North Retro | Double Head Rigs

Nothing new under the sun😃 Here’s a great piece from between 1972-1974.

Thanks to Pelle Pedersen for keeping stuff like this.

CRISIS shows what the double head rig is all about. Here she is just barely cracked off-the-wind and really powering! The genoa staysail lead is at about 8° from its own tack. The main twist is perfectly married up to the inside sails. 

For close reaching and in many cases for going to windward, a double head rig (high clewed reacher or jib topsail plus genoa staysail) gives a distinct advantage over a genoa. Even on boats carrying a Starcut spinnaker, a reåcher and staysail arean essential combin­ation. First of all, even in light wind, the Starcut can never be carried closer to the wind than 50° or 55° with advantage over the reaching double head rig. Therefore, there’s a fairly wide angle–say between 35° and 50°–when the double head rig is much faster than any other combination of sails. As the wind freshens, it rapidly becomes im­possible to carry a Starcut spinnaker close to the wind and then the reacher becomes even more important since it will be used with wind much further aft. See drawing on page 2 The reacher (jib topsail) isa da­cron sail of the same area as the #1 genoa (unless the #1 hasa very large overlap) cut with the clew as high as possible @ and with the sheet led to the quarter of the boat–probably
where the spinnaker sheet blocks are mounted. The reacher is used with the apparent wind between 35° and wherever the Starcut can be carried-­say 55° or so in moderate air and 90-950 in a fresh breeze.

The genoa staysail or reacher stay­ sail has about 40% of the area of the reacher and is flown under it like a small genoa. It is hoisted flying on a wire halyard (which usually doubles as a topping lift) (b) mounted roughly 1/3 of the I dimension below the masthead. The tack is set about 1/3 of J aft (d) on the centerline of the foredeck. Al­ternately, the staysail can be de­
signed to set on the free genoa hal­yard and tacked a bit further aft. (c) The tack fitting can either be a fixed pad eye or better a slider on a length of genoa track running fore and afton the foredeck centerline to provide variable tack position for this sail and the spinnaker staysail. The stay­sail is sheeted outside the shrouds to the genoa track on a fairly wide reach but under the spreader and between the shrouds (upper and lower) on tight reaches if the shrouds are quite far outboard.

Reaching a double head rig is dis­tinctly faster than a genoa for sev­eral reasons. The mast important is that a sail like a genoa whose leech is appreciably longer than the foot, twists excessively when eased, the upper part falling off and luffing prematurely while the lower part cups in behind the main producing backwind and drag. Since a reacher hasa shorter leech anda longer foot than a genoa it can be set well eased (for reaching) without twisting off and thus the relative trim angle of the whole luff of the sail can be kept nearly constant.

Having the entire sail trimmed at the same angle to the wind adds up toa big plus in efficiency–more forward force and less side force.

The high foot of the reacher permits a big staysail to set inside with a minimum of interference. This is the second big plus for the double head rig. A great deal more sail can be set effectively than with a genoa even if a staysail is put up with the genoa. Other pluses: The reacher is cut rounder and fuller than a beating genoa; hence, more power. The reacher has more area aloft where the breeze is fresher and less turbulent. The reacher never picks up the bow wave the way a genoa does. And, it’s  great for cruising–high clew, good versatility and plenty of speed for light air sailing!

For several years now, a number of boats have been using double head rigs very effectively for upwind work in light and medium air as well. One might expect that a very conclusive answer as to whether this is faster or slower than a genoa would have de­veloped and everybody would either be using genoas or double head rigs by now. There seem to be two basic reasons why no consensus is possible. The fint is that same boats are de­signed fora double head rig and same are not. The other is that without doubt, same owners and crews could never get along with a double head rig while others get extremely good performance from the double head rig. 

Dealing with the boat first, there  are several things that influence whether a boat is appropriate for beating with a double head rig. First of all, we feel that a boat which makes its best upwind performance by pointing extremely high rather than  by footing and going fast is probably not going to profit from a double head rig for beating. A slightly less close winded boat that can foot fast would be a good candidate for the double head rig.

The second thing that makes a double head rig a good choice is if the boat is intentionally rigged with a 150% overlap where she might normally carry a 170% for light air racing. This is often the case for boats that are going to compete in the Southern Circuit or in areas such as San Francisco Bay. In a boat that is slightly under-rigged, a 150% double head rig is definitely faster up­wind than a 150% genoa and is a necessity. The real issue, of course, is on a rating basis whether a 170% genoa is enough faster than a 150% double head rig to make up for the difference in rating. If a choice has already been made to go to a 150% and this makes the boat a bit under-canvassed, then the double head rig should be used.

