Modern Epoxy resins have become commonplace in the shops of both amateur and proffesional wooden boat restorers. Properly used, epoxies can save a considerable ammount of time and money in the restoration or repair of a boat. Improperly used, however, they can be a hazard both to the user and to the boat they are being used on.
Types of Epoxies-
There are several different types of epoxy availible today, Mainly Resins (liquid) and Putties. Epoxies are multiple part, meaning that in order to use them you must mix two or more components together. When the parts are mixed, a chemical reaction occors, which results in the hardening of the epoxy. Different types are suitable for different jobs-
Resins- Liquid resins are the most versatile of the types. Consistencies
vary from watery to more like honey, depending on the brand and intended
useage. Liquids can be used as they are, or mixed with a varity of fillers
to acheive different working, curing, or strength charachteristics. Used
plain, they can be used as glue, to 'wet out' fiberglass cloth, seal plywood,
and more. Mixed with appropriate fillers, they can become various types
of fillers, formulated for strenght, sandability, or a combination of the
two. Liquid resins are mixed with different hardners to acheive different
curing results, as an example to give a longer working life before the resin
cures or to acheive a super clear end result for varnishing. Resins are
mixed with hardners by ratio, some of the more common being 3-1 and 5-1.
Examples of this type of epoxy include the brand names West Systems, System
3, and Epiglass. All of the following techniques were developed with resins
in mind.
Putties-Epoxy putties have quite a few good uses in restoration
as well. Most putties on the market today are formulated mainly with strength
and/or a fast cure time in mind. Different brands come in different consistencies,
that range from peanut butter to play dough. The thicker formulas are often
workable by hand, which is ideal for quick repairs. Most putties can be
used anyplace you would use thickened resins.
Essential Tools- You need to have a few basic tools on hand when
you are going to work with resins. Epoxy hardners are strong sensitizers,
so you should protect your skin from contact with both the resin and the
hardners. Use a pair of disposable latex or vinyl gloves. You will want
to have several mixing pots, the best ones are flexible plastic. A few sturdy
mixing sticks, disposeable brushes, and a roll of masking tape will also
come in handy. Uncured epoxy can be cleaned up with a solvent made specificly
for the purpose (most epoxy manufacturers have their own) or laquer thinner.
You also need a means of accuratly measuring the epoxy and harnder, if you
are on a tight budget any graduated cups will do, but it is much easier
to buy the dispenser pumps made by the resin manufacturers specifically
for that purpose.
Mixing Epoxy- Before you can use epoxy resin, you have to mix
it in the appropriate ratio. The ratios used vary from manufacturer to manufacturer,
so consult the information that came with the epoxy. Measure out the propper
ammount of resin into a container, leaving room for the harnder. Measure
the harner in a SEPERATE container, (1) then add it to the resin (2). Mix
the epoxy thouroughly, but SLOWLY(3).Mixing too fast will allow bubles to
get trapped in the epoxy, which will get in your way later.
Fillers- The type of filler that you use will depend on what
you want the epoxy to do. There are fillers availible for making adhesives,
for high strength structural filling, and easy sanding fairing fillers.
Consult the technical information for the epoxy manufacturer to determine
which is correct for your use. Add the filler AFTER the epoxy resin has
already been thouroughly mixed(1). Pour the filler into the epoxy, and stir
it thouroughly (2). Add more or less filler to acheive the desired thickness,
but do not exceed the manufactureers reccomended maximums.
Filling a small hole, gap, crack, or void-
Areas that have small holes, gaps, cracks or voids to be filled should
be delt with as follows- (1) Isolate the repair area. Find the extent of
the damage. (2) Gouge any damaged or rotten wood out of the repair area,
using a chisel, wire wheel, ect. This will both remove any weak material
and also make room for the epoxy and filler mixture.Be sure, especially
when you are dealing with rotten wood, that you go all of way down to sound
new wood, or your repair will be weak. Mix the epoxy and appropriate filler,
following steps above. You will generally use a HIGH STRENGTH filler for
this type of work. (3) apply the resin/filler mixture to the repair, and
work it in place with a putty knife or resin spreader. Allow ample cure
time, then sand any tool marks or imperfections. The repair is now complete!
Repairing bigger areas-
Bigger repair areas can't be filled with epoxy and filler alone, both for reasons of the high cost of the epoxy and also the weight. In a case like this, it is best to do the following- (1) Isolate the repair area. (2) Cut the ends of the area at an angle. this provides ample area for the epoxy to ahhere to. Make sure you go beyond the damaged wood. When both sides of the area to be repaired have been properly cut, measure the size of the hole and cut a "dutchman", or a block of wood that fits into the hole loosly. You do not wat a perfect fit, or else there will not be room for the epoxy. (3) Put the dutchman in place, using a generous ammount of epoxy at both ends.
Repairing rot damage near a bolt hole-
Water leaking in alongside a bolt hole (as in a stem) will often lead to rot damage along all or part of the bolt hole (1). To repair it, you need to (2) remove the rotten wood with a chisel. (3) Fill the hole completely with epoxy and a high strenght filler mixture, allow it ample time to cure, and then re-drill the hole for the bolt.
Laminating with epoxy-
You will often need to laminate two or more peices of wood together in order to get a peice of wood of a desired thicknss. Epoxy makes an ideal adhesive for this purpose. Make sure that the parts to be joined are clean and dry. Brush an ample ammount of either unthickened epoxy or epoxy with a small ammount of adhesive filler in it on both parts to be joined. Clamp the parts together securely, and keep them clamped until the epoxy has cured. Properly done, this is as strong as a single piece of wood.
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