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Author Topic: Boat Davits  (Read 10417 times)

CERES

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Boat Davits
« on: November 27, 2008, 07:28:20 pm »

 :-)I know I can purchase boat davits in plastic on-line but wishing to have a completely scratch built paddle wheeler I am thinking of making my own using either brass rod or even plastic rod which I could form using heat.
My enquiry is does any of my fellow model makers have any ideas with regards to the fixing of pulleys
Thanks   CERES.
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DickyD

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Re: Boat Davits
« Reply #1 on: November 27, 2008, 08:11:25 pm »

Hi Ceres

Check out Bryan Young's General Havelock build, he has some nice close up photos of his davits and pulleys.  :-))

http://www.modelboatmayhem.co.uk/forum/index.php?topic=5905.25
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Bryan Young

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Re: Boat Davits
« Reply #2 on: November 28, 2008, 12:04:02 am »

Thanks Dicky.
I suggest that you browse your local charity shops for aluminium knitting needles....the ones with round heads. If (because of so called Health and Safety rules) you cannot find any, then ask your neighbours. I finished up with scads of them of different sizes..and the neighbours are always proud that they "helped" a bit.
If you are wondering what the fastening bits look like then just ask (on the forum) and I will try to oblige. BY.
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Bunkerbarge

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Re: Boat Davits
« Reply #3 on: November 28, 2008, 12:30:53 am »

My interpretation is at the bottom of this thread:

http://www.modelboatmayhem.co.uk/forum/index.php?topic=6094.msg133861#new
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Reade Models

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Re: Boat Davits
« Reply #4 on: November 28, 2008, 06:58:06 am »

I would think it all depends on the (real life) size of the lifeboats, and whether of not they could be lowered manually on ropes?

Larger lifeboats would surely require some sort of geared windlass system to control lowering?  Sure, the sheaves make lowering lifeboats manually an easier proposition (load x distance) but larger lifeboats would be so heavy as to be very difficult to manage in an emergency, especially if they were full of people?

I've also often wondered how paying out the ropes on a PAIR of davits is controlled so that the lifeboat stays level as it travels down to the surface of the water?  Also, how is swinging of the lifeboat outboard managed?  Presumably one davit at a time, but doesn't this lend itself to potential tangling of lines, and lifeboats hanging over the side at some crazy angles?

Never having been shipwrecked (thankfully), I have no idea of the actual procedures or circumstances. I'm sure the experts can enlighten me?

Malc
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Dave Buckingham

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Re: Boat Davits
« Reply #5 on: November 28, 2008, 07:17:02 am »

The radial Davits I used many years ago.

Order of movement
Push boat aft
Swing out bow
Push frd swing out aft end
Square up
Lower ends using mark one eyeball to keep level.
All done by hand

Dave
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RickF

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Re: Boat Davits
« Reply #6 on: November 28, 2008, 11:26:07 am »

Are these any use?

Rick
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Bryan Young

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Re: Boat Davits
« Reply #7 on: November 28, 2008, 03:13:48 pm »

All good answers. My experience with boats lowered via radial davits showed the following:-
All hands and the cook were needed to lower and hoist the boats...so embarkation was done via the embarkation ladders once the boat was afloat. Dodgy if the ship was sinking or bouncing around / heeling etc.
There would normally be a couple of crew left on board to clear the falls, but the knotted lifelines were always there anyway for those who nedded them.
Given their prime purpose, the boats were not primarily designed to be lifted back up again! Of course they were...but only with a couple of people on board...the rest had to climb the ladder, or use the gangway if it was lowered. BY.
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Bryan Young

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Re: Boat Davits
« Reply #8 on: November 28, 2008, 03:18:04 pm »

All good answers. My experience with boats lowered via radial davits showed the following:-
All hands and the cook were needed to lower and hoist the boats...so embarkation was done via the embarkation ladders once the boat was afloat. Dodgy if the ship was sinking or bouncing around / heeling etc.
There would normally be a couple of crew left on board to clear the falls, but the knotted lifelines were always there anyway for those who nedded them.
Given their prime purpose, the boats were not primarily designed to be lifted back up again! Of course they were...but only with a couple of people on board...the rest had to climb the ladder, or use the gangway if it was lowered. BY.
I should also have mentioned that lifeboats with rope falls were invariably fitted with 3 sheave purchases, and as far as I am aware there is only one way of rigging them to prevent twisting or toppling. I put a photo of this on the forum a while ago, you may find it useful. BY.
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CERES

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Re: Boat Davits
« Reply #9 on: November 30, 2008, 07:19:23 pm »

 :-)) :-))Many thanks for all your replies and pictures. From all this info I should manage to build a couple of pairs.Thanks again.

