Bellissima required ballast

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5 December 2016 at 18:47 #2634
David Wren 2
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@davidwren2
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5 December 2016 at 18:47 #68924
David Wren 2
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@davidwren2
I’ve just purchased an aero-naut Bellissima sailing yacht that has never sailed and has no ballast on the keel as is obviously required. I have discovered that the ballast is available as an optional extra but I fancy having a go at producing it myself from sheet lead as guided by posts elsewhere on the forum.

As a newcomer to model boats (although I’ve been making model aircraft for over 60 years) could someone tell me if my ideas below would get me to a starting point weight for the ballast?

Stated displacement from the instruction book = 4700g

Weight of model with all R/C gear fitted = 2600g

Required ballast = 4700-2600 = 2100g or around about 200ccm of lead.

I also assume that all of this mass is formed into a streamlined torpedo and fitted to the end of the keel and not split between the keel and the bottom of the yacht.
5 December 2016 at 20:33 #68926
Gareth Jones
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@garethjones79649
Hi David,

I looked through the instructions here **LINK** and could not find any reference to any ballast in the hull so it seems reasonable to assume it is all in the streamlined bulb fitted to the bottom of the keel.

It is not too difficult to make up the shape in two halves using lead flashing, laminated together with epoxy adhesive. At least using this method you can trim the pieces and weigh them as you progress to get the right weight. In the ones my wife has made they have been filled with Isopon and sanded to shape afterwards, but take precautions against getting contaminated with lead dust in the process. There are plans of ballast shapes/profiles available on the web and I think, from the My Hobby Store plans service (or maybe it is the other lot)

I am currently making a pattern for an A class yacht keel weight. We are planning to get that cast professionally. I don't fancy juggling a pan filled with 17 kg of molten lead.

Gareth
6 December 2016 at 09:24 #68930
ashley needham
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@ashleyneedham69188
17Kg of lead !!!! Wow (and not cheap) Ashley
6 December 2016 at 12:06 #68931
Kev.W
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@kev-w
With 17kg of lead, that will make it well up the heavy end of the class, modern boats only displace 13 – 14kg
6 December 2016 at 21:12 #68944
Gareth Jones
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@garethjones79649
Kip,

Serica II is definitely not a modern A class. It's a derivative of a Bill Daniels design from around 1956. We guess it will weigh around 60 lb (27-28 kg) when complete and it's 84 inches long.

One of the reasons it has begun to take priority over my Humber keel Spider J is that if we don't get on with it soon, we will be too old and decrepit to lift it in and out of the water.

Here's a photo as it is now, along with our hearing dog Sally for scale purposes.

Gareth
6 December 2016 at 21:50 #68945
Kev.W
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@kev-w
Wow !! that is some hull, beautiful lines, they sure don't make 'em like that any more

Hope you're going to post up some pic's of her in flight, once you get her on the wet stuff.
7 December 2016 at 07:03 #68947
Banjoman
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@banjoman
Gareth,

That looks not only like an impressively large model, but like an exceptionally beautiful one, too! Absolutely stunning! Any chance of a wee thread from you on her as well, including some more photos to admire?

Mattias
7 December 2016 at 08:55 #68951
ashley needham
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@ashleyneedham69188
I think a stretched out Lion would have been better for scale purposes.

Any ideas of a launching apparatus or are you all really strong and wornot?? Ashley
7 December 2016 at 09:55 #68953
Malcolm Frary
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@malcolmfrary95515
At risk of going back to the original question, 2.1Kg sounds very reasonable, and will all be in the bulb. Unless there is a really terrible trim problem, yachts never, ever, need internal ballast. It would be in the wrong place to do the job of applying righting moment against the efforts of the sails.

Laminating is the easy way to go with all of the proper precautions when handling lead. 2.1Kg is still a lot to use if casting, and making a mould, while not rocket science, is a bit involved, especially one the right size. The shape is fairly critical – I have seen a few blocks stuck on the end of a fin "to see if a bit more weight was better" which simply doesn't work.

The launching apparatus for the other boat mentioned is in the first "second boat" post. Use a crew. With a yacht that big, if there is a good sailing breeze, it is not just the weight of the yacht, its the drive from the sails while it is being handled on shore. Big heavy yachts with big sails will make a spirited attempt to have a single handler join them in the water. By comparison, a 5Kg yacht with good rigging can be launched and retrieved with one hand using the mast as a handle.
7 December 2016 at 11:25 #68956
David Wren 2
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@davidwren2
Gareth

Thanks for the link to the building instructions, they were for the Bella which is a scaled down version of my yacht but it told me that instructions are downloadable in English as the ones that came with the boat were in German.

I’ll take note of your safety warnings when handling lead. When I think back to my days in the 1950s melting lead in a cocoa tin held with a pair of pliers on my mother’s gas stove and then pouring it into a mould which hadn’t been heated to gas mark 7 I go into a bit of a sweat. Mind you only small (compared to 17kg anyway) quantities were used.

Malcolm

Thanks for confirming my calculation I'll go ahead with 2.1kg and use the lamination method. I've cast ballast weights for competition gliders in the past and didn't realise the risks I was running having read some of the precautionary posts – mind you I never needed to cast anywhere near 2kg of ballast.

I’ll search around and see if I can find a site giving typical coordinates for the bulb.
7 December 2016 at 19:52 #68965
Malcolm Frary
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@malcolmfrary95515
Back when I had cause to make a ballast weight I made it as two identical mirror halves, so about 1Kg each. The trick was to get the right volume. This involved immersing 1Kg of lead in water in a measuring jug, separating water and lead, replace lead with plasticine until the same marl was reached. Then make the plasticine the required shape and take the mould off that. But that was pre-internet. It worked with the flattened teardrop shape I was after, not sure just how well it would work with a torpedo shape.

Edited By Malcolm Frary on 07/12/2016 19:53:20
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