The PBO team fits the anchor well, frames, fore-and-aft pieces, cockpit seats and foredeck beam to the Secret 20 – while making sure everything is properly aligned
The previous article in this series (Part 2: Birth of a boat – truing stem and stern) saw the keel set up with stem and sternpost – and not much in between. Since then, we’ve made what looks like excellent progress – leaving us with something relatively boat-shaped. But that’s getting ahead of ourselves. How did we get to that point?
See the full set of articles: Building the Secret 20 kit boat with PBO.
A month of sawing, sanding, planing, chiselling and fettling – and things are looking good. However, we deviated slightly from the (admittedly sparse) instructions. These suggest installing each frame as it is cut out, slotting everything together as you go. However, as we dry-fitted each piece the Secret became more and more rigid, each piece taking out some of the uncertainty that could lead to misalignment.
So, with a little trepidation, we decided to dry-fit the whole kit, align it and then glue everything together. That’s quite a task, but after much discussion (and tea) we decided that it would not only save a bit of time but also lead to a better-aligned boat at the end of it.
The only problem would be that there was a lot of aligning to do… and a massive gluing job at the end of it.
Cutting out the frames
Our kit delivery came with sheets of 9mm marine ply, with the frames partially cut out with a router. The frame of the Secret is designed to slot together with pre-cut tabs, so making sure that the frames were as accurately cut as possible was vital to ensure the kit went together.
The frames were cut out using a jigsaw – and to make sure we cut the right part, we carefully marked each cut line with a pencil. Next, the cuts were tidied up with a sharp block plane. Any ‘feathering’ that remained after the routing process had to be sanded off.
Some tabs needed shaping correctly. To do this, we made a cardboard template of the opposite side and transferred it to the plywood before cutting out with a jigsaw.
With the frames cut out one by one, we could try installing them on the keel. They lock into pre-cut slots on the keel – but these needed easing with a chisel to make them wide enough to fit. We also needed to square off the ends of the cut-outs in the frames to ensure the frames fitted fully down onto the keel.
We worked from forward to aft, cutting out each frame in turn, fettling it and fitting it to the keel before moving on to the next one. It was really important to make sure they fitted well enough to locate properly, or else the shape of the boat would be affected.
The instructions suggested epoxying in the frames individually before adding the fore-and-aft braces. However, we came to the conclusion that it would be sensible to add the fore-and-aft sections, as well as the bunk tops, in order to keep everything braced well – so we took the plunge and decided to dry-fit all the pieces first, brace up and then glue it in stages with everything in place.
Installing the anchor well
The first thing to install was the anchor well base. Made up of two halves, this slotted into frames one and two and a notch on the stem, and stiffened up the first few frames nicely. We cut battens to support the anchor well base, dropping the outside edges of the well to assist it to drain. These could then be glued in, which helps support the stem, forefoot and first frames.
Fore-and-aft sections fit below the bunks in the cabin, holding the frames at 90° to the keel, adding rigidity to the structure, helping to shape the boat’s bottom and extending up to cockpit seat level at their aft ends. These were cut out and slotted in.
Next up, the cockpit sides, which do much the same job further aft, slot into frames 7-9, stiffening everything up and forming the cockpit well. The aft ends push through slots in the final frame (10) and form the beginnings of the counter and the structure that will support the transom and aft deck. These two fore-and-aft sections will later be glued together, so we joined them with temporary screws and plywood pads to help everything align properly. The slots into frame 10 needed a lot of easing before the pieces would sit happily and at the right angle.
Now we could work on the cockpit seats. In two pieces each side, these slot through frame 10 and add to the counter/transom structure. The forward piece forms the cockpit seats, and a long shelf inside the cabin. These had the effect of pulling all the frames into position and holding everything much more rigidly.
The final part of the structure was to install the bunks. Even though we won’t glue these in yet we felt it was important to have them in place to ensure correct alignment of everything else. They were cut out as above, and posted through frames 3 and 4 to create the base of the diminutive double bunk in the cabin.
