Bulb building (update 1.03)

The bulbs themselves can be very different in the method of casting and assembly.

Emma

Gary’s instructions and procedure work very well, but you can modify how it is done any way you like.

However you do it, it should finish up with a total weight of keel and bulb of 3400g for the Emma sloop.. Gary assures us it will still sail well up to 200g either way, but recommends the 3400g.

We cast ours in two halves, each about 1480g. leaving a neat fit cavity for the keel foot to fit back in for final attachment.

Some work in progress photos.

This is a removable bulb version. Why remove it if it works? Well, if you were racing this boat against others and have a need for speed that cruising doesn’t demand, you could have 2 or 3 different weight bulbs to suit various sailing conditions. I doubt if I will bother but I’ve made it a workable option.

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Bob W ….   The blank for the bulb can be made from blue foam. To stop the plaster sticking to the foam coat with grease. I mistakenly used sellotape. The surface needs to be as smooth as possible. The blank also needs to be totally symmetrical along its length. Don’t ask how i found out! Remember foam will float on the plaster so you will need a couple of small batons to hold the foam down level with the surface of the poured plaster.

 

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Gary advises..  About the total weight of keel & bulb –
I do suggest the keel & bulb should weigh 3.4 kg (7-1/2 lbs)
However, this is assuming that the Boat has been built according to the plans and, without keel & bulb, weighs about 2.7 kg (6 lbs).
The really right thing to do is fashion the bulb so that the TOTAL weight if the finished boat, with keel & bulb, is 6.14 kg (13-1/2 lbs)
This will compensate for the weight of any variations in construction, such as added details or equipment, and will assure that she floats on her lines.
Lastly, allow yourself a bit of leeway. Emma will be happy if she comes out plus or minus 200 gr (.4 lbs)

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If you have any tips or ideas on bulb making please use the contact form to tell me about it.

However please do not include anything on the actual melting of lead.

 

Casting is not to be undertaken by anyone unsure of how to do it safely. Seek experienced assistance if need be.

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