Bob is quite right, I think that all of us fill up right up to the brim!
Of course the vent fills up too but this is not a problem in practice.
Best regards
Barry Tennant
ptag.dev@ukonline.co.uk schrieb:
> Hi! Fergus and all.
> I would venture to suggest that the purpose of the vent tube is also to
> allow you to fill up to the neck of the filler cap which even for a tail
> dragger will retrieve your 2.01 lost litres plus about another litre to
> fill the filler tube.? All IMHO of course. With a trike most of this
> problem is eliminated.
>
> Regards
> Bob Harrison kit337 G-PTAG.
>
> -----Original Message-----
> Behalf Of Fergus Kyle
> Sent: 28 May 2000 23:30
> To: europa@avnet.co.uk
> Subject: Measured tank capacity
>
> Today I measured my fuel tank, which was tagged as no. ,
> dated . This tank goes in an XS cockpit, and was levelled at
> its top to within 0.1deg of horizontal both laterally and fore/aft in
> the presumption that what is wanted is Fuel Remaining in level flight,
> which would be marked by a level headrest platform/tank top.
> As by Tony Krzyzewski, I added vegetable colouring to each measured
> litre of water and recorded its resulting depth in millimetres. I began
> by filling the port side section through the filling inlet. When it was
> full, the water began to fill the starboard section. When both were
> replete, the combined level began to climb an increasingly wide common
> volume, until the sides became virtually vertical. The filling ceased
> when the bottom of the fill inlet was reached. From this I gleaned the
> following facts:
> (1) The two side sections join at approximately 153mm=22 l;
> (2) Each side measured almost identically from top to 153mm.;
> (3) The four sides of the tank became almost vertical at +/-190mm.=28.3
> litres;
> (4) From there upward, the curve became virtually linear to bottom of
> filler inlet, 286mm.=45.4 l;
> On the grounds that linearity (or nearly so) could be extrapolated, I
> concluded that the Top of Filler would be reached at 326mm.=52.4 l and
> that the Bottom of the Vent Boss would be reached at356mm.=56 l.
> I then tipped the tank back to filling attitude (Noseup of assumed
> 7deg) and caught the outflow from the inlet boss. The loss of volume
> amounted to about 2.0 l. From this I calculated, rightly or wrongly that
> the max volume one would want on board at refuel would be 54 l. before
> affecting the vent line.
>
> If you wish to duplicate my graph of Fuel Remaining, and see the
> effect
> of tank shape, follow the steps below:
> A - Draw on a graph narrow side left to right, 60 - 0 squares (base is
> litres), and up the left side, 0 - 400 units (depth of fluid);
> B - Plot the following (litres - mm.): 54-354, 54-343*, 50-318, 46-300,
> 40-258, 32-200, 28-188, 26-180, 23-160, 22-153, 21-132, 17-95, 15-65,
> 13-35, 11-0, then go vertical to 11-153, 10-144, 8-120, 6-95, 4-65,
> 2-35, and 0-0 near the bottom right corner.
> C - Join the points smoothly where required.
> NOTE:
> The curve represents Fuel Remaining in Level Flight. By playing with
> the figures and assuming pessimistic errors, I cannot believe the curve
> is anywhere in error by more than about one litre.
> At about 153mm., the curve changes to reflect the depletion of Port side
> only (about 11 litres) with 22 remaining. Thus the second cusp.
> AT (OR BEFORE!) 11 litres remaining,THE STARBOARD (RESERVE) SIDE SHOULD
> BE SELECTED, unless you have Nigel Charles' excellent scheme of backing
> up with automatic-pump. That's why the vertical line at the 11 - litre
> mark.
> If you would rather have the raw measurements to acquire your own
> graph, I can send same.
> Bouquets or Brickbats,
> happy landings,
> Ferg A064
>
>
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