Reply-To: Sky2high@aol.com
Reply-To: lancair.list@olsusa.com
From: "Scott Krueger" <sky2high@hotmail.com>
To: lancair.list@olsusa.com
Cc: Sky2high@aol.com
Bcc: 
Subject: LNC2 Flaps, Trailing edges, Fairing and Ailerons
Date: Sun, 14 Oct 2001 11:15:00 -0500
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Message-ID: <F11BLSAQV6uPDVniSnR00004b0f@hotmail.com>

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David,

You wrote:

<<...flaps are usually (if not always) down on 2 place Lancair planes at the 
airshows.  ... I also worry about the thickness of the trailing edge of the 
flaps, ailerons, and elevators.  ... is there some trick to make everything 
look similar (like lots of fill near the gap between them)?  I have decided 
to sand the trailing edges of the elevators and ailerons to the same exact 
thickness, with the flaps having a much thinner trailing edge, but exactly 
on a straight line with the aileron
next to it.  Then I will leave the flaps in the full down position at
airshows and no one will even notice that the aileron and flap have no real 
similarity, right?>>

After you have correctly made everything from wing tip to fillet in a 
straight line, consider these comments:

1. Flaps - On many 320/360s, the bottom tip of the left fillet is not level 
with the bottom tip of the right fillet when the aircraft is laterally 
levelled -- sometimes there is as much as a 1/2 inch difference from level.  
This should be checked with the wings on and, of course, the trailing edge 
of the wingtip should also be level.  This may affect your flap re-rigging 
after test flights.  It has been useful to fly in primer to get the rigging 
and fairing right before final paint.  Cruise flap to fillet fitting is 
important to reduce interference drag.  The flap functions to reduce lift 
(hence drag) at its faired-in 7 degree reflex position and then to affect 
the trailing edge camber (hence pitch and drag) when taken out of reflex. 
One only cares that the thin flap trailing edge does not induce drag at 
cruise.  Note that a full flap landing with a strong crosswind exhibits an 
increase in weathervaning because of the upwind flap and an apparent 
blocking of the downwind flap.  Even though the flaps may be beautifully 
faired in, they may be left in the down position, when parked, because it 
does allow easier and safer ingress and egress.  It also allows the curious 
to get a closer cockpit peek rather than leaning over the flap and 
potentially damaging the flap or falling and gouging the canopy with their 
sunglasses or nose ring.

2. Aileron - The blunt 1/4 inch trailing edge makes that control surface 
more responsive.  Look at your neighbor's jet for confirmation.  Do not 
dicker with a crucial low speed stall control device - not with its' 
structure or shape.  In flight, some have experienced a "twittering" of the 
ailerons when rigged neutral at cruise.  This is a consequence of rod end 
lash.  This situation can be eliminated by rigging both ailerons slightly up 
(just a hair) when the stick is centered resulting in light air pressure on 
both, thus no lash. If your test flights are good with such rigging, you 
might wish to add micro to the wing tip for visual fairing although it is 
not necessary since the change is so small.

Remember, it is an AIRplane and only the air cares what your surfaces and 
trailing edges look like.  The airshow judges won't be flying in your 
airplane, you will.

Scott Krueger
N92EX
98 Oshkosh Outstanding Workmanship
99 Sun'n'Fun Outstanding Aircraft


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