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Struggling with low speed manouvering and docking

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I have a 35 foot rogers catamaran, very light, foam glass construction with a single 9.9hp Yamaha high thrust.  It is a very light boat.

 

The boat is being painted next week, after which I will have the mast with new rigging re-installed, new sails etc.

 

We ran a trial with the new 9.9hp Yamaha the other day.  I forgot to put the centreboards down prior to leaving a fairly tight spot in the marina and really screwed the pooch.  The boat was on the verge of not having any low speed control and quickly reversed in and re-tied and dropped the centreboards which made things a lot easier - but still not great.

 

We don't have the outboard steering with the rudders as the outboard turns less than the rudders and restricts rudder movement if connected to the steering system.

 

I am considering fitting the smallest bow thruster (110mm) as far forward as possible to the port hull to assist with low speed manoeuvring and possibly one to the stern.

 

Any suggestions on how I can improve the manoeuvrability of the boat including a way to connect the outboard to the steering system without restricting full rudder turn, understanding that both budget and lack of skill may play a part......

 

Thanks for your suggestions.

 

IMG_E1118.JPG

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Nice looking boat, 9.9 seems  small for that size and windage of boat. Might be fine for a mooring ball but in and out of marina berths with a cross wind...

I've had a couple of 8.5m light (900kg) multi's, cats and a tri with 8hp on them and there are times even that is marginal.

The key on the cat was having flow over the foils, if they are reasonably high aspect then at low speeds they'll have very little bite. We nad to come into the berth with a bit of pace on then gun the engine to stop the boat.

Leaving the berth, was drop the lines and again give the engine the message until we were going. That was a berth with just poles, no finger and we were stern too through.

Is having 2 outboards an option, one either side?

Wouldn't add much weight for a boat that size and would give you a whole lot more options around maneuvering, plus a bit of redundancy.

Either that or put a rub rail on while its out the water

 

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You say the outboard doesn't steer with the rudders, but does it steer at all? If not then fit a tiller to it. And you'll probably find the boat behaves better in reverse with the engine dragging it rather than pushing it; it's less dependent on the flow over the foils.

Think about which way the wind and currents are moving. They can help or hinder a lot. It can be worth manhandling the boat using ropes to/from a different position in some circumstances. Oh, and don't forget to put the centreboards down!

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Yes the outboard does steer.  If we hook it up to the steering (ropes and pulleys) the turn of the outboard is less than full lock on the rudder.  This means we probably loose around 20% of the lock on the rudders.

 

I agree that 9.9 is at the low end of the power range but we are space constricted.  Had a Honda 20 that came with the boat that just did not fit.

 

Is it worth fitting a bow thruster when she comes out of the water?

 

And yes I did stuff up by not lowering the centreboards.

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Either install a separate steering system for the outboard, or disengage the (rope pulley) setup from the rudders once in the clear?

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We fitted a bow thruster to a 27' cat that had a single Yam 9.9 that did not steer.

Made all the difference but still struggled a bit with strong cross winds but

you knew one way or another your had options to get to the berth even if

not totally dignified!

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What about (2) torquedo pods mounted under each hull? 

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2 hours ago, smj said:

Either install a separate steering system for the outboard, or disengage the (rope pulley) setup from the rudders once in the clear?

The independent steering might be easy to jury rig to test, and then relatively easy for permanent solution if it works for you.

I was on a biggish day charter cat (I think it was a Goldcoast) run out of tight spot in the harbour. I noticed it had one large sled mounted outboard. I thought it a shame to not have the advantage of two widely spaced props for manoeuvring until I saw the boat in operation. Having outboard and rudder steering as two systems allowed the use of water flow over foils and outboard thrust independently, e.g. with way on hard to port on the helm and hard starboard but reverse on motor both slowed the boat and had the stern almost jump to starboard. I think he’d practiced it a few times (maybe a few times a day 100 days a year...) but I was impressed.

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Could the outboard tiller be lengthened a small bit so that the outboard hits its stops at the same time as the rudders hit theirs? Angle will be different, yes, but performance far better.

Thrusters seem like extreme overkill.

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One 9.9 motor seems underpowered for a boat of that size and windage anyhow? Get another 9.9 motor. Having two engines should help with steering as well?

In lieu of thrusters, have a look at (removable) bow mounted trolling motors. Most are remote controlled these days.

https://haswing.com.au/caymanb.html

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Thrusters would be a last resort.

Can you rig a tackle to allow the outboard to steer somewhat less than the rudders?

Your cat will maneuvre more predictably astern than forward at low speed. More predictably for a car driver.

We had a 45 ft cat with a single 35 hp Yanmar in a central pod.  For a while I had the extended stern-drive leg steering with the rudders.  Worked fine but when I tried it with the stern-drive locked, that worked fine too so never bothered with it again.  Same marina.  We always came in stern-first.

A single 9.9 is marginal but, if you can learn to live with it, you'll be saving a lot of aggravation and the horrible sensation of overload confusion when things go pear-shaped.

It must have worked for someone.

Cheers

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Get another 9.9. cant be any more expensive than a thruster?  It will mean moving the existing one but you can ditch the steering gear for it.

 

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Think about putting at least one of the dagger boards down a bit.  My Corsair 31 is almost impossible to maneuver under motor without at leas some dagger board down.

 

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Can you re-rig the steering tackle to provide a 2:1 purchase.  In other words for every 2 feet of pull from the rudder side of the tackle you get  1 foot of pull/action on the engine's tiller.  You may not get full lock to lock on the engine steering but it will be something, and its a simple no cost, no/few holes drilled solution to try.  You will only need 2 pulleys from your "spares" inventory to give it a try.  2:1 is the way most outboard motor boats in the 50's and 60's were steered before there were teleflex type cable systems.

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twins and spins

two motors make anything eazyer by an amazing amount [lift crew at M&S in the grove long ago]

as do outboards that spin 360 instead of reversing the prop but hard to get with decent HP as 5hp is the point they disapear

I would  favor a  forward mount big el troller if stearable remotely over a mounted thruster both for cost and control and drag

adding an other  y-9.9 is the best idea and move them out as far as you can more power gives more control

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Add Anti-cavitation plates to your lower unit on the motor (Doel Fins or Gorilla Wings). That’ll prevent low-speed cavitation. Also get a high thrust , low pitch prop (if you don’t have one already). Most props are pitched for planing speeds. A thrust prop is pitched lower, giving you more bite at low speed. I liked being able to steer my outboard independently from the rudders. Or...go for the 2:1 or other mechanical limiting on the motor steering. 

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