Author Topic: L1 cert for a Madcow V2 4" kit....  (Read 8690 times)

Offline grub00

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L1 cert for a Madcow V2 4" kit....
« on: July 31, 2016, 04:21:09 PM »
Hi there! I'm new to the forums and have just recently joined URRG.  I'm in the process of building my first high powered rocket and have a couple decisions that I'd like some advice on:

  • Motor casing size: I'm not certified and would like to use the V2 kit for my L1 and eventually L2 cert.  However, I'm at a bit of a loss to figure out how to manage that with the large motor diameter of this kit (54mm).  I've been looking at the Cesaroni casings, and they seem to come in certain lengths that correspond with the number of 'grains' you can stuff in a motor charge. I'm assuming that its common practice to get the biggest casing that you reasonably fit into your rocket and then you have more options with your motor selection.  So long term, I'd like to buy longest casing I can, but I'm wondering if this would allow me to put a single grain burn motor for L1 and L2 certification? Then, after my certs are done, I would be able to ramp it up and put higher power motors in the same casing. My alternative would be to buy 2 casings to accommodate the different use case, but that seems more expensive.
  • The second question is related: How do you adjust the ballast of the nose cone to accommodate different wight casings and motors? The kit I'm building comes with instructions that say to epoxy lead shot behind the nose cone bulk plate. That seems pretty permanent and non-adjustable :) Is there some system that you all have seen that anticipates a changing center of gravity?

Offline Bob Krech

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Re: L1 cert for a Madcow V2 4" kit....
« Reply #1 on: August 01, 2016, 12:43:29 AM »
Before you purchase anything, you need to understand several things about hobby rocketry motors.

1.)  Commercial hobby rocket motors are standardized to certain motor casing diameters and certain grain lengths.

2.)  For CTI, the casing diameters are: 24 mm, 29 mm, 38 mm, 54 mm, 75 mm, 98 mm and 150 mm.

3.)  For each casing diameter there is a nominal grain length: 1G in 24 mm is 1.25" long; 1G in 29 mm is 1.75" long; 1G in 38 mm is 2.30" long; 1G in 54 mm is 3.31" long; 1G in 75 mm is 5.33" long; 1G in 98 mm is 6.06" long; and 1G in 150 mm is 8.04" long.  The uniform grain length make it convenient and economical to assemble motors.

4.)  For each casing diameter there are nominally 7 casing lengths: 1 G, 2G, 3G, 4G, 5G, 6G and 6GXL.  We'll ignore the 6XL motors for now since the grain lengths used can be different than the nominal grain length for the casing diameter.

1G in 38 mm is nominally ~120+/-  Ns, 1G in 54 mm is nominally ~ 400+/- Ns.

5.)  You can not only purchase the longest motor casing for a given casing diameter.  This is not allowed by the certification authorities for safety and performance reasons, so you have to buy several casing lengths in a given diameter if you want to use all the reloads in a given diameter.  To reduce the cost to the user, there are 1G spacers that allow you to use a longer casing than the reload would normally require.  For example, if you use a 3G reload you would normally use a 3G casing, however you can use a 4G casing with a 1G spacer, or a 5G casing with (2) 1G spacers.  You are only allowed to use a maximum of (2) 1G spacers in a larger casing so for example you can not use a 6G casing with (3) 1G spacers because using (3) 1G spacer is not allowed by the certification authorities.

6.)  The CTI has starter casing sets that consist of (1) 3G casing, (1) 6G casing, (2) 1G spacers, 1 delay adjustment tool, and in certain diameters forward and/or aft closures.  This allows you to use 1G thru 6G reloads with only (2) motor casing lengths.

7.)  38 mm starter casing sets cost $110 and 54 mm starter casting sets cost $220 from AMW Pro-X.

8.)  Smaller diameter casings are less expensive than larger diameter casings.

9.)  38 mm reloads are less expensive than 54 mm reloads because they have a lower total impulse and contain less propellant.   For example, a 1G 38 mm Blue Streak propellant cost $8 whereas a 1G 54 mm Blue Streak propellant cost $20.  The other components of the 38 mm reload costs ~$16 whereas the other components of the 54 mm reload cost ~$31.

The 2.6" FG Mad Cow V2 is a fine rocket but it is not one I would recommend as your first high power kit for several reasons.  It uses more expensive 54mm motors instead of less expensive 38 mm motors, and it is quite sensitive to CG location and will require nose weight for a stable flight so it's really not a good first high power rocket, and it is not set up for electronic deployment which will make recovery easier when you go high on a L2 motor.

