chains to stop the hull spreading.

[luctor et emergo]

I'm about to remove the forward part of the cabin from my boat, creating an open hold. At the front the original riveted cross brace is retained, combined with a solid bulkhead, and roughly in the centre I will retain the existing bulkhead (to gunnel level), but in the middel of that (a space of some 23 feet) I may need to add another cross brace to take the strain of the hull sides, when I have loaded up with coal. Towards the rear the hold will be closed with another bulkhead (for the cabin), but that part of the hold will contain various tanks, which will bear on the floor, rather than the hull sides.

 

My question is, can I attatch a chain and tensioner to the top of the knees, or do I need to attach the chain to the actual hull sides? Considering that I wont be loading more that 200 bags max (probably less) which is about 5 ton, , about 5 bags high, and thus the strain on the hull sides won't be very high..

 

Thanks

[Speedwheel]

Chains will be necessary for when travelling empty to stop the sides spreading. When you are loaded you will need beams to stop the hull sides bending in. As you load, the pressure from the outside of the hull increased as it gets lower in the water so the beams hold the sides apart.

Edited August 2, 2010 by Speedwheel

[RLWP]

Chains will be necessary for when travelling empty to stop the sides spreading. When you are loaded you will need beams to stop the hull sides bending in. As you load, the pressure from the outside of the hull increased as it gets lower in the water so the beams hold the sides apart.

 

That's brilliant! It's so obvious when explained, but the opposite of what you think based on casual observation. Thanks for that, I've learned something

 

Richard

[luctor et emergo]

Ahhaa, I have learned something as well. So in effect, beams will work both ways? A beam it is then. I will have to source a suitable piece of beam, which shouldned be to difficult.

 

Thanks Speedwheel

[RLWP]

Ahhaa, I have learned something as well. So in effect, beams will work both ways? A beam it is then. I will have to source a suitable piece of beam, which shouldned be to difficult.

 

Thanks Speedwheel

 

Might explain why you are getting stuck in narrow locks too

 

Richard

[Speedwheel]

No, you will need beams and chains. Beams to hold the sides out and chains to hold them in.

 

Here we go, best pic I can find at the moment. The boat is loaded so the chain is slack and the beams are holding the sides apart. When unloaded the chain will be tight, holding the sides in, and the beams will be loose on their supports.

 

Edited August 2, 2010 by Speedwheel

[WotEver]

How clever - I had no idea...

 

Tony

[mykaskin]

I only took one chain and beam out from Victoria during unloading (more or less in the middle of where the 18 tons of gravel was), and while the chain was a little lose with the weight, there was little force on the beam. For 5 ton, and persumabably the rest of the with a cabin I wouldn't worry too much.

 

Richard Horne's Arundel doesn't have any beams or chains, using angles to the bottom to provide the nessesary structural strength.

 

Cheers,

 

Mike

Edited August 2, 2010 by mykaskin

[J R]

No, you will need beams and chains. Beams to hold the sides out and chains to hold them in.

 

Here we go, best pic I can find at the moment. The boat is loaded so the chain is slack and the beams are holding the sides apart. When unloaded the chain will be tight, holding the sides in, and the beams will be loose on their supports.

 

 

They say you learn something every day, and with your concise and precise illustrated reply, have certainly done so. Never knew and it all makes sense when you think about it. Well done and a good post.