Basic boat hull construction question.

[tmh]

Again, a beginner here with a beginner question.....

Could someone describe the basic layers of a fiberglass hull so I know what to expect or look for as I start to do some repairs and/or add new fittings to my boat (1985 v-hull)? By this I mean is there a thin outer fiberglass shell and an inner shell? Is there typically insulation ot other material? Or is the fiberglass solid and thick (3/4" or whatever). Are most fittings just screwed in or are the bolted through to the other side?

Are the sides and bottom usually constructed the same? The back transom is wood - usually one thich solid piece, correct?

Thanks for the info. I'm nervous doing anything to my boat before I learn the basics of what's there and how it attaches.

 

[tashasdaddy]

Re: Basic boat hull construction question.

i think the best education you can get is going thru alot of the restoration post, look at the pictures that have been posted of the floors and stringers, upper decks being removed. mark, ed and jason have very good links to there restoration projects.

 

[oncebitten]

Re: Basic boat hull construction question.

So sorry.

 

[Chris1956]

Re: Basic boat hull construction question.

TMH, Most Fiberglass boats start life as two shells of molded cloth and resin. Gel coat (thickened poly resin) is sprayed on the outside of both shells, and gives a smooth colored finish. Now wooden or fiberglass stringers and frames and the transom(usually wood)are attached to the bottom (inside) of the lower shell. Most are glassed to the shell. Foam is applied to the area between the stringers and frames until it is even with the top of the stringers and frames. Now a floor (usually 1/2 plywood) is attached to the top of the foam, stringers and frames. Now the top shell is attached to the bottom shell with screws or rivits and caulk . This seam is covered by the rubrail. Now the boat is fitted out with fuel tank, steering, engine + controls electrics etc.

The foam acts to strengthen the hull and on good boats, all fasterners are bolted through the hull. The fiberglass thickness is a function of the boat's size. I have seen fiberglass as thin as 1/4" on small boats. If is also thicker where more strength is needed. Fiberglass is strongest if the manufacturer uses continuous sheets of cloth. Long glass fibers=strong construction. I fear that a lot of boat manufacturers are using shorter fibers and composite putty materials which are not as strong. Manufacturers also use "chop guns" which are modified paint sprayers, to lay down a layer of chopped fiberglass cloth, mixed with resin. These are perfectly suitable for surfaces inside the boat (cover the floor, inside gunwales, ski well etc), but since they do not provide much more than waterproofing, are inadequate for any structural work (IMHO).

 

[tmh]

Re: Basic boat hull construction question.

Thanks for the answers. To be honest, although I don't mind doing some research and learning, my needs are to learn what to look for in my boat to do simple things like add fastners, etc. I have no desire to be a boat-building expert.

Chris, great description of the basics. Now I can have a closer look at mine and have a good idea what's what.

 

[ondarvr]

Re: Basic boat hull construction question.

It's a little difficult to say what you may find when you start working on your boat. So many methods, good and bad have been used to build boats (even the same brand and model) that until you dig into it you won't know.

Fittings & brackets should be through bolted with a plate on the back side, but just bolts and washers are are OK most of the time. Cheap and flimsy, is screws just screwed into the fiberglass, but its common.