Ballast Keels.

[Derek BradleyParticipant @derekbradley32270]

Some time ago I scratch built a (slightly modified) 1:8 scale version of the Sarik Hobbies bermudan sloop 'Ardent'. Apart from one or two little hiccups I was very pleased with the build but the trial sail was a disaster because I had built it with sheets of lead in the single keel. I had worked out the amount of lead by ballasting down to the waterline and then weighed the lead. Problem was that the ballast was not low enough to give a reasonable righting moment.. I have now stripped out the sheets of lead from the keel and intend moulding a new ballast keel from lead shot as the thought of messing about with molten lead leaves me somewhat worried. I have made a master copy (or as they say in the trade a 'pattern&#39 for the ballast. I am not happy with this as I made it out of balsa and am waiting for some obeche from Slec to make a better one. I am thinking of using a mix of very fine sand and plaster of paris to make the mould from the pattern or should I just use plaster of paris? The lead shot would then be poured into the mould along with a 2 part resin to seal it. This is a model of a cruising yacht so I am happy with the shape and depth of the fin keel and an extra inch of depth does not worry me.. A new ballast keel would be attached by fitting to the bottom of the fin and secured by bolts into nuts moulded into the fin. Any suggestions would be very helpful. Many thanks.

Derek.

[Derek BradleyParticipant @derekbradley32270]

Making a ballast keel using lead shot.

[Tim RoweParticipant @timrowe83142]

Hello Derek

When you make your new pattern it is important that you seal and wax it well. The sealing is to stop water from the plaster of Paris making the wood swell. This could split your mould or make the pattern difficult to get out, The wax will help the pattern to release.

Don't forget to taper the side of the pattern otherwise it will get locked into the mould. You would have to dig it out! The lead would also be locked into the mould which would have to be broken to get it out. That wouldn't matter so much if you only want to make one.

I would probably pre-mix the shot and resin to make sure every thing stuck together. If you pour it in afterwards it might not get everywhere and the shot would fall out.

Good luck

Tim R

[Derek BradleyParticipant @derekbradley32270]

Many thanks for your tips Tim, especially the waxing of the pattern. I was thinking of painting the pattern in order to seal it but, I suppose that, the addition of the wax will help to both seal and free it.

Derek.

[Derek BradleyParticipant @derekbradley32270]

I think that the only other query is – IF I was to use a mixture of fine sand and plaster of paris what should the mix ratio be?

Derek.

[Ray Wood 3Participant @raywood3]

Hi Derek,

I can't see any reason to add sand to the plaster of Paris as I commented on Mayhem? Sand is used as a mould from a pattern in a foundry for casting iron which is normally machined to get a finish. Plaster of Paris will be ultra smooth if your plug is good. The only issue is the resin & lead shot is normally used to fill a plastic or grp shell to weight a keel, trying to form what your pattern looks like is a winged keel and will be a devil to release from what ever mould you use as Tim R advised. The other consideration is drilling your holes through resin & lead is a bit of a bug$er !!

I have been thinking this issue through for a project I have in mind, I think there is scope for producing the shape with balsa sheet and using that to contain the lead & resin and then using resin & cloth outside the keel, you are not the only person who doesn't like the idea of cast lead keels, but I find it quite fun

Regards Ray

[Derek BradleyParticipant @derekbradley32270]

Many thanks Ray. I will take your advice and use only plaster of paris. I will take time over making a new plug. I intend placing the plug in a box of the appropriate size with the bottom of the plug and wings flat onto a releaseable surface and then pour the p of p in so that it comes well over the top of the plug so that when it has cured the plug can be eased out using a couple of woodscrews screwed into the bottom. Fingers crossed..

Derek.

[Chris FellowsParticipant @chrisfellows72943]

That's a coincidence! I was reading through some of my threads earlier to find out some information and having come across some of your comments I wondered how you were doing?

Did you finish your Huntress?

Just to add to Ray's comment about drilling through lead and resin, can you incorporate some sleeves?

And hello Tim, long time no hear from you.

Chris

Edited By Chris Fellows on 26/03/2023 22:37:11

[Derek BradleyParticipant @derekbradley32270]

Hi Chris,

Thanks for the tip about using sleeves – must be worth a try. I have been following your progress on the other website. Sorry to say that I gave up on the Huntress as, no matter how I tried, I could not get the hull strakes right and I sold it along with all my other boats. I will be 90 years old later this year (and 39 years since I had a heart op) so, at times, I feel as if the dreaded day is approaching and, unfortunately, tend to get rid of some of my assets. I even sold on the yacht that is the subject of this blog but the person who bought it was good enough to sell it back to me. It was my first ever scratch build and I was so pleased with the appearance and my build of it and I knew that he had done nothing with it. I knew what problems it had and am in the process of trying to solve them now. Whether I ever get to sail it remains to be seen but, at least, it takes my mind off other things.

Derek.

[Chris FellowsParticipant @chrisfellows72943]

I don't tend to post much about my builds on other sites, just snippets really. Some might say I don't post much on here either given my slow progress!

Sorry to hear about the Huntress, the strakes can be a pig. Pity about the other boats as well but I understand where you are coming from. Good that you got Ardent back though.

Chris

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