Alternative to pilings

[blackrose]

I wasn't sure which sub-forum to post this on?

 

I've got a mooring on the Thames but I need to organise some poles or pilings to prevent my boat being stranded high & dry in the event of flooding.

 

Fixing vertical poles or pilings is difficult as I don't have the equipment to sink them in the river bed and the very edge of the bank is held in place with only with fairly flimsly corrugated metal which would not be suitable for fixing poles against.

 

So I've come up with this idea (I'm sure I'm not the first one), in which the boat is held away from the bank by two horizontal scaffold poles attached to the boat's cleats with large shackles allowing some movement like a hinge. I'm not sure how the poles would be attached to the bank but it would be something similar, allowing the poles some freedom of movement.

 

 

 

Sorry about the quality of the images. The straight lines in the first image are poles and the curved lines are slack ropes. The cleat in the second image is on the boat.

 

When the river rises the boat goes up and may even rise over the bank, but when the water recedes the boat is pushed back out and cannot "land" on the bank.

 

I would appreciate any constructive comments or suggestions especially from anyone with experience of this sort of thing.

 

Thanks - Mike

Edited April 25, 2010 by blackrose

[carlt]

I don't know if you've enough room, before you're obstructing the channel, but I have two mud weights, fore and aft, which pull the boat away from the mooring, when the tide comes in

[blackrose]

I don't know if you've enough room, before you're obstructing the channel, but I have two mud weights, fore and aft, which pull the boat away from the mooring, when the tide comes in

 

Yes, there would be enough room for that - so you mean you drop the mud weights on the river side away from the boat and tie them off, and as the level rises the you are pulled out? They'd have to be big weights wouldn't they? I'd worry about the boat dragging them along the bottom.

[MoominPapa]

A cunning scheme which is popular on the River Nene, is to fit at couple of 50mm towing balls to the boat, front and back. At the mooring there are two scafolding poles hinged so that they can pivot up and down, with trailer hitches on the end that connect to the 50mm balls. It's basically your scheme but using trailer hitches rather than schackles. The other part of the scheme is that one or both of the poles is actually a triangular frame with two hinges on the bank. This stops the boat from moving up or down stream without needing to use ropes.

 

MP.

[blackrose]

A cunning scheme which is popular on the River Nene, is to fit at couple of 50mm towing balls to the boat, front and back. At the mooring there are two scafolding poles hinged so that they can pivot up and down, with trailer hitches on the end that connect to the 50mm balls. It's basically your scheme but using trailer hitches rather than schackles. The other part of the scheme is that one or both of the poles is actually a triangular frame with two hinges on the bank. This stops the boat from moving up or down stream without needing to use ropes.

 

MP.

 

Thanks, I'm not quite sure how trailer hitches work and what sort of attachments I'd need to fix to the boat, but I'll look into it.

 

Doesn't the opposing angles of the poles in my picture do the same thing as a triangle frame (i.e. stop fore and aft movement)?

[Guest wanted]

If you could knock vertical scaff poles into the bank, maybe you could attach the Horizontal ones going to the boat, using swivel scaff clamps?

 

 

Uploaded with ImageShack.us

Edited April 25, 2010 by wanted

[MoominPapa]

Doesn't the opposing angles of the poles in my picture do the same thing as a triangle frame (i.e. stop fore and aft movement)?

Triangles are much stronger than quadrilaterals. Given the fixed lengths of the poles and the boat and the bit of bank between poles, there are lots of different quadrilaterals differing only in the angles at the corners. To avoid the boat moving you have to make the pivots of the poles control the angle: that's hard. For a triangle , once you fix the lengths of the sides you fix the angles at the corners.

 

One way to think about it is that your angled poles are one side of the triangle, you just need to add a second pole to each going straight from the boat to the bank. Those keep the boat a fixed distance from the bank whilst the angled poles stop fore and back movement.

