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Draining tank with cowl

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Andy Shailer08/02/2009 10:16:52
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what is the best way to drain the fuel tank,  from cab fuel tube when you cant get to it, because of the cowl. I did a see a plastic moulded product that has fuel tube runing on outside of cowl, but cant find the information anyway.
Many Thanks
Andy
winchweight08/02/2009 19:22:40
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I use a Dubro fuel valve. It fits in the carb fuel line and is a neat fitting that attaches to the cowl or the fuselage. You can refuel or drain completely through it, no mess at all as it draws from the clink line.
Andy Shailer09/02/2009 21:16:16
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Thanks for that Shaun, im looking into where to get them from.
 
Many Thanks
 
Andy
Martin McIntosh09/02/2009 22:46:14
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I normally drain from the silencer pressure line with the model inverted and the bung from the fill line removed; alternatively I use a system of tubes (four) under the model which consists of a `U` arrangement in the carb. line, a pressure release tube with a bung (in the case of crankcase pressurised systems - or otherwise) and a blanked off tube to park the clunk tube on when not in use so that the system is sealed  to prevent evaporation and fuel seepage. These are soldered or glued to a strip of printed circuit board or similar. Works well. Hope this helps.
Andy Shailer10/02/2009 20:26:55
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Thanks for that idea Martain.

Richard Duvall17/02/2009 11:21:49
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I picked up on the idea of using a fuel valve from this thread.  So I ordered one for the Chipmunk I am currently building.  I found one that was less than half the price of the Dubro version.   Now I've got it the problem is where to locate it! The only bit of accessible fuselage would place the valve behind the tank with the result that the fuel line onward to the carb would be something like 9 inches. Is this a problem?  I suppose I could mount it on the cowl itself but that would make the fitting and removal of the cowl more difficult, but one of the main aims is to avoid the need to remove the cowl.  I'm assuming that the 3rd tank connection just needs blanking off.
Martin McIntosh17/02/2009 20:51:02
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If not using crankcase pressure but only silencer pressure or none at all, you must keep the fuel line from the tank outlet as short as possible or the motor will have problems drawing fuel when the nose is raised. A fill valve fixed to the firewall on the underside would appear to be a good compromise since it will be out of sight.
Martin Harris17/02/2009 21:19:16
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Fancy meeting you here, Richard.  I'll post this here rather than your Chipmunk thread as it is just as relevant to this one...although parts will be Chipmunk specific.
 
I mounted my refuelling valve about an inch in front of the air intake on the rear of the cowl LH side where there is a circular hole on the full size for access to depress the carb float while priming.  It doesn't affect removal of the cowling as the valve is mounted on a small wooden structure attached to the tank box.
 
This doesn't extend the tubing very much at all.
 
It's a solution which avoids stressing the cowl as it sits just clear of the valve below and doesn't detract from the model's scale appearance in any meaningful way. 
winchweight18/02/2009 19:05:05
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Yep, block off the usual fill feed as you refuel, defuel and supply through the same line.
 
As for finding a space to put it - I used a piece of right angle aluminium from B&Q, the sort you might use to reinforce a corner with screws etc. I enlarged one of the holes for the valve, cut off the surplus material and screwed it to the bulkhead. It is secure and is unaffected by removing the cowl. You just need to drill a hole in the cowl to access it.
 

Steve Hargreaves - Moderator26/02/2009 15:01:14
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I fit a second clunk to my fill line (I always use a three line tank...fill/drain, silencer pressure, fuel feed) that way the fill line will always be able to draw fuel & you can empty the tank in the same way you would fill it.
 
I always find taking the fuel tube on & off the carb nipple eventually leads to leaks

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