How many launch lugs?
 

18" Rocket , BT-80 Tube, 10.4 ounces.

How many launch lugs should I put on?

Comrade:

One, two inches long, centered on the CG or as close as you can to it.

Thank you!

47 should do it nicely.

Just joking. Something that large I would always go with two.

Yeah, I'd hate to have to say "I should have....."

You can get 12" long launch lugs at Balsa Machining.

I don' t think that you'd need 47 of those, but safety first.

If I were me, I'd go with two.

On a relatively long design like yours, I like to put one lug on or immediately behind the c.g. and a second small lug on the forward edge of the body tube. This applies to sport designs but not to most competition designs.

My thinking: two lugs spaced apart minimizes the friction of a rocket trying to twist on a single lug, at least until it gets a little velocity started and until the top lug clears the launch rod.

I also like to touch up the tip of the launch rod to make sure there are NO burrs or rough spots to snag a launch lug.

You are you, aren't you? :eek: :D

If performance is a concern, listen to the old guys that routinely competed in altitude. They wanted the least friction in addition to the least amount of tip-off. Most migrated graduated to towers, rails, and piston launchers (do they still allow that in any events?), but I bet they have a good grasp on lugs and rods too.

If performance isn't a concern, look at the rocket and see what makes it look good. A single longer one near the CG works. Big Bertha kits have been made like that for decades. A single long one near the aft end works. A shorter one at the aft end and another near the CG works, like with the old Cobra 1500 and Mean Machine. A shorter one near each end works if it's not a long rocket. The Cherokee-D was designed and built that way for years. In short, it won't matter a whole lot unless you just stick one short lug on the rocket.