Angier,
The original UD-3 caps (circa 1989) had a flat aluminum surface and a
nylon(? or teflon) wedge between which the o-ring was squeezed to expand against
the fuel opening neck. These were terrible.
Newer UD-3 caps (since about 1997) had both upper and lower nylon
wedges that squeezed the o-ring out. These are much better.
However, fuel or time may dry the surfaces so much that the o-ring doesn't
get pushed out properly on either cap type. Occasionally a squirt of
silicon lubricant on the cap moving parts and ring will help correct
that condition. It also makes it easier to close the cap tab. If the
cap is too hard to close, the roll pin axle can be sheared (I told you guys I
have made almost every possible mistake).
You can always buy fuel resistant o-rings to replace your old ones.
Also note that there was no part number change between the old and new
style caps.
Grayhawk
PS You have added a safety chain between the tank and the cap so it can't
be lost, haven't you?
In a message dated 8/17/2010 9:10:52 A.M. Central Daylight Time,
N4ZQ@comcast.net writes:
One of
my three fuel caps appears to have an O-ring which is stiffer
(header tank) than those on the wings. It closes ok but the tab no
longer sits flush with the cap surface. I'm wondering whether the O-
rings which came with the original kit are now beyond their useful
life. (not from flight time but build time)...
From your experience,
how frequently should they be swapped out in
the
field?
Angier Ames
N4ZQ
--
For archives and unsub
http://mail.lancaironline.net:81/lists/lml/List.html