Bottom hulls job, gel-coat question :: Catamaran Sailboats at TheBeachcats.com

catdanI have an old P18-2 that is in desperate need of a bottom hull job, leaking perhaps 3 gallons of water in 2 hrs on the water.

This may have been asked before but I was unable to find the answer in the archives:

I would like to avoid sanding down all the gel-coat completely, except around the bottom parts. Is is possible to just sand down and fiberglass the bottom parts, slightly sand the entire hulls, and spray on gel-coat?

What products would you recommend? Or is gel-coat just tinted polyester-resin?

Hey Dan,

I am new to cats, but have two sloops that I have done a lot of work on. So the topic of hull repair is not new to me. I am not proclaiming myself as an expert, but here is my personal experience and what has worked for me:

I just purchased a Sol Cat 18 that also was leaking on just the starboard side. I was warned by the previous owner that he drained about 5 gallons of water after a few hours on the water.

Why glass the entire bottom of the hull? After glassing you are going to have to fair that new glass if you don't want to affect speed. Then after fairing, which is a lot of careful sanding and filling...and sanding and filling...and more sanding...you are ready for gel coat or whatever else you choose to put on the outside. Did I mention that glassing anything from the outside is going to require fairing and SANDING? I am so tired of sanding :)

I got my cat home and filled it with water until I could see that the daggerboard trunk/slot (or whatever it's called on a cat) had a very thin area where the water was leaking. There was a slight crack on the bottom edge of the trunk. I simply glassed from the inside (port access) with fiberglass tape (5" wide 6 oz cloth, two layers) and made sure to fillet the corners with epoxy filler to avoid any air pockets in the fiberglass layup. Of course you want to sand first and also clean with some acetone first.

Once that dried I roughed up the same area around the outside and used some filler to patch the crack completely (at this point the leak is already fixed by the inside repair). The filler is just to hide the crack and smooth the outside. I am not going to even bother with hiding the filler on the outside since it's inside the trunk area.

I would always try to repair from the inside IF POSSIBLE. If that's not possible, then go ahead and repair just the problem section from the outside. If it's a small area and I am going to reapply gel coat, then I use polyester resin. If it's a large enough area to warrant painting most of the hull I personally prefer to go with epoxy resin and then use a two-part paint over that (which you can roll and tip and get a professional looking job). Keep in mind that to paint you need cooler weather so the paint has time to flatten and give you a glass like finish. Not sure what area of the country you are in, but I'm just outside Sacramento and it's already in the 80's by 9 am. Got to wait until fall or spring to paint with polyurethane here (if you want the best outcome).

Polyester resin doesn't stick well to itself, so that's the reason for only using it on small repair jobs. The same for gel coat (polyester)...spraying a second coat of gel coat won't last as long as the first. You also don't want to spray it on too thick because you'll get spider cracks after your hull flexes. I have plenty of stress cracks on an O'Day 240 where they sprayed the gel coat on too thick and the hull flexed.

My cat has the original gel coat and then a lot of touch up enamel paint. So when it gets time to freshen it up I am going to go with 2 part paint myself (Interlux Perfection 2 Part). This requires a primer to go over the gel coat.

If you can find someone that has done it before to help you with the first coat your pretty much guaranteed professional looking results...it's all about more thinner coats and not less thicker coats. And no fussing and going back after you roll it on (just slightly 'tip' any air bubbles with a brush IF you have any at all and don't keep messing with it). Most people tend to try and lay it on too thick and then you get very visible brush marks! Done right the paint will flatten out well and quickly skin over and when you have several coats on you will see your reflection in the paint (4 coats).

Dan

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Bottom hulls job, gel-coat question

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