The slots in these needed careful adjustment to ensure correct alignment – especially as they tended to pull the frames out of alignment before everything fitted properly. Eventually, everything fitted well and we could fix them down with temporary screws to keep them aligned while the glue sets on the other sections.
Now came the most important part of the job – making sure everything lined up. (See previous article’s comment about circular battleships!) The first step was to make sure each frame was aligned and level – these set the shape of the hull, so were particularly important to get right. To do this, we used a long spirit level placed across the top of each frame, with a smaller one added lower down if possible to add another level of calibration.
Once each frame was level, we held it and added a ‘leg’ support on each side to keep it there and stop any twist creeping in as we straightened up the rest of the boat. In this way we levelled up a frame at a time, working aft and installing legs to take out any twist. It was remarkable to see the whole boat, which had been quite twisted when dry-fitted, straighten out and level up, and all the pieces began to fit much better.
Once we’d added leg supports to each frame, we could move on to the fore-and-aft pieces of the frame. Some of these were applying a lot of tension to the frames and each other, and were dictating the shape of the boat – so we needed to ease their slots to enable the boat to settle to a comfortable and fair shape. To do this we used a sharp tenon saw and ¼in chisel to lengthen some slots where required – the shelves in the cabin and the cockpit seats needed quite a lot of easing to help them lie flat. On others, the slots needed widening, and we found that a Japanese saw of the type that cuts on the ‘pull’ stroke was ideal. This could be run down the offending slot to widen it and allow the whole boat to ‘breathe’.
The next part of the alignment process was to ensure that each frame was upright. We employed another spirit level for this, and used temporary screws to pull each edge in where necessary and to temporarily join athwartships and fore-and-aft panels where necessary.
You may remember that we installed a laser level on the sternpost in the previous feature. Now came its time to shine, quite literally. The level’s spread beam, set up perfectly vertically, would allow us to carefully align each frame. We set it up so that it was shining vertically on the stem and first frame (fixed in place last month), and so that it also shone perfectly down the middle of the final frame.
With first and last set up correctly, we could be fairly sure that the boat was straight – but we double-checked by assessing where the beam shone on each intermediate frame, too – and after some fine-tuning we got it matching the centreline on all frames, as well as central in the slot in the keel deadwood and on the stem as well.
This combination of the laser level’s line, a long spirit level on each frame and a short level to ensure that each frame was vertical gave us a good an indication as we could get that the boat was as true as possible.
We decided to cut and fit the foredeck beam as another safeguard against the first three frames ‘twisting’ or losing alignment. The beam is made up of two timbers laminated together. These we screwed together temporarily, before using a jack plane to straighten and smooth the edges.
This done, we rounded off the underside of the beam before dry-fitting it – and to our relief it aligned the necessary frames.
The beam must slot into a rebate where it meets the stem. We marked this up, and then used a Japanese saw to cut the edges of the slot, before a ½in chisel took away the waste with the assistance of a mallet.
Tidied up with a chisel, we were left with a neat slot for the front of the beam, which could then be laminated together with epoxy. As a final check, we used the laser level to ensure that the beam was straight and aligned fore-and-aft and central in the boat – and to our relief, everything lined up!
Each frame is designed to be attached to the keel with an epoxy fillet for strength. That done, all the joins between fore-and-aft and athwartships frames must be filleted. That’s a lot of fillets! See the next article for a guide on how to make perfect fillets.
With Hamish Cook from Wessex Resins’ advice ringing in our ears, we set to work. We decided to be sensible and not attempt to glue everything at once, so we started by adding fillets where the frames meet the keel. One disadvantage of our method of keeping everything dry-fitted in situ is that some crawling around on the floor is necessary – but we still reckon it’s a sensible move.
So, one month into the project we’ve got something that looks like a boat. The Secret’s lovely lines are beginning to show… all we have to do is make a couple of hundred fillets and we’ll be able to move on to installing stringers!
Read Part 4: How to make the perfect epoxy fillet
As published in the December 2016 issue of Practical Boat Owner magazine.