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  #1  
Old 06-19-2007, 07:59 AM
neverquit's Avatar
neverquit neverquit is offline
G.Norman
 
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Default Sump Tank Size and Location

I'm making the sumps for my Cozy and found the chapter a bit vague on the location. It's only logical to place them over the 1.25 hole but should they be as far forward as possible or should they go aft all the way to the firewall?

I thought of also drilling a 3/8 hole at the opposite end through the strake to allow fuel to enter during descents. It seems on descent there is a possibility of running the sump dry while having plenty of fuel in the tanks. Anyone done any good mods on these?
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  #2  
Old 06-20-2007, 04:38 PM
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neverquit neverquit is offline
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Default Re: Sump Tank Size and Location

What's the deal? Are there no experts out there to help on this topic?

Looks like the Cozy mail list again. C'mon guys, give this a shot.
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  #3  
Old 06-20-2007, 04:40 PM
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TMann TMann is offline
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Default Re: Sump Tank Size and Location

Plenty of experts ...... but not a lot of help.
Can't help you on this one ........ my Long-EZ does it quite different.
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  #4  
Old 06-20-2007, 04:43 PM
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John Slade John Slade is offline
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Default Re: Sump Tank Size and Location

I saw a good discussion on this and thought you got a good answer.

Ah! I know. You asked the same question in multiple places at the same time, didn't you.

Bottom line, as I recall, was "no extra holes".
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  #5  
Old 06-20-2007, 05:05 PM
argoldman argoldman is offline
Rich
 
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Default Re: Sump Tank Size and Location

The Aerocanard (kit) uses a slightly different sump situation.

It uses a single 3 1/2 Gal sump (may be 2 1/2 but I think I am correct) tank which is located over the main gear bulkheads, the rear one being shortened so that the bottom of the tank is canted down in the rear. The two main tanks flow unrestricted and unvalved into this tank. The tank has a central baffle and has room on each side to access the feed tubes from the tanks. The inlets to the tank are toward the top of the tank and the pickup tube is orientated so that it is approx 1/2" from the bottom so as to create a water trap (with associated drain). There is a float switch to indicate if the tank is draining and fuel not being replaced. The plans specify no vent but there is a "burp valve" for the initial fillup to eliminate the trapped air. The concept here is that the fuel used is replaced by the flow from the tanks and thus no vent is necessary.

In mine, I think that I will run a vent from this to connect to the existing vents (in a manifold,) so that the vent pressure in all tanks can be the same. This will come in handy if I ever run the tanks dry and need to refill. I won't have to "burp" it with the ensuing spurt of gasoline in the innards of my cockpit.

Tanks, I gas that's about awl.
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  #6  
Old 06-20-2007, 05:17 PM
Nathan Gifford Nathan Gifford is offline
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Default Re: Sump Tank Size and Location

The discussion on the CozyBuilders e-mail list suggests that the problem does not exist on descents. However, in low fuel conditions, or rather, very, very low fuel (3-5 gals) conditions in a steep climb (20 deg) you can encounter fuel starvation. Dropping to nose to get 120 mph climb speed seems to rectify the situation.

On fuel injected systems I read someone is installing wet fuel pumps in the sumps (vapor lock?) but I do not remember who.

John, I know you did your system slightly different, but I do not recall you having a sump.
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  #7  
Old 06-20-2007, 07:12 PM
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John Slade John Slade is offline
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Default Re: Sump Tank Size and Location

Quote:
I know you did your system slightly different, but I do not recall you having a sump.
I made my sumps per plans except that I used threaded aluminum flanges from Wicks and AN fittings rather than just flox the pipes in place. Feeds go to pumps under the back seat, then through individual filters to a T just before the rail. After the pressure regulator the return is switch by a solenoid on the firewall to returns at the top rear of each tank. Engaging the left pump also engages the solenoid to switch the return left. If the left pump is off the return default's to the right. The only problem is possible vent overflow during take-off on both pumps with the left tank brim full. I've only done that once.

The rotary has much higher fuel flow than the Lyc installation because of the return. Even at idle the fuel is flowing quickly, so the sumps would drain quicker. Same would be true on high attitude climb (and this is tempting to do with a turbo). I've never seen any problems with fuel starvation, but this may be due to the fact that I wouldn't even dream of continuing a flight or, especially, taking off with < 5 gallons in either tank.

This discussion has been helpful, though. Knowing I'm probably more suseptible than most, if I ever am low on fuel I'll be on the lookout for starvation and ready to level off. A nice thing about a high pressure fuel system is that air will be expelled quickly when the backup pump is engaged.
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  #8  
Old 06-21-2007, 07:31 AM
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Default Re: Sump Tank Size and Location

Quote:
Ah! I know. You asked the same question in multiple places at the same time, didn't you.
Yes John as we all do. I'm guilty but I always give this forum first shot. I confess I've been to the nudie bar too.

Quote:
I saw a good discussion on this and thought you got a good answer.
Yes, of course always a good answer as expected, "keep it to the plans". Always looking for new, possibly better ideas.
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  #9  
Old 06-21-2007, 08:30 AM
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John Slade John Slade is offline
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Default Re: Sump Tank Size and Location

Quote:
as we all do
Not all. Just a few do that.
Quote:
Always looking for new, possibly better ideas.
Understood, but new ideas, especially in fuel systems, and lead to new problems. Unless there's a compelling reason to change it, the fuel system is best left alone.
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  #10  
Old 06-21-2007, 09:06 AM
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mplafleur mplafleur is offline
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Default Re: Sump Tank Size and Location

Quote:
Originally Posted by John Slade View Post
Not all. Just a few do that.
Understood, but new ideas, especially in fuel systems, and lead to new problems. Unless there's a compelling reason to change it, the fuel system is best left alone.
Your's isn't anything like "per plans".
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  #11  
Old 06-21-2007, 09:29 AM
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Default Re: Sump Tank Size and Location

I said "unless there's a compelling reason". High pressure fuel injection and returns needed for a rotary are a compelling reason - once you accept that the engine is going to be installed, that is.
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  #12  
Old 06-22-2007, 02:11 PM
chasingmars chasingmars is offline
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Default Re: Sump Tank Size and Location

Quote:
Originally Posted by neverquit View Post
I always give this forum first shot. I confess I've been to the nudie bar too.
What was their take on the aircraft fuel system question?
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