Winglet performance

At 06:58 22 February 2011, Bill Bullimore wrote:

However...
- we spent 11 whole days getting them on straight and true

- the original kit was jigged incorrectly and would have resulted
in misalignment (food for thought when done professionally)

- the foil profile did not match the wing at the join. This was
corrected with re-fairing when the glider was refinished in Poland


Whose winglet kit did you fit to your Mosquito, how did you know the
correct toe in/out angles (i.e "Straight & True) & how did you measure
the the toe angle when fitted.

I'm dubious about the factory fitted winglets on my Discus B - again the
cut angle on the winglet doesn't match the Schempp tech note. But the
performance doesn't seem to be any worse with them than without and they
stop the tip dolly falling off (When manoeuvring on the ground, before we
get ay sarky comments!) so I continue using them.

Kevin

Kevin,
I won't name the kit supplier for obvious reasons, but we did spend some
considerable time getting the locating pins back to true and parallel,
before we could even start the fitting.

It was indeed a memorable moment when we sawed the first old tip off and
it fell with a klunk onto the floor.

From memory we only gave only 1 or 2 deg toe-in. There is a 'flat-ish'
surface on the outside winglet face to establish toe-in. It is a very
complex mod. because there are so many variables, I remember 6 of them:
~ rotational pitch
~ toe-in/out
~ splay (dihedral)
~ total span in and out
~ vertical position
~ fore/aft position

For the best match of the airfoil profile between winglet and wing, we
simply chose the 'least worse' position. Wing tape helped the final
match and covered some sins. Poland did a proper job later.

The main reference point established was the top rear tip (projected out
with layers of tape), which was used for all checks. On a non-flying day,
it might be worth running these checks on your assembled glider, I would
also use a point at the front of the wing/fuse join. It's amazing how
span can vary between left and right wings.

Also I believe we made a mistake with the tear-drop shaped eurathane
stick-on tip skid by sticking it on in the direction of flight. Next time
that gets replaced I will try and align it with the best l/d airflow.

Of course the real expert on all of this is Afandi Darlington, compared
with his expertise, one is reminded of the great philosopher Homer
Simpson's all-embracing observation:
"Doh- I wish I knew Stuff".

bwBB


Whose winglet kit did you fit to your Mosquito, how did you know the
correct toe in/out angles (i.e "Straight & True) & how did you measure
the the toe angle when fitted.

I'm dubious about the factory fitted winglets on my Discus B - again
the
cut angle on the winglet doesn't match the Schempp tech note. But the
performance doesn't seem to be any worse with them than without and
they
stop the tip dolly falling off (When manoeuvring on the ground, before
we
get ay sarky comments!) so I continue using them.

Kevin