Rudder Restoration

[monkeyhanger]

I really wish I had started this thread around 6 months ago, it may have saved the waste of a piece of fabrication one of our volunteers made which, once Python was out of the water was evidently not right for the job in hand and the fantastic discussion amoung a group of people who clearly know a lot may well have been useful in assisting those making a decision about the way forward.

 

My own personal feeling is that as the boat is far from being anything close to original 1929 spec there is no pressure to ensure that the rudder is a faithful reproduction of that spec in looks. I do agree that it does need to be fit for purpose though.

 

Python is due to be refloated tomorrow. There is limited space to keep her out of the water any longer than absolutely necessary at Paul's place. Also as she relies on volunteer crew being available to move her the logistics of meeting a tide to get her back onto The Chesterfield Canal for winter then the need to book a C&RT team well in advance to assist in getting her through the too narrow Stret Lock the logistics get complicated enough without delays.

 

We may still be delayed because there is still a very large question as yet still not answered. Where was all the bilge water coming from on the last leg of the tour. When she was in the water there was no visible area of concern but everyone was certain it would show up when she came out. It did not! The stern gland has been repacked. There was some play but no one is reallt too certain that the bit of play that was there could have caused the amount of water we experienced and still not be visible from inside the engine hole when she was motoring. Tomorrow she will go back in the water and will be run in gear for a period while everyone holds their breath and hopes there are no leaks. If there are then we will move to Plan B. Everyone hopes we don't need Plan B!

 

I am following this discussion with great interest as I have never actually taken much interest of even started to understand the science behind rudder design before now. Thank you for filling a big gap in my knowledge!

In light of the whole discussion on cavitation/aeration/ventilation - perhaps someone can advise what the proper name is for the flat (horizontal) bit on top of the rudder? Also what is the purpose of the bit that sticks out of the water with a hole in it?

 

Just to throw some more ammunition at the argument I have managed to dig up a photo of what the rudder looked like before someone took their nail clippers to it!

 

I suspect that the horizontal bit around the rudder stock will be a piece of thick rubber. It would be there to stop water shooting up the rudder tube and getting the steerer's feet wet. It's probably slipped down the stock an inch or two.

The hole in the rudder blade is so you can attach a rope should you need to remove the rudder for maintenance. Unbolt the ram's head, pull the rudder blade up and out of where it seats in the skeg, allow it to fall free under the boat then fish it out with the rope. Saves on drydocking. Simple and easy!

[kingofthecut]

The hole is so you can remove the rudder in the water. You tie a rope through it and lift the rudder up and of its cup then drop it down into the water with the rudder stock sliding down its tube then when it has all dissappeared into the cut pull up on the rope and you've removed the rudder. Putting it back on is similar in reverse but you need to drop a line through the hole and tie to the top of the rudder stock to. This is after having removed the rams head of course.

[cheshire~rose]

While I have no way of knowing for certain it is thought that what can be seen in that photo is likely to be from the conversion which was done in the 80's

There is no evidence of any support to the skeg or any horizontal strengthening bands on the rudder. It goes without saying that during the conversion most of the things that were done were done to budget and a timescale and there is no way of knowing how many rudders she has had replaced since that time but if it were especially weak then I suspect it would have been upgraded at some point in it's history

 

Thanks for the explanation guys

[Mike C]

 

The hole in the rudder blade is so you can attach a rope should you need to remove the rudder for maintenance. Unbolt the ram's head, pull the rudder blade up and out of where it seats in the skeg, allow it to fall free under the boat then fish it out with the rope. Saves on drydocking. Simple and easy!

 

? Ummm

[Mike C]

I resisted the temptation to do a search but I think we are saying the same thing! Now you say ventilation you might well be right that it is the correct term, I may have made up aeration but you knew what I meant!

I agree with 'kingofthecut'– there seems to be a lot of dictionary readers replying here. It is, and has been for as long as I can recall, been the case that a plate under the counter of a deep narrowboat to assist in holding back when the counter is clear of the water is referred to as an ‘Anti-Cavitation Plate’ . The oldest intact arrangement I have seen has been in place (as is) since the early 1960’s.

