>I'm in the process of making the fuel vent pipes. I have two pieces
>of stainless steel tubing, each 150mm long. I need to bend them
>through 90deg, drill 2 holes in the back and bond them into the
>fuselage. The manual has no dimensions for this and I guess it's
>not too critical but what have other people done?
>
>Dimensions I'm looking for would be:
>1. Length from vent forward tip to start of bend.
>2. Approx radius of bend.
>3. Height of horizontal vent tube above the fuselage skin
>4. How much tubing ends up protruding through the lower skin?
>
>Rough dimensions would be great if anyone has a few minutes to spare
Phil - I can't give you any dimensions as I haven't an example to
hand, but i can offer some observations.
When Tim Houlihan & I were preparing for the Europa Club tour of
Ireland last year, he was having a lot of trouble getting sensible
readings from both his sight gauge (exactly as the manual) and his
electronic gauge (which uses a pressure sensor like Tony K's but at
present has a different display device.
We fiddled about with the vent system, found and cured some leaks at
joints, but nothing seemed to improve the reliability of the
indications. By blowing or sucking carefully on the vent pipe on the
ground, we could demonstrate that the sight gauge and the electric
one were telling the same story. Aloft, both gave off-scale
indications at certain parts of the flight envelope - and my memory
is a bit hazy here, but it seemed that the fuselage angle of attack
appeared to affect whether we got sensible or silly answers. I don't
think we ever got around to it before getting fed up with test
flights, but I wanted to try taping over the holes at the back
because I suspected they were so close to the fuselage top surface
that they might have been going in and out of the boundary layer and
thus affecting the pressure seen in the vent pipe. Another test would
be to block the main end of the vent and leave the back holes open to
see how indications differed.
For what it's worth, I'm intending to use Graham Singleton's version
of the fuel system (with ali pipes) and have the vent pointing down
at the bottom of the fuselage (so that vented fuel from over-filling
goes on the grass rather than over the fuselage), which should also
eliminate any of the above issues. I'll tell you later if it doesn't!
regards
Rowland
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| Rowland Carson LAA #16532 http://home.clara.net/rowil/aviation/
| 1280 hours building Europa #435 G-ROWI e-mail <rowil@clara.net>
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