On the first attempt, Art and Mike had their heads to the avbay, John rested the rail on his shouder. I was taking the pictures; had I been any good at it, I would've gotten the charges going off. THEN BAM-BAM! What happened to Mike has always been one of my fears. Mike, you're one of the most persistant rocket guys I know! It's definitely an altimeter problem, which you'll work out with the manufacturer privately. I have a vested interest in that, as I had planned to use one on a rocket similar to yours. Great pictures; now we all know what concrete does to PR G10, in close up. You're lucky the nosecone shot off with no damage. Concrete and FG nosecones don't work well with each other either. As we all agreed yesterday, you'll have no trouble pushing your chutes out! Yesterday wasn't what we'd hoped, but a good lesson for all of us.

Mike
Hind site is 20-20 If only you knew the alt. was bad(hard to tell out there), I had the same one (tested too) sitting in the back of the van you could of barrowed! Might of made the differance.
Oh Well, a shame. Thats why I wanted that vacume chamber. Not everything coming off the assembly line is perfect. Good luck next time.

Scotte

Scott,

Actually most of the long time manufactures put their product through vigorous pretesting. Yes I know which manufacture this one was and I can say that each individual unit is vacuum calibrated and tested before it is approved. Yes things are still possible but pretty rare.. Again most ALL failures Ive had and seen were out of a user related issue. Trust me ive made my mistakes doing them as well.. One thing of most importance is that no one was hurt during any of this. Thats a lucky thing. We all should be fortunate and think about the safety aspects first.

I think at this moment the discussion of the unit in question or the manufacture is not relevant and needs to be put on hold till more info from the manufacture is given on what happened.

Mike Sorry to see things didnt work out as planned. Again get with the manufacture and give it a go again....

The avbay is still intact, although cleaned up and the primary charges removed, and until I can make contact with the manufacturer I don't want to speculate. I want to help trace down the root cause of this problem with them, and as a product development engineer, I do not want to make across the board comments about another engineer's product. For some reason, I have this uncanny knack in finding problems that others have not not experienced, so this is not new to me. We'll all learn from this once we have more facts. I'm certain I did everything by the book, so I am sure the designer will want to be involved. If I screwed up in some way, then that's another lesson learned.

However, when I got home, in a post flight fit of curiosity and fact finding, I did attach some 12V LEDs lights (manufacturer approved) to the external charge terminal blocks and stuck the avbay on my patio in the wind to see if I could set them off. Since the igniting signal is so short (about one second) I couldn't see an event in the late day light. I have exactly the same setup in another rocket, that I did not have time to launch on Saturday, so I may be doing some tests on it (without the big charges, just the e-matches).

I have the avbay out on the deck tonight getting frozen, with e-matches connected (no BP) and I'm going to turn it on around midnight. The temperature (30 deg F) will then be the same as it was on Saturday, midday. In the warm garage it beeped a normal ready mode for 15 minutes without firing off. I'm looking to consistantly repeat the failure so I will know what NOT to do in the future.

On the first attempt, Art and Mike had their heads to the avbay, John rested the rail on his shouder. I was taking the pictures; had I been any good at it, I would've gotten the charges going off. THEN BAM-BAM! What happened to Mike has always been one of my fears. Mike, you're one of the most persistant rocket guys I know! It's definitely an altimeter problem, which you'll work out with the manufacturer privately. I have a vested interest in that, as I had planned to use one on a rocket similar to yours. Great pictures; now we all know what concrete does to PR G10, in close up. You're lucky the nosecone shot off with no damage. Concrete and FG nosecones don't work well with each other either. As we all agreed yesterday, you'll have no trouble pushing your chutes out! Yesterday wasn't what we'd hoped, but a good lesson for all of us.

Mike
Hind site is 20-20 If only you knew the alt. was bad(hard to tell out there), I had the same one (tested too) sitting in the back of the van you could of barrowed! Might of made the differance.
Oh Well, a shame. Thats why I wanted that vacume chamber. Not everything coming off the assembly line is perfect. Good luck next time.

Scotte

Scott,

Actually most of the long time manufactures put their product through vigorous pretesting. Yes I know which manufacture this one was and I can say that each individual unit is vacuum calibrated and tested before it is approved. Yes things are still possible but pretty rare.. Again most ALL failures Ive had and seen were out of a user related issue. Trust me ive made my mistakes doing them as well.. One thing of most importance is that no one was hurt during any of this. Thats a lucky thing. We all should be fortunate and think about the safety aspects first.

