No. 47 - February 1982

FURLING GEAR

Robert Fier (#1912)

 

I am writing to you concerning the success I have had in using the Schaefer System 250 Furling Gear for the 140% Genoa sail on my Tanzer 22.

 

When I initially rigged my boat with the System 250, I found that the upper swivel tended to move too close to the forestay when the Genoa was hoisted to the masthead. After several inquiries, I learned from the Schaefer people that they manufacture and sell a "keeper" which consists of a small nylon wheel which is bolted between the wire portions of the upper swivel. In essence, the liner roller prevents the upper swivel from moving toward the forestay after a halyard raises the Genoa. In other words, it maintains the upper swivel and thus the sailhead separated from the forestay.

 

By attaching the furling drum to the aftmost opening on the stem fitting, there is sufficient clearance between the edge of the drum and the forestay at the tack.

 

In use, it is totally unnecessary to head the boat into the wind when the sail is unfurled, it being necessary merely to pull the Genoa sheet on the leeward side and the sail opens and fills at the same time. In furling the sail, it is easiest if the boat be headed into the wind - the line attached to the furling drum is then simply pulled off the drum, causing the drum to rotate and thus wind up the sail. I attached a small block to a foot of the lifeline stanchions and the furling line is drawn back from the drum through such a block, through the block on the inboard jib track, and thus into the cockpit.

 

I have taken the sail down when underway in favour of a hanked working jib and have reversed the procedure. The forward hatch makes it most convenient to stow or unstow the Genoa. Of course, it is constructed with a wire luff in order to achieve the necessary tension. I have a winch mounted on the port side of the cabin top and a clam cleat which I use alternatively with the Genoa or the working jib.

 

Suffice it to say that this arrangement makes cruising a very simple and enjoyable experience.

 

 

MYLAR SAILS

If you've been shopping for sails recently, then I'm sure that you've seen most of the comparisons between Dacron and Mylar. Since the T-22 Class Association does not allow unwoven sail materials at class events the decision is simple for most owners. At a recent executive meeting, allowing the use of Mylar sails in class events was discussed. It was decided that there would be no change in the by-laws concerning sail materials. The following articles by Steve Haarstick of Haarstick Sailmakers and by Bob Raven our Chief Measurer will provide an under­standing of the basis of that decision.

 

Steve Haarstick

Basically, I think anyone design class should carefully consider all the pros and cons before rule changes are enacted that would obsolete any portion of a sail inventory. Are the advantages really worth the extra expense that will be incurred by all the competitive members of the class?

 

It is true that present Mylar film sailcloths are lower stretch than most conventional sail fabrics used in a conventional cross cut panel layout, and may help to reduce the need for more than one Genoa or mainsail to cover the 0-20 knot range. However, everyone would feel it necessary to buy a new sail even if their present sail was relatively new. At least in the short term, the cost savings are non existent.

 

In the long term, Mylar film fabrics are still undergoing dramatic change as more and more sailmakers recognize the need for different stretch properties than are available in present Mylar fabrics.

 

In short, the major problem with Mylar is its stretch properties, although quite low, are basically the same in all directions. If sails were uniformly loaded, then present Mylar materials would be ideal.

 

But sails are not uniformly loaded; the maximum stress on the fabric is in the leech area. Any Mylar that has sufficient strength in the leech area, even the vertical cut Mylars, are over strength and over weight in the other areas of the sail like the luff and body areas. As a result, it is not only very difficult to adjust sail shape with halyard tension but the resulting weight of the sail is heavier than necessary.

 

Adjustability is a very important ingredient to wide range boat speed. If you can't adjust the fore and aft shape of the sail with halyard tension independently of variations in forestay sag, you have reduced the adaptability of the sail shape to the range of wind and sea requirements from 0-20 knots.

 

The vertical panel layout of certain very light weight Dacron fabrics begins to make more and more sense as these Mylar limitations become more understood. The Dacron Quilt-Cut concept that we invented in 1978 combines all of the structural advantages of Mylar, without the adjustability problems, and at a lighter overall weight as well!

 

I would enjoy the opportunity to demonstrate the superiority of present Dacron fabrics used in the Quilt-Cut concept directly with any Mylar sail currently made. Should you and your class decide to allow Mylar fabrics, my only request would be to eliminate any minimum weight specifications so that we may utilize some of our very light Dacron sailcloth in Tanzer 22 sails.

 

For example, we would use a very firm 2.2 oz. Dacron in our all-range Genoa. This sail would have a very fast and durable range of 0-25 knots, yet would be 30-50% lighter than any comparable range Mylar fabric. We could also construct a very excellent Quilt-Cut Dacron Mainsail from a 4.2 oz. fabric in the leech and a 3.3 oz. fabric in the front half of the sail.

 

As I mentioned earlier, Mylar film fabric is starting to go through another dramatic change. By next year, I really believe that most of the present Mylars will be obsolete, as they will be replaced by Mylar fabrics with a great deal more strength orientation in either the panel direction or in the cross panel direction. Only then will they be able to match the strength to weight ratios presently attainable by the many "warp" orientated Dacron fabrics we use in our vertical Quilt-Cuts. If this does occur, we would become enthusiastic about Mylar materials, as they would begin to make structural sense.

 

Bob Raven (#1129)

No doubt everyone is aware that Mylar* and Kevlar* have become the latest improvements in sailcloth technology. Basically these sails consist of a very light backing material which is bonded to a polyester film. The advantage of this type of construction is a superior strength along the bias of the material. As a result, the sail will hold its shape better and have a longer effective racing life, although its actual chronological life might be shorter. One of these disadvantages to Mylar appears to be the resulting stiffness and there­fore difficulty in handling for the average cruiser. Mylar also appears to be much more susceptible to tearing and delamination from the handling of the sails.

 

It was in keeping with the intent of the Class Association, which as stated in the bylaws is to maintain all boats on an equal footing when entered in a competition, that last year we did not allow the use of Mylar in class sanctioned events. This position was taken not to restrict the availability of new technologies in sailcloth to the membership, but rather to maintain the competitiveness of all boats at class events. It was also taken in order to protect the membership from an unproven technology. (I should also mention that the J24 Class Association has felt similarly to us and has denied the use of Mylar. They have taken this position in order to give the technology time to prove itself.) Therefore again this year, Mylar sails will not be permitted at class events.

 

* Dupont Trademarks.

 

 
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