A mini-journey: Tiny (part VI)

I had some other topics that took most of attention the first half of the summer, the national dance fest (see a speedrun video from above by Postimees, or the full concert by ERR). Followed by FOSS4G Europe 2025 in Mostar, Bosnia-Herzegovina. So it was only the end of July that I was able to redirect my attention back to the boat-at-hand.

I would like to arrive at laying down at least half of the decking before the building season finishes this year - so if the striped and sideways-stacked plywood idea does not work I’ll have time over the winter to come up with something else. But in order to close the deck, I’ll need to install the amidship seat. But before I can fix the seat I’ll have to saw a hole in the bottom of the boat for the centerboard. And before I cn do that I’ll need to prepare and fix the keel on the outside bottom

So, the centerboard… it’s essentially a fin you can put in/pull out through a slit in the bottom of the hull. Tiny’s plans call for an open box (or trunk, or case) that’s integrated into the bench, with the centerboard itself uhm… “operated” from the inside by hand, no fancy hide in the hull mechanisms.

For building and installing this I’ll need two things:

• to build a “box” that will serve as the casing (plus as the seat support) for the centerboard. This will have to fit tigthly to the bottom as it will be partly in water, because
• to install it I need to saw a slit in the bottom of the hull through the keel (on the outside) and keelson on the inside…

Since cutting a hole in the bottom of a solid and (hopefully) watertight hull seems like a very dramatic act, I’ll start with building the box first. Incidentally, a ready box will also help to determine the exact location for the slit in the hull bottom. So I started with drawing the full size pattern of the lateral side

This will help to measure the exact amount of scrap material I have left and will later guide with sawing the correct angles and sizes after assembly. I found a few scrap pieces of rough cut 10cm wide planks which I planed down to about the same thickness and width. Since the final box’s height is about 24cm, one of the planks also needed to be cut in half length-wise. I figured the extra cm does not play much role here, as I will get rid of it during assembly to the hull anyway…

Because now looking at the original plans again - one thing that I had absolutely overlooked when making the hull itself two years ago, part of the bottom was supposed to be flat / straight, just exctly where the centerboard box was supposed to go.

But anyway, the planks were then laminated side-by-side.

Before assemblying the box itself together I fiberglassed both sides of the box side-pieces which was preceded by sanding everything down and cutting the sides to the final angles too. At a later thought I should have also painted the insides before putting the box together - it would have been way easier. Now I’ll have to squeeze myself in there with a long-necked roller-brush instead.

At the same time as the box epoxy was curing I had time to work on preparing and installing the keel on the hull outside bottom. As the centerboard slit will go straight through the keel it will have to be in place before I start cutting it into the bottom. The keel material is a salvaged piece of weatherboard, which had to be cut and planed to rectangular cross-section.

It did take some (re-)measurements to align the (new) keel on the outside with the (existing) keelson on the inside (more-or-less), but in the end had to keep my fingers crossed that the measurements are correct and what’s the middle of the boat (keelson) on the inside boat-width-wise is also the middle on the outside so the centerboard slit will be in the center and straight.

Moving back on the hull inside and getting ready to install the centerboard box. This needed the temporary seat to be removed, but to keep the pressure on the hull sides plus have a way of marking the centerline somewhere up in the air I placed a temporary cross-support at the location where the centerboard box upper aft corner would be. This made it also easy to align the centerlines.

Ok, so now the next thing would be to get the box bottom cut to shape so it would fit tightly to the hull bottom. As I wrote before, this is not as simple as doing a straight edge/line cut because of the hull bottom curvature. This will somehow have to be transformed to the box side (on both sides). It could/should be taken off the plans, but as real life might be something else then I decided to use a clever instrument - a pen attached to piece of 1cm thick scrap wood. Running it smoothly and flat against the keelson will copy the needed curve on the box side.

I then used this markup line to plane the centerboard bottom down to the curve of the keelson where it will be installed. But now there was another problem - how do you mark the slit location on the hull? It should pretty much match the box opening location. Of course! Templating again - draw the box bottom template, transfer it to the correct location by the box outer edges, and we have the exact slit location marked down on the keelson.

If you want to be sub-millimeter exact, then use plywood for templating instead of paper. I figured that building paper is enough for me because my precision sawing will anyway in all probability be worse than the accuraccy that I get from using plywood.

.. and now the dramatic part.

I think this took about half a day of measuring and remeasuring and having another cup of coffee “before I really start” and then going over the checklist to see if I have everything covered, again… and again.

My main worry was that before I can go handsawing, I will need to make the first cut with the circular saw. But for that I will need to somehow make sure that when I press down on the circular saw it will in fact go parallel to the keelson length-wise. To make sure this is the case I built a right-angled guide on top of the keelson - a few scraps of wood fixed with clamps. If I now place the foot of the circular saw dead flat against the perpendicular guide I can be sure that the cut will be nicely parallel. Now it’s only a matter of getting the correct location keelson-width wise to start the saw.

I ended up sawing most of the slit cutlines with the circular saw - only the ends which are at an angle were hand-sawn. The ends of the slit were cleared with a large enough drill-bit and then fine-tuned with a chisel.

Having turned the hull over, to my astonishment, the slit was nicely in the middle of the keel too. So after some minor cleaning up, the drama was over.

Next up were the centerboard box cleats which fix the box more securely to the hull. I ended up laminating them out of 1*2cm battens on either side of the box. Using the box itself as a guide it was relatively easy to get them into place.

Come to think of it now as I’m writing this down I cannot remember what was the reasoning why I did not install the box itself in the same go, but instead opted to take it out after cleats were securely fastened in place and the epoxy cured so I could clean the slot. But anyway, the next job was to fix the box to the hull. The side cleats were already there but at a spur of the moment I decided to add extra cleats to the fore and aft sides of the box aswell.

With the seat risers there was more measuring and re-measuring, and on-the-spot fixing of the parts that are attched to the hull. With the risers that are fixed to the centerboard box, it’s fairly straight-forward - these go flush with the top side of the box. The hull side ones need more attention so that their position is at the same height as the center ones. It took a couple of tries to get them sorted out but finally got them fixed too.

For the seat planking itself I’ve been thinking for some time that I’d like to try if I can use “free-hand-sawing”. That is - saw to planks at a non-straight edge line but in a way that they would still fit together tightly side by side. I found a few unedged planks in the shed which is a good way to test how it could be done. The idea I had was to stack the two neighbouring planks one on top the other with a bit of overlap, fix them with clamps and then with the circular saw just saw them lengthwise so the seam would be the same shape, however it comes out with no marking line to follow.

The first cut I was hesitant about the outcome, but it really seemed to turn out nicely so I did the rest aswell in the same manner.

Using again the template for the seat I took before, I rough cut the planks into correct dimension so they would fit in their respective location. Only then did I do the final cuts to see how the seat would look like, and I have to say I like it. Maybe I’ll even try and emphasize the seams by carving slight ditches into them and filling them with darker putty before varnishing the whole seat with clearcoat.

But the seat installation will have to wait because suddenly I realized that if I want to paint anything then now is the perfect opportunity to do it on the inside before the seat or decking start restricting access. So I’m off to the paint-shop as it will take some time for the delivery to arrive and I can spend a few days final-cleaning up the inside on the hull, install tougher supports for oarlocks, and bevel and install two battens - one at either side of the keelson (which would not have been necessary if I had paid a bit more attention when fixing the keelson to the hull in May) - before the paintworks can begin.