Thursday, June 12, 2014

Eagle Spacecraft Models, meet the Balsa Disk Fliers

[Cover image of Eagle Book of Spacecraft Models sourced from John Guy Collick]

Vince sent me a link to a review of a most excellent old book published in 1960 called Eagle Book of Spacecraft Models by Ray Maimstrom. I’m a sucker for these sorts of old-school model building books. I searched and found it for sale at an online reseller, and although it’s a little pricey for me, the seller had a photo of this interior page describing  how to build a free-flying model airplane in the shape of a ‘Martian Flying Saucer’.
[Sourced from an ad at Abe books; won't say which one as I might still buy it :-) ]

I immediately flashed back to some posts at my now defunct blog, retroDynamics, about some simple disk-wing hand-launched gliders I made some years ago from balsa wood and styrofoam. They won’t go to Mars :-) but they’re good for some pleasant backyard fun. For a change of pace, here are the old posts:

13 April 2009
Circular Wing Glider
I’ve been reading about airplanes with circular planform wings, and building some simple flying models, for a year or so. Hopefully I can write more about them in the future, but, thusly inspired, I built this very simple balsa glider back in January.

The wing has a diameter of 6 inches. The mass of the glider, less the nose weight, is 10 grams; the clay nose weight adds 3 grams and puts the balance point ahead of the wing’s quarter-chord.

It flew fairly well. For awhile. I launched it from the back deck of the house by pitching it high over the snow drifts piled up in the backyard. During construction I had inadvertently glued a small twist into the tail fin - which I couldn’t quite twist back out - which caused the glider to turn to the right, sail over the 8 foot side-yard fence, and crash against a wall of my neighbour’s house precipitously close to her kitchen window. Luckily no damage was done and I was able to inconspicuously retrieve the plane without having to explain to her, or my wife, why a man of my age was assaulting her house with a toy glider.

That was the last flight. The raw balsa had absorbed a lot of snow and the whole thing warped too much to be flyable after that. That and the impact on the nose-weight snapped the canard from the fuselage. Now that summer is almost here I’d like to try and build a few more of these; some from foam as well as balsa.

21 July 2010
First flight of a disk-wing glider with a K-F step
I tried flying this disk wing glider with a Kline-Fogleman step in the backyard last evening after the wind had died down.

The disk has a diameter of 6 inches and the total mass of the glider is 5.5 grams. A paper-clip attached to the nose was used to place the centre-of-mass a bit ahead of the quarter-chord.
Synopsis: It felt too light when it left my hand, veered in a large arc to the left, crashed into a tree, and broke off the canard.

I clumsily tried to glue the canard back on with super-glue - it was originally attached just with white glue which was no doubt why it broke off ! - but, I got the alignment all wrong. I decided to call it quits for the evening, and spend a little quality time some other day on fixing the plane.
I did try to fly it immediately after the crash without the canard. It didn’t flip end-over-end, just made a short and graceful arc to the ground.

17 August 2010
Trimmed flight of the K-F disc glider
I fixed-up the broken KF disk-wing glider and gave it another try. The wing and canard were re-glued with a thick super-glue, and the balancing clay mass was moved all the way forward to the nose. Total mass is now 8 grams. The centre-of-mass is about halfway between the leading edge of the disk and the trailing-edge of the canard.

I flew it a little in the backyard to get the trim worked out before trying to fly it in a larger field. This way I can run down to the workshop to easily fix things if needed. I shot a short video of some of the backyard test flights, but for some reason I couldn't get them uploaded, so some imagination is required at this point :-) The glider was launched from roughly 5 feet above the ground, and it flew for about 22 paces before crashing. It seemed surprisingly resilient and didn’t break or distort after a few fly-and-crash sessions.

I think the model has a lot of drag, the canard is getting a bit beat-up from a few crashes and re-glues, and the disk is probably too thick for such a small wing and low-speeds. Anyway, I’ll try flying it in a larger field before starting to build another variation.

19 August 2010
Disk wing glider without K-F step
This glider is the same basic size as the one with the K-F step. I took it out to the backyard to get it trimmed for flights in a bigger field.
The centre-of-mass is just a little bit ahead of the disk's leading edge, and the total mass is around 6 grams.
Once trimmed, it seems to fly ok - well, I know that isn't too quantitative :-) I think it flies a little worse than the one with the K-F step, but this too isn't based on any quantitative. I need to devise some sort of test that would demonstrate what sort of effect the K-F step does have.

19 March 2012
Unfinished: Disk wing glider with curved K-F step
Back in 2010 I was playing around with disk wing gliders and one that had a Kline-Fogleman step. I made up some parts for a variant that had a curved step, but never got around to gluing the pieces together. I thought the model with the K-F step flew better than one without, but that was just a feeling and never proven. I need to get out the glue and give this one a try.

I checked around my workbench and those pieces are still there - maybe a summer project.

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