Reversing

[RLWP]

ummm. afraid not, back to the drawing board, the turning pivot of a boat is just forward of the engine room (or 1/3 of the way from the stern on these modern jobbies). Not that this negates your reasoning about the wind leverage.

 

Hi Chris,

 

that may be true for your boat, but standing on the back of my boat and watching how it behaves when moving forwards, as you put the rudder across the boat turns somewhere around the second mushroom from the front. That is about a third of the way from the bow. For reference the boat is a 70' ex-hire boat with a cruiser stern and about 1' 10" draught, water tank in the bow. What happens in working boats with engine rooms and empty holds may well be different.

 

Richard.

 

Oh no! Now someone is going to have work out the centre of gravity and polar moment of inertia for a narrowboat. Hope it isn't me...

[Keeping Up]

I tried this on the boat next door and they shouted at me. What did i do wrong?

I expect they were awake at the time. That leads to inaccurate results. Next time, do it in the middle of the night while they are asleep.

[Mat B]

.....

So is there a knack to reversing? ....

 

It may sound obvious, but get the boat pointing in the right direction before starting the reverse.

[RLWP]

ummm. afraid not, back to the drawing board...

 

 

Well, rather than take a theoretical approach, we had a very pleasant day bringing Tawny Owl from Wootton Wawen to Hatton on Saturday, and I discovered that... I'm wrong! The turning point on our boat is much nearer the third mushroom than the second. This puts it just back from the centre of the boat, nearer to Chris Pink's 1/3 from the back than my 1/3 from the front.

 

As we had a clear run (in bright sunshine with only one hailstorm) and wanted to get the boat back on it's mooring, I didn't do any significant reversing, so I don't have any more to add to that yet. I am also interested to see what happens when we fill the water tank as it is less than half full at the moment.

 

Richard

[Yoda]

I think that the turning point on most boats is about two thirds forward. This point seems to move back if the bows are high.

[DHutch]

I think that the turning point on most boats is about two thirds forward. This point seems to move back if the bows are high.

The point at which the boat turns will vary on a number of things i guess, such as you say, the distrobution of weight, but also i suppose the shape of the hull, and whats causing it to turn.

- For most boats 3/2rds seams to be a good aproxamation. Proberbly further back on some boats that are very light at the front. And futher back on emilyanne, who weight is very evenly distrbuted. With only around an inch varation in draught from the front to the stern of the boat.

 

 

Daniel

[RLWP]

The point at which the boat turns will vary on a number of things i guess, such as you say, the distrobution of weight, but also i suppose the shape of the hull, and whats causing it to turn.

- For most boats 3/2rds seams to be a good aproxamation. Proberbly further back on some boats that are very light at the front. And futher back on emilyanne, who weight is very evenly distrbuted. With only around an inch varation in draught from the front to the stern of the boat.

 

 

Daniel

 

Let's assume (warning, warning) that this is a lovely day with no wind and still, calm, non flowing water. Intuitively (warning, warning, warning) the boat will turn around it's centre of gravity, which can be worked out.

 

Is this true, and if so what about the forces on the hull? There will be some drag as water moves across under the hull, there will be a pressure difference due to the area of hull that is being moved sideways, There will be a hydrodynamic effect due to the difference in flow across either side of the swim. Do these water effects change the point that the boat turns around? Logically (more warnings) they don't and the boat turns around it's centre of gravity.

 

Anyone care to comment on these thoughts?

 

Richard

[Machpoint005]

It may sound obvious, but get the boat pointing in the right direction before starting the reverse.

 

...and once you are going arsewards, the only control you have is where the arsend goes. The stem will do whatever it wants (wind, shallow water, current). You can kick the arsend to one side or the other (in forward gear) then return to slow-astern to keep some momentum going. It's a knack, and sometimes it all goes to ratchet.

 

The centre of rotation argument only applies, in my experience, when going ahead. Going arsewards, wind pressure and propellor drag are likely to be much more important.

 

Ian

[Tim Doran]

I did my first reverse my 45 footer yesterday morning with supprising success. I was faced with either a 10 min forward, a lock, turn around the lock again and then another 10 mins or 150 meters in reverse to a winding hole. I thought that i would have a go in reverse. I decided to do it early so that I would not meet any other boats. I just put her in tickover and used the pole to keep the blunt end in the correct direction. I found that the pointy end just followed. Big smile to myself when I reached the hole.

As a new boater i would avocate having a go. If you are moving slowely then if you were to loose control you could either correct relaxed and easily or stop and go forward.

[RLWP]

As a new boater I would avocate having a go.

 

Hi Tim, well done! I would always have a go at any boat manouver, after all it may work, and if not you will always learn something!

 

Our longest reverse so far was all the way back down the arm at Brinklow, in the dusk, with a newly blacked hull, on a frozen over canal.

 

Richard

[alan_fincher]

Dont feel bad about it, some boats steer better in reverse than other. (NOT MINE )

I've tried that line as well.

 

There have certainly been boats I could reverse with some accuracy, but I've always struggled with our current one.

