Repairs

Have you ever had one of those light-bulb moments? You know, where something suddenly dawns on you seeming without any lead up or introduction. I had one this afternoon whilst I was continuing the work on removing the centreplate case on Shoal Waters and doing very well.

This is a bit of a long post as I took a shed load of photos, but I’m not sorry about that. What do the youngsters says these days? Oh yes…

Sorry, not sorry.

I’d spent a few moments making a portlight template on the laser cutter and checking the fit.

This was the light I used as a test since it is not quite round as you can see from the top right. The perspex has been cut away slightly so that the light fits by the navigation light. I’ve just noticed that you can see the cabin light on side. I’d been using that to sweep up some rubbish and forgot to turn it off.

I made the template a fraction smaller so that the cutaway was not required and tested the fit. Good enough and so I moved on to the centreplate case.

All was going very well and I found that there is one place that brass screws were not used in Shoal Waters as you can see from the photo. Annoying to find and excavate but the screws all came out easily once the surrounding wood was removed.

All was still going very well and I decided to take a photo of the support under the bridge deck so that I know how to put it back again once the rebuild is under way.

Likewise the port side as this has a stop screwed into the top of the case to prevent the block and tackle used to raise and lower the centreplate from pulling the upright out.

Then I remove the starboard upright and that is when the light bulb went on.

Up to this point I had decided that the original case was two layers of plywood laminated together but this showed me that I was wrong about that. You see, the upright was set into the case through the outer layer of plywood.

This is a closer look. And the light-bulb moment was that Charles would not have cut away one layer of plywood on the case to inset this upright, he would have just put it out the outside. That in turn meant that the entire outer layer of plywood was not original but put there by Charles when he first constructed Shoal Waters back in 1963. Looking at the construction of the cabin shows quite clearly that this outer layer of plywood was put on first, apart from where the bridgedeck support uprights were placed. All the other parts of the cabin that are fixed to the centreplate case attach to the outer layer of plywood and are not inset.

So why is this shocking? Quite simply:

If Charles had not constructed Shoal Waters in this way sometime in the last 20 years she would have sunk and quite possibly whilst under sail.

A bold claim, I hear you say but isn’t that just supposition? Let me show you what I mean.

It didn’t take long to clear away all the beading and other centreplate supports from the top of the case and to then cut the side of the case away.

Like this. A very satisfying moment but I need to show you a closer look at one part of the side removed.

This is the inside face of the aft part of the case side with the top to the left. As you can see, someone has tried a repair job at sometime during Shoal Waters’ life, that yellow gunk looks like epoxy. Still, the part of interest is the smooth area at the top left.

This bit here. That smooth bit is the inside face of the outer layer of plywood.

That is to say that the entire inner layer of plywood, the one originally build by Fairy, in this area has gone.

The rest is in pretty poor shape as well and there may be other areas of the case where the inner layer has completely disintegrated. If this is the only part then when the boat is upright, this is out of the water. but would have been under water when heeled over, that is when sailing.

If the original layer is missing in other places that are underwater all the time, then it is likely that Shoal Waters would have sunk on her mooring.

But, I hear you say, that’s all well and good but how can you tell that the outer layer is not original. Just finding one part where a support has been inset doesn’t mean that the outer layer wasn’t original.

Well, I can’t say 100% that it is not original, but I can say to 99.999% and that is because I own Naiad, a Shoal Waters look-alike built from a Fairey Falcon by yours truly. The hull dates from the same year as Shoal Waters.

So I hopped into Naiad’s cabin armed with vernier calipers.

Here is the width of the top of the centreplate case in Naiad to the outside of the plywood from the top. Just over 31mm

Now, using the proddy end of the calipers I’ll measure the width of the top to the outside of the case.

Like this.

The result is just over 31mm.

So, Naiad, a Fairey Falcon hull built in the same year as Shoal Waters has a single layer of plywood for the centreplate case sides.

