From: "Chris Lewis" <christopherlewis@...>
Date: Thursday, May 29, 2003 5:49 PM
Subject: Re: Help with rib production?
Date: Thursday, May 29, 2003 5:49 PM
Subject: Re: Help with rib production?
John - Sorry to hear that you didn't have folks come through for pod
material. Next time send me a PM and I'm more than happy to help if I
happen to have surplus material on hand. My first couple of pieces
came through the mail, but I burned through them quickly while
learning. It's just as well that you have a quantity since pod
pulling is as much art as science.
The pod is one piece of .060 PETG heated over a stove burner and
pulled over a form. I use a piece about 6.5" x 6.5 to 8" and use a
couple of spruce sticks 1/4"x1/2"x7" along with a couple of "binder
clips" on each side to hold the plastic while heating. The key is to
heat slowly until the PETG is droopy, but not until large bubbles
start to form. Heat thouroughly from edge to edge by moving across
the burner. I have a pod mold very similar to the one shown in Bruce
Kimball's folder on the Little Nipper group. It has a carved, sanded
and faired poplar fuse shaped to my liking and about 3" of wing shape
attached to each side at the correct dihedral angle and LE shape. It
has a 1/4" steel rod drilled into the TE side so that I can mount the
form in a vise that is clamped right next to the stove. Once the
plastic is floppy - Use gloves! you'll immediately want to
pull it over the pod form and use your gloved hands to make sure it
gets into the corners where the fuse and wing stubs meet. It takes
work and practice. Pull to fast and the PETG gets too thin. Too slow
and it cools and doesn't cover the pod mold. Be patient! Practice,
Practice, Practice...
Re-read my instructions and step 9 indicates the measure, mark and
drill method for the intermediate rib spar holes. This extra wingspan
is crucial to gaining more float time. I don't use pins. I just glue
as I go with thin CA using a capillary tube to restrict glue
application. Goes fast, works great.
Keep in mind that going to the plastic pod means a total redesign of
the airplane. The servos must be recessed in the wing, a boom mount
must be fabricated, bolt anchors for the pod/boom mount must be added
to the wing, servo linkages changed, pod form built and a pod pulled.
Glassing the balsa pod, going to a cruciform tail (supergee style),
WPU for tail finishes and extending the wing are simpler mod's if you
are just looking to move up from the standard bug. It you like to
tinker, go nuts. The Bug is an amazing platform to start from or fine
just as it is.
After talking with Dick Barker of DLG fame, I might try making this
pod in two pieces using Vac-bag method and FG. But I've got a full
sized Uplink to scratch build first.
Hope that helps.
Chris in Seattle