|SJ23 Tech Tip B12, (Updated 2017-12-11) Bob Schimmel|
is a tough and durable material if
it matches the application. For the wrong application it can be brittle
and weak. On the bow of an
SJ23 it's quite suitable as long as you don't stand on it or rub a line
over the edge of it. Try telling that to a weekend cruiser who's
working up a sweat to retrieve 100 feet of anchor line and chain without an anchor roller!
They're very likely to use the edge of the cap to pull the line in. That being the case, the edges of the cap
will develop grooves very quickly.
What prompted me to make a new cap for Panache was an incident I had
moving a very heavy mooring prior to having an anchor roller. See Tech
tip B26. The
1/2" line slipped off the cleat and as the cement block went screaming to
the bottom the line melted a groove through the edge of the cap, melting it
like hot butter. I temporarily sealed the groove with Sikaflex,
but it's not the same as an intact cap.
At the time of this writing Gene Adams of PORT GARDENER SAILBOATS manufactured black replacement fibreglass caps and sold them for about $35.00 US each. They are far more robust than the original factory caps. San Juan Sailboats still sells them today.
if you want a really tough bow cap that will probably outlast your boat
consider making one from sheet metal. Enclosed in this Tech Tip are three
versions plus another idea for sealing a cap. They may seem
difficult to make,
but with a little forethought anything is possible. If you know somebody
who is experienced in sheet metal work you'll be surprised at the ideas
that pop up. You might require the services of a TIG (tungsten inert gas) welder.
HULL CONSTRUCTION INFO
- The factory bow cap shown below is made of a black fiberglass material
that is glued to the bow with the same polyester mash (a lightly catalyzed putty called thicksol)
that is used to
fasten the hull liner to the hull. The edges of the cap are sealed with a
that is likely Boat Caulk, Life Caulk or maybe butyl rubber.
The first two were
popular sealants in the early 1970s. (Butyl
rubber was used for a car windshield in the 1970s when they weren't an
integral body component like they are today). If one of
the of two caulks was used it is likely dried up and leaking by now. In fact, it would surprise me if it
TO DECK CONSTRUCTION - The SJ23 hull to deck joint consists of an
inward pointing fibreglass flange that is actually the top 1" of the
hull, rolled inwards. The balsa cored deck lays on top of the flange and
butyl rubber is used as a sealant and an adhesive between the flange and
the deck. The edge of the deck consists of solid fibreglass for strength.
An aluminum toe rail caps the joint and the toe rail is
through bolted to the deck every 6". The
screws should be tightened occasionally to keep the joint snug. Do not over tighten,
slightly tighter than snug is sufficient. You should not compress the butyl
rubber. This joint is designed to be slightly flexible. Fiberglas
mash was used under the bow cap to fill gaps and to hold it down to the deck.
last through bolts are installed in the end of the toe rail about a foot
from the stem, just aft of the cap. The deck extends to the
stem where the end is covered by the bow cap. The deck fits snug on top of the
stem and is attached to the fibreglass hull flanges with two pop rivets.
It is also through bolted to the forestay
fitting. (If this sounds like minimal support
under the bow cap, keep in mind that the small bulkhead that forms the aft
end of the anchor locker adds significant strength to the bow by keeping
the hull sides together). However, the lack of a toe rail in the
forward section creates a relatively unsupported area. In addition,
several 1" diameter holes may be drilled through this portion of the
deck to pass the electrical wiring for the bow running lights. See
images above. Unfortunately the factory didn't seal the edges of these
holes so the balsa core is exposed to the full humidity of the anchor
locker. In addition, the leading edges of the toe rails are probably NOT
sealed to the deck so any water that is driven under the cap will flow
under the toe rail and likely appear somewhere alongside the low side of
the hull. Gawd such simple things to do properly
at the factory! However, NOW is an excellent time to seal
these holes after the core of the wood is bone dry. Use epoxy to seal
the balsa core in the holes. Use Sikaflex to seal the hull to deck joint
around the deck and to seal the leading end of each toe rail.
|CONSTRUCTING the CAP - Unbolt
and remove the forestay fitting. Scrape the old sealant off as the fitting
will be reused. Gently remove the old cap with a knife, long screw driver,
etc, cutting through the sealant and gently prying the cap up. Scrape the old
sealant off the deck area till it's whistle clean.
INSTALL the CAP
decided to replace the bow cap on Malia. The redesign and installation are
all his handy work. He made a pattern and a local welder cut the stainless
steel sheet metal then welded them together. The integrated cap & forestay
fitting is bolted down by
the screws through the mooring chocks and through the holes where the
forestay fitting is bolted. The entire structure is strong enough that
it replaced the forestay fitting with a new plate you see welded
plate is extended back to fit under the
chocks and the hull portion is extended down to cover the forestay holes.
The forestay load is supported by the stem bolts. The smooth shape creates excellent protection from anchor damage,
adds strength to the bow and totally seals the bow. The outside corners
below the mooring cleats are rounded so the mooring line can't chafe. Rather
than match the blunt bow curve of the stem, he extended
the deck and stem lines out to where the two sheets meet, creating a distinctive and
shape. Another nice feature of his design is the smooth
bottom of the cap edge. If the bow should come down on something solid,
this will minimize the chances of "lifting" the cap off the deck.
Alan had a bit of a nasty surprise when Elizabeth Jane broke free from her
mooring. Her mast got hung up on a tree and her bow was scraped when it met with a sandstone cliff. A new stainless steel bow
cap was fabricated by a local Wisconsin machine shop at a cost of $850 US.
The new cap is well sealed to the hull to prevent water ingress which
further increased the overall strength.
The end product is far stronger than the factory original.
Like version II above, Alan also incorporated smooth sides so the cap cannot
be lifted. And while he was at it, he installed new navigation
lights on the hull to clear the cap for deck work. Its always good to
consider all aspects of a repair. Very clean neat job.
And finally if you've replaced the puny factory deck lights with Fresnel lights (Aqua Signal 25) installed on the pulpit and the cap is still in good condition, then all you really have to do is plug the light fixture holes. This is what Randy did. He cut an aluminum plate to fit the cap, sealed it with butyl rubber then screwed it down with 4 stainless screws. It takes a bit of pressure to spread the butyl rubber which is best done with a heat gun. Alternatively you can park the boat in the hot sun and let Mother Nature do the heating for you. Make a fillet with the rubber that oozes out along the perimeter out and remember to seal under the screw heads. Job done. No point in making it more complicated than it needs to be.
By the way that's a Hood furling system fitted to the boat. I knew you were going to ask this.