When changing a sloop into a cutter

[Izos]

meaning, adding a staysail, should the main sail be redesigned to feet the new sails configuration?

[Jeff_H]

It depends on why and how you add a staysail. On most sloops the foretriangle is to small to effectively use the staysail for normal sailing. By any traditional definition of a cutter, cutters have proportionately larger foretriangles. (By the traditional definition of a cutter and sloop you are actually creating a sloop with multiple headsails and not a cutter, but that's another story.)

When you add a staysail in the foretriangle meant for use in moderate or less conditions, both your main and jib, need to be recut. The mainsail needs to be cut very flat down low as it will be backwinded by the forestaysail and the forestaysail needs to be cut flat with a moderately open leech so it won't backwind the mainsail or be backwinded by the headstaysail (jib).

If you are adding the staysail for heavyweather then the staysail needs to be cut flat and you need to carefully design the reefs so the boat will remain balanced sailing under just the reefed mainsail and staysail. That typically is such a deep reef on a sloop, that it is only useful in extremely heavy winds, and in that case you are better sailing under a strorm trisail because a conventional mainsail made out of heavy enough sailcloth and flat enough for those heavy conditions would be useless in normal conditions.

Jeff

[chris_gee]

Adding a staysail will not make it a cutter as such. Such a rig is generally called a double headsail sloop or slutter.
The difference is that the cutter is designed to have both headsails flying at once, whereas the slutter would usually have just the one. However it is possible to have two but this depends on the overall design, and performance may suffer.
There is at least one other thread on this but there are some misconceptions so it might help if I try to explain my conception of what is happening.
What is required for boat balance is that for simplicity there be equal sail area fore and aft of the centre of lateral resistance the point of balance of a boat. This assumes both sails are trimmed correctly eg luffing the main effects the force aft.
Similarly one boat may have a large headsail and smaller main or vv.
In the former case the mast is set further back.
Simply adding an extra sail does not increase power because the windforce is a function of the mass and speed of the air diverted.
That means that the same mass of air goes through the foretriangle whether it passes over 1 sail or two.
However two factors come into it.
Forward drive is mainly produced in the luff area, rather than the flat area, so in theory two luff lengths should give greater forward drive. In other words the air diverted remains the same so the force is the same but the resultant forward component of the force differs.
The catch is (although this gets complicated) that the force comes from laminar flow.
The extent of this depends on having the right slot size.
If it is too narrow as you would have seen you backwind the main or the inner sail, which cuts out the drive in the part that produces the forward force.
On a sloop that slot size is designed in.
On a cutter a bowsprit is required to give the extra separation for a second slot.
On a slutter you don't have that capacity without moving the mast back chainplates and all.
The other issue is to use 2 foresails at once you need to maintain the slot along the whole luff length so the luffs are parallel.
To do this means that the staysail is lower on the mast which will usually require running backstays to strengthen the mast at that point.
The alternative is to use a solent rig or or an inner forestay which which is set back only a couple of feet and terminates at much the same point as the outer forestay and may be detachable to allow for easy tacking without the furling the genoa to stop it hooking up.
In this case only one headsail is used at a time except perhaps downwind.
This has an advantage of better sail set using a dedicated sail on the inner stay rather than partly furling a genoa, where in effect you furl the part with the draft built in, in stronger wind conditions.
However you still have to balance the sail plan against the reefed main.
So in answer to your specific question you seem to assume greater sail area forward, (if in fact it is greater rather than just distributed between two sails for ease of sail handling) may need to be balanced by greater sail area aft.
This might be done by using full battens to get a bigger roach, however first you have to establish form whatever configuration you set up if in fact you have greater force rather than less, and secondly what the sail balance was like previously and after the other changes. For instance you may have had weather helm and increased it.
On the other hand if you added a bowsprit you may have eliminated it.
So you see it is not as simple as interposing a staysail.

[johnshasteen]

I agree. I've had two cutters and two sloops over the last 40 years and a sloop is designed from the keel up to be a sloop and a cutter to be a cutter. If you look as a real cutter, the mast is set much farther back on the boat - it generally comes down through the middle of the cabin and most cutters also have bow sprits, which gives it the ability to effectively carry both a headsail and a staysail and the boat remains balanced. Adding a second head sail to a sloop doesn't make it a cutter and won't do a lot for performance. Some sloops have added a removable inner headstay to use in heavy weather - drop the headsail, raise the inner headsail.

[bubb2]

nothing I can add to the above but the comments are right on the money!

[Izos]

thank you very much for your responses.
learned alot by reading them.
obviously have much more to learn on the matter.

[slutter]

Izos don’t let the old farts put you off; the world is not flat go find
out for your self and it only money not that you can take it to the
grave with you.
I made a slutter of my Cal24/3 and it is the best thing I have done.
To be able to choose how much sail you put up will teach you to be a
better sailor. Who knows you might find sailing in 30Knots+ fun.
Options with sq ft of sail for and aft is what you want.
Good sailing to you.
Slutter.

[SimonV]

I own an ericson 39b which has had a staysail added with running backs the staysail lines up with my main when it is on the third reef and makes a very balanced rig in heavy weather. When not in use the stay is moved to the side of the rigging allowing trouble free tacking.

[stevemac00]

This might be interesting for you. Dave converted his sloop to a cutter. I doubt you'd have to modify your main sail but a sailmaker can suggest if a re-cut is necessary.
Outfitting4List

You didn't say why. I think the main benefit is you can sail with heavier winds with a more balanced configuration. This means your main is likely in first or second reef. Another advantage may be more sail area with light winds but an asym headsail would be a cheaper alternative if that's your reason.

My boat can be rigged for either but I have a sloop. The cutter rig is more complicated. Many people make they're staysail rigging removable so they can sail as a sloop. But you have to also have to add running backstays at the increased mast loads at the staysail mast tang. Also you need new staysail tracks and two more winches for those leads.

So unless you sail where the wind is usually +30k or are going on long passages I'd look for other projects.

[rotrax]

Hi-I have read the thread and cant help wondering about the Island Packet rig with the self tacking staysail and overlapping genoa.Our I.P.350 sails pretty good for a heavy boat and the staysail is used more often than not.We have only had 30 knot winds gusting 36 so far.We rolled in about a third of the genoa and took in the first reef.She balanced well on a reach and had a steady motion.Our mentor(we are fairly new sailors) had not had any experience of an I.P. rig but was very experienced with cutters.He quite liked it.Any comments?