Now look at a photo of Naiad’s centreplate case before the cabin was built. The side of the case is unbroken from the tip of the case back to the aft of the case, although you can only see the front part in this photo.

Now look at that part close up in Shoal Waters on the port side where I’ve not removed anything yet.

That is the front edge of the second layer or plywood which stops just behind the shaped part where the mast step goes. It’s not easy to see in this photo due to the lighting, but it is there. All this is pretty conclusive to me.

So, having convinced myself that Charles’ original construction choices prevented a disaster, I carried on.

I removed the layer of plywood that was inset into the hull using a sharp chisel. This after part of the plywood came away but not as easily as first part had. The first part practically fell off and made me wonder if it has ever been glued to the hull or whether the prolonged water saturation had dissolved the glue. This part of the plywood was quite clearly glued in place but even so, the glue line broke very easily without damaging the keel timber.

Looking aft in the slot I can see the back of the case but this slopes away aft and is outside the cabin so I’ll need to partially dismantle the cockpit to get the last part out.

I started by making an incision on the outside where two pieces of wood had been joined.

Then looking out from the inside I could see the daylight through the cut, so I know where I’ll be to be cutting.

I did this bit before taking the side of the case off as I thought I might be able to get it all in one go, that isn’t going to be easy so I just took the side off and I’ll work on the remaining piece of the case another day.

So, a very satisfying day but one that is a little bit shocking at the same time.

Time for a cup of tea.

Now that I have enough of the starboard side of the centreplate case removed to see how to remove the rest, I need to add some more support under the keel. The case itself adds significant strength to the keel and removing it will remove that strength. The keel is probably strong enough to support my weight once the case it completely removed, but there’s no sense in relying on “probably” when it is a simple job to add a couple of additional supports under the keel.

So I’ve put a sturdy support under the keel mod-way between the two trailer supports, more or less.

That should do the trick nicely and change the probably to certainly.

Time for a cup of tea.

Now that there is light in the cabin I can continue the removal of the starboard side of the centreplate case and, as the title of this post suggests, I have yet to locate the bottom of the plywood side.

I widened the cut through the base of the case and cut down to a point just above the part that I know is the top of the keel. At this point the plywood is still visible on the inside of the case but it is not securely attached to the keel. Using a flat-bladed screwdriver I was able to prise the plywood of away from the keel and break it off. It is still damp, although not wet any more, and quite easily snapped.

Looking down the slot I can see that the plywood does not go right down to the bottom of the keel, which makes sense since this would make the edge of the plywood touch the water and that would in turn soak up the water, something to be avoided at all costs. So the builders of the hull cut a long and deep recess into the sides of the slot leaving about 6mm of the keel timber intact to form a barrier. Presumably it also forms an edge to locate the case properly.

So, I now have the top of the keel timber and I have the bottom of the side of the case. This means that I can cut away large chunks of the side knowing that I’m not cutting into parts of the boat that I should be leaving intact.

Mind, you, there are screws holding the side of the case down to the keep, so I’ll need to try and avoid cutting those. They appear to be stainless steel and my multi-tool won’t cut through that.

These are the piece of the plywood I removed from inside the keel timber. You can also see from this photo just how effective the cabin light is now that it is installed. This work would have been difficult without it.

The downside of the work is that Charles used something he called Mendix or Mendex spread liberally to cover any gaps in his ‘Clodhopper Carpentry’. I’ve not been able to find out what this substance is, but I can tell you that it is very tough and when cut produces a fine, choking power so I have to wear a breathing mask to avoid breathing this fine dust into my lungs. That means that I need to take regular breaks in the cutting work as this restricts your breathing. Besides that the dust gets everywhere and a break every now and then is needed to brush the dust of and clear up the mess in the cabin.

I usually make a cup of tea (no surprise there) and then resume work once I’ve finished the cup.

Some time later…

This represents about an hour’s work, about all I can do in one stretch. I’m just not used to crouching down into a small ball and then working on something sideways. I need to take a break after an hour. So I need to find some small tasks that take about an hour to carry out in a standing position and do those between hour long sessions cutting away the case side.

