Getting started

Safety-PPE for fiberglass repair

Tools for a fiberglass repair

Fiberglass repair kits and materials



So, if you are new to this, you should have read the Getting started sections and made a list of tools, materials and safety gear you will need to set yourself up for a fiberglass canoe repair.

Ok, so a fiberglass canoe hull thickness is generally not very thick, so you will need to be very careful when using the sander/grinder for this fiberglass repair, but first get yourself organised.

To start our repair first make sure our fiberglass canoe is in a warm spot and out of any cool or cold drafts, you could put the canoe on a set of saw horses as this should give a good working height, prepsol down all around the crack at least 300mm with a clean cotton rag to make clean and let dry.

Now depending on your finish and if you are looking for a great finish, it will be fast and much better to use a 2 pac spray finish, these can be tinted to your requirements and used when your ready for your fiberglass canoe repair, they can be purchased from paint places that supply the automotive and paint trades.

Some marine centers may also sell them so give them a call before jumping in your set of wheels as this will save you time and $ in case they do not have them.

So in order to get a good colour match you will need to polish a area away from your damaged area and take a colour card to the canoe or if your wanting the best match if possible take the canoe to your nearest paint centre where they will colour match it for you, but this would be the last resort.

The other more practical way is by using a clean sharp chisel bevel side down and working outward from the crack take out roughly a 4 mm (3/16th) by say 32mm (11/4″) round type flat section with the canoes colour on, take that to your paint place where they will polish it up if needed, then tint the 2pac up for you.

You could of course use gel coat or gel coat paste, but this is not going to be good for the uninitiated unless we just have a scratch or chips in the gelcoat but when we are doing a fiberglass repair like this unless the repair is only quite small and the reason is this, for gelcoat to work properly it needs a little thickness so you will need to grind out some of your laminate (that may make your repair weaker) and paying attention to where it comes in contact with the original gelcoat edge on the canoe.

If we are using Gelcoat repair paste it will dry hard and usually with out a tacky surface which makes sanding a breeze, but if we are using gelcoat in its liquid form it will be tacky when dry (that is its nature) to get out of this you will need to spray or put some PVA, or a plastic film to seal the surface as it dries.

You then wash off the PVA or peel off the plastic film in order for it to be sandable.

Another way we could add a few drops or more of wax in styrene as we mix up the gelcoat, this will make the gelcoat not tacky when dry making sanding better, once the gelcoat is in and we start to sand this is where (if you are not experience in doing this kind of work) you run a big risk of sanding through showing up the laminate underneath because it was not deep enough to take gelcoat or you may see through the gelcoat after you cut and polished it.

This is why the 2k or 2pac system is faster and better unless you are a traditionalist or the repair is on a new boat etc. and most pros (unless the canoe is new) would opt for a 2pac finish anyway as gelcoat can be time consuming to work with.

Ok lets now get back on track, with a marker pen (white board maker is good) or pencil mark around the fiberglass crack at least 50mm (2″) all around and make sure the ends are round and 75mm (3″) either end and don’t bring to a point.

Using your grinder (in this case with 24 grit disc) VERY CAREFULLY and not applying much pressure to the grinder, grind out up to the outside line where this is your feather edge, the crack is your deepest part and be careful not grind right through your hull thickness at this point.

The end result should be a even hollow dish like appearance with little or no humps or deep hollows through out this area, now do not touch any part of this with your fingers or hands or get it contaminated.

Using a clean no lint rag (white cotton) or compressed air, dust around the outside and get rid of any dust near your repair.

Cut your first layer of mat (if you have not done so already) about 25mm (1″) in width and past the length of the fiberglass crack either end by around 20mm, now do the same for your second piece making sure it is wider and a bit longer to overlap the first e.g 50mm (2″) in width.

Do the same with the third or fourth piece of mat, the idea here is to fill the hollow with overlapping layers of fiberglass mat with the last layer hitting near the feather edge (where color meets the raw sanded or ground fiberglass.

You should at least have one layer of a heavier grade mat layered in between as fiberglass repair kits usually come with only a 450grm csm mat and not 600 grm csm, but this is not totally necessary for a canoe repair, now put these in order with the 25mm width mat first (as this layer is the first to go down) with the widest one last.

Mix up a small test batch of resin with catalyst (hardener) according to the instructions on the tin and watch the time it starts to gel (approx 20mins) if you are happy with the time (or according to the instructions in your kit) you can now start to mix up your real batch of resin and mix well, making sure you stir from the outside to the inside of the container and visa versa so that the resin and catalyst is mixed well.

