Need help on launch lug sizing

[Ken PlattnerParticipant]

Thanks Chris. I’ll be up Friday to launch the small rockets with the kids. I’ll look for you Saturday…

[Chris LaPanse]

Great – I’m headed up saturday, as I said, and I’ll be there until it starts to wind down on Sunday. I look forward to seeing this cluster project 🙂

[new2hprParticipant]

I’ve built up a stubby cluster rocket (3″dia, 25″ long) with 3 24mm mounts. Due to heavy epoxy and G10, it weighs right around a pound. I was planning to use my existing 4′ long, 3/16″ rod for it, but now I’m questioning that logic. My pad will take up to 3/8″ rod and I don’t plan to go to a rail just yet. 😉 Any thoughts on how much whip I might get with this setup or should I tear it off and go bigger. It’s already painted, though…

On the cluster side, I just finished a relay setup that should be good for up to 40A (battery and relay at pad). I want to try it out at a local field (Sandstone Ranch) on 3 D12s, then 3 E9’s. Stability on the E’s low velocity might be interesting. Might need a longer rod.

If it works, maybe I’ll get it to Octoberfest. Watch for the Hot Pink Suppository of Discomfort.

Thanks for any help.

[Ed Dawson]

I hate to be the bearer of bad news, but you’ll probably need to pull those 3/16 launch lugs of and replace with at least 1/4″.

I assume the 1 pound weight you were talking about was without the motors loaded. Plus, with the cluster, if one motor does not ignite your thrust will be off center and add even more rod whip.

That’s my two cents worth….

[Chris LaPanse]

I too would go with 1/4″ minimum, though a rail would be the optimum.

[Tim Thomas]

Seams a little light to me, but if you don’t want to take off the old because of the paint, you might think about adding a set of rail buttons. They are small and easy to add and you would be good to go for Oct. A rail will end all whip problems. Speaking of whip, if you come to Octoberfest a whip for those Estes motors would help. Several of the guys will have them, and you can borrow mine if you like. Brian from Rocket Garden has some real nice ones for sale for very little money. See you there! 8)

[new2hprParticipant]

Rocksim puts the weight at 19oz with 3 E9’s loaded. I don’t have a scale to check it for real. Anyone know where I could pick up a decent one for little $? I’d only need to weigh stuff under a couple lbs. (for now!) 😉

Being an EE, I’m not afraid of some solder. I made up a whip to go along with the new relay system. It has banana plugs on the end of it. Don’t know how that might hook into the club system. If there are big enough alligator clips, they could hook onto the plugs.

Adding the buttons sounds like the quickest fix for Oct., but won’t let me test-fly it beforehand. Maybe carefully slicing the lug off, sanding with paper around the new lug, and epoxying it on would be ok. I could always make it pretty later.

What do you use for larger lugs? Aluminum, copper tubing or special rocket stuff?

On a side note, at >16oz, does anyone have the FAA number to call in a notification? How much notice do they need before flight? Yet another advantage to flying with the club…

Thanks for all your inputs!
Ken

[Warren B. MusselmanModerator]

The club takes care of all FAA notifications for flights at club sanctioned launches. We have the waiver, you don’t ever need to worry about it.

As for the lugs, I would strongly recommend you avoid lugs for anything larger than 1/4″ – it’s old news and most folks use rail buttons or rail guides of some sort. If you must use a launch rod, go 1/4″ or 3/8″. You can buy lugs at Hobbytown or brass tubing to fit at most any hobby shop.

I personally recommend Acme conformal rail guides for models the size you’re talking about and use JB Weld to glue them onto the airframe.

Warren

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