Posted by: John Jombock , DN1513 on March 28, 2005 at 23:36:09:
In Reply to: Re: Uni-glass sideboard reenforcement posted by Paul Goodwin on March 24, 2005 at 21:44:32:
A NON-GLASS SOLUTION
I would like to describe a very simple lightweight way to fix or
prevent splits in the sideboards of DN fuselages . This is an
alternative to the use of fiberglass cloth .
I started building DNs in the early '60's . It didn't take me
long to become acquainted with split sideboards . I noticed that
the cracks seemed always to develop just above the floor back
over the runner plank. I thought that maybe I could somehow take
advantage of the tremendous athwartship strength of the floor
system to support/strengthen the sideboards in the problem area.
I was working for Alcoa in those days and access to all kinds of
aluminum nails . Aluminum nails are made from high-strength
hard-drawn wire . itook some of these nails , sawed off the
heads , and epoxied the resulting "pins" into holes drilled
in the problem areas of the overturned hull at midthickness of
the fuselage sideboards . I have found this scheme to be 100%
effective for almost 40 years . I went to the local True Value
hardware store today and found that they have 10d(0.145"x2-7/8")
Nichols aluminum nails in stock ; these are probably all you
need , although I have used 16d(0.175"x3-1/2") immediately over
the plank .
Here are some additional comments :
Drill the holes for the aluminum "pins" about 1/16" deeper than
the length of the pins . Use a drill larger in diameter than
the diameter of the pin to let the epoxy to flow freely along
and around the pin . After drilling the holes , turn the hull
over and "bounce" it to shake the "sawdust" out of the holes .
Then turn the hull back over and install the pins .Use #206
Slow Hardener and just a little colloidal silica . You want the
wood to soak up all the epoxy it will take . Gougeon #807
Plastic Syringes will make filling the holes easy . Next drop
epoxy-coated pins into the holes point-first . Keep an eye on
the pins ; maintain a little mound of epoxy over each pin until
the epoxy hardens .
For repairing cracks , use #807 syringes to inject epoxy under
pressure into the holes (before installing the pins) to fill
the cracks as much as possible .
I've generally used a 3-inch pin spacing , but I can't guaran-
tee that's the optimum .
I'd put pins in from the intersection of the seatback and top
deck up to the first knee .
I might gradually decrease the length of the pins from the
leading edge of the plank up to the knee to avoid a distinct
horizontal line of stiffness change along the fuselage side .
If I haven't made myself clear on all of this , you can give me
a call at 724-794-4425 .