Installing an FD Mast with
Single Fixed Spreaders

by Tony Zegers

The following are some thoughts on the subject that occurred to me as a result of having changed over to this type of rig. The objective is to give sufficient support to prevent collapse of the mast in all sailing conditions, and to provide the correct amount of flexibility for fast sailing in most conditions. A well-rigged and tuned mast is a key to speed, and it should, therefore, be installed with great care and precision.

Let us first look at the preparation before we put the spreaders on. The mast should be rigged without the spreaders and placed, with everything installed, plumb in the boat. The genoa should be rigged in sailing trim for light winds. The rigging should be tensioned normally. We then roll the genoa up and roll the boat over on its side and support the mast just above the hounds; also we provide a support between the hounds and the deck at such a height that the mast lies absolutely straight. It should be noted that the mast foot will have to be attached firmly to the mast by screws or glue, and it should fit without play in the channel. The mast is now ready to receive the spreaders. Before we install the spreaders, however, two things have to be decided: first, the height of the spreaders above the deck; and second, the angle of the spreaders to the centre line of the boat and their length. I mention angle and length of spreaders together as they are inter-related. If the mast is restrained from moving at deck level by blocks or other arrangements, the maximum deflection of the mast will tend to be somewhere above the middle between deck and hounds and probably below 5/8 of that distance from the deck. This now gives us an area where we can locate the spreaders. For a limber mast, they should be near the higher limit (DeHavilland); for a stiff mast (F Section} near the lower limit. SEE SKETCH.

fig 1

Editor's Note: This article appeared in the Canadian FD Class Association Newsletter.




The spreaders and sockets can now be positioned on the mast as follows: the end of the spreader shall ideally be on an imaginary reference line, going through the shrouds at the location of the spreaders or slightly forward (less than 1/4 inch} of this line. We find this line by holding a straight batten at this place. SEE SKETCH.

fig 2

The reason for this is to have the mast straight when only the weight of the mainsail and boom are hanging on it. The distance between the end of the spreader and shrouds in transverse direction shall be set at from 3/4 inch to 2-3/4 inches depending on what mast section we use. Also crew weight and fullness of mainsail are a factor in this case. This distance has to be established for each case, and a difference of 1/4 inch makes a significant difference in performance. After the spreaders have been fastened to the mast in the position as described above, we pull the shroud to the spreader tip and secure it at that point. If we start sailing and we find that the rig is too stiff, it will be necessary to shorten the spreaders a little and change the angle correspondingly so the ends of the spreaders remain on our reference line.

Active control of mast bend can be effected by varying the deck spacing and difference placing of the boom bales.