Why do catamarans not have backstays? I wondered about that, too. I had to ask my sailing friends why do catamarans not have backstays. This is an old term and we had to do a little research. Here’s what I found.
Catamarans are built light for speed. Backstays are attached to the hulls rather than the beams making the structure stronger and more stable, but also heavier and slower. Backstays would have meant a much heavier beam right at the stern with heavy loading at the center and the need for a second dolphin striker.
Catamarans Not Have Backstays
Catamarans do not have backstays. A backstay is a sail that runs from the mast to the back of the boat, the transom, and is often adjustable. Adjusting the backstay controls the forestay tension and the shape of the sails. A backstay can be solid from the mast to the transom or it may split in the lower section with “legs” that spread out to the transom. Either way, this adds to the weight and needed strength on the stern. Therefore, catamarans will not have backstays.
Backstays Tension the Forestay
When looking at a rigging chart like this one, it makes sense why catamarans not have backstays. Backstays increase the tension in the forestay and bend the bast to flatten the mainsail. The backstays often have manual and sometimes, hydraulic tensioners built into them to make this easier. Both of these bring the genoa forward. In other words, they reduce the drag under these conditions.
As the boat tacks the backstays change over. These “running” backstays counter the tension of the forestay to suit the sailing conditions and the sailing angle. In general, you tighten the running backstay to increase the tension of the forestay. Similarly, you can adjust it further when the boat sails very close to the wind.
The Running Backstay Sails
Running backstays can be removable, adjustable, and provide some additional support and tuning. They run to the outer sides of the transom and are adjusted with each tack. The windward running back is in tension. Therefore, the leeward is eased so as not to interfere with the boom and sails.
If you’re in winds strong enough to need backstays, you probably have too much main sail up. It’s better to sail with no main, reef it, or pull the main sheet tight. For instance, put out a spinnaker or your jib. For example, you can also add a spinnaker.
The Dolphin Striker Sail
A dolphin striker, is an older term for a martingale boom. We call them martingale or simply a striker. It is a small vertical or near vertical ancillary spar spanning between the bowsprit and martingale. This sail redirects the tension in the forward end of the martingale slightly more vertically.
On a catamaran such as the Hobie 16 and the Tornado where the mast is stepped on a beam between the hulls the dolphin striker provides support for the beam in order to support the mast load. This vertical angle is necessary to oppose the forestays’ mostly upward tension on the forward end of the bowsprit than would be the case without the dolphin striker.
Conclusion
In conclusion, catamarans do not have backstays. They build catamarans for speed. Therefore, cruising cats are built lighter than their monohull cousins. This is because all catamarans got their start in racing.
This is for two reasons, first the Prout brothers, Francis and Roland, were the first modern catamaran pioneers, and the first introduction of their design was in sailing. Because of this introduction, catamarans got the reputation for speed.
The second reason is that from winning their first race in the early 1950’s, they clearly showed that catamarans were just plain faster boats. As a result, sailboat racing has increasingly focused on catamarans ever since. I hope this answered your question! If not, please leave me feedback and I will research it some more. Cheers!
Sources:
https://www.cruisersforum.com/forums/f48/catamaran-standing-rigging-212827.html
https://en.wikipedia.org/wiki/Running_backstay
https://rigworks.com/standing-rigging-or-name-that-stay/
https://www.wisconsinhistory.org/Records/Article/CS7110
https://sailboatdata.com/sailboat/hunter-45-ds
https://books.google.com.vn/books?id=T0YF0TUlE2wC&q=martingale+rigging+stay
https://en.wikipedia.org/wiki/Running_backstay
https://en.wikipedia.org/wiki/G.Prout%26_Sons