuel tank style?
« on: June 26, 2021, 07:00:36 PM »
I'm looking to build a .21 sport speed plane.  It's early in the design stage and I'm wondering about the fuel tank/delivery system.

What are the pros/cons of using crankcase pressure?

Same goes for a pen bladder tank. Pros and cons?

Thanks
Dave Rigotti
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Chesterland, Ohio

Offline Dennis Toth

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Re: .21 Sport Speed fuel tank style?
« Reply #1 on: June 27, 2021, 09:41:40 AM »
Dave,
Not sure why no one has posted a reply, must be all coming back from the NATs and need a rest. Anyway, I will give my two cents. The bladder approach is the simplest, slightly higher pressure approach. You need a fine needle valve thread, need to allow clearance inside the fuse for the full diameter of the inflated tank, the bladder could break but you can usually see this coming, need to fuel proof the inside of the ship, need to use a starter to start. This approach has been used since the 1950's and works. Crankcase pressure on the other hand has been used since the late 1960's. It allows the tank to be constructed within the pan and once the needle is set it should be close all the time. I believe you would use a coffin style tank with the pressure line located near the front as a uniflow. This is the same layout for straight suction. Hopefully some of the guys using this approach can jump in and show a sketch of the tank layout. Sizing is around 1 1/4oz?

Best,    DennisT

Offline Dennis Toth

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Re: .21 Sport Speed fuel tank style?
« Reply #2 on: July 03, 2021, 04:50:56 PM »
Does anyone have a layout plan that works for both suction and pressure. I've done the coffin type with the pickup  at the bottom of the front bend and the uniflow at the top of the tank just before the end of the pickup line. Vent to the top from the inboard side. Would still like to see sizes for different classes (oz?) and any alternate shapes that has been used.

Best,    DennisT


Offline BillLee

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Re: .21 Sport Speed fuel tank style?
« Reply #3 on: July 03, 2021, 08:08:45 PM »
Whatever shape you finally choose, keep in mind that a uniflow works whether it is pressure or suction. ....
Bill Lee
AMA 20018


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