Posted by GooberSB |
Dec 19, 2011 @ 12:13 PM | 2,915 Views
I wanted to build myself an indoor flier similar to the 12" version I built for a friend but without the expensive PZ brick.
It's amazing how fast the weight goes up on a disc shaped aircraft. At 125% the size of the 12" version, the weight is about 300%.
I started out with a 5g hexTronik motor and a 350mah 2S but it couldn't keep it in the air at all. I switched to a 3S battery and could smell the wires melting in the motor after a few minutes of average throttle. I replaced the motor and battery with a hexTronik 2211 (250 size) and a 500mah 2S. That made a big difference.
Now, I've been using the 2211 on wings of various sizes. The 20" and 24" KESL wings (see my blog posts below on those) and a few failed builds fly great with these motors. But I wanted this one to be indoor not a fast outdoor flier. I learned from my Electrifly Pluma that a large motor with a large prop can fly extremely slow so that's the direction I went.
I put a 8x3.8 prop on this motor and went with a 2S to keep the rpms down. I don't want a lot of rpms this time.
Here's a video of the result. I'm flying on low rates because on high rates the axial roll is pretty fast. I think if I increase my expo from 30% to 70% I can fly it normally on high rates and be able to a good hover too.
Posted by GooberSB |
Dec 06, 2011 @ 08:41 PM | 3,020 Views
I finally got around to finishing my 48" UFO build. It took longer that I thought because I had a few setbacks, but first let me describe the project.
After building 2 successful UFOs and looking at lots of plans for Mantas, bi-planes with disc wings, and other oddly shaped aircraft that could be reduced to a flying disc at the most basic level I decided I wanted to try something large.
I knew the wing loading could be low - maybe 3oz / sq ft - but how low was to be seen. My first step was to buy the sheet of 8 ft x 4 ft 1/2" Dow bluecor insulation at Lowes for $12. The plan was to make this a KFm2 with the step on top being a semi-circle of 48" diameter.
I cut the full 48" dia circle and the semi-circle quickly. After fitting them and doing some tests I realized that the weight of the back half caused it to flex and bow and bend. Like a cattail on the end of a reed has a lot of leverage when the wind blows.
Then I realized I needed a strong spar of some sort to hold the back half of the craft straight and level with the front half. I used a 3 ft 1/4" wooden dowel from Michaels for this. Melted a trench into the center panel all the way along the center thrust line and glued the dowel in with hot glue and gorilla glue. Didn't have to be neat, just straight down the center. It would be covered later with the fuselage.
After glueing the spar down the center it was time to cover the front half with the 1/...Continue Reading