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  #11  
Old 10-19-2010, 08:40 PM
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blackshire blackshire is offline
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Quote:
Originally Posted by tbzep
I cut the finger tab off and use that end at the thrust ring end for all those reasons, plus because the finger tab looks ugly to me.
Before Semroc came back and began offering the old-style motor clips, I also did that with the finger tabs (although I still keep un-cut ones from Estes and Quest kits in case I'm ever out of Semroc motor clips when I want to do a scratch-build). Aesthetically, I've also always found the finger tabs unsightly--the old-style motor clips are just as functional without being prominently visible.
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  #12  
Old 10-19-2010, 08:46 PM
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Royatl Royatl is offline
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Quote:
Originally Posted by Doug Sams
At the risk of starting trouble, for which I'm in the mood , I'm listing some of the doo-dads and habits common in this hobby for which I have great skepticism of their net benefits.

Baffles:

I like em. But of course, they're not a complete panacea. You still have residue and heat damage that accumulates, and they add weight.

Quote:
Fancy motor retaining hardware (eg, Aero Pack):

Agreed.

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Tapered fins:

I assume you're dumping rounded and airfoiled fins in with them.
I still prefer them cause they just look cooler.

Quote:
Long shock cords:

Somewhat with ya on this, as far as the extreme is concerned. Two or three times body length is plenty, but the CW around here is "if theres still room in your chute compartment, you aren't using enough shock cord."


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Clear coats: Over decals? Sure.

But if you don't put it over everything, it's probably gonna look ugly at some point. Either use it all over or don't use it at all.

Quote:
Q2G2 ignitors: They're awesome. Best commercial ignitor ever for air-starts. But they're not an absolute necessity for ground-started clusters.

Sure, but doesn't matter. If I have the Q2G2s for a cluster, I'm gonna use them before I use Solars. Of course, I was here when Langford first put SureShots to AG-1's and we were flying 20 - 100 motor clusters out on I-85 in Doraville. It got to be where some of our club members were using flashbulbs regularly for single motors!
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  #13  
Old 10-19-2010, 09:03 PM
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Originally Posted by cas2047
-SNIP- I find that longer shock cords help to prevent damage to the rocket and cone (if it's balsa) from the nose cone whipping back and hitting the rocket. It also seems to prevent zippering. Although I can't back that up with anything more than my own personal experiences. -SNIP-
With elastic and Kevlar/elastic shock cords, that's been my experience as well. Because the rocket is usually still moving slowly at ejection, when the nose cone snaps back the rocket body isn't in the same location it was in when the nose cone popped off, and it usually misses the rocket body. Watching ejections on low-altitude flights, I can see the whole rocket body/shock cord/nose cone assembly begin to perform a slow end-over-end somersault when the nose cone snaps back (until the parachute inflates or the streamer unfurls and "takes hold").

For lightweight BT-5/ST-5 to BT-50/ST-10 size rockets, I've found that (as Chan Stevens' NAR R & D Report indicated) a non-elastic shock cord of Kevlar works just fine. I usually use 18" to 24" of 100# Kevlar cord. Thick cotton string also works well for this application, although it does get singed and has to be replaced sooner than Kevlar.
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  #14  
Old 10-19-2010, 09:17 PM
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John Brohm John Brohm is offline
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Quote:
Originally Posted by Doug Sams


<grumble, grumble, wrong side of bed, etc...>

Long shock cords: Whoever came up with the foul notion that making the shock cord longer solves the problem of high speed deployment needs to take a high school course in physics. If your rocket is plunging toward the earth at 400mph, I don't care if the shock cord is 300 feet long, when the rocket gets to the end of the cord, there's gonna be one heckuva a jerk on the airframe, the suspension lines and the recovery harness. You can quote me on that.

< grumble, grumble, bad hair day, etc... (wish I could have bad hair...)>

Doug...feeling rather curmudgeonly...

.


All true; but I will say that in my experience, the occasional long shock cord has, on more than one occasion, made for me the difference between retrieving or leaving a rocket in a tree. I'm just saying...
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  #15  
Old 10-19-2010, 09:20 PM
tfischer tfischer is offline
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Quote:
Originally Posted by John Brohm
All true; but I will say that in my experience, the occasional long shock cord has, on more than one occasion, made for me the difference between retrieving or leaving a rocket in a tree. I'm just saying...


Please elaborate...
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  #16  
Old 10-19-2010, 09:47 PM
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Quote:
Originally Posted by jeffyjeep
Hi Doug. I agree with most of your points--except for one: long shock cords.

I make shock cords WAY too long for 2 reasons: 1) a shock cord that's too long can be repaired and retied several times before it becomes a too short shock cord, and 2) from my experiences with rockets with heavily-wieghted nose cones, a short shock cord can and HAS broken on laundry deployment, or the NC has sprung back and damaged the BT end.

To summarize, I prefer to use an elastic fabric shock cord that's too long. But hey, everyone's different. .


I'd second both these points. I also in a number of cases, especially rockets with payload sections or large nosecones, have the rocket come down in separate sections on separate chutes. Tends to solve a fair number of recoil damage problems, but more items to keep up with in the sky (though spectators like to see the 'extra' chutes).

Earl
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  #17  
Old 10-19-2010, 09:53 PM
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Quote:
Originally Posted by tfischer
Please elaborate...


Where we fly there is this long row of trees that runs down the middle of the recovery fairway. Most rockets that have the misfortune of landing in these trees seldom catch in the tops, but instead in branches to the side. A longer shock cord means the rocket hangs lower, and at least increases the chances of a successful retrieval.
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  #18  
Old 10-19-2010, 09:58 PM
tfischer tfischer is offline
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Quote:
Originally Posted by John Brohm
Where we fly there is this long row of trees that runs down the middle of the recovery fairway. Most rockets that have the misfortune of landing in these trees seldom catch in the tops, but instead in branches to the side. A longer shock cord means the rocket hangs lower, and at least increases the chances of a successful retrieval.


Cool. I could see it going both ways - a smaller cord might not catch at all, whereas a longer one might loop over a high branch and hang down from both sides. I guess if you can somehow pull it down though, that's when it pays off
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  #19  
Old 10-19-2010, 09:58 PM
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Quote:
Originally Posted by tfischer
Please elaborate...
Having seen some High Power Rockets with l-o-n-g shock cords (a great example can be seen descending under a main parachute and a small pilot 'chute on page 51 of The Model Rocketry Handbook: 21st Century Edition by Stuart Lodge), the main body of such a "treed" rocket could easily dangle down close enough to the ground for the rocketeer to reach up and gently "shake 'n tug" the rest of the rocket down from the tree's branches.
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  #20  
Old 10-19-2010, 10:05 PM
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Quote:
Originally Posted by tfischer
Cool. I could see it going both ways - a smaller cord might not catch at all, whereas a longer one might loop over a high branch and hang down from both sides. I guess if you can somehow pull it down though, that's when it pays off
Unfortunately, even shorter shock cords can wrap themselves around branches or overhead wires. My nephew's streamer-equipped Estes Athena (the older E2X kit with the Generic E2X white plastic fin unit and the aluminized nose cone) wrapped itself around a telephone wire several times... :-(
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