View Single Post
  #7  
Old 11-06-2010, 08:28 PM
CPMcGraw's Avatar
CPMcGraw CPMcGraw is offline
BARCLONE Rocketry
 
Join Date: Mar 2005
Location: Mobile, Alabama
Posts: 5,355
Exclamation 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.
Attached Thumbnails
Click image for larger version

Name:  Lil' Leaguer 3D.jpg
Views: 139
Size:  45.8 KB  Click image for larger version

Name:  Lil' Leaguer 2D.jpg
Views: 111
Size:  92.6 KB  Click image for larger version

Name:  Lil' Leaguer VFin Enlarged.jpg
Views: 103
Size:  27.1 KB  Click image for larger version

Name:  Lil' Leaguer Fin Sheet 2 Corrected.JPG
Views: 99
Size:  73.2 KB  
Attached Files
File Type: rkt Lil' Leaguer.rkt (126.1 KB, 107 views)
__________________
Craig McGraw

BARCLONE Rocketry -- http://barclone.rocketshoppe.com
BARCLONE Blogsite -- http://barclone.wordpress.com
BARCLONE Forum -- BARCLONE Forum

BARs helping BARs

SAM 0044
AMA 352635
Reply With Quote