I think at this moment the discussion of the unit in question or the manufacture is not relevant and needs to be put on hold till more info from the manufacture is given on what happened.

Mike Sorry to see things didnt work out as planned. Again get with the manufacture and give it a go again....

Yes it could of been something Mike did. But I dont think manufacturers are perfect either. As a bussiness man myself, I know every Roof we ever put on, isnt perfect. Yes, I have had to fix some leaks.
Mike was saying testing it at home wasnt producing the same result .
I may be streching but, it was fairly windy. If the pressure bleed hole in the av. bay, was facing the wrong way, it only takes 1/4" change in pressure to arm the thing. ??? Will be interesting to know the answer.

That's an interesting thought Scott. My very first dual deploy bird had only a single altitude bleed hole into the avbay and it fired its charge on the pad when a gust of wind hit. Since then I've generally gone to 2 or 3 holes equally spaced around the avbay and have never had that kind of problem again. However, it was a specific altimeter that was known to have this problem - not a Missileworks.

Warren

Cant say ive ever had that issue with wind setting off any of my atlimeters. But I also use the better method of using 3 to 4 equal and properly calculated static ports as they filter out noise from wind and other varibles and they also provide for more accurate readings and better deployment. Just an all around better way to do it.

FYI, I have 6 each 5mm diameter static bleed ports evenly surrounded around the avbay.

ROOT CAUSE OF PREMATURE DEPLOYMENT IS NOW KNOWN

No need to continue to speculate. I will provide more data after a few more tests tonight, and how to prevent it.

Good deal - can't say I've ever seen that many, but that'll certainly do the job.

FYI, I have 6 each 5mm diameter static bleed ports evenly surrounded around the avbay.

ROOT CAUSE OF PREMATURE DEPLOYMENT IS NOW KNOWN

No need to continue to speculate. I will provide more data after a few more tests tonight, and how to prevent it.

Mike,

6 x 5mm? What is your avionics bay specs? Length and Diameter?

That's an interesting thought Scott. My very first dual deploy bird had only a single altitude bleed hole into the avbay and it fired its charge on the pad when a gust of wind hit. Since then I've generally gone to 2 or 3 holes equally spaced around the avbay and have never had that kind of problem again. However, it was a specific altimeter that was known to have this problem - not a Missileworks.

Warren

More than one hole? That wasnt in the directions for any of my rockets!8O

Oh yeah, it's also just as important that you dont have TOO much port area. Too much or too little can confuse the altimeter.

Warren

Forget all this rocket stuff... there's one really important point... why do I look like Kenny in South Park in Mike's picture? 😯

I use three, on this next rocket, they'll be calculated using MWC's formula.
It gives me (3) 3/16" to 13/64" for a 219.7 cubic inch volume.

Forget all this rocket stuff... there's one really important point... why do I look like Kenny in South Park in Mike's picture?

Awesome!

I've used one static port on probably 95% of my rockets. I did use 3 on my L3, but I think that is the only time I did so. That was a very large ebay, and the requisite hole was bigger than I felt comfortable with.

Jim Amos once told me that it is "OK to have any number of ports, as long as it is NOT 2 ports". IIRC he was concerned about winds moving through under certain circumstances. He was OK with 1, 3, 4, etc. I also believe this info was in his older manuals? I have them downloaded on my other computer, I can dig that up sometime if necessary.

Everything I have read indicates that too much area is bad, especially on high speed or high acceleration flights. I just had a conversation on this last week w/ Peter Lawall (PerfectFlite).

JW

Mike,

6 x 5mm? What is your avionics bay specs? Length and Diameter?

5" diameter by 12" Long. Here' s the MW Guidlines with my calculations in red (FYI, all this is on my web site):

So you have .588 in^2 as your area that you need in holes. So now you wanted 6 holes around the airframe. This would be .588 in^2 /6 or .098 in^2 for each hole. A = pi*r^2 so r = SQRT(a/pi). Therefore we get r= SQRT(.098/pi) r = .1766 in. That is the radius, so for diameter that is twice so that mean each hole would have to be .353 in. Interesting that the two formulas get two different answers.

Edward