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Author Topic: Bilge Keels  (Read 2876 times)

sinjon

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Bilge Keels
« on: July 19, 2007, 07:56:55 AM »

Hello,

I have got to the stage of making two bilge keels for my 1:48 HMS Bulldog. There are a few grey area's that I need some advice on.
1/ What material.  2/ How thick.  3/ Is the profile oblong, or trapezium, i.e. do I use filler once they are attached  4/How to attach. 5/ I assume they run parallel to the keel,  but of course at that part of the hull it's all compound curves, now how on earth do you
mark their position ?  - Head scratching time.

Thanks
Colin
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John W E

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Re: Bilge Keels
« Reply #1 on: July 19, 2007, 09:25:13 AM »

hi there Colin

Just so that we dont get confused between stabilisers and bilge keels, I have added a 'scraggy' drawing to the approximate places on the ship.  Like everything else in life, you can guarantee the stabilisers will be different on every ship and so will the bilge keels.  So, this drawing is only shows an approximate position of the aforesaid.

Bilge keels run fore and aft and not necessarily parallel to the keel.  They are normally made up of an 'L'  shaped structure in cross-section where the foot of the 'L' is welded to the hull.    As I have said before these can vary in length and numbers also.    If you can obtain a picture which is on the web of the new River Class Patrol vessel, you will see what I mean. 

Stabilisers these are another subject that vary in number per side and also shape and size.  Normally though they are, as I have drawn, but the cross-section is of an aerofoil shape and these do move up and down in the same way as a wing flap does on an aeroplane, to counteract pitching and rolling movements and normally are independently controlled.

Please bear in mind that this is only a brief description of what they are and where they fit.

If you can either email or telephone Jacobin Plans people, the guy there has helped me out a lot in the past and I am sure he will be able to help you out with the positioning of these.  Also, Paul of PS Ships may be able to help you out.

Hope this is of some help.

aye
John e
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Bunkerbarge

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Re: Bilge Keels
« Reply #2 on: July 19, 2007, 10:14:46 AM »

Bilge keels are fitted to the bilge strake, which is the curved plate that, usually at the midship section, joins the vertical sides to the flat bottom.  The bilge keel is generally 1/3 of the length of the vessel centred on the midship section but, as Bluebird says they are very individual.

They are usually made of "Bulb" iron welded to a flat doubler plate with the bulb outboard and facing down and are tapered towards each end.

It is very difficult to get some strength into such a protrusion on the hull so I made my last ones out of ply with tabs incorporated into their design.  I cut slots through the hull to line up with the tabs and then covered the tabs internally with car body filler.  The whole arrangement was finally covered with a coat of resin.

Stabilisers are very many and varied and can be active or passive, retractable or fixed, or nowadays on yachts even active when the vessel is alongside.

A typical cruise ship fin is about 30 feet long, 7 feet across and can generate 135 tons of thrust at 19knots.  Older ones may have a tail flap but more modern ones will be of a fishtail design, the idea of this being partly to minimise turbulence within the fin box whilst the fin is housed and the vessel is underway.

Basically you do need some drawings or pictures of the actual vessel in question to have an idea of what was
actually fitted.

I did once see a model which I think was a Bulldog and the modeller had connected the stabilisers to the rudders in such a way that the fins countered the heeling effects of the rudders.  Actually relatively simple to do and apparently very effective.
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sinjon

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Re: Bilge Keels
« Reply #3 on: July 19, 2007, 10:31:31 AM »

Thanks Bluebird & Bunkerbarge,

Mine are definitely bilge keels, about 400mm x 5mm. I think I will go with the L shape, and perhaps glue an O section to the edge to give it a better cross section.
The flange of the L should enable me to tape it into position quite easily - mark and then glue.

