Ballast – what is best?

[Brian MuirParticipant @brianmuir84327]

[Brian MuirParticipant @brianmuir84327]

I have now fitted the deck, but have left access to the middle 6 frames so I can place ballast in the hull. When I floated the boat, I tried filling it up with stones to get it to float at the same waterline as the plans. They weighed 1.5 kg.

I got a piece of lead bar from my local scrap yard (free!) and bought some lead weights from a diving warehouse. I'm a bit reluctant to fix lead to the keel, the plans show a cut out section of the timber, to be replaced a by lead. I have hammered the bar into the shape to do this. How could I fix it in place, screws into the keel?

Can I get away with putting the lead weights inside the hull between the frames at keel level?

I checked the plans and the main mast is going to be about 30 inches tall! That seems a massive lever for capsize forces. This probably means that any weight will have to be on the keel, as low as possible as a counterbalance.

How do I workout how much ballast will be needed altogether?

[Paul TParticipant @pault84577]

Hello Brian

I have always found it best to fit the counterweight as low as possible so screwing it to either side of the base of the keel is the ideal solution.

After fixing to the keel the lead can be shaped into a smooth bulb shape so always fit more lead than necessary to allow for removal.

There are all sorts of different calculations to work out ballast but the problem with a yacht is that the centre of mass keeps changing as the wind force changes, sometimes the easiest method is trial and error.

I hope this helps

Paul

[Colin BishopModerator @colinbishop34627]

Paul is right. The lead needs to be kept as low as possible and placing it inside a model is unlikely to provide the required righting force.

You could probably get away with attaching strips of lead each side of the bottom of the keel and then fairing off the leading edges. The amount of lead to use will be dictated by what is required for the model to float at the designed waterline. If that doesn't produce enough righting force then you would need to deepen the keel as adding more weight would just pull the boat under!

Colin

Edited By Colin Bishop, Website Editor on 22/08/2013 21:16:43

[Malcolm FraryParticipant @malcolmfrary95515]

If 1.5Kg is what takes it to waterline, then thats what you have to play with. If the lead is to fix directly under the keel, then a couple of screws will help, but the main fixing should be the layer of epoxy that lies between lead and wood. If the lead can be fixed to a deeper fin, a good arrangement is to have a pair of "saddles" with through bolts with the heads and nuts in recesses. Again, epoxy between wood and lead, and the lot faired in.

If there is plenty of beam and freeboard, it is surprising how much heel can happen before the rail gets under water, but if sailing becomes survival rather than navigating, it might be a good idea to look at ways of reefing at an early stage of the build, just to make sure it can be done.

[Brian MuirParticipant @brianmuir84327]

Thanks to Paul, Colin and Malcolm, I think I will have to go for fixing to the keel. Instead of cutting out a section I might make two "saddles" to fit either side.

This might seem a bit dim, but how do you shape the lead when its in place, a file seems a bit of a job, perhaps a grinder?

[Paul TParticipant @pault84577]

Brian

Lead is a very soft metal and can be shaped with a shavehook or a surform I wouldn't advise using a grinder as lead is toxic and you don't want microscopic bits floating around in the air.

Take some simple health precautions before starting such as work outdoors, wear gloves, eye protection and a good P2 type dust mask (not one of those cheap paper masks)

Remember to start off with more than 1.5kg of lead as the shaping process will obviously reduce the weight.

A good method of fixing is to drill through both pieces of lead and the keel and then use bolts to hold the whole thing together, you will have to counter sink the holes to recess the bolt heads and nuts, these holes are then plugged with filler.

After working with lead it is advisable to have a good shower just to make sure every scrap of dust is washed off. This might sound like an over reaction to a perceived problem but lead poisoning is very serious.

Paul

 

Edited By Paul T on 23/08/2013 11:26:11

[Colin BishopModerator @colinbishop34627]

Lead responds well to just bashing it with a hammer, especially if all you want to do is to round off a corner!

Colin

[ashley needhamParticipant @ashleyneedham69188]

Check out sacrificial anodes at a boat chandlers. You may just get something approximately the right weight and streamlined already. Simply glue on and drill two holes to bolt through , fill with P38.

On my sailing herald I simply had a flat keel with two holes in, and a few slabs of lead with holes drilled through for bolts, so i could easily adjust the weights so I then knew how heavy i needed the keel to be. THEN I found (after the article) a pair of sacrificial anodes to use and now have something respectably hanging on the bottom.

Ashley

[Brian MuirParticipant @brianmuir84327]

Thanks to all, I have decided that as this is a rough prototype I will just bolt two lead weights either side of the keel to test it for stability and hopefully see how it sails.

[Malcolm FraryParticipant @malcolmfrary95515]

You will be able to check stability, but unformed lumps will have a terrible effect on hydrodynamic performance, so once you know the weight required, get to the shaping as soon as possible.

My procedure with a yacht weight was to get the volume by dunking the weight of lead in a jug of water, remove the lead, replace it with plasticine until the jug was full again, shape the plasticine and use that to make a "master". I then used that to make a mould (plaster of paris and a long time in a low oven to totally dry) and poured molten lead. If you know the precautions to take, OK, if you need to ask, think about getting the shape another way. Lead is quite nasty stuff. As room temperature metal, its toxic, at melting temperature, it gains many more ways of amplifying its dangers.

Like Colin says, if placed on a solid enough surface, it will repond to physical violence.

[Brian MuirParticipant @brianmuir84327]

I decided on the brute force approach and hammered the lead into the shape I wanted, the when I had fixed it with epoxy and removed some material.

I tested the effect in my trusty wheelbarrow tank (see pic) and even whenheeled over on the beam end, it sprang back and settled quickly. I was also very impressed by the way it dealt with such a massive heel. The dodgers on either side of the cockpit, which I had thought of as a bit of styling, actually did a great job of holding back the water so that even on the beam end, no water poured into the cockpit! (see pic below)

Hats off to the designer.

[Brian MuirParticipant @brianmuir84327]

I took her out for the maiden voyage this afternoon, she didn't sink, let in water and no bits fell off or broke….. but even in very light winds she heeled over a lot, I think I will need more weight on the keel for the next one! This is a screen grab from a phone video, sovery poor quality.

[Paul TParticipant @pault84577]

Brian

You might have to extend the length of the keel to place the counterweight lower to resist the turning force created by the sail area.

Paul

[Brian MuirParticipant @brianmuir84327]

I added two strips of lead (hammered into rough shape and bolted on) either side of the existing lead keel, and this was enought to stop her heeling so far. In a stronger wind, she just heeled over enough to dip the rail in the water and sailed beautifully.

Thanks to all for the adivce.

[Kimosubby ShipyardsParticipant @kimosubbyshipyards]

Brian,

now enjoy the sailing!

I expect you'll soon have another on the blocks though??

Glad to have particpated in the advice group, and that you have a working outcome,

Kim

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