Hi just looking at a LM27 to buy and it has had 19 inches put on the length if the keel, has anyone seen this before and what were the benefits. Any help appreciated
I assume you mean that the draft of the boat has been increased by 19" (i.e from 36" to 55"), and this has been undertaken by a previous owner. That is a very significant increase that will have a marked effect on the stability of the boat and the structural forces acting on the hull. If this has not been undertaken with the benefit of expert knowledge and high standards of design and workmanship it could have an adverse and potentially very dangerous effect on the boat. Such modifications would also need to be reported to an insurer, otherwise one's insurance may be invalidated, and reporting it may make it more difficult to obtain insurance.
(As a point of comparison, the Scanyacht 290, a manufacturer's revised version of the LM27, was available in 37" shallow draft and 53" deep draft versions.)
Presumably this has been done in an attempt to improve the windward ability of the boat. Personally, I am all for minor modifications to make a boat better, but if I wanted a high windward performance boat I would buy one and not try to make the LM something it is not.
The keel is there to resist the sideways force of the sails. Increase the keel area, an especially depth, and if nothing else is changed the boat will likely heel excessively, increasing the chances of capsize. Such a keel will also put increased forces on the hull it was not designed to take, especially when sailing to windward. (I imagine an owner making such a modification would also increase the size of the sail rig, which raises other concerns and questions.)
To prevent the boat heeling excessively with a bigger/deeper keel one would normally need to increase the ballast in the boat. The amount and position of the increased ballast would need to be carefully calculated. There is not space inside the hull of an LM27 to add significant weight unless one removes the existing iron or steel ballast and replaces it with denser lead (as some or all of the Scanyacht 290 versions have) or, unlikely, depleted uranium. That means any added weight would be put in the keel. That will itself increase the structural forces acting on and in the hull (in addition to the sideways hydrodynamic pressure from increased area) , will result in additional flexing of the hull and could potentially lead to structural damage or failure.
Unless such an extreme modification was designed by a qualified and experienced yacht designer/naval architect, and the installation supervised/inspected by either that person or a qualified surveyor, and there was documentation to prove this to my and an insurer's satisfaction (and I think it highly unlikely that will be the case), I would recommend you walk away and look for another boat.
Perhaps I am being unnecessarily alarmist (I would say cautious), and would welcome others' views on this.
