Post mortem - Madcow Sea wolf

[dr wogz]

Hey,

So, I flew my Madcow sea wolf, 2nd flight, on an AT I366R. Boost was strong & straight.. til about 400', when the nose & laundry all popped out & shredded. On decent, we heard the ejection pop.

On post exam, it looks like I exceeded the strength of cardboard; the NC wanted to return the earth thru the top of the BT.. (NC weighs in at .87kg / 1.91lbs) Lesson learned: add a bit of glass to the top end of the BT!

The motor looked fine when I disassembled it, so no blow-by.

Does that sound right?



Rebuilding it is fairly easy; cut it down (fin can / fins are still solid), add a coupler tube & new section of tube. Fill, glass, finish! Worst part, is that I lost my JL chute release.. major bummed about that!

 

[Woody's Workshop]

Ahhh, one of the disadvantages of adding nose weight for stability for a larger engine.
If initial bang of thrust is enough, not even glassing cardboard tubes will help.
Need to move up to a glass tube.

 

[crossfire]

Did you have a vent hole in booster tube? Sounds like a early pressure deploy?

 

[smugglervt]

I didn't know you lost your JLCR. I would have help look for it. There were enough of us there for a grid search.

 

[dr wogz]

thanks all
No, no hole, didn't think I needed one for the small area inside.. but will add one for next time
Kit came with cardboard. maybe next time I'll go FG
Yeah, Kevin offered t help look for it, but I figure with the corn, the swamp & reeds (where I retrieved it from), and the fact it was black, would have been next to impossible to find.. Stronger / longer tether next time! I think the initial shock of what happened as well, didn't help..

Forgot my hat at the brewery too..

 

[SpaceManMat]

If it was chute deployment due to pressure build up then I would expect to see zipper a primary damage. If cardboard folded (bucking) with little sign of zipper then structural failure. Ordinarily NC exiting tube would be due to rotating, I would think tube would most likely fold over first. Can you post pictures would help.

 

[crossfire]

Who knows maybe you would get a zipper and maybe not. It just looks like a pressure pre ejection problem. As we all know in this hobby strange things just happen.

 

[dr wogz]

Obviously, Betty (the cat) isn't too impressed with me over this..

looks like a zipper with much of the upper tube (~4") missing, removed at the spiral. We deduced the 'punch out' was from the formed eye on the bottom of the NC as the NC folded over during ascent..

So, maybe the NC did start to come out of the tube, got to a certain point, and 'fell over' as the rest of the rocket was pushing forward, and therefore caused a stress on one portion of the tube rim, which lead to its demise..

it was interesting to watch..

 

[Exactimator]

Did the premature deploy happen at burnout or shortly after? If so, that would be drag separation. Seawolf's got a lot of drag. Was the nose cone fit snug?

I have a 4" cardboard Madcow Phoenix. The nose cone weighs 1 lb 12 oz. I've slammed that rocket up on VMAX motors multiple times and the tube's never blinked. If your thoughts are the weight of the NC caused the tube to buckle under thrust, I don't think that would make it pop out and deploy the laundry, although stranger things happen with rockets. More likely the weighted nose cone came off, slammed back into the top of the tube and crunched it.

I'd be surprised if you were able to build up enough pressure to pop the nose at 400 feet.

 

[dr wogz]

NC was snug, not tight. And the NC weight is still firmly anchored up top. I would think the "event" was just at motor / trust burn-out or slightly before..

Enough NC separation to allow it to topple over. that's my thought.

 

[rharshberger]

At what altitude do your sims show motor burn out? Even with a snug nose cone a heavy nose can still drag seperate deploying the laundry. The I366R is plenty hard enough hitting and abruptly shutting down that a large fin area rocket (higher drag on lightweight airframe section) and a heavy nose cone could easily separate. Its not a bad idea to vent all HPR airframes and wiyh heavy NC's use shear pins or some other method of nose cone retention when using hard hitting motors.

 

[mikec]

FWIW, I think drag separation is less common than most people think, unless the nose is extremely massy and loose and the rocket is very draggy (which admittedly may be the case here.) I'd be more inclined to blame an early ejection, which can be very hard to see even looking at the remains of the motor.

 

[wighty44]

FWIW, I've build this rocket and have flown it 3 times on CTI "I" motors (255 & 303), but did not see any evidence of BT stress or fatigue after the filghts. I do have a 3/16" vent hole inline , and below my fwd rail button (positioned near the rocket's CG).

Late entry: Overall weight is 2,591g of which 540g is nose weight.

 

[Zeus-cat]

It would be nice if the Jolly Logic stuff came in hot pink cases. I lost an Altimeter Two when my shock cord decided to break. Like the OP, I didn't even bother to look for a black plastic thing in a corn field.

 

[Glasspack]

Paul,

Sorry to hear about the Rocket is sure looks good whats left of it.. Love the Sea Wolf Kit.

I destroyed the upper section of my SA-14 Archer Booster section the day after I certified with it.
Got distracted several times during prep & I let it fly with no motor casing around the Cesseroni H143SS.



I hope you rebuild yours like I did my Archer....... !! I think this forum is awesome Thank you for posting that !!
We can all learn from each others experience ......

