Take a look at the picture below:

The point above the 56 is the center of effort. That's where all the force from the wind balances on the sail. Imagine pushing on the center of effort of a model Skerry with your finger. It will tilt away from you until the force of the water under the hull balances your push. it will move sideways until stopped by the resistance of the daggerboard. But it won't turn because center of effort is aligned with the boat's center of lateral resistance.

Now add a jib. The center of effort moves left. Everything else stays the same. Push with your finger and the boat will tilt away more since there's less hull buoyancy to resist at the point where the wind balances. It will also turn away from you because there's some leverage between the center of effort and the center of lateral resistance.

So if he wants a less stable boat with lee helm that won't sail as close to the wind, it's a very effective modification :-)

Boats and sail plans have to be designed together. In this case, if you want a jib, you'd have to balance it by making the main sail a different shape, moving the mast back or by adding a mizzen.

Good luck,

Laszlo

  Thanks for the info Lazlo. I am new here and have picked up some great ideas from your posts and really appreciate your help. My neighbor , Holden , watched   me sail my Dory beyond the horizon a couple of times and in short order he had a Skerry of his own , with a sprit rig, which I  think  can present challenges for beach launching when the  wind and waves require a steady and quick raising and lowering of sail , which is typical here in the lower Chesapeake.

My thinking is he should get the balanced lug and resist the urge to add anything and use the sprit sail for a change of pace  .  I am still learning , too and when he asked me about the small jib as an option and  showed me some examples of sprit /jib rigs on a skerry ,   I suggested  he  ask the designer  about the jib paired with a sprit on a skerry .I am sure  he will do that. In turn , I would post the question on the builders forum. Apparently some one has added a jib to a sprit rigged skerry which is pictured below. I am confident he will use the info he gets in response to his question and make a smart decision.

http://www.christinedemerchant.com/skerryjib.html

The Skerry and Dory are outstanding designs for beach launched rowing and sailing - No waiting at marinas or trailoring delays .They  are positioned on the beach and you just walk down to them and in minutes,  you are out there in the  big blue . There are so enjoyable that I think that is why one gets to thinking of tweaking them ........

There are now 3 of them launching from my beach and based on feedback, I expect to see more .

Dermot

Dermot,

I would love to see some video of your beach launchings.  We are planning some Skerry trips off of SC beaches and the launchings are the only parts that worry me.

Hooper Williams

Brevard, NC 

Hooper,

Don't worry. The Skerry gets beach launched dozens of times at Okoumefest every year  and I've never seen anyone have any trouble with it. Just set it all up, push off, jump in, grab the lines and tiller and when it's deep enough, put down the daggerboard. Oh yeah, make sure that the rudder is down. It took longer to type it than do it.

Dermot,

If you read her blog carefully,you'll see that Christine had changed the shape of the mainsail, which upset the balance between the centers of effort and lateral resistance. Basically, she moved the center of effort right. Adding the jib moved it back to the left where it belonged.

So she in effect made the jib work by changing the shape of the main sail, just in reverse.

Have fun,

Laszlo

 Thanks Laszlo,

My main concern is getting through the surf and learning to judge how much is too much and how to maneuver in differing current/wave and wind conditions without getting broadsided and rolled.  I've watched skiffs launch in some pretty dramatic surf enough to realize there must be knowledge and skill beyond normal boating to get through that afloat.  (maybe luck?)  The surf on the NC/SC/GA coastline can vary dramatically during the course of a day and from one day to another.  

Hooper 

 Hi Hopper ,

I will try and get some footage for you soon, if not video,  at least good still photos.

Beach launching in moderate ocean surf should be OK if there are decent intervals between waves. You have to launch and clear the waves without delay . If the  surf is stoked up that's another matter and if it were me I would avoid it .When it's rough here and I want to go out ,  I use a smaller 14 ' kayak instead.

Dermot 

Laszlo , 

Thanks for bringing the additional sail modification to my attention.

It makes sense and I will share that insight with Holden, the skerry skipper.

Dermot 

Hooper,

If you're launching through surf, I'd recommend doing so under oars and not putting up the sail (including daggerboard and rudder) until you're well clear of the surf.

Years ago, I had a 16-foot sprit-rigged Amesbury Skiff with daggerboard and rudder.  I never even stepped the mast until I was in open water.  The oars gave excellen control through the surf.  Even when much younger, I didn't have the nerve to negotiate surf with the clutter of sailing gear hanging in the breeze.

Regards,

Dick

 Thanks Dermot.and Dick.  This is the type of information I'm trying to gather.  I've seen 18 foot runabouts launch through 8-10 ft surf on the west coast of Mexico and I know rowing "surf boats" is a sport in New Zealand or somewhere.  I don't want to try to be extreme, but I would like to develop a skill for reasonable surf launching.  I look forward to seeing some photos or video from Dermot.  Maybe we should start a new thread, since we are pretty far off the subject of adding a jib.  

Hooper   

Everything that Lazlo pointed out  about center of effort and center of lateral resistance is absolutely correct.   

However, I replaced my spritsail with a lugsail. The mast is now aluminum and quite a bit thicker and more substantial.  Ergo, there's more windage, which is forward of the daggerboard.   There's a bit of rake to the mast and the whole thing is moved aft about 4 inches.   Then again, if I take a photograph of the boat  with the boom and yard centered and plot the geometrical center of the sails rectangle, it's still pretty darned close to right over the daggerboard.

 On a lark, I made a dumb, flattish jib from the leftover "test" polypropylene tarp that had been used for my test lugsail.  I set it up and went for a sail. It worked just fine and the boat did not turn off, downwind or need horrible corrective action with the tiller.

I also have observed that the tendency of the boat to round up, or not...or drift off....or not can be immensely affected by exactly where I put my 280 pounds of bulk.  As a general rule, I sit as close to the center thwart as I possible can. I bet dollars to doughnuts that where I sit has a hugely greater impact on the balance of the boat than the 12-14 square feet of jib that I do or do not put up.

Thus my conclusion is that  in fact the real answer tol your question  is, IMHO....try it and see what happens.