Boat handling with twin engines

Sorry but no! The rudders on a planning boat are sized arround giving the correct turn ratio at planning speed, they are tiny compared to a similar sized yacht so yes i agree that they should work in astern if there is flow but they are so small they just dony untl you have speed on.

When you are manouvering a planning boat in a marina at slow speed i.e. under 3 knots the rudders on a shaft drive boat do not work on the astern engine, the flow of water from an engine in astern is forwards so it is not going over the rudder, by comparison the ahead engine is driving its flow over the rudder with considerable force - hence the rudders work in ahead. You need to have a fair bit of speed on 5/6 knots plus to actually have a chance of steering in astern and then you have to ask why would you go backwards at that speed in a marina?
 
Well yes, but all a bit pedantic.

I think we are mostly agreed, that using the wheel in a marina, is fairly pointless. Experienced or not.

Cant remember ever looking how fast I am going when backing out the marina, and usually far to busy using the engines to stop the front bit passing the back. Useing the wheel as well, would just add even more complications to the process.
 
Jon you really are quite wrong. Your post ignores fundamental fluid mechanics and engineering. Your statement "the flow of water from an engine in astern is forwards so it is not going over the rudder" shows no understnading of fluids. There most certianly is a flow of water over the rudder when the boat is moving astern or when the the engine is running astern. It's obvious that a spinning prop will create a water flow, whether it is spinning forwards or backwards. That's how it accelerates the boat.

I fully agree that the sideways force of a rudder on the astern engine is less than on a forward engine (becuase the fluid on the "suck side" of an axial impeller not mounted in a tube - ie a boat's prop- has more dissipated flow and hence less velocity than the fluid on the "blow" or "push" side) but it is most certainly not zero as you are saying. And that is borne out in practice - when astern one can feel the sideways force/turning effect even on smallish planing boat rudders, if one is sensitive to it.

I agree what you say about planing boat rudders being small and being sized to work at speed, but that's an effect on both astern and ahead performance of the rudder. It is not an "astern-only" matter.
 
I'm with Haydn here

Toooooo much information.

Just stick the helm in the middle and do it all on the engines.

The effect you get from the rudders is not only small and it all gets too confusing for my little brain to work out.

You are all trying to be too clever - KISS

So there.
 
But it's all waffle really init. Yer about three second in reveres with one engine and forward on the other, then switch about a few times, till going down ally way backwards. Then it's a case of stopping the front end from vearing round with the wind. So one engine sorts that out, whilst the other keeps you going back ards.

All the rest of the crap is just muddying the waters.

I've never seen a wind that can beat the engines. Well certainly not one that you would be out in.

Why is it. You give good advice, then some pillock has to come along all pedantic and slag you off. Then get into aljebera or whatever.

God knows what the poor poster is going to advise his older Dad, uncle, I forget. /forums/images/graemlins/confused.gif

Simple, both hands on big sticks. Round fender on bow. Outer engine forwards, inner reveres. Boat spins the on fender. Back up again maybe, again use fender against pontoon. Surprisingly, you can get to 90 deg from pontoon, never touching the hull.

All this about using the wheel is bolox. Works well at 20/30 knot's and they know it.
 
Haydn (and Hurric) I agree with you 100%. Stick the wheel amidships and park/unpark just on engines. I said that in my first post above on this thread. I do not recommend using rudders.

But in the 2 posts immediately above I'm just disagreeing with Jon who says that rudders do not work when going astern slowly, becuase there's no water flow over them. That is nonsense. Rudders do work and do have flow over them when props are spinning astern, though only a modest amount. But I still agree with you, there is generally no point in using rudders for this sort of manoeuvering. Rudders bring little benefit and lots of effort turning the wheel. Yes, best advice to OP is use just the engines :-)
 
Thanks guys, consensus seems to be not to use the wheel only the sticks. Particular thanks to hlb for earlier post describing how to get boat going sideways. Suspect that will need some practice. As will getting into a tight space.

Talking of tight spaces, in a marina what is considered to be the norm re space either end of the boat for alongside berthing? Seems my dad has been put into a pretty tight space where his bow almost overhangs the boat in front with about 6' behind him. Position of the cleats make it awkward to move back. Was originally promised that there would be about 10-15' spare at either end but they've now squeezed another boat in.
 
Look where I said about useing a bow spring above. Dont try the sideways method till really confident and when theres room to easily moor.

Much depends on wind and tide, as to how you approch. So each time might be different. But here goes.

Drive the bow into the gap at say 45deg, so arse is sticking out. Crew on the bow. Lassoo's a cleat by hanging a big loop of rope over the side, then swinging it over the cleat, hopefully one, say six foot back from the bow. Judge the length of rope, so the bow is going to end up as close to the boat infront as you need. Tie it off. You need to do this as quickly as possible. Before things go wrong. Back out and try again if needs be.

Once rope is secure, drive forwards against it with inside engine whilst putting the outside engine in astern. The back end will start to come in and the boat will lay alongside the pontoon. Whilst this is going on. Crew walks to stern,, steps off and secures the stern, useing springs as well, till the boat cant move. Only then are the engines taken out of gear.

You need a big round fender near the bow. Find the right place on your boat.

To leave. Forwards on the outer engine, reverse the inner. Ajust as necesary. The back will come out and the boat will rotate on the fender. Once clear, back out.
 
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