Gel Coat Repair and Deck Sanding

[rctestflight]

In June 2022 I started restoring a 1972 13-footer, I now have these questions:

Q1: what should be done about a previous repair in which fiberglass was applied on top of the gel coat?

Q2: other than sand blasting, what is the best way to remove old paint from the deck non-skid surface?

Q3: how was the deck held down with screws around its perimeter (which I infer was the method from the appearance)?

Q4: what was the deck made from?

I know some of the decks of older Boston Whaler boats are plywood. This deck is not flat.

Any help would be greatly appreciated.

[Moderator's note: if you attach multiple images to a post, the images need to be identified by figure numbers and have captions that indicate was is being illustrated. I have created figure numbers and captions for the three images you uploaded.]

Fig. 1. A prior repair, deemed substandard.

Fig1a.jpg (44.08 KiB) Viewed 1851 times

Fig. 2. More substandard prior repair work.

Fig2a.jpg (31.37 KiB) Viewed 1851 times

Fig. 3. Impressions of screw heads in the molded cockpit deck.

Fig3a.jpg (22.67 KiB) Viewed 1851 times

[Phil T]

The impressions of screws in the deck are not screws. The are marks from the mold.

There are two skins of fiberglass bonded together and structural foam injected in between. There are no screws.

[jimh]

Q1: what should be done about a previous repair in which fiberglass was applied on top of the gel coat?

If you are unsatisfied with a prior repair to a fiberglass boat, you can grind off the prior repair and try again.

Q2: other than sand blasting, what is the best way to remove old paint from the deck non-skid surface?

Soda blasting.

Q3: how was the deck held down with screws around its perimeter (which I infer was the method from the appearance)?

The appearance of screw heads is an artifact of the plug which was used to make the mold which was used to make the hull. There are no screws in the actual hull. The screws were in the plug.

Fiberglass boats are generally made in female contact molds. The molds are created from a plug. The plug is usually the prototype hull or a mock-up of a hull structure made just to create the mold that will make the production hull.

That Boston Whaler left exposed screw heads in the plug for the early 13-foot hulls is an example of the practical approach of the designer, Dick Fisher. Dick Fisher was also a bit whimsical, and he may have intentionally left those screw impressions in the finished hull just to confuse other boat builders about how the boat was made, just as he has apparently confused you.

Q4: what was the deck made from?

The deck was molded using the typical laminated fiberglass methods. The deck was created in a female contact mold. The gel coat layer was sprayed into the mold to a thickness of about 0.020-inch. Polyester laminating resin was then sprayed into the mold, often with chopped strands of fabric with some areas also getting fabric cloth and in some special areas wood.

I know some of the decks of older Boston Whaler boats are plywood.

There are no old Boston Whaler boats with plywood decks. In some older Boston Whaler boats the forward deck could have an optional wood platform that raised the deck and provided a flat surface to allow an angler to stand more easily.

[jimh]

For general advice on making repairs to the gel coat and laminates of a Boston Whaler boat, please read these articles:

Repairing Hull Damage the Whaler Way
https://continuouswave.com/whaler/refer ... epair.html

Boston Whaler Factory Instruction Sheet for Hull Patch Kits
https://continuouswave.com/whaler/refer ... tions.html

Minor Repairs with Epoxy Resin
https://continuouswave.com/maintenance-logs/epoxy/

[jimh]

Based on the impression taken from Figure 1 and Figure 2 above, the present condition of the boat has paint applied on old repairs which were applied on the gel coat layer.

With the original gel coat layer of the hull and deck now concealed by paint and substandard repairs, I doubt there is much opportunity to restore the boat to its original gel coat layer without very substantial work. If your purpose in acquiring this boat was to have a long and tedious restoration project, you have the purchased a suitable boat.

There is really no mandate that all old Boston Whaler boats must be restored to factory-new condition and appearance. A hull with repairs that protect the hull integrity and maintain the hull strength, covered by a nice coat of paint, are completely suitable for a boat whose purpose is to be operated as a small skiff and enjoyed for that use.

[rctestflight]

Thanks for the help. The Continuous Wave reference material is great. Wish I would have known about that earlier.

Soda blasting the deck may be a bit out of reach for me.

Q5: can paint remover and a wire brush be used to remove paint that has been applied atop gel coat resn?

[rctestflight]

As I was opening up the cracks in the original gel coat with my Dremel tool, some of the thicker areas were chipping out. See a demonstration that records this behavior at

https://youtu.be/hAX1mqwJnMM

Q6: what is the best repair method to prevent failure of cracks in the original gel coat that have been filled with fairing compound?

[jimh]

I watched your mercifully short recording of your work with a Dremel Tool (and many thanks for the concise recording) that tried to increase the depth of cracks in the gel coat layer of an older Boston Whaler boat and resulted in pieces of the gel coat flying off.

The reason pieces of the gel coat flew off when the Dremel Tool came in contact with them is the bond between the gel coat resin and the underlying layer of laminate structure of the hull was not good. There was no adhesion between the gel coat layer and the underlying layers of fiberglass laminate.

The cause of this poor adhesion between the gel coat layer chips and the underlying fiberglass laminate layers might be due to the gel coat layer being very poorly protected over the many years since the boat was laminated as a Boston Whaler hull. The gel coat layer may have been exposed to weather and UV radiation for long periods of time, with the result that the gel coat layer became very dry and very brittle.

That the gel coat layer flew off in small pieces as you abraded cracks with your Dremel Tool is actually a good outcome. To have made top coat repairs over these loose and poorly adhered areas of the gel coat resin would have been useless. The gel coat would have eventually debonded from the underlying laminate structure, ruining any top coat that you might have applied to them.

In refurbishing a fiberglass laminated hull, you must remove all the loose layers of laminate and gel coat before you can make a solid repair. This may require abrading away a lot of loose gel coat resin. Once you get down to a solid surface, you can use a primer to fair the surface to a smooth level.

There is a good youTube presentation showing the restoration of an older Boston Whaler boat with many cracks in the gel coat layer at

Boston Whaler Crazing Repair
https://www.youtube.com/watch?v=4tZDBOYqdfA

This demonstration is very nicely photographed and narrated. It is packed with information.