Monday, 30 May 2022

Hull Asymmetry.

 Some thoughts.

I have had disappointing feedback from many people about the poor performance of proas they have built

Proas attract the attention of a group of people who see this vessel as a quick and easy boat to build and sail.

Quick, simple & cheap is an uncomfortable triad, poor quality is the result.

Considerable care must be taken to produce a high performance, reliable and safe sailing vessel. Care in design, construction, choice of materials will have a huge impact on the end result.

Many have built to their own design, often deep V ply construction or some other composite sheet material.

Building an efficient asymmetric hull is not a simple matter of making one side flat and the other curved.

No foil built in this way can be considered efficient.

I have never published plans of my proas and I never will. My conscience prevents me from doing so. The intellectual property belongs with the Micronesian people who designed the proa. The proa is a highly specialized and potentially dangerous sailing vessel. It takes years to learn the skill needed to sail one. I do not wish to place novices in danger of their lives.

The so called Kiribati dimple built into the lee side of the main hull is the secret to the success of a true asymmetric shunting proa. Without this feature your proa build will disappoint you with the absence of true windward lift.

Hull speed is another factor that contributes to hydrofoil efficiency. (Hull asymmetry) the faster the more lift. If you live in a region with consistently light winds this too will be a factor in poor lift performance.

Here in NZ we experience seasons with consistently high winds from 15-30 knots on a regular basis. Plenty of power to maximize the potential of an asymmetric hull.

Due to ill health I have retired from building and sailing proas, therefor my publication of more material will cease here.

Good luck to those who are prepared to keep an open and enquiring mind.

To the deniers and non believers, take a long walk on a short pier.

Best wishes from Harmen Hielkema.











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2 comments:

  1. Tel U24 July 2022 at 00:36

    Thanks for sharing this quality information with us.

    ReplyDelete
  2. Anonymous12 October 2023 at 17:00

    Thank you for publishing your very interesting and careful experiences with proas - I appreciate your diligence and caution. May the wind carry you (even if you can't sail proas anymore). Mooie friese naam. Jan

    ReplyDelete

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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.

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