Three Weeks behind the mask

No, I’m not talking about an extended tour of UK High Street as lockdown is eased. It’s fairing time! What an incredibly messy job. It reminded me of the slightly eccentric chap who taught me real physics at the tender age of 16 (me, not him). He gave us all a handout telling us how to rejuvenate old cycle lamp batteries – those things with a zinc case, containing some noxious black powder with a long carbon rod stuck in the middle of the powder. The carbon rod made the positive terminal and the case the negative one and some sort of chemical reaction between the powder and the case produced the volts and some meagre amps. The cycle lamp (dim at the best of times) would get fainter and fainter until is became a dull red low. “Instructions for Rejuventation” it read. “Pull the top off and remove the carbon rod. Shake the powder out onto a sheet of paper and stir it about. Repack it and the carbon rod back in the case and glue the top back on. It will give you another few weeks. IT MAKES A TERRIBLE MESS. DO IT AT HOME, NOT AT SCHOOL”. I didn’t attempt it in either location, so still don’t know if it would work 1

But, as usual, I digress.

The art of fairing 2 involves mixing up lots of fine powder with lots epoxy resin, smearing it across a surface and then sanding it off again leaving, one hopes, a super smooth surface without defects or lumps that, when painted with gloss paint will look fantastic. This way plywood pieces that did not quite align as they should have 3, finger joints that make two seven foot planks into one 14 feet long 4 and glass fibre tapes that reinforce the joints 5 (not to mention the spills of epoxy and the inadvertent saw cuts) are all hidden from view.  It was (a) quite hard work and (b) made an awful mess, with white dust everywhere.

Bearing in mind the last part of the instructions for rejuvenation (see above) I didn’t do this at home. The boat was upside down on the trailer so it could be pushed out through the doors of the boat shed and do it outside, weather permitting. Thus, lots of plastic particles were released to the atmosphere…

There were four stage to the process

Stage 1 Making the tools

I soon realised that my little 50mm x 100 mm 6 wooden sanding block was not going to be up to the task. The electrical orbital sander would be effective on smaller areas but the dust would be beyond  the capacity of the inbuilt collection filter and I really needed something that would sand the filler flat over long stretches and sand it over the curved surfaces at the bow. This called for some serious inventing.

First of all an improved dust collection for the orbital sander. Some duct tape 7 and a convenient piece of tubing made an effective coupling to the Vacuum Overhead Dust Extraction System.8

Then I needed some larger sanding blocks. The first one, for long flat surfaces, was easily made up using a piece of 18 mm ply wood and a few screws and a long strip of 80 grit sand paper. A couple of handles (more plywood) and there it was.

Now, how was I going to be able to sand round convex shapes? I needed something springy. I tried a saw blade but it was too stiff. I had some 1mm thick ply from years ago and cut that into two 75 mm wide strips, which I laid along a thicker bit of ply to act as a base. The strips were held off the ply base by blocks at each end and only fastened to one end.

Sand paper was then laid along the strips and fastened at each end. When the whole lot was pressed over a convex shape, the strips slid over each other and at the loose end, forming a uniform curve support for the sandpaper. So we now had a fixed flat sander and a variable curve sander. Off we went.

Stage 2 Mixing the fairing compound

I’d been used to mixing generous amounts of epoxy and a hard filler to make joins and fillets. Now I needed to mix large amounts of epoxy and a much finer filler. It was a bit like mixing flour and milk to make scones. You had the liquid (the epoxy) and the flour (the filler) and it took skill and patience to mix them together to get a uniform and useful constituency. Not too stiff, other wise it’s a B****r to spread. Not too soft, otherwise is runs all over the place when put on sloping surfaces. But just right, like Goldilock’s porridge.

Stage 3 Spreading the porridge

This was like plastering a wall. I need one of those things that plasters use to hold the sloppy plaster in one hand so that they can scoop it up onto the float and then on to the wall in one fluid movement without spilling a drop. I think they call them a Hawk.

Another piece of scrap ply was fitted with a handle and the plasterers float was found at the back of the shed in the box marked “it might come in useful”.

The Hawk (not to be confused with a dinghy of the same name)

But, alas, the fluid motion had never been very fluid and was now positively creaky. I learned to limit my ambitions and do on about half a square yard at a time.

Eventually the bottom was covered with the stuff, as was the transom.

Stage 4 The fairing

To my surprise and delight both sanding tools worked quite well. Despite VODES, sanding dust flew all around, on my shirt, in my hair and up my nose. Here’s where the mask came in. VODES was successful in controlling the dust from the orbital sander and the collection bag rapidly became full.

I forgot stage 5

Repeat Stages 2 – 4 until satisfied.

It took three weeks.

Oh Yes, Stage 5. Clean the last of the dust off with tack rags and get sticky hands

This image has an empty alt attribute; its file name is 20200710_150345-1.jpg
Stahe 5 – Tack Cloths to wipe off the dust

Next week, the boat gets turned the right way up9 and gains a cockpit floor, a ballast tank and a bouyancy tank.

Notes

  1. Do NOT attempt this with any modern battery – it could catch fire or explode!
  2. One of my readers has sent me an email, suggesting I’m an artist. I’m not sure where he gets this idea from…….
  3. Surprisingly few – only at bow and stern.
  4. So far, over 100 metres of the stuff.
  5. I’m sure you all have got the hang of converting metric to imperial by now
  6. Never travel without it, particularly to the Moon – it saved the guys on Apollo 13 7
  7. Assuming Apollos 11 and 12 didn’t take place in some unknown desert location
  8. Don’t get excited. It’s only a pond vacuum cleaner.
  9. Without all that hard work of leaning on the centre board – that comes later in life.

2 thoughts on “Three Weeks behind the mask”

  1. Only ever had limited success with plastering my dad was a dab hand and a pretty good all round builder ……..the Hawk was great but most of it ended up on the floor when I tried to ceilings 🤣. Love the inovation with the sanders 👍

    Like

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