First Ground Test EVER Was Successful!

So, I know this is a walk in the park for all of you and you do it more often than I can probably imagine.
I just finished my Formula 75 and she turned out great! For some reason I was worried about the motor recovery portion.
As you can see from my last post, I was asking about 3f vs 4f bp.
I used the 3f on hand (used 1.2g to simulate a 29mm motor ejection)
and stuck the rocket on it's work stand, hooked up my remote igniter and POOF!
Out of the rear end of my rocket, a big old orange fireball and the nosecone didn't come off all the way...
I forgot to plug the engine mount.
So, attempt number two about five minutes later, mount plugged, another charge setup and in the rocket.
Recovery test in 3... 2... 1... CRACK!!
Keep in mind I did this test about 15 minutes ago. So about 9:20PM Central Time.
For some reason, I was just so excited that I forgot somehow that bp goes boom when you pull the trigger (in this case, push the button)...
The wife wasn't thrilled and I'm sure the neighbors are wondering what on earth that was.
But now my pretty orange parachute protector has black marks on it... :lol: Kidding of course.
Nosecone and chute and all popped out and unwound nicely even only a couple feet off the ground.
Can't wait for my maiden flight with this baby and my Lv1 Cert on the 29th of this month!

So, technically your second ground test was successful. (Sorry, I can only be who I am. )

Hahaha!! Love it. Didn't think about that at all!!
I should rename the post... "First NIGHT of Ground Tests Was Successful!"

Congrats, though. I feel ya on late night charge testing...
[video=youtube;vE4gcRSdaII]https://www.youtube.com/watch?v=vE4gcRSdaII[/video]

Huh... Looked exactly like mine did! Must have done something right!
I'll try to record it sometime!

Sounds like you are all set for Level 1. Glad you remembered to plug the MMT. :wink:

No kidding. I ALMOST panicked.

On a slightly more serious note...

I just went to repack my chute and noticed a small hole melted into it.
Can I repair it or should I trash it and buy a new one?
Nothing melted together.
It somehow got around the chute protector. :-/
I'll use some barf from now on, no matter what...
Lesson learned. :-(

Do you have a pic? What kind of chute?

A sky angle c2, 28 inch diameter.

Imagine sticking a quarter vertically through a sheet of paper.
Same size and length. No pic right now. Sorry. Getting the kiddo in bed for the night.

If its rip stop nylon it should be OK. Look for lines running in both directions. It will look like a grid all over the chute. The lines will be about 1/4 inch apart.

Just like Zeus-cat says, if it is ripstop, you'll be fine. Sounds like it is a pretty narrow hole. If it really bothered you that much, you could stitch it up.

I'll keep it as is. Thanks guys!
If it gets worse I'll stitch her up.

I would cover it with rip stop tape, aligning the weaves in the same direction. Google ParaGear

Just as a point of reference, I've been using old umbrellas as chutes for years. They are NOT rip stop, but the many holes in them haven't made any noticeable difference in how well they work. The thing about burn holes in nylon, they melt the edges of the fabric together so that helps prevent any further tearing of the material. Also, unless you have a huge hole burned in the chute, the area of the holes is probably less area then a spill hole would be. You would need a lot of burn holes in a chute before you notice any difference in performance.

Thanks for the advice everyone!

Keep your old shirts / towels etc...throw them in there as protection or to simulate a chute and yes some dog barf, but then it's all over your yard.

Been there without the motor as well when I did my first test.

Reminds me of the time I did a ground test of a 24mm high L/D snap ring research motor with a graphite nozzle. I didn't have the forward snap ring seated with the motor buried into the ground nozzle up. Pushed the button, the case came up to pressure and the forward closure blew out. The case flew over 100 feet into the air straight up and straight down. The forward grain hardly had a burn mark on it. I later tested it somewhat successfully but the case pressure was way too high. The motor didn't
come apart but the aft snap ring was bowed out and trashed the groove. If the firing had gone on longer it would have failed. Kurt

How do you guys plug the MMT? When I did my ground tests (and i agree, it's exciting!) I used one of my kids' playdoh containers, small one, that fit in the opening for the forward closure of my 54mm CTI case. It worked well, but I'm sure there are better ideas. I've heard of people using spent motors, but I don't have any.

For what it's worth, I've stuffed an old sock with more old socks and tshirts, wrapped a nomex blanket around it, and twisted the whole "plug" into a motor tube before. It's not a perfect seal, but it will give you a good idea whether your charge size is sufficient or not.

AZRxocet said:

For what it's worth, I've stuffed an old sock with more old socks and tshirts, wrapped a nomex blanket around it, and twisted the whole "plug" into a motor tube before. It's not a perfect seal, but it will give you a good idea whether your charge size is sufficient or not.

Click to expand...

seems reasonable. A spent motor doesn't give you a perfect seal either, unless it's plugged or otherwise modified. I'm assuming the opening "touch hole" that bridges from delay element to ejection charge permits a slight release of pressure reward (assuming also that the forward closure is completely intact), but that amount of venting is negligible?

for my most recent ground test I stuffed an AT 38/720 case up the pipe and used a charge well cap to prevent venting through the case.
Rex

I knew those charge well caps would come in handy for something some day! Guess I'll let them clutter up my range box for a while longer! :wink: