[roc-chat] Re: [roc-chat] Re: Motor and Case Fitting
- From: "chris_coffee@xxxxxxxxxx" <chris_coffee@xxxxxxxxxx>
- To: roc-chat@xxxxxxxxxxxxx
- Date: Sun, 16 Dec 2012 10:43:40 -0800
That's what I'm thinking, too. Ok, one final question. What is the general
consensus on motor casings being longer than the motor tube? Is it safe to use
a motor that is, say 19.5" long, in a motor tube that is only 10" long
considering the CP is aft of the CG?
Sent from my Verizon Wireless 4GLTE smartphone
----- Reply message -----
From: "Jack Garibaldi" <jackgaribaldi@xxxxxxx>
To: <roc-chat@xxxxxxxxxxxxx>
Subject: [roc-chat] Re: Motor and Case Fitting
Date: Sun, Dec 16, 2012 10:03 am
There is a setting to say the other way around I always just say measure
everything from the tip of the nose or I didn’t see your design maybe you had
something wrong or out of wack on it. Jack G From:
roc-chat-bounce@xxxxxxxxxxxxx [mailto:roc-chat-bounce@xxxxxxxxxxxxx] On Behalf
Of chris_coffee@xxxxxxxxxx
Sent: Sunday, December 16, 2012 12:39 AM
To: roc-chat@xxxxxxxxxxxxx
Subject: [roc-chat] Re: [roc-chat] Re: Motor and Case Fitting Thanks, Jack.
This will help a lot. The only reason I said the CG was behind the CP is
because that's what openrocket has it at. That's what had me confused because I
knew it was suppose to be the other way around.
Sent from my Verizon Wireless 4GLTE smartphone----- Reply message -----
From: "Jack Garibaldi" <jackgaribaldi@xxxxxxx>
To: <roc-chat@xxxxxxxxxxxxx>
Subject: [roc-chat] Re: Motor and Case Fitting
Date: Sun, Dec 16, 2012 12:23 am I also noticed you said the CG behind the CP
everything is measured from the tip of the nose so the CG is forward the CP not
Behind it. Jack G From: roc-chat-bounce@xxxxxxxxxxxxx
[mailto:roc-chat-bounce@xxxxxxxxxxxxx] On Behalf Of Chris Coffee
Sent: Saturday, December 15, 2012 9:41 PM
To: roc-chat@xxxxxxxxxxxxx
Subject: [roc-chat] Motor and Case Fitting Hello everyone, I am currently in
the process of building a Madcow 4.0” Fiberglass Little John. It has a plastic
nose cone with a fiberglass wrap on the inside (not sure if there is a actual
nomenclature for that design) and a 10” long 54mm motor mount. The instructions
state the “estimated” CP is at 36”. I have put together a simulation with
OpenRocket to the best of my knowledge (I am certainly no expert with the
program) and I am seeing a slight problem. According to O.R. the CP is at
34.508 in. and the CG is at 35.196 in.! When I add weight to the nose cone, in
order to get the CP at least 4.0” behind the CG I have to add approximately 18
oz. of weight. To me that just seems a bit drastic so I figured I would put it
out here and see if I can get some advice on what to do. I have attached the
copy of what I have done with O.R. to this point. As of now the parachute is
just a experimental size because I am not sure what size to use. Was told to
wait until I get the rocket built and then we could figure it out, so I am just
playing with ideas here when it comes to the chute. Christopher L. Coffee
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