 

A picture would be much better here, I'll try and sketch something soon.

 

MP.

[MoominPapa]

This is a hitch, which you'd bolt at the end of the scaffold pole:

 

 

and this is the 50mm ball if locks onto, which would be attached to the boat.

 

 

and here's my very bad diagram of how it goes together: the red line is the common pivot axis for all the landward ends of the poles and the blue line is the edge of the bank.

 

 

The hitches release easily by lifting the handle: you probably want to get the sort that will take a padlock....

 

MP.

[carlt]

Yes, there would be enough room for that - so you mean you drop the mud weights on the river side away from the boat and tie them off, and as the level rises the you are pulled out? They'd have to be big weights wouldn't they? I'd worry about the boat dragging them along the bottom.

They're 56lb mudweights with about 20' of chain and 15' of rope.

 

I'm moored against telegraph poles so there's no danger sitting on the barge, that acts as a pontoon, the mudweights are there to stop the boat rubbing against the poles.

It is quite important to get home on time, when on a mud berth, btw.

Edited April 25, 2010 by carlt

[Guest User]

They have the towing ball & hitch method on the Great Ouse too ... viewed looking at the boat end on, it kind of looks like this. As you can see the only way the boat can swing as the water rises is away from the bank .... and the bankside pivot is usually raised about 6 ft ...

[DHutch]

Thanks, I'm not quite sure how trailer hitches work and what sort of attachments I'd need to fix to the boat, but I'll look into it.

Just as per the shackle, but with a ball and socket, rather than post and shackle

 

Doesn't the opposing angles of the poles in my picture do the same thing as a triangle frame (i.e. stop fore and aft movement)?

In a word. No.

- Its just the same as mooring without springs relies fully on the boat being hard against the bank not loose.

- You need something diagonal. For which if it where me, i would use some rope or steel wire across the diagonals. (just like springs)

 

 

Daniel

[blackrose]

If you could knock vertical scaff poles into the bank, maybe you could attach the Horizontal ones going to the boat, using swivel scaff clamps?

 

 

Uploaded with ImageShack.us

 

Not a bad idea. I hadn't seen those swivels before and they could be useful higher up on the bank end where I can hammer vertical poles in.

 

This is a hitch, which you'd bolt at the end of the scaffold pole:

 

 

and this is the 50mm ball if locks onto, which would be attached to the boat.

 

 

and here's my very bad diagram of how it goes together: the red line is the common pivot axis for all the landward ends of the poles and the blue line is the edge of the bank.

 

 

The hitches release easily by lifting the handle: you probably want to get the sort that will take a padlock....

 

MP.

 

Thanks, that's given me some good ideas. Now - just need to work out how to attach the poles to the bank. I guess the higher I can get the fixing point on the bank the better in terms of not exceeding the operating angle of the trailer hitches.

Edited April 26, 2010 by blackrose

[blackrose]

They have the towing ball & hitch method on the Great Ouse too ... viewed looking at the boat end on, it kind of looks like this. As you can see the only way the boat can swing as the water rises is away from the bank .... and the bankside pivot is usually raised about 6 ft ...

Where would one procure these trailer hitches? Ebay?

[carlt]

Where would one procure these trailer hitches? Ebay?

I bought one from my local caravan suppliers, for the tender trailer, recently.

 

About £20 iirc.

[blackrose]

I bought one from my local caravan suppliers, for the tender trailer, recently.

 

About £20 iirc.

 

Thanks this one says it's rated at 750 kilos. Is that going to be sufficient for a 32 tonne boat in flood conditions on the Thames?

 

http://wap.ebay.co.uk/Pages/ViewItemDesc.a...781&emvcc=0

Edited April 25, 2010 by blackrose

[DHutch]

Yeah, i would buy the hitch new from a trailer place (trailer parts warehouse, peak trailers, or locally) then the ball you can either buy from the same or else pick up from a scrappy for about £5 a pop.

