Archive of the Yahoo! Groups mailing list for the Bug hand-launch glider 2002-2018

From: "gldrgidr" <gldrgidr@...>
Date: Saturday, May 31, 2003 12:55 PM
Subject: Re: Help with rib production?
Understand that this is just my opinion, but I think that the plastic pod is the worst design feature of the Little Nipper. It takes a lot of effort and time to produce the first good pod. You have to carve a mold and learn to heat the PETG at just the right temperature and heat the plastic sheet uniformly so that you get a pod that doesn't have thin areas. All of this could easily become more of a project than building the entire plane. And when you do get a good pod you are forced to install the servos to the wing instead of a distance in front of the wing where their weight can be used to balance the weight of the tail. The see-thru fuse also doesn't help with making the plane visible at altitude. I built a balsa pod for my nipper and it was lighter even with a layer of .75 oz. fiberglass to make it crash resistant. I could have built several balsa pods in the time it took to get a good plastic pod. I also think that installing all the radio gear in the fuse makes it a lot neater package - one piece wing mounts to one piece fuse. The see-thru pod is very inovative looking and this may make it worth the effort for some, but not for me. John --- In BugHLG@yahoogroups.com, "John Gospodarek" <John.Gospodarek@i...> wrote: > 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