|
Salutti tutti,
To anyone interested here's a picture of the
weighing of our LIV wing panel. There's a load cell just above the rope sling,
total weight registered was 120 lbs, total weight of the wing panel was 118lbs.
The flap weight complete with hardware and tracks is 9 1/4 lbs, the
aileron (balanced) just under 7lbs. so the weight of the one complete wing minus
micro and paint is just under 134 lbs (61 kilos). Micro and paint will add a
pound or three but with care it will be minimal. Haven't weighed the second wing
panel yet but expect it will be similar, the total wing weight then should be in
the vicinity of 270 lbs. (123 kilos)
From Martin Hollman's book Modern Aeroplane
Design Vol 1, the LIV wing design weight is 310 lbs, (140kilos) so
we are well under that weight, just goes to show what you can do when you
try.
A quick comment on wing incidence:
On my last LIV project....one of those fast build kits, the wing shear
box was installed with a twist so that the port wing had 0.3 degrees more
AOA than the stbd. After much discussion
with Lancair at the time the decision was made to remove the shear box and
reinstall it correctly...and Lancair credited the owner with the cost of
the work. It was heavy going with Lancair at first, their comment was along the
lines "we have massive jigs and it must be correct" ...but it wasn't, but
to their credit they came to the party.
(On a different, note on the current LIV we have a
gearbox problem, it looks like it was assembled with parts from the reject bin.
The centre diagonal parts in particular have rolling marks that have heavily
indented the metal surface and there are heavy scratches/gouges inside the
web...anodised over the top. After sending pictures to Lancair Tech the reply is
"the gearbox is fine, they all look like that now" This is the first time
in more than ten years of LIV experience that I've seen such a gearbox, if "they
all look like that now" I suspect the hired help isn't what it used to
be)
The LIV wing has a NACA 64212 profile at the tip.
From memory the ES has the same profile. The 64212 profile has a high
coefficient of lift but a sharp stall meaning that with just half a degree
more AOA past the peak, the loss of lift is about 0.1 from a maximum
coefficient of about 1.6. Also the wing design with 2 degrees of
washout is such that the wing root will stall first and the stall
should progressively move out to the tips with a further increase in
AOA. With the wing panel that has the lesser washout the stall will
progress out to the tip faster than on the opposite wing. When the stall has
moved outboard to the tip the opposite wing tip is still at or very close to the
maximum coefficient of lift, so with one wing stalled and the root of the other
wing stalled but still producing max lift at the tip.....think about it.
The accident report is likely to read "the aeroplane appeared to carry out an
aerobatic manoeuvre".
There's one such LIV accident report from Downunder
that reads exactly that. There's no proof one way or the other of what exactly
happened in the accident but the more I come to know of the LIV wing the more I
suspect that the wing is not tolerant of sloppy inaccurate
workmanship. Just for the comparasion I'm curious to know what the wing
incidence tolerance is on the big birds...Boeings etc. Does anyone
know?
Build 'em straight and light I say...
Ciao,
Roberto d'Italia.
|