Balanced Lug sail for skerry

I've already built my Skerry and would like to covert to a Lug sail. John Harris mentioned that the mast had to be moved towards the stern 6 inches. Any ideas as to how this may be accomblished without  changing the original mast step?  I also have another question. How are the new yards attached to the mast? Does anyone have some pictures? Mike

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RE: Balanced Lug sail for skerry

Re moving the mast step (or do you mean the mast collar - the upper hole in the forward deck you pass the mast through before 'stepping' it in the step - the piece on the floor), the easiest way is probably just epoxying in a new one a few inches aft of the current one.

If you meant the collar, one way to do it would be to make a removable thwart that clamps on the gunwales. That's common on sailing canoes, so they can convert back and forth from sail to paddle.

Re gigging a balance lug, here's a comprehensive page:

But personally, in terms of the upper parrel and halyard arrangment, I think the following is a much better solution, by Michel Storer (look for the part called "The Mainsail Halyard", where one rope, the halyard, holds the sail up, and holds it against the mast:

 I hope that helps.



RE: Balanced Lug sail for skerry

Oops, I meant mast partner, not collar. The partner is the top mounting hole itself, the collar is what is (on a yacht say) is used to seal the gap between the mast and the partner, to stop water entering the cabin (typically a rubber gasket/boot-thingie).

Damn, and I was feeling so salty there for a while! ;)


RE: Balanced Lug sail for skerry

Thanks David. The info and site was just what I needed.  Mike

RE: Balanced Lug sail for skerry

I also had heard that the mast had to be stepped 6" further aft when using the balanced lug rig.  I had some correspondence with John and he has determined that the balanced lug will work fine in the plan location. Perhaps he can chime in on this.


RE: Balanced Lug sail for skerry

Im thinking about the balanced Lug for my Skerry also.

It currently has the standard rig with sprit sail.

would this same sail work on a balanced lug rig?

and can I leave the mast stepped in its same location?

RE: Balanced Lug sail for skerry

>>>>I've already built my Skerry and would like to covert to a Lug sail. John Harris mentioned that the mast had to be moved towards the stern 6 inches.>>>

I've never said THAT!  That would be a structural mess even if it were necessary.  

I dug around and found some recent correspondence with a builder, with illustrations, helpful to the conversation about Skerry lug rigs.  Pasted below:

The traditional calculation for proper balance states that the sailplan's center of effort should be placed 10% of the waterline length forward of the quarter-chord point on the center of lateral resistance, if the boat has a well-defined fin like the Skerry.  Forward of 10% equals more lee helm;  less than 10% equals more weatherhelm.

Skerry Lug sail
This calc is oversimplified, as good sail balance includes many factors, especially hull shape, length of boom, sheet leads, the "draft" of the sail, and so on.  But it does give you a starting point.  This is the original drawing where I puzzled over the Skerry's balance with a lug rig set on the stock mast.  According to the official calculation, this boat should have weather helm, because the CE doesn't have any "lead" over the CLR.  It doesn't, though, because the Skerry is double-ended and narrow-sterned hulls don't "gripe" much when heeled, and because the tug of the sheet is from the middle of the boom.  (Imagine a sharply heeled boat, follow the vector of a sheet led from the aft end of the boom, and you can visualize the mainsheet pulling the stern to leeward.)
Skerry Lug sail
At some point someone asked about inducing a bit more weather-helm in the very neutral lug-rigged Skerry, so I did the calc with the boom peaked up a bit, moving the CE aft.  As far as I know this works fine.  You can get away with murder in boats with narrow, fine-ended waterplanes.

How you handle a cat-rigged boat that weighs 100lbs will have a huge effect on issues of balance.  Not enough outhaul will create a baggy sail that will scramble the delicate balance of vectors that determines sail balance, for example.  Another really common mistake is to sheet in hard in tacking when the boat has little or no way on.  With no water flowing over the daggerboard and rudder, they generate no lift, stall, and the forward-mounted rig will just blow the bow off ("lee helm") no matter what you do.  Sheet in gently after you tack to start the boat moving and generating lift over the foils.  If you're having trouble, bear off a little until you've gathered enough way for the daggerboard to start lifting, then come back up onto the wind.  Use a light touch on the tiller, as big rudder movements will slow the boat and exacerbate a stalling problem.  Especially in light air, a poorly shaped daggerboard can contribute to the trouble, by stalling more easily.

RE: Balanced Lug sail for skerry

Thanks John for the excelant reply.

Im a little rusty on my nautical design nomenclature.

So Would you dumb it down for me a bit and tell me which of the above pictures will sail good.


ALso Is the sail I have ok to use as a balanced lug?  

Mine looks like the sail in the picture but I dont have exact measuremnts.

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