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  #1  
Old 04-04-2010, 06:14 PM
Phil Silvester Phil Silvester is offline
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Default Status Update from Arizona

Cozy IV construction still progressing in Mesa.
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  #2  
Old 04-04-2010, 06:48 PM
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John Slade John Slade is offline
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Default Re: Status Update from Arizona

Looking good, Phil.
It's come a long way since I saw it in your garage!
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  #3  
Old 04-04-2010, 07:53 PM
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kjashton kjashton is offline
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Default Re: Status Update from Arizona

Looks good. Looking at your vent lines: Do you have an additional vent in each tank back near the center spar?
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  #4  
Old 04-05-2010, 01:47 AM
Phil Silvester Phil Silvester is offline
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Default Re: Status Update from Arizona

The vent lines are per plans inside the fuel tanks. I just made them extra long so that I can run them over the top (inside the cowling) and exit on the opposite side under the spar.

John and Kent,

Thanks for the compliments. Progress is slow but steady.

Phil
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  #5  
Old 04-05-2010, 11:48 AM
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kjashton kjashton is offline
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Default Re: Status Update from Arizona

Quote:
Originally Posted by Phil Silvester View Post
The vent lines are per plans inside the fuel tanks
Well, the reason I ask is that the early plans I have did not include the second vent near the spar but if you don't install one, you'll vent fuel in the summer when parked on the ramp with the nose down. AMHIK

You can still install an AN elbow in the inside of the fuselage wall back near the spar and run one from there. If you want to join it with the other vent line, it must join at some point above the highest anticipated fuel level in any airplane position.

Call me "Blue Streak". :-)
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  #6  
Old 04-05-2010, 08:24 PM
Phil Silvester Phil Silvester is offline
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Default Re: Status Update from Arizona

Thanks for the info. on the nose down tank "burping" scenario. It's been a while, but before I closed out the Strakes I drilled some holes in the vent line just forward of the spar. I didn't take any photos, but I did the same as Wayne Hicks. His web site link is below.


http://www.maddyhome.com/canardpages...apter_21_5.htm

I think this should work. What do you think?
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  #7  
Old 04-05-2010, 08:29 PM
Marc Zeitlin Marc Zeitlin is offline
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Default Re: Status Update from Arizona

Quote:
Originally Posted by Phil Silvester View Post
... It's been a while, but before I closed out the Strakes I drilled some holes in the vent line just forward of the spar.

I think this should work. What do you think?
Drilling holes in the vent line effectively ends the tubing at the point of the drilled holes. Redesigning the vent system without an understanding of this isn't a good idea. If those holes are under fuel, then the fact that the end of the tubing is in vapor somewhere else is meaningless - the fuel will get into the vent line through the holes, and vent overboard with tank pressurization or fuel expansion.

There's a reason tubing doesn't have holes in it along its length.
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  #8  
Old 04-05-2010, 09:16 PM
Phil Silvester Phil Silvester is offline
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Default Re: Status Update from Arizona

OK, now what?

1/ Leave as is.

2/ Plug the holes.

3/ Use my fuel probe fitting as a vent.

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  #9  
Old 04-05-2010, 10:12 PM
Marc Zeitlin Marc Zeitlin is offline
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Default Re: Status Update from Arizona

Quote:
Originally Posted by Phil Silvester View Post
1/ Leave as is.
This effectively gives you one vent in the tank, at the back. This is good for when it's parked nose down, and bad for when you're climbing or level.

Quote:
Originally Posted by Phil Silvester View Post
2/ Plug the holes.
This puts you back to the plans configuration.

Quote:
Originally Posted by Phil Silvester View Post
3/ Use my fuel probe fitting as a vent.
Nope. Not anywhere near the top of the tank, and what would you put the fuel probe in?

Really what's needed, for the aircraft we've got that live in both nose high and nose low configurations is two or three vents - one at the back, at the highest point when grazing; one at the plans point for taxi/cruise; and one at the front in the climb configuration. You always want at least one vent to be in the vapor, not in the liquid.

I've got one at the back and one in the plans position. I still vent a little fuel if the tanks are really full and I'm climbing steeply.
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Old 04-06-2010, 02:24 AM
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ErlendM ErlendM is offline
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Default Re: Status Update from Arizona

With two (or even three) vents - do I connect them at the top of the turtleback or just before the exit under the strakes?

