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Monday, March 10, 2008

DLG Plan: Part 1, Design thoughts

"The time has come," the Walrus said, "to build a DLG:
Of wings - and fins - and carbon booms -
Of glass fibre - and pins -
And why the sky is bubbling -
And whether pigs have wings."

It is time for me to build such a pig. First question, shall I use an established plan or kit, like Spin Up, Round-A-Bout, Dynamo Hum, Turn Up, or other? Erm....No. Why? Because I wanna make my own! I enjoy designing. I cannot do better than the established designs. No, my objectives are different. I see this as a learning experience. I'm not going to ignore the exisiting designs. I'd like to create a free flight tip-launched glider that has the following attributes:
                • Simple design
                • Quick and easy to build
                • Pleasant looking
So, ladies and gentlemen, I present to you LIPZOID, well, a back-of-an-envelope sketch of it.

DESIGN THOUGHTS

The original Monster DLG by Tetsuo Itoh in 2004 had 8 panel wings. Phew! At that time, it was the fashion in conventional "javelin" style launching HLGs to have multi panel polyhedral wings (5 or more panels). A few months ago, Tim Batiuk smashed the US HLG record with his 4 panel design, Turn Up. His plan is freely available at Kurt Krempetz' excellent
AMA Glider website. If I was sensible, I'd make a Turn Up (er, affectionately, "Turnip"). It has a 4.5" root chord, four wing panels and is not my own design! Maybe later.

I have 4" wide 6mm balsa in stock and want to try to make a three panel free flight DLG. 4x36 worked on Dynamo Hum, Twirly Bird and the Monster was close to that size. Three panels works for the Gambler RC DLG. Most F3K designs are simple dihedral (though of course, they have aileron servos!). There is long history in 3 panel wings in Free Flight, such as the iconic, super-performing Keil Kraft Senator rubber model, many F1A glider designs and quite a few conventional HLGs. So why not a FF DLG in 4x36 three panel? The wing can be glued up in one session and the wing root fuselage joint is a simple butt joint (no need to sand a v in the fuselage). So time can be spent instead on that lovely glass fibre cloth stuff. Fewer joints means lighter weight too.

For a bit of style, and because capriciously, I'd like to call the model LIPZOID, I decided to utilise ellipses for all flying surface planforms. My excuse is that ellipse planforms have a long history in free flight, especially in HLGs. They are also easy to print on a pc! None of this fancy drawing package nonsense, no. I use old-fashioned PowerPoint. I'll use ply biscuit(s?) and GF cloth on wings, no CF tow. It must have bass wood or spruce on LEs (thread may be ok on the tail feathers). Fuselage from 6mm balsa reinforced with GF, spruce or bass and ply, aiming for light weight and simplicity. Probably a nylon bolt for the boom pivot. Button timer and probably 2 different thicknesses of fishing pole elastic to hold the boom yet create appropriate tension on the timer arm. No throwing peg - just sandpaper top and bottom - just like Mr Batiuk.

Will it fly? Who knows? But I'm gonna enjoy finding out!

1 comment:

StevieB said...

I'm looking forward to seeing the progres of this build. I'm planning to have a new DLG ready for the Nats following similar design principles to you.