From: "John Gospodarek" <John.Gospodarek@...>
Date: Friday, May 30, 2003 8:19 AM
Subject: Re: Help with rib production?
Date: Friday, May 30, 2003 8:19 AM
Subject: Re: Help with rib production?
Chris,
Thanks for the reply. Very nice explanation! I have seen several on
the LN Group and yours is very complete. I have the petg and have a
good idea of how to pull the pod. My problem is how to make the
mold. Do you make two half molds from the root rib template and glue
them together? I am not a good carver and am not sure how to get the
angle correct and a good fit, if I don't do it that way. I have even
considered making a foam mold first and doing a FG lay-up over it.
The mold is the stopping point for me.
John
--- In BugHLG@yahoogroups.com, "Chris Lewis" <christopherlewis@e...>
wrote:
> 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