Close Encounters Of The Cat Kind

By Author: Terry Buddell
Total Articles: 24
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To the initiated or newcomer to Multihulls the prospect of up close manoeuvring in tight situations must be the kind of stuff bad dreams are made of. However, getting to grips with the beast is the best answer and surprising many Cats, large and small, can run rings around a mono when it comes to manoeuvring in close quarters.

FACTORS THAT DETERMINE THE TURNING CIRCLE.
Like a monohull with twin engines and a juicy bow thruster, the difference between the ‘haves' and ‘have nots' is astonishing. Let's look at the type of power that is available to a Cat and how it determines its handling characteristics and the secret ingredient, ‘the turning circle'.

STERN MOUNTED OUTBOARD ENGINE
Arguably, the most difficult to handle due to a few factors, one is that no controlling prop wash can flow over the rudders therefore requiring that a higher ‘entry speed' may be required to control direction. Another problem may be that when going astern the props often don't perform as well as when going ahead. Some advantage may be gained from the fact that they may be able to rotate through 360º. ...
... However, most outboards are invariably clamped and only dead ahead and astern are available. Therefore, the end result will be a wide turning circle probably worsened by adverse wind or tides and lack of water flow over the rudders.

INBOARD MOUNTED OUTBOARD AND/OR STERN DRIVE LEG
Usually preferable to the former scenario due to more steering control for turning via tillers and cables. Some may be steered independently. Once again no control from the rudders is available due to lack of prop wash, so higher approach speeds to maintain control, may be needed. Probably, approaches into wind or tide would certainly help keep control over the direction.

INBOARD ENGINES
Sheer heaven! Twin diesels are probably the favourite choice, for economy and ease of handling, especially at low speeds. The prop wash can be precisely used to control direction and, luxury upon luxuries, these engines can be used to turn a cat almost in its own length. As mentioned, the forward thrusting engine (the outer, usually) will be more effective but extra power on the reverse will be needed to compensate. It's not unknown to mount twin outboards on each hull to attain a similarly desired effect.

Other factors controlling turns will be power available, wind/current speed and direction of windage on the boat, and deployment of centreboards in order to maintain more ‘grip' on the water. Finally, choppiness or sea state may contribute some difficulties to steering.

TIGHT TURNS through 180º
(see ‘Tight turns to starboard ‘diagram)
Often in a confined area such as a dock, river or narrow waterway, a cat can turn superbly using a spring. The spring is tied to the foremost cleat, furthest from the berth or bank and the line run down the outside of the beam then round the stern cleat then away to a bollard or cleat on the berth. Cast off the inner hull bow line, motor ahead gently and the spring will tighten pulling the nose around tightly. When clear and around release the spring line, taking care not to foul propeller with the line in the water.

Once again, a twin engined vessel can tighten this turn by using one engine ahead, one in reverse (the inner) and the helm hard over to the direction of turn taking advantage of the prop wash over the rudders.

COMING ALONGSIDE
It is wherever possible to make your approach into wind and current because using the slow forward speed, the forward inner line can be made fast by a crew member without leaving the boat. A line is simply looped over the desired cleat and made fast. The wind or current, if from ahead, can then swing the stern in neatly aided by a little outer engine power astern (see diagram ‘Coming alongside').

If possible, it would be preferable to loop a short line amidships first because it gives you time to sort your forward and aft lines whilst being held fast. Ensure the amidships line is not astern of amidships because the bow will tend to swing away from the berth causing excessive force on the cleat and possibly ripping it out if the forward line does not get attached smartly.

In cats with non-steering power you must keep some power on to provide steerage, reversing at the last possible moment to reduce way and preventing excess strain on the line, hull or cleats. However, with steerable motors providing steering control, a slower and more sedate approach is possible.

I always remember some solid gold advice some years ago about coming alongside, If you're going to hit anything at all, do it in wonderful slow motion!..How true!

LEAVING A BERTH
There are two ways of leaving a berth in reasonable conditions, forward or reverse. The tight turn method forward has been described if the wind and current have reasonable force but a normal forward departure is fairly straightforward. It may be helped by letting the forward inner bow line go, leaving an inner stern line on. Forward gently, turning away from the berth and then after pivoting to the required direction, ease off the power and release the looped inner stern line.

In adverse conditions, such as gusts or a wind pushing you against the berth, a reverse exit can be favourable. Attach a big fender at the bow to pivot on. A bow spring is attached to the inner bow and to a line astern on the berth. NOTE: If this line is to go off with the boat ensure it is looped for quick removal. After all crew are alerted for standby, release any other lines except the forward spring. Motor ahead gently, If directional control is available, turn in towards the berth. Due to the width and more available leverage the cat will begin to swing out, sternward first, away from the berth, pivoting against the forward inner fender. When the cat is at the desired angle, go astern, slip the forward spring and reverse away smartly into clear water astern (see fig: 3)

KITING YOUR KAT
Lastly, a catamaran has a unique method of manoeuvring sideways without any rear or forward motion. This method can be used for simply standing by for an indefinite time or for moving into a berth sideways. It works just well with a forward wind or current and relies simply on the correct angle and enough power to counteract the wind or current resulting in zero forward or reverse speed. This, of course, can be altered by increasing the power or decreasing as required.

When approaching a berth turn into the wind or current, bow nearest to the berth. The wind at the correct angle will start to ‘kite' the cat sideways towards the berth. Adjust your power to move ahead or reverse as the case may be. You will move sideways inwards if the angle and power are correct. It takes some practice but is very efficient in difficult headwind conditions (see ‘Kiting in' diagram). It may help if the rudders and centreboard are fully in the down position.

Remember at all times, cats behave differently under differing conditions and are subject to power, engine configuration, wind and current and available ‘grip' on each rudder and hull.

Have fun, but remember do it all in wonderful slow motion!

I f you have enjoyed this article and would like to read more why not visit Terry's site at www.dolphinboatplansDOTcom
Terry buddell is a freelance writer and lives on board the yacht he built in Gladstone Australia. terry designs boats and has evolved the Easy-Build method of boatbuilding boats that require no internal framing. Terry is a Marine Surveyor and has a website where he sells his boat plans and designs !
If you are interested in more articles and informative info about building your own boat, why not visit www.dolphinboatplans.com