From: Fredmoreno@aol.com
Message-ID: <b0fe4696.2508a136@aol.com>
Date: Thu, 9 Sep 1999 01:35:50 EDT
Subject: Lancair IV wing root fairings
To: lancair.list@olsusa.com
Mime-Version: 1.0

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I have seen several Lancair IV aircraft with a gap between wing and fuselage 
through which you could see daylight.  BAD.  The leakage creates substantial 
drag and can affect stall behavior.  Putting on tape to cover the gap is not 
fully effective as the speed is frequently enough to remove the tape and if 
the air does not, the rain will peel it off in short order.

I have seen two ways to make the intersection tight.  One (which I used) is 
to butt the fairings to the wing and fair them smoothly so the top and bottom 
surfaces are flush at the intersection, and then put a 2 BID flange 
internally on the fairing that fits into the wing about 1/2 inch.  Use 
release tape on the wing and shape the tape so that the flange hou build has 
some tapered lead-in to permit the wing to slip over the flange as it is 
later reinserted into the fuselage.  Works fine.  It requires that you put 
the flange on while the fairings are held in place with Clecos, and then do 
the final bonding to the fuselage after they are finished, trimmed, and 
sanded.  Inserting the flanges while laying on your back and working in the 
little space between fuselage and wing is not fun.

    The second approach which I like better (seems easier) is to lap the 
fairings over the wing about 1/2 inch by stretching the fairing toward the 
wing tip by adding BID on the exterior of the fairing and onto the wing 
(which is covered with release tape).  The wing is then removed and the BID 
trimmed.  The wing is then reinserted and the fairing finish sanded. When 
finished the fairing is not flush to the wing surface but leaves a small step 
of perhaps 0.04-0.06 inches.  If this is also the paint line between white 
wing and colored fuselage (as is commonly done) it is not noticeable at all.  
One then sands the wing surface which is under the fairing (out of sight) to 
provide some lead-in to the fairing (taper) when the wing is reinserted.  
With a little care, patience, and persuasion and some tools (like thin putty 
knives) one can cause the fairing to slip over the wing and seat tightly.

Either way there is a lap joint to eliminate air leakage.  Mucho better than 
a butt joint.

Fred
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