Chain Plate Inspection and
One of the necessary evils of owning a boat
is the requirement to re-bed deck hardware from time to time. The C34 has a
well-designed chain plate system that effectively transfers the rigging load
from the shrouds to the deck and the hull. Unlike many sailboats, the
plates are not tied to a bulkhead or any interior wood work. The holes for
the plates do, however, pass through the deck which is a sandwich is made up
of the hull liner, plywood and the deck laminate. In Mark I boats, the
holes were cut and the chain plates installed with bedding compound. The
edges of the laminated plywood were left exposed. This is a prime source of
water intrusion that can lead to deck rot and delamination. If extensive,
this rot requires major structural repair and is best avoided by properly
maintaining the bedding compound used to seal the chain plate holes in the
deck. The interior chain plate assemblies should be regularly inspected for
the presence of leaks. Leaks are evidenced by presence of water, corrosion
on plate components or brown staining around the plate assemblies. Water
that leaks through the plates is likely to run down the rod assembly and
cause water damage to the wood shelving behind the settees.
Chain plate shows signs of surface corrosion due to leaking around the bolt
on the left and the top edge of the plate. This was the original factory
bedding, 19-years old at the time the picture was taken—long over-due for
The proper bedding
material for chain plates is polysulfide. Boatlife Life Caulk or 3M 101 are
two readily available examples. The prime benefits of polysulfide are its
sealing properties, flexibility when cured and that it is readily removed
when it’s time to re-bed in the future. The only down side to polysulfide
is the time required for a complete cure—up to 21 days in cold
temperatures. Polyurethane adhesive/sealants such as 3M 5200 should not be
used as their primary purpose is to adhere, not seal components. Due to
flexing and maintenance requirements it WILL be necessary in the future to
be able to disassemble the chain plates. Polyether sealants may be used (3M
4000 UV or West Marine Multi-caulk) as can silicone, especially if limited
time is available for bedding jobs.
This repair is best
accomplished with the boat in the water. This will allow the bedding to
cure with the chain plates under tension. It’s best to work on the same
shroud on both sides of the boat at the same time, i.e., aft lowers, uppers
or forward lowers. The first step is to treat your turnbuckles to a spray
of lubricant. Then, remove the cotter pins from the bolts. The turn buckle
is loosened with two wrenches, one to hold the shroud stationary and the
other to turn the turn buckle. Two adjustable wrenches will work. A medium
and large type works the best, using the medium wrench to hold the shroud
and the large wrench on the center of the turn buckle. It is important not
to allow the shroud to twist when loosening the turnbuckle. Only the turn
buckle should turn. Turn the turnbuckle for a turn or two and look at the
threads to determine if you are tightening or loosening it. When viewed
from above, most turnbuckle assemblies are rotated counter-clock wise to
loosen. Continue to loosen the turnbuckle until the shroud is slack and you
can remove the cotter pin in the clevis pin holding the t-bolt to the chain
plate. Disconnect the shroud from the chain plate.
Bolt, lock washer
and bushing at the base of the rod. The assembly shown does not have a lock
nut. Note beveled aluminum bushing at the top of the assembly.
The next step is to go below and remove the
back cushions on the settees to access the bolts at the bottom of the rod.
Use a 15/16” wrench to loosen these bolts. A shot of lubricant will help if
the bolts have not been loosened. Some boats have two nuts—the lower nut is
a lock nut to ensure the upper nut doesn’t back off. Other boats are
equipped with multiple lock washers. Be sure that after you loosen these
bolts you catch all of the hardware so that it’s not lost in the recesses of
the hull. You may or may not be able to slide the aluminum beveled bushing
at the top of the assembly. If there has been any leaking, the aluminum may
have corroded slightly to the stainless rod. A tap with a hammer will
usually be sufficient to loosen this bushing. Each bushing is different; so
use care not to mix them up. Also note which side is the top and bottom
when you remove it and mark it so that it’s reinstalled properly. If you
don’t wish to completely disassemble and lubricate or remove the rod, it’s
only necessary to loosen the bolt a bit to allow you twist the rod out of
the chain plate fitting.