So that’s it for today.

Time for a cup of tea.

The title of this post is a little misleading, since what I’m trying to find is where the soft/rotten wood in the centerplate case ends.

In the above photo you can see where I have cut more of the side of the case away and exposed the diagonal end block. I think I have left just one veneer of the plywood on this block and it was very difficult to remove indicating that the plywood here was in good condition. I removed as much as I did so that the new sides will have a significant overlap and therefore a very good seal when it is installed.

The black arrow points to the top of the keel and the green arrow points to a rounded piece of wood placed next to the case side and on top of the keel.

Contrast that with the same area in Naiad (more or less). Again the black arrow points to the top of the keel and the green arrow to the rounded bit. From the Naiad photo it is obvious that the side of the case goes down to the keel at the least and the rounded bit is there to strengthen the joint and to provide a good area for sealant.

But in Shoal Waters there are two rounded bits.

Here’s what I mean. The black arrow points to the top of the keel, the green arrow points to the first rounded bit, equivalent to the one in Naiad and the red arrow points to the extra one. Now, was this original or put in by Charles Stock or Tony Smith? I don’t know but I need to find out how far down the plywood goes so that I can cut away the plywood but nothing else.

I’ve cut away a section out of the top rounded bit but it isn’t clear if the plywood extends this far or not. I’ll let the wood dry and clean it up with a sharp chisel. Hopefully that will show up the demarcation between the plywood and the Mahogany (?) rounded part.

Once that is done then I can carefully cut away the plywood and leave the rest untouched.

Before I go too much further, I should really measure the position of the pivot bolt hole. I’m doing all the exploratory work on one side only chopping away willy-nilly to find out the extent of the plywood. However, when it comes to the the other side I’ll know where cut and should be able to get the side out in one piece. More or less. That’s the plan anyway. That will allow me to use that side as a pattern for the new sides. However, I’ll still make a pattern as best I can once this side is removed just in case the other side doesn’t come out cleanly.

Time for a cup of tea.

The next part of the centerplate case replacement is a bit technical, apologies for that, but has to be done before I cut away any more of the case itself. The first task is to measure as much of the case as I can and draw it out.

I marked a straight batten and 150mm (6″) intervals and then clamped it to the bridge deck such that the forward end was directly above the forward end of the case using a plumb bob to get that lined up.

Then I hung the bob from each of the marks on the batten in turn and made a mark with a white pen on the top of the case and on the bottom.

The marks on the batten.

The marks on the top of the case.

And the marks at the bottom.

The final part of the measuring was to measure from the batten to the top and bottom marks and note these down. At this point it doesn’t have to be precise, with 5mm is close enough for now. Just as well as it’s really hot in the boat and I’m not really that limber, so it’s a bit awkward.

I then drew out the measured line in QCad, the drawing program I’ve used for years. The white line at the top represents the batten, the blue lines are the distance from the batten to the top of the case and the green line are to the bottom.

Then I added a straight line at the top of the case (in red) as I think this is straight on the boat, I’ll have to check, and fitted a smooth curve to the lines showing the bottom of the case.

Now, my CAD program shows me that this much of the case can be cut out of a piece of plywood that is 1210mm long ad 290mm wide. This is good news since quality marine plywood is sold in sheets that are 2500mm long and 1220 mm wide.

Now for the tricky bit. The original case was made from two 7mm thick pieces of plywood laminated together for a total thickness of 14mm. I can’t buy plywood of that thickness, so I have the the following choices. Three laminates of 5mm for a total of 15mm, two laminates of 8mm for a total of 16mm or a single sheet of 15mm thick. I did consider two 6mm laminates, but this will result in a case that is 2mm thinner than the original and although it would probably be fine, I’m not happy about making it thinner so I discarded that idea in favour of making it thicker, and therefore stronger.

