The Murphy Builders Site

Well there was a whopping amount of response to all those key strokes...
so
I can only assume you're all out there busily scrubbing aluminum with
Scotchbrite!! Missed a spot.. lol

More tips & tricks from today...

Where cheap clothes... coveralls or a work/lab coat that you dont' care
about, that has pockets for clecos.

Put on a pair of latex gloves.

Now put on another pair of latex gloves!

Measuring proseal/prc/sealpack/what have you is not a guessing game... no
scooping some of this and a bit of that..... buy a digital scale.

Mix EXACTLY 10 to 1. It's simple. Throw a scrap piece of .025 about 4" x
6"
on the scale and hit Tare to zero. Coax, for example, 90 grams of the
white
gooey stuff out onto the aluminum and then put the lid back on the can.
Open
the catalyst and stir it up GOOD with a popcycle stick. Carefully add
EXACTLY 9 grams of it to the top of the white heap. Clean the stick on the
side of the jar to get everything back in there and recap it. Then get
your
1" wide putty knife out and mix.. and mix.. and mix somemore 'till it is
absolutely consistant looking with no white streaks.

Spar to rib areas you can use your putty knife to lay down a strip of
sealer
about 1/16th inch deep. Everywhere else I use popcycle sticks for their
filleting abilty and easy of use. Tongue depressors broken in half down
the
middle have places to be used as well giving you one rounded side and one
sharp corner.

Pre-plan what you are going to accomplish... lay all the parts out in the
order they are going to go together. Give thought to what rivets you need
and have them out in open containers to easily pick up one at at time.

For an example of the amount of material to use... I mixed 90 + 9 Proseal
to
start the day, along with 1 teaspoon + 1/2 catalyst of Epoxy cromate that
I
mixed first so it could flash before I got going.

The epoxy was for the trailing edge, rib flange to spar, of the wing ribs.
Between seams and to dip rivets to insert and pull.

The 90 grams of Proseal I mixed installed the outboard tank rib and the
two
center ribs... along with all three rear bulkheads except for the flange
of
the last one that mates to the root rib. This was enough material to seal,
rivet and then smear a layer overtop to make sure the flange was sealed
tight... as where all the rivet heads. No need to use "tank" rivets while
putting the ribs and such in...as you can seal overtop of them all. Be
sure
to rivet with manufactures heads on the INSIDE of the tank where ever
possible. Just makes life that much easier.

Now by the time I got this 90 grams used up and the three ribs and 2.5
bulkheads in place I was running out of workable time on this stuff and I
was also out, but it was already tacking where I'd been...... so I'd
suggest
batches of about 60 grams when doing the tedious parts so you're not
throwing unworkable stuff out.

I then mixed another 60 + 6 to do the root rib, the last bulkhead rivet
flange and the fuel fittings and stringer fillers on the root rib. It
wasn't
enough.. I ran out with 2 fillers and the vent fitting to install. Mixed
another 60+ 6.... installed the last 3 items, smeared the tank side and
outside faces of them... and then built dams in a few corners on the rear
bulkheads for future lid seal down with the remainder.

Total time to get one 3 bay tanks ribs/bulkheads and all root fittings and
fillers in place... about 5.5 hours Even I was optimistic when starting
this
morning that I was gonna get both done... and I've done this many many
times. Guess I should have looked at my past work logs! Tomorrow... tackle
tank #2 and then I can let it cure a few days and start on the top and
bottom skins. I'll take some pictures when I get to the "little clip"
stage
of that to positon the outboard tank rib so I can Proseal the stringer
fillers and spar fillers in place without the rib moving out of positon.

Wayne


----- Original Message -----
From: "Wayne G. O'Shea" <oifa@irishfield.on.ca>
To: <ted@vafm.org>
Cc: "Murphy Rebel Builders List" <rebel-builders@dcsol.com>
Sent: Wednesday, January 11, 2012 7:45 PM
Subject: Re: [rebel-builders] Building a leak free fuel tank.. Rebel,
Elite,
SR, Moose.. breed doesn't matter.

Well it's not all there.. but it's a start!! LOL

I should also note for the SR guys...

Be sure to seal the spar doublers plates while building up the spars....
the
SR/Moose doesn't have rear tank bulkheads.. etc to require worrying about
the "joggle"... but it all comes down to being like a paint job where 90%
of
the job is preperation!

Well actually it's 75% getting your mind wrapped around mixing up that
sinky, black goo and dawning gloves with enthusiasm...23% prep work and
2%
putting it all together !!

Wayne

----- Original Message -----
From: "Ted Waltman" <ted@vafm.org>
To: "'Wayne G. O'Shea'" <oifa@irishfield.on.ca>
Sent: Wednesday, January 11, 2012 7:39 PM
Subject: RE: [rebel-builders] Building a leak free fuel tank.. Rebel,
Elite,
SR, Moose.. breed doesn't matter.

Thank you for your time in thoroughly documenting this Wayne. Much
appreciated!!!!

Ted

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of
Wayne
G. O'Shea
Sent: Wednesday, January 11, 2012 5:05 PM
To: rebel-builders@dcsol.com
Subject: [rebel-builders] Building a leak free fuel tank.. Rebel, Elite,
SR,
Moose.. breed doesn't matter.

Guess I could have added some more to this the other day.. but with me
being
what seems like about 2 years behind in the shop my patience isn't what
it
could be these days.

So with tank "pre-prep" on the top of my mind, after spending an entire
day
getting parts prepped for sealer tomorrow, I offer the following in
addition
to the great advise Ken has already offered and like Bob says most of
this
has been covered for years and can be found somewhere in the archives.

