The other day I was out at Brewers park which some kids. Seemed there were about 4 kids that were old enough for Squirrels but they had brothers and sisters that were a little young. It’s not that they can’t do it but the supervision requirement rises sharply for kids under 10. If I have four kids that are new to modeling, I can’t manage the younger ones at the same time.

So I was thinking there needs to be some thing simpler than a Squirrel that flies nicely for younger children.

Perhaps a catapult design would be nice. To make it even simpler I was thinking of going with a spinner like a maple seed.

I’ve been working on a few catapult designs for quite some time now and decided to try and finish one of them. I figure that a twirling maple seed type aircraft would be a good solution.

The first step is to try to get something to auto-rotate.

I measured the center of gravity for a maple seed that I found on the ground. Here are a few pictures to show where it is.

Center of gravity

An excellent way of measuring the center of gravity of any aircraft is to suspend the aircraft by two or three lines. Make sure that all lines suspending the aircraft all originate from the same point. Also make sure that the aircraft is fairly level. Suspend a plumb bob or any pointing object from the same suspension point but make sure that the plumb bob does not touch the aircraft. In my apparatus I used a needle as the plumb bob. Actually my friend Joanne helped me with this measurement and the pictures.

I made a few prototypes and haven’t had much luck yet. Here are a few

I’ve tried moving the Center of Gravity around with the use of putty. I’ve tried many different shapes. I get a bit of rotations sometimes but the sink rate is very high. I expect a larger version to sink slower than an actual seed.

There is a lot more going on than meets the eye here.

In a nutshell the viscosity of the air is quite relevant at this scale. Ridges on the maple seeds leading edge contribute to the production of a vortex of constructive turbulence.

Here’s a model my friend Ondrej Mitas made. It’s made from balsa, esaki, basswood, and lead. He said it “Sort of spun like the real deal.”. I’d love to see a video of it so see if I can learn anything. Ondrej has a lot of interesting and amazing art. It’s worth a look!

There have been other attempts. As a rule they are much too large to have this turbulence pattern (larger Reynolds Number and so forth). But there are some interesting flights here: