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  #1  
Old 07-26-2018, 06:35 AM
Larry DeCamp's Avatar
Larry DeCamp Larry DeCamp is offline
 
Join Date: Apr 2010
Location: Clinton, Indiana
Posts: 692
Default Flop tube question

My project has a flop tube in the left wing. It will require extra elbows or sharp tubing bends to bring the tube to selector valve without routing it through the left footwell. Extra elbows are to be avoided due to vapor lock potential with FI.
The ship will only be configured for positive G aero (no inv’oil). So, is the extra elbows and bends a problem with FI ? I can convert to standard pickup or simply carry on with plumbing.
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  #2  
Old 07-26-2018, 07:41 AM
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Saber25 Saber25 is offline
 
Join Date: Dec 2010
Location: Colorado
Posts: 188
Default

Larry,

The flop tube is not necessary for positive G maneuvers. I removed mine some 20 years ago when I realized the heavy brass fitting was putting a wear mark on the bottom tank skin. The O ring failed and allowed metal to metal contact.

https://www.youtube.com/watch?v=P8uJYaJFst4

This was done with the normal fuel pickup.

Cheers, Hans
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  #3  
Old 07-26-2018, 07:56 AM
Michael Henning Michael Henning is offline
 
Join Date: Jun 2011
Location: Nashua, NH
Posts: 498
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I routed my fuel lines through footwell area with no issues of interference.
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  #4  
Old 07-26-2018, 08:09 AM
Larry DeCamp's Avatar
Larry DeCamp Larry DeCamp is offline
 
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Location: Clinton, Indiana
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Default Thanks Mike

Got any pics of footwell path .
Decamplarry@gmail.com
765-505-1160
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RV-4 fastback w/ Superior EXP 0360 /AFP & CPI
Clinton, IN
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  #5  
Old 07-26-2018, 07:19 PM
SJordan SJordan is offline
 
Join Date: Sep 2016
Location: Scottsdale, AZ
Posts: 169
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I forgot to switch to my left wing with the flop tube and rolled inverted. Engine ran for a solid 30-45 sec before losing fuel pressure. I don’t see the need for a flop tube unless you have full inverted oil and plan on spending minutes at -2g. FYI I have Standard Bendix fuel injection on a Superior forward sump.
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  #6  
Old 07-27-2018, 01:06 PM
TS Flightlines TS Flightlines is offline
 
Join Date: Apr 2010
Location: Ridgeland, SC
Posts: 2,169
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Larry---we've plumbed alot of inverted tanks for guys. At the tank we use a long drop 90* hose end that routes through the tank nose bracket and crimps to a teflon hose. At the side skin, we 'either' is a 90* bulkhead fitting to connect the valve lines or make a longer hose to connect to the valve with a grommet at the side skin. A bunch of them out there, no issues we've heard of.
Tom
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