11-06-2010, 07:28 PM
|
 |
BARCLONE Rocketry
|
|
Join Date: Mar 2005
Location: Mobile, Alabama
Posts: 5,357
|
|
Correction to Fin Sheets
After reviewing the patterns I posted earlier and studying the way the vertical fin halves actually come together, I realized they were not quite right. RockSim introduces some "gotchas" in the fin export. While it did a good job following the pattern of the ogive transition at the end of the probe, it did not correctly extrapolate (good 50-cent word) the step at the very rear of the fin, just behind the trailing edge of the main wing.
As I looked closer at the pattern, the true height of the ogive transition above the top surface of the main fin was really not enough to justify cutting the curve. It would also have been a real royal pain to fill that gap with a piece of balsa and round it out properly. Most of that transition was "inside" the area of the main fin.
The new cutting pattern and the revised RKT file make this part of the construction easier. I have eliminated the ogive transition from the tip probe dowel stock. It now ends where the notch is located in the leading edge of the main fin. The vertical fin begins where the dowel ends, and fits flush with the top surface all the way to the rear edge. Now, the vertical fin has a "step down" that is 1/2 the thickness of the main fin. This allows the top and bottom V-fins to meet together behind the main fin. You can easily glue the top and bottom V-fins together along this root before sliding them onto the main fin. Construction is now greatly simplified.
I hope this helps everyone who is considering building this model.
Carl, don't put the old 1/16" sheet into production! Use this new pattern.
|