We have been through that recently. From what I gathered, the lightening
holes are here because the wood and steel are dissymetric materials. It's
a question of elastic properties. Ideally, the WAFs should be tapered.
Since this is not practical, because of the spar construction mode, the
incremental lightening holes are there to act roughly as a taper.
If the WAFs tend to loosen (which I doubt, since I battled a lot to get
mine out), then the practical solution is to build the ribs in such a way
that the bolts can be accessed for a periodical inspection, and re-torqued
as required, every 5 years or so.
>From my opinion, the extra bolts would just be an overkill.
Now, again, it's your call.
Serge Vidal
KR2 "Kilimanjaro Cloud"
Paris, France
rhartwi...@juno.com
Envoyé par : krnet-boun...@mylist.net
2005-07-21 19:09
Veuillez répondre à KRnet
Remis le : 2005-07-21 19:10
Pour : kr...@mylist.net
cc : (ccc : Serge VIDAL/DNSA/SAGEM)
Objet : KR> WAF
Ref: WAF Modification
The drawings indicate that the UK mod is actually lighter than the R-R
WAFs. Each individual WAF fitting is made from 2 thicknesses of .063
steel (as opposed to one of .125 for the R-R). One is slightly longer
than the R-R fitting and one is considerably shorter. The long fitting
has 4 extra AN4 bolts running down the center instead of the 3 (so
called) lightening holes--the shorter fitting is a doubler at the wing
attach bolt and catches 2 of the extra bolts and four of the standard
bolts. There are four 3/8 inch alum bushings in the spar for these extra
bolts.
I have heard of WAFs loosening over time. Would putting the 3
bushed bolts down the center of a R-R WAF rather than the large graduated
lightening holes be an improvement? I do understand that there is an
engineering reason for the large holes. Comments from engineering
types??
Dick Hartwig
Waunakee, WI
rhartwi...@juno.com
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