The Murphy Builders Site

Not sure the following means much and I wouldn't worry about it if you've used
PRC1422 but as I understand it:

Although used in amateur built fuel tanks, PRC1422 uses a dichromate hardener
and is NOT mil spec according to Leavens Aviation, the Canadian distributor.

PRC1440 uses a manganese dioxide based hardener and is the mil spec stuff for
fuel. This is the stuff that MAM lists as equivalent to what they ship. It is
more difficult to obtain (but the same price) where I am, and I'm not really
sure it matters, but given a choice it probably makes sense to stay with the
1440 in case it is more compatable. If anybody needs it, I will look up the
other equivalents as they are listed on the PRC sheets that MAM included with my
manual.

I couldn't obtain the 1440A brushable in a pint can but a 3.5 ounce Semkit (more
expensive) was about the right amount for brushing the rivets and seams of one
fuel tank. Or in my case, one Semkit before both tank tops were installed, and
one after the tops were installed.

Ken

PS - I wasn't near brave enough to consider testing with fuel before closing my
tanks. Nor did I feel the need to with fillets everywhere including around the
rivets. Like Warren I had no leaks. Well actually I had several leaks, but soapy
water traced them all to the various temporary plugs and balloons that were
installed for the air pressure test. Dish soap and water works much better than
laundry detergent.


"Warren T. Montgomery" wrote:

I didn't pre-test prior to the top skin , however I did use PRC1422A,
brushable on all rivets and seams.

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Leakless,

My SR, 2nd wing has been sitting for five days under pressure with no
leaks! :-) 2 fer 2!!
I didn't pre-test prior to the top skin , however I did use PRC1422A,
brushable on all rivets and seams.
In fact what I did was wash & clean the entire area, rivets and all with
lacquer thinner while the PRC-B was still wet.
Except I was liberal with the PRC-B on corners and stringers.
I then scotch brited all surfaces followed by the 1422A on the seams,
rivets, corners and toast.
By close up I was 99.99% sure I wasn't going to have any leaks.
I certainly wouldn't use fuel to pre-test as I might forget to put out
my Cuban. (not a problem in the US)
I've heard of alot of complicated testing systems however what I did was
simple and I didn't have to run out to the hardware store.
Attached all nylon fittings, fuel caps and drain.
cut off inner tube valve stem and with short hose attached to tank
fitting.
tripled three party ballons (for after celebrations) and attached to
fitting.
Sealed extra fittings with pieces of inner tube.
was able to pressurize the trippled ballons to about 1psi.
measured outside circumference of ballon and monitored. (finished flaps)
EASY, now I can take the ballons off and have a party.Hey my birthday is
even on the 17th and the wife is out shopping for a bench grinder for my
3M wheel! Life is great!! and as BobP says, no more toast and PRC in the
morning.

Sealed,

--
Warren T. Montgomery
<monty@emirates.net.ae>
Dubai, United Arab Emirates

From: Hibbs <hibbs@pacifier.com>
To: Murphy Rebel Builders List <murphy-rebel@dcsol.com>
Subject: Gas vs H20

2nd, I am testing my fuel tank (the top is not on yet) by using water.
The molecular size is smaller than gas. Anyone else used water for the
1st test (the 2nd will be air once the top is on)? Is there any reason
to think that leaks might show up better as a reaction to gas
(separation, bubbling, etc.)? The spec sheet on proseal shows it has
been test with salt water and jet fuel.

Leakless (so far) in Vancouver

Scott Hibbs
hibbs@pacifier.com

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