[christmas cheer]

That is a direct lie. That is a falsification.

It is NOT true and if any moron took it that way I apologize for your being a moron and taking it that way. I have certainly made TIMELY clarification posts when some MOPRON took it that way.

It is a lie.

I also made clarification posts when the MORON was detected by myself and others and stated they would intend to escalate this into a Kosdon - Irvine war. I am not at war. I do not intend to go to war. I hope Frank feels the same despite what his MORON of a business partner might say or do.

MORON is a LIAR.

Jerry

Did he warranty the rocket as I did the motor? FULL replacement if it FAILED the stated mission?

Jerry

Jerry, the fin-panels were off-the-shelf G-10. Nothing I got from Dave had any relation to the shred - any "finger pointing" on that should be directed at me, not him. It was a true "velocity flutter" event, caused by an airspeed too high for the fin construction, and the point of failure was completely in the G-10 panel itself, not in any glued assembly.

Besides, the rocket was neither destroyed, nor did it fail its stated mission - which, for that flight, was to give us an idea of what would happen to the fins on the H2O2 bird if we tried to push it _that_ fast. :)

-dave w

Was it glued to accept that grade of fiberglass?

Was the manufacturer notified of the expected average thrust you planned to use for a short duration on a solid and a much longer duration on a liquid, AS I WAS?

If so, the fin panel should have been considerably thicker IMHO and any either analysis or experience would have revealed that.

Jerry

I do believe the stated full load H2O2 mission was that thrust for more than twice as long. Would you like me to post a performance run to show it would have gone about 1.5 times as fast?

You saw the fin panel attachment on that bird - the panels bolt in: root tabs are sandwiched between 1/8" ply mounting strips mounted edgewise on the MMT (and reinforced with 4 layers x 4 oz. glass cloth, tip-tip in each "fin bay" - each fin is clamped by 4 6mm bolts. No glue required.

That all held together just fine - the G-10 parted outboard of where it was clamped in the root assembly.

I still have the root tab remnants. (I might give you one for a souvenir...) All show a similar fracture pattern.

It looks like each panel started to fracture from the trailing edge forward: the aft edge of the break is almost perpendicular, straight through the thickness, while nearer the leading edge the material is more folded and peeled.

A probable key design factor was something that seemed like a good idea at the time, as a tidy treatment for a fin slot extending to the rear of a removable airframe tube, but probably added a structural weakness: the aft end of the root tab is located forward of the trailing edge of the panel itself: this involves a notch in the aft/root corner of the panel, which seems to have provided a point of stress concentration where the material first started to crack, once vibration-stress built up to a certain point. The crack then "grew" forward, further weakening the panel, until it finally flopped over and was torn away.

Note the appearance of the remnants, post-flight (and the otherwise-intact condition of the rocket - I even got you your casing back, undamaged, despite everything...):

(Don't worry, I haven't forgotten our challenge... life, peroxide, and everything have somewhat slowed down my actual HPR-type activities of late, but I don't intend that to be a permanent condition!)

-dave w

Yes and that is NOT what failed. The fin was too thin or too flexible.

Switch to steel and double the power.

Jerry

Precisely.

-dave w

Hmmm...

I thought you could never be too thin or too flexible...

David Erbas-White

I wonder if there is any evidence on the fracture surface that shows the cyclic loading, if indeed fatigue was the mechanism of failure. One could do a failure analysis using an SEM to search for beach marks or chevrons, provide the fins have any witness features. If so, one could count them and back into a cyclic load frequency.

Just a thought

-- Drake "Doc" Damerau

YOU (or your girlfriend) cannot. Your rocket CAN.

Send him the wreckage! He has TEST EQUIPMENT!