Stability on my Estes V2 modified

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LaneKG

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Folks,

I have modified the maxi V2 as follows

Loc 29 mm motor tube
Loc centering rings including one inside small end of nosecone
styrene sheets sandwiched between the fin halves per Sandman
nose wight added 4 oz (I think) or was it 8 oz
retention hardware
pratt heat shield
36 in chute.

Now was all that a good idea. I am not sure. I like to say I have created a monster as it weighs 1.9 lbs

With the current nose wieght the CG is 18 in from the tip of the nose

I put in a mass overide and a CG on styme's rocksim file.

The loaded for launch weight CG is 19.8 in and Barrowman CP is 18.45 (Unstable) and Rocksim is 23.78 (marginably stable)

Am I ok here or add some more nose weight?
 

jetra2

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I remember reading somewhere about how the V-2 was designed to carry a 1000 pound warhead in its nose, but without it, as was learned, the rocket is not stable. Therefore, I recommend adding more noseweight, just in case. A rocket that is unstable under G power is SCARY...I recommend that you verge on overstability, or try to get the stability to ~1.5 calipers.

Jason
 

gerbs4me

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I agree with jetra

be sure to get launch pics, gotta see:D
 

cls

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let's go by the numbers ...

according to rocksim and the precise info I put in for my Estes V2 (hah), the CP is somewhere near 52 cm from the nose. that's just forward of the top of the tail cone.

for minimum stability the rocket's CG should be at least 1 diameter (BT-101 = 101 mm) forward of the CP. so you definitely need to put a bunch of weight up there, until you can balance the rocket 42 cm from the tip of the nose cone.

consider doing the swing test on it before launching.


good luck with your beast! and don't forget to post pix.
 

LaneKG

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Folks,

I am 3.9 in margin with Rocksim CP and Unstable with Barrowman CP I plan to use a G64-7. I think I will add a bit more weight. However the more weight I add the slower off the rod.

Greg
 

Stymye

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you will need a long 1/4 rod, a rail would be even better
 

LaneKG

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stymye,

I am set for 6ft 1/4 rod. As for the rail can I install a button where I cannot get to the back side.

Greg
 

stevem

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thought I'd chime in here on the rail button - you sure can mount them where you cannot get to backside. a 1/8" hole and some epoxy is all you need.

after using a rail I'd never go back to rods and lugs.

one question - is 'slow off the rod' a bad thing? I love how slow my V2 lifts off, seems more realistic.
 

cls

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stevem: is "slow off the pad" necessarily bad? not really by itself. as long as the rocket is moving fast enough that the fins are "flying" and will keep it going straight up. a marginally stable rocket, slow off the pad, in a cross wind, now that's asking for trouble.

lanekg: now you see the downward spiral that happens when you up-size motors. add a bigger motor, sure, but you waste much of the gain because of counter weight. add more counter weight, need a bigger engine ... etc. etc.

anyways your G64 is gonna rock!!
 
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