To remove the rod from
the chain plate base, just turn it until it’s loose. This will be easier
with a bit of lubricant, a light tap with a hammer and then a non-marring
vice grip or channel lock pliers. Use care not to damage the polished
stainless rod. After it’s screwed out of the chain plate, allow the rod to
slide down to rest on the hull. It is possible to remove the upper and aft
rods if you wish to clean them up, but the forward lower rods are difficult
to remove unless the teak trim strip below the port lights is removed.
The next step is to go
back up on deck and remove the chain plate covers. These are the metal
rectangles that surround the base of the chain plate and are held in place
with two small #8 ¾” stainless screws. Remove the screws and gently pry the
cover off of the deck. It will be necessary to clean the old sealant from
the cover after removal.
Figure 3 and 4.
Chain plate cover
and machine screws that hold plate to the bottom of the deck. The screws
will be replaced with hex head bolts and the standard washers will be
replaced with fender washers during reassembly.
nuts down below.
Figure 6 and 7.
Remove nut, lock
washer and angled aluminum washer behind settee and unscrew the threaded
chain plate cover.
the seal and removing chain plate from the deck. This can be aided if
someone can step on the plate from above and provide downward pressure
The last step is to remove the two 3/8” x
16 course threaded machine screws that hold the plate to the deck. This is
a one person job as the screws and bolts can be accessed by reaching through
open portholes. Once the bolts are removed, the easiest way to pry the
plate from the bottom of the deck is to go above and simply stand on the
plate to put pressure on it. Apply smooth steady pressure—don’t stomp on
it. If you are working alone, be sure to put something below to catch the
plate when it falls as it weighs several pounds. After removal, the chain
plate components should be disassembled and cleaned.
This is how the port
upper plate looked after removal and before it was cleaned. After cleaning,
there was only minor surface corrosion which was removed and the plate was
Old sealant and any surface corrosion
should be cleaned from the plates and components after removal. A
combination of steel wool, a wire brush, Scotchbrite, razor scraper, small
screw driver and elbow grease will aid with mechanical removal of ALL of the
old sealant. Any sealant not removed may prevent proper adhesion of the new
bedding compound during re-installation. The plate components should be
inspected for any signs of corrosion. Welds should be inspected for any
signs of fatigue. Some light pitting as the result of surface corrosion is
probably O.K.; but any cracks or fissures should be suspect. Any suspect
plates should be replaced. Replacement plates can be obtained from
Catalina. You’ll need to specify your hull number, year built and which
chain plate when ordering.
Disassembled chain plate
components. This is the port aft lower plate from Hull 563 and is a
different design than the other five. It has bolts in addition to the weld
holding the chain plate to the base. Based on the type and condition of the
sealant, it appears that this plate was installed at the factory during
The other five plates on
Hull 563 do not have bolts reinforcing the weld. Additionally, the have
heavier gauge metal for the hinge plates on the bottom. Note the markings
to aid in re-installation. It DOES matter that the plates be re-installed
in the same orientation in which they were removed.
Cleaning the deck and
chain plate cut-out will require some effort. Our chain plates were
installed at the factory with silicone. Of the six plates, only one showed
no signs of leaking after twenty years. Five simply required cleaning and a
coat of clear, deep-penetrating epoxy (CDPE) to seal the exposed edge of the
3/8” plywood in the deck laminate. One had some rot in the plywood around
the bolt holes and cutout which required repair, and this chain plate also
exhibited sufficient signs of corrosion to warrant replacement.
