Composite Kayak Repair - Fixing the Whisky after my Charlston Rough Water Classes

While at the East Coast Paddlesports & Outdoor Festival this year I took a few classes offered through Sea Kayak Carolina. These were rough water courses from Kayak Waveology and a surf course with Dale Williams. I had a great time but my Whisky 16 did not handle it as well.

In a review of the Whisky 16 I defended the light lay up of the fiberglass. It actually gives a little flex and can prevent sever damage when you have a close call among the rocks. It has a hex core bottom that gives the rigidness the hull needs. I love the design of the kayak but it has a flaw.

You will see in the picture that the fiberglass flexed enough to crack the gelcoat and the resin in the glassing. This happened when the kayak slapped the water after I had to shot over a 4 foot wave that was about to break outside the zone we were surfing, basically breaking on top of us. So, upon inspection I noticed two things that contributed to the cracking. First, it cracked just past the hex core where it does not cover the full length of the hull. Second, the fiberglass in the hull of the front hatch does not appear to be fully impregnated with resin.

So, I found out that the glass hull cracked and now had flex in it by the cracking of the gelcoat. 

 You can see that it really does not stand out much until you zoom in. I actually did not notice it until we got home and we were unloading the kayaks.

You can see by the way it is cracked and the lack of scratches or other signs of impact that this was caused by stress.

It is actually an easy thing to repair since there are no holes in the hull. The area just needs some resin in the stressed area and some added glass for reinforcement. Then a gelcoat repair.

First thing you need to do is prep the area. I start with a 230 grit sandpaper to clean and rough the area then I clean out the dust and wipe the area down with Acetone.

You want the surface to be well cleaned for the resin to adhere to the surface. The sanding will also open the original fiberglass the was not well impregnated with resin. This will allow you to force additional resin into the original glass.

 Next thing is to get your fiberglass and cut it to the size you need for the project. I use a 6 ounce fiberglass instead of cross layering sheets of 3 ounce. This is a repair and not a structural build.

Your glass should cover the area of damage and continue a couple inches around the damaged area. The kayak had stress areas along the sides as well as the large area on the bottom so, I cut a piece big enough to cover the sides as well as the bottom cracking.

Next I spread the resin on the area that is cracked and force it into the cracks. this will fill in any gaps in the original glass and fill in areas that were not fully impregnated originally. This will created a stronger bond with the new fiberglass.

Then you lay the new glass onto the area and work it into the resin. Then you start adding more resin into the new glass and forcing it in with a squeegee. You need to use enough resin to fully saturate the fiberglass.






On this repair I added some additional glass on the bottom where it was the weakest form the cracking. This will add additional support for the area and give it added strength.

As you work the resin into the glass you will also work out the air bubbles and press the fiberglass flat and into any corners. It should lay as smoothly as possible and have full contact to the area of coverage.

In the photo below you can see the repair with the double layer of fiberglass on the bottom and a couple additional patch areas on the  left side.


Once you have the fiberglass full of resin and smoothed out you need to let it cure. I use an epoxy resin that cures in about 6 hours at 80 degrees fahrenheit. I generally let it cure over night to be on the safe side. The resign can nor over cure but it can be an issue to try and sand it before it has cured enough.




Now you will sand the area you just patched. Not to much. You do not want to sand away the fiberglass you have just applied. You just want to sand down the edges where the fiberglass willbe rough and rough up the resin on the top of the glass to add a finishing coat.

  After the sanding to smooth the edges you will want to clean out the dust. Then once again clean the area with acetone to remove any grime and grease left by your hands.






After you have the surface sanded and cleaned you will notice the sharp hard edges of the fiberglass. Also the surface will have an uneven texture to it. To get a smoother surface you will add some additional resin around the edges with a paint brush. then you can brush on an additional  layer on the surface to get things relatively smooth. Since this is the inside of the hatch I do not get overly particular with it. I just do not want any rough edges to abraid my dry bags when I slide them in and out.

Now you need to let the resin cure. After it cures it should be fairly smooth without sharp edges. You and apply more resin as needed.







Now, it is time to repair the gelcoat. This is where you get particular about the sanding and smoothness. First, you have to do some prep work by removing the cracked gelcoat and and prep the surface. I use a polyester gelcoat paste for this type of repair. Also I don't have the area to use a sprayer and painting the gelcoat on with a brush can be problematic. The paste has issues of itself. You have to be really careful about air bubbles and after the first sanding you may find that you need to apply paste again to fill air bubbles.

first thing you want to do is chip off any loose cracked gelcoat and open any cracks. This will allow you to have an area to apply the new gelcoat and it will be attached to gelcoat that is tightly bonded to the fiberglass.






Make sure you do not dig into the fiberglass base. You do not want to compromise the strength of the glass.  After you have chipped out all the loose gelcoat and scraped open the cracks you will need to sand the surface. I use a 300 grit sandpaper. Then thoroughly clean the area with acetone.




Now you mix and apply your gel paste. My hull is white but not a true white. I do not bother trying to match the color. I pigment my gelcoat with a true white. This allows me to inspect the repaired area over time but you have to look closely to notice the difference.

When you spread the paste on try to keep it smooth to prevent air bubbles and do not over work it. You are not trying to get it even with the original gelcoat. This is done during the sanding.

 Then you let it cure. Some people like to let it cure to a firm state but, not fully cured. The idea is it is easier to do the initial sanding. I like to let it cure for at least 12 hours so,I generally leave it overnight.

I find it is less likely that I will oversand the patched areas if the gelcoat has fully cured.

Next is the initial sanding.

I start with a 300 grit sandpaper and sand the patched area until the are almost flush with the original surface. I sand in a circular motion trying to stay on the patched area and following the kayaks contours.

The sanding block I use is cut from a piece of closed cell structural foam.

You can see in the photos that the sanding gets almost flush but not quite. The reason for this is to allow for the wet sanding that will go through 3 grades of grit to get a smooth finish.

The finish will be the most time consuming depending on how much of a smooth finish you want.

For the wet sanding I use sanding sponges I get from HomeDepot.

I have a 320 a 400 and a 600. I start with the 320 and sand the patched area pretty much flush then I move to the 400. When it is fairly smooth to the touch I move to the 600 to finish the surface.

The surface will still have a dull look to it. Next I use a fiberglass polish to start giving it a little shine.

Take you time with the wetsanding and polishing. This will be what defines your work. This is the surface that people see and notice. It will also be the deciding factor of how much you can charge if you decide to do the repairs for others.  In my area there are very few choices of places to go for composite boat repairs.

 Polishing can be done by hand or with and electric car buffer. I chose to do this one by hand because it is my boat and I was not concerned about a high gloss shine. If you want a high gloss shine use an electric buffer and go over the area a couple time with the polish the add a couple coats of boat wax.

 Give it a good wipe down and a coat of wax.

I use a spray on boat wax. If you want a high gloss shine use paste wax and a power buffer.

This is the finished surface. If not for the light color difference you would not know a repair had been done.

This should help you get started on your own repairs. Or, if you are in the Washington Metro Area you can look me up. Reasonable rates but I have a real job so repairs will take atleast a week.