And many people talks about drilling a little hole in the vent-line at the top of the turtleback to prevent siphoning. If I have three vents in the positions you (Marc) suggested I really can't see how this could occur at all, as at least one vent-line would always be out of the fuel?
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  #11  
Old 04-06-2010, 10:45 AM
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kjashton kjashton is offline
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Default Re: Status Update from Arizona

Quote:
Originally Posted by Phil Silvester View Post
I drilled some holes in the vent line just forward of the spar.
Whoever initiated that idea wasn't thinking it through for all conditions. In a climb with nearly full tanks, the hole allows fuel to fill the line up to the fuel level and increasing pressure in the tank pumps the fuel overboard. But yeah, it works well when you're parked.

I suggest using your current line as a rear vent and install an AN elbow in the top of the rib between the storage area and the tank and run a vent line aft from there to vent the tank in a climb. If you want to join the two lines, they need to join above the fuel level.
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  #12  
Old 04-06-2010, 12:54 PM
Phil Silvester Phil Silvester is offline
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Default Re: Status Update from Arizona

The plans CH21 does have a stement in bold not to make any changes to the fuel system......

Thank you for the suggestions.

1/ Existing vent becomes the "rear vent" for parking attitude.

2/ New vent in baggage compartment bulkhead (as close to the top of the strake as possible). Is now the cruise/climb vent.

3/ Both vents will tee inside the cockpit above the fuel level.

4/ Vent location per plans on the top of the turtleback.
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  #13  
Old 04-06-2010, 01:07 PM
Marc Zeitlin Marc Zeitlin is offline
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Default Re: Status Update from Arizona

Quote:
Originally Posted by ErlendM View Post
With two (or even three) vents - do I connect them at the top of the turtleback or just before the exit under the strakes?
I didn't connect mine at all - I didn't see the advantage or point. I looped my vents up over the turtleback and down to the bottom of the strakes. This gives me a top point as high as I can get it to minimize the probability of siphoning, and protects from fuel leakage in the event of a rollover event.

I have no idea what joining them does, other than save a bit of 1/4" tubing. IF you're going to join them, do so at the highest possible level - not just slightly higher than the tank. There are a lot of dynamic effects involved in venting tanks, in turns on the ground, in the air in slips, etc. You should see the WK2 vent system :-).
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  #14  
Old 04-06-2010, 03:08 PM
argoldman argoldman is offline
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Default Re: Status Update from Arizona

Quote:
Originally Posted by Marc Zeitlin View Post
I didn't connect mine at all - I didn't see the advantage or point. I looped my vents up over the turtleback and down to the bottom of the strakes. This gives me a top point as high as I can get it to minimize the probability of siphoning, and protects from fuel leakage in the event of a rollover event.

I have no idea what joining them does, other than save a bit of 1/4" tubing. IF you're going to join them, do so at the highest possible level - not just slightly higher than the tank. There are a lot of dynamic effects involved in venting tanks, in turns on the ground, in the air in slips, etc. You should see the WK2 vent system :-).

If you use individually selectable tanks, joining the vents (l & R), as Marc suggests, serves little function.

However, if you are of the all on/all off persuasion, using a sump tank, a different scenario ensues. To prevent an unbalance of what amounts to Pitot pressure (into the vent tubes facing forward), which can, if uneven due to plumbing or vent location problems, it is, in my opinion, vital that these vent lines be connected together( L&R), including the sump tank (although there is some question about any advantage of venting the sump except for the first filling) at a highly located manifold from which the external vent lines go down and out. Doing this allows the pressure inside of each tank to equalize so there is little possibility of fuel transfer from a higher pressure tank to a lower pressure tank. Using a single manifold with 2 or more external vents coming off of it, also decreases the possibility of a vent blockage ruining your whole day. It does provide a single point failure area at the manifold, however logic (which isn't always correct) says that that area is much more difficult to serve as a blockage area.

Again, if you are of the L/R pursuasion.....Never Mind
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  #15  
Old 04-06-2010, 08:59 PM
Kraig Kraig is offline
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Default Re: Status Update from Arizona

Quote:
Originally Posted by Marc Zeitlin View Post
You should see the WK2 vent system :-).
What I would give to see any or all of WK2!!!,...

But since I live in New Mexico, I expect to see a lot of it. Just read a news article that the runway is 1/3 finished and the foundation and elevator/stairway shafts of the Spaceport are underway. Should be great to see it when they are done in about 1 to 2 years.

Kraig
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