Friday, October 24, 2014

Following up on some comments

In relation to my post, "Lugsail Performance - Better than you may Imagine", Simeon writes: -

I know you've been busy with First Mate but some of us fans are still waiting for illumination on your comment from an earlier blog entry:

"In a later post I'll show you how you can improve the windward performance of the lugsail even more, using nothing more than a short length of V.B. cord."

Well, I have been very lax both in the writing of posts, and in the answering of comments. I'm sorry for that - it has been a combination of building a house, trying to catch-up of long overdue work (and in the process, putting food on the table), and having more plumbing work done on my heart (currently up to nine stents). Still, it is not an excuse for me being rude and dismissive.

Regarding the method of improving the performance of a lugsail when sailing on the wind, a clue lies in the sheeting arrangement on a Chinese lugsail.

My old boat, which is still sailing after 45 years, here sporting her Chinese Lugsail back in about 1990

The system I use to improve the performance of a lugsail is a very simple vang which which leads to the head of the yard. This vang system can also be used effectively with all varieties of lugsail (balance, standing, and dipping), the sprit rig, and the gaff-headed rigs of differing styles.

Most people are familiar with boom-vangs, but the vang I'm showing here operates at the top of the sail, and unlike boom-vangs, it is very lightly loaded, requiring only a light line. This is not an idea of mine - vangs like this have been in use so centuries - however, I suspect that my method of rigging and adjustment is novel.

In the above drawing, I've shown a small boat with a balance lugsail set close-hauled. For the sake of clarity, I have omitted the mainsheet from the sketch.

The vang is simply a length of 3mm (1/8") VB-cord made fast to the head of the yard. In the case of a sprit rig the vang attaches to the upper end of the sprit, or to the outer end of the gaff for a gaff-headed rig.

I have drawn the vang in red, and it runs down to a thumb cleat on the weather side of the transom, across to a simple fairlead on the rudder head, and then along the tiller to a small V-Jamb cleat or a little cam cleat located in a convenient position to allow adjustment. There is very little load on the vang, and it is quick and easy to adjust.

The vang is lead to the weather side so that the angle it makes up high is not too acute, therefore increasing the mechanical advantage. When tacking there is no handling required, because the vang slips out from under the thumb cleat of its own accord as the sail moves across the boat. After the tack has been completed and the boat has settled on the new course, it is a simple matter for the skipper to reach over and grab the vang as it blows out in a smooth curve from head of the sail down to the rudder, and slip it under the thumb cleat on what has become the new weather side of the transom.

For up-wind sailing, this simple vang allows one to adjust the amount of twist in the sail from boom to yard (or gaff, or sprit), greatly improving performance if the crew knows what they are doing. Some will tell you that you should have twist in a sail to take into account "wind gradient". Well, full-size empirical testing has shown that such a thing may be of value at very low wind speeds, but once the wind speed exceeds 6 knots, you are better off with minimum twist.

Sailing downwind, the very same vang can be used to prevent the yard/sprit/vang from going beyond 90 degrees to the centreline of the hull (70 or 80 degrees is better), therefore avoiding the dreaded "death roll".

In this photo of Phoenix III at rest, you can just make out the 1/8"/3mm vang blowing out in the breeze behind the sail. Obviously it has been completely loosened off, but it gives an idea.


  1. We used a scaled up version of this yard vang (6mm line) on our Bolger Jessie Cooper and it made a huge difference in windward performance and allowed us to surprise a lot of folks in the process.

    1. Re Jessie Cooper - one boat I can't escape from (in my mental fleet) is AS29

  2. Ross -

    Thanks for your excellent detailed description and fine sketch and photo. Yes, it does make a lot of sense to me and I'll be trying such a vang the next time I'm out on the SCAMP. I've already rigged the vb line but will wait on the thumb cleats for now and be using some appropriate fittings on the outboard sides of my aft transom. I've been known to flag out my balanced lugsail forward so have allowed enough line to permit that.

    Thanks for passion for wooden boats and best wishes for your upcoming plumbing upgrade.


    1. Thanks, Simeon,

      Very kind words indeed. I feel terribly guilty for having neglected my blog, but as someone I know said recently, "I haven't got time to fit my life into my life..." I find it very difficult to delegate, and I've got so many things on my plate. However, I take it as a very positive sign that after 55 years of passion for wooden boats (sailing, mainly) the feelings continue to grow stronger - no hint of boredom or burn-out!