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Fuel Tank Vent Line

dnimigon

dnimigon

Active Member
Back on the build again after a long break. I'm building the tanks and have most of the one done . Getting to the point of closing. Have a few issues with vent line. It doesn't say about drilling the hole for the vent line in the end rib. I looked around and all the ribs thinking I put one in wrong thinking one had a hole for this vent line but I didn't. Is this hole drilled near the top of the rib with no specific area as long as it's close to where the drawings show it. Also where does a person eventually vent this line once in the fuse. I kind of wonder why the vent line goes across the top of the tank and then drops down a bit before exiting the rib. Doesn't this create an area for fuel to get into which it will with fuel sloshing and plug the vent or will this line be vented downhill from their out the bottom of the fuse someplace.
 
If it's like the 7A. it works like your toilet. The line enters the fuse, goes up a bulkhead to the top of a fuse (thus preventing any exit of fluid), goes forward, down by the firewall and exits in the floor in a fitting that's cut and exposed to ram air pressure. (That last part is not like your toilet, thank goodness)
 
Dave,

Vent line goes across the tank because the highest point of the tank is the furthest outboard because of wing dihedral. Thus, this is where you want your vent line to start. As Bob said, eventually this will go into the fuselage to a high spot (higher than the inlet) that keeps any sloshing fuel from coming out. It is vented to the bottom of the fuselage so that if there is significant fuel expansion in a full tank, the excess fuel will drain onto the floor rather than bursting your tank, or draining someplace else that you don't want it to.

greg
 
what you've told me seems okay but what about the drilling of the hole in the rib for the vent line fitting. Am I suppose to just make my own hole. I guess also it doesn't make sense to me that the vent line goes down into the fuse, then up again before going back down. doesn't this trap fuel in the lower part of the line making it not venting then or am I reading this wrong.
 
dnimigon said:
also it doesn't make sense to me that the vent line goes down into the fuse, then up again before going back down. doesn't this trap fuel in the lower part of the line making it not venting then or am I reading this wrong.
Click to expand...

Any liquid in the lower part of this line will be sucked back into the tank or will be pushed back into the tank by the small pressure that feeds the vent in the air stream.
 
Dave,

Maybe this is a stupid answer, but if you are looking at the end rib adjacent to the fuselage, I would put a bulkhead fitting in there rather than just run the line through a hole and try to seal it. Obviously for a bulkhead fitting you also need a hole but of a different size.

greg
 
I think I figured it out from different pics. I was referring to the end rib of the tank that has the fuel gauge. The vent line exits the rib here using a bulkhead fitting. Just nowhere does it say anything about drilling the hole for the fitting or placement. I kind of went off the drawings and assumed this was okay having first drilled a hole big enought for the fitting. hope this correct.
 
You might consider buying the preview plans (the big thick notebook with all the plans) from Van's. It's really helpful to be able to see what stuff you're working on in a subkit ends up connecting to in another subkit that, perhaps, you haven't gotten yet.

It's also great fun to sit and sift through all the drawings.
 
Bob Collins said:
You might consider buying the preview plans (the big thick notebook with all the plans) from Van's. It's really helpful to be able to see what stuff you're working on in a subkit ends up connecting to in another subkit that, perhaps, you haven't gotten yet.

It's also great fun to sit and sift through all the drawings.
Click to expand...
Preview plans don't substitute for a finished airplane or advice from those that have finished one; I've ran into problem following the direction and plans.
 
Paul Thomas said:
Preview plans don't substitute for a finished airplane or advice from those that have finished one; I've ran into problem following the direction and plans.
Click to expand...

I didn't mean to imply they did. I'm just saying it's really helpful to see how parts we're working on in a subkit end up integrating with parts we work on on the next subkit. And it's fun to spend hours at night flipping from plans to plan.

Here's an example. When you get your fuselage kit, the first thing (this is for a 7A) they have you make is the firewall components, including a doubler for a fuel pump that, if you use fuel injection, you won't use. Then it will have you riveting pieces with rivets you'll have to drill out later in order to attach contactors, battery boxes, breather tubes, oil pressure hoses etc.

It's like putting a jigsaw puzzle together. Wait. Now that I think of it, I don't like jigsaw puzzles! :eek:
 
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