 

However the engineer at our marina seems to be able to take any boat there straight off it's moorings and reverse the whole length straight into his wet dock, and with very few bursts of forwards to correct his alignment.

 

The one thing I'll say is he achieves this by lots of power, and at fairly hairy speeds. A couple of times I've though "this will all end in tears", but it never seems to.

 

He fairs just as well with a Springer as he does something from the upper end of the marketplace.

 

So whilst I think some boats reverse better than others, it seems more pertinent to say some boatmen (or women) reverse better than others.

 

I agree though that the times I get it right, there isn't a spectator in sight, but if there's a crowd I can guarantee to foul up big time.

 

Alan

[Scotty]

The one thing I'll say is he achieves this by lots of power, and at fairly hairy speeds.

I've seen some impressive reversing which again involved lots of power and high speed.

 

The guy must have been doing 6 to 8 mph in reverse with the occasional crash into forwards gear to straighten the boat.

Very succesful, but also very noisy and scary and not something i'd try with other boats and people around.

[mykaskin]

I've reversed a couple of boats, both of them a long way. I tend to find longer boats go backwards better, but it does depend alot on the quality of swim (and probably size of the prop as paddle wheel effects are more noticable when reversing). To get any sort of steerage you have to go at a fair old rate - I've managed to reverse my 60ft boat about a mile, at times going as fast as 4 mph (on the GPS).

 

When you are getting it right it feels like you are holding the boat direction on a knife edge, and the smallest of movements on the tiller left or right will alter the direction of the bow. Of course it only takes the lightests of breeze to start the bow swinging, and before long you have power forwards to catch it. Don't let the stern get to close to the shallow water, for a start there is very little grip when you are already going backwards, and the suction will pull you further into the shallows.

 

When going backwards spend more time looking forwards as this is the only way you can actually tell which direction you are travelling in.

 

Other than that practice makes perfect.

 

Cheers,

 

Mike

[Digitalis]

I may be to late to make an entry about this subject I dont know how long they last or when a suject finishes, maybe someone will let me know !!

"so much to learn" any way when we went on our RYA boat handling course,( I dont know if I am allowed to say with who so I wont) but

he had me driving like a right good un reversing under bridges and all kinds, and I was amazed that he could teach me this in 3 days,

and we certainly did not need a bow thruster, the way to go is full speed ahead and then straight back in to reverse with plenty of paddling, with

the tiller, honest i never thought someone could teach me that, our son in law drives a pilot cutter on the Wash and thinks we should have a bow thruster

on our new boat. I can't wait to show him my mother in law skills on the tiller when we get on the cut in May. I am a bit girly and didn't think I would manage

but there you go you dont know until you try, hubby was amazed that they could teach me such skills, hope this is of help to you.

[RLWP]

I may be to late to make an entry about this subject ...........

 

 

the way to go is full speed ahead and then straight back in to reverse with plenty of paddling, with

the tiller...

 

Hi Digi,

 

no old threads never die, and this one isn't even old!

 

I'm interested in understanding more about what you learned on your course. Please could you describe your new skills in a bit more detail so that I can have a go as well!

 

Richard

[stickleback]

Hi Digi. Was it by any chance in Cheshire??!! If so - I think we might have had the same course!

 

Stickleback

[Digitalis]

Hi Digi. Was it by any chance in Cheshire??!! If so - I think we might have had the same course!

 

Stickleback

 

"aahhh its lubbley" how you call me Digi and make me feel like I'm one of you already,and that

you would think that I know what I'm talking about !! and no it was actually on the Shroppie if thats any help, I still dont know if I am allowed to say ??

 

Well I'm not even sure if when I get out on the cut in May on our new baby I will even be able to put it in to practice but as I have told you

the way to reverse is just as I said and I was really doing it I was amazed at the guy who taught us,even when we first got on the boat for the three

day course there was me,Hubby and another bloke,his wife should have come but she had an operation come up and had to go in hospital,any way

Although I had paid my whack for the course I imagined the Guy who was teaching us would leave me out, I'd got my make up on and looked abit girly

and thought I'd watch the world go by and make the tea,however he put me straight to it getting out of the Marina and passing all the moored boats,

I was thinking to myself does he know what he's doing !! I also thought that Hubby and the other bloke thought the same, but because he had given

me confidence from the word go it went great, once when he was showing me how to reverse, the weight of the water on the tiller whilst trying to paddle

became a right hard struggle and pull on the tiller and the teacher actually caught hold of me,and then he apologized for touching me, and I said to him

why would he apologize as its what I would have expected, and he said that a good teacher would not ever need to touch the pupil or ever take hold of the tiller( I am Only little

tho)

and he never did, we all passed with flying colours and I loved every minute of it, he was brilliant,

[stickleback]

I saw someone reversing a hire boat the other day near Stoke Bruerne - I thought he was AMAZING at first - went quite a way, at speed, in a straight line and I thought he must be really expert! Then it all went very wrong and he was wavering about all over, one side of the canal to the other, several near misses if not actual contacts and one of the crew (passengers?) trying to fend off with a pole and then with arms and legs - couldn't watch any longer in case of nasty incidents! So the initial straight line was, I feel, probably beginners luck...

