Gunning Dory Help Needed

[Todd Bradshaw]

A gentleman contacted me for input on increasing sail area on a gunning dory plan. You know me and that I generally don't second-guess designers without good reason, but in this case the rig on the plan (Leg-O-Mutton sloop with a total sail area of about 75 sq. ft. - very low aspect ratio - on a 400 lb. 18' boat) does seem pretty small. I told him that increasing sail area and aspect ratio is fairly simple and should be able to be done without screwing up the helm balance, but that I know very little about gunning dories or their sailing/stability characteristics.

The plan shown here has a proposed new rig (purple) superimposed over the original sailplan. Balance is estimated at this point and the amount of sail area to add was pulled out of the blue. Input would be appreciated from those with experience sailing this type of boat.
Thanks,
T.E.B.
http://www.imagestation.com/picture/sraid50/pa3c2e337086b8f4ad13cb996ef866449/fcaf1709.jpg

[ 02-04-2003, 06:02 PM: Message edited by: Todd Bradshaw ]

[Ben Fuller]

Todd,

That looks like a reasonable amount of increase. Make sure the customer has some shrouds or cut the jib with plenty of hollow on the luff. Mast bending forward really messes things up on these rigs. Also make sure that the customer can get weight to windward if the customer sails alone. With the flare in these hulls if you are in the middle of the boat to windward you have considerable sail carrying power. Most of the traditional dory rigs have more weather helm than we find acceptable now, and reducing it some would not hurt.

[Ian McColgin]

What you show comes close to how Leeward ended up, except I never got around yet to making the jib.

Which you'll want for righteous balance - I have to about hang my butt off the stern to turn down-wind.

I would make it possible to reef. I reef down to the original size for breezes over 15 kt if I'm going up wind to any degree.

The extra area is most needed for really light air. These boats have a low 'hull speed' and once you hit it, it's like a wall. Added sailpower does not increase the top end much. It does increase the fun a lot.

On Leeward I did not use a conventional boom - more like a horizontal sprit normal to the luff and out to the clew. Makes it hugely easier for the crew to survive tacking and makes the whole unit self-vanging.

Definatly get a window in the sail. On every point of sailing you cannot see squat to leeward except on calm days when you can lie down in the boat.

These boats are lovely but they do take some water. The addition of elvstrom type bailers a bit forward of the second from aft frame station is nice.

[Bill Perkins]

Here's a happy owner with some second hand sails he felt worked well enough .

http://www.imagestation.com/picture/sraid14/p06e77723e37ee603a4b470d902e45139/fde34e06.jpg

I have his email address if you'd like to hash it out with him .