How does spar protrusion affect performance

Marc Ramsey wrote:

A related anecdote: my partner and I have a
LAK-17A which has quite obvious spar bumps on
the top and bottom wing surfaces. We're perfectly
happy with the performance, so we haven't done
anything about it. A top US contest pilot had flown
with us a number of times in his new ASW-27B
(when we were using 15M tips), and noticed that
he couldn't keep up in higher speed glides.

So you are going to make impressions of your "unique" airfoil in case LAK
fixes their process? That way you could get them to build you another
glider (should you need one) with assurances you will still have the magic
bumps. ;-)

Regards,

-Doug

Doug Hoffman wrote:
So you are going to make impressions of your "unique" airfoil in case LAK
fixes their process? That way you could get them to build you another
glider (should you need one) with assurances you will still have the magic
bumps. ;-)

Not to worry, I don't think LAK is any more capable of fixing their
processes than Schleicher 8^)

Marc

Marc Ramsey wrote:

Doug Hoffman wrote:
So you are going to make impressions of your "unique" airfoil in case LAK
fixes their process? That way you could get them to build you another
glider (should you need one) with assurances you will still have the magic
bumps. ;-)

Not to worry, I don't think LAK is any more capable of fixing their
processes than Schleicher 8^)

Of course. How naive of me. :-)

Btw, here at Ionia we have a LAK-17A driver whose ship also exhibited some
problems at the surface over the spar. Although I can't recall if it was
protrusion or depression. Regardless, the local repair guru, David Nelson,
did a repair job on it and it now looks flawless. The LAK-17A driver seems
to really like his ship as well.

Regards,

-Doug