Since November 09 I've been distracted by my physical condition which has affected my wrists and hands.
I've also been very busy at the Rawene Hospital solving problems.
My outboard motor now has the Dierking foil fitted and I've ordered a new 7.1/4'x 5'' prop which arrives next week. (It's a Yamaha prop)
A funny thing about the New Zealand importers of Sail Outboards. When I made an enquiry about a replacement prop they tell me the manufacturers never made a long shaft 2,5 Hp 4 stroke outboard!
The outboard motor catalogue published in a recent NZ Boating Magazine lists 2 prop sizes for a Sail brand 2.5 Hp, 7,1/4"x5" and 7,1/4"x8". They tell me they've never stocked a 5" pitch prop either.
I wonder how my long shaft came into existence? Perhaps it's a figment of my imagination. I've posted some pictures of it, can you see it? It measures 19" from the bracket hook to the bottom plate.
Even the Sail brochure/ hand book that it came with says "Long Shaft, Barge Model 4 stroke, 2,5 Hp."!
Has anyone else got one / seen one or am I alone in the world?
Please let me know.
The reason for the foil is to reduce drag and turbulence around the surface piercing shaft. When unchecked the turbulence allows air to make its way down the trailing edge of the leg causing the propeller to cavatate or loose laminar flow over the blade, thereby reducing thrust.
The foil mitigates this problem increasing motor efficiency by a large factor.
Outboard motors are designed to sit behind a transom so the manufacturers only create a foil for the immersed section of the stern leg. The proa presents the unique problem of a surface piercing outboard which this foil answers very well.
I measured, cut and folded a piece of aluminium panel and wrapped it around the stern leg of the motor.
I do not want this structure to be a permanent part of the motor because I need to gain access to the ports for leg lubrication and water pump. I riveted a v section tab down the trailing edge of the foil and screwed the other side with s/s p.k. screws so that I can unfasten it any time I need to.
I've laid out Toroa's sail on the workshop floor and I've started the modifications I've been planning.
I've removed the swallow tail tips from Toroa's old red sail (which is featured on youtube) and I've added them as an extension to Takapu's old sail. This procedure results in giving me more sail area down low allowing me to attach the boom much lower on the yard closer to the tack.
I grafted the fabric together using double sided tape which I will then sew with a zig-zag triple stitch. The stitch pattern is critical to the success of this modification as the sail cloth has been laid up diagonal to the angle of the bias to allow for stretch. If the fabric stretches without the equivalent stretch in the stitching the seam will fail or poor set will result. I'm going to try our domestic machine and if it doesn't cope I'll visit our nearest sail maker in Kerikeri next week and ask them to stitch it up for me.