As always, if you want to know something or have a problem it is guaranteed that someone in our Forum will have an answer. More than you can say for other  forums.
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victorian

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Re: Boat Davits
« Reply #10 on: December 01, 2008, 12:46:21 pm »

I was glad to see this thread because I'm hoping someone can help with a davit question that I've found mystifying! In the picture you can see a davit arrangement common to many late 19th century British warships. But no-one that I've asked, including a number of old sea salts, can explain how it worked. I've even purchased a copy of the 1904 manual of seamanship in the hope of having it explained, but without success!

In the picture the rope (fall?) runs over the first block, around the second block in the boat, and back up to the third block. But then where? It clearly goes back into the boat. Is it secured with a quick release link to the boat, or to the bottom block, or what? Or is the rope secured in some way so that the men in the boat could lower themselves?

Some contemporary builder's models show this davit arrangement, but never in sufficient detail to answer my question. Here's the picture:



Incidentally, the manual of Seamanship does suggest that the chains attached to the top curve of the davit are intended to draw the boat alongside the ship's gunwale for loading, by attaching the top of the chain to the bottom of the boat, causing it to swing in as the boat is lowered. I'd assumed they were there for securing the boat in rough weather or something.
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Bryan Young

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Re: Boat Davits
« Reply #11 on: December 01, 2008, 06:34:35 pm »

Victorian...no wonder you are confused, there are so many bits of rope and stuff in your pic as to boggle the mind.
Are you sitting comfortably? Then let us begin...as they used to say.
All of this reply is my own personal opinion from a seamans point of view. I may very well be wrong...but it may also make sense.
1. I would suggest that the chains are of a length to be hooked on to the lifting hooks and tightened up to relieve the weight on the rope tackles when the boat is "hung off" fo a period of time. So just a relieving device.
2. What I think you refer to as the 3rd rope seems to be just another steadying rope for the davit head.
3. The 3rd block seems to be a simple way of obviating twisting of the falls but also giving scope to re-rig for different weights of boats..the small ones on deck could use the same davits with a bit of jiggery pokery. The "standing part" appears to be attached to a swivellig becket on the lower (larger) block.
4. None of the rigging shows a way of hauling the boat alongside the ship as the "pudding bar" effectively stops the boat swinging iwards whilst the woven canvas straps (clearly visible) stop the boat swinging outwards. I cannot imagine that the men on the boat would lower themselves.
"Normal" ships hold the boat inboard with the aid of "bowsing in" tackles. Again not fitted here.
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victorian

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Re: Boat Davits
« Reply #12 on: December 02, 2008, 10:20:26 am »

Bryan

Thank you so much for that wonderful post! How I wish that I had access to that diagram when I started building Mars!

Nonetheless, I think my arrangement in the models has turned out to be a reasonable, if crude, interpretation of the real thing. The main thing that I've missed because it's always covered in ropes in the photos is the ball head arrangement on the tip of the davit. (Pic below).

Strangely, my original question still stands though because the diagram still doesnt show what happens to the outboard end of the fall. If you follow the 4" cordage under the wood block and up over the fixed block it loops back to the centre of the wood block again and dissapears. This is what happens in all the photos too. What happens to this rope? Is it fastened to the centre of the wood block in some way? This my original question. I think we are in sight of a solution now!

BTW, I was delighted to see the diagram shows the size of the stag horn bollards, the next pieces to go on "Pelorus". In the best photos these bollards are only one or two pixels, although they are shown in the drawings for "Pegasus" that I have. They are missing on "Mars", so come the next refit ....

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Bryan Young

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Re: Boat Davits
« Reply #13 on: December 02, 2008, 04:13:04 pm »

Victorian. Thanks for your comments.
The rope falls are not in an endless loop. I think the picture is misleading. Although the rope appears to "return" I think you willl find ithe end is attached to a becket on the block. What the "odd-ball" rope is doing I have no idea. I suggest you leave it off. If no-one knows what it does then no-one will miss it! Keep it simple, rig straightforwardly and see what you are missing (if anything). The hauling part will go to the cruciform bollard and would generally be hoisted up out of the way (health and safety...and neatness) before going to a reel.
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RickF

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Re: Boat Davits
« Reply #14 on: December 03, 2008, 12:21:53 pm »

This thread is becoming yet another mine of information - thanks, BY and Victorian.

