Advice required on lead shot & resin as internal ballast

[fj19]

Has anyone experience of casting internal ballast using lead shot & polyester resin mix? I am currently fitting out a grp hull with bilge keels and plan to fill the bilge keel mouldings with this ballast. I would appreciate advice on this matter.

 

[geoffatstanpit]

Lead would be nearly half as good again as the usual steel punchings. But it would be expensive. Last time I bought scrap lead was for making diving weights in 1960 and it was a shilling a pound then. Probably more now!

 

[pandos]

I do not have any experiance but would have thought that you would be better off melting the lead and casting it into one solid block and then glassing this into the keel.

I am not sure how you stop the molten lead affecting the grp but there must be some method as many boats are done this way.

My friends keel is filled with iron punchings mixed with resin and poured in. Cheap but nowhere as dense /effective as lead. It Has started to rust and has needed a few temporary repairs.

 

[graham]

Large quantities of polyester resin can generate a lot of heat as it cures.I havent done any lead shot moulding but be very carefull ,try a small quantity first.

Would it be easier to cast in some larger lumps of lead and use the lead shot to fill in the gaps?

 

[jwilson]

The 'quality' way to do this is to make a single lead casting that will fill the required keel base just undersized, and then lower this into a bed of resin/wetted out mat with accelerator/catalyst amounts adjusted to give very slow setting (to avoid heat gereaation during cure). Then glass over the lot. Obviously the lead casting is made outside the keels first - the GRP would probably catch fire if molten lead poured in!

This gets the weight concentrated as far down as possible - always a benefit. Maximum lead - minimum resin.

You can however get a fairly good result by casting medium-sixed bars/ingots from scrap lead, and laying them in with resin. You can pour in lead shot to fill gaps. Much easier to manage as a DIY job, but you must make sure the resin is slow-setting, or you will get overheating as the resin cures. Not quite as good as the single casting method, but much better than iron punchings set in resin, which is what many people use for cheapness..

 

[kenhick]

I can only tell you the way I did it not sure if it’s the right way work ok for me.
Linen the inside of the keel with bin liners then filled the keel with foam, when set remove and slice up to manageable size, use these to build concrete moulds in fast dry cement make sure it’s gone off, NB, melt lead pour in, finish off with lead shot mix in slow resin and filler to slow it down even more, best of luck 3ton in my keel hard work

 

[oldsaltoz]

G'day fj19 and welcome to the YBW forums.

Lead shot is normally used to fill only the voids left around ingots and scraps. The use of lead shot only would almost double the cost of your ballast.

The last time we did this we used Epoxy resin thinned with Methylated spirits, adding 40% meths by weight after mixing the hardener in the normal ratio. As the voids between lead shot are very small heating is not normally a problem.

Don't forget to fully glass in the top section.

Avagoodweekend......

 

[boatmike]

Several methods. You can use scrap lead chunks or lead shot dumped directly into your keel and set with resin.
Advantage: easy to do.
Disadvantages: You can only do a bit at a time to stop the resin overheating, you get a low density result and its expensive in both lead shot/scrap and resin.
You can also use the same method but use a lead /cement mix which will give you as good a result if you glass over the top afterwards and be slightly heavier than shot+resin.
You can't pour molten lead directly into a GRP keel for obvious reasons!
You can make a mould of the internal shape of the keel. If you can get inside, and still have direct access from the top (i.e. no deck on yet) its pretty easy to make one out of foam as somebody else said, but make sure (as he said too) that you use loads of release agent or line the keel out with builders polythene. An alternative I have used is to use 1/8" thick rubber sheet stuck to the hull which when removed gives you clearance to resin bond the casting in afterwards. If you make up a wooden frame with lifting points on it and lower this in before you foam out you will not use as much foam and have something that you can erect a scaffold over to lift with a block and tackle when set to get a straight lift. (you will need this later to lift the lead in anyway) Use this to make a concrete mould from as the other post suggested,and pour your lead a bit at a time to fill the mould. You will of course need to follow H&S rules pouring lead. Wear a mask and don't breathe the fumes. You will need a substantial heat source and proper pouring ladles etc. Take advice from experts on this. Alternatively (and better) get professionals to come to you and cast on site, or take the mould to them. Don't forget to cast in lifting points!
It sounds more hassle this way but the resulting job is loads better.
Most yards that built boats this way always farmed the job out to specialist lead casters. There aren't many left as most now have bolt on keels.
It will be necessary whatever you do to calculate the weight you need. The finished lead casting will be 40% to 60% heavier than shot plus resin.
Never saw the advantage of shot+resin over shot+concrete if your keel is deep enough to get enough weight that way but don't substitute this for a designed weight in lead alone. The result won't be heavy enough and the boat will be tender.. Consult the boat's designer if you can. (what is it by the way?) If as you say it is a bilge keeler designed for home completion it may have been designed for the method you are intending. If so I would still consider concrete/lead mixed up beforehand in a cement mixer and just poured in cold. Leave for at least a month to dry before glassing over the top though. Get on with other jobs and come back to it later!
Hope this gives food for thought...

 

[jleaworthy]

I seem to remember that the builders of the Sea Wych gave comprehensive instructions on how to carry this out. Perhaps the representative of the Sea Wych Owners Association who regularly contributes here could help?

 

[Talulah]

Re: Advice required on lead shot & resin as internal ballast

Much younger when my father and I built our Roberts 34 we melted scrap led into a small saucepan. We made loads of small ingots this way. We lined the inside of the keel with lead sheet the same height as the ingots. The ingots were put in place and molten lead poured in to fill up the gaps. At times the outside of the keel felt incredibly hot. The depth of the keel was filled over a number of months depending upon how much scrap lead we had collected. There was no damage to the keel from the heat.