I want to cut the pieces on the CNC router so that I have accurately cut, identical pieces, and since my router table is 1270mm x 1270mm square, I’ll not be able to cut a single side at a time as the entire case will be around 1800mm. The above drawing only goes as far as the start of the cabin whereas the case itself protrudes into the cockpit. But this section is certainly not so tall as the rest, so for the purposes of deciding how much plywood I need I only really need to find the tallest part of the case.

So that eliminates the 15mm thick plywood and I’ll have to cut shorter sections and glue them together. The choice between the three 5mm sheets and the two 8mm sheets comes down to the cost. Two sheets of 8mm ply will cost a total of £265.80 whereas three sheets of 5mm will cost £342.18, a significant difference.

There will be plywood to spare after cutting the case pieces out and these will be used to replace the bulkheads that reinforce the case.

These can be seen in the above photo. Cutting these away will destroy them no matter how careful I am, so these will be replaced. They have to be removed as otherwise I’ll not be able to cut the case away from the keel.

The next part of the decision making is how to laminate the pieces together. I’ll join the parts together lengthways using what is known as a puzzle joint since trying to cut a scarf joint in 8mm ply is far beyond my capabilities and as the sides of the case do not bend, a scarf joint would be an overkill. A simple butt joint would work but the puzzle joint increases the glueing surface greatly and that results in a much stronger joint.

Here is an example of a puzzle joint that I made when trying out cutting the joint on the CNC router.

And here is the joint put together. As you can see, it’s not only a very good fit but is self-locating in that it won’t pull apart even without any glue in the joint.

So, that takes care of joining the pieces together but laminating them is another issue. The join between the two laminates much be perfect. No skipped areas of glue and no voids and there is really only one way to do that for a hobbyist and that is a vacuum bag. You get a piece of plywood around 25mm or an inch thick that is flat and slightly bigger all round than the laminates which are glued together and pinned so that they don’t slide over each other You put the laminates on the thick flat piece, put the whole thing into a plastic bag and suck all the air out. This forces all the pieces together and since one of them is thick and flat and won’t bend whereas the others, which are thinner and will bend, the laminates are pressed against the flat bit and will also be flat once the glue dries.

That’s the hand-waving, brief description. You’ll see how it works when I get to that bit and take photos.

Anyway, for now the technical bit is done and I can proceed with the removal of the rest of the damaged case.

Time for a cup of tea.

I had some work to do on the CNC Laser after work and while that was running I decided to look at some of the pieces I removed from the top of the case yesterday.

This is one of them and exhibits one of the things that Charles Stock did consistently wrong when building and maintaining Shoal Waters. He used brass screws. You can see the result in this piece of wood quite clearly, the discoloured circles of wood around the places that the screws were put originally.

This is the view from the other side and you will see that either the screw is missing completely or the zinc has leached out of the brass leaving just copper. These copper fastenings need to be removed and the wood repaired before it is put back in place. Still, enough of that, it was time to move back to the centerplate case. Armed with a multitool with a sharp, fresh blade I set to.

This is the result, a hole in the starboard side of the case. I had to say that it was either a very sharp blade on the tool or it was distressingly easy to cut through the side of the case.

This is the section that I cut out viewed from the inside face.

Looking down the slot through the opening I could easily see the metal spacer and it was easy to fish out with just my fingers.

It is the spacer through which the pivot bolt passes and its purpose is to prevent the bolt from crushing the case inwards when it is tightened. Too loose and the water will get in as the seal is not good enough, but tight enough to stop the water ingress would also deform the sides of the case. But with this spacer in the way, that deformation is prevented.

Back in the workshop I took a closer look at the section of the case that I had just cut out. It is in very poor shape as you can see. This large flake of wood came off just using my fingers.

And this was cause by scraping the wood with a screwdriver. It’s totally rotten. The inner face of the case seems to have been coated with something, presumably to stop the steel plate from damaging the wood, but under that it is soft and fragile.

