I have a friend who is into sailing in a big way and to increase the stability of his boat want to change the keel to a different design, one with a larger area. He is very worried about the increased forces in the mast wires.
Does anyone know anything about this or could recommend a good source?

Cheers

Liam Mc

If it’s not a home made boat, I’d have assumed that the original designer had made the keel to suit the strength of the sail and mast. Tbh I’d rather have a keel snap than rigging explode. Real question is…can he sail properly?

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Originally posted by Mr Whippy
If it’s not a home made boat, I’d have assumed that the original designer had made the keel to suit the strength of the sail and mast. Tbh I’d rather have a keel snap than rigging explode. Real question is…can he sail properly?

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Originally posted by alistairolsen

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Originally posted by Mr Whippy
If it’s not a home made boat, I’d have assumed that the original designer had made the keel to suit the strength of the sail and mast. Tbh I’d rather have a keel snap than rigging explode. Real question is…can he sail properly?

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if it s a yacht as opposed to a dinghy then a keel failure will result in a dangerous and permanent inversion followed in general by sinking so i would far rather suffer a rigging failure.

Consider that most racing yachts are sailed with all of the crews weight adding to the effect of the keel and suffer no ill effects.

also depends on the age of the rigging, I would change it ever 5 years if racing, but a lot of boats are running 20 year old wire

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This sounds very complex. The design of hull, keel, and rigging is usually co dependant. By increasing the area of the keel, do you mean as in long keel (an alarmingly complex alteration) or deeper (which will have huge effects on the hull, rigging, mast load, etc) Getting a different boat souds the most logical route.

The sailing dingy I have snapped its keel due to the previous owner having too much sail up, the boat simply capsized and he made a new one. Considering the forces on the rigging wires and their usual fittings on the end of them, wires wiping around your face seems very dangerous. Personally I don't think he should change a thing and if he's out grown the capabilities of the boat, it probably now time to move onto a faster one.

on the flip side, if its a cruising yacht that he sails shorthanded with reduced sail and just wants a little more stability then adding to the keel is most likely fine.

Is this like one of those "I have a friend with an embarrassing problem" questions you see in the magazines and you know it's really the writer ? It's alright to admit you like boats Liam, no need to be covert. I will take this opportunity to admit that I quite fancy a go at kayaking.

lol, no its not my boat though I have seen it. I do like to go out in my kayak though

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Originally posted by Peteff
Is this like one of those "I have a friend with an embarrassing problem" questions you see in the magazines and you know it's really the writer ? It's alright to admit you like boats Liam, no need to be covert. I will take this opportunity to admit that I quite fancy a go at kayaking.

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so then what kind of boat is it?

don't say a sailing boat

I don't understand why he wants to increase the area if he wants to make the boat stiffer. To do that he wants to add ballast to increase the righting moment, not lateral keel area. that will, if anything will make the boat more tender as it will make less leeway.

This can be done easily by adding lead ballast inside the hull around the keel without adding stress loading on the keel bolts and floors. Alternatively cast or bolt lead bulbs to the keel

The rigging wire spec is dependant on the righting moment of the boat which is a factor of both form stability (shape of the hull) and the keel. As a general rule adding ballast of up to 30% of the keel weight is permissable without upgrading the rig spec as it would only add about 20% to the rig loading which would have been designed with a 100% safety factor.

It would be useful to know the type of boat as race boats are built with much lower safety factors.

Hi, I'm a bit of a lurker but this topic caught my attention - I know two people who were onboard a yacht which lost its keel and one guy died. The failure was due to a few factors, including poor design, added weight and the keel manufacturer changing the design (they put a weld at the point of highest bending moment to simplify manufacture) link. However, if it's simply a case of worrying about the rigging, wire rigging gauges are not exceptionally expensive and will give a good indication as to the tension in the wires.

[Edited on 22/9/09 by CurlyBen]

Look what happended to Tony Bullimor. He added weight at the bottom and reshaped his keel.

Look what happended to Tony Bullimor. He added weight at the bottom and reshaped his keel.

Both those examples were race boats which are notoriously designed on the limits or beyond in the name of performance.

It is highly dependant on the type of boat as to whether adding ballast is possible. Most GRP boats up to the '70's were massively overbuilt. Early knowledge of the properties GRP was very limited and the assumption was that if a 28ft boat needed 1" planking when built in timber, then it had to have 1" thick lay-up in GRP. So the were built like brick s**thouses (unfortunately they often sailed like one as well)

If your friend has one of those then he could hang whatever he liked on the bottom.

On the otherhand anything built in France by the volume builders (Beneteau, Jeanneau, Dufour etc.) up to the '90's are very fragile. They had some very odd ideas about how to stick the keel on and frequently they need strengthening just as they are.