Thursday, July 11, 2019

Sailing the Argie 15

I designed the Argie 15 in 1988 for the Argus Newspaper Group in South Africa. They named it after the street corner sellers of their newspapers, the Argie Boys, as a dedication to them. In the more than 30 years since many hundreds of these boats have been built and they are to be found in 60 countries.

I was the first person to sail an Argie 15, the prototype that was built by journalist David Biggs. He produced the weekly DIY supplement for the newspaper and commissioned the design as a DIY project for his readers.
That is a young me at the helm, journalist David Biggs as crew, on the maiden sail of the Argie 15 prototype.
We sailed among the moored boats of False Bay Yacht Club, in about 8-10 knots of breeze, with the boat behaving beautifully. Many boats were built from the articles in newspapers and magazines, as well as plans bought from us, generating a strong following.

I didn't get to sail an Argie 15 again for nearly 30 years, when we launched our own boat three years ago. In all that time I only heard good reports about the handling characteristics of boats to this design. Then, a few months ago, a new builder asked me about the comments that he had read of these boats having lee helm and how to remedy it. I had not seen these comments and told him that I would do some testing with my boat when on a planned sailing trip to North Carolina in June.

That sailing trip was a few weeks ago. I went out by myself in light and fluky conditions that gradually built to about 15 knots and gusty afternoon sea-breeze. This gave me opportunity to test in a range of conditions.

I like to sail from well forward in my boats in light conditions, so I fitted my long tiller extension, a 6ft length of bamboo connected to the tiller by a short length of flexible hose on a pivot bolt. This would enable me to sail from anywhere in the cockpit, from far aft through to sitting on the centre thwart. I had seen in photos that some owners helm from aft, alongside the tiller, so I needed to test this position although I knew it would create problems.

This proved to be the case, with fore/aft trim having a big effect on helm balance. With weight aft, she trims bow-up and the bow gets blown downwind because the centre of lateral area moves aft. The hull should float close to the attitude shown on the sail plan to get the balance between sails and underbody correct.  If sailing alone, sit well forward, alongside the daggerboard. With other people aboard and sitting toward the front of the cockpit the helmsman can move aft, as seen in the photo of the prototype, keeping the boat fairly level. Just because you can sit next to the tiller is not a good reason to do so, trimming the boat level is what is needed.

Trimming the boat so that it heeled to leeward or windward also had a large effect on the helm balance. Sailing in steady light breeze while sitting on the windward side gave me lee helm but sitting on the leeward side gave me weather helm. In light but gusty conditions, sitting on the windward side, I had lee helm in the lulls and weather helm in the gusts. I then sailed downwind, standing in the middle of the cockpit, with one foot on each side of the cockpit. This allowed me to push down on either foot to change the heel angle. With the rudder on centreline I was able to steer the boat to either side as much as I wanted, with my feet. Pushing down on the windward side heeled it to windward and gave lee helm, pushing the bow toward the leeward side. Pushing down on the leeward side did the opposite.

This results from changes in the shape of the immersed portion of the hull with changes of heel angle. When heeled over to leeward, which is the correct attitude when sailing, the leeward side of the hull becomes more curved and the windward side becomes less curved. The neat symmetrical hull shape when upright changes to somewhat of a banana shape when heeled and that banana shape turns the boat toward the high side.

At the same time the centre of the sail area, through which the wind drives the boat forward, moves off to leeward of the hull. The drag from the water, holding the boat back, stays at the hull. This results in a lever with the sails pushing forward at the one end and the hull holding back at the other end. This causes the boat turn to windward, have weather helm.

Those two effects from heel that create the desired weather helm will also work in reverse. Heel your boat to windward instead of to leeward and those effects will move to the other side of the boat and give you lee helm.

The effect of fore/aft trim and heel on helm balance is common to most boats of all sizes that have a fin keel, centreboard or daggerboard. I used these affects on my Didi 38 "Black Cat" to maximize boat speed in light to moderate conditions. In light breeze I had most of my crew to leeward on the foredeck. As the wind increased I gradually moved crew aft and to windward, one person at a time, thereby adjusting the amount of weather helm by changing the fore/aft trim and heel angle. It works exactly the same in a dinghy like the Argie 15.

The take-away lesson from this is that you can adjust the helm to suit yourself, between lee helm, neutral and weather helm, by moving weight around the boat. For the Argie 15 the main points are:-

1) It should not be sailed bow-up but it does not mind sailing bow-down. In light conditions I would sail it bow-down but would trim it level fore/aft for most other conditions. In strong conditions downwind I would get weight further aft, as is normal with most boats.

2) It should not be sailed heeled to windward. Crew don't have to sit on the windward side, they can sit wherever needed to get the nicest feel for the helm in light conditions. In stronger breeze the boat will naturally have weather helm and will need the crew to windward for stability. Again, this is the same for most other boats.

There are also sail adjustments that can affect the helm. More power from the sails increases weather helm. Sails that are full (lots of camber) generate a lot more power than sails that are flat, so they create weather helm. Increase power in the mainsail for light breeze by slacking the foot to increase camber. With a jib that has the forestay inside a sleeve at the luff there should be a line at the bottom of the luff, tying it to the eye of the stay. This line is used to adjust the tension of the luff, which adjusts fullness of the sail. Tighten the line to flatten the sail and loosen it to make the sail more full for more power. If you have Cunningham lines rigged on your boat for jib and mainsail you will use them to adjust luff fullness.

Whether you have an Argie 15 or some other dinghy or small keelboat, you can test these principles on your own boat. When you know the characteristics of your boat you will improve its performance and your racing results.

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1 comment:

  1. Hello Dudley, thank you very much for you detailed comments! It's me who ask you that question about the helm)) Buying A15 project I knew almost nothing about sails, so I really appreciated your answer and your readiness to help amateur builders to understand better the subject!
    Regards, Vasiliy L.