Fairing the Hull Patches: Things Get Messy!

12 Dec

It has been cold of late even here in New Orleans and also a bit wet so we haven’t gotten too much done on the boat itself. But there’s always plenty to do in the shop, so we haven’t been idle! I’ll get into that soon with some posts on the chainplates we are fabricating but for now I’ll pass on a couple lessons we learned from the bit of fairing we’ve been able to do.

Having patched the through hulls satisfactorily, including a second session of glassing on some of them, we have moved onto trying to get them to blend smoothly with the hull, called fairing. In the epoxy manuals this is made to seem like a quick, simple task. Not surprisingly it didn’t go nearly as simply or as quickly as we tried to convince ourselves it would! The thing about fairing is that while the concept is simple -just mix the epoxy and low-density fairing filler, slather it on and trowel off the excess- the epoxy/filler mixture manages to combine all the worst properties of stickiness and runniness such that it is an absolute terror to work with. Of course it didn’t help that our first attempt at fairing was made late in the day with sundown threatening, nor that we tried to tackle all the holes at once. Predictably, things got a bit sloppy!

Our main difficulty was the consistency of that gloppy red mess. First, we didn’t use enough filler and our patches on the hull began to run:

Then we used a lot more filler and it got so thick that it was the consistency of bread dough and sort of sticking to itself such that when we tried to get a smooth surface with the trowel we would end up with little beads and gouges instead:

With these consistency issues our first attempts at fairing ended up not very fair at all but that’s ok because the low density fairing filler is designed to sand easily so it is very forgiving when mistakes are made. Eventually, on our second day, we dialed in an epoxy/filler consistency which felt about right and gave us reasonably smooth results. Here’s the play-by-play, this on the following day:
First the epoxy and filler is mixed to a ‘peanut butter’ consistency. This is one of the many instructions in the West System epoxy manuals which seems straightforward until you actually try doing it! We were not helped by the cold(ish) weather which made the epoxy thick and sluggish.

Once the filler is mixed it is troweled over the repair. The first pass is done lightly and with lots of epoxy/filler on the trowel. We found a sharp angle was best in order to distribute epoxy over the entire area and push it into any gaps. If the repair is very rough it might take a couple passes. The goal here is to get epoxy into any gaps and all over the repair.

Then, we fair the area by taking one pass with the trowel at a wider angle. This time the goal is to take off epoxy rather than laying it on so it helps to use a bit of pressure. You should be able to get a smooth surface without gaps or bumps with a single uninterrupted pass. If you don’t, simply try again. Just makes sure to push epoxy back into any gaps that may have formed.
This procedure is the same on any fairing job which is small enough that you can get the whole area with one sweep of some sort of trowel. We also did this on some spots where the deck had deformed slightly at hardware attachment points. Being smaller these repairs were much easier:
First thickened epoxy is laid down. Not the sharp angle of
 the trowel- this helps to push the epoxy into any gaps.

The repair should be completely covered in the epoxy/filler mixture.

Then a single sweep of the trowel levels the repair, leaving epoxy only in the low spots.

Of course it will look messy until painted, but it 
will be nice to have a smooth deck again!

This article was syndicated from Safe At Harbour But Meant For The Sea: DIY Sailing with Paul Calder


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