Ballast pattern - bulb - for deep draught classes

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Ballast pattern - bulb - for deep draught classes.


Printed ballast pattern. Choose from several geometries to suit you own application. If the standard designs do not suit please contact us directly with your custom requirements.

Product code. BALLAST PATTERN - BULB

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Ballast pattern - bulb - for deep draught classes

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Ballast pattern - bulb - for deep draught classes.

Printed ballast pattern. Choose from several geometries to suit you own application. If the standard designs do not suit please contact us directly with your custom requirements.

If you cannot source a good ballast locally, having one cast at a local foundry from a pattern may be the solution. There are two basic types.

Conventional bulb

Suitable for 65, 36R, IOM, M, 10R and other similar deep draught classes. Choose from length/diameter ratios of 9.5 or 8, from breadth/depth ratios of 1 and 1.2, and a variety of standard target weights. The pattern can be supplied in port and starboard halves or fore and aft halves depending on how you or your foundry intends to make the mould. Supplied in either 2 or 4 parts. The aft end of the pattern is cylindrical which allows the cooling molten metal to flow freely into that section of the mould cavity. It also helps protect the fragile end of the ballast until it is finally shaped to a point. 

Length/diameter ratio

The 9.5:1 ratio length/diameter pattern should be used with lead that is alloyed with 4% of Antimony (Sb) which will give the long/thin casting enough stiffness and strength. The volume of each pattern is adjusted to giive the target weight when using 4% Sb.

The 8:1 ratio length/diameter pattern should be used where pure lead is used so that the resulting casting is less subject to being bent. The volume of each pattern is adjusted to giive the target weight when using 0% Sb.

Breadth/depth ratio

Where the draught of the boat is less than the maximum permitted and/or where drag reduction is the major factor, then the round section ballast will give best performance. Where stability is the major factor and the draught is at the maximum permitted by the class rules then the 1.2:1 ratio breadth/depth ratio will give higher stability at a slight increase in drag.

Fine tuning the casting weight

The target weight of castings made from the port/starboard split patterns can be adjusted up by adding a spacer of suitable thickness on the centreline.

Winged planform pattern - for shallow draught classes

Please see SAILSetc product BALLAST PATTERN - WING. Suitable for 36R, 6M and A Class and similar shallow draught classes. To the same design used for some years on the prototype A Class SWORD and more recently on 6 Metres. The length/breadth and breadth/depth ratio is fixed. Choose from several target weights. Supplied in fore and aft parts up to a target weight of 10 kgs. Above that target weight there will be three parts.

The parts of the pattern are either provided with jigsaw puzzle type connections or dowel holes and dowels.

 

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