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From the Boatshop
by Ron Magen
"Like Hell it Does
"
I've used RTV Silicone {the GE stuff} for many jobs.
What it outgases is what you smell - Acetic Acid {Chemically speaking,
White Vinegar is a 5% solution of it}. Like any chemical, you have to be
aware of what you are dealing with and take proper precautions.
I have used both the Clear and White varieties with good results and no
problems. If you use a good bit of it in a small closed space it WILL get
to you. Do all your prep work before opening the tube and ventilate closed
areas and there is no trouble. Obviously, if you are working close to
something that is VERY SENSITIVE to pH changes you should remove or mask
it.
The 'experts' say to use 3-M 5200 when you want to attach / bed something
PERMANENTLY. Once set-up the bond is supposedly almost impossible to
break. 5200 takes about 7 DAYS to 'cure'. {this can be a real problem when
you are using the '2-step' process to bed something}. 4200 was 'designed'
to be a FASTER CURE than 5200.
My personal experience is that GE Silicone can be JUST AS PERMANENT as
5200 . . . I had to repair a deck because of that. About 10 years ago I
bought a used West Wight Potter 19. I then proceeded to remove all the
weathered wood to refurbish or replace it. I also decided to re-bed all
areas where the deck or hull was penetrated. I followed the 'accepted
wisdom' and used 5200 to seat a new backing board for the o/b motor mount.
I made new Mahogany hatch slides and figured I would like to be able to
remove them for future re-finishing {if I couldn't do it 'in-place'}. In
addition, I decided to bolt them down so I used a small tube of white
silicone. When I went to snug up the bolts, on the motor mount, after a
week of 'curing', the 5200 still 'squished out' like Whipped Cream. The
silicone had 'skinned over' in an hour or so and 'cured' by the next day.
I was able to snug down the bolts and get a good, tight, seal. However, I
had forgotten to mask off the side of the Varnished wood pieces and left
the tape in place on the deck. It was a real pain to get it off the deck
where the silicone had lapped over it, and I never did get all of it off
the wood.
Fast forward 10 years . . . to last year. Due to a marina / boatyard
foul-up {they screwed up a keel & hull blasting & paint job, and had to do
it over again} the boat sat for almost a year and the cover was torn off
for a good part of that time. All the wood I had put on was in really sad
shape and I decided to remove it for refurbishment or replacement. It took
TWO DAYS of various chemicals, probing, and finally DRIVING WOOD WEDGES
{which BROKE THROUGH the DECK} to get the hatch slides off !! {". . .
silicone doesn't hold and you'll have to replace it every couple of years
. . ." - - LIKE HELL IT DOES }.
This time I was a little smarter . . . a 'good seal' is one thing, but
this is ridiculous. After repairing the deck with epoxy and Gelcoat
paste, I again used GE Silicone {RTV} in a 'gun size' tube from Home
Depot. I made new slides and gave them about six coats of varnish, with 3
coats on the bottom. After masking off the deck I gave it 2 coats of wax .
. . NOT buffing the second. I did the same to the BOTTOM & SIDES of the
slides, then masked them. I gunned a good layer of the silicone on the
marked perimeter on the deck, and on the center portion of the slides.
Settled them in place and set the bolts to get a good, even, squeeze out.
A finger wetted with liquid soap made a nice fillet. A couple of hours
later I removed the tape . . . easily & cleanly this time. A day or so
later I was able to snug up the bolts and 'rolled out' a nice bulge along
all edges; easily trimmed with a knife and sharpened piece of scrap wood.
The 'wax barrier' should allow a good seal around the bolts, yet make
future removal very easy . . . or so the theory goes . . . we'll see in 10
years.
Ron Magen
Backyard Boatshop |