or polyurethane sealants require mechanical removal. A combination of small
screw driver, Scotchbrite and a small stainless steel brush will remove the
sealant from the no-skid deck. A 3/8” drill can be used to clean the bolt
holes and a combination of files and sand paper will clean the inside of the
chain plate cut-out. The wood in the deck laminate should be inspected. If
it is the color of normal wood, there is no rot. If it has turned black,
but resists probing with a knife or other sharp object, it should be dried
out and then treated with CDPE. Even if there is no sign of rot, two coats
of CDPE will encapsulate the wood and prevent damage in the future. The
inside of the bolt holes should be treated as well as the outboard cover
plate screw hole (this will require the use of a syringe to apply the
This plate showed signs
of minimal leakage. There is some mold in the plywood, but this laminate
can be preserved with an application of CDPE. Note the remains of the
factory-applied silicone. This silicone held up well for 19-years.
If there has been sufficient leaking to
allow the plywood core to rot, repair is more problematic. Visual
indication of problems may include gel-coat cracking if the upper glass
laminate has been stressed by compression. A simple tap test with a hard
object will also provide some clue as to the extent of the core damage.
Ultimately, a moisture meter will be required if the damage appears to be
extensive. The repair described in this article is sufficient if core
damage is limited to a small area around the bolt holes and cut-out. An
excellent discussion of core repair can be found at
www.rotdoctor.com. If there is any doubt about the ability to properly
accomplish this type of repair, it’s best to consult a professional.
The same chain plate
after cleaning and two coats of epoxy to seal the wood.
The rotten plywood core
has been removed from the area around the cut-out and the nearest bolt hole
using an Allen wrench chucked into an electric drill. Additional material
was removed with a small hooked wire. This chain plate was sufficiently
corroded to warrant replacement. Probing and tap test indicated that
non-repairable core damage was limited to an area within 2-3” of the
cut-out. This portion of the core will need to be replaced with thickened
step is to remove as much of the rotten core as practical. This will also
help determine the extent of the damage/repair required. After cleaning the
rotten wood, a combination of digging with a bent wire (or similar tool) and
vacuum should be used to remove rotten material. The next step is to
stabilize the remaining wood with CDPE. If damage is limited to a small
area, the CDPE can be applied with a syringe and tubing via the cut out and
bolt holes. To help the epoxy flow, heat is judiciously applied with a heat
gun and the boat can be heeled slightly to aid in the flow out board. The
heat will reduce the viscosity of the epoxy, aiding in absorption. Most of
the repair will be the result of capillary action as the remaining plywood
soaks up the epoxy. Fortunately, this area of the deck can be accessed from
below, so if more extensive treatment is required, it is practical to drill
into the laminate from the cabin.
To properly repair the
bolt holes, the holes should be bored over-size, filled with epoxy and
re-drilled (3/8”) after the epoxy sets. Due to the laminated nature of the
deck core, it’s only necessary to bore through the substrate until you reach
the hull liner.
Over-boring the bolt
holes prior to filling with epoxy. Due to the nature of the laminate, a
step-drill was used for this purpose. It is not necessary to drill all the
way through, only to the cabin liner. A standard drill bit may be used for
this purpose. Note the crazing of the gelcoat around the bolt hole as well
as the cracks that go to the cut-out. This is the result of compression and
failure of the deck core in this area.
Masking the area to
contain the epoxy. Rust stains on the liner were cleaned with a combination
of Davis FSR, a stainless wire brush and Scotchbrite.
West System caulk tube
used to force thickened epoxy into the deck. These inexpensive tubes are
purchased empty and the thickened epoxy is then added. It’s important that
a method be used to ensure that the epoxy is forced into filling all voids
in the laminate.
Thickened epoxy applied
to the voids. Heat is judiciously applied to reduce viscosity—use caution
since this quantity of epoxy can generate quite a bit of heat during the
curing process. If in doubt, do not apply heat to this type of repair. The
epoxy is allowed to fill the cut-out to a level just above where the old
plywood was removed. This will need to be cut-out after the repair has
Each chain plate
should be inspected after cleaning for any sign of corrosion or stress
fatigue. The simple rule-of-thumb is if in doubt, replace it. Most damage
severe enough to warrant replacement will be detectable with the naked eye,
but a magnifying glass will go a long way to making an accurate assessment.
