MadCow 4" Patriot weight...

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Forever_Metal

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Hey all!

I know this topic has probably been beat to death and has been pulled up and then re-buried over and over again. I'm hoping to get some info from current or recent builders...

According to openrocket and a lot of math to back up OR's findings, in order to get 1+ cal for CP/CG with a Aero J460, I need to add 1100g+ of weight to the nose when using the removable avx bay, and can only get to .833cal if I want to use a J800t. I (originally) wanted to eventually fly this on a K (I know, right?), but can only get to .743cal with that weight (at 1200g cal is still only .874). I've attached the OR file and the particulars below; ANY help advice or confirmation will be appreciated!

Kit config (no AVX)
4" dia, 53mm mount, dry weight before adding to the n/c is 1483g

Kit config (avx bay)
4" dia, 53mm mount, dry weight before adding to the n/c is 1848g

Thanks in advance!!

fm

View attachment MadCow Patriot 4.0 (w_AVX).ork
 

jjhdnd

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The "stock" MC patriot needs some forward weight. I followed my club's advice and put a water bottle in the payload section for my L1 cert flight. Drank the water after the successful flight to celebrate. (I suppose I could have planned ahead and used some other ... beverage.) After that, I made a new forward section for dual deploy. That adds enough weight and is a good idea if you are using J motors and want to get it back. Add GPS if you want to get it back from a K. :)

Have fun! My MC patriot has been great workhorse!
 

Forever_Metal

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The "stock" MC patriot needs some forward weight. I followed my club's advice and put a water bottle in the payload section for my L1 cert flight. Drank the water after the successful flight to celebrate. (I suppose I could have planned ahead and used some other ... beverage.) After that, I made a new forward section for dual deploy. That adds enough weight and is a good idea if you are using J motors and want to get it back. Add GPS if you want to get it back from a K. :)

Have fun! My MC patriot has been great workhorse!
Was there enough weight from the avx bay and recovery hardware that you didn't need any nose weight or was it a ... smaller bottle (.5L vs 1L) I prefer the other... :wink:

Did finally get some design changes in to help it along, to fly the K now only requires 1000g...

Thanks for the reply

fm
 
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Forever_Metal

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Want to thank Tonimus for the info! Will hopefully be putting this bird up during NSL!!!

thanks all!

fm
 

Tonimus

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Just now seeing this thread, but I did reply to the OP's PM already. As I told him, trust the sim for nose weight. As others have dealt with before me, the scale fins need a TON of nose weight to fly straight. I check the sim against reality when the rocket is fully loaded with the motor in question to make sure I have at least 1 caliber of stability. Hasn't done me wrong yet.
 

Forever_Metal

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But 1st, the Thanks!

To rharhsberger for referring (getting me off my rear)
To Tonimus:headbang: you provided the direction you steely-eyed missileman!!
To the Huntsville Area Rocketry Association; who allowed me a few hours away from the MPR/HPR LCO
table during NSL 2016 to talk to current builders/fliers about this!!
And to the fliers who spoke to me, thanks for your time (yeah that means you Jr Lvl 1, GOOD JOB)!!!

And now, to the slide show...

Fully assembled
(will include spring washers for flight)
IMG_0157.JPG

I used JB, and placed a 3M plastic epoxy plug in the tip
(will butt the end of the 5/16 threaded bolt against it,
so ejection charge will not push completely against mount only)
IMG_0158.JPG

Another offset picture of the plug
IMG_0159.JPG

This is the carrier top
IMG_0160.JPG

This is the bottom side of the carrier.
There will be a 5/16x7" all thread bolt
holding the 1.25" lead rounds (with jam nuts)
IMG_0161.JPG

All-told I will be able to vary the weight from 375g
(minimum for J350 to ~4000') to ~1000g (yes, I'm gonna say it, a K!)

Hope you all use this idea, if you make changes or have better ideas,
please, please let me know!!!


Thanks for looking all!

fm
 

Tonimus

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Awesome. I'm glad I could point you in a direction that worked for you. Now learn from me and do not attach the 'chute too close to the nose cone or it may not unfurl.
 

Rex R

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as I recall, I believe that I needed 450g of nose weight in my otherwise stock patriot to balance an AT 2-grain 38mm motor, I have been known to put a pound of cheese in the payload bay for an I211.
Rex
 

Flyfalcons

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I saw a Youtube video of a 4" Patriot and it was mentioned that 23 oz of nose weight was used.
 

Forever_Metal

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as I recall, I believe that I needed 450g of nose weight in my otherwise stock patriot to balance an AT 2-grain 38mm motor, I have been known to put a pound of cheese in the payload bay for an I211.
Rex
Rex,

You remember what kind of speed off the rail you were hitting?

fm
 

Rex R

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according to OR; H242-8 44f/sec(no additional weight), I211-10(with cheese) 46.5 f/sec. if I were to build it today it would probably turn out somewhat lighter...it was my 1st Hpr (and cert rocket), it turned out rather solidly built. OTOH it isn't bothered much by wind :).
Rex
*edit*
weight w/o motors is 2.02Kg
 
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Forever_Metal

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Hey ALL,

Thanks for the advice! As you can see by the picture, I got a bundle that works.

IMG_0196.JPG
It even passed it's ejection tests with a fairly nice report!

I was asked to provide a parts list and where to get soooo here ya go!

1) 4" Ply Centering ring (Madcow) with 4ea backnuts/bolts (HomeDepot)
please see earlier photo for placement!
2) 4" Ply Bulkhead plate (MC)
3) 5/16"x4" eyelet with coarse thread + nuts/washers (HD)
4) 1.5" coupler for above (HD)
5) 5/16"x4" coarse thread Grade8 bolt (HD)
6) 4oz. Disc Sinkers with 5/16" hole drilled (Cabellas)

I'm actually going to use this if needed on all of my birds now. Also allows me to change the weight depending on the motor I want to fly! Don't forget that you can change the thickness of the hardware to suit your needs. I used these sizes due to the weight involved!

Thanks again!

:headbang: fm :headbang:
 

Tonimus

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Nice. I went with scrap I had laying around for weight. In my nosecone it's washers. In my buddy's SuperDX3 it's timing gears.
 

Tonimus

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I'm lucky I haven't grenaded a motor that bad yet:smile:
Wasn't grenaded. A SBC my buddy bought had timing gears instead of a chain, and to some (me included) they sound ridiculous. We swapped it out for a chain and kept the gears for whatever. Now they move faster than they ever did before.
 

Forever_Metal

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Gear drives keep my 360 purring along at 7200rpm all day, fortunately the engine is too loud to hear anything else...
 
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