Just an FYI I have found mixing the propellant, letting it sit overnight and
adding the curative the next day works also.
Jim Wold
-----Original Message-----
From: James Dougherty <jafrado@xxxxxxxxx>
To: ROC Chat <roc-chat@xxxxxxxxxxxxx>
Cc: Lee Buchok (Redacted sender hyflynboy for DMARC)
<dmarc-noreply@xxxxxxxxxxxxx>
Sent: Sat, Apr 25, 2020 3:50 pm
Subject: [roc-chat] Re: Vacuum Pump
That's sweet. Thanks Mike for sharing ...
On Sat, Apr 25, 2020 at 10:48 AM mnkramer.net <kramer@xxxxxxxxxxxx> wrote:
Ignoring the day job vacuum pumps, I have a Gast pump I use at home,
Let me weigh in on a few things,
Degassing, I use (again at home), a menudo pot (big aluminum pot, they cost
around 30-40$ plus need to add a plexiglass lid so you can see through and a
rubber gasket (needs to be thick). For this i want a high volume flow, so I
can draw down the pot. 25 inch Hg minimum. Plus if you want to get very good
degas resin add a degassing agent (small percentage siloxane, or BYK-501) makes
a very big difference. This is what we do at the day job. Bumping the mix,
draw vacuum, quickly release and then draw vacuum again before letting it sit
works well, for that you need a vacuum pump with some volume.Cheep vacuum gauge
works. You can buy degassinng kits from ebay pot with lid and pump.
Vacuum Bagging, you need t leave the vacuum on during the cure to get the best
properties. ust bagging a part (food sealer only gets you a little way, a pump
running during cure and a breather in the bag will get you full 14psi pressure
on the lamiante. Always use a resin trap, For home and the day job we use
gallon pickle jars, with a rubber cap. The hose TO the vacuum bag runs to near
the bottom of he jar the one FROM THE PUMP runs to the top of the jar. That
way if you suck resin in is doesnt get into the pump. You can reuse the jars
just let the resin cure in the bottom and leave it. Again 25in Hg minimum.
Cheep vacuum gauge works.
Fora pressure chamber you don't need nearly the depth of vacuum that you need
for degassing or vacuum bagging. The trick is to regulate the vacuum for this.
A cheep vacuum accumulator, and a needle valve to a bell jar (or use a pickle
jar). An empty helium tank (the disposable ones for filling up balloons), an LP
tank, or an air tank from Harbor Freight ($25 before the coupon, and there is
always a coupon). Draw vacuum on the tank to a reasonably low level, have the
tank connected to a jar, allow open the needle valve slowly to 'simulate
launch' close at apogee, open another needle valve to let the pressure return
to earth.
A chart converting altitude to pressure is at
https://www.sensorsone.com/altitude-pressure-units-conversion/
On 4/25/2020 9:48 AM, Lee Buchok (Redacted sender hyflynboy for DMARC) wrote:
Can’t remember exactly, it’s been awhile. I think it may have been around 4 to
5 thousand ft. I was using it only for functionality checks on an altimeter. I
remember not being able to completely seal the bell jar connections.
Sent from my iPad
On Apr 24, 2020, at 12:40 PM, Cris Erving <cris.erving@xxxxxxxxxxx> wrote:
How much "altitude" can you get with it? I got one of those two during the
25% BF sale... I haven't had the time to rig up a test jar yet.
Eggtimer Cris
From: roc-chat-bounce@xxxxxxxxxxxxx <roc-chat-bounce@xxxxxxxxxxxxx> on
behalf of dmarc-noreply@xxxxxxxxxxxxx <dmarc-noreply@xxxxxxxxxxxxx>
Sent: Friday, April 24, 2020 12:28 PM
To: roc-chat@xxxxxxxxxxxxx <roc-chat@xxxxxxxxxxxxx>
Subject: [roc-chat] Re: Vacuum Pump I found a cheap pump at Harbor Freight.
They have two grades, the cheap one was about $100 when I bought it about 4
years ago. Used it for checking altimeter along with a bell jar I got from
Amazon.
Sent from my iPhone
On Apr 23, 2020, at 9:51 AM, John Coker <john@xxxxxxxx> wrote:
I have used a venturi as well for vacuum bagging. (I use a system meant for
laminating: https://www.qualityvak.com/air.html.) I'm sure a true vacuum pump
would get a harder vacuum, but for most purposes a venturi works well enough.
Now, if you don't have a good air compressor, then a venturi is less
appealing.
John
On Thu, Apr 23, 2020 at 9:14 AM James Dougherty <jafrado@xxxxxxxxx> wrote:
Lee
https://youtu.be/cDIooANLU3Q
that Nike Nike I flew off your tower had the sustainer bagged with this pump:
https://www.fibreglast.com/product/1148_Vacuum_Generator/Vacuum_Bagging_Pumps
fins bagged with food-saver
https://www.amazon.com/dp/B07VPRW77Z/ref=cm_sw_r_cp_api_i_C6BOEb8Q8FW1V
best bang for the buck...
thanks Dierking for your remora cam
On Apr 23, 2020, at 8:27 AM, Lee Scott (Redacted sender "leescott91006" for
DMARC) <dmarc-noreply@xxxxxxxxxxxxx> wrote:
Guys in the know
I am going to be purchasing a vacuum pump in the near future and there seems
to be quite a few options.
I plan to use it for the following:
- degassing propellant for research motors
- vacuum bagging of composite laminates for fins and tubes
- testing of electronics in a chamber.
I am not necessarily looking for the best price. I am looking for a pump that
will meet my needs and not be something I need to worry about not performing as
expected.
Does anyone have any recommendations?
Thanks
Lee
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