Sunday, 31 January 2010

January 2010 progress on Toroa

Work on Toroa's sail and motor has begun again.
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.

1 comment:

  1. Hi Harmen,

    I have read through you blogs Sequentially from 2007 to August 2010. It took time but defiantly worth every minute, some sections I had to read several times to understand. Thanks for providing such detailed information.

    There are are 2 area's I would love for you to expand on (a blog on each topic would be really appreciated), in the hope I can learn more.

    1) this is probably the easier one, I would love more more details about your sail, "mast" and "boom". I read with interest you comparison between the weaved sails and the cotton sail materials, I noticed that you mention using poly-tarp, is that what this sail is made of? You mention that sails always have angles between 50 - 60º what angle is your sail? which direction does the thread in your sail run (i'm guessing from the Tack to the middle of the leach and then at right angles to this)? How are your spars constructed and connected? They look to be PVC electrical conduit, but I suspect there is more to them than that? are they just lashed together at the tack or is there some other connection?

    2) In April 2009 you talked about the "Kiribati dimple". I have looked at the photo's many times and re-read that post several times as well as everything else google turns up, but I still am not sure what I am looking at with regards to this. As it obviously has a significant impact on performance I would like to learn more about it. Can you highlight this in the photo's or draw it and explain how you went about implementing it in your hull.

    I also notice that your suffering of arthritis is gradually getting worse, This is something I can understand, having been there. I started getting arthritis at the age of 18 (after suffering chronic fatigue and other ailments) it progressively got worse, I gave up on western medicine and tried traditional Chinese herbal medicine, after 1 year of taking this medication I was back to being almost free of any pain. I hope you are able to find the same relief I was able to.




Toroa by Harmen Hielkema & Mike Toy.

Header Photo: Toroa at Rawene by Julie Holton.

This blog is dedicated to the memory of my father Roelof Hielkema who instilled in me the willingness to learn.
These pages are intended to inform and add to the growing body of knowledge concerning the Canoe Culture of the Pacific, past, present & future, from the Tupuna, the Ancestors of the Pacific cultures to the people of the world.

These pages contain Images and text relating to our two proas, Toroa & Takapu, some history relating to our experiments & experiences.

The dissertation that I posted on this blog in April 2008 "Takapu The Proa" was written by me in 1997 in response to an assignment that I was set whilst studying for my design degree. The dissertation covers many issues that a proa enthusiast may benefit from reading about.

Waka define culture as culture defines waka

Waka reflect the individuality and uniqueness of a society which in turn is governed by the geography, geology, topography, climate, location, resources, isolation, origin, flora, fauna, flotsam, jetsam, etc.

Waka are our link to the past, they have shaped our present and define our future.

Waka are the vessels of knowledge, physical and mental development, freedom of bondage to the land, key to our inquisitiveness, expressions of our ingenuity and courage, our love of shape and form, the seat of our power.

Waka are the source of our material culture, from which all processes are derived.

Waka are who and what we are.