Keel damage

homerjack · Posted: Sat May 03, 2014 7:35 pm Post subject: Keel damage

Chewed up about 3 ft section of keel under cockpit on rock last summer. About inch deep along length. Thinking of grinding to fresh glass and shaping new chopped glass and resin and grinding edge shape. Any suggestions?
Thanks.

homerjack · Posted: Sun May 04, 2014 12:06 am Post subject:

Can I use Marine-Tex for this?

colobear · Posted: Sun May 04, 2014 12:22 am Post subject:

How wide is the gouge, and how deep all along its length? If it is not too wide or deep you may be able to use epoxy, you can color it to match the hull. Best of course would be reglassing depending on how deep of course. Pictures would help. I had a similar gouge from Lake Powell, not an inch deep though, and was able to make a good repair using epoxy.

homerjack · Posted: Sun May 04, 2014 12:28 am Post subject:

The keel is V shaped. The entire point of the V has been sheared off down about an inch leaving at least an inch wide flat jagged area running about 3 ft long. Yeah I slammed the rock pretty good.

thataway · Posted: Sun May 04, 2014 6:26 pm Post subject:

A photo would help. If it really is an inch deep--it is probably in the sold glass area, which starts in front of the helm bulkhead. Again, assuming that it is in the solid glass area, and an inch deep, this is a significant damage, and needs to be rebuilt with glass. There are three choices--polyester is cheaper, and in some ways easier to work with, but does not have as good secondary bonding characteristics. The next in vinyl ester resin--better adhesion, it does allow easy application of gel coat, and is a little more expensive. The third choice is epoxy. Epoxy has the best adhesion, is stronger, but you have to choose which glass fibers (especially mat, since some of the mats have sizing which does not dissolve in epoxy, and thus not as good penetration. Gelcoat does not stick as well to epoxy. Epoxy has to be protected from Ultra violet light damage (not a major problem on the bottom of the boat).

I personally like to work in epoxy, because of the adhesion, but in your case, I would use vinyl ester resin. I would grind away all of the damaged glass; normally you want at least an 8 to one taper as you work in from damaged glass to good glass (again, a one inch deep gash leaves little of the original laminate. I that part of the boat was probably built with mat and woven roving. Today, I would be considering using 1708 which is 17oz biaxial roving at 45Degrees, stitched to 3/4 oz mat. because it is a repair, I would lay down 1.5 oz mat first, then a couple of 1708 and finally on the top, matt to build up the last amount to fair to the contour-- at least one coat of resin rolled on, and then gel coat. (You have to occlude the air from gel coat for it to set up)

It could be done in all mat, if the gouge is not as deep as indicated. In that case, I would just use polyester. There are many different ways to do this type of repair.

If the bottom of the boat is painted, then you don't have to worry about the gel coat--and just put a couple coats of finish resin, and sand it fair.

If it was a small gouge, and you were going to paint it, then MarineTex might be acceptable. Repair folks don't like MarineTex, since it all has to be ground out when you want to re-laminate a repair. The polyester does not stick as well to epoxy, as epoxy sticks (secondary bonding) to polyester. Marinetex is a good epoxy for small repairs, and some other uses, but it does not have the glass fibers in it, so there is not as much strength for a large repair.

tsturm · Posted: Sun May 04, 2014 8:44 pm Post subject:

potter water · Posted: Sun May 04, 2014 9:52 pm Post subject:

It would be a good idea to let some expert boat fiberglass folks/surveyors look at the damage. Unless you are really experienced, you may miss some other structural stuff as a result of that kind of hard hit. I'd worry about delamination in the keel area for example. Delamination behind what appears to be solid structure takes real expertise. From the sounds of it you may well have something other than cosmetic to worry about. It would want the opinion of a very knowledgeable person to make you or a future buyer comfortable with putting another decade or two on your boat.

Of course, pictures may change my thoughts a lot, one way or the other.

Good luck.

homerjack · Posted: Sun May 04, 2014 10:17 pm Post subject:

Yeah I was kinda thinking along those lines. Gonna take to a shop. Thanks for the advice.

colobear · Posted: Sun May 04, 2014 10:39 pm Post subject:

Good choice