Forwarded message from David Wilshin
Date: Mon, 28 Dec 2009 11:29:10 -0800
From: David Wilshin
Reply-To: David Wilshin
Subject: Mason 43 Deck Prism Installation
To: email@example.com, Bob Miller
Ross, As promised, attached is my explanation of the installation of my boat deck prism.
Also a couple of pictures: during and after. Feel free to use it or not as you see fit
for your website, and to edit appropriately, etc. Thanks for your assistance. I can't
imagine the out come if I not had it. All the best for a great New Year. May you"go cruising"
in 2010 if that is your desire. Bob, Feel free to post this on the Mason website. I have not
forgotten about signing up, but this write-up was first on my priority list. However, please
continue to cut me some slack as we are in the process of selling a house, buying a house,
selling a boat, and closing an office. I have a lot on my plate.
Thanks very much.
Happy New Year! Kindest regards to you both.
Click On The Pictures For Detail
Boat Deck Prism Installation
Following is a description of the installation of a replacement boat deck prism on S/V Always, Mason 43 #37, in December, 2009.
The installation was based on guidance from Ross Bruce, proprietor of www.boatdeckprism.ca, who also provided the replacement prism
and polished stainless holder plate.
Prior to installation we had to decide which type of installation was appropriate. One available system consists of a flat trim
plate which fits into a recess around the edge of the prism. This is the system originally employed on Always. The alternate,
and preferable system according to Ross, consists of a trim plate which is designed to hold and support the prism, rather than
merely trim its outside edge.
We opted to follow Ross’s suggestion. Doing so may mean that the prism will "never need to be replace again." However, we later
learned that one consequence of that decision was that we were compelled to modify the deck to receive the preferred but larger
trim plate. So those unwilling to undertake modification of the deck may prefer to stick with simply replacing the original prism
and flat trim piece, although according to Ross doing so may result in a greater likelihood of future leaks.
We began by removing the old trim plate and prism. A heat gun softened the old sealant and facilitated the process. We left the below
deck area open so we could push the loose prism up and remove it from above deck. We also gently removed the below-deck
trim piece which was easily removed after the softening of the old sealant. Then we sealed the opening below deck with newspaper
taped to the headliner all around the edges. This proved effective in preventing dust and dirt from fouling the nav station during
the remainder of the deck preparation.
Examination of the hole in the deck following removal of remnants of the old sealant revealed that the entire hole through the deck
layers had been epoxied so that water leaking around the old prism had not penetrated into any of the deck layers or balsa core.
However, the screw holes for the deck plate had not had epoxy treatment and had therefore been susceptible to water intrusion around
the screws to the extent the old sealant had failed.
Since we had decided to install the polished stainless holder and trim ( www.boatdeckprism.ca part number 141 ), we needed to expand the
hole in the deck to accommodate the larger stainless holder. We chiseled the teak decking down to the fiberglass beneath. Then a
grinder took the fiberglass upper layer of deck and balsa core to the proper width and depth determined by the size of the outside
of the stainless holder and trim, allowing sufficient room around the holder on the bottom and sides for a bead of sealant no less
than 1/8" and for epoxy to seal the sides and bottom of the cut-out. Per Ross’s suggestion a high speed rotary saw blade worked well
to rout out the corners the grinder couldn’t get into. The rotary saw blades are available at Home Depot and are designed for the
rotary saws used to cut sheetrock and other materials. However, the blades worked in our Dremel tool so we were not compelled to buy
a rotary saw. Since the teak deck was not completely flat, following completion of the opening itself we chiseled the deck slightly
as needed to assure the holder would sit flat on the deck and not tend to rock underfoot after installation.
Because we were now into the balsa core we used marine epoxy to seal the opening. For the vertical surfaces, before adding the hardener
to the resin we thickened the resin with baby powder to get it to a peanut butter consistency so that it could be applied with a putty
knife and would remain in place. Ross had suggested talcum powder or baby powder. Baby powder was easier for us to find. He also
suggested tape to hold the epoxy in place as it cured, although our mix was stiff enough as not to run after application and tape was
not necessary. You can use the trim piece here with multiple layers of tape to act as a spacer and create room for the sealant. Ross
indicates that neither masking tape nor duct tape will stick to the epoxy.
At this stage we also drilled oversized holes where the screws for the stainless holder and trim were to go, and then filled these holes
with epoxy. These were drilled out later to permit screwing in the screws to hold the frame to the deck. The epoxy plugs will prevent
water from passing around the screws and into the deck and core.