Paul

 

[ericm541]

I seen the flight my first thought was drag separation of course early deploy would do the same thing. A second after the motor burned out it came apart, zipper is from the chute opening while going up. Sorry you lost the chute release that sucks and the shredded chute.

 

[rcktnut]

Did the premature deploy happen at burnout or shortly after? If so, that would be drag separation. Seawolf's got a lot of drag. Was the nose cone fit snug?

I have a 4" cardboard Madcow Phoenix. The nose cone weighs 1 lb 12 oz. I've slammed that rocket up on VMAX motors multiple times and the tube's never blinked. If your thoughts are the weight of the NC caused the tube to buckle under thrust, I don't think that would make it pop out and deploy the laundry, although stranger things happen with rockets. More likely the weighted nose cone came off, slammed back into the top of the tube and crunched it.

I'd be surprised if you were able to build up enough pressure to pop the nose at 400 feet.

+1 Drag separation, not from pressure build up.

 

[Flyfalcons]

The Sea Wolf has a very heavy nose and a very draggy airframe. My money is on drag separation. It is a constant battle for me, working the tape on the nose cone shoulder to make sure it is tight (but not binding) before each flight.

 

[dr wogz]

I thank you all for your thoughts & comments. I too, am leaning towards drag separation. I have a number of 2-56 nylon screws, and will be adding at least one to the 'pre-flight check list'... once rebuilt..

 

[crossfire]

Not sure if you need shear pins? Just add some masking tape to the coupler to make it a little tighter.

 

[dr wogz]

NC separation, no upper AV bay. It's a short rocket! almost a stubby!! 1 can't hurt..

 

[ECayemberg]

Did the premature deploy happen at burnout or shortly after? If so, that would be drag separation. Seawolf's got a lot of drag. Was the nose cone fit snug?

I have a 4" cardboard Madcow Phoenix. The nose cone weighs 1 lb 12 oz. I've slammed that rocket up on VMAX motors multiple times and the tube's never blinked. If your thoughts are the weight of the NC caused the tube to buckle under thrust, I don't think that would make it pop out and deploy the laundry, although stranger things happen with rockets. More likely the weighted nose cone came off, slammed back into the top of the tube and crunched it.

I'd be surprised if you were able to build up enough pressure to pop the nose at 400 feet.

Listen to Exactimator. This is what happened to your rocket. Cardboard airframe is not the issue here.

I thank you all for your thoughts & comments. I too, am leaning towards drag separation. I have a number of 2-56 nylon screws, and will be adding at least one to the 'pre-flight check list'... once rebuilt..

Right on, brother! Sorry to see the damage; you'll get 'er next time!!!!

 

[dr wogz]

hey, it's how we learn right?!

While it may be a loss, I gained some valuable lessons! Now I know! (and knowing is half the battle! Yo Joe!!)

 

[smugglervt]

thanks all
No, no hole, didn't think I needed one for the small area inside.. but will add one for next time
Kit came with cardboard. maybe next time I'll go FG
Yeah, Kevin offered t help look for it, but I figure with the corn, the swamp & reeds (where I retrieved it from), and the fact it was black, would have been next to impossible to find.. Stronger / longer tether next time! I think the initial shock of what happened as well, didn't help..



Forgot my hat at the brewery too..

Paul,

I can stop by the brewery when they are open again and see if they still have your hat.

 

[AfterBurners]

thanks all
No, no hole, didn't think I needed one for the small area inside.. but will add one for next time
Kit came with cardboard. maybe next time I'll go FG
Yeah, Kevin offered t help look for it, but I figure with the corn, the swamp & reeds (where I retrieved it from), and the fact it was black, would have been next to impossible to find.. Stronger / longer tether next time! I think the initial shock of what happened as well, didn't help..

Forgot my hat at the brewery too..

just my :2: but maybe add a neon streamer to the JL I have one and that's what I plan on doing just in case it happens to me.

 

[dr wogz]

Jim, if it's an easy trek, please do. (tried calling yesterday..)

Afterburner, yes, I plan to: paint it orange, add a longer & stronger tether, and add a 12" streamer to my next one..

 

[Daddyisabar]

I think adding the vent hole is in the directions. I would guess several factors contributed to drag separation; a heavy nose cone, a heavy draggy body, a punchy motor, a little built up pressure, nose cone just a bit too loose. That Sea Wolf is a heavy little porker and the bits do tend to build up a lot of inertia so if deployment in not exactly at apogee it is easy to get a zipper on the cardboard.

Yes, my first big 38mm rocket had to be the Mad Cow Sea Wolf; paper and wood glue, needs all the power she can get, a great sale price, who could resist! Still got a small zipper so it was time for this green horn to go back to the school of hard knocks for some anti zippering treatment. To heck with paper, wood glue and weighty sport scale rockets. Bulletproof fiberglass, long sleek 4FNC beauties are just oozing awesomeness.

 

[CPUTommy]

Two strands of this stuff and you will be very VERY hard pressed to lose anything its attached to. My rocket landed 3/4 of a mile away and the whole time I was walking towards where it landed the wind and sun twinkled it. I never launch with out a few strands. At altitude its very evident where your rocket it is, more so on very sunny days.