Thread: False Keel Advice Needed

Interesting idea Bornfreee, but it does seem a lot of effort for something that's going to get the crap kicked out of it in short order. I'm an inert materials (read plastics) guy now a days, though the wooden shoe is a tried a true technique.

Hello folks,

PAR gave me some good advice in this thread about fitting a timber keelshoe with epoxy resin to the bottom of my grp boat.

Well, it's taken a while but I'm now in the process of doing that but before I fit the shoe to the boat I need to ask - Would it be a stronger bond if I clamp the the shoe up tight to the boat hull, or should I leave say a 1/8" gap to allow for a thicker bed of epoxy between the timber and the hull? I'm thinking that tight clamping will squeeze out most of the glue make the bond weaker.

redx.

Generally you want some space for the epoxy to live. An easy way to do this is to use some spray adhesive on some light fishing line and tack this to the area, inboard of the edge. On a keel shoe, two strings, just inboard (an 1/8" - 1/4" or 3 - 6 mm) of the shoe edges will do. The string will insure the joint has not only goo in it, but a uniform amount. This is actually an old trick. On carvel built boats, the planking often had some cotton string in the rabbits, which would hold the joint ever so slightly open, so the typically oil base sealant could live without being crushed out, plus if the cotton string got wet, it would swell up, helping seal the joint. I've seen some use little washers to do the same thing, as well as other techniques, all to insure a slight gap.

I'm still in the inert materials camp, like metals, plastics or aunt Millie's potato salad, after it's left out for a week. In fact, I've used about a quart of this to patch some large cracks in my driveway recently.

An 1/8" gap is huge (for this), a 1/16" is better and you'll use half as much epoxy too. No, the spray adhesive (spray the string, not the shoe or boat) will not affect the bond and the fishing line is inert, so . . .

Thanks once again for the good advice PAR.

I'd like to have used the HDPE, UHMWPE as you suggested but the cost of it here is too great for my budget, so I've opted for timber which I'll smother in epoxy. I was thinking of using washers as spacers but the fishing line is a great tip, I didn't think if that one, thanks.

redx

If using my strip on a strip technique, just a few pointers. Of course bond the first strip to the boat, washer, fishing string, whatever as spacers. Insure a good bond. Lightly fasten a sacrificial strip to this bonded strip. You have lots of good hardwoods to choose from down there, so pick a dense one, so it holds up longer. This strip needs to be bedded in polyurethane (if trailer borne) or polysulphide (if moored or berthed) and lightly fastened. I'd use #6 flat head screws, into the bonded strip, just long enough to hold the sacrificial piece. The idea is to let these fasteners shear off or pull out, in the event of a really nasty strike. The bonded piece can have a new sacrificial piece attached to it if this happens.

Eventually, the sacrificial piece might need to be replaced, which will suck, as it's bonded, but if it's damaged enough to need replacement, you just hack it off the best you can, sand back to the hull shell and bond on a new one. I replace these fairly regularly, often ones I've installed many years previous. I usually grab the reciprocating saw and whack most of it off in one shot, getting as close to the hull as I dare. Then I grind it down with one of several tools - the big disk sander with a 24 grit pad makes quick work of it, but a belt sander, a power plane, etc. can also hone it down, so you can finish up with a DA and prep the surface for a new one.

On my boats, only one has need a new bonded strip and it lasted about 15 years first. It lived through 4 sacrificial strips, before the thing looked so bad I just had to change it. If you're not that rough on your boat, as I am, then it could last a life time, with replacement sacrificial strips every so often as needed.

If you want more protection, screw a "half oval" to the bottom of the sacrificial strip. There's two types, hollow or solid back. The solid back stuff is the bee's knees, but expensive. The hollow backed half ovals are much cheaper, but dent easily. Another trick I use, instead of a half oval, is just plain old aluminum flat stock. Most hardware stores sell 3/4", 1", 1.5" (etc.) bar stock and it's easy to drill and counter sink for screws (6" on center). I use this as the protective metal strip, under the sacrificial strip. It's an extra layer of protection as sea monsters and obnoxious mermaids can be hard headed at times, so you can use some metal, to help bash your way through.

Thanks for that information PAR, good advice is always appreciated.

Cheers,
redx