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've never used one. I've always thought they were a solution in search of a problem. Saving a few pieces of treated toilet paper...well, it ain't much of a savings. And, I'm pretty sure they don't really keep all the burn off the chutes all the time. Right?

Fancy motor retaining hardware (eg, Aero Pack): How hard is it to cook up a couple of Kaplow clips? If you're losing motors due to retention issues, maybe you need to take some remedial rocketry classes

Tapered fins: Yeah, I've done a few. Guess what? Unless you're flying competition, they're more trouble than they're worth. They're more prone to breaking, and, as a sport flier, the added altitude only makes them harder to track. Sure, the occasional indulgence is perfectly acceptable, but for those who have a life, square cut fins work danged fine

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.

Clear coats: Over decals? Sure. Over anything else? Use a paint that doesn't need to be clear coated. It's called enamel. Check some out. Save that extra effort for building another rocket.

Q2G2 ignitors: They're awesome. Best commercial ignitor ever for air-starts. But they're not an absolute necessity for ground-started clusters. I've lit many clusters using plain old Solar ignitors, and had excellent results getting all motors lit most of the time, and never had an ignitor related failure. Us old far...timers remember that before Solars, we had nichrome and crap - those were the two choices. Solars were a light years-ahead improvement. Now, 30-some years later, they're still a danged fine ignitor, and all that's needed most of the time.

Alright, that's all I can think of for now, but I'm sure I'll remember three more as soon as I hit the send button...

Doug...feeling rather curmudgeonly...

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YORF member #11

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.

Good thread BTW.

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Never trust an atom. They make up everything.

4 out of 3 people struggle with math.

Chemically, alcohol IS a solution.

NAR# 94042
SAM# 0078

Shock cords--the nose cone and body are zipping apart at a fast, but decreasing velocity. The energy that the shock cord has to absorb is proportional to the square of the velocity. If you want things to stay together, you need to do one of three things:

1--slow down the flying objects more quickly
2--reduce the mass of the objects
3--wait for friction to do its thing and slow them down on its own (i.e. longer shock cord)

Elastic has the nice effect of slowing things down quickly as it stretches, but has the unpleasant effect of snap-back. I strongly prefer chain-stitched (or monkey braided) Kevlar, as it greatly reduces the force on the system while the knots are unfurling, and doesn't snap back. My R & D report at last NARAM measured this and found that the chain-stitched Kevlar took something like 2/3 of the total energy out of the system before actually yanking on the nose cone tether/Kevlar attachment points.

But what do I know? I usually taper my fins

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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Earl L. Cagle, Jr.
NAR# 29523
TRA# 962
SAM# 73
Owner/Producer
Point 39 Productions

Rocket-Brained Since 1970

The Estes tube marking guide. I like the two discs for the different size tubes, but the provided straightedge is somewhat flexible and gives me inconsistent results. I use aluminum angle instead for marking lines on a tube.


Bill

Exactly! The disks are a great tool--the angled straightedge is NOT. Like you, I use an aluminum angle--but I always insert a BT coupler into each end of the tube first before marking so the line doesn't go parabolic.

Now, if only Quest had a set of marking disks for their BT's........

__________________
Never trust an atom. They make up everything.

4 out of 3 people struggle with math.

Chemically, alcohol IS a solution.

NAR# 94042
SAM# 0078

"Cox Sure-Shot ignitor."

Actually, they were Centuri Sure-shots which were invented by Irv Wait and sold by his company Rocket Development Corporation as "Ignit-rite" igniters. Centuri brought Irv in to continue his work on the Enerjet composite motors and changed the igniter's name.

Sure-shots were one of the best products ever. I flew nine cluster flights and only had one motor not fire as the Sure-shot burned, but was pulled out by the clips. The igniter stick was the prefered fire source for the flashbulb ignitors. John Langford (Aurora Flight Sciences) popularized the flashbulb system. Most of my remaining Sure-shot sticks will not burn correctly and mostly smolder. They have been hauled around the country during military service.

Cox did have their own unique igniters that were plugged into a specific holder on their launch pad. It had a pyrogen head that made it look like a match.

Dougie - decaff !!!

Chas

All of the items listed by Doug as useless and overrated I find to be of GREAT use.
ALL my rockets use baffles wherever possible; when constructed properly they provide 100% protection of the chute.
Anything I have BT55 size or larger has a baffle.

Clearcoat EVERYTHING; not doing so is pure laziness or being a cheapskate.

Engine retainers- why not ? It makes things easier.

Anybody that does not understand the benefits of a longer shock cord needs to take a remedial physics course BADLY ! Most of my rockets use a shock cord about 3 times the length as supplied. Never get "estes dents" to the cone or tube either.

I taper the vast majority of all my 3FNC and 4FNC rockets for the extra performance- it takes little extra time and the performance gain is free.

I have ZERO problem with someone Certing level 1 and 2 in the same day that has never before launched a rocket; then again I don't think the cert process should exist AT ALL for flying high-power. If up to me it would be a free-for-all whereever, whenever, devoid of ANY regulation AT ALL !

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When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, and HAVOC !

You crack me up, GH. I'm having fun with this (and hope you are, too).

Didn't you post a while back that you were gonna start using my shock cord setups?

Seriously, (to all), I always use longer shock cords than usually supplied in the kits. That is, long cures short.

But length does't cure high speed deployment. Something else is needed. That's what this particular sub-topic was railing against


Doug

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YORF member #11

Centuri Sure-Shot igniters. Thanks for the correction. No, I NEVER had one fail either.

__________________
Never trust an atom. They make up everything.

4 out of 3 people struggle with math.

Chemically, alcohol IS a solution.

NAR# 94042
SAM# 0078