My Scrach Build MPR Project

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Jan 20, 2009
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I present to you my latest project. It stands at 62 inches tall (picture is standing next to my Loc Onyx that is awaiting its paint job after my first botched attempt), weighs in at 48 ounces at the moment, and is awaiting a few touch up details with Fill n Finish and a paint job. On paper it was designed for the Aerotech G77R motor, and I am pleased with the result. I have scratch built many LPR rockets, but this is my first time scratch building MPR. The recovery system includes a steel wool filtered baffle and 10 feet of kevlar shock cord. It will be recovered on a 36 inch parachute. My only regret is that I opted for a 29mm motor mount instead of adapting down from a 38 :bang:. The paint job will be mostly black with a few red highlight stripes and details, and it will be touched off with a few small decals I got from (fantastic service). If I am happy with this rocket on a G77, I may decide to try for my Level 1 on it. But one step at a time.

I have a quick question regarding nylon parachutes. I am hoping to dye the parachute to a brighter color, hopefully red, but I was wondering if anyone had any experience with Rit dye and whether or not it is suitable for this application. Any help is appreciated, as well as any comments and critiques. I have scratch built many LPR rockets, but this is my first time scratch building MPR. The recovery system includes a steel wool filtered baffle and 10 feet of kevlar shock cord.

Are you aware that steel wool can and will catch fire? :shock: If your useing the pot scrubber type mesh, you'll be fine.
Yes, very good point. I made sure to check that problem out. I'd heard one or two horror stories (just from a guy who knows a guy who knows a guy etc), but enough to make me double check the stuff I put in. I am using a very coarse grade with thick filaments and tested it with a lighter outside to make sure it wouldn't readily ignite.
The scrubber type of steel wool can and will burn, trust me..One bursting into flame on the way down causing a range fire contained by a farmer using a Caterpillar road grader(he plowed with the rippers around the fire). THe second when it landed I told the owner, "Your rocket is burning with a smoldering fire melting all the plastic." When they got the rocket and assessed the damage the baffle had indeed caught with a smoldering fire fed by the plastic. Just as destroyed as mine that caught fire.

What happens is the hot ejection charge hits cold steel and condenses on the steel, building up layers that after a while become excelent base for a fire to start, black powder coated steel.

A better baffle is one where the airflow has to change direction like a stack of disks separated by enough space that it doesn't plug up. Alternate disks with one larger hole in the center with one's with 6-8 smaller holes drilled around the circumference.
Make the top of the baffle removeable. Then you can clean the mesh or just replace it.
Should be easy enough to implement the disk baffle method. I had originally built a baffle like that, but can't remember why I decided not to go with that. Thanks for the suggestions everyone, I certainly wouldn't want this rocket to go up in flames. I'll post pictures once I get it painted. I should be able to use one of my school's race team's painting rooms to do the job right.
As the others have said, stay away from the steel wool. I've burned a lot of it years back.

In regards to Rit dye, it works fine.
to emulate what would happen with steel wool in your rocket, you would need air moving over it as you're lighting which case, you'll see that it takes fire, and throws considerable slag. as your rocked decends, i imagine it would have a ball of molten iron dripping away.
With all the warnings about the hazards of steel wool, I'm glad about posting the details of my design for review. I replaced the steel wool with a balsa wood baffle coated with epoxy to prevent heat degradation. Thanks for all the tips, I certainly appreciate hearing from those who are far more experienced.
Oh, and in case anyone was wondering what happened to my majorly ugly Loc Onyx that this rocket is pictured next to. Here's a quick update.