The Subak is meant to be run on wind and muscle power. So, beside a series of tests on the sailing which are slowly moving forward (which involves moving not only forward but also somewhat towards the wind – tacking should be feasible!) we have also been looking at the muscle powered motion. There are two main systems we are interested in: good old fashioned rowing and the Yuloh. The Yuloh has been discussed previously and will come again soon. Today we have been working on the rowing.
From the wide world of online information, I have found that the inboard length of oars should be 55% of the distance between the rowlocks. Another importat fact that I can no longer find, but measured off a previous rowlock mounting, was the distance from the aft side of the seat/thwart to the rowlocks. We measured 33cm, which leaves enough room to not bash your knees with the handle of the oar. The leverage of the oar, i.e. the ratio of the length inboard to the length outboard, depends upon a number of factors. The oars we have been using have a ratio of around 2:5. This is good in the punt, which is tiny and light. It seems to be a bit heavy for the Subak. However the Subak is quite high (40 cm) from water level to the the rowlocks, so the oars need to have a length to reach to the water at an angle that is still comfortable to row at.
So we decided to get enough spare distance between the rowlocks by putting them on extenders outside the gunwhale. Angle steel was cut and welded, a tube mounted at right angles to make it vertical. Oops! This was a mistake. When rowing, it becomes clear that the rowlocks should be angled so that the oar passes straight through – the vertical orientation that we have means that the top part of the collar (that presses against the rowlock) was being squeezed through and getting overloaded and thus damaged.
Nevertheless, after mounting the outriggers and losing one drill bit to Poseidon in the process, a test row was made. Down the Winterhafen, a 400m stretch in 10.5 minutes (wind behind) and 12 minutes into the wind gives 2.1 kmh as a speed. With the Yuloh the same stretch took around 13 minutes (1.8 kmh = 1 knot). Both devices need some more work, but we are getting up to useful speeds. The Yuloh felt easier, the rowing felt like it used arm strength a lot more. Rowing seems more manouverable, but that is probably an experience issue.
But we definitely can say that the third attempt at rowlocks for the Subak has lead to success: they are pretty much in the right place!
The next step will be to look at new oars. The following diagram gives some ideas.
The diagram shows the position of the hulls, the planned inboard (loom) length (66cm) and the maximum allowable outboard length of 141cm. This gives us a ratio closer to 2:4 than 2:5 which will probably be more comfortable to row the heavy vessel. The two circles indicate the thighs of the rower, the looms clear their legs with some spare space. The rowlocks we have now have an internal diameter of around 5cm, but we might look at using thole pins and retaining cords that are more easily replaced. And at 15 Euro each, they are not the sort of things one wants to lose too often!
So we will soon report on oar making, but first we will get back with more yuloh experiments and development.