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Craig,
Thanks for the info. Looks like you are way
ahead of me.
What I plan/hope to do is to get templates about
every 2 feet apart for the wing,
h. stab and (?) rudder. Get the contour right
at these points, then long board
in between.
Hadn't even thought about the incidence and washout
- not sure what I can
do about them anyway.
Doug
----- Original Message -----
Sent: Tuesday, July 31, 2007 6:12
PM
Subject: [LML] Template of Leading
Edges
- How close are we to the designed
airfoil?
I
have a IV-P, not a Legacy but my airfoils are very close to design intent.
I CNC machined three templates that are accurate to
design intent within .001". I made one template for the root,
one for the flap/aileron split and one for the winglet
split. I did not use feeler gages, but it was hard to see light
under the 3/4" wide templates. I feel the three locations were within
.03" of design intent and the
leading edge was much closer than
that.
- Is it possible that we may have
squeezed the wing too tight and made it too narrow or added
too much micro and made it too blunt?
- Can we get the correct airfoil by hand
sanding?
I
used a very long "long board". Three strips of sand paper
long.
- How do we know what the correct airfoil is - by
eyeball?
- Is there a better way?
I am thinking of "templating" my leading edges -
getting a template that is the correct airfoil and attempting to get the
leading edges as close to design as possible.
- Does this make sense?
- Am I wasting my time chasing 1 or 2
knots?
- What is the best method of getting the correct
airfoil?
- Has anyone else done this?
While the airfoil shape is very close, I was able to
measure incidence with the templates as well. The incidence was not as
good as I would have liked.
Here are my actual incidence inspection
results:
RH
LH
Spec
BL26.25 -1.764
-1.9705
-1.6
BL104
-.8033
-1.178
-.777
BL171
+.397
+.145 +.342
Washout 2.143
2.115
1.942
Results were obtained
with a precision level .0005/ft and a sine bar. Therefore I'm pretty confident
of the numbers.
By the way, I did the same thing for the
horizontal. The top of the horizontal is not per design but the bottom
is. The horizontal is actually an inverted wing rather than a
symmetrical surface. I'm not smart enough to know what total effect this
has.
Craig Berland
D. Brunner
N241DB
90% done 30% to go
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