2020.03.27 - Stabilisation

The task I set myself for today was to finish levelling Naiad and to stabilise her so that getting onboard would not rock her around nor would it put undue strain on her keel.

I carefully measured the design waterline on the lines plan and found that the waterline at the stern is approximately 56 mm up from the bottom of the transom and at the bows, the cut water corresponded to a vertical line down from a line drawn across the bows 334 mm aft of the front of the stem.

Measuring the transom was easy and I used a piece of tape to mark the point I needed. The bows was a little more complicated. Firstly I measured back 334 mm from the stem and marked the spot with a piece of tape. Then I rested a straight piece of wood on the toe rail so that its centre was over the mark on the deck. I adjusted the angle as best possible by using a piece of string from the stem to each side of the boat where the wood touched the toe rail and once the distance was the same both sides I knew that the wood was perpendicular to the centreline.

I used a plumb bob to transfer the edge of the wood down to the ground on each side and put a screw into the ground as a marker. Then a second piece of wood was put onto the ground just touching the screws. Then I sighted along the top piece lining up the second piece and I could then see where the position of the cut water was on the hull and this was also marked with a piece of tape.

All I had to do now was to make sure that the two marks were level.

This is carried out using a water level. You get a long piece of clear tubing and fill it almost full with water. Then you hold one end of the tube against one of the marks such that the water level is at the same height as the mark. The other end of the tube is take to the other mark and the angle of the boat adjusted so the the water level at both ends of the tube aligns with both marks.

Here is the tube at the bows. The lower edge of the tape is there required mark here.

And here is the stern. Again the lower edge of the tape is the mark.

The red liquid in the tube is hot water with some red food colouring added since it is otherwise quite difficult to see the water level.

So that completed the first part of the task. The boat is now level fore and aft as well as athwartship. On to the second part of the task.

I add two supports under the boat up forward. These consist of two parts. A solid upper part and a lower part made from opposed wedges. You put them in the required position and then hammer the wedges together to jack up the support a little to take some strain.

Finally I cut two thick square pieces of wood and two long support to put under then stern as shown.

Although this does support the stern quite well, if for any reason the stern should lift a bit then the supports as shown fall away and have to be put back again. To complete the support I shall add some braces to join the two supports together and also more to prevent them from falling forward if the stern should lift.

But that is a task for another day.