[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.

shows the fin attachment - note the way the fin panels are notched to fit around the aft centering ring and fill the slot in the airframe tubing.

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...):

The manufacturer of the rocket will develop upgraded hardware for future missions... a prototype of the successor construction method (glass cloth and Aeropoxy resin over shaped urethane foam, with a thin G-10 profile core) was tested, inadvertently, at Fresno last May, when a failure of a second-stage recovery event brought the thing all the way down on drogue only, to a landing with no damage except some dirt to wipe off one fin.

(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

NEPRA President NAR Section 614 NAR 79986 L3 Remove "My Shorts" to reply

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

Send him the wreckage! He has TEST EQUIPMENT!