My 18" glider

Last Saturday I decided to make chuck gliders. I needed some exercise.

I had:

• a Sig's tapered balsa sheet 1/4"x4"x36"
• a leftover piece of 1/16" balsa sheet from years ago
• a length of carbon fibre rod about 2.5mm from a discarded kite and about 22".

Using a measuring tape, I marked the middle of 36" on the flat bottom side of the tapered balsa.

With a 12" steel rule, I marked the centre line and panel lines of each 18" pieces of balsa.

Then I extended the lines to the top side of the tapered balsa.

The mid panels are 5" and the end panels are 4" in lengths.
The end panels are tapered with the tip at 2".

I cut out the two 18" wings, I did one with swept back tip and the other with swept forward, i.e., cut from leading edge and the other from the trailing edge.

I marked out 3/8" on the top planform from the leading edge, 1/16" edge lines from the bottom, planed and sanded to airfoil shape.

I sawed three-quarters of the way through the top, on the centre line and mid-end panel lines. Bend, prop up and cyano ('insta-cure' from BSI) the mid-panels to 1/2" at the mid-end panel lines, forming a dihedral. Then I gripped a piece of sandpaper over my steel rule and used that to sand half-way on the sawed lines of the mid-end panel lines again. Each tip panel was propped up with the 2" high triangle piece of offcut and that formed my tip dihedral. This formed my polyhedral wing.

I cut from 1/16" sheet balsa the fin, horizontal stabilizer and wing pylon.
The horizontal stabilizer is 5" span, 4" root chord and 2" tip chord. The fin has the grain running with the leading edge, is 45 degrees to the horizontal and the other dimensions were just approximation.

I am placing the fin underneath the horizontal stabiliser. I figured that I want a glider which points to the wind, so it has to be large enough to counter the pylon and polyhedral, and which will produce a rolling motion to bring the nose towards the wind, hence the inverted fin position.

I first cyano on the horizontal stabiliser, lining up the centre line with the rod, then cyano on the fin to one side of the rod. After this was done, I approximate the nose length of the glider by using rubber bands to temporary position the wing and 2 pieces of 5gm leadweight at the nose.
I adjusted the wing fore and aft until the CG lies somewhere one-quarter from the root leading edge and put a bit of masking tape on the carbon fibre rod to indicate the edge of the wing's trailing edge. I sanded the pylon piece, and shortened the trailing edge by about 1 mm; this is to give the wing a bit of positive incidence. Then I cyano the pylon to the wing, lining up the pylon with the centre line marking and when cured, cyano on the assembly to the fuselage rod/tail feather assembly, skewed slightly. I throw with my right arm and wanted the glide to be left turning, I wanted the tail to contribute slight lift so the wing was glued on with a slight rotation to the left when viewed from rear.

To strengthen the pylon-rod joint, I glued on 1/16" sheet with grain perpendicular to the pylon to form a reinforcement and to provide a bigger contact surface for the rod, aligning the pylon's trailing edge on the mark I made earlier with masking tape.

From one of the wing's off-cut, I made a little nose, slotted on the long side and of sufficient area to cyano on the 2 pieces of leadweight. this is then banded onto the rod in the front. This is my idea of adjustable nose weight positioning device. I don't like the idea of poking anybody unintentionally with a 2.5mm rod and some form of safety must be exercised.

Initial flight in the field resulted in me cutting off a piece of the leadweight. The CG is now more than 50% from the wing's root leading edge and is lower than the wing because of the pylon.

Throw hard, the glider zooms up, transition into left hand glides. Then what's left is a bit of warping on the left tip so that it doesn't dip too low.

I am leaving the nose banded on for now until I get more consistent flights and have to trim it more accurately.

Why bother to build? Isn’t it better to just buy a ready made model?

Why bother to build? Isn’t it better to just buy a ready made model?

Here’s a section off a preface in a book entitled “How to Design and Build Flying Models”:

The great failing of the hobby, as it is practiced by millions of men, boys (and girls!) today, is the withering away of resourceful initiative, a natural result of the trend to prefabrication, ready-to-use items, and things that require little or no basic know-how.

The modern hobby overlaps more and more with the toy field. If model planes are to remain more than toys, keeping traditional values of training and worthwhile accomplishment, it becomes highly important to understand why and how a plane flies. For a model-plane builder not to have this understanding would be like a doctor lacking the ability to diagnose his patients' complaints. Unthinkable!

And this book was published in 1970.

Treasure Trove at www.outerzone.co.uk

A treasure trove it is, what a great repository for aero-modeling knowledge! There are an abundance of plans and even some books and all these captured the ingenuity of aero-modeler of old which is still relevant today.

www.outerzone.co.uk

I have never seen or flown free-flight (simple stick rubber jobs excluded), CO₂, or jetex, but there is an abundance of good plans (in good taste) in this repository and they are obviously good candidates to be converted to modern radio control or modified to use present material and technology.

 

We are in a way better situation now to design, build, finish and fly model planes than it was then. We have the internet to research our projects, home/office printers to print insignia and other designs. We have foam sheets, carbon fibre rods and tubes to build or strengthen our models. We have affordable airbrush and air compressor to finish the models. We have brushless motor/esc with lightweight lithium polymer batteries to power our models. Our radio control equipment is very affordable, lightweight and reliable. And there is a multitude of products such as retracts, hinges, and on board telemetry, cameras and such. Our flying skills in general has obviously improved with so much of ready to fly models that I would guess that we would be considered ‘skilled’, ‘experienced’ or even ‘expert’ flyers back then. Minimal effort, maximal enjoyment.

 

Some thoughts are:

·        Ducted fan designs. Easily converted to electric ducted fans using brushless motors and commercially available ducted fan units.

·        Free flight designs. Easily converted to radio control. I am thinking of a Sopwith Triplane or a Savoia S13 or even a DH-2.