Figure 20 shows a good example of a plate that should be discarded. This
plate was installed in the forward lower position. It was exposed to
long-term leaking. It shows signs of exfoliation corrosion around the
forward bolt hole as well as a fatigue stress crack. The corrosion can be
noted visually as well as by dragging a finger nail over the suspect area to
detect surface imperfection. Due to the corrosive environment caused by the
leak, the ability of the plate to withstand stress load is dramatically
reduced. The best way to obtain a replacement chain plate or sub-component
is to call Garhauer directly (909-981-2364) as they sub-contract fabrication
of these fittings for Catalina. You’ll need to provide your hull number and
production year so that the proper drawings can be referenced. Ask to speak
to Doug. The new plate we ordered for our project fit perfectly.
Once the deck has been
repaired or cleaned and sealed as necessary, the next step is to reinstall
the chain plates. Before you apply any sealant, dry fit all of the
components for proper fit. Replace any suspect hardware. Ensure that when
the nuts that secure the bolts will have a minimum of two-three threads
exposed AFTER the lock washer has been tightened down. If the bolt/screw is
too short, it will be difficult to start the nut if sufficient thread isn’t
available. This problem will compound if you are attempting to start a nut
with polysulfide oozing through the assembly. If in doubt, too long is
better than too short. If circumstances permit, the best 316 grade
stainless will likely have to be ordered as most local stores will not stock
this grade of hardware. Several good on-line sources exist. The bolts or
screws that secure the plate to the deck should use locking hardware, either
lock washers or lock nuts. Since there will be plenty of sealant used in
assembly, I’ve found the best combination of hardware is a lock washer with
a standard 3/8 x 16 nut. After the sealant has been cleaned up and dried,
you can finish the end of the bolt/screw with an acorn nut if desired.
Chain plate corrosion
and hairline crack warranting replacement.
Reassembly sequence is
important! If you removed the stainless rod for cleaning and lubrication,
you may have to fit that back into the hull before you put in the chain
plate. To properly orient the rod, the longer threaded portion goes down
with the shorter threaded portion screwing into the pin at the chain plate.
On all but the forward plates, it will be necessary to install the pin
BEFORE the deck bolts, i.e., during reassembly when the plate is covered
with sealant. If you fail to do this, you’ll have to pull a bolt to allow
the pin to slip in place after assembly, ruining the seal around that bolt.
Dry fit the entire assembly before you add the sealant—you’re less likely to
make a messy mistake.
To re-bed, a liberal
coating of sealant should be applied to the top of the plate as well as the
area around the weld. The goal is to fill the hole in the deck from the
bottom up to ensure an adequate seal. Ensure that you’ve removed the
cushions and put down adequate drop cloths or plastic as there will be quite
a bit of sealant that is squeezed out during assembly. It will take an
entire tube of sealant to properly bed all six plates. It’s worth having an
extra on hand to ensure that you don’t run out with half a plate covered in
wet sealant. The plates can be installed by one person if you work
carefully as you can get adequate access through the open port lights. If
you are working alone, it’s easier if you replace the screws with hex head
bolts, since it’s much easier to hold on to a wrench than a screwdriver with
your arm extended through the open port light. It’s also easier to put the
final torque on the nut after the sealant has dried without turning the bolt
if you can use a wrench to hold it in place instead of a screw driver.
To re-install the
plates, the first step after dry assembly and fit check is to apply a thick
bead of sealant to the bolts under the head and fender washer. The standard
washers installed by the factory should be replaced with fender washers to
distribute the load over a greater deck area, minimizing chances of
compression damage. Some sealant should also be applied to the bolt hole
itself. The bolts should then be pressed into place through the deck.