Thank you both, especially the bonus bits on stabilisers.
Colin
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Bryan Young

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Re: Bilge Keels
« Reply #4 on: July 19, 2007, 07:06:24 PM »

Bilge keels are fitted to the bilge strake, which is the curved plate that, usually at the midship section, joins the vertical sides to the flat bottom.  The bilge keel is generally 1/3 of the length of the vessel centred on the midship section but, as Bluebird says they are very individual.

They are usually made of "Bulb" iron welded to a flat doubler plate with the bulb outboard and facing down and are tapered towards each end.

It is very difficult to get some strength into such a protrusion on the hull so I made my last ones out of ply with tabs incorporated into their design.  I cut slots through the hull to line up with the tabs and then covered the tabs internally with car body filler.  The whole arrangement was finally covered with a coat of resin.

Stabilisers are very many and varied and can be active or passive, retractable or fixed, or nowadays on yachts even active when the vessel is alongside.

A typical cruise ship fin is about 30 feet long, 7 feet across and can generate 135 tons of thrust at 19knots.  Older ones may have a tail flap but more modern ones will be of a fishtail design, the idea of this being partly to minimise turbulence within the fin box whilst the fin is housed and the vessel is underway.

Basically you do need some drawings or pictures of the actual vessel in question to have an idea of what was
actually fitted.

I did once see a model which I think was a Bulldog and the modeller had connected the stabilisers to the rudders in such a way that the fins countered the heeling effects of the rudders.  Actually relatively simple to do and apparently very effective.
Question for you. I once did a stint on the RFA (Helicopter Pilot Training Ship) "Engadine". She had fin type stabilizers ...the only ship in the RFA that had them. Almost without exception the lack of expected movement of the ship when they were deployed caused an amount of sea-sickness amongst the ships permanent crew. Does this still occur with cruise liners?
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Bunkerbarge

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Re: Bilge Keels
« Reply #5 on: July 19, 2007, 09:26:13 PM »

I once saw the Engadine in Falmouth in about 1982 when I was there on a laid up box boat.  When she left a little crowd of wives and sweethearts came and waved hankies and cried.  When we left no-one gave a dam!!

We never have the same issues on cruise ships as 95% of the people here have never seen a wave anyway.  Then 4% can't remember the last time they saw one (I come into that category!) and the remaining 1% are new hires from a real ship in proper waves!

You wouldn't believe how little these things normally move around and the slightest sniff of a wave and we change itineries and get out of the way.  When you are used to box boats on the N. Atlantic it's actually pretty boring from that respect.
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Martin [Admin]

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Re: Bilge Keels
« Reply #6 on: July 19, 2007, 10:14:26 PM »

Is this the model you are building?
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Colin Bishop

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Re: Bilge Keels
« Reply #7 on: July 19, 2007, 10:35:07 PM »

Just a small point which hasn't been mentioned. Bilge keels are normally fitted to the turn of the bilge and their size is constrained by the need not to project either vertically or horizontally from the general run of the hull. By this I mean that if the ship is in dry dock the bilge keels won't touch the bottom and if the vessel is alongside a wall they won't be the first part of the ship to contact it.
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Bunkerbarge

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Re: Bilge Keels
« Reply #8 on: July 20, 2007, 01:17:02 AM »

Good point Colin and the bilge strake is the turn of the bilge.
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sinjon

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Re: Bilge Keels
« Reply #9 on: July 20, 2007, 08:20:22 AM »

Yes Martin - The very one - HMS Bulldog, I still chase every photo I can find.
I have already downloaded the photographs you posted a while ago.
Perhaps Colins point makes the positioning fairly straight forward - put a square across the side of the hull and the bottom where the bilge keel starts and finishes,  mark where both places where it touches, put another mark between them (more or less) - it (theoretically) should give you a centre line (I think)
I obviously haven't tried it yet !

Colin
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Colin Bishop

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Re: Bilge Keels
« Reply #10 on: July 20, 2007, 09:08:01 AM »

It would be interesting to know when bilge keels were initially used. I know they were fitted as experiments to Victorian battleships when they had a major effect in reducing rolling and thus making a steadier gun platform.
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