 

With reference to the wider debate - Yes, cavitation in a lab sense is exactly as described, with gas (usually oxygen) generated from pressure differences in the water caused by propeller action. But please lets not allow the flexing of intellectual prowess to fuel opportunity to cause changes to known norms in our very limited world of narrowboats. – Narcissism in this forum is silly and ugly

 

Python – You would be wise to seek independent professional advice and listen to them, boats repaired by reacting to all inputs without vetting their validity and worth is likely to cost you heavily in the long term.

 

(Edited for clarity)

Edited September 18, 2012 by Mike C

[RLWP]

? Ummm

 

 

Richard

[kingofthecut]

It is, and has been for as long as I can recall, been the case that a plate under the counter of a deep narrowboat to assist in holding back when the counter is clear of the water is referred to as an ‘Anti-Cavitation Plate’ .

 

I agree it is and always has and always will be I was just mentioning that I had been told this was technically incorrect, I think it was Ric Young when he came back from University! University education eh., you can't beat it.

[Timleech]

I agree with 'kingofthecut'– there seems to be a lot of dictionary readers replying here. It is, and has been for as long as I can recall, been the case that a plate under the counter of a deep narrowboat to assist in holding back when the counter is clear of the water is referred to as an ‘Anti-Cavitation Plate’ . The oldest intact arrangement I have seen has been in place (as is) since the early 1960’s.

 

With reference to the wider debate - Yes, cavitation in a lab sense is exactly as described, with gas (usually oxygen) generated from pressure differences in the water caused by propeller action. But please lets not allow the flexing of intellectual prowess to fuel opportunity to cause changes to known norms in our very limited world of narrowboats. – Narcissism in this forum is silly and ugly

 

 

(Edited for clarity)

 

Mike, if you really want to keep authentic terminology from early pleasure narrow boating days, they were also known as 'cissy boards' - early examples tended to be wooden blocks bolted under the counter.

 

Tim

[Mike C]

Mike, if you really want to keep authentic terminology from early pleasure narrow boating days, they were also known as 'cissy boards' - early examples tended to be wooden blocks bolted under the counter.

 

Tim

Yes, but that’s only a term I heard in the north west, and not for a while – was it a name that Shrubby gave them?

[cheshire~rose]

 

 

The horizontal plate I was talking about is the one you can see in this photo. I had wondered if this was also some sort of anti cavitation device too?

[ricyoung]

I agree it is and always has and always will be I was just mentioning that I had been told this was technically incorrect, I think it was Ric Young when he came back from University! University education eh., you can't beat it.

 

Don't drag me into this!

[kingofthecut]

Don't drag me into this!

 

You're the one who was talking about north sea ferries cavitating at a mile depth!

[Hairy-Neil]

The hole in the rudder blade is so you can attach a rope should you need to remove the rudder for maintenance. Unbolt the ram's head, pull the rudder blade up and out of where it seats in the skeg, allow it to fall free under the boat then fish it out with the rope. Saves on drydocking. Simple and easy!

 

Anyone who's been on the Thames will have noted that the Salters 'Steamers' and other similarly large pleasure boats have a length of chain bolted through said hole and securred to the hull above waterline.

 

DIscuss....

Edited September 19, 2012 by Hairy-Neil

[MtB]

Anyone who's been on the Thames will have noted that the Salters 'Steamers' and other similarly large pleasure boats have a length of chain bolted through said hole and securred to the hull above waterline.

 

DIscuss....

 

It's coz they are punk-boats, I reckon...

 

 

Mike

[cheshire~rose]

It's coz they are punk-boats, I reckon...

 

 

Mike

 

Is the chain secured with a safety pin? If not has anyone done a risk assessment?

