Model Boat Mayhem
The Shipyard ( Dry Dock ): Builds & Questions => Yachts and Sail => Topic started 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
-
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
-
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.
-
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.
-
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
-
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
-
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.
-
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
-
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
-
Thanks for all the replies, a lot to think of before ballasting
Richard
-
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)!
-
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
-
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
-
I never said it was cheap, just heavy.... {-)
-
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
-
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
-
Melted wax is good for holding lead shot in place, and you can get it out if you want.