Canadian Yachting May 2020 - 52

DIY/MAINTENANCE

Deck Repair
By Andrew McDonald

I

t's race night and the breeze is strong. Sails are full, the
rigging is taught and the crew are working hard. Footfalls
hit the deck and bodies move across the cabintop. The
boat is tacked and sails are changed. Sheets are tightened and
maximum downwind speed is reached.
While all of this is happening, the boat is flexing under
tremendous pressures. The stays and chainplates pull at the
edges of the hull, squeezing its shell. As sheets are tightened,
deck hardware is strained. The pounding of the boat through
choppy water acts like a series of jabs in a prizefight. Walking,
stepping, and jumping cause the curved cabin top and decks to
alter their shape slightly.
All of this takes place in a rapidly changing marine environment. The effects of flexing and movement are exacerbated by
the pounding movement of water, and the elements of sun and
rain attacking from above. To make matters worse, we allow the
shells to freeze on land for 5 months of the year, with drastic
changes in moisture content and temperature during this period.
Given all of this, it's no surprise that when the race is done
and sails are being packed away you step back and notice new
spider cracks in the gelcoat, or the feeling of a 'soft' or 'spongy'
spot in the deck as you tread across it. Before the 'how' and 'why'
and 'cost' of this starts to sinks in, lets examine what a 'spongy'
deck really means, and how to address is.
The shell of a fiberglass boat is made of multiple layers of
material, each with different properties - essentially a sandwich
of a core material (often a wood or balsa), surrounded by a alternating layers of fiberglass materials, topped off with a layer of
gelcoat. At some point during the 1960's, wooden boat manufacturing was replaced by fiberglass techniques and processes.
As this evolution took place, much thought was given to high
production output, low production costs, ease of labour, and the
weight and durability of the finished products. In the decades
leading into the 1990's, the boats produced were made with
decks made of balsa core material - a low-cost wood product,
very lightweight, and ideally suited to strengthening large surfaces
and curved shapes. Hundreds, if not thousands, of the boats built
during this period are still being enjoyed today.
In the 1990's, production techniques began to evolve further.
Fibreglassing techniques, and the new scantlings derived from
thinner, more lightweight hull forms propelled the use of epoxies,
carbon fibre and Kevlar. In modern production boats, core materials and 'spongy' decks aren't as much of a concern. But the hundreds of thousands of productions vessels produced by the likes
52

Can adian Ya cht i ng

of C&C, Catalina, CS Yachts, O'Day and Grampian, in the period
between 1970 and 1995 are likely to develop deck core issues.
This is truly what we're discussing - the damage, water intrustion
and subsequent rotting of the core material of the vessel's deck.
A key component of a quality marine survey is a testament to
this fact. A surveyor will spend some time reviewing moisture
meter readings and using a tool to tap at various points on the
hull surface (inside and out), the decks and superstructure. The
moisture meter will indicate if the core material is saturated with
water, and the tapping will indicate (through percussive testing)
if delamination - the separation of the layers of the fiberglass and
core - has occurred. These tests are the best way to determine if
there's cause to panic when the deck sags beneath your weight.
With the stress, strain, environment and use of materials, it's
almost inevitable that the core material becomes wet and rotten
over time. The deck flexes and strains, and the layers that comprise the deck each flex and move at their own rate: The core is
light and highly flexible, the layers of fiberglass surrounding the
core strengthen it, but still allow movement. The gelcoat is thin,
hard and the least flexible of all. Through the layers, deck hardware is attached using machine screws, backing plates with a dab
of caulking. Over time, the caulking shrinks and rots, water permeates and soaks into the core. The water has nowhere to escape,
so it leaches and spreads within the core, soaking a large area.
Time marches on as this water intrusion occurs; in the winter,
the water will freeze and expand, allowing more water to permeate the following spring. As the core soaks, it delaminates from
the surrounding fiberglass layers, losing its strength and changing
the way the pressures are supported when strained. The gelcoat
surface layer may begin to crack in areas of strain. The deck 'gives'
when it is stepped on and feels like a wet sponge underfoot.
There's no cookie-cutter approach to a repair - the method
used will depend on a number of factors, including: the extent
of damage, the hardware adjacent to the deck damage, whether
the deck has smooth or non-skid surfaces, underside deck access,
and the ability to match the repair area to the surrounding
surfaces. That said, a quality repair will follow a general process:
IDENTIFY THE EXTENT OF THE REPAIR
It's tempting to think that the use of a moisture meter is a simple, non-invasive way to test to see if the core is wet or rotten.
The truth is, the use of a moisture meter on fiberglass is a bit
of an art, with varying degrees of success in interpreting the
results. There are many factors that skew results: The varying
MAY 2020



