Question re TrueModeler Sentry ATA

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Murrill

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Several years ago I purchased the Sentry ATA from TrueModeler; however, I never took it out of the box until last week. I'm almost through with construction, but I found the nose cone weight was missing. Can someone please tell me how much the piece weighed? I can easily substitute a fishing weight, but I need to know how much weight to use.
Thanks!
John Murrill
 

powderburner

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Welcome, Murrill!

The only thing I know about the Sentry is what I can read on the EMRR review. The guy who wrote it includes a list (rather complete-looking) of parts in the kit but does not list any ballast weight. Maybe someone here on TRF has more info?

A side note: we are glad you have joined us here, and hope to see you back often. But for this kind of query, you really only need to post it once on one forum. These guys are pretty good about helping, and you can bet they will notice your question anyplace you post it.
 

mkmilion

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If you can figure out the exact wieght or what it was to begin with. I suggest that you hop on over to your local Dollar Store and pick up some modeling clay, you get like four different colors, anyway. Load it your NC up with it, until it is balanced.
If you don't know how to balance it: All you have to do is tie a string through the LL and swing in a circle and watch how it acts. If flies backwards, add more weight to nose. I hate to admit it but I don't know how it'll fly if the nose is too heavy. I've never had that problem.
Okay I hope that helped. BTW you kinda have to have it constructed in order to do the test, but I'm pretty sure you guessed that.
And again WELCOME THE TRF!!!
 

powderburner

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Actually, you don't tie a string through the launch lug. You find the longitudinal center-of-gravity of the fully loaded, flight-ready bird by balancing it (on your finger will do fine; no need to use a knife-edge for precision).
At this point you will probably want to wrap the BT several times with string to create sort of a girdle; you tie your swing-test tether to that girdle. Before testing you can fine-tune the tether attachment by sliding the girdle up or down the BT so the rocket hangs level.
The LL may or may not be on the c.g., and in any event, may or may not take the abuse of swing-testing without tearing. Balancing the rocket with respect to the LL is a bit of a gamble. You are after the proper c.g.-c.p. relationship.
 
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