by Rick Buchanan, Hobie Hotline March/April 2008 (Volume 37, Number 2), pp 14-15
“I’ve got a hole in my boat which needs fixing”… takes on a new meaning when you’ve got a major hole in your boat. What do you do now? Is it repairable? How do you fix it? There is a saying, “If it’s fiberglass, it can be fixed,” which to a certain extent is true. Professional repairs can be expensive, but the good news is that most of the expense is labor. Fiberglass work is not rocket science – you can do the labor yourself and save thousands on a major repair.
The following example shows the damage and subsequent repairs to a Hobie 18 that was probably caused by a heavy tree branch falling onto the boat while it was on a trailer. In fact, both hulls were damaged in the same area, right where the hulls rest on the trailer rollers.
Step 1 – Preparation
Set the boat up in a place where you have easy access to work on it. For this repair, we needed to flip the boat over and set it on saw horses. With a sander/grinder, take off the gel coat around the perimeter to expose underlying damage, which should look lighter in color than undamaged material. The pencil in photo [1] points out the line between the good and the damaged material. Doing this will give you an idea of how large an area needs repair. The damage may be much more extensive than you think.
Step 2 – Remove Damaged Laminate and Feather Back
With a carbide saw blade on a scroll saw, cut out the damage. The gel coat needs to be ground away from the surrounding area in preparation for the repair [2]. The amount of gel coat to be removed depends on the size, shape, and location of the repair area. If the internal repair area involves the foam sandwich area, you may need to cut/grind/sand some of the original material away. This is made easier by using a Dremel tool with an extension cable.
Step 3 – Back up the Repair
Depending on ease of access to make a repair, you have some options on how to make and use a backing material. [3] shows some fiberglass cloth that was laid out on wax paper and saturated with resin. The type of resin used in this repair was vinylester, (a high-grade polyester resin). The excess resin needs to be squeegeed off to allow the cured sheet of fiberglass to be thin and flexible. This flexible sheet can be easily cut with a good pair of scissors and placed inside the hole to provide the “backbone” for the repair [4]. In this repair, screws were used [5] to hold the sheet on the inside of the hull. This was made easier since the porthole was next to the repair area for access. It’s still fairly easy to get a backing material in place without a secondary access hole. A future This Old Hobie will address how to make “blind” repairs like this.
Step 4 – Build Up Outside Laminate
Once the thin sheet of fiberglass is held in place, lay one layer of new fiberglass over it, being careful to leave the screw heads exposed. This will make removing them much easier. When the first layer of glass is cured, remove the screws. After they’re removed, go inside the hull through an opening (in this case a porthole) and place a small piece of tape over each screw hole to stop resin from leaking through from the succeeding layers of glass that you’ll be adding [6]. Once the new fiberglass layers are sufficient for the repair, they need to be sanded to shape. When you reach the point where you have the outside area nearly finished [7], you may want to use some body filler to fair any high/low spots. Evercoat Formula 27 is good for this stage, and is available from West Marine. It’s polyester based and accepts gel coat very easily. [8] shows Formula 27 being faired out using a wallpaper spreader.
Step 5 – Finishing the Outside
Once the fairing in is finished and you are satisfied with the shape of the repair, you can mask off the area for spraying new gel coat [9]. Cover all of your body with shirts, long pants, hat, glasses, filter mask, and vinyl gloves. Breathing gel coat spray is very bad for you, but the process of spraying gel is not that difficult. Thin it 1:1 with Duratec High-Gloss Additive, test on a piece of cardboard to get a feel for it, then catalyze it and go. The spray is very flammable, so do in a well-ventilated area (outside) on a still day (no bugs or dust in the finish). Make sure to run a lot of clear acetone through the sprayer when you’re finished to clean it out. To get the hardest finish, you’ll need to spray the gel after with PVA (polyvinyl acetate–mold release wax –available at West Marine or on-line) on the patch after the gel has partially cured. PVA is water soluble so you can wash it off when everything’s hard. Once the gel coat is cured, you will most likely need to sand a small amount of “orange peel” with 320/400/600/800/1000 grit wet or dry sand paper to get it smooth. Finish with a buffer/polisher and a good quality rubbing compound such as 3M Super Duty [10].
Step 6 – Build the Inside Laminate
Once the outside repair is finished [11], flip the boat right side up on the saw horses and begin the internal work. This starts with measuring and cutting fiberglass material large enough to overlap the original hole by about 1½”–2″ over the entire perimeter. The type of glass to use will vary from one repair to another. For a good-sized hole like this, a “dual bias” type glass is recommended. The glass used here is called “Nytex” [12]. It’s a layers of fiberglass mat sewn together with two layers of unidirectional fiberglass (not woven like a glass cloth).
Once the layer of dual bias has cured, cut and fit some pieces of foam to replace what was removed. The foam used here is Divinicell. It measures 3/8″ thick and is green or grey in color [13]. After getting the foam the right shape you can glue it in place with some catalyzed resin thickened with aerosil or fumed silica. The pieces of foam will most likely need to be pressed and held in place while the resin cures. Here we used some scuba diving weights [14].
When the resin holding the foam has cured, cut and fit another layer of the dual-bias fiberglass, like in [12], setting it in place over the entire repair area. Wet it out with catalyzed resin using a plastic squeegee to spread the resin. The resin used in this step should be a finish coat that dries tack-free.
Time to go sailing!