A better choice for your first high power rocket in a Mad Cow 2.6" FG kit would be a dual deploy ready DX3, Screech, or Tomach with a 38 mm motor mount.  (They are basically the same rocket with slightly different fins.)  They can be flown with, or without, dual deploy, with, or without, electronics, and with, or without, the payload section.  They are much more versatile than the 54 mm V2, and much less expensive to launch, and more important to a newbie, you are less likely to loose it.

1.)  You can do your L1 without electronics in an apogee deploy motor ejection mode.  A simple up and down flight on a 3 grain Pro38 mm H motor.

2.)  You can purchase a PerfectFlite StratoLogger and build your e-bay and install the altimeter and simply monitor your next few flights on 3G or 4G H motors.

3.)  When you are comfortable with the electronics, set up the rocket for dual deployment and do that with a 4G or 5G I motor.

4.)  After you are comfortable with dual deployment , go for your L2 cert using the dual deploy with a 5G or 6G reload.

You can always buy the V2 first, but this is an easier approach to get to L2 using one rocket.

YMMV

Bob 








Offline dbmccann

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Re: L1 cert for a Madcow V2 4" kit....
« Reply #2 on: August 01, 2016, 11:01:25 AM »
Welcome!   Many things to decide, and many options to choose from.

First I agree with Bob-  the V2 is a difficult kit that you may find frustrating to learn with.  Short rocket + small fins can be maddening.   There are dozens of options, but the suggestion of a 2.6" kit is a good one (I'm bias, I have a Screech that I fly to around 9,000' on 38/1200 motors and love it.  If you're interested in it, I've got flight videos and photos I can share, and a build thread here http://urrg.us/smf/index.php?topic=26.0. I even built a second one with a 54mm mount here- http://urrg.us/smf/index.php?topic=60.0)  Something long, stable and between 3 and 6 pounds makes for a good L1/L2 bird at Potter.

Bob covered CTI.   The other two major brands are Aerotech, and Loki Research.  (Don't be confused by the research,  they're commercial motors). Both these brands size their cases by approximate impulse.   This is a brief overview of AT's 29mm systems- http://urrg.us/smf/index.php?topic=146.msg1153#msg1153
Typically, people wind up getting multiple cases. 

Loki cases  use reusable nozzles, which lowers reload costs a bit.  A large portion of the Loki L1 38mm loads ship without a hazmat fee.  All CTI has this fee, and most 38mm AT.


This was my old 38mm set.  AT 360 and 720 cases,  CTI 1, 3 and 6 grain.   two spacers in each set let me fly 1-6 grains in each system.  I found myself only flying 3 or 6 though, so the spacers never got used.




If you're set on using the V2, It is possible to get a 3 grain 54mm case and use spacers to fly a one grain motor,   and put an adjustable weight system in the nose.   I haven't run any sims on it, but a 3 grain 54 will likely get you into an altitude you'll need to consider dual deployment and tracking.    This winds up being a complex build.  That's not a bad thing, but you may be happier building it after getting experience with a simpler rocket. 
« Last Edit: August 01, 2016, 11:34:16 AM by dbmccann »

Offline grub00

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Re: L1 cert for a Madcow V2 4" kit....
« Reply #3 on: August 05, 2016, 07:22:21 AM »
So much great information here! Thanks for the replies.  I'm going to be looking at something smaller and less powerful to do my certs on, and maybe just finish up the V2 for display purposes right now. It appears that I've purchased the rocket equivalent of a Datsun 280Z :)... Small body, giant motor, easy to crash (lose)  I've got some research to do o dual deployment and how that all works.  I'm assuming that yall are saying the V2 can't do it because the short body doesn't allow much space for an electronics package?

Given that you can use 1 spacer in a casing, is it common practice to buy a 2-grain, 4-grain, and maybe a 6-grain casing (along with a spacer) to cover all the motor configs?

Offline RKeller

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Re: L1 cert for a Madcow V2 4" kit....
« Reply #4 on: August 05, 2016, 08:13:41 AM »
The V2 is an awesome kit but it is a good idea to look for a rocket better suited to your immediate needs. you can use two spacers in a motor.
Riley Keller
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L1 25 Oct 2014 Estes MDRM CTI H133
L2 25 June 2015 Rocketry Warehouse DYOK, CTI L1030RL 14.7k ft mach 1.57

I'm addicted to building stuff, rockets are just a way to get high

Offline grub00

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Re: L1 cert for a Madcow V2 4" kit....
« Reply #5 on: August 05, 2016, 08:25:43 AM »
...you can use two spacers in a motor.

Ah, yep I see that I misread that. Thanks!

