Auxiliary Rudder with Trimtab Windvane
For the skipper who wants the security of an emergency rudder and a separate upper airvane assembly.
The horizontal axis airvane of the auto-helm windvane powers the trimtab. Water flowing past the trimtab controls the auxiliary rudder which, in turn, steers the boat. The boat’s main rudder is locked and used to balance the boat.
The auto-helm windvane is suitable for boats to 55 feet and especially suited for boats with:
Excessive play or friction in main steering system
Wheel steering with more than four turns
Center cockpit/Aft cabin
Bad weather helm
The Auto-Helm windvane became part of the Scanmar windvane family in 1988. A proven self-steering gear for more than a decade it has since been improved and refined. It earns its excellent reputation from countless ocean crossings and circumnavigations. Today’s auto-helm windvane is thoroughly tested and perfected.
Superior Auxiliary Rudder Principle
The airvane develops information for course corrections. Because of the limited power of the airvane, the signal has to be amplified. Rather than connecting the airvane directly to the auxiliary rudder, the airvane controls the trimtab. Even though it is small, it has ample power to turn the auxiliary rudder.
The auto-helm is a true emergency rudder which will effectively steer your boat back to port in case of main rudder failure. The semi-balanced auto-helm rudder is strong and efficient with a low drag, high lift profile.
No Lines in the Cockpit
The auto-helm windvane is not connected to the boat’s wheel or tiller. It is completely independent of the boat’s steering system leaving the cockpit uncluttered.
Superior Light Wind Performance
This self-contained windvane provides outstanding light air performance. It avoids the friction of the boat’s own steering system and much larger rudder area. As long as the boat is moving through the water, the auto-helm will literally "ghost" the boat along in light winds.
Directional and Downwind Stability
The directional stability of the boat, especially in heavy downwind conditions, is significantly improved because of the aft location of the auto-helm rudder. The extra rudder has a stabilizing and tracking effect of the boat.
The horizontal axis airvane is most powerful in the the vertical position. By pulling the airvane down towards the horizontal position, it can be easily reefed to control the power of the trimtab. When clearance for the mizzen boom is needed, the airvane can be pulled all the way down.
A small, inexpensive, electronic tiller-pilot can be rigged up to the counterweight of the auto-helm windvane. Instead
of the airvane moving the trimtab, the electric autopilot will move it with minimum power consumption. To minimize
interference the airvane is reefed to a horizontal position. This is an excellent set up for motoring or when sailing a close
The auto-helm comes in two halves - the airvane (upper) unit and the rudder (lower) unit. The two units can be totally
separated, with the only connection being a wire running through a friction free teflon tube. The rudder can be mounted
at the ideal height and the airvane higher up, where it gets the best wind. It is possible to avoid interference of davits,
radar mast and other obstructions. The auto-helm windvane’s customized attachment system makes installation easy
on most boats. Installation plans for hundreds of cruising boats are on file. Send us as much information as possible
about your boat. We will make an installation drawing and mounting recommendation at no charge or obligation.
All rudder support parts in the lower rudder unit are made of stainless steel. The rudder and trimtab are hand laid,
fiberglass laminates filled with closed cell, high density, polyurethane foam. The upper airvane unit is made of hard
anodized 6061-T6, marine grade aluminum.
Upper airvane unit weighs 17 lbs (8 kg). Mounting hardware to the rudder is about 15 lbs (7 kg). True installed weight is only 32 lbs (14.5 kg) due to the reserve buoyance of the rudder.
Auto-Helm Upper Unit Only
A simple alternative for boats with outboard rudders such as trimarans. The upper half is available separately to drive a custom trimtab on a boat with an outboard rudder. The trimtab is not provided by Scanmar International because size and design change from boat to boat. However, a quick consult with a naval architect can get you started on a design. This is a simple and economical system for the sailor who is handy and does not mind making part of his windvane himself rather than buying a finished product.