>Gidday,
>
>Is it possible to make the trailing edge of the fin's tip radius such that
>it will blend exactly into the rudders? I only have the tail and wing kit
>manuals at this stage and am not privy to how they mate together. I would
>really like to be able to place a straight edge 1/2 on the fin and1/2 on the
>rudder, and transition it up over the tip of both, having both match!
>Any tips! Please
>Regards
>Tony Renshaw
It is so long since you asked this I thought I'd better keep your whole note.
This is probably the only area I have studied in any depth. This was because
my rudder close-out block slipped about (0.8 mm at max) so I sanded-off the
spare & was concerned that my close-out cavity would be too small. For all
practical purposes, the specified 25mm radius on each top corner of the fin
converge at the trailing edge to form a semi-circular shape which matches
the profile of the top edge of the rudder.
I improvised the action of the hinging of the rudder to the fin by
drawing the shapes of the trailing edge of the fin aperture at tip and root
(measuring the actual sizes) on a thick pieces of card (the back of an A4
note pad). In each case I cut one straight side and the semi-circular 'arch'
but only scored the other straight side and bent it through approximately
90deg so as to simulate the hinge. (I actually about 1mm off the line to
allow for the thickness of the card) Next I held the inner flap against the
rudder core with the scored crease along the hinge line as near as I could
guess. Then by trying to bend the simulated fin close-out on to the rudder
core I could understand how it would interfere. I believe the rudder
movement is 30 deg each way so I have made a shallow 'step down' (with a
steep ramp) in the top edge of my fin core to give app 5mm clearance to my
template as it swings through a little more than 30 deg. If it works out
right I will avoid having to 'fabricate' a lump off my rudder AFTER the
lay-up. Hopefully it will also result in a small neat shape. If I have got
it 'wrong' I will be no worse off than if I had not tried. Watch this space
but DON'T hold your breath. I demonstrated to myself that there is no
interference problem at the root (bottom) of the rudder.
To answer your question:- I think that it is impossible to avoid a small
notch in the 'horizon line' of the fin + rudder at their junction but not
enough to be noticed from more than a few metres away otherwise the
transition should be a straight line.
If I this is not a) Not clear and b) Still relevant: come back & I
will send you a photocopy of my template and some sketches.
Eric Evers
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