Offline dbmccann

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Re: L1 cert for a Madcow V2 4" kit....
« Reply #6 on: August 05, 2016, 10:26:11 AM »
V2s can go DD, just need to use the nose cone as a payload for it.

Offline RKeller

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Re: L1 cert for a Madcow V2 4" kit....
« Reply #7 on: August 05, 2016, 10:46:20 AM »
V2s can go DD, just need to use the nose cone as a payload for it.
absolutely! If I built one I would build it just like I did my Lil Rascal, that has worked great... http://urrg.us/smf/index.php?topic=25.0
Riley Keller
URRG
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L1 25 Oct 2014 Estes MDRM CTI H133
L2 25 June 2015 Rocketry Warehouse DYOK, CTI L1030RL 14.7k ft mach 1.57

I'm addicted to building stuff, rockets are just a way to get high

Offline grub00

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Re: L1 cert for a Madcow V2 4" kit....
« Reply #8 on: August 05, 2016, 10:53:55 AM »
V2s can go DD, just need to use the nose cone as a payload for it.

Was thinking that as well, the Nose cone on this thing is huge. The problem there is that I already glued the body pieces together and I'm assuming that you'd need the rocket to break into 3 pieces of DD?  Is there an alternative config for Dual deployment that I'm not familiar with that would do it in 2? Thanks for the tip though.

Offline dbmccann

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Re: L1 cert for a Madcow V2 4" kit....
« Reply #9 on: August 05, 2016, 11:50:54 AM »
If you haven't glued the coupler into the nose yet, you're ok.  Riley's lil rascal thread should show what you can do.   The NC coupler becomes the av bay, and you blow the nose cone off it to release the Main. 

Offline grub00

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Re: L1 cert for a Madcow V2 4" kit....
« Reply #10 on: August 05, 2016, 12:16:29 PM »
I glued ALL THE THINGS.... I'll know better next time.

Offline RKeller

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Re: L1 cert for a Madcow V2 4" kit....
« Reply #11 on: August 05, 2016, 12:44:35 PM »
I glued ALL THE THINGS.... I'll know better next time.

LOL, there is still a good option... https://www.jollylogic.com/products/chuterelease/ we have a few members using this with good results.
Riley Keller
URRG
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L1 25 Oct 2014 Estes MDRM CTI H133
L2 25 June 2015 Rocketry Warehouse DYOK, CTI L1030RL 14.7k ft mach 1.57

I'm addicted to building stuff, rockets are just a way to get high

Offline grub00

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Re: L1 cert for a Madcow V2 4" kit....
« Reply #12 on: August 05, 2016, 02:31:26 PM »
That does look nifty...I purchased their Altimeter II for the V2 a few weeks back since I wasn't intending on putting an electroincs bay in.  So, conceivably, the motor charge deploys the drogue chute and nose cone with this doo-dad attached to a rolled-up main chute?  When it senses the right altitude it releases the main chute?  Sounds like there might be some 'art' to rolling the chute so that it doesn't flutter itself open on the initial descent?

Offline RickB

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Re: L1 cert for a Madcow V2 4" kit....
« Reply #13 on: August 08, 2016, 10:42:37 AM »
There is a bit of a trick to wrapping the chute for successful unfurling, but it just takes some practice and experimentation.  The Chute Release can be set to open anywhere from 100' (not recommended) to 1000', so you can give the chute more time to open.  Most are using them in a drogueless situation, where it separates with motor deployment and just tumbles until the release altitude, but I have heard of some folks using them in combination with a drogue or streamer that come out with the motor charge.  I was thinking of putting a long mylar streamer on my Scorpion, more for viability reasons than not. 

There are those that will tell you that CR won't properly replace normal DD, for various reasons.  But if you wanted some redundancy using it, you can get two (though not cheap), and daisy-chain them together so that as long as one fires, the chute opens.  The plus side is that either can still be used on most any rocket you have, and having two units allows you to otherwise get two rockets prepped at a time.  A tradeoff of using a Chute Release between many rockets is that you can't really fully prep your next flight while waiting for the rocket on the pad to go up.  I'm considering getting another just for that reason, but it would also be nice to have aforementioned redundancy on a higher-flying rocket that's single-deploy.
Rick Barnes

Offline grub00

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Re: L1 cert for a Madcow V2 4" kit....
« Reply #14 on: August 08, 2016, 11:28:27 AM »
Lots of good ideas here....

I think what I'll do is try out the chute release on some cheaper, smaller rockets first to validate my packing technique.

Also, unrelated to the recovery, what about using a motor adapter to step down the power a bit? Is that allowed on cert flights?