With gloves on (optional), lay a wet layer of resin over your damaged area and lay down your first piece of matting having the crack in centre of mat and dampen down making sure that each end overlaps and interweaves to the next following piece if your fiberglass crack is long, be quick and not chat, wet out this piece and lightly roll over it to remove any air bubbles or work it with your brush.

Your mixed resin should still be fine and ready for the next layer overlapping the first evenly as possible, making sure you do not match up with your ends as you need to stagger these throughout, except the very ends of the crack, just overlap the other.

Quickly working, wet this layer out and working your brush lightly from side to side even out the layer or use a paddle roller to easily and quickly lightly work it level, If time and resin is ok lay down your third or last layer (you may need to mix up a new batch of resin to finish the job depending on the size or if the resin in your tin has started to gel, use a new tin and wash out your brush with some acetone to keep from gelling up) and continue if need be.

When the fiberglass repair work is done, wash out your paddle roller (if you are using a roller) and your brush and let your job set up till hard.

Now if any crack is showing on the inside of the fiberglass canoe this can be ground out till you meet up with the new outer layer and finished off like the outside, the last layer should be bigger than the outside repaired area.

Next using your grinder with the same disc on very carefully run over the glassed area to level off any high areas and any hairy glass fibres that may be there, you can use your hand carefully to feel for any high spots and can be a good idea to use gloves when doing this as fiberglass splinters can be sharp.

Now using a flexible plastic ruler on its flat or similar and starting from one end bend it to the fiberglass canoes curve, slowly bring it through, the fiberglass repair should be just level or just under, any high spot can be sanded down.

Prepsol or clean off the area wearing gloves not to contaminate this area and let dry well, mix up your filler (a test mix is good first) and trowel it through using a flexible spatula or a flexible plastic filler card from one end to the other evenly and slightly raised if posible, let dry hard before trying to sand.

Now using your cork/rubber block and 80 grit sandpaper and following the fiberglass canoes curve (unless you are on a flat section) knock off all the high filler, now using a 150 grit knock out the scratches of the 80 grit and continue to level.

At this point if there is any hollows or pin holes, prepsol this down, let air out (dry) and fill with some filler before sanding any more.

When dry, continue to lightly sand (don’t worry if your starting to lightly sand into your colour) now feel with your hand it should marry into the outer colour pretty evenly, any light high spot can be lightly sanded to marry in.

With your 240 grit take out the 150 grit scratches and dull off the surrounding colour it should now feel nice and even like if you are feeling any other part of the canoe, now if your happy with it, dust all around and wipe over all the areas with prepsol or similar with a clean cotton rag.

When dry, our fiberglass repair can now be prepared for applying the primer, you will need a roll of masking tape and newspaper or you can buy the masking tape already stuck to a brown paper roll which makes it pretty easy to paper up.

Now starting at least 75mm (3″) around your fiberglass repair, wipe lightly over and up to to the masking tape with prepsol and let dry well.

Shake up your can of primer and if you have not used a spray can before have a little play on some scrap tin or something similar till your confident, make sure like all things to read the spray cans instructions before use and use in a ventilated area.

Spray a light even coat of primer over the repair but do not go anywhere near to the masking tape, just keep it just over the repaired sanded area, do a second coat heavier this time, let set and a last one should be the same but don’t do it too heavier as you will get runs and feather all coats to the outer but covering the repaired sanded area.

Undo all paper and masking tape and ditch it, when primer is all hard you can lightly sand all over with 240 grit followed by 320 grit and 600 grit into the coloured area, don’t be too concerned if you can lightly see through the primer in some areas.

Wash down with some light soapy water and let dry, now mask and paper up the same as before but leaving more area from the primer to the outer mask which has been scuffed with 600 grit wet and dry before hand.

Lightly prepsol down and let dry, shake and mix up you top coat as per instructions on the can and do a test spray patten somewhere to see how it looks and get an idea of usage.

Now lightly evenly spray your first coat over the primer, let tack off and follow another coat through overlapping the first and heavier, let tack off, now give a last coat which should be beautifully glossy and solid colour with little over spray anywhere near the masking tape and let dry, just before hard dry remove the paper and masking tape gently taking it off away from your sprayed area, let all now dry hard.

If you have a little overspray you can use some 1200 grit wetndry and some light soapy water followed by 2000 grit wipe down then polish in when dry, make sure its done a few days or a week after as the 2pac may not gloss well when cut and polished into the surrounding colour depending when you did it e.g winter.

So we hope that this fiberglass canoe repair will put you back onto the water and happily canoeing.



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