Hearne, Texas

    Went out to Hearne, Texas this weekend for a Tripoli high powered launch.  My monkey's rocketry group was having a tournament.  We watched a lot of small rockets use mid-power motors to reach 3500 feet, which was pretty exciting.  It was very windy, so most of the rockets were never seem again.  This also marked the weekend of trying to get my level 1 high powered certification.
    The menacing Zombie took the launch pad armed with a H400 Vmax engine and kicked off the pad with no problems.  The rocket easily went 3000 feet and the ejection charge fired of the nosecone no problem.  The descent velocity was way too high and as it came closer, we realized the parachute was tangled.  The Zombie tumbled down into the ground, but none of the components broke!!  The fin fillets, the epoxy keeping the fins in the body tube, came off sadly.  This meant that the zombie was not "flyable" on recovery, so I couldn't receive my L1 certification.
    The range safety officer, RSO, was very kind and allowed to to go re-epoxy my fins on.  After the fins had set, I threw the Cesaroni H125 Classic in the Zombie and it took the pad again.  This time, I had used a different parachute packing technique, showed to me by a very kind group of fellow rocketeers I had met there.  Instead of wrapping the parachute in the shroud lines, as is commonly done with model rockets, you fold the shroud lines into the canopy and roll it up.  This may seem like a subtle difference, but it keeps the shroud lines from becoming tangled.
   All was set for try number two, and the RSO counted down and hit the launch button.  This engine was very different than the Vmax (as described in a previous post), but the rocket still flew straight.  Until the phenomena of fin flutter kicked in.  As a rockets speed increases, the amount of turbulent force on the fins increases drastically.  At a certain point in it's trajectory, the flutter forces overcame the new epoxy fillets and all the fins flew out of the body tube.  The rocket immediately lost its speed and started tumbling down to the ground.  This was concerning, because the rocket had a specific delay charge that anticipated reaching simulated apogee.
    The rocket tumbled down to about 15 feet above the ground before the ejection charge went off and the parachute slowed the rocket.  If it had happened one or two seconds later, the Zombie may never have flown again.  Luckily, all three of the fins were recovered and the body tube was unscathed.  For the next launch, I plan on using a much stronger resin with flecked cotton to increase its strength.  I will also use a composite material on the joints to make sure that the fins are now permanently attached.
    The Zombie will rise again and I will be sure to pack the parachute right and use it to get my level 1 and level 2 certifications.

Here's a video of the rocket taking off the pad.  I wasn't prepared for just how fast this take-off was going to be!

-Aerolite