Giddaye from the land of OZ.
As I’m new to this forum thingy, have I listed my enquiry at the wrong venue, (technology discussions).
I am looking forward to hearing anyones opinion on raked keels in the IOM class. They used to be popular 15 years ago, around the time the class was established. It would appear from what little I can find on the internet that forward raked keels, (especially in dingy classes) seems to improve windward performance and reduce weather helm. I know IOM’s can easily be setup with no weather helm, but I’m wondering if there is any performance gains to be had, as the hull designs seem to have become fairly standard, as has performance overall.
Looking for any input as I have a very narrow IOM hull laid up ready for keel building.
Most focus seems to be on setting the fin and bulb up to reduce twisting from what I have seen lately from most designers in this class.
Understandable since the fins are now 1/2 the thickness they were 15 years ago.
worth taking a look at though…
Thanks for your comments Brett
You’re absolutely correct. The fin being attached to the front of the bulb will twist the fin to some degree. Being an ex kiwi, there was some thinking there a few years ago about fin twist allowing the boat to gain windward ground. I wonder if this would work? Of course to obtain twist the bulb would need to well back on the fin. I can remember there was a resolution on the table that fins be a minimum of 10 mm thickness.
I’ve had a very informative contact with Chris Cochran of Morrelli & Melvin. The main reason why forward sloping keels are no longer in fashion is due to their stalling out at low speed compared to conventional straight keels. Interesting that there is currently a 38 foot keel boat on “IONIC YACHTS” web site with a forward sloping keel. Maybe they don’t know what Chris does? IOM’s in the early 1090’s were designed with forward sloping keels, however they fell from favour very quickly. Maybe due to what Chris Cochran of Morrelli & Melvin tells me. There is a real interesting site on the web for those of you who are interested in big boats;
http://www.sailinganarchy.com/ Interestingly the editor of this site sails an IOM.