Through-hull holes
I have a special *patented* (not really) system for eliminating (filling in) these holes. Easy, no-brainer and, done right, entirely adequate.
First, realize that most people do these backwards. For some reason they will patch the inside first and then go outside to fill it from there. Why do work upside down?
Using my method, you first (after sanding and cleaning with acetone the whole area) stick a patch of duct tape (yes, honestly, duct tape) over the hole on the outside of the hull. Make sure it sticks well. Then go inside and snip out 'cookies' of mat, bidrectional and/or Fabmat. Really anything will do. Only woven roving (Fabmat without the mat part) should be avoided as it does not absorb resin well. Make their outside diameter to match the inside diameter of the hole. Make as many as will fill the hole to the thickness of the hull, when dry, then make about 4 or 5 more.
Also cut out the patches for the inside too: given a 1-1/2" through-hull hole (holding tank exit, tranducers), make one about 6"-7" in diameter and two or three more in progressively smaller sizes. These should be in bidirectional or else just mat. Avoid cloth as, believe it or not, it's not that strong for puncture stresses.
Tape off the unaffected/sensitive areas, etc.
When you wet out these cookies and lay them into the hole, keep daubing with the brush till you have good ooze all around the cookies. You will push against the duct tape. This is desirable (just not hard enough to make it fall off). Take the roller to it only when you've got the last one or two cookies bulging up a little. Then lay up the biggest patch first, centered over the hole, and then the next smallest and so on. Doing patches from smallest to largest results in air gaps around the perimeter of the smaller ones. You don't want that.
With the roller, press the patches down till the biggest one is adhering well to the inside of the hull-- no air voids around the topmost cookie in the hole. If you haven't put enough resin or cookies in the hole, now-- and only now-- is the time to peel up the patches, add more resin and redo the patches. Air pockets in hull patches usually mean weakness in a place where you don't want weakness. Don't make yourself regret having cheated here. In my (42 years) experience, the best advice is: DO NOT SPARE THE RESIN. (I so often have to remind boatbuilders: it doesn't say 'Cherubini Yachts and Resin-Conservation Company' on the building. Nor does it say 'Cherubini Yachts and Sandpaper-Preservation Society'; but I digress.)
When the patch kicks off, go outside and peel off the duct tape. You should/will see a bulge where the cookies were pressed a little through the hole. Sand/grind this down to be fair with the hull. If you filled well, with enough resin, you should see an even little greenish-gray line around the perimeter of the patches; this is the resin filling the round seam there. If you see little voids in it, you can patch them with vinylester-based, waterproof structural putty, using a knife, and sand them fair. If you see big voids in it, you did something wrong (see note about resin conservation, above).
To finish this off, the best way is to now sand out a little dish, about the size of a medium-sized pancake, tapering to nothing at the ends (as though you're to lay up a teacup saucer, only not quite as deeply into the hull). When this is clean, make some patches like for the inside and lay them up over the outside of the hole. You can use a dead-man, like a broom handle, and a circle cut of Starboard or wrapped with sheet plastic to prop this patch against the hull to ensure good adhesion. But most of us with Hunters don't have hulls that thick; and I haven't had any problems with just sanding off the cookies on the outside and fairing it over. I did all mine in this way.
I included three pics:
The one from outside is of the filled patch, with no gelcoat or barrier coat showing, not yet faired-over smooth. These two are the inlet and outlet from my boat's original toilet system.
The second one is of some cookies I cut out to fill miscellaneous holes in the cockpit. They don't have to be exact. They're just getting stuffed into place. Again, don't spare the resin.
The third one is of a hole in the cockpit pan which has received duct tape and will be filled with the cookies in the other picture.
Stuff in the blog may be helpful; browse around or just ask me. :dance:
