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Repairing a Sea-Kayak!
Or "Who put that rock there!"
Kayak repair is to many a black art. This can be for many reasons:-
The basic repairs consist of a bit of carpet tape and crossed fingers. This is fine for a quick repair in a trip but not good long term. Eventually running up beaches and lots of seal launches take their toll on the keel of a kayak and repairs are needed. Or worse, bumping a rock can have a disastrous effect on the side of a sea kayak. Ever wondered why your kayak leaks in the compartments when no one else has that problem? Could be the deck fittings, bulkhead or a small hole, so why not fix it!
It must be remembered that resins, gelcoat, catalyst and fibreglass are not designed to be swallowed, placed in open cuts or areas of thin skin tissue like eyes or more private areas. So it can be very advisable to wear rubber gloves, goggles or a face mask when working with these items. Ventilation is a must as the fumes can be very uncomfortable and in some cases fatal! AND it IS all very flammable, so those people who are unfortunate to feel they must smoke restrain yourselves whilst in the work area!
Repairs take the following format:-
Assess the Damage
Always worse on a new boat! No one wants to be the first to put a blemish on their pride and joy. But one that has many battle scars, well one more will not hurt. Cracks or splits are much simpler than full blooded holes of course. A split or crack may just be a case of painting a bit of resin in the gap whilst a hole may require some assistance to hold the shape of the boat.
Like painting, the surface must be firm to hold the new materials. There is no point in putting lots of fibreglass onto loose repairs from before. Although it may be unfortunate, or seem extra work, you are best getting rid of all the old repairs. Your shoulder will thank you for it when you put the kayak on the roof! Sand/groove ALL the area that GRP is to be bonding with so it will not fall off easily. It MUST be dry. Fibreglass absorbs water so you must give it time to dry out! Do not waste your time if the clouds are looming in the garden, head for the garage or get the tent out.
Do you wish to make it look like it never got hurt or simply slap on some fixes. The materials include fibreglass, Resin, Catalyst and a brush as a minimum. Additional items may be Pigment, Gelcoat, Tissue, Woven Roven, Acetone and Powder.
This has a time factor! It is based on temperature and the amount of resin / catalyst being used. The minimum temperature you should be working in is 16C / 62F. If it is colder than this you may want to add more catalyst, but this will make the repair more brittle. Add Catalyst at 1% (10cc per KG resin) to give a working time of about 25 – 30 minutes. The chemical reaction creates heat so if the resin is left as a large quantity for long it will go off quicker. First stipple the resin onto the fibreglass on a board or similar then paint a small amount onto the kayak itself. This will make sure all will bond well. Place the fibreglass onto the kayak and again use the brush to stipple the area. This is to remove all air and let the resin fully bond with the glass. Transparent repairs are easier to see as the materials go clear. If you wish you can add a piece of tissue to the top layer for ascetics.
Wash Out Brushes, dispose of excess safely
Once all repairs have been done get the brush and any other tools you wish to reuse in the Acetone as quickly as possible! Get every drop of the resin out of the brush. Any tubs containing waste resin allow to go solid – make sure they do not create a fire hazard- this makes them easier to dispose of. DO NOT POUR WASTE ACETONE OR RESIN DOWN THE SINK!!! There are many ways of disposing of the chemicals. If left open to the air acetone will evaporate so seal the lid. Old acetone can be reused as the first rinse of your brush. It is not advisable to pour chemicals over the neighbors fence either.
Once all is hard check the work for spikes of glass or loose edges. It may need a bit of sandpaper over the top. What does make things look nice is a bit of sanding followed by a gelcoat mixture to really smooth things down.
Get the kayak back on the water!!!!!!
Seems obvious. The kayak has been off the water far too long already so get out there and enjoy it.
Glossary of Terms
Little seen today, thank goodness! MUST be added to resin before catalyst and mixed in thoroughly! If not it IS explosive. So if you are unfortunate enough to get some resin that does not have the PA (pre-accelerated) suffix ASK! If it does not have accelerator in it already it will not cure (go hard) no matter how much catalyst you use. Add accelerator, mix in very well, allow to settle and add catalyst.
Used to wash out brushes and tools as it dissolves resins. Also dissolves lots of other plastics so best kept in a glass jar! Often called Propanone. Nail varnish is a very diluted form of acetone. WILL cause dermatitis (skin disorder) if left in contact for prolonged periods.
A simple but easily forgotten item. Used to "paint" gelcoat onto a mould and "stipple" the resin into the matting.
Best seen in translucent resins as it is black in colour. Often combined with Kevlar to give good strength, light weight and stiffness, look for the black & yellow checker pattern. Beyond the normal amateur for use. It delaminates easily. Very expensive.
