CP for LOC EZI-65 NEEDED

CP for LOC EZI-65 NEEDED

Post by szwa.. » Mon, 22 Aug 1994 13:31:49



Help! I am building a LOC EZI-65 with a beefed up recovery system (0.25in
bungee,motor mount strap ala PML etc.) and want to check the CP-CG
relationship prior to launch. I called LOC and they would not tell me the
location of the CP. I would rather not use the Barrowman equations (I am
a math dunce :-) ) and would very much appreciate it if someone could
supply the dimensions. Thanks for the help.

William F. Walby
TRA#2904
AeroPac#102
NAR#60661

 
 
 

CP for LOC EZI-65 NEEDED

Post by kaplo.. » Wed, 24 Aug 1994 02:29:15


Quote:

> Help! I am building a LOC EZI-65 with a beefed up recovery system (0.25in
> bungee,motor mount strap ala PML etc.) and want to check the CP-CG
> relationship prior to launch. I called LOC and they would not tell me the
> location of the CP. I would rather not use the Barrowman equations (I am
> a math dunce :-) ) and would very much appreciate it if someone could
> supply the dimensions. Thanks for the help.

Back around Danville-5 (1991), I attempted to put together a list of all kit
CPs. I got minimal cooperation from manufacturers. LOC particularly was hard
to get data from, even thou I made up some neat sheets to get what I needed.
Their concern was that if they told their customers where the CP was, then
thy might do something like load up an Ultimate until it had 7 H motors in
it, and then it wouild be unstable and/or shread.

None-the-less, I managed to complete a list of CPs for  something like 100
HPR kits. I don't have it handy, but it should still be on one of my home
systems. I'll try and find it tonight, and post the list here. Please note
that the list is copyrighted by yours truely. I am willing to make it
available to the net, for personal use only (specifically NOT for
publication in any magazine, newsletter, etc without my permission), and
without any claim of accuracy, etc. (in otrher words, you can't sue me if
I'm wrong). Since much of the data came from elsewhere, I can't vouch 100%
for what is there. I'll also try and dig up my "input form", post it, and
request data on unlisted models from the net. Maybe this can be the start of
a new "FAQette" of CP data...


USPO:   HealthCare COMPARE Corp. 3200 Highland Ave Downers Grove, IL 60515
TPC:    (708) 241-7919 x5327            ICBM:   4149'48" North 880'51" West

        BATF: Doing to Model Rocketry what they did to Waco, Texas :-(

Disclaimer: If this message is caught or killed, the secretary will disavow
any knowledge of my actions. These bits will self destruct in 5 seconds....

 
 
 

CP for LOC EZI-65 NEEDED

Post by kaplo.. » Wed, 24 Aug 1994 21:33:08


Quote:

> Help! I am building a LOC EZI-65 with a beefed up recovery system (0.25in
> bungee,motor mount strap ala PML etc.) and want to check the CP-CG
> relationship prior to launch. I called LOC and they would not tell me the
> location of the CP. I would rather not use the Barrowman equations (I am
> a math dunce :-) ) and would very much appreciate it if someone could
> supply the dimensions. Thanks for the help.

One more thought: I suspect that LOC didn't tell you where the CP was for 2
reasons: (1) liability, and (2) they don't know where it is! As sad as it
may seem, you don't have to be a rocket scientist to sell rockets. I suspect
that the great majority of rocket kits on the market today have never had
their CP computed by the manufacturer. I doubt that there is much difference
between model rockets and HPR rockets, either. There are an awful lot of
manufacturers out there who just build a rocket, and if it flys OK, then
sell the kit. I'm sure there are even some who don't get too hung up on the
flight test step, and sell it anyway, or never bother to try (consumer
testing).

At least you, as a user, had the intelligence to ask the question, and know
what a CG and a CP mean. I think that even that concept is beyond some folks
I've met.

I would really like to see EVERY HPR kit have a CP location in its
instructions. I wouldn't hold my breath waiting for that to happen. It's
really outside the safety codes, so they don't have to tell you. But as an
RSO, I just might demand that YOU know where it is, before I let the model
fly on MY range.

They claimed to do this once at Danville-5. This was the launch after the
"incident" with the pod rocket. There were all these grand plans about
strict RSO safety checks, CP and CG marked on each model, etc. I brought my
non-portable computer down, and spent most of the weekend in my room doing
CP calculations. Once done, no one ever bothered to check for stability or
naything else at the RSO desk anyway. They haven't done so since. They even
had another land shark rocket just like the time before. This one didn't
hurt anyone for 2 reasons: (1) the outboard motors were not detachable, and
(2) it randomly picked a direction away from the people and buildings to
power prang.

Suffice it to say that I've never seen a stringent a safety check at a
Tripoli sanctioned launch as was done to my E DEL model at NARAM-36. This
goes back to the post regarding trhe high expected failure rate at HPR
launches. It need not be so. The purpose of the RSO is to have an impartial
expert double check everything on your model, as if someones life depended
on it. It just may.


USPO:   HealthCare COMPARE Corp. 3200 Highland Ave Downers Grove, IL 60515
TPC:    (708) 241-7919 x5327            ICBM:   4149'48" North 880'51" West

        BATF: Doing to Model Rocketry what they did to Waco, Texas :-(

Disclaimer: If this message is caught or killed, the secretary will disavow
any knowledge of my actions. These bits will self destruct in 5 seconds....

 
 
 

CP for LOC EZI-65 NEEDED

Post by C. D. Tavar » Fri, 26 Aug 1994 05:15:00


Quote:

> Suffice it to say that I've never seen a stringent a safety check at a
> Tripoli sanctioned launch as was done to my E DEL model at NARAM-36.

But that was your rocket, Bob.    :-)
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