[tccrockets] Re: Who remembers the story?

  • From: Bob Feretich <bob.feretich@xxxxxxxxxxxxxxx>
  • To: tccrockets@xxxxxxxxxxxxx, JAMES FRANCO <ALDOCYBER3@xxxxxxx>
  • Date: Thu, 26 May 2022 12:16:46 -0700

My guess is that the rocket body was not sufficiently vented.

A 8" body tube has a cross-sectional area of just over 50 sq inches. A 1.2 PSI pressure differential (inside to atmosphere) is all that is needed to break sheer pins rated for 60 lbs.


On 5/25/2022 9:09 PM, JAMES FRANCO wrote:
Fwd: [tccrockets] Re: Drag separation    
Here is the original email string from the chat. We used to have good discussions on the chat, let's start that up again.

-----Original Message-----
From: Jimmy Franco <aldocyber3@xxxxxxx>
To: tccrockets@xxxxxxxxxxxxx
Sent: Mon, Oct 21, 2013 7:22 am
Subject: Re: [tccrockets] Re: Drag separation

Robert pretty sure the nosecone is in the trailer, but it had some shoulder damage on it.   Jimmy F.
TRA 12524   From: Cliff Sojourner Sent: Monday, October 21, 2013 12:04 AM To: tccrockets@xxxxxxxxxxxxx Subject: [tccrockets] Re: Drag separation   On 2013-10-21 00:03, AiRobert wrote:
Yep, that looks like it. Where did it end up at?

on Bruce's head, duh!

From: tccrockets-bounce@xxxxxxxxxxxxx [mailto:tccrockets-bounce@xxxxxxxxxxxxxOn Behalf Of Ryan G. Coleman
Sent: Sunday, October 20, 2013 9:53 PM
To: TCC Rockets
Subject: [tccrockets] Re: Drag separation   Is this the nose cone you're looking for?
  On Sun, Oct 20, 2013 at 9:33 PM, Jack Garibaldi <jackgaribaldi@xxxxxxx> wrote: That body and fins you had was pretty big and draggy, when I left your black nose cones was on the table   Jack G   From: tccrockets-bounce@xxxxxxxxxxxxx [mailto:tccrockets-bounce@xxxxxxxxxxxxxOn Behalf Of AiRobert
Sent: Sunday, October 20, 2013 9:28 PM
To: tccrockets@xxxxxxxxxxxxx
Subject: [tccrockets] Drag separation   Apparently the nosecone drag separated on my rocket Friday, even though I had three #2 nylon shear screws installed. As I understand it, drag separation is caused by the airframe and fins having more drag than the nosecone, so the airframe slows down faster than the nosecone (After the motor quits). According to Rocket Materials http://www.rocketmaterials.org/datastore/cord/Shear_Pins/index.php The three pins should have held about 60 pounds of force. After re-running RockSim with the biggest motor available the maximum deceleration was about 200 feet/sec/sec. (The actual motor used showed about 150 f/s/s deceleration.) That is about 6.25g of deceleration. Assuming that the nosecone produce no drag it would mean that the nosecone would have to weigh 10 pounds to break the shear pins. While I haven’t weighed the nosecone I’m sure it’s less than 10 pounds and that it also produces some drag and that the total deceleration was less than 6.25 g.   Am I missing something on the calculations?   Robert Zylstra PS Anyone find a 7.5 inch black plastic nosecone?  
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Jimmy F.
Tripoli Rocketry Association
Member 12524
Level 3

Sent: ‎Wednesday‎, ‎May‎ ‎25‎, ‎2022 ‎21‎:‎01
To: tccrockets@xxxxxxxxxxxxx
First of all this story is related to Robert Zylstra, I loved hanging out with that guy.
So the story is a good lesson in rocket aerodynamics and the force the air imposes moving over a rocket’s airframe in conjunction with motor burnout, specific to drag separation. We should all try to learn something from each of our flights and other’s flights as well, makes us better fliers and safer.
I came across this old email today from 2013 which I will forward next.

Jimmy F.
Tripoli Rocketry Association
Member 12524
Level 3

From: Rob Diehl
Sent: ‎Wednesday‎, ‎May‎ ‎25‎, ‎2022 ‎19‎:‎54
To: tccrockets@xxxxxxxxxxxxx
L3 attempt gone wrong?  
I know there have been problems with Der Red Max launches 

Sent from my iPhone
On May 25, 2022, at 5:25 PM, JAMES FRANCO <aldocyber3@xxxxxxx> wrote:

The nose cone is from a 8" Der Red Max

Jimmy F. TRA 12524 L3
-------- Original message -------- From: Bruce Rohn <bhrohn@xxxxxxxxx> Date: 5/25/22 16:58 (GMT-08:00) To: tcc-chat <tccrockets@xxxxxxxxxxxxx> Subject: [tccrockets] Re: Who remembers the story?
Hello, I am Conehead Bruce, I am from France and I eat MASSIVE QUANTITIES!!!!!
On Wed, May 25, 2022 at 3:39 PM Rob Diehl <dmarc-noreply@xxxxxxxxxxxxx> wrote:
I remember the pic. I don’t remember the story. 

Sent from my iPhone
On May 25, 2022, at 3:23 PM, JAMES FRANCO <aldocyber3@xxxxxxx> wrote:


Jimmy F.

Tripoli Rocketry Association

Member 12524

Level 3

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