Keel Replacement

[kevinmal]

Hi everybody,
I sail a 30' half tonner one off which I bought last year. After sailing her for one season I found her to be very tender in heavy conditions and pretty hairy running downwind with a spinaker up in anything over 15 knots. At the moment I am thinking of changing the keel for one with a bulb . The existing keel weighs approx 1 ton .
I have a design of a keel for a Mount Gay 30 which is a steel structure filled with lead ,and seems to have an enormous bulb on the end. What I would like to know is the following
1. How to calculate the size of the bulb needed
2. How to locate the position of the new keel
3. Will I need to beef up the internal structure to take the extra loads.
I would appricate any help I can get with this.
Thanks Kevin.

[BOATMIK]

If you Google for the ABS code for Yacht Construction you will have a lot of the info you need for the internal structure.

Remember too that if you increase the stability of the boat it will be putting a lot more load on the rig.

Because stability was penalised under the IOR rule putting a Mount Gay Keel on might well double stability - which will double the load on the rig.

So I would definitely suggest running some calcs on this too.

If you are not too sure about what to do, perhaps it is wise to consider paying someone to work it all out for you. Much cheaper than doing all the mods and finding out that you got something wrong along the way.

On the other hand you can learn a lot doing it by yourself - but in that case you have to accept mistakes as part of the learning curve.

Best Regards
Michael Storer

[Windvang]

Originally Posted by kevinmal

Hi everybody,
I sail a 30' half tonner one off which I bought last year. After sailing her for one season I found her to be very tender in heavy conditions and pretty hairy running downwind with a spinaker up in anything over 15 knots. At the moment I am thinking of changing the keel for one with a bulb . The existing keel weighs approx 1 ton .
I have a design of a keel for a Mount Gay 30 which is a steel structure filled with lead ,and seems to have an enormous bulb on the end. What I would like to know is the following
1. How to calculate the size of the bulb needed
2. How to locate the position of the new keel
3. Will I need to beef up the internal structure to take the extra loads.
I would appricate any help I can get with this.
Thanks Kevin.

A lot of Half Tonners in Begium have done that. Try the forum at http://www.halftonclass-europe.net/ and you will get most of the answers.