Ensure that the nuts are readily available, and insert the plate from below
with the bolts protruding through the holes. You can then slide a lock
washer into place and hand tighten the nuts while pushing down on the bolt
heads from above. Alternatively, you can build an inexpensive tool to pull
the chain plate into place using a wing nut and a nylon zip tie.
Tool used to pull chain
plate into place with sealant through the deck. The wing nut is loosened to
allow the eye bolt to extend and a nylon zip tie is slipped in place through
the hole in the chain plate. The zip tie is then pulled tight and the wing
nut fastened to pull the plate into place. There is sufficient room to then
insert the bolts from above.
any bedding job, the sealant should be allowed to cure before applying final
torque to the bolts. Clean up the mess below and attach the threaded rod to
the pin in the chain plate. Slip the angle washer into place as well as the
lock nuts, and tighten the nut at the base of the rod hand tight. You
should then re-attach the turn buckle toggle to the chain plate. Hand
tighten the turnbuckle and then return below to tighten the nut at the base
of the rod sufficiently to compress the lock washers—this constitutes “just
snug” which is the proper torque specification. You can then put a couple
of additional turns on the turn buckle to tension the rig. The sealant
should cure with the rig under tension.
There are several good
techniques for masking when bedding deck hardware, but this is complicated
if you have an older bolt with textured deck under the fittings. Newer
boats have no non-skid molded into the deck area around the chain plates.
If bedding over non-skid, the easiest way to clean excess sealant is to
simply allow it to ooze out, and then cut it off with a razor blade after it
has cured. If you are using polysulfide, you can clean things up easily
after it has cured with a small stainless steel brush. Polyurethane and
silicone are a bit more challenging and some effort should be made to remove
excess when wet and masking will definitely help.
Ensure that adequate
time is allowed before you put final tension on the rig and sail the boat.
Polysulfide should be given a minimum of one week to cure during warm
temperatures and at least 14 days during cooler temperatures.
Figures 22 through 34 illustrate chain plate installation steps.
Repaired deck ready for
chain plate installation. Ensure all surfaces are completely clean and
wiped down with acetone or a similar solvent before applying bedding
Positioning the chain
plate “puller” and nylon zip tie used to secure the plate to the eyebolt.
Applying the bedding
compound to the chain plate. The goal is to force the bedding up from the
bottom, so be sure to put plenty at the base of the plate.
the chain plate with the zip tie. This can be done with one hand when
working carefully. Ensure you slide the end of the zip tie up through the
hole so it doesn’t become stuck when you try to pull the plate. [Ed.
note: if the "puller tool" had a hook or an "opened eye" verses a closed
eye-bolt, then the zip tie loop could be closed before the chainplate was
raised into position. Then feed the loop up through the hole and slip
it over the hook.]
Tighten zip tie and eye
bolt to pull plate up to deck.
held in place. Note that pin is fitted at this time since it may not be
possible to slide it past the bolts once they are inserted.
Prepping the bolts with
bedding compound prior to inserting. Note the use of over-sized fender
washers to better spread the bolt load to the deck.
Bolts inserted from
above the deck. Bedding compound is simply allowed to ooze out. It will be
trimmed off with a razor after it has set.
washers and nuts hand tightened, plus one half turn with the wrench. Do not
compress the lock washers until the bedding compound has partially cured.
Coat the end of the tie
rod with Lanicote and thread into place. Note that the top of the rod just
protrudes above the pin. Ensure a minimum of one thread is visible when
Attach the nut to the
base of the tie rod. Ensure that the thick aluminum “washer” is properly
oriented. Assembly is hand tight at this point. It will be tightened to
“just snug” once the bolts holding the plate have received their final
tightening after the bedding has partially cured.
Installed plate and
cover. The excess polysulfide bedding is easily removed with a razor blade
after it has cured.
Interior view of
finished chain plate after excess polysulfide has been cleaned up, post
"Spirit", '88, #563