Hello Everybody!  I am doing a little research on header tank venting ( no vent, one vent, two vents, etc.) and was wondering if anybody has any information as to how much air actually accumulates in a header tank during a "normal" ( i.e. mostly straight & level with some banking turns) flight.Any information would be appreciated.  Thanks!

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Hey Frank, check out this video from Skytek they built one especially for the zenith 750 has 2 vents very detailed video. i ended up making one myself that is very similar but it holds 2.5 gal.

https://www.rotax-owner.com/en/videos-topmenu/builder/425-750-4

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That's a neat header tank John!

I'm planning something very similar and have been looking at off the shelf 'fuel cells' that have a few fittings (I'll have to add more).

Could you please share the dimensions of your tank (either markup on your image or simply LxWxH)? I think 2.5 gal would be the sweet spot for me, specially because I'm concerned about aft CG limit with a Rotax engine. 

Hi John!  Thank you9 so much for the helpful information.  Grately appreciated.  I am combining information that I learned at Oshkosh this year with buildr's/pilot's experiences.  I'll post a short report on my findings shortly.  Thanks again!  Frank

Not a Viking issue, but I unport either right or left side (at the main tanks and thus the header empties) when less than 5 gal remains and I slip for an extended time.

That and the fuel stains from Zenith's terrible vent are the bane of my 750 existence.

Roger says he gets all but a few ounces out of the tank. I have done so with careful management, but I don't trust doing it with both tanks so I always have a 5 gallon reserve on one side.

Here is the dimension's for the header i built.

John 

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Thank you! I was sketching out something similar, although more tall than wide (making it easy for bubbles to rise up and finding their way to the vent outlets).

I also found this one which seems like a good size, probably slightly bigger. I might have to watch for CG problems but other than that, can you think of any reason why this might not work? I'll drill a couple of holes and attach fittings for fuel lines coming from the wings. I'm thinking I'll use the existing top fittings for vent lines, since they are slightly higher.

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