Looking at the end of the cut piece you can see the plywood that Tony glued to the outside of the case to reinforce it. This split away from the original casing when I prised the section out. Then there is a fairly intact middle layer of plywood and then the darker part that is the rotted plywood. It looks as though the sides of the case were made from two piece of plywood glued together with something like Aerolite glue and the inner face of the case covered with something, perhaps Aerolite glue again, as protection. Over the years the rot has gotten into the inner layer of plywood but has not been able to cross the glue barrier into the original outer layer of plywood except where close to the pivot bolt hole.

As a final task for today I took a screwdriver to the other side of the case and as you can see form the above photo, it too is severely compromised. The conclusion I draw from examination of the casing is that the rot has spread at least as far as the solid ends and will therefore need to be completely removed and replaced with a new case.

Now that I have the side of the case opened up I can see that this isn’t going to be such a difficult job as I had first thought. I will have to cut away the two side reinforcing bulkheads, which is mildly annoying but has to be done, before cutting the case as close to the keel as possible. The idea being that if I’m careful with the removal I should be able to use the removed case as a pattern for the new one.

We shall see.

I’m fairly confident, however, that if Tony Smith had not reinforced the case when he did then Shoal Waters would have sunk, either on her mooring or, more likely, when being sailed and the leverage of the water on the centerplate on the case cracked the case apart. Scary to think about.

Still, a new case made from high quality marine plywood from Robbins Timber will put her back into sailing condition for many years to come.

I just have to get on and do it.

Time for a cup of tea.

Time to start work on figuring out why the case is leaking and why the surveyor had concerns about the integrity of the wooden casing. This is what he wrote in his report, a copy of which I have been given:

On examination of the casing, there is no indication of leakage through into the bilge compartments of the vessel, all areas are seen well painted, dry and clean. The casing is found generally well fitted still and without obvious movement. There are no areas of soft timber that can be fully determined without further opening up.

However, soundings of the plywood cladding gave dull returns which are indicative of degraded timber that might exist within the original casing boards; beyond the thickness of the added plywood cladding.

We had already been advised by Tony Smith that there is a leak in the region of the centreboard case, it is just not obvious.

The first place to start is the removal of the two metal plates through which the pivot bolt passes. These are held in place by what turned out to be stainless steel screws which came out easily.

The plate itself had to be prised off and underneath the plate was a white sealant.

The same was found for the other side of the case. The wood under the sealant came off in layers like you would expect of plywood, except it seemed to be solid mahogany or similar. It did not come off easily and had to be removed with a chisel.

And that makes quite a mess !

I decided to take another look at what prevented the centreplate from being removed from under the hull by putting my camera on the case looking down through the slot. This is the result:

So, I had briefly entertained the notion that the issue with the case could be easily located and solved, but now that I’ve seen this obstruction more closely and noted the fact that it seems to have made a gauge on the inside of the case, I have not choice but to remove the starboard side of the case so that I can access this damage, asses and repair it.

If the damage was caused by the centerplate removal then I would not have expected so much damage to be caused unless, as I mention in the video, the wood was already soft i that area or possibly rotten.

I’ll cut away a section of the timber in that area, perhaps a foot wide and from the bottom of the case to the top of the side panel. This will give me a large enough area to see how far down the damage goes and will also allow me to examine the wood on the other side of the slot.

I’ll make the cut as carefully as possible in such a way that the replacement isn’t going to be an odd shape. Or no more odd than is normal for a boat, but that’s a task for another day.

Definitely time for a cup of tea.

From an engineering perspective there’s something about Shoal Waters’ road trailer that bothers me. In fact, I’d go as far as to say that it is at least bad practise if not just plain wrong.

Here’s the trailer put out of the way temporarily whilst I try to find space for it in the hay barn. Can you see what bother’s me?

Here’s a closer look at what I consider to be the problem. The cross beam is welded to the wrong side of the side beams. It’s underneath.

The intermediate beams are the same except that they are not welded but use U-Bolts. But they are underneath the side frame. See how rusted that U-Bolt has become? The weight of the hull is being taken but this and the other U-Bolts, not a good place to be.

