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post #5 of Old 06-26-2001
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Glassing hull

(This is very long so you may want to print it out)Glassing a wooden boat is not something that should be undertaken lightly. At best it should be the last resort when there is no other way to salvage a boat. Oddly enough if the boat is in halfway decent shape glassing a wooden boat actually is shortening its useful lifespan.

The success of glassing a wooden boat is heavily dependent on the construction and condition of the wooden boat, and the materials and methods used to glass it.

Boats that are strip planked, plywood and splined and edge glued construction are easier to glass successfully. Carvel planked boats are much harder to glass successfully and lapstrake cannot be glassed at all. Softwoods and soft hardwoods are easiest to glass. Materials like Oak or Teak are next to impossible.

In terms of materials, using epoxy resin greatly increases the chance of a successful job. Epoxy offers a combination of much greater adhesion, greater ability to withstand flexure and excellent impermeability. Obviously epoxy is more expensive, can be more difficult to work and has fewer laminate choices. On the other hand, its properties are so superior that unless the project is a quick and dirty job with an acceptable lifespan less than a few years, I would not even consider using any other type of resins with wood.

To glass a wood hull, the hull needs to be very dry, both inside and out. It is much easier to glass a boat when it is upside down and it may actually be worth while to empty the boat, remove the tanks and engine, drop the ballast keel and turn the boat upside down.

The process starts by removing every bit of the existing finishes on the hull. All cracks, seams, dings and dents are raked clean. The hull needs to be refastened as necessary to connect the skin to the internal framing of the boat. Any damaged frames should be sistered or replaced. The boat is jacked as close as possible to its lines. High spots are faired as much as possible.

The hull is then thoroughly dried and then saturated with un-thickened epoxy, which will require 2-3 coats depending on the species of wood. Once the surface is completely saturated and sanded all over, the seams are filled with thickened epoxy. It may be necessary to run a Skillsaw or panel saw with a shallow blade setting along each seam to get a clean faying surface for the epoxy. Next the hull is thoroughly faired with thickened epoxy. This is a fairly tedious process of filling and long boarding.

You also have the problem of what to do about the ballast keel. Often the ballast keel is glass encapsulated. If you are going this route the keel bolts and floor timbers should be replaced and or repaired. This will be the last chance to replace the keel bolts easily. If you don''t encapsulate the keel then the keel should be dropped and the glass carried into the hull to keel joint.

Once the boat is completely fair you are ready to start glassing. You will want to precut the laminate and be able to do each lay-up in a continuous pattern. Pre-pregging the fabric, vacuum bagging and post curing can increase the ease of lay-up and or your likelihood of success.

You have a number of options with regard to the number of laminations. With sheet, cold or hot molded plywood or splined and edge glued construction you can often get by with a single lamination acting as a moisture proof membrane. On a carvel planked boat you really need to build up a structural outer skin and so a number of laminations will be required. With strip plank you may be able to either. If you encapsulate the keel multiple layers will be required in the area of the hull to keel joint.

Then you start your final fine fairing. Start by sanding and filling any obvious dips and dings. Once fair, below the waterline paint on several coats of untickened epoxy to act as a barrier coat. Above the waterline, start blocking the hull using an appropriate high build primer and a long board to show the high spots. It is a multi-cycle process using spot fillers and died primers. This is a big job but an important one if you want to end up with a yacht like finish. Once the hull is ready to paint throw a couple coats of paint on the protect the Epoxy from UV and then turn the boat over.

Strip all finishes on the inside of the boat and completely saturate the planking and frames with epoxy to keep the planks from swelling and contracting. Flood seams and cracks in the wood and joints at butt blocks and frames with un-thickened epoxy. This process is enormous work. You can almost build a replacement hull easier and faster using the existing hull as a plug or a mold.

You have other issues about how to do the hull to deck joint. But this covers the basics. I strongly suggest that you stick with quality known products. The two that I really like are WEST System epoxies and MAS epoxies. MAS may have some advantages but both offer good factory support. MAS can be reached on line at

WEST System can be reached at
WEST also has a lot of how to pamphlets and they used to have a very good one on just this subject.

Then there is the affect of glassing a boat on its performance. My old 1939 Stadel Cutter had been glassed. Theis really advesely affected her performance turning a reportedly pretty quick little boat in her day into a real slug. Boats are just not made to take on that much additional weight as a skin. This weight increases stress on rigging and can adversely affect seaworthiness and comfort at sea.

One final point about the guy''s suggestion about the lobster boats being glassed. Lobster boats are generally strip planked and at least when I was a kid they were generally planked in softwoods, more often then not, cedar. These are are good candidates for glassing but glassing a wet hull, especially with a polyester resin is a sure way to have a premature failure of the glass to wood connection.

Good luck
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