Wednesday, September 30, 2009

Gaff or Bermudean?

In his essay titled "The Ideal Sailing Rig" naval architect Michael Karstan discusses the advantages and disadvantages of different sail plans and hull shapes.  He makes a compelling case for the gaff rig, albeit with a short gaff, no Tops'ls and a single bridled gaff halyard.  A few questions immediately come to mind:

If the gaff has only one halyard do you sacrifice some trim capability and run a greater risk of fouling the main when you drop the sail. The throat halyard is for raising sail and the peak halyard for trimming.  N'est pa?

With the more traditional two halyard rig you can drop the peak to "scandalize" the main and quickly de-power.  I suppose you lose that capability if you have only one gaff halyard?

Just looking at the single halyard's angle of approach it appears there would be more potential for a fouled gaff when you drop the main.  I would rather have to handle two halyards than climb the mast to unfoul a jammed gaff.  Comments? 
Below are excerpts from Mr. Karstan's essay relating specificly to his views on the gaff rig.  To read the complete text click here  What's the Ideal Sailing Rig?

Is the Gaff Rig Suited to Modern Cruising...?
If windward sailing is of paramount importance then of course the Bermuda rig has much to recommend it.

For modern day cruising the gaff rig is often maligned. In my view, for blue water voyaging the gaff rig has much to offer.

If a vessel's keel is shaped efficiently and if the sails are cut for maximum efficiency on the wind and if the sail plan has been designed well, a gaff rigged boat will perform incredibly well, in many cases besting the performance of
a high aspect ratio Marconi rigged boat. This is especially so if one is sailing on any course other than a hard beat to windward.

A gaff rig provides the chance to set more sail area on a given length of mast. For a given sail area the mast can be quite a bit shorter, so the mast will be that much stronger and will require less complex rigging to keep it in place.

The stiffness of a column is inversely proportional to the square of its length. A mast that is twice as long will fail with only one fourth the load, therefore must be four times stronger. One strategy is to use a heavier mast section. The more typical approach is to divide the mast into several "panels" by the use of spreaders. This is the "Marconi" rig. It introduces more stress, more places for failure, more cost, more maintenance, etc. For racing, this is of course justified.

For general cruising however, we can make a good case for keeping things simple and strong. If set up simply, a traditional rig will be friendly and easy to use. For example, one will be handling soft lines rather than harsh stainless wire and winches. If the sails are laced, we will have eliminated sail track and other hardware, along with its relatively much greater expense. This is not to say that one should be old fashioned... far from it!

For example, nearly all the masts I specify are welded aluminum tube or pipe. These are perfect for the gaff rig as well as for the low aspect Bermuda rig. Compared strictly on a strength to weight to cost basis, aluminum pipe spars are impossible to improve upon.

As further example, among the gaff rigs that I have drawn, one will observe that I prefer short gaffs without tops'ls. Primarily, this is for reasons of simplicity, efficiency, and ease of use. The penalty in excess rigging required for gaff tops'ls is more than I'm usually willing to fool with while sailing. In my experience, due to that added complexity, gaff tops'ls often just sit in their bags unused. In exchange for the added complexity of rigging, gaff tops'ls ordinarily provide little gain in terms of usable sail area.


Notes on the Short-Gaff Rig
My short-gaff sail plans are meant to address the shortcomings of the traditional types of gaff rig sail plan. By using a short gaff with no tops'l, there is more luff length to the sail. With a longer luff on the lowers, the lower sails are able to perform much better when on the wind. As an added bonus, sails are not broken into such small units, so are able to be more efficient on all points of sail. As a further bonus, this arrangement permits a single halyard on the gaff, using a fixed bridle that is balanced during sailing trials, then permanently made fast at the best spot.

The short gaff strategy is not my invention by any means... In fact, in its ideal form the short-gaff-sail is fairly close in profile to the shape of the fully battened elliptical plan form racing sails of today. The short-gaff rig was developed and was well proven on vessels such as the Dutch sloops, Bermuda sloops, and of course the pilot schooners of the last century that sailed out of Baltimore.

The pilot schooners needed a foolproof rig that had superior performance, and that could be handled by a man and a boy. They were large vessels...! Applying the same strategy to smaller sailing vessels, one can very easily single hand a 50 footer. As far as the sailing properties, they are well documented among those vessels, and by my own experience having sailed with them.

3 comments:

bott said...

I'd definitely go for the gaff rig on the BCC, furthermore, i would advise wholly against a single-halyard topsail-less main. that eliminates much of the gaff rigs versatility and power (especially without a topsail. it vangs the gaff and add sail area up high where the air is fresher, powering up the rig considerably).

look around on the wooden boat forum for old discussions on gaff vs. bermudia and you'll find lots of good info. much better (IMHO) and mr. Karstan's.

bott said...

by the way, i am gaff sailor (http://www.flickr.com/photos/ericbott/2353451294/in/set-72157604264253041/), and was serously consitering purchasing a BCC bare hull and building it as a gaff.

sea star looks like she'll be a beautiful boat once again!

Ben Eriksen said...

yeah im in favor of traditional halyard set up. no point in having a gaff main without a tops'l either. SWEET !