Model Boat Mayhem

The Shipyard ( Dry Dock ): Builds & Questions => Yachts and Sail R&D: => Topic started by: Tester on September 23, 2009, 09:35:31 PM

Title: Ballast - Steel balls or lead shot
Post by: Tester on September 23, 2009, 09:35:31 PM
Hi

I need to fill a fin keel with ballast, apart from the obvious rusting problem with steel, any thoughts on what's best.

Options seem to be lead shot or steel balls, I think I'm trying to find out what gives the greatest density ie most weight in confined area.

Any ideas

Richard
Title: Re: Ballast - Steel balls or lead shot
Post by: Wasyl on September 23, 2009, 09:55:05 PM
Depleted Uranium {-),its heavier than lead,or there,s Mercury,but thats a Hazardous substance,so you,re better off with good old lead,its cheap, its easily melted,and shaped,

Wullie
Title: Re: Ballast - Steel balls or lead shot
Post by: tobyker on September 23, 2009, 10:07:55 PM
depending on the shape of the keel you could fill it with plaster of paris, extract the plug, make a mould from it and then cast a lead keel insert, to get maximum density as low down as possible.
Title: Re: Ballast - Steel balls or lead shot
Post by: tony52 on September 23, 2009, 10:15:16 PM
Make sure you get genuine lead shot. The shot sold for anglers now has other metals mixed with it to prevent poisoning swans etc. and is much lighter. An angler informed me where he previously attatched 3 weights to his line (of original lead) he now has to attach 5.
For a replica vintage yacht I obtained some real lead from a divers supply shop.
Title: Re: Ballast - Steel balls or lead shot
Post by: amdaylight on September 24, 2009, 12:35:51 AM
The lead shot will be heavier than the steel shoot. I install both the same way in a keel of a sail boat, put the shot in a plastic zip lock bag, pour in your epoxy of choice, seal bag mix shot with epoxy, lay bag on flat work surface and move the shot / epoxy mixture away from one corner and cut that corner off, pour shot / epoxy mixture into keel and then let the epoxy cure. When the epoxy cures it will have encapsulated the shot so it the shot is lead it wont leach out into any water that might get down there, if the shot is steel then the epoxy will keep the water away and the steel shot won't rust. Only one other thing to remember is to get the boat as level in all directions as you can before you pour the shot / epoxy mixture in so it will settle at the deepest part of the keel.  :-))

Andre  :-)
over yonder in Portland Oregon
Title: Re: Ballast - Steel balls or lead shot
Post by: tigertiger on September 24, 2009, 04:11:50 AM
Lead is more dense than steel.

Lead 11340kg/cu.m
Rolled steel (so bearings could be less dense) 7850kg/cu.m

So lead is about 44% heaview by volume
Title: Re: Ballast - Steel balls or lead shot
Post by: Bugsy on September 24, 2009, 09:07:50 AM
I found a cheap supply of lead the other day i.e. free - our local gun club. The pellets from the air-gun range are ideal.
Title: Re: Ballast - Steel balls or lead shot
Post by: dreadnought72 on September 24, 2009, 09:10:37 AM
Lead is more dense than steel.

Lead 11340kg/cu.m
Rolled steel (so bearings could be less dense) 7850kg/cu.m

So lead is about 44% heaview by volume

Very true. And packing spherical shot (whether steel or lead) decreases that density further. You can't get more than 74% of the metal as spheres into a void. Spherical close packing (http://en.wikipedia.org/wiki/Close-packing) for the maths. Given that resin has a density of ~ 2180 kg/m3, the best results for a shot+epoxy casting is:

Lead + resin = 8960 kg/m3

Steel + resin = 6380 kg/m3

Andy
Title: Re: Ballast - Steel balls or lead shot
Post by: Islander1951 on September 24, 2009, 09:53:25 AM
Tungsten is much heavier than lead, so embedding some in lead will bring your C of G down

Look here for more info:

http://www.rcsailing.net/forum1/showthread.php?t=4809&highlight=tungsten
Title: Re: Ballast - Steel balls or lead shot
Post by: Tester on September 24, 2009, 10:16:40 AM
Thanks for all the replies, a lot to think of before ballasting

Richard
Title: Re: Ballast - Steel balls or lead shot
Post by: dreadnought72 on September 24, 2009, 10:44:24 AM
Nice one, Islander!

Tungsten's also almost affordable. A kilo for 121, here (http://cgi.ebay.co.uk/Tungsten-Metal-Cylinder-1kg-element-sample_W0QQitemZ390018595678QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item5aceeb7b5e&_trksid=p3286.c0.m14)!
Title: Re: Ballast - Steel balls or lead shot
Post by: Colin Bishop on September 24, 2009, 10:57:01 AM
That's interesting! I've got a couple of very old ballast weights from a 747 which I think are made of tungsten and they come in very useful for all sorts of things. They weigh nearly 5kg each - Hmmmmmm....

Colin
Title: Re: Ballast - Steel balls or lead shot
Post by: roycv on September 24, 2009, 11:28:35 AM
Hi all, don't forget lead flashing, sold in rolls, as seen in plumbers merchants, can be cut and slid into place or hammered to shape. 
regards Roy
Title: Re: Ballast - Steel balls or lead shot
Post by: Islander1951 on September 24, 2009, 01:34:43 PM
I never said it was cheap, just heavy.... {-)
Title: Re: Ballast - Steel balls or lead shot
Post by: 6705russell on September 24, 2009, 01:57:04 PM
For ballast i always use sand in sandwich bags, easy to alter and position to get a good trim and sits low and flat to the hull....

Russ
Title: Re: Ballast - Steel balls or lead shot
Post by: nemesis on September 24, 2009, 05:48:50 PM
Hi, it is alright using epoxy & lead but I always think what happens if it has to come out for some
reason or other. I always just use lead, moulded & cast to the shape required. Makes carrying the
vessel so much easier if it is removeable.
                                            Nemesis
Title: Re: Ballast - Steel balls or lead shot
Post by: Islander1951 on September 25, 2009, 08:49:23 AM
Melted wax is good for holding lead shot in place, and you can get it out if you want.