Rot Doctor


Subject: Prindle Cat Soft Hull (pt. 2)
Date: Wed, 31 May 2000

I’m not sure what you mean by cored or solid. The hulls on my p16 seem to have been constructed in two pieces then bound together. The White bottom part of the hull (which has no cracks…one is a little wavy, but still solid) and what I will call the cap (yellow with some stress marks). The one hull that is soft is just soft in the yellow section 1 foot in front of the front cross bar (a 2ft section). This section gives more than the other side when you press on top of the hull. I heard that colored hulls are a thing of the past because the sun/UV rays contribute to a shorter hull life.

Do you think access ports in the hulls forward of the crossbar will weaken the hulls? I know if there were access ports I probably could reinforce the fiberglass as well as add flotation.

Thanks for your great ideas.
Look forward to hearing further comments.
Kevin G.

Good, thanks for the further info. You have a solid fiberglass hull I’m almost positive. Cored hulls have “sandwich” construction. Fiberglass/core material/fiberglass. This is commonly used on bigger boats to add stiffness. On catamarans the stiffness is gotten from the triangle shape of the hulls. This is normally a very stiff design. However, if the fiberglass is not quite thick enough, over time the cracks and softness will occur. This is the same thing that happened to the Hobies that I told you about.

Adding the crossbar to the bows would help, but not completely cure your problem. If I wanted to take the time and effort to make the repair properly, I’d add “stringers” to the corners of the triangle on the inside of the hulls. This will add stiffness without adding too much weight. This means cutting a fairly large hole in the top of the hull, big enough to allow you to work on the inside of the hull. After adding the stringers, I’d re-attach the piece that I’d cut out of the top, repair any surface cracks, and spray some color-matched gelcoat over the top of everything. All in all a fairly big job, but definitely do-able by someone of average skills. At this point the front crossbar would be added insurance against future failure. As far as adding floatation while you are re-strengthening the hulls, that would be fine as long as you keep a channel at the bottom where water can flow aft to the drain plugs. With the stringer design that I have in mind, this would work fine.

If you want, I can certainly coach you through the process, advising of the common pitfalls to watch out for, and what to do to make the job come out right.

The colored hulls thing is new to me. Generally UV deterioration happens to the gelcoat only. It shouldn’t affect the strength of the hull. You certainly notice the oxidation on colored hulls more than on white, but everything gets oxidized by the UV, and it shouldn’t affect the fiberglass underneath.