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

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.

A little light metal work

Hey, I’m excited. I’ve had two like and one comment to the blog. Thanks for the like patmcf and the like and comments from saxisgood. Saxisgood is one of the most loyal of the readers¹ and can be relied on to make comments. Thanks for you both – please keep it up. ²

Anyway, this has excited me so much that I’ve just had to burst into print but a few days after my last post.

In the last couple of days I’ve given up woodwork, gluing, filling , fairing etc³and have fallen back on an old favourite – metalwork.

And it concerns the centre board⁴ pivot.

The centre board is set in a slot in the bottom of the boat and is held loosely in the boat by a rod passing through a hole in the board. This rod is glued across the slot so that, as the board is pivoted about this rod, more (or less) of the board sticks out of the bottom of the boat. Now any self respecting engineer would know that this is guaranteed to make the board wobble. A better mechanical solution would be to have the rod stuck to the board and to pivot it by having a bearing surface at each end, running in bearings glued to the boat. But no, sail boats don’t follow this logic. The rod is fixed and the bearing surface is the hole in the centre board. It’s a very short bearing surface (25mm max) so is quite highly loaded and the board wobbles . Having a stainless steel rod passing through a wooden centre board won’t last long, so two stainless steel trunnions have to be glued into the centreboard.

The piece on the left is one “trunnion”

Here’s where the metal work comes in. I had to hand a piece of 3 mm stainless steel. Cutting these pieces out posed a problem. A hacksaw would take too long, the angle grinder would probably do it but would also take some time and make a lot of sparks. How about the jig saw – I had used one several years go to cut up two Triumph Herald rust buckets to make one slightly less rusty car which my son drove around for a year or so- so I knew they could cut thin metal – how about this stuff. I found some “special” blades for stainless steel, held the sheet firmly with a couple of G gramps, spread oil liberally along the cut line and, with the jig saw to as slow a cut sped as possible, got to work.

The noise was appalling, smoke and oil went everywhere but the special blade did the job – it took about 10 minutes to cut each shape. Then the corners had to rounded off and the burrs removed using the angle grinder and that was it.

All I have to do now is glue them in place and cover the board with glass fibre cloth ………

Wish me luck for next week.

Notes

1. Now at the grand total of 3 in any one day – so much for making a living with this!
2. The making comments, that is.
3. Only temporarily, you understand.
4. Just in case you don’t know what a centreboard is, it’s a large flat (or aerofoil) board that replaces a fixed keel in a proper yacht. Keels (and centre boards) stick out below the boat to provide some lateral grip in the water so that by clever resolution of forces at different angles lets the boat sail at an angle towards the wind, and it does it without the benefit of software – isn’t that clever?

Real, rough carpentry

Another two weeks has flashed past, it must be because we are comping out of lockdown and a social life is just hull up on the horizon. I’ve been getting into practice, partaking of the odd drink or two in other peoples gardens. But then the weather closed in again, so it’s been back to boat building.

We’ve made a bit of progress. The glass fibre cloth has been successfully fixed to the outside of plank one and the spectre of fairing is coming closer. Before undertaking this messy task, the boat needs to have vestigial keel and bilge keels fitted and the plywood centreboard case that sticks out of the hull needs a hardwood casing. All of these bits are necessary to provide some protection to the hull when (inevitably) the bottom strikes some hard stuff, either gently as the skipper deliberately parks her for a night so he can sleep on board above sea level or (more likely) he’s not been paying enough attention to navigation.

The glass fibre cloth in place on the bottm

Another delivery arrived – a few feet of Utilie.¹ This is a lovely dark brown wood, usually with a smooth, close grain. I had elected to have standard sawn sizes, rather than bespoke sizes² and the first thing to be done was to convert my hand held electric circular saw to some sort of bench saw.⁴

A large piece of rough plywood and some offcuts of roofing joists were soon cobbled into shape and there is was – a bench saw. As a sop to ‘ealth ‘n safety I fitted an earth leakage trip in the electric supply and placed the stop button near my foot.

To my great surprise, it worked quite well and I was able to trim the planks to the required sections without trimming bits off me……

Here I am fitting the protective bits around the centreboard case – the weather had warmed up for the day!

The protection for the centre board case used two pieces of 50 x 25 mm section, each just over a metre⁵ long. A trial fit showed that they needed to be bent to match the curve of the hull. Fortunately I found that the force need to bend them wasn’t that great provided I could devise a mean to apply it. In the end I settled for a loop of rope through the centre board case at one end and a weight at the other. As you can see from the video, I supplied the weight and then used G cramps and friction to hold them inplace whilst the epoxy set.

The two bilge keels needed bending too but there was no convenient centre board case to hand, so I temporarily screwed them in place from inside the hull. After the epoxy had set, I was able to remove the screws and fill the holes.

The keel strips were another matter. The yard had supplied three pieces of utilie, cut to shape to form the stem and the first two pieces of the keel, where the bend round the forefoot was through 90^o on a tight radius. The next pieces of the keel (up to and aft of the centre board case) were to be made out of 35 x 40mm section. Cut to lenght, these pieces wouldn’t fit my steamer, so I scrounged a piece of sewer pipe from the builders yard and built a bigger one. Despite soaking the timber in water overnight, and steaming each piece for 6 hours, I could not entice them to bend and stay bent to conform to the required curve. In the end I cut the timbers into strips about 10 mm thick to laminate them into position. This worked really well, only needing a selection of building bricks⁶ at end to make the laminate conform to the keel. Four triangular blocks, 30mm think, formed a transition from the keel to centreboard case.

The electric “thicknesser” – or plane, as I prefer to call it – smoothed out irregulaties at the joins and it all looked rather professional.⁷

Rough carpentry done. Fairing can commence. But that will be in another episode.

Rough carpentry completed

NOTES

1. Well, metres of the stuff which, I was assured, was from an FSC approved forest

2. At the time of ordering, I had only a rough idea of the sizes I would need, so couldn’t be specific³

3. It was more economical too.

4. I had been meaning to do this since I bought the thing about 20 years ago

5. Conversion for those on the west of the North Atlantic and for the brexiteers who still cling to the Empire.

6 The builders yard has a plentiful supply!

7. From a distance.