I see leaking tank after leaking tank that the builder put ABSOLUTELY no
effort or time into preparing to build a leak proof tank. I regularily
find
no evidence of scotchbriting a nice cross hatch pattern in all the
mating
parts, if any scotchbriting at all. Guys expecting
Proseal/Chempac/PRC/Flamemaster to stick over top of epoxy chromate in
the
tank area. Now that just ain't gonna happen!

To give an idea of time... I spent 4 hours scotchbriting the 8 ribs, 6
rear
bulkheads and all the little filler clips and fuel fitting bushings for
two
tanks today for a pair of Rebel wings. I had already previously spent a
few
hours scotchbriting the main spar and stringers where they go thru the
outboard tank rib. This was all done with a 2" coarse scotchbrite disc
in
my
air drill... then everything was gone over with a piece of hand held
coarse
scotchbrite material to be certain that everything was done and to get
in
all the little tight corners/nooks and crannies! Every stringer
"clip/filler".. end rib angle filler.. spar filler.. etc scotchbrited by
hand on both side.

Prior to scotchbriting EVERY inch of aluminum was precleaned with
Acetone.
After scotchbriting I spent about 2.5 hours cleaning everything with
Acetone
again... like Ken says... you clean until the cloth stays white and then
some. I use white papertowel.. and take a single sheet and fold it
numerous
times. This way you have a "sponge" holding Acetone and you can refold
it
in
numerous directions before throwing it in the fire once you have every
face
of the thing black.

During cleaning I even caught myself where I had missed a joggle on a
rear
bulkhead with the scotchbrite wheel.... thank god as that is the most
prone
place for leaks. You need to scotchbrite the hell out of the joggle area
on
the bulkhead and then do the same on the inside surfaces of the rib
flange
where it fits in place. This joggle area MUST be sealed while you are
riveting in the tank bulkheads or you are doomed from the start! Be sure
to
scotchbrite the underside of all the flanges in the tank area.. and
ANYWHERE
that sealer may sit be it from what you spread or from where the dipped
rivet gets pulled tight.

Now keep in mind.. the time frame above.. this is strictly the ribs,
bulkheads and clips. I haven't even mfg'd the tank skins yet as there is
no
point at this stage as the hole pattern will change slightly once I seal
and
rivet the rear tank bulkheads in place. So tomorrow the ribs/bulkheads
get
sealed and riveted hopefully... and then after a few days cure I'll be
able
to start making skins... and more scotchbrite.. more cleaning.. etc.

The trick is to work your way towards a complete "bathtub"... getting
the
bottom skin/ribs/bulkheads all in place and sealed. NO .. more sealer
isn't
the answer, good prep on the mating seams with about an extra 1/2"
scotchbrited out onto skins and ribs is the key to make one nice smooth
light coat of sealer do it's job properly by giving it something to
adhere
to.

When it comes time for the top skin.. there are two ways to do it... and
you
need to preplan this so your stringer filler "clips" have been fitted
inside
or outside the tank.

If your top wing skin is already in place with stringers on it.....
before
you can place the top tank skin there should be no filleting required
anywhere in the tanks. All that should be left to do is put a bead of
sealer
around the perimiter and down the stringers and place the top skin. Pre
cleco the holes in the tank skin before placing..... a pair for every
rib
flange.... a pair in every bulhead flange and a few for stringers.

Now the big trick to being able to do what I've stated above.. is you
have
to have your stringers sealed thru the outboard rib... and of course
it's
waving all over the place so how the hell do you do that and have it in
the
correct place... right. Well you make little tying clips from a hole
mess
of
little rectangles of .025 or .032 scraps. Transfer the hole pattern from
your tank skin overlap to wing skin holes, to the outboard fuel tank rib
flange holes. Then cleco these little "tie clips" between the wing skin
and
the outboard tank rib flange. While you are at it take another long
strip
of
material and transfer the holes on the tank skin between the three
stringers.. a front spar hole and a rear bulkhead hole. Now the clips
will
hold the rib exactly where it's supposed to be and the longer strap will
hold the stringers fore/aft where they are supposed to be.... and you
can
install your stringer fillers now with sealer and rivets. Then you can
work
the sealant in.. around.. thru.. the stringers and both inboard and
outboard
of the tank until you are absolutely sure there isn't a pinhole thru
there.
Once you've got that covered then you want to build dams between rib
flanges
and stringers and at any corners of rib to spar or rib to rear bulkhead
junction until you have a complete.. flat.. sealing surface for the top
skin
to set down on.

If you haven't placed your top wing skin yet or riveted the stringers to
it... you can do your tank first. Follow most of the above other than
the
need for the little rib holding clips etc. Seal and rivet the stringers
to
the top tank skin. Have the tank as ready as possible for a flat sealing
surface and do the cleco pairs etc.. put the bead of sealer down and get
the
skin in place and start dipping/rolling rivets and placing them in
holes.
Have a piece of scrap 0.025 material ready to slide in under the tank
skin
at the main spar, to simulate the wing skin going between them, so
sealer
doesn't ouzz into the space. Now pull all the rivets that you've
dipped/rolled in sealer before placing and once complete you can get in
under the tank skin overhang and work on filling the tank
stringers/fillers
to a perfect seal.

When in doubt on the stringers.. turn the lights out in the shop and
shine
a
bright light down the stringer from the wing tip and look in the tank
filler
for light coming in... or visa/versa.. light in the tank and go look in
each
stringer curl at the wing tip for light shining out.

Enough for my head tonight after all that Acetone...

;O)
Wayne


----- Original Message -----
From: "Bob Patterson" <bobp@prosumers.ca>
To: <rebel-builders@dcsol.com>
Sent: Friday, January 06, 2012 4:49 PM
Subject: Re: [rebel-builders] Re: [rebel-builders] top tank skin removal




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