Encapsulating ballast

[mel80]

Hello.

Not really construction, as such, but close enough to go in this forum, I hope.

I am, at the moment, looking at buying a second hand GRP sailing boat; a 27ft long keel yawl (1984) with the keel integral to the hull moulding. The boat was bought as a bare moulding by the previous owner and he has finished her to a pretty high standard in all but one respect: the lead ballast (consisting of 5kg ingots) is completely unsecured!

He has obviously been happy to sail like this for over 20 years, but it would worry me greatly.

I understand that it is possible (and was probably intended in the design) to secure the ballast in the keel by pouring a resin mix around the ballast.

My questions are:

1. What resin/ mix should I use?
2. Will this be sufficient to hold the ballast in place under all conditions, or would additional security be needed?
3. Will I need to prepare the inner surface of the keel in any way to ensure good adhesion?
4.Are the lead ingots a reasonable form of ballast, or should I consider selling them and buying smaller units?
5. A very approximate idea of cost? I know that this depends on many factors, but even a very rough idea would be useful?

Thankyou.

[gonzo]

Large volumes of resin overheat and burn when curing. You can set the lead pigs in cement, a very traditional method. To make sure it won't come loose, even in a capsize, you can laminate short wood pieces to the inside of the keel hollow. The cement and lead will harden around them and won't ever move.

[mel80]

Thanks for that. I hadn't thought about using concrete, but it does make sense. I imagine that concrete is also a bit more dense than resin. That said, it must be possible to do it with resin also. Is the heating issue the reason why people use additives, such as silica, mixed with the resin?

[gonzo]

Aditives are used to modify the viscosity or other characteristics of a resin.

[Howgegoboat]

Hi
How about melting the lead insitu using a blow torch, or on the boat stove?
If you dont mind the fumes, this will result in a lower CB, or how about chopping down into small ingnots which can be secured easier.
Or I might be barking up the wrong tree!
I am about to cast a 300kg concrete keel for my boat,
Yours James

[gonzo]

If you torch the fiberglass in the keel it will go up in smoke. The fumes from melting lead are very toxic. A cast keel must be melted and poured in one piece. If not, it will come apart. It takes a fair piece of equipment to handle thousands of pounds of molten lead.

[longliner45]

correct me if im wrong ,,, I dont know if you have a cavity in the keel you are intending to use ,,,or if this is a bolt on ballast, if it is a bolt on ,, a cast iron bath tub,,bonn fire and wooden mold are good,, if it is a cavity you could make sections of lead or put the lead in with a additive as afore mentioned,,,,also like gonzo said ,,fumes from the lead are very bad,,hence lead poison,,,look up woodenboat .com and you will find (with some searching) how aprentice boat builders pour lead ,,whatever you do ,,be carefull......longliner

[mel80]

Thanks for the replys everyone.

Longliner: Yes; it's a cavity in the keel.

Howgegoboat: To be honest, I'm not all that keen on lowering the CB; the design was for iron ballast so it's already pretty low and, as she'll be used for cruising, I'd prefer not to make her too stiff. Thanks for the suggestion anyway.

I think that we'll probably leave it for a bit, get to know the boat and make changes to the ballast if neccessary. Once we're sure that everything is to our satisfaction, then we'll secure it permenantly (probably with concrete like Gonzo suggested).

[Jimbo1490]

There exists special curatives that will not exotherm no matter the thickness of the mass. Many bowling balls are cast from thermoset epoxy and they are pretty thick. You might inquire about such a curative from a manufacturer like Air Products And Chemicals. When I have made inquiries with them in the past they have been outstandingly helpful and generous with samples. They are a great company to deal with, and they have a $hitload of different epoxy curatives! They can tell you the ratio to use with your resin or show you how to calculate the ratio yourself.

Jimbo

[mel80]

Thanks Jimbo; I'll look into that. Air Products And Chemicals seem to have suppliers in the UK, so I'll give them a try.

[rturbett]

now I'm picturing bowling balls and concrete