Possibly the most dangerous part of the whole system! Use with extreme caution! Can dissolve skin! Sometimes called hardener. Used to start a chemical reaction in resin or gelcoat. Add 1% to resin or 2% to gelcoat to give approx. 25 – 30 minutes working time. NOTE: Catalyst and Accelerator mixed together are explosive!
A form of small fibres (approx. 50mm) that have been glued together in a random direction with a bonding agent to form a cloth-like substance. Can be used in all aspects of repair, often used for deck and seat manufacture where appearance is not important. Very rigid when bonded with resin. Cheapest form of fibreglass.
Actually a polyester fabric instead of glass. Only to be used for the hull as it is very flexible, although very strong. Very sharp knife required. More expensive then Chopped Strand Mat or Woven Roving.
The generic name used for a material made from molten glass. When woven into various methods (Chopped Strands, Woven Roving or Tissue) it is able to be bonded with a resin to create the kayaks we paddle today. Often used, incorrectly, when referring to Diolen, Kevlar and Carbon-Fibre materials.
Fluff Roller
Looks very similar to the rollers used in painting the walls. Used during kayak manufacture to 'paint' resin. A roller allows the resin to quickly be applied to large areas of fibreglass matting.
The waterproofer! Very thick resin used on the first layer (outside) of a kayak during manufacture. Often used in conjunction with pigment. Requires Catalyst to make it go hard but will eventually become unusable if left. The side in contact with the air remains sticky allowing the fibreglass layer to bond with it. Contains no wax so the wax applied to a mould is effectively bonded to the surface of the gelcoat. If using for external repairs you must seal the Gelcoat from the air, esle it will remain sticky. It is also possible to add a small amount of resin for the repair to seal the gelcoat or include a wax in styrene additive.
Glass Reinforced Plastic. The generic name given to a laminate of resin and fibreglass. Was the most common way kayaks were manufactured but is now superceded by Rotary Molded Plastics (Plastic Pigs/Tupperware) designs. Still the most common method used for sea-kayaks.
Best seen in translucent resins as it is yellow in colour. As it is difficult to cut it is not often used by amateurs. Very good weight/strength ratio. Except for its colour it is similar in appearance to Woven Roving. Only Carbon-Fibre is more expensive.
A sandwich of resin and fibreglass. Often has a layer of gelcoat that forms a shiny protective skin.
Liquid Wax
Gelcoat contains no wax. If painted onto a kayak it will always remain sticky. It is possible to add liquid wax (prior to catalyst) so when it is curing the wax will float to the top of the gel and seal it from the air. This then allows it to dry correctly. Another method is to add a bit of resin to the mixture instead of wax.
Paddle Roller
Aluminum roller used to squeeze air from the laminate.
Used to create a colour effect on the resin or gelcoat. Add 5% in gelcoat for solid colours, translucents do not usually use pigment in the gelcoat. For resins use 2 ½% for solid colours, translucent colours only need 1% max usually ¼%. Sadly different colours cure faster than others. Basic rule, the lighter the colour the quicker it cures. Black takes forever to go hard. Yellow is often difficult to work as it streaks easily.
Often a form of talc. Used with resin to form a bulky paste. Often the stuff used to seal the cockpit seat to the deck or to fill the ends prior to drilling the holes for the toggles. Much cheaper to use than resin alone.
Release PVA
Polyvinyl Alcohol. Used on new moulds to break it in. Not required on moulds that have seen several kayaks been made. MUST be followed by "ordinary" release wax.
Used to polish the surface of a mould prior to applying gelcoat. It is essential that the surface is completely waxed and dry, else the kayak can stick to the mould. Most waxes no longer require PVA prior to use. Check this is the case!
Thinner than gelcoat and is used to bond the fibreglass strands to the gelcoat and themselves to produce a laminate. Sadly not actually waterproof! Comes in many varieties always ask for marine quality. Most resins today are Pre-Accelerated. This means only Catalyst is required to make it harden. Resin will eventually go hard if left in the air.
Stippling is the direction you move the brush when working with resin. Resin or Gelcoat must not be brushed onto fibreglass up & down or left to right (like paint). Instead the brush is lifted off the material and placed back down again. This action is called stippling. Gelcoat is painted onto the mould or repair, like paint.
Very thin form of Chopped Strand Mat. For its weight it absorbs a large amount of resin. Very good for placing over Chopped Strand Mat to make a smoother repair.
Very long lengths of glass thread that are woven in a criss-cross pattern to form a cloth. Often used as the last layer of the laminate on the hull of a kayak where its smoother surface and flexible nature can be fully utilised. It does not soak up as much resin as Chopped Strand Mat so can be used to make kayaks lighter or stronger. Almost the cheapest form of fibreglass.