How important is the Launch lug location? I know that it can't interfere with the fins hitting the launch rod etc. . I also know that most are located so you see the belly of the rocket. but aside from that does it matter?
And that bit matters a lot.Close to the CG-CP area, so that there's less leverage trying to rip it off.
How important is the Launch lug location?
On the side, parallel with the long axis of the rocket, somewhat middle-ish. <<- as precise as you need to be 95% of the time for LPR
I saw in someone's build thread that he had placed a lug on the face of a fin instead of adding a dedicated stand-off. Genius.I have seen some off-set away from the rocket to support a wider section (HoJo, I'm looking at you!)
I saw in someone's build thread that he had placed a lug on the face of a fin instead of adding a dedicated stand-off. Genius.
I am with Joe on this one. Unless it is a very long rocket, or it is going to be on the pad for a long time (happens at some club launches where the racks are loaded in shifts), I don’t think the CP Location matters much. For the above cases, breezes blowing while rocket is on the rod will cause a bending force if the lug is away from the CP. this can break off the lug while it is sitting on the rod on the pad.I usually put them alongside fin roots. If the fin is straight it guarantees the lug is straight, and the fillet partially hides it.
aerodynamically, not sure if it results in more or less drag than an isolated lug separate from the fin joint. maybe @BEC knows that one.
I use a rod as well when I have two lugs, but in a different process.I now use a rod to:
- Ensure alignment between the upper & lower lugs And helps align them to the marked line for the lugs. Slip them onto the rod, add a bit of glue, then roll them into place. Secure [the rod] with a piece of tape.
- Keeps them round / fit the intended rod.
- (Also keeps glue out of the lug!)
Also, I like to use a slightly oversized rod, or add tape to a standard rod, so it's snugger in the lugs than the actual rod at launch time will be. That ensures even more accurate alignment, and is better at keeping the lug round if there's any need for that.
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