There are many reasons people prefer boats with asymmetrical spinnakers over traditional symmetrical spinnakers flown from a spinnaker pole. The asymmetricals are easier to sail since you don’t need to hassle with pole on the mast and there are fewer lines leading to the cockpit. Those lines include: a topping lift to raise the pole, a foreguy to keep the pole down, afterguys to pull the pole back, and control lines on the mast for moving the inboard end of the pole up and down.
Besides being simpler to fly, most rule makers allow asymmetrical spinnakers, flown from a centerline bowsprit, to be bigger than sail flown off of a pole that can be rotated aft. The rule makers allow this increase in size because they see the sails flown off a centerline sprit as less effective than a sail that can be poled out away from the mainsail when running. But rarely do you get to see a direct size/shape measurements between the two types of spinnakers on the same boat.
UK Sailmakers has used FSI sail design software to overlay both types of spinnakers, in this case on a J/35. In the first two images, we’re looking at a red A2 running asymmetrical superimposed over a standard S2 spinnaker. You’ll see how much more surface area there is providing additional power and drive – especially in winds below 14 knots when the boat is not sailing dead downwind.
The next sequence then imposed a smaller A3 over both the prior spinnakers. It’s amazing to see the size and shape differences in these direct comparisons.
What you say, you don’t have a sprit on your boat? That’s no longer a problem. You have a number of options. You can acquire several different off-the-shelf deck mounted sprits (both aluminum or carbon), the Trogear sprit that can rotate up at a dock or mooring, or more permanent custom-made bolt on options. Either will work and you can be sailing with a new asymmetrical spinnaker sooner than you thought.
If you sail shorthanded or in areas where the prevailing winds are under 14 knots, switching from symmetrical spinnakers to an asymmetrical spinnaker flown off a bow sprit is an easy choice.
Contact UK Sailmakers about converting your boat from symmetrical to asymmetrical spinnakers.