Canadian Yachting May 2020

Table of Contents for the Digital Edition of Canadian Yachting May 2020

At the Helm: Uncharted Waters
Marina Yacht Club: Krates Marina, Keswick
Special Feature: Eye Care - Beware of What You Cannot See
Special Feature: Anchoring - Science, Art and Experience
Power Review: Greenline 33 Hybrid
Sail Review: Beneteau 30.1
The Port Hole: May 2020
DIY/Maintenance: Cored Deck Repair
Crossing the Line: Kjallarinn
Canadian Yachting May 2020 - Intro
Canadian Yachting May 2020 - Cover1
Canadian Yachting May 2020 - Cover2
Canadian Yachting May 2020 - At the Helm: Uncharted Waters
Canadian Yachting May 2020 - 4
Canadian Yachting May 2020 - 5
Canadian Yachting May 2020 - Marina Yacht Club: Krates Marina, Keswick
Canadian Yachting May 2020 - 7
Canadian Yachting May 2020 - 8
Canadian Yachting May 2020 - 9
Canadian Yachting May 2020 - Special Feature: Eye Care - Beware of What You Cannot See
Canadian Yachting May 2020 - 11
Canadian Yachting May 2020 - 12
Canadian Yachting May 2020 - 13
Canadian Yachting May 2020 - 14
Canadian Yachting May 2020 - 15
Canadian Yachting May 2020 - Special Feature: Anchoring - Science, Art and Experience
Canadian Yachting May 2020 - 17
Canadian Yachting May 2020 - 18
Canadian Yachting May 2020 - 19
Canadian Yachting May 2020 - 20
Canadian Yachting May 2020 - Power Review: Greenline 33 Hybrid
Canadian Yachting May 2020 - 22
Canadian Yachting May 2020 - 23
Canadian Yachting May 2020 - 24
Canadian Yachting May 2020 - 25
Canadian Yachting May 2020 - Sail Review: Beneteau 30.1
Canadian Yachting May 2020 - 27
Canadian Yachting May 2020 - 28
Canadian Yachting May 2020 - 29
Canadian Yachting May 2020 - 30
Canadian Yachting May 2020 - The Port Hole: May 2020
Canadian Yachting May 2020 - 32
Canadian Yachting May 2020 - 33
Canadian Yachting May 2020 - 34
Canadian Yachting May 2020 - 35
Canadian Yachting May 2020 - 36
Canadian Yachting May 2020 - 37
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Canadian Yachting May 2020 - 48
Canadian Yachting May 2020 - 49
Canadian Yachting May 2020 - 50
Canadian Yachting May 2020 - 51
Canadian Yachting May 2020 - DIY/Maintenance: Cored Deck Repair
Canadian Yachting May 2020 - 53
Canadian Yachting May 2020 - 54
Canadian Yachting May 2020 - 55
Canadian Yachting May 2020 - 56
Canadian Yachting May 2020 - 57
Canadian Yachting May 2020 - 58
Canadian Yachting May 2020 - 59
Canadian Yachting May 2020 - 60
Canadian Yachting May 2020 - 61
Canadian Yachting May 2020 - Crossing the Line: Kjallarinn
Canadian Yachting May 2020 - Cover3
Canadian Yachting May 2020 - Cover4
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