Collision Bulkheads

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Collision Bulkheads

Postby Wild Rose » Tue Feb 26, 2013 7:59 am

Quick question on collision bulkheads,

I have been reading about a few ocean going boats and they talk about the requirement to have them. Whats the thinking here? Am i wrong to think that most the things that we might hit out at sea, will be submerged, not head on? (excluding docking ;) )
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Re: Collision Bulkheads

Postby Phillip » Tue Feb 26, 2013 8:57 am

Morning Wild Rose,

Collision bulkheads are usually in SHIPS where the bulk of the holds are too big such if they were breached the ship would sink.
By limiting the area with collision bulkheads the amount of water that gets into one area will not sink the ship.

Remember several of the Titanic's were ripped open and that’s why it sunk, and I think they were open to each other at the top. :shock:

So, with a Top Hat where are you going to install a collision bulk head?
Remember it’s got to be closed off ALL the time or what’s the point of having one!

The odds of actually using a collision bulkhead are so small its not worth mentioning.
If you do need to use one, well that problem will be the least of your problems. :o
Phillip.
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Re: Collision Bulkheads

Postby Dolphin » Tue Feb 26, 2013 10:06 am

I beg to differ Phillip.
On a short trip from Broken Bay to Port Hacking we came across a sling lot of timber that was lost from a ship. There were about 30 pieces of 6" x 12" 12 feet long between Broken Bay and Bondi (about 20miles). It was lucky we did the trip in daylight and saw them.
On another occasion when I was on Coast Guard Radio duty a fishing boat had its prop shaft ripped out as it went over a container at speed on its way to Browns Mountain off Maroubra.
It is a good Idea if you can fit a collison bulkhead. Filling in the part bulkhead immediately behind the anchor locker would be a good start.
Sealing the cockpit locker lids in the V Berth would be another place to start.
I'll try and dig out a photo of a yacht that hit a ship and lost its bows. Its dramatic.
Yes a collision bulkhead is a good idea and easy to install.

Remember; The Titanic was built by professionals, Noah's Ark was built by amatuers.
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Re: Collision Bulkheads

Postby Troppo » Tue Feb 26, 2013 1:42 pm

While this is not exactly about bulkheads I think it relevant: Last Friday a power boat hit a log near Barren Is (5 nm E off Great Keppel Is, 14nm East of coast). Don't know the damage but the boat did make it back to shore at reduced speed. With the floods there is an enormous amount of floating debris about, I saw logs almost as long as Windchaser floating down the river. I am not sure how hard a 'knock' would need to happen to hole a Top Hat, given their excellent build, but if the front section which originally was a sail locker was watertight then a hole in the bow would not sink the boat. For me, sealing that section would depend on whether I thought the risk of holing was high enough to warrant doing. Certainly, if it happens it would be a serious complication.

boat hits log news article [Oh, the pic in the news article is of a sunken boat, you can make out its shape underwater.]
http://www.themorningbulletin.com.au/news/log-trip-with-coast-guard/1769932/
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Re: Collision Bulkheads

Postby bearmcnally » Tue Feb 26, 2013 2:58 pm

Hello Hatters

Crash bulkheads in Top Hats ? The fore-peak bulkhead is a basic crash bulkhead . If you a talking sealed water tight ones why ? We only own small EX JOG yachts not icebreakers .I think if you were going to cruise into a situation that required that sort of construction I don't think you would want a Top Hat !

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Re: Collision Bulkheads

Postby storm petrel » Tue Feb 26, 2013 7:38 pm

I agree Bear, if I wanted to sail across an ocean I would not not do it in a Top Hat. Not that a Top Hat couldn't do it. It is just that it would be very slow and very uncomfortable. In any event, collision bulkhead or not, you would be foolish to venture beyond the continental shelf without a liferaft.
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Re: Collision Bulkheads

Postby Shaun » Tue Feb 26, 2013 8:46 pm

Gday,
I am in the process of creating collision bulkheads/waterproof compartments in Blue Moon, I have not stored anything under the V-berth, instead I have packed them with empty 1.25lt & 2lt drink bottles, dont know if its a good idea with the drink bottles, my theory is if the hull is holed in that area, the compartment wont fill completely with water, & the bottles will provide some bouyancy, if they dont float away.
When I get some spare time, ill make the compartments waterproof. And will make the pointy end waterproof too, & if I can find some bulk decent cheap floatation, ill stuff it under the cockpit, & any other spare spots.
I think its a good to make the mothership the liferaft, mind you I havent done any calculations as to how much floatation would be needed to keep all that lead & a cabin full of water afloat.
Got the inspiration from Roger Taylor, he shows how he made his Corribee unsinkable on his website www.thesimplesailor.com

cheers
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Re: Collision Bulkheads

Postby Phillip » Tue Feb 26, 2013 9:25 pm

:shock:
I can't believe these posts.

As Bear has said Top Hats are too small to even consider collision bulkheads.

Why are you guys even thinking about this is beyond me. Even if you completely sealed off
all the compartments mentioned they will not be enough to stop you sinking!!

The volume needed to stop a Top Hat sinking is about that of the volume of the main cabin, so where the hell are you going to find THAT!

There is a system that involves a large inflatable bag, but it needs a couple of scuba tanks to inflate it. So where to hell would you put all that on a Top Hat!!

The Top Hats that I know of that have come to grief have ALL run UP onto the HARD STUFF where they didn't SINK but came to grief with the rocks!!

If I was going fast enough [like the speed boat already mentioned] in my Top Hat I would really be scared about hitting something, but only for a few seconds as I have only done a max of 11 knots for a very few seconds on one occasion.

Design wise, if bulkheads were required in Top Hats Illingworth and Primrose would have included one in the design.

They didn't, so lets go onto something else.
Phillip.
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Re: Collision Bulkheads

Postby Dolphin » Tue Feb 26, 2013 9:52 pm

With all respect Phillip I think the risk is real as I have shown in at least 3 cases and Louis confirms withthe amount of rubbish out there. I've seen a boat in Gladstone that hit a ship and lost the bow. I think that for a small amount of effort that the forward part of the bow can be protected. Just saying it has never happened doesn't mean that it wont happen.
Bear even says that the forpeak bulkhead is a collison bulkhead, well its not if its not watertight.
There have been posts about sea cocks being broken off and the vessel nearly sinking. That has been reported in this forum as a reprint from a newspaper article. If the V Berth furniture moulding was sealed by fitting watertight hatches, and that is easy to do, it would save the integrity of the hull.
I agree that filling the inside of the boat with floatation is impractical and a few simple calculations rule that option out.
Just allowing for the lead in the ballast alone, 1250kg you would need 1250l of displacement. That means you need 625 2 litre containers. If you put them low down the hydrostatic pressure will reduce their volume so you would need more, say 30% more. Lets not go there!
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Re: Collision Bulkheads

Postby Killick69 » Wed Feb 27, 2013 3:53 am

A wooden fishing trawler came onto the hard just ahead of us at Fenwicks yesterday. She sank off Refuge bay on Sat. Broke mooring in Refuge bay and hit rocks. Don't know what she was doing moored in Refuge and don't know how deep under water she went. Do know there is a hole about 1 metre radius in her Starboard side.
Cheers, John
P.S. Quick look through the hole did not show any compartments.
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