 

Stickleback

[Chertsey]

OK, I am absolutely no expert at all but two lessons I've learnt. Firstly, try to avoid steering in reverse; if you can, manoeuvre by going straight backwards and doing the steering going forwards. Secondly, be bold - i.e. you need more revs going backwards to get any kind of steerage than you do going forwards. Instinct (well, mine anyway) is to wind it down, but this is counterproductive.

[Guest axiom propellers]

I just can't seem to get the boat to go where I want it to in reverse. It's not that I have to reverse very often, but for example, out cruising a few weeks back on a windy day, I wanted to reverse as the wind was bringing me too close to the lock gates before they had been opened. The boat didn't respond at all and luckily there were no other boats around for me to bash into, or embarrass myself in front of!

 

So is there a knack to reversing? Even in wind free conditions no matter where i put the tiller it makes no difference as to where the boat goes.

 

And in your replies please bear in mind: I'm new to boating and not being at all scientifically minded technical terms will be lost on me!

 

Reversing is a bit of a black art. Especially if you do not have the right sized propeller for your size of boat and engine. The information is out the but very complicated to understand. If when you selected reverse, and got no response. I'd be looking very closely at my propeller.

The other thing i would be looking at is the size of you rudder. is it too small.

 

The marine propeller, due to it very design is very one sided. By this i mean all of the water leaving the propeller is all coming from the one side. Thats why you have to put rudder to the opposite position to get any responds. commonly known as 'prop walk'.

 

I hope this hasn't lost you. The answer is in the propeller.

[alan_fincher]

It's the way you tell it, I think.

 

I thought I largely understood the issues, until I read this.

 

But you've certainly lost me!

[Guest axiom propellers]

It's the way you tell it, I think.

 

I thought I largely understood the issues, until I read this.

 

But you've certainly lost me!

 

Your propeller does not give an even flow of water through it. All of the water passing through the prop is forced to one side.

 

So when your reversing, make sure your tiller is in the correct position to compensate for the propellers uneven flow.

 

Have you noticed when trying to stop, the boat 'crab's over to one side?

Edited July 18, 2008 by axiom propellers

[blackrose]

Your propeller does not give an even flow of water through it. All of the water passing through the prop is forced to one side.

 

So when your reversing, make sure your tiller is in the correct position to compensate for the propellers uneven flow.

 

Have you noticed when trying to stop, the boat 'crab's over to one side?

 

Most of us are aware of prop walk which is much more pronounced in astern, but your tiller does not function as a tiller in astern because water is passing the wrong way across it (which is also why the prop walk is so much more in evidence than when the boat's going forward). So the tiller can only function as a rather inefficient deflector in astern and compensating for prop walk with the tiller is often easier said than done. Boats with longer swims (or a long swim to beam ratio in the case of widebeams), tend to fare better. My tiller angle has very little effect in astern whatever I do with it, but if the stern (or bow) starts to wander it's easy enough to rectify by putting it into forward and getting it into the right place again before resuming astern. I'd say that using "back & fill" is just as important as using the tiller in astern.

Edited July 18, 2008 by blackrose

[John Orentas]

Your propeller does not give an even flow of water through it. All of the water passing through the prop is forced to one side.

So when your reversing, make sure your tiller is in the correct position to compensate for the propellers uneven flow.

Have you noticed when trying to stop, the boat 'crab's over to one side?

 

 

Prop walk !

 

It has been called the paddle-wheel effect for the past 50 years, what is different now.. A propeller is close to having a concentric symmetrical performance when comparing one side to another.. The big difference is seen when you compare the top to the bottom, the propeller is very much more efficient in deeper water than in shallow water.

 

There is always a considerable sideways force which is proportional to the axial force, when going forward the effect is not noticeable because the steerer automatically compensates with the tiller, when reversing the steerer does not have that level of control.. As the bottom of the prop. is producing more thrust than the top the stern of every boat will always be pushed to one side depending on the direction of the prop rotation..

 

With a smaller propeller the the depth difference between the top of the prop and the bottom will be much less, therefore the paddle-wheel effect will be less, the only single prop. vessels with near zero paddle-wheel effects are submarines.

[howardang]

Prop walk !

 

It has been called the paddle-wheel effect for the past 50 years, what is different now..

 

I suppose it depends where you come from! It's been called by its proper name, 'Transverse thrust', almost since propellers were invented. Each to his own, I suppose.

 

The thing with PWE or TT or PW (you choose) is that it can be used to advantage because once you know which way your prop rotates, you can allow for it, or use it to help in manouvering. A prop which rotates clockwise when going ahead (right-handed) will push the stern to starboard and therefore the bow will go to port unless corrected. The opposite when going astern. Vice versa for a Left-handed prop.

 

HTH

 

Howard