Thanks, this is what I will do with a lead bulb at the bottom. I am thinking a keel depth of about 200mm (the hull is about 1000mm long) with 1100gm (measured requirement) lead ballast on the bottom will be a good starting point, any thoughts on this?
@Richardjm:
The longer the keel fin, the less weight you need on the end for the same righting moment.
Here is a real world example of a model boat I own that sails quite well in most weather including a blow - the Shunbo Monsoon is 900mm long, mine has a 1700 gram keel bulb. The keel fin measures 400mm from the waterline to the bottom of the keel bulb. Overall height of the boat is 1800mm from bottom of keel bulb to top of mast. Sail area (standard Bermuda rig) is about 0.4 square metres.
Pictures of this cheap Chinese boat at:
http://www.hobbyking.com/hobbyking/store/__8309__RC_1_8mtr_Monsoon_Sailboat_90pcnt_RTR.htmlI can tell you that the recommended 1300 grams keel weight on that website is NOT enough for this boat; it makes it very tender to sail in anything but very light weather.
Depending on your sail plan height and area, your proposed 1100 gram bulb on a 200mm fin may be a bit short and a bit light. The above figures may serve as a guide if nothing else
Keep in mind that as you lengthen the fin, the leverage increases and you finish up with a lot of stress between the hull and the fin. With the Monsoon, the keel fin extends right up through the boat to deck level to spread the loading.
Hope this helps...