Tuesday, February 19, 2013

Current jobs in the workshop include a Jim Michalak-designed Scram Pram I'm finishing off for a customer who has done a lot of work on the job already, but whose work commitments have prevented him from carrying out the final few jobs. See my previous post for photos. I have to say that this boat is very exciting and I look forward to the test sailing so that I can gain first-hand experience of the "Bird Watcher"concept.

Ian Hamilton's First Mate is nearing completion finally. The interior has been painted using a water-reducible linear polyurethane paint, and despite the difficulty in applying this sort of paint in very hot conditions (over the last month or so, the temperature inside my shed during the day has reached 43C/109.4F on many occasions), the end result has been very satisfactory. Properly applied, the paint ends up being as tough as the conventional two-pack polyurethanes, but has a pleasing subdued gloss which is appropriate for wooden boats, and the paint can be applied with much less concern about the dangers of VOCs (Volitile Organic Compounds). Brushes wash out in water, and as they say, you can drink the thinners (water!). I've used this sort of paint on many occasions in the past, and I can tell you that it is not easy to apply unless the conditions are perfect. However, if you follow the manufacturer's instructions to the letter, the end result is worth the effort.

Three Brothers. Ian's version will have the layout shown in the upper profile

As soon as either the Scram Pram or the First Mate has left the workshop, I'll be making a start on Three Brothers - this is also for Ian Hamilton. It is Ian's intention to use this boat on an extended journey along the Kimberley coast of Western Australia.

The intention with Three Brothers is to produce a boat which is simple and quick to build using the 'stitch-and-glue' construction method, and which will operate effectively in the semi-displacement mode. My aim was to get efficient running at a speed/length ratio of 2.2 which in the case of this boat means 10.5 knots or 12.1 mph. According to my calculations, with a reasonable load, this speed could be achieved with 15.6hp.

My performance predictions with 288kg (634lbs) passenger weight and 85kg (187lbs) for engine and fuel are as follows: -
·         Assume displacement of 820kg (1804 lbs) NOTE: This is for the performance calculations only. Displacement as shown in the drawings is 1191kg (2620 lbs) so the boat is capable of carrying significantly more than the 288kg (634lb) passenger load.

·         Salt water
·         LWL 22.6 ft
·         Power to achieve 10kts                                                           -           13.9hp
·         Power to achieve optimum SL ratio 2.2                              -           15.6hp
·         Speed with 30hp (Crouch’s Planing Speed Formula)             -           19.3kts
·         Speed with 40hp (Crouch’s Planing Speed Formula)             -           22.3kts
·         Speed with 50hp (Crouch’s Planing Speed Formula)             -           25kts
My choice of motor would be either:
·         18hp four-cycle outboard, giving a full-throttle fuel consumption of approximately 5.7 lt/hr (1.5 gal/hr);
·         30hp four-cycle outboard, giving a full-throttle fuel consumption of approximately 9.8 lt/hr (2.6 gal/hr);
·         30hp two-cycle outboard, giving a full-throttle fuel consumption of approximately 13.0 lt/hr ( 3.4 gal/hr), but with a weight and cost advantage.

      Due to the initial load that Ian thinks he will have to carry, he intends equipping his boat with a 50hp outboard, although this is still open to discussion.

      The construction of  Three Brothers will take place over about two years, as Ian needs to earn money to feed into the project, and I will only be able to devote a limited number of hours eack week due to other jobs.

      In addition to the building jobs mentioned, I have another First Mate to finish off, and three sets of plans to complete for publication.  The First Mate has been brought to a structurally complete hull stage by her owner, but changes to his work space mean that he must reluctantly pass the boat on to me for completion. However, he will do some work on her whenever he is able to get to my place.

      Plans for Whimbrel, Little Egret, and Fleet are all very close to publication stage, and in fact boats could be build using what is already available. However, I need to finish off some detail drawings and instructions before letting them loose.

Little Egret

     More information soon.


  1. Hi Ross- sounds like you have the same kind of work that I have- finishing off other people'd projects. I do like the "Whimbrel' plan - looks like something I have been thinking about. Can't tell how long it is from the scan, though.Looks like you are working on some interesting projects.

  2. Ross, you and Walter Baron (Old Wharf Dory) must be the two most productive work-alone boatbuilders I've ever seen. And I never cease admiring the work of each of you.

    I like the Wimbrel too, a lot.

    And isn't that a slick paint job on Fleet?

    Rich H.