[Canberrauav] installing the main tank in the Porter

Andrew Tridgell tridge at samba.org
Mon Mar 17 11:14:03 EST 2014

Hi Grant and James,

James and I had a good look at different ways to install the main tank
yesterday afternoon. We found that there was really only one way that
worked well:


The install has the tank vertical, with the center of the tank about 6cm
behind the CoG. It just so happens that the height of the tank makes it
exactly fit both vertically (with enough clearance for the outlets at
the top) and horizontally between the two support spars in the top

The hatch I cut in the top fits neatly over the tank. It needs some
hinges or screws to hold it, but that shouldn't take long.

I think the main advantages of this layout are:

  - very little sloshing around of the fuel

  - the clunk is nicely at the bottom of the tank, and will allow us to
    use all the fuel, to the last cm or so

  - hopefully less chance of foaming of the fuel

  - tank can be held securely both top and bottom (its quite a snug fit)

  - minimal floor space used by the tank, so easier to install

I think the 6cm behind the CoG will actually be an advantage, not a
disadvantage. When the tank is full it will counter the weight of the
header tank, which is a lot further from the CoG than the main tank
is. As the tank empties it will tend to lead to a bit more forward
weight (as the header tank will still be full). So we will slowly become
a bit more nose heavy as we fly, but only by a very small amount. That
should not lead to any stability problems.

Grant, I hope you don't mind that I went ahead with the install of the
main tank without checking with you first. After James and I saw how
well it fitted in that orientation we thought it was the obvious way to

I'd like to put in a few extra wood supports, and a bit of strengthening
where I had to cut a support below the flooring, but it shouldn't take
much. Hopefully we can have this all ready for a 1hr flight this

Cheers, Tridge

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