check the outside bottom curve for glass wear... if worn put on some glass...esp if you spend time beaching, dragging through sand.. the hulls are only about 1/8 thick (w/no foam core on the bottoms).
Mine has it too. The guy in our group who has been sailing the longest puts a layer of marine tex on the bottom of his hulls every year in the off season to prevent beach wear I guess because its cheap and easy to use epoxy and prevents wear on his hulls.
frp is basically a yellowish clear colour, it only stops being this colour when it is covered in non-structural gelcoat
as the boat gets pulled up and down the beach the gelcoat gets worn off first, showing the clear yellowish frp under it
at this stage it's easiest to just flip the boat over, mix up a little white? gelcoat and brush it along the keel-line to recover the exposed frp
if this isn't done, continued dragging on the beach will start wearing the frp resin off until eventually the glass fibres will be poking out of the resin
if that happens things are getting weaker. if it's only a few fibres missing more resin can be brushed over and then covered with gelcoat
if a whole layer of glass-fibres have been worn off then a whole new layer should be added. this is quite a big job and can be done with many different fibres, like kevlar etc. and resins, like epoxy
Thank you erice, good points. I think I am at stage one now as it does not appear, feel or sound different from other parts of the . I will put the gelcoat coat (yellow) on my list of off season projects.
i'll probably do mine again next spring too, on a nice, dry warm day
with the hulls upside down and level i'll sand the exposed frp on the keel-line, to it give some tooth, maybe #120 grit, then wipe off the dust with a cloth, then wet wipe it again with acetone, which is an excellent degreaser and the solvent for most polyester based gelcoats
the acetone will dry off almost as fast as you wipe it on
then due to the nasty toxicity of polyester catalyst the surgical style rubber gloves go on and with a calibrated dropper i'll drop in 1ml of catalyst/hardner into 100ml of gelcoat. don't really need that much but trying to measure less than a 1ml is more difficult than it's worth
with a cheap 1 inch paint brush i'll fore/aft brush the gelcoat over the yellowish frp on to 1 hull, then the other. wait 5min? and do it again. and keep repeating until i run out or the gelcoat kicks and gets too tacky to brush smoothly
takes about an hour, costs about $10?, lasts 2 or 3 years of average sailing, for me anyway
This is what I did to my Prindle 16, same issue,
thought the bottom might be getting a little thin from beaching. Used 3M fiberglass resin jelly. Sanded bottom with #120 and applied jelly. Much easier to work with than liquid resin and goes on much thicker. Sanded down to new profile with orbital sander...Then I taped off 4 inches up the keel and sprayed it with black pickup truck liner spray from a rattle can, black, 2 coats, got it at the auto parts store, used it just like bottom paint. Works great! I sail off of the beach. This stuff is tough. Sand dragging and beaching no problem now.
Aside from redoing the bottom I also filled in a small quarter size soft spot that was there when I bought the boat. Worked just fine. I would use this stuff anywhere
you have a repair. It is thick enough to build up layers
quickly and since it doesnt drip all over the place is much easier to work with.
When I repaired my bottom I did it
on my trailer and just moved the boat back and forth on the
rollers. I did not even have to flip the hulls upside down
to apply this stuff. It just sticks. Make sure you mix it right with the hardener and only mix what you can apply in 5 minutes or so. It sets up really quick. Good luck, it worked great for me.
I forgot to tell you this stuff is not clear, but as I mentioned I put a bottom finish on my boat which covered up the areas that I repaired. If you sail off of the beach, the truck bed liner coating along the keel works great. I have gotten lots of "thats a hell of an idea" from fellow
cat owners along my stretch of beach.
If you are applying the resin jelly anywhere you want a colored finish, you will have to cover it with a matching paint or use a liquid resin that you can apply a tint to.
It starts getting tricky when you are trying to match resin colors on faded gel coat.