Eric,
So to clarify you are removing BP and putting blue tape over the cavity?
Sent from my iPhone
On Sep 5, 2017, at 8:36 PM, Eric Melville <eric@xxxxxxxxxxxxx> wrote:
I put blue tape over the touch hole. It might sound ridiculous but I have not
seen a single burn through, on at least a dozen flights now.
- iPhone mail
On Sep 5, 2017, at 7:40 PM, Dave M (Redacted sender "muldavea" for DMARC)
<dmarc-noreply@xxxxxxxxxxxxx> wrote:
So what should I do otherwise with the BP cavity? Is there a better way than
filling with epoxy?
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On Sep 5, 2017, at 6:47 PM, Dave M (Redacted sender "muldavea" for DMARC)
<dmarc-noreply@xxxxxxxxxxxxx> wrote:
I just emptied the cavity of the BP.
Sent from my iPhone
On Sep 5, 2017, at 6:12 PM, Dave Barr <dhbarr@xxxxxxxxx> wrote:
To clarify: did you keep the delay grain or was that epoxified as well?
On Tuesday, September 5, 2017, Dave M <dmarc-noreply@xxxxxxxxxxxxx> wrote:
54mm. I believe they were a J295 and a K570.
Good point Kurt. Maybe I was just unlucky with those two launches. At
first I thought I was cutting off the oxygen supply somehow at the base
of the motor (I helped a guy who was down to his last igniter when I
noticed he had heavily taped up the bottom of the motor) but I just had
the red cap on and even cut an X cut into it after igniters failed. It
was only later that I realized it was the motors I filled with epoxy so
I got suspicious. Now I'm paranoid to do that again. On some small
Aerotch motors I've just used Vaseline instead of BP with some tape over
it, but figured epoxy is a better alternative?
Sent from my iPhone
On Sep 5, 2017, at 4:54 PM, Kurtgug@xxxxxxxxx <kurtgug@xxxxxxxxx> wrote:
Once you burn the first igniter without lighting the motor, it is always
harder to light it with the second, and even harder with the third. The
core gets coated with soot which acts as an insulator. If you had the
pyrodex pellet in there, it is hard to imagine that not lighting. Maybe
it did light but fail to light the fuel. That would really coat the
inside with soot.
Sent from my iPad
On Sep 5, 2017, at 4:44 PM, Dave M (Redacted sender "muldavea" for
DMARC) <dmarc-noreply@xxxxxxxxxxxxx> wrote:
No I was very careful next not to disturb anything. And the epoxy dries
so quickly that I didn't think it would have any chance to soak thru
anywhere.
Sent from my iPhone
On Sep 5, 2017, at 4:36 PM, Gregory Lyzenga <lyzenga@xxxxxxxxx> wrote:
On Sep 5, 2017, at 4:22 PM, Dave M (Redacted sender "muldavea" for
DMARC) <dmarc-noreply@xxxxxxxxxxxxx> wrote:
A while back, I had two Cesaroni motors that were not plugged but I
didnt want the motor to blow the BP charge. So I removed the BP and
filled up with epoxy. Problem was, in each case, it took maybe three
attempts to launch. Kept burning out igniters. Any thoughts?
In the process of removing the ejection charge, did you disturb or
damage the igniter pellet at the top of the grain? Since Cesaroni
igniters are basically just e-matches without a bunch of pyrogen, there
is a pyrodex pellet at the top of the motor to get the ignition going.
If the epoxy ran onto that, it might explain your problem. But on
second thought that seems unlikely, since there would be a delay grain
between it and the ejection charge well. Hmmm… I’m not sure...
- Greg
----------------------------------------------------------
Gregory A. Lyzenga <lyzenga@xxxxxxx>
Dept. of Physics, Harvey Mudd College (909) 621-8378
Claremont, CA 91711-5990 mobile (626) 808-5314