Rick
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victorian

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Re: Boat Davits
« Reply #15 on: December 03, 2008, 07:11:01 pm »

Hope you meant that, Rick, because here's another photo. This appeared in a magazine called "Shipping Wonders of the World" in October 1936 and possibly hasn't been published since. It's the clearest view I've yet found and if you look at the davit in the centre of the picture you can clearly see the 'mystery rope' dissapearing behind the wood block, apparently into the bottom of the boat. It's not fastened to the top of the block. In my models I've tied it off to the bottom of the block where the boat hooks on but that's obviously wrong. (You can see a larger version by clicking the picture)


The caption attributes the photo to the South African squadron but doesn't identify the ship.
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Bryan Young

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Re: Boat Davits
« Reply #16 on: December 03, 2008, 07:32:34 pm »

OK, I give up. I have struggled to come up with an answer for the abbherent rope.
I still say, rig it as well as you can, and then try to work it out. Nothing better than a 3D version to show the requirements.
Sorry, but my level of competence has been reached. BY.
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Colin H

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Re: Boat Davits
« Reply #17 on: December 03, 2008, 10:08:15 pm »

OK guys please don't laugh I do not know anything at all about davits or ships rigging what ever so excuse my terminology but.

In the last pic the pulley blocks all appear to be single wheel the heaving rope leaves the ship and runs through the first pulley. Then down to the centre pulley which is attached to the boat. Then up to the outboard side of the third pulley it then comes of this pulley and drops down behind the pulley which is attached to the boat.

If this is the rope in question it becomes obvious that this rope must be tied off to the boat otherwise the rope would simply run through the blocks and the boat would fall into the sea.

OK I am down behind the wall you can throw your brick bats.

Colin H.
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Ron1

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Re: Boat Davits
« Reply #18 on: December 03, 2008, 10:42:28 pm »

This is how I do it.
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Bryan Young

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Re: Boat Davits
« Reply #19 on: December 04, 2008, 05:58:26 pm »

Victorian: I really wish you hadn't asked the original question as I can't seem to let go of it. But as the weather is so lousy I decided to have a browse and came up with this little lot. By now (hopefully) you are suffering from a sort of brain overload like me. Share the suffering....it's your model!
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victorian

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Re: Boat Davits
« Reply #20 on: December 05, 2008, 03:27:12 pm »

BY - thanks for another marvellous find. We are getting there - pass the asprin!

But it seems even the great Norman Ough didn't know the answer to this. In the text he refers to 'double blocks', while his diagram clearly shows the type of single block we are interested in. However, his diagram has a little spot inked in where the 'mystery rope' meets the wooden block, suggesting it's tied off there. The photos clearly show the rope going past the block toward the bottom of the boat. Oh noooo...

I still have a few lines of enquiry to follow up. If I ever get to the bottom of it I'll report back. Maybe a preserved ship somewhere has this arrangement? Thanks to everyone who has contributed.

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Bryan Young

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Re: Boat Davits
« Reply #21 on: December 05, 2008, 04:09:02 pm »

Victorian....keep asking! Holding "little secrets" to oneself profits no-one. Levels of knowledge on this forum go through the whole range and tapping into it is surely the reason the forum exists....not for personal aggrandisment (of which I have been accused in the past). Keep trying. BY.
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John W E

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Re: Boat Davits
« Reply #22 on: December 05, 2008, 04:57:55 pm »


This may be of some help ?
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Bunkerbarge

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Re: Boat Davits
« Reply #23 on: December 08, 2008, 10:57:39 pm »

I think there is a possibility that this rope, although tied off to the block, may also be left with a tail hanging down to assist in handling the blocks when the boat returns to the ship.  It is a lot easier to get hold of a rope and pull the block into position with it than it is to get hold of the block itself, which may have been raised slightly to keep it out of the water and to make recovering it again that bit easier and safer.

Just a thought as I've seen ropes used to handle falls in this way.
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Bryan Young

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Re: Boat Davits
« Reply #24 on: December 09, 2008, 05:29:23 pm »

I think there is a possibility that this rope, although tied off to the block, may also be left with a tail hanging down to assist in handling the blocks when the boat returns to the ship.  It is a lot easier to get hold of a rope and pull the block into position with it than it is to get hold of the block itself, which may have been raised slightly to keep it out of the water and to make recovering it again that bit easier and safer.

Just a thought as I've seen ropes used to handle falls in this way.
Hi,Bunker, interesting thought. Are you suggesting that the "rope in question" is really just a handy handling device? If so, I take my non-existent hat off to you. For a clankie you seem to be pretty bright! Good thought. Bryan.
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