The third thing to consider is the re­lation of the length overall of the boat to the J measurement of the boat, or to the LP of the genoa to be used. If the boat has an extremely large J or LP and very short ends, the sheet lead for the jib topsail may be too far forward since the stern does not stick out far enough to move it aft. This forces the clew of the jib top­sail to be lower and reduces the available room for the staysail to work. On the other hand, a boat with a relatively small foretriangle and a very long stern overhang is an ideal candidate for a double head rig since the jib topsail can have a very high clew and the staysail can have lots of room to work. To be effective, the jib topsail must not only have a sheet position well aft of the mast, but also a sheet lead angle that is fairly wide at the stern. A boat with fairly wide quarters would be a better choice than a boat with an extremely pinched in stern, since this would keep the jib topsail away from the mainsail.

Finally, and an extremely important consideration, we come to the type of rigging on the spar. The further up the spar the lowest spreader is, the bigger the staysail that can be set with its leech just clearing under­neath the spreader. If a mast has double spreaders, or if the single spreader is extremely low and forces the hoat to use a relatively small staysail, this is something of a disadvantage. Even so, many double spreader rigged boats do very well with a double head rig, but it is not the optimum situation. Since a single spreader quite high on the mast is a feature of many older boats and also is a feature that interferes with the abili ty to use a genoa, these are ideal candidates for the double head rig. 

The disposition of the lower shrouds is very important. This is an area where the owner’s attitude enters into it, since it often means a structural modification to the boat to get the optimum situation for the double head rig. First of all, a forward lower shroud is usually intolerable and has to be gotten out of the way one way or another. Usually a centerline babystay replacing the forward lower shroud is the best solution. Even getting the forward lower out of the way isn’t enough if the best staysail is to be built. The other lower shroud should either be well inboard or rigged over a mini-spreader. Dick Deaver on his Cal 33 fitted the lower shroud with a spreader in order to bring the shroud attachment at the deck further inboard and increase the size of the staysail that can be used. This has become the standard approach on many boats. On any given rig and sailplan we would have to work out exactly what the best options are to develop a double head rig that would be really effective.

One last thought on the characteristics of the boat is that a boat which is designed in such a way that using genoas effectively is nearly impossible becomes a candidate for a double head rig. Two things control the ability to sheet a genoa. One is the dis­tance that the spreaders extend out from the mast, particularly high on the mast. On double spreader rigs the length of the upper spreader controls the sheeting of the genoa leech and on a single spreader rig both the height of the spreader and the length of the spreader control the sheeting of the genoa. The other thing that controls the genoa is the distance the shrouds are outboard of the mast at the deck. A boat with wide spreaders and shrouds well outboard at the deck can’t sheet a genoa prop­erly and should try a double head rig.

Even if a boat were in mast senses ap­propriate for the double head rig, it might still be that in many owners’ hands a 170% genoa would give better performance on a rating basis than the double head rig. There are several reasons for this. First of all, it is hard to sail the boat at its optimum upwind with a double head rig simply because the helmsman’s view of the luff of the primary headsail is ob­scured by the staysail. The second factor is that the double head rig requires that the trimming of three sails interact properly rather than just two. The extra variable makes it difficult to reach the optimum trim. Another problem is that tacking the boat is more difficult and therefore more costly in an around-the-buoys race. These con­siderations make the double head rig much more appropriate for longer offshore races than for the shorter around-the-buoys racing with the first leg to windward.

Using the double head rig effectively upwind requires an owner and crew who have practiced with the rig and have learned to understand it and get the best out of it. It probably requires a more dedicated approach to racing than does the simple genoa rig. How­ever, many North Sails customers are racing sailors and are interested in getting the very best performance they can out of their boats. We feel that with our individualized approach to the double head rig, we can help many of these sailors to do even better to windward than they would with genoas.

For reaching, as we have said, the double head rig is a must. On CHARISMA, for instance, the double head rig is .5-.7 knots faster in 10 knots of breeze at 45° apparent than a genoa + staysail! Many seriously raced boats use a #2 reacher (“blast” reacher) with an area of about 80% of the primary reacher for reaching in very heavy air.

CHARISMA and SIREN SONG were 2nd ånd 4th in Fleet in last year’s Bermuda Race and used #2 reachers much of the time. For long distance offshore racing the #2 reacher can be a plus.

The use of reachers has grown tre­mendously in the last year or two. One reason, of course, is simply that the quality of the offshore fleet has improved and more owners are racing hard and using a reaching double head rig to gain an edge. The other tre­mendous stimulus, however, has been the advent of twin groove luff de­vices. Now sail changes from genoa to reacher and back to genoa can be done on short legs and in shifting winds without losing ground on the course. As a result, the reaching double head rig is extremely valuable for short course racing as well as for longer races–a big speed plus in light air on those reaches and an i­deal alternative to lugging a spin­naker when its blowing and you’re really overpowered! 

“CELERITY II” a Cal 33 won the St. Pete to Ft. Lauderdale Race in 1972 with all North sails. Her large genoa staysail is used effectively by disconnecting the leeward lower shroud (now illegal under IOR rule). A better arrangement is a mini spreader for the lower shroud.The double head rig can be a good way to add power to relatively short rigged CCA designed boats.