conversions:sloop to cutter rigged

Is it feasible to convert a sloop rig to a cutter or even a Yawl to single mast cutter
without unbalancing the boat? And this without moving the mast forward or back.

 

It is done, and has been done since long ago. I've done it with success.
The cutter generally puts the mast further back (unless starting with a hard-mouthed sloop, which may allow keeping the mast as is by adding a bowsprit).
Also, adding a mizzen can balance an added bowsprit.
Sail size matters too. Modern large fortriangles are so big (especially as developed from 70s IOR rules) that the majority of the sail plan is forward of the mast. In such cases it's quite easy to braek down the headsail into two smaller sails of the same size. I've found the cutter rig reaches faster and is slightly less weatherly, but altogether more handy than the sloop rig. More of a cruising set-up. All without moving the mast.

 

We could go on, but Alan has said it all really.

 

Some folks are willing to take a few of the advantages of the cutter with out the expense of balancing the boat with a bow sprit.

A second headstay that tacks to the forestay attachment point and attaches 3/4 of the way up the mast is fine for EZ inshore cruising.

Usually called a Slutter rig.

A lever style tack is used for the second stay.

The genoa or #1 sail works as it usually does , but when the wind pipes up the inner stay is set and the smaller sail hoisted.
The foresail is then dropped and secured in a zipper bag , not being removed from the forestay.

Not great offshore as the mast can bow at the second stay attacment point,but great for day sails in variable winds.

FF

 

True regarding mast bend if a masthead rig (with backstay). But if a gaffer, which requires backswept shrouds, any point above the gaff can be stayed and shrouded easily. This also applies to boats with fractional rigs.
Offshore, the inner headsail could be braced with a runner or permanent backswept shrouds, or something positioned like a shroud but removable (using a lever like the foredeck one) to allow the mainsail to be set at right angles to the boat. Then the rig would be fine for heavy offshore work.
And sometimes the mast is stiff enough to withstand the strain if the stays'l isn't too large. This was the case with a boat I converted. The inner sail attached to the mast at about 7/8 height and the mast was pretty heavy for the boat to begin with. The outer (bowsprit mounted) headsail was on a spectra line to a winch on the mast, and was set up to roller furl (not reef). When that was rolled up, I'd drop it to the deck, where it lay in a tight roll all the way back to the cockpit. No zippered bag required. It was just tied down onto the deck,

 

" No zippered bag required. It was just tied down onto the deck,"

The zippered bag is not to control the sail , but for it to LIVE in.

No UV damage, no hanking and unhanking , no wet sails below deck.

FF

 

Apples and oranges, Fred. The bag is for hanked-on sails, and the UV strip for roller-furled sails. Thanks for pointing that out.

 

Did it for my boat for offshore but installed running backs with a 6 fold purchase to towrail. When going to weather and reaching a bit I found that I could leave the wheel alone for much longer with the cutter rig. But it did need the running backs and especially with a reefed main which takes away mast support. Both headsails were rigged with Profurls of two sizes.