The wing type utilized in 235/320/360s is

 

NASA NLF(1)-0215F

 

 Natural Laminar Flow airfoil #1

 

 

02 = Lift coefficient of .2 at cruise.

15 = max thickness is 15% of chord.

 F = flapped

           

 

Design criteria -

1. Produce max lift coef at certain Reynolds number AND not depend on laminar flow.

2. Obtain low profile drag coef  from the cruise lift coef of .2 (Cl)

 

Constraints:

 

a.  Thickness 15% of chord,

b.  Pitching moment must be a small negative number at Cl of .2 and

c.  Simple flap of 25% of chord.

 

Max lift, Min Drag would be best if laminar flow occurs on .4 chord of the upper surface and .6 chord of lower surface.

High lift is in conflict with pitching moment and negative positioning of the flap is used to fix this.

 

Testing was done at -10, 0 and +10 degrees. 

Tests were conducted from 66 Kts to 198 Kts (.1-.3 mach) and the objectives were met.

 

There are many references to this airfoil on the web, especially NASA Technical Paper # 1865.

 

So what?

 

The wing should not be over stressed by taking the flap out of reflex.

 

Other points (relative to my 320):

 

1.  If flight is preferred at greater than 120 KIAS, the gear cannot be used for drag since Vlo and Vle are 120 Kts.

2.  If flight is preferred at greater than  100 KIAS, full flaps cannot be used since Vff is 100 Kts.

 

Here is the result of  recent experimentation at Va = 143 KIAS, light turbulence:

 

At 3000 MSL, 29C, Dalt 4840, Palt 3290:

 

KIAS MAP" RPM Flap degrees      Attitude (Approximate from AI)

-------  -------- ------- -----------------------  -------------------------------------------

  141 18.5   2310  -7 (faired reflex)  2-3 degrees nose up

  141 20.1   2310   0 (no reflex)

  141 22.2   2310 +3 (takeoff)         .5-1 degree nose down

 

Too bad I forgot to take along my digital longeron angle device.

 

I will use small flap displacements in addition to reduced power to fly in bad turbulence at Va or less.

 

I do use flap increments to slow down (to gear speed) and keep the nose down as I enter the airport traffic area.

 

Note, this info is worth what it cost.  It only pertains to Lancairs equipped with the NASA NLF(1)-0215F wing.