The dreaded epoxy fairing compound!

If you have already read about the first phase of Kyria's restoration then you may have noticed a mention that in hindsight the application of the epoxy fairing compound was a big mistake.  Well, this is putting it mildly!  I think the effort required to sand this fairing compound was one of the reasons (amongst others) that I gave up on the restoration the first time round.  That and having to start working for a living!

To recap quickly, the fairing compound consisted of West System epoxy resin mixed with their 410 Microlight filler - which is described in their literature as "the ideal low-density filler for creating a light, easily-worked fairing compound especially suited for fairing large areas".

It wasn't the fairing compound itself that was the problem, as such, but the way in which I had applied it.  I was young and enthusiastic, but I knew nothing about fairing.  I just plastered the stuff on each plank as I went.  Not only was I filling the hollows, but I was also putting just as much of the compound on the high spots too, which would mean a lot of unecessary sanding!

​To top it all off, I wasn't mixing enough of the filler in with the resin.  You are supposed to keep adding the filler until the mix becomes a 'peanut butter' consistency, which is then trowelled onto the surface to be faired.  My mixture had a lot more resin in it and I was actually applying it with 2" throwaway paint brushes!  All this meant that the fairing compound was a lot more difficult to sand than it should have been!

I really cannot understand what I was thinking doing it in that way.  When approaching work that I haven't done before I normally read everything I can find on the subject so that I can learn from the experience of others.  I also usually follow the instructions closely on such things and test on a small area first to make sure that it works before going too far.  We live and learn!

Removing the epoxy fairing compound

Because the epoxy had been degraded somewhat by UV light over the 20-year period, I decided to remove it completely rather than trying to fair the surface as it was.

I started off trying to remove it using a Festool Rotex 150 sander with very coarse 24 Grit heavy duty sand paper.  This is a very powerful sander which is normally very good at removing material quickly in Rotex mode (the highly aggressive sanding action comes courtesy of a combination of eccentric and rotational motion of the pad).

6mr Kyria epoxy fairing compound

Port side prior to starting on removing the epoxy fairing compound

6" Rotex sander initially used for removing the epoxy

The sander removed material fairly well to begin with, albeit not as well as I expected, but the grit was losing its edge very quickly and after sanding a section about 300-400mm square the heavy duty sanding disc was no longer removing much material at all.  This would mean that I would need to change the sanding discs very often and as well as being rather slow it would ultimately be quite an expensive way of removing the epoxy.

Another issue was that as soon as the sanding disc went through the epoxy it would remove material far too quickly from the wood itself.  Even with a hard pad this left an uneven surface with low spots where the disc had gone through to the wood and high spots where epoxy resin remained.  The sanding disc was tending to skate over the surface of the epoxy, whilst wherever it touched the wood it would grip and remove too much material.

6mr Kyria epoxy fairing compound

This section of the bow took most of the day with the sander (and many sanding discs!) and there's still a lot of the fairing compound left to remove!

After a while I decided to try a different way of removing the epoxy.

I knew there would be a learning curve and tried to perservere with the sander.  Whilst I did improve the control somewhat, I still wasn't happy with the result I was getting.  After a while I decided to try a different way of removing the epoxy.

I had a new Stanley Surform Plane in my toolbox and I thought that perhaps that would be more effective at removing the fairing compound.  I should have known better!  No matter how much pressure I tried to apply, the surform plane just skidded across the surface of the epoxy without so much as touching it!  Back to the drawing board then...

The surform plane was useless, but it did give me an idea.  One of the other tools I had was an old Stanley Bailey No. 5 jack plane and I thought that might be worth a try.  So I sharpened the blade and gave it a go.  Eureka....it worked! 

If I set the blade to remove the right amount the fairing compound was coming off in shavings (well almost!).  This seemed like a much better way of removing the epoxy and as long as I planed at various angles the long bed of the plane would help to keep the surface reasonably fair as I went.  It also felt a lot more satisfying than using the sander!

​The only drawback was that the blade in the plane didn't stay sharp for very long either.  I found that I had to re-sharpen the blade every 10 minutes or so, otherwise the plane just skated across the surface of the epoxy.  Having to hone the blade all the time certainly became a bit monotonous after a while, and using the plane on a vertical/overhead surface was hard work!  But at least it was more effective than the sander. 

6mr Kyria epoxy fairing compound

Epoxy removed from a good section for'd using the plane

The vintage Stanley Bailey No. 5 jack plane I used to remove the epoxy fairing compound

Proceeding aft, some areas with epoxy removed, some still to go

Stanley honing guide that was very useful when sharpening the blade

I started off planing at different angles to fair the surface as I went, both diagonally and fore-and-aft, and then finished off by planing fore-and-aft in the direction of the wood grain, but angling the plane diagonally slightly to keep the surface fair in all directions.  By working in that way and keeping the blade sharp I found I was getting a nice smooth and reasonably fair surface.  It was more difficult to get a fair surface on the sharper turn of the bilge (at least in a vertical direction) and this area would require more work with a suitably flexible long sanding board later.

There were also some areas where the plane would not work at all - such as the sharp concave curve between the bilge and the keel (particularly the tuck).  The same applied to any areas where there was considerable twist in the planking - the flat bed of the plane could not accomodate any twist.  In these areas I just had to sand the epoxy by hand using a purpose made sanding block with a convex shape to fit the the concave curve.

6mr Kyria epoxy fairing compound

The majority of the epoxy removed, still some more fairing to do

6mr Kyria epoxy fairing compound

One of the adjustable trestles I made to support scaffolding planks

Shaving of wood from a plank with epoxy from the seam still attached

Initially started off with two levels for the staging aft, but increased this to three later as it was difficult to work under the counter stern.

Long-boarding to fair the hull

Once I had done as much as I could with the plane, the next step was to sand the hull fair using a long board - or often more aptly named a 'torture board'!  Initially I started off with some manual sanding boards that I had made with various thickness of ply (varying degrees of stiffness for different areas of the hull), but then I came across a sanding board made by a company called Flexisander, which is specifically designed for fairing.  This works on the same principle as a wiper blade in order to ensure a more even curve and better contact of the sand paper with the surface.  As with the plane, it was best to sand in many different directions, including diagonally and fore-and-aft.

6mr Kyria epoxy fairing compound

The Flexisander - a manual sanding board - this one is just under 4ft long (1120 mm) by 115 mm wide and is fitted with velcro to take velcro-backed sandpaper

6mr Kyria epoxy fairing compound

I used this flexible sanding block for tighter curves, but it was much too flexible and so I took some aluminium sheeting and velcro'd that to the base of the block and it worked quite well then.

Fairing the hull with an array of different sanding tools to suit different areas.

This was another flexible sanding board that I made myself as I wanted something a little less flexible than the Flexisander for some areas.  This turned out to be a good general purpose fairing board.

I have to say that longboarding has got to be one of the most soul destroying jobs to do on a boat!  It took me the best part of 3 weeks to fair just one side of the hull and I still have the other side to go yet!  I will certainly be glad when I can move on to more constructive jobs.  Below are some more photos showing the port side at various stages of fairing:

6mr Kyria epoxy fairing compound
6mr Kyria epoxy fairing compound
6mr Kyria epoxy fairing compound

Well, that's all for this update.  The next post will be on removing the old epoxy and glass cloth from the plywoood subdeck.  I wanted a break from working on the hull before I tackled removing the epoxy from the starboard side and I also needed to move the boat to make room to work on that side also (this will be covered in a future post).

As usual, please feel free to leave any comments below and share with any friends that might be interested!

Share this page:

Leave a Comment: