We last saw the centre board after it had received its lead ballast back in February, which by the way filled the aperture and its re-machined rebate very nicely.
I next removed the scrap ply backing pad, which held the lead in place during the pour.
You can see how the molten lead charred the ply pad. It bubbled and smoked wonderfully, as it did in the keel.
I used a Bahco scraper to fair both sides to a flat surface.
Next I filled the low spots on both sides with thickened epoxy.
And I then sanded both sides of the ballast to a smooth, flat surface, like this.
Then it was time to shape the edges of the board to a streamlined profile.
First I sprung a strip of thin ply to a fair curve along the trailing edge of the board, taking the line from the drawings. Like this.
Then I used the big Festool sander to shape the board to the profile indicated on the drawings. This was the result.
The leading edge now has a bullet-nosed profile, and the trailing edge has a long taper down to a thin edge. This will slide through the water nicely.
You can see that the edges are protected by epoxy armour which I added to a rebate cut around the edges of the board way back at the beginning of the build. Removal of material during the shaping has revealed the armour, especially on the trailing edge.
With hindsight I don't think the sander was the best choice of tool to do this. The board got pretty hot and I was concerned that the heat might damage the epoxy, but it seemed fine when it had cooled down. If I were to do it again I would use a plane and just finish with the sander.
After shaping I applied fibreglass cloth to both sides of the board. Here is the starboard side with its 'glass, curing.
The drawings say to wrap the cloth around the leading edge at this stage, but mine resolutely refused to stay in place.
So instead I added a strip to the leading edge when I was 'glassing out the bottom of the hull interior, like this.
Prior to this I had recoated the board to fill the weave of the 'glass cloth, and sanded it.
The board is nearly complete. It needs a couple more coats of clear resin and to be sanded to a very fine finish.
The manual says to leave it like this, as do other builders, but I am pretty well decided that I will paint it the same colour as the hull.
Others say that no one will ever see it, but it's actually really easy to see the keel or the board of a boat sailing in clear water. And I think as it is this board is not very pretty!
So it will end up being dark blue.
Confident that I now knew how to cut 'glass cloth panels correctly I cut them all out in one session and set them carefully aside to deploy as and when required.
The cloth has to be handled gently and kept from dragging against anything rough which instantly pulls threads. Damaged cloth not only looks unsightly but can be difficult to smooth and wet out nicely.
Installation of the rest of the 'glass panels progressed well and they were all wetted out over the course of four or five days and left to cure.
Here is the starboard panel in bay 7, laid in place and ready for wetting out.
And here is the port panel in bay 2, laid in place and ready for wetting out with clear resin.
The 'glass cloth is actually very compliant provided that I am patient and gentle. It conforms well to the shape of the hull and the fillets and doesn't mind being stretched or pulled slightly to get a good fit.
In bay 1 the steep sides of the bow compartment meant that I had to use a small piece of masking tape to hold it in place while I wetted it out, as here.
And here it is after application of clear resin.
I found that a 4" roller was the ideal tool for wetting out, and a brush was sometimes useful for tamping down the cloth into a fillet or a corner.
I started wetting out in the middle of each panel and worked slowly but firmly out to the edges. On steep sided bays it helps enormously to work up to the top of the panel first. This holds it firmly in place while the rest of the panel is dealt with, otherwise the top just falls down onto the wetted cloth and gets in a right mess.
Brushes are no use whatsoever for applying resin to cloth - they just drag the cloth or pull threads loose.
Here we see several completed bays on the starboard side of the boat.
The very last panel to be installed was the starboard side in the bow compartment of bay 1.
Here it is after wetting out.
And that is almost the end of 'glassing the bottom of the boat! When the bow panels are fully cured I will sand them and add a strip of 'glass tape all the way up the stem and along both chines as required by the build manual, and that will be the end of this activity.
I must say that I have really enjoyed this phase. Well, let's face it - after the endless agony of sanding fillets pretty much anything would be fun!
Next we move on to sanding the 'glass and applying more clear resin to get a perfectly smooth surface, ready for paint. I can't wait to get the sanders out again ...
With all the fillets in place it was time to start adding a fibreglass cloth covering to the bottom panels of the hull, for added strength and resilience.
I started with the port side of bay 9 in the stern, between bulkhead 8 and the transom. This will be sealed as a watertight compartment and not visible, so it is a good place to practice in case the outcome is not cosmetically perfect!
I cut 'glass cloth using the pattern I created earlier, and wetted it out. This was the result.
I thought it looked pretty good, so I moved on to the port side of bay 8. That went well too. Here it is, wetted out.
Flushed with success and confidence I then tackled the port side of bay 3, which is a much more complex shape with overlaps onto floor 3 and bulkhead 2 and the adjacent bay. Using the paper pattern to cut the cloth I managed to make an incorrectly shaped panel which did not fit the bay - twice!
I realised that the 'glass cloth was deforming as I cut around the pattern, being much more flexible and pliable than the paper. This was clearly not the right way to do it ...
So, I carefully smoothed out the fabric and placed the pattern on top. Two folding tables placed together provided a suitable work surface.
Then I weighted the pattern down, so that neither the pattern nor the cloth could move. Like this.
I recruited two stuffed chicken doorstops to assist. They are perfect for the job, and they didn't seem to mind helping out …
The trick then is not to cut around the pattern but to mark out the outline of the panel on the cloth itself. I used a marker pen to make a dot every two or three inches about a quarter of an inch from the edge of the pattern. Then I cut along a line inside the dots, knowing that the outcome would be correct even if the cloth was deformed in the process.
It worked perfectly. Here is the end result.
So far, so good!
I mentioned in a previous post that I thought it would be necessary to overlap the fibreglass covering on the bottom panels of the hull up onto the sides of the centre board case. Advice from others and a closer look at the build manual confirmed that this is indeed a requirement.
When creating the epoxy resin fillets along all the hull panel joints I neglected for some reason to add fillets where the keelson and the centre board case are joined. It is in fact obvious that fillets are required on this join, otherwise it would not be possible to have an overlap of fibreglass cloth from the bottom panels up onto the case itself, since the cloth will only conform to a flat or a curved surface - sharp turns are not possible.
So … more fillets were called for! Readers of previous posts will know how much I enjoyed making and then sanding the hull fillets i.e. not at all, so it was a bit galling to realise there was more to come.
However, by this stage I was fairly proficient at making and shaping fillets, so it was no great hardship to create six more - three on each side of the centre board case.
Here they are, after creation.
And here they are after shaping and sanding.
While I was at it, and having some filleting material left over, I ran a small fillet up the join between the case and bulkhead 7. I will tidy this up later.
The next job is to add fibreglass to the bottom panels. A nice change from sanding fillets!
While I was waiting for the reworked fillets to fully cure I decided to invest some time in making patterns for the fibreglass cloth panels which would soon be required for the interior of the bottom of the hull.
There are nine 'bays' in the bottom of the boat. Each requires a layer of fibreglass cloth to be applied port and starboard, overlapping up the sides and across the keelson and over each other to maximise the strength of the hull.
First I measured each bay and made a scale drawing of the pattern for one half of each bay, including the overlaps.
Here is the drawing for bay 3, which lies between bulkhead 2 and floor 3.
Then I marked out the patterns full size on sheet paper. I used thin paper so that it would conform easily to the shape of the hull.
I cut out all the patterns and test fitted them in the hull, as here.
The next step will be to use the patterns to cut 'glass cloth panels. I will most likely do this inside the house, where I can place two or three folding tables together for the work surface. There isn't sufficient room in the workshop.
Right now I'm enjoying a short break after finishing the fillets, although it has now occurred to me that I might have to add more fillets along the join of the keelson and the centre board case if I decide to run an overlap of cloth up onto the side of the case.
That would be tedious, to say the least! But as I consider the options, it seems inevitable …
In the previous post I said that I was not happy with the quality of my workmanship, and that some of the fillets would need rework. There was no question about it. If the boat was to be strong and attractive, more sanding misery was required.
So, I spent some time deciding which fillets needed to be improved and made a work list.
The first thing I did was to tape out the keelson fillets, like this.
I should have done this in the first place, to achieve wide, shallow and neat fillets.
Then I set about reworking all the items on my list. By now I had become relatively expert at filleting and it only took three days to carry out all the remedial activity.
Another six days of dressing and sanding followed before I declared myself content with the size, strength and appearance of all the fillets.
At last, the agony was at an end. It felt like I had been working on these fillets for months but when I checked my log I found that the entire exercise had taken just over five weeks. I don't think that is a bad investment of time, given the importance of strong joints.
The next step is applying fibreglass to the interior bottom panels of the hull. It will be a very welcome change!
I have to admit that I became very despondent when faced with the task of sanding the fillets to a smooth curve. It was no surprise. I knew it was coming but I was still downhearted at the prospect of spending hours and hours scratching away at rock hard epoxy.
I made a half hearted attempt to begin sanding, using a piece of pipe insulation as a sanding block, and it barely scratched the surface. A crisis of motivation had set in.
I had read on one builder's blog that he was so demotivated by the prospect of sanding that he only managed one hour's work in the four weeks following completion of the fillets. I could easily empathise.
So I did nothing for a couple of days. While pondering how to find the energy to get going again it struck me that professional finishers must face this challenge every day, and they certainly don't do it by hand!
So I did some Googling and I discovered carbide burrs. A carbide burr is an industrial abrasive head mounted on an arbour for use in stationary or hand held grinding tools, for the purpose of deburring, shaping and finishing hard materials. A diamond cut burr will shape stainless steel and titanium, so it will handle epoxy with no difficulty.
I decided that a ball shaped burr would be best, and purchased one with a 16mm diameter - the largest I could find. Here it is.
A trial run with it fitted in my little DIY Bosch cordless drill worked quite well, but it quickly depleted the battery and the drill did not have the necessary grunt to drive the burr at the high speed which it needs to be effective.
My cordless professional DeWalt drill is too big and heavy for use inside the boat, but luckily I had a third, small corded drill languishing in a drawer from many years ago. It is an ancient Bosch, so old it even has a chuck key! Here it is, with the burr fitted.
It is powerful (400W) but is small enough and light enough to use inside tight spaces, and it proved ideal for dressing the fillets. It took four days to do the entire boat. The poor old Bosch got a bit tired after several hours of continuous use, but it held out.
I had removed the sharp and lumpy surface of the fillets, but they would still need to be sanded to a smooth finish - especially where they are visible. But I was happy to have otherwise saved a huge amount of work.
This is where I made my second discovery. I called the burr vendor to ask how long the burr will last, and in conversation he suggested that I consider SpiraBands. I had never heard of them, but I had a look and they seemed to be just what I needed to finish the fillets.
Again, they are industrial abrasives. They are cloth-backed sandpaper cylinders which slide onto a rubber holder mounted on an arbour for stationary or hand held use - ideal for use in an electric drill. They come in various lengths and diameters, although the choice of grits is quite limited - mostly coarse. I purchased a selection of sizes - 60, 30, 20, 15 and 10mm diameters.
This is what they look like.
So then I went to work with the SpiraBands to smooth the fillets. Like the burr, they worked really well. I soon found that these abrasives work best on epoxy at low to medium speed, so I used my little variable speed Bosch cordless drill. The abrasives are much more controllable at low speed. As previously mentioned the battery only lasted ten or fifteen minutes, so I purchased two spares and by keeping them fully charged at all times I was able to work without interruption.
In practice I found that I used all the diameters, depending on the size and angle of the fillet. The big 60mm was ideal for the wide and shallow chine fillet, which is why I purchased that size.
The final stage was to hand finish the fillets with P80 grit aluminium oxide sandpaper, which I now buy in 50 metre rolls because I use so much of it. That way it works out really inexpensive.
The pipe insulation made quite a good sanding block for the chines but all the other fillets required much narrower blocks. I found that thick cardboard folded into double and triple thicknesses made ideal sanding blocks, offering a solid edge but being slightly flexible they could adapt to the curve of the fillets. A cork block was useful too.
All this sanding took what seemed like an eternity, and I have to tell you that it was mostly abject misery.
Truly, I thought, we have entered the vale of tears.
Other builders told me to keep going, and that once the fillets and fibreglass are completed the build gets back to being fun again.
So I kept the faith and soldiered on until I had sanded the very last fillet. This whole process took two weeks.
Theoretically I should have been ecstatic, marking the occasion with a celebratory glass of something cold, but alas I was only too well aware of an uncomfortable truth … I was not happy with the quality of some of my fillets.
The bottom fillets in the stern compartment were not big enough, and needed to be beefed up quite a lot. They were the first ones I made, and I was over optimistic about how much epoxy would be required.
The same applied to the fillets in what I would normally call the stem of the boat, at the very front. Not big enough or strong enough to take serious punishment if something hit the bow.
And all the keelson fillets were not good enough. They were too thin and patchy, and quite frankly not neat enough!
And here and there around the boat were incomplete or scruffy bits of fillet, which needed remedial work.
There was no doubt that I had a lot more work to do to make the fillets fit for purpose, and that we were still very much stuck in this vale of tears …