The accompanying photo shows the completed opening. The blue tape marks the edges of the new stainless holder. The epoxy on the balsa
core is clear, whereas the epoxy in the screw hole plugs is gray in color as a result of the addition of baby powder as a thickener
before addition of the hardener. The dark line near at the sunlit end of the opening is a shadow resulting from the shallow chiseling
out of the deck to receive and level the original flat trim plate. Also evident in this photo is the upper edge of the below-deck trim piece.
Since we were installing the prism into the stainless holder and trim we needed to create sufficient "shims" to support the prism at the
right height in the holder so that as the soft sealant cured it would not compress by gravity and permit the prism to sink too deeply into
the holder. We followed Ross’s suggestion to turn the prism upside down with the "mountain" pointing up. This exposed the horizontal
surface of the prism which would eventually be suspended by the stainless holder. We then applied small "candy kisses" of sealant to the
surface of the prism at close intervals, e.g., ¾", being careful not to get them too close to the "base" of the mountain where the
below-deck trim piece would eventually go. After a couple of days of cure time, using an exacto knife and a razor blade we trimmed the
candy kisses to the proper height to allow the prism to sit in the stainless holder so that the top of the prism was at or below the top
of the holder.
The sealant Ross suggested was GE SilPruf scs2000 series silicone sealant. If you can’t find it locally, you might find it as we did at
amazon.com and technologylk.com. Order two tubes. One was not sufficient for our installation, although it likely would have been if our
installation had been solely replacement of the prism and the flat plate. Ross indicated this sealant is used for installation of glass
into window frames and is formulated to take the elements. It comes in several colors. We opted for black, consistent with the deck
caulking and the prior prism caulking.
Installation of Frame and Prism
Before installing the frame to the deck we drilled holes in the epoxy plugs to the proper depth for the screws. We then went below deck,
carefully (to minimize falling dust) removed the newspaper, reinstalled the inside trim piece, and then recovered the opening. Then, back
topside, after carefully taping every surface on which we did not want sealant, we pumped sealant into the deck opening and around the
stainless holder and inserted the holder into the deck, securing it with screws.
While it might have been possible at this point to also install the prism into the frame, we opted to allow the sealant to cure around the
stainless holder before installing the prism. Partly this was a function of the nature of the sealant. Before cure it is gooey and goes
everywhere. We had our hands full keeping the deck and holder clean just installing the frame. Had we tried to install the prism at that
time, we likely would have had sealant where we didn’t want it. After the curing of the sealant around the stainless holder we installed
Errant sealant is easily removable after about 4-6 hours of curing by rubbing it into a ball similar to the way rubbers cement does. Since
the sealant is initially sticky and gooey, we found tooling to a smooth bead somewhat difficult, as it stuck to our tools, whether metal
or plastic. We suspect that minor imperfections in the bead will quickly disappear with wear, as will the glorious shine on the exposed
surface of the holder. The installation has been storm-tested, and doesn’t leak. We’re thrilled! And there is more light below than came
through the original prism.
Comments on Order of Work
Review of our notes from conversation with Ross indicates he suggested installing the glass to the prism first, and then installing the
combined unit into the deck. On reflection, given our need to fit the glass not only into the stainless holder but also into the below-deck
trim piece, we are satisfied with our procedure of installing the holder to the deck before installing the glass to the holder.
In hindsight we suggest doing the prism candy kiss installation simultaneously with the deck preparation so as not to lose two days waiting
for the kisses to cure so they can be trimmed to the proper height.
Watch your weather window as you will have a hole in the deck for a while. We were compelled to duct tape and cover from one winter storm
mid-process. Duct tape does not stick well on the teak deck, so give some thought to your temporary weather seal. Also, we found that
even without a storm in the forecast we were susceptible to water intrusion from dew running down the side of the cabin top. Fortunately,
our situation was no-harm-no-foul, but none of us wants water in the nav station. It’s why we’re replacing the prism in the first place!
Final Comment on www.boatdeckprism.ca
Ross Bruce was great to work with. But if you are even considering "someday" replacing your prism in the deep recesses of your mind, do
not delay at least ordering the prism and trim. He told us that in about a year he is "going cruising." And since he is a one-man shop,
you will no longer be able to get his products, much less his advice and counsel.
Have fun! Another great boat project!
Dave Wilshin, S/V Always, December, 2009