The cross beam at the rear is also welded and also underneath.

So why do I consider this to be an issue? Simply put, the entire mass of the boat and the strain of it bouncing up and down as the boat is transported from A to B is on the welds and the U-Bolts. I would have designed this with the cross beams on the top of the side beams. In this case the welds would only serve to increase the rigidity of the frame and the U-Bolts would only be there to stop the beams from moving around on the frame. The weight and stresses would be taken by the beams directly.

Now I can see two reasons why this might have been designed this way. The first is that if the intermediate beams are put on top of the side beams, the the U-Bolts would be the other way up and the nuts and protruding bolts would sticking up, rather than down and that might be considered to be a hazard. Secondly, by placing the cross beams underneath, the height of the boat above the trailer is reduced by 60mm. Is that significant? I don’t really think so.

Still, whatever the reason for the design decision, I’m going to change it so that the beams are where I think they should be. I’ll not removed the welded beams, they are there to make the frame rigid but two new beams will be sourced and mounted close by them, but on the top of the side frames.

Now, this trailer is never going to be road worthy, it’s too rusted for that, but over the next few years a boat will be put on and taken off the trailer at least four times a year and I need to make that as painless as possible. That means a beam under the hull but over the trailer and wide enough to get the trailer out just be pulling it and not by going through the hassle we did previously. Right now, the boat is so low that this isn’t possible. By placing the offending cross beams on top of the side frame and by raising the rollers as high as they will go, there will be ample room to put the beam in place and thus create the required bridge. The down side is that Shoal Waters will be higher and thus slightly more difficult to get into. I’ll just have to lose some more weight and start stretching to increase my flexibility.

So that’s what I’ll do.

Obviously, photos and posts to follow as this progresses. Shoal Waters needs to be moved into shelter of the hay barn as soon as possible.

Time for a cup of tea.

Continuing on from the tasks of the morning, removing the centerplate was next.

The pivot bolt was removed from the case and the salt-encrusted rope cut off the plate itself and a thinner line attached, one that would go down through the centerplate slot with problems. However, the plate just would not drop out of the hull.

It came out this far and no further. In the end I decided that there was either a stone wedged in the case somewhere or the pivot was not just a bolt but a tube held in place by the bolt. Since the plate sounded as though it were being brought up some something metallic, the latter option seemed most likely. That left us with two options. The first was to lift the boat up another 1.5m or so to allow the plate to be taken out vertically, or it would have to be take out from the inside as is the case with Naiad. With Naiad I can easily remove the mast compression post so getting the plate out is just awkward due to the weight and size.

Lifting the boat any higher was just not practical, in fact, with the equipment I have it would be pretty much impossible. So the inside option was the next to be tried.

This is as far up into the cabin I could get the plate, it’s touching the roof at this point. However, by removing the back two covers of the case I could lean it forward and just move to enough to one side to clear the compression post and it slid out.

Then it was just a case of sliding it out of the cabin using a couple of foam mats so as not to damage the varnish in the cockpit.

Judging by the wear at the top of the slot, I would presume that this is the original centerplate made by Fairey back in 1963. It is in remarkable condition. There’s rust on the leading edge but nothing to cause concern, the only two areas that need attention are the worn slot and the worn hole at the top of the plate used to haul it up and down. Once it has been scrubbed a decision on whether it should be re-galvanised or painted with antifoul will be taken.

Here you can see where the two cover boards were removed. They were going to be take out anyway, so that’s not a problem and the screws holding them in place were stainless steel and came out easily.

Difficult to photograph but you can just see the pivot in the case. It may be held in place by the two metal plates screwed to the outside of the case. I’ll check that out another day.

Shoal Waters has been put back to bed ready for the next step.

The trailer was put into the hay barn as the forecast suggests that it might be wet for a few days and having it in the dry means that I can work on it without any hassle.

Time for a cup of tea.