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Modified sloop to cutter rig

Giro

.
Jul 23, 2019
62
MacGregor MacGregor 25 Monterey
I have been observing photos of Macgregor 25s which appear to have been converted to cutter rigs. It looks as though blocks have been added to the masthead and halyards have been installed forward of the roller furling units which have also been installed. Wouldn’t this type of modification require a major reconfiguration of mast placement in addition to the installation of a reinforced bowsprit attachment?
 
Oct 24, 2010
2,390
Hunter 30 Everett, WA
I'd suggest posting this on Macgreggorowners.com. Sorry, I can't help.

Ken
 
Oct 22, 2014
15,791
CAL 35 Cruiser moored EVERETT WA
The Cutter rigging should go inside of the sloop rigged forestay. The Cutter Stay should also attach to the mast somewhere below the jib stay. This works well for a Mast Head rig. The Cutter sail gives the Mast Head rigged Sloop the opportunity to put a smaller sail ahead of the mast in building winds. It helps to balance the sail plan.

The MacGregor 25 is not a mast head sloop. It is a fractional rig with the forestay connecting to the mast in the upper 1/3rd of the mast height.
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Not sure it would provide much benefit.

What you appear to be discussing is adding a Spinnaker or Head sail in out beyond the Forestay. This would enhance your downwind sailing speed and complicate the sail handling.

Often an asymmetrical spinnaker is chosen. It is a compromise. A little easier to raise and lower, but not as effective going directly downwind as a symmetrical spinnaker.
 
Jan 11, 2014
7,718
Sabre 362 113 Fair Haven, NY
A 25 foot boat is a little small to convert to a cutter rig. The sail area on the staysail will be quite small, especially if the boat is a fractional rig.

Larger boats often add an inner forestay for offshore work with a staysail or a storm jib. To do it properly the attachment point on the deck needs to be reinforced and tied to the hull or to a bulkhead to distribute the loads. Some boats will required the addition of running backstays to balance the forces on the mast from the stay sail.

Cutter rigs are only efficient when reaching. Off the wind the mainsail blocks the staysail and on the wind the it interferes with air flow in the slot between the jib and mainsail.

For downwind sailing, some boats will add a second forestay just behind or along side the existing forestay. This arrangement allows for flying 2 poled out jibs. Great for sailing down wind in the tropics. These are not really cutter rigs. Alternatively many roller furlers have 2 tracks in the foil. A sail can be hoisted in each track and poled out to get the same effect.
 
Oct 19, 2017
6,876
O'Day 19 Littleton, NH
It looks like, too convert the M25 to a cutter, you would want to move the base of the existing headsail aft by a foot or so, to become the staysail, add a short bowsprit and run the new yankee to the masthead. Reinforce appropriately. No need to move the mast, but this would change the CE forward when flying the yankee.
I'd also be inclined to add a small stub keel forward of the cb, unless I felt she already suffered from bad weather helm. The added sail area might require the new keel extension be weighted to keep her from becoming overly tender.

-Will (Dragonfly)
 

Giro

.
Jul 23, 2019
62
MacGregor MacGregor 25 Monterey
I want to thank those of you who responded to my inquiry regarding the transformation of those sloops into “wannabe cutter rigs.” Your investment of time explaining your points of view are insightful and display deep knowledge of marine mechanics and/or engineering. However, to be clear, I have no intention of attempting to change my simple 25 foot sloop into anything other than what she was created to be. I can truthfully say that my curiosity has be duly satisfied. Thanks, again.
 
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Likes: LloydB
Jan 11, 2014
7,718
Sabre 362 113 Fair Haven, NY
However, to be clear, I have no intention of attempting to change my simple 25 foot sloop into anything other than what she was created to be. I can truthfully say that my curiosity has be duly satisfied. Thanks, again.

Good choice. If you really interested in rig designs and more importantly the how to design them, take a look at Brion Toss's The Complete Rigger's Apprentice. Fair warning, it could be more information than you wanted. :cool:
 
Jan 21, 2009
231
Catalina 30 Lake Perry, KS
I have been observing photos of Macgregor 25s which appear to have been converted to cutter rigs. It looks as though blocks have been added to the masthead and halyards have been installed forward of the roller furling units which have also been installed. Wouldn’t this type of modification require a major reconfiguration of mast placement in addition to the installation of a reinforced bowsprit attachment?

You may have seen the Newport Venture/Macgregor. Kind of a cult boat these days,

 

Giro

.
Jul 23, 2019
62
MacGregor MacGregor 25 Monterey
No. I’m very familiar with the Venture 23. That’s not what I’m talking about. The V23 was designed by Roger Macgregor and was engineered in accordance with cutter rig specifications. Very Hanson, nostalgic little boat. What I’m referring to is the M 25s that have been dramatically modified. Fascinating stuff.
 
Sep 17, 2012
80
Morgan 383 Fairhaven, NY
Anyone ever have to short tack a cutter rig up a channel? Dreams of converting to a sloop usually follow.
Leave it alone is my advise.
 
Jun 9, 2008
1,643
- -- -Bayfield
As mentioned above, the J area (distance from the mast to the stemhead fitting) is longer on a cutter rig than a sloop rig. While it might not be feasible to move the base of the mast aft, it is feasible to add a bow sprit to increase the J area. But it needs to be done so that it can withstand the rigors of the forestay attached at the outer end, which means it has to be strong and also supported by a bob stay beneath. The next problem, as explained, is that you need to make the rig into a masthead rig so that the yankee (foresail) forestay attaches to the top of the mast and runs to the outer/forward end of the bow sprit. Then, for proper mast support, you have to have side stays, with spreaders to support the loads up high in the mast. You could do this by making your existing side stays as intermediates and then adding uppers that go to the near top of the mast. But then you'd have to change the spreaders to accommodate the two shrouds at the ends and also install a double chain plate at the deck level to accept the 2nd shroud too. But, to me, it makes sense to just buy a cutter if that is what you want and don't bastardize this boat.