We recently purchased a 2006 Tiara Coronet with twin 5.7's, which we like very much. I find it very difficult to control at low and idle speeds, particularly in significant wind or current. It behaves as if the rudder is just too small, and requires a lot of shifting in and out of gear. Has anyone else experienced this?
At low (idle) speeds you generally will have very little if any effect from rudder input. A rudder is similar to the wing of an aircraft where it needs air (in the rudder's case, water) moving over the surface in order to create lift. Id suggest centering your rudders and using the shifters to control the boat.
Max hit it on the head! The Tiara 2900 Coronet is a very wide vessel with shallow draft (more affected by wind and current). Gas engines idle at a very low RPM and yet they have a very high RPM at WOT, which means the props have low pitch to accomodate the wide range from idle to WOT. The rudders are designed for cruising speeds and WOT. Making the rudders larger to accomodate low speed handling would adversly affect cruising and high speed handling and in some cases could create dangerous situations. Max is right, center your rudders and use the shifters to control your movement when docking or in tight situations. In some cases you will have to give a bit of throttle to make the boat do what you want. Either way, the twin inboards are much better than I/Os or Outboards. If money is less of an object, you may want to consider installing a bow thruster. Personally for the few times you may need it, in a boat as small as a Coronet, I would not spend the money. Just take your time and you will eventually get very good at handling the boat without it.
Concur with others that this is most likely a normal handling issue. Only thing to add is make sure your hydraulic steering is not sloppy due to trapped air (there should be NONE), and bleed the lines if necessary. Chris, I'd like to learn from you about the downsides of rudders that are "too large". I've read online about many who increased their rudder sizes to help with tracking. I always thought the downside might be some lost speed, but now you have me aware there is more to it than that. What dangerous situations could arise?
Twin inboard planning hulls generally have small rudders. The rudders will have little affect at idle and vertually no affect in reverse. The easiest way to dock a twin engine inboard is to center the rudders and use the clutch controls to manuver around the dock. Outboards and I/Os generally can be turned for trust vectoring when docking, but on an inboard you can not thrust vector, you can only deflect thrust using the rudders and only in forward. When an inboard is put in reverse, the rudder is going to have almost no effect.
Installing larger that standard rudders may cause a loss in speed, but more importantly cause steering issues at high speed. The rudder hydraulics where designed with certain working pressures. Enlarging the rudders will certainly increase working pressures and could lead to a hydraulic failure or could lead to an inabililty to turn the wheel at all at high speeds. Most Tiaras do not have power steering. Increasing loads by increasing rudder size may call for a complete redesign of the steering hydraulics and may necessitate the addition of power steering. Larger rudders could also cause over banking in hard turning situations. The IPS Tiaras have computer controlled steering that limits how far the IPS drives can turn depending on your speed so you cannot put the vessel into and unsafe hard turn. Manual hydraulic steering cannot have multiple steering ratios based on speed. Either of these situations could be dangerous. Manufacturers including Tiara do a fair amount of research and development when designing the running gear. While items like props can be tweaked to a specific users typical loading, rudders on planning speed vessels typically should only be redesigned by licencensed Marine Architects that take into account everything in the steering system including hydraulics, rudder design, steering tie bars, steering pump and lines.
I'm not saying a rudder system could not be improved upon, just that it should be designed by proffesionals familiar with flow dynamics, hydraulic designs and steering systems.
Exactly what I was looking for. Thanks, Chris!
I have essentially the same boat. A '94 29 Open. I think mine handles great, but I also have years of experience with single I/O's out outboards which are significantly worst in wind and current.
I always use my engines for close quarters manuvering. With the wide spread between the props it handles great both forward and reverse.
One trick when dealing with wind or currents is to bump the RPMS up a little. My trans are rated for shifting up to 1K RPM. My low idle is around 600-650. Bumping the RPMS to around 800 helps tremendously. Once the trans is engaged don't be afraid to use more throttle if necessary to help maneuver.
With a little practice I'm sure you'll be a pro in no time.