Posted by schrederman |
Jun 08, 2008 @ 10:59 PM | 11,944 Views
I built many of these models. I lived pretty close to the designer and kit manufacturer, Cecil Haga. These models were large area, thin airfoiled models that flew well if built light. However, I saw more that one of them that just didn't fly worth squat! Without exception, these models all had decalage problems. Setting the stab absolutely parallel to the flat surface of the wing behind the spar was the most critical part of building these models. On my later personal models, I set the stab with 1/2 degree less positive decalage than the designer called for. They were almost 0/0, but not quite. After all was said and done, I then trimmed the flight mode of these models by removing nose weight until they were pretty squirrilley, and then I added back 1/4 to 1/2 oz. I never tripped this airfoil. I could climb with just about anyone and out climb most.
Another secret that I learned quite by accident... Blunt the leading edges, slightly... ie... make the leading edge radius slightly larger and use 1/4 sq. instead of the 1/8 X 1/4 of the original. If this is done, the tail saddle will have to be modified to give no more than 1 degree positive decalage, and the trimming by CG will have to take place all over again.
Trimming by CG... what? Here's how... Measure from the CENTER of the leading edge radius and the trailing edge of the wing to the table. Continue to move stuff around until the centers are equal distance from the table. With the wing at 0 degrees with the table,...Continue Reading
Posted by schrederman |
Jun 07, 2008 @ 01:49 PM | 11,921 Views
I have seen a lot of change in my life, due to my profession. We have gone from rotatry-dial phones to cell phones, and from 6 MHz wide, analog television stations to digital video and audio. I have personally gone from flying an E-K Logictrol Ranger, 3-channel radio to a JR 9303. I resisted the moldie movement a bit, but not really. I am still convinced that an accurately-built wood wing with some carbon enhancements can be competitive. While I lament that most of us don't design and build anymore, I am not someone that seriously bashes those non-builders. Tease them a bit, yes... but they always know it's not serious.
Take, for instance, the Houston Hawk. From conceptual talks to full-size CAD plots, one week in the making. My original is still the best flying model I own. It has, at the time of this writing, 261.5 flight hours, and 1401 launches. It has been crashed and repaired twice. It is competitive, though that was not really it's purpose when it was designed. When I went to Houston, I was surprised to find the old Hawks club to be just a shadow of it's former glory. Being a prolific builder, it became habit for many to gather at the back of my vehicle to see if I was dragging out something new. That led to a club building project. That's what the Hawk was... a teaching tool. We had 17 people in my garage for a wing-building session. A teaching tool... yes, but it is competitive, too, and it has proven itself.