[NB Python]

Today Python was supposed to be heading down The Trent back towards The Chesterfield Canal for winter. The crew were hoping to have a much better idea of just what difference that rudder modification by the end of today but there has been a stoppage at the lower end of The Erewash (due to pollution) and Python is trapped behind it.

 

C&RT have told our crew they will allow Python to leave Trent lock when they get there but obviously the situation may change.

[Proper Job]

Anyone who's been on the Thames will have noted that the Salters 'Steamers' and other similarly large pleasure boats have a length of chain bolted through said hole and securred to the hull above waterline.

 

DIscuss....

It's the rudder stop

[ricyoung]

You're the one who was talking about north sea ferries cavitating at a mile depth!

 

If I was then I apologise - I certainly did't mean to mislead, even our tugs don't draw that much (although 20+ feet is quiet a bit)! All I can really add is that due to the relatively small distance from the top of the blades to the free surface, the fairly poor afterbody shape of most narrow boats and the decelerations we expect from a boat when stopping. You cannot really apply big ship or standard marine theory to narrow boats, whether the alterations being discussed make any difference I'll leave judgement to their respective owners.

 

If anyone wants to have a more in depth chat I'd be more than happy to have it, but I suppose this tread isn't the place for it. Ric

[mykaskin]

The horizontal plate I was talking about is the one you can see in this photo. I had wondered if this was also some sort of anti cavitation device too?

 

The plate on the rudder is probably both stiffening, and possibly (and I don't know the technical term) a way of keeping the prop wash from going over the top of the rudder when held at large angles - thus increasing the effectiveness of the rudder. It may also be (used as) a step to aid people out of the water.

 

Agreed, it's often called an anti-cavitation plate when used to reduce ventilation on both narrowboats, outdrives, and outboards. Just pointing out that the processes involved have been poorly named (even in sea boating it appears).

 

Mike

Edited September 19, 2012 by mykaskin

[Timleech]

Yes, but that’s only a term I heard in the north west, and not for a while – was it a name that Shrubby gave them?

 

Probably not heard the name for a while because there aren't many of that type around these days!

 

If they were named by someone I/we know, much more likely to have been Steve Kay or Malcolm Webster. I really don't know, but the name was in use for a long time.

 

Tim

[cheshire~rose]

Thanks for your explanation Mike

 

I have been told by the current crew that the new rudder makes a BIG difference to Python's handling - but now they want hydraulic steering as is is too heavy! - I think getting a full length tiller back on there will be a priority now. They mentioned (with tongue in cheek) getting hydraulic steering. I think I will have a look on eBay for a bull worker for them to build up those biceps!

[Pluto]

Probably not heard the name for a while because there aren't many of that type around these days!

 

If they were named by someone I/we know, much more likely to have been Steve Kay or Malcolm Webster. I really don't know, but the name was in use for a long time.

 

Tim

Shrubby's yard in Runcorn was certainly the source of many boating 'ideas' in the 1970s. Shrubby was larger than life, which was in himself large enough. He used to work the trip boat Lapwing with Charlie Atkins, and fell in at Dutton, suggesting to the passengers that Charlie had pushed him in. Even several years later, Charlie still reckoned that you could see the hole he made in the water.

[IanM]

I agree, the balance blade looks too short. This will result in heavy steering.

 

Mike

 

 

Thanks for your explanation Mike

 

I have been told by the current crew that the new rudder makes a BIG difference to Python's handling - but now they want hydraulic steering as is is too heavy! - I think getting a full length tiller back on there will be a priority now. They mentioned (with tongue in cheek) getting hydraulic steering. I think I will have a look on eBay for a bull worker for them to build up those biceps!

 

[cheshire~rose]

As I have previously said it probably would have paid to post the query before the work was done to gain a census of opinion but hindsight is a wonderful thing.

 

When Mike posted about the "balance" I did not even know what he was referring to - but I do now

 

the steering being heavy will not be helped by the fact that the tiller is rather short too.

[IanM]

Indeed, that's not going to help in the slightest!

 

Python - Braunston Historic Boat Rally 2011 by imulford, on Flickr