Archive for August, 2009
Mannequins 4 Sail by Harry Manko
Here is a fun fact for those out there who need to shape an object so as to have a smooth elliptical cross section throughout, and lack detailed plans or templates. To make the Ulus’s ama, the shape of the elevation view is given by a table of offsets that one uses to create the plywood sheerweb, and the planview shape is laid out by hand using mainly one’s eye aided by some long battens. I did some rough scaling from a rendering in the plans, but no dimensions were available. At each station along the length of the ama there is thus defined a rectangular cross section into which fits the the curved cross section of the final shape.
But how to actually form the shape so that it will not be un-fair? I decided that an elliptical cross-section throughout would be simplest. The best approach is to first shape the rectangular lofted solid into a octagonal lofted solid, and then take it from there. This is how round spars and oar looms are made. With a little geometry I figured out that for an ellipse incribed in a rectange, the sides of the enclosing octagon lying on the original rectangle sides are 1/(1 + √2) ≈ 0.414 times the length of the corresponding rectangle side. So for many stations along the length of the ama we measured these distances and then used battens and string lines to mark the foam ama core preparatory for final shaping with handsaws and sanding boards. It’s turning out pretty well, as you will seen in the next update.
Temerity Racing went for a practice sail on Sunday August 9, circumnavigating Angel Island clockwise. Wind was WSW 24 kts gusting to 30 kts in the Slot, and we had our hands more than full with a single-reefed main and 95% #3 jib up. At times control was non-existant during gusts, as the helm loaded up and there was no one available with the physical strength to trim the main. Two fishing boats and the mid-bay #7 red channel marker nearly felt our wrath as we rounded up on them. Good practice for the Sarcoma Cup though, as conditions that day (especially the white-knuckle ride home from Richmond) were nearly identical. We had good intentions about getting in some spin practice as well, and gave the 3/4 oz a good soaking in its bag in the bow, but were too tired by the time we got back to calmer waters.
Location: 68.38. 06N 109.37.05W
Wind: 8 – 10 Kts Westerly.
Cloudy. Light rain.
20 August, 2009
We finished early yesterday after struggling in frustrating winds, and having suffered the expectation of forecasted favourable conditions. Once landed, we scrambled up an 800ft escarpment in the vain hope of finding a radar station manned. Although there was no one present, we enjoyed incredible views from the top. We returned to the boat for a sociable dinner with French wine given to us by Phillipe. The wine was probably more chilled than Phillipe had intended and sadly we only had each other for company! We woke at 0430 to west winds but struggled with inflatable rollers to get the boat afloat as low tide thwarted our departure. We succeeded and we are now making good speed. We’ve got about 100 miles to go to Cambridge Bay, so should arrive late Friday/early Saturday.
Two Royal Marines, Kevin Oliver and Tony Lancashire, are right now making Canada’s Northwest Passage, sailing, rowing, and at times dragging their Norseboat 17.5 sail/row cruiser thousands of miles to raise awareness and money for the UK charity Toe in the Water, a group which “aims to inspire the men and women who have sustained often traumatic injuries, including the loss of limbs, to move beyond their disability and to become re-inspired by life.”
Good luck and fair winds!
Race site here.
Angel Island (west side), San Francisco Bay, California
23 August 2009
2009-08-23 02:16 PDT 5.47 feet High Tide
2009-08-23 06:32 PDT Sunrise
2009-08-23 08:15 PDT 0.72 feet Low Tide
2009-08-23 10:24 PDT Moonrise
2009-08-23 14:48 PDT 5.95 feet High Tide
2009-08-23 19:51 PDT Sunset
2009-08-23 20:59 PDT 0.72 feet Low Tide
2009-08-23 21:28 PDT Moonset
Continue reading ‘Sarcoma Cup Currents’
Progress on the Ulua has been pretty slow of late, with our attention given over to Temerity and lots of other family activities. I’ve also been procrastinating badly with regard to fitting out the interior. There has been some work done though on some of the auxilliary parts.
I covered starting the inwales in my last real post. They are now glued in. The outwales are also fabricated and waiting.
I had a lumber mill cut the planks for the ‘iakos from very thick African mahogonay and ash stock. They really grumbled about doing the hardwood work, they seemed to think it was bad for their saw. The results were very good, though, and I don’t think I could have done it myself on my cheap table saw.
Laminating an ‘iako. I had thought to do more of traditioinal Hawai’ian double-bend, but wasn’t sure how much it would spring back after gluing, so I went with the simple bend called for in the plans.
While I was in laminating mode, I decided to do the main section of the boom as well. I had a lovely 18′ length of 3/4″ fir, and I ripped two planks out of it and laminated on a jig (again built on the strongback). The boom-jaws still need to be made up and fitted.
I had purchased two blocks (4′ x 8′ x 4″) of yellow (probably the ‘bad’ kind) of urethane foam, and these had been taking up a lot of space for over a year. I was also worried that they would be damaged by light. As it turned out, they were already warped somewhat from just sitting on their edges. So I decided to make up the ama as a little side project.
Above: lofting the profile shape of the ama on a scarfed-up piece of 3/16″ ply. I scarfed two 2′ x 8′ sections with fiberglass reinforcing of the joint, which may have been overkill. The bow profile is left square as it will be hand shaped in the end.