Wednesday, April 18th, 2012 10:17 am GMT -6 Wednesday, April 18th, 2012 10:17 am GMT -6Wednesday, April 18th, 2012 10:17 am GMT -6
 
Pickerel Prototype 2 - study 2

I built two more half-size prototypes. I started building another full-size version.

 

 

 

Are We There Yet?

Is the Pickerel design close to being finished? It sure looks that way to me, but I plan to keep on building prototypes as long as I see ways to improve the design.

I have gone through a couple dozen design revisions between rough sketches, plan views, half-size prototypes, and full-size prototypes. The goal with each one of these is always to decide as quickly as possible what parts of the design to keep and what parts to throw away.

One thing is for sure. What I have now is far better than the design I started out with. It always works out that way, and it takes perseverance to see a design through to its logical conclusion.

Pickerel prototype 2, original design

Oops!

The second Pickerel full-size prototype, shown in the video, was built wrong. When I shot the video I knew something was not quite right. The leading edge angle was very different than the half-size prototype and the plan view drawing I had done earlier.

Before I shot the video I had taken half a dozen or so measurements and everything had checked out. I knew the piece of foamboard I had built it from was not quite the right size, so I assumed that must be the reason why.

After I shot the video, I saw the blunder. Can you spot it? The ends of the raked wing tips are not supposed to be flush with the trailing edge of the rear wing. They are supposed to be a few inches forward of that.

There is another problem with the second full-size prototype. I think it is ugly. The high leading edge sweep angle just does not look good.

I decided to stop working on it. I just did not like how it was shaping up, and it was wrong anyway. I decided to take the design in a new direction.

Pickerel prototype 2, shrunk design

Shrinkage

What if I shrunk the design slightly so it would fit on a single sheet of foamboard? I had already tried that before, but the propeller was barely going to fit in the space between the two wings.

I went through a few more design revisions on paper. I ended up sacrificing the raked wing tips. I know, they look neat. But they were eating up too much of the wing span.

I think I am going in the right direction. Fitting onto a single sheet of foamboard simplifies the design, a major goal. It still looks good. The more compact design does not need as much reinforcement from wooden dowels.

I test flew this half-size version and it shows promise. It would fly better if the nose were just a little bit longer. Right now a small change in the nose weight can make a big difference in the flying qualities.

Feedback

How does it look to you? What would you change?

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