"Eric Greenwell" wrote in message
...
Doug Hoffman wrote:
tango4 wrote:


yes it's 'normal' and yes it will affect performance

it needs fairing, filling and refinishing.

Ian


Yes. According to Richard Johnson a laminar flow airfoil not only needs
to
be accurate in shape , but it needs to have no "waves" larger than +/-
..002"
in 2", in order to extract best performance. If you can see and feel
the
bump of the spar you are violating both of these criteria. Fairing and
refinishing a wing, and making sure the airfoil is correct, is not a
small
task, but doable. I am (finally) finishing up my RS-15 wings. I know
the
shapw is accurate and I know the +/- .002" waviness limit is not
exceeded
(this is best checked with a dial indicator).

I thought Johnson's criteria was +/- .004".
--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA


R.Johnson states .003" to .004" peak to peak in Soaring May 1998
The contact of the gage is held in the centre by a 2" cart.
The Johnson measuring cart picks up only limited deviations info.
Longer wave can not be picked up readily and longer
waves can be just as detrimental if they exceed certain limits
(That is where attention to details and craftsmanship is so important.)
I would like to refer Doug to an article by Vic Saudek
"Airfoil Smooth-Curve Measuring" of 1987 in Soaring for further reading.
Regards
Udo