Launch Lug Placement and Launch Rod Length

[gary7]

2 Items regarding launch:

1)Does anyone have a reference or thought as to where to place a launch lug on a rocket? Are two, 3 inch lugs better than one, six inch lug? What about placement? Middle of main air frame tube or closer to the bottom? Or both if you use two lugs? Thanks as always.

2)How do you determine the optimal rod lenght? 1.5 x or 2 x the rocket length or is there a generally accepted formula for determining this?

 

[Micromeister]

2 Items regarding launch:

1)Does anyone have a reference or thought as to where to place a launch lug on a rocket? Are two, 3 inch lugs better than one, six inch lug? What about placement? Middle of main air frame tube or closer to the bottom? Or both if you use two lugs? Thanks as always.

2)How do you determine the optimal rod lenght? 1.5 x or 2 x the rocket length or is there a generally accepted formula for determining this?

Gary:
Regardless of rocket size I consider launch lugs at best a necessary evil. Personally if I'm using LL's or rail buttons they will be as small as I can possibly get them, nearly always two instead of one with one tucked in a fin/body joint fillet toward the leading edge and the other just shy of the loaded CG of the model. The Forward lug will be as small in length as I can make it or be a wire ring "Antenna" so it sort of looks like it's supposed to be there

Launch rod length is dependent on the models speed at exit not the length of the model.

 

[dave carver]

Two 1" lugs, 1 at the CG the other on the bottom. Slash the ends to a 45 degree for less drag.

Rod length if you arn't sure is best determined with a sim like WRASP or one of the many others. They will tell you the speed of the rocket at the end of the launch rod. I believe 50 mph is the goal your looking for.

Google WRASP and install, find the rocket with the same diameter and enter your rockets weight and motor and give it about .8 drag and run the sim. Many factors including altitude of launch and temp and barometric pressure(I think) can be changed


p.s: The Gary Seven episode of Star Trek is my favorite one of all with the bonus of Terry Garr