 

I would also then for belt and braces have both ends of the pole secured with length of rope i think. Although i guess you will have the mooring lines as well as the poles already.

 

 

Daniel

[blackrose]

Yeah, i would buy the hitch new from a trailer place (trailer parts warehouse, peak trailers, or locally) then the ball you can either buy from the same or else pick up from a scrappy for about £5 a pop.

 

I would also then for belt and braces have both ends of the pole secured with length of rope i think. Although i guess you will have the mooring lines as well as the poles already.

 

 

Daniel

 

Yes I guess if I double up with rope it should be ok, although I am beginning to wonder what advantage the trailer hitch has over a short piece of chain bolted through the end of the pole wrapped around a cleat on the boat and padlocked back on itself?

Edited April 25, 2010 by blackrose

[MoominPapa]

Yes I guess if I double up with rope it should be ok, although I am beginning to wonder what advantage the trailer hitch has over a short piece of chain bolted through the end of the pole wrapped around a cleat on the boat and padlocked back on itself?

 

Lack of clanking when the boat rocks?

 

MP.

[Grace and Favour]

Yes I guess if I double up with rope it should be ok, although I am beginning to wonder what advantage the trailer hitch has over a short piece of chain bolted through the end of the pole wrapped around a cleat on the boat and padlocked back on itself?

 

And trailer hitches are very easy to disengage should you need to do so in a hurry.

[WJM]

What about attaching two or three poles to the boat. It would be fairly easy to secure them to the fender attachments, sticking down into the water below the hull. This could be a much simpler and neater way than trying to rig fixings on the bank. They would be much more portable too. You could take them with you on your travels and use them anywhere.

 

I would be nervous of using mud weights for this purpose. The river could rise enough to lift them off the bottom, or in a strong stream the weights could be moved along the river bed.

 

Where is your new mooring?

[blackrose]

What about attaching two or three poles to the boat. It would be fairly easy to secure them to the fender attachments, sticking down into the water below the hull. This could be a much simpler and neater way than trying to rig fixings on the bank. They would be much more portable too. You could take them with you on your travels and use them anywhere.

 

I would be nervous of using mud weights for this purpose. The river could rise enough to lift them off the bottom, or in a strong stream the weights could be moved along the river bed.

 

Where is your new mooring?

 

I'm not sure how that would work?

 

Wraysbury.

[carlt]

I would be nervous of using mud weights for this purpose. The river could rise enough to lift them off the bottom, or in a strong stream the weights could be moved along the

Well the levels at my mooring changes around 3 metres, twice a day and once a month is over a metre above the pontoon and my mudweights have never moved.

 

My chains and ropes could accomodate a tidal height that would flood much of Essex, before the ropes are vertical and pulling the weights out of the mud.

 

How long are you proposing your poles, fixed to the boat be?

[WJM]

If you have a scaffold pole attached to the side of the boat and protruding two or three feet below the baseplate, then the boat would not be able to move onto the flooded bank. I am assuming a fairly well defined bank of course, campshed or similar.

 

My river mooring has scaffold poles set into the bank but they are about six inches in from the edge. I have seen a chined cruiser hull hang up on this gap. I am not sure how a narrowboat would fare, at best it might develop an alarming list before falling violently. During floods, I tie my boat pole vertically to the side of the boat to prevent it getting onto bank.

[carlt]

If you have a scaffold pole attached to the side of the boat and protruding two or three feet below the baseplate, then the boat would not be able to move onto the flooded bank.

So, if the pole protrudes, say, 3 feet and the boat draws, say, 2'6", then the river need only rise 5'7" before your poles can float over the bank.

 

My mudweights can hold the boat away from it's mooring with a water rise of over 25', on a really high tide after which the flood defences would fail anyway and a hung up boat would be the least of peoples' worries.

[WJM]

Well I think Blackrose would be ok. The Thames is not likely to rise by 5'7" :-)