Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml@lancaironline.net
Date: Tue, 04 Nov 2003 14:37:12 -0500
Message-ID: <redirect-2709636@logan.com>
From: Sky2high@aol.com
Subject: Re: [LML] Re: Closing Surfaces With Epoxy/Flox Vs. Hysol?
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The answer: Depends. 

The construction techniques available in 1989 and utilized before Fast 
Builds, before Cap Strips, before Hysol were thus:

Usually double-joggled joints were closed with a two-part 3M industrial grade 
structural adhesive (called 3M hereafter) that had several noteworthy 
properties.  It was fuel-proof.  Thinner was better in that the adhesion betwixt 
parts was stronger than the goop itself, thus squeeze out was important.  

A. Joggled joints had to be clamped to accomplish proper squeeze out and pop 
rivets were useful for this function.  Two bid were used in the exterior 
joggle depression and, where possible, a single bid on the interior after flox 
(epoxy/flox combo) was applied to smooth the overlap.  Note that each stage 
required more sanding and prep.

B. Non-structural parts (i.e. elevator pushrod tunnel) were microed in and 
supported with one or two bid applied over the joined surfaces and one inch on 
either side of the joint.  The bid was best applied before the micro cured.

C. Bulkheads utilized flox for the joint along with two (or more) bid as in 
B. It was soon learned that the bid was best applied whilst the flox was still 
wet thus eliminating more sand-fill-sand stages.

D. Ribs and spars in all flying surfaces were installed to the first-side 
skins like bulkheads (see C).

E. Closing out major pieces (i.e. wings) was accomplished by:
a. Carefully fitting the close out piece.
b. With the receiving rib/spar filled with flox and the skin covered with 
release tape, the parts were fitted and clamped.
c. After cure, the parts separated, the flox area cleaned and sanded, 3M 
smeared on both sides and the parts clamped together.

F. Control surface final skins were attached soley with flox.

Thus, for example, my lower wing skin (holding up the fuel bays) are held at 
the ribs by a mere half-inch of 3M.  Thus, the use of "depends" during high G 
maneuvers.

The invention of cap strips (rib/bulkhead flanges) changed everything.  More 
modern fast build techniques have ribs and bulkheads pre built of glass (no 
foam or nomex cores) with 1 to 1.5 inch flanges. Initial surface attachments can 
be made with flox only (no additional bid) because of the large joint 
surface.  Skin close-outs are done with Hysol (similar to 3M) and no special fitting 
procedure, perhaps because it is a better adhesive when thicker, perhaps 
because some flox fibers are mixed in with it, perhaps because it doesn't exotherm 
or some combination of these.  The newer epoxy, with its' quick cure time and 
tendency to exotherm, is a benefit for faster construction but cannot be made 
in large quantities. The addition of bid is done at certain close out joints 
for proper strength. 

Any Lancair project should be judged by whether the construction methods 
appropriate at the time Lancair produced the kit (or later modified the 
directions/components) were actually followed by the builder. I don't know of any 
structural failures in Lancairs thusly built.

Scott Krueger
Sky2high@aol.com
II-P N92EX IO320 Aurora, IL (KARR)

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t=3Dutf-8">
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<DIV>The answer: Depends.&nbsp;</DIV>
<DIV>&nbsp;</DIV>
<DIV>The construction techniques available in 1989 and utilized before Fast=20=
Builds, before Cap Strips, before Hysol were thus:</DIV>
<DIV>&nbsp;</DIV>
<DIV>Usually double-joggled joints were closed with a two-part&nbsp;3M indus=
trial grade structural adhesive (called 3M hereafter) that had&nbsp;several=20=
noteworthy properties.&nbsp; It&nbsp;was fuel-proof.&nbsp; Thinner&nbsp;was=20=
better in that the adhesion betwixt parts was stronger than the goop itself,=
 thus squeeze out was important.&nbsp; </DIV>
<DIV>&nbsp;</DIV>
<DIV>A. Joggled joints had to be clamped to accomplish proper squeeze out an=
d pop rivets were useful for this function.&nbsp;&nbsp;Two bid were used in=20=
the exterior joggle depression and, where possible, a single bid on the inte=
rior after flox (epoxy/flox combo) was applied to smooth the overlap.&nbsp;=20=
Note that each stage required more sanding and prep.</DIV>
<DIV>&nbsp;</DIV>
<DIV>B. Non-structural parts (i.e. elevator pushrod tunnel) were microed in=20=
and supported with one or two bid applied over the joined surfaces and one i=
nch on either side of the joint.&nbsp; The bid was best applied before the m=
icro cured.</DIV>
<DIV>&nbsp;</DIV>
<DIV>C. Bulkheads&nbsp;utilized flox for the joint along with two (or more)=20=
bid as in B. It was soon learned that the bid was best applied whilst the fl=
ox was still wet thus eliminating more sand-fill-sand stages.</DIV>
<DIV>&nbsp;</DIV>
<DIV>D. Ribs and spars in all flying surfaces&nbsp;were installed to the fir=
st-side skins like bulkheads (see C).</DIV>
<DIV>&nbsp;</DIV>
<DIV>E. Closing out major pieces (i.e. wings) was accomplished by:</DIV>
<DIV>a. Carefully fitting the close out piece.</DIV>
<DIV>b. With the receiving rib/spar filled with flox and the skin covered wi=
th release tape, the parts were fitted and clamped.</DIV>
<DIV>c. After cure, the parts separated, the flox area cleaned and sanded, 3=
M smeared on both sides and the parts clamped together.</DIV>
<DIV>&nbsp;</DIV>
<DIV>F. Control surface final skins were attached soley with&nbsp;flox.</DIV=
>
<DIV>&nbsp;</DIV>
<DIV>Thus, for example, my lower wing skin (holding up&nbsp;the fuel bays)&n=
bsp;are held at the ribs by a mere half-inch of 3M.&nbsp; Thus, the use of "=
depends" during high G maneuvers.</DIV>
<DIV>&nbsp;</DIV>
<DIV>The invention of cap strips (rib/bulkhead flanges)&nbsp;changed everyth=
ing.&nbsp; More modern fast build techniques have ribs and bulkheads pre bui=
lt of glass (no foam or nomex cores)&nbsp;with 1 to 1.5 inch flanges. Initia=
l surface attachments can be made with flox only (no additional bid)&nbsp;be=
cause of the large joint surface.&nbsp; Skin close-outs are done with Hysol=20=
(similar to 3M) and no special fitting procedure, perhaps because it is a be=
tter adhesive when thicker, perhaps because some flox fibers are mixed in wi=
th it, perhaps because it doesn't&nbsp;exotherm or some combination of these=
.&nbsp; The newer epoxy, with its' quick cure time and tendency to exotherm,=
 is a benefit for faster construction but cannot be made in large quantities=
.&nbsp;The addition of bid is done at certain close out joints for proper st=
rength. </DIV>
<DIV>&nbsp;</DIV>
<DIV>Any Lancair project should be judged by whether the construction method=
s appropriate at&nbsp;the time Lancair produced the kit (or later modified t=
he directions/components)&nbsp;were actually followed by the builder.&nbsp;I=
 don't know of any structural failures in Lancairs thusly built.</DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT lang=3D0 face=3DArial size=3D2 FAMILY=3D"SANSSERIF" PTSIZE=3D"10"=
>Scott Krueger<BR>Sky2high@aol.com<BR>II-P N92EX IO320 Aurora, IL (KARR)</FO=
NT></DIV></BODY></HTML>

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