Where to "Stick" it???

Pros and Cons Please. How would a boat handle that uses an oversized Jib or Genny on a mast that is at the approximate midship location with a Yawl style mizzen of about 1/3 the size of the J or G...and no "main" sail in between. The mizzen would sheet to a boomkin and back. This is something I have been knocking around as a small (very) shallow water cruiser. The reason I want the mast aft is so there is an uninterupted area for a decent double berth, with mast just aft of the bunk, and enough room for a bit of a galley, a head and maybe an easy chair and stove aft of the mast. Oh, and the LR would be Bilgeboards, Bilgekeels or (Ahem) Leeboards. Pardon the drawings as they were quickly done up in Freeship and Paint.

Steve
(I hope I got all the sail terminology right )

 

Hi Steve!

First, let’s sort some terminology. A Genoa overlaps the mast (as drawn) or else it’s a jib. If the mizzen mast is located in front of the rudder stock, it’s a ketch, if not, a yawl.

Basically what we are dealing with here is a question of balance. This is quite a complicated subject but generally you will need to consider these points.
1. The centre of effort (CE) of the rig needs to be established. In a two-masted rig this is normally done thus...
• Establish the CE of each sail – draw a straight line from the clew of each sail to the centre of the luff. Now draw another straight line from the tack to the centre of the leach. At the point where these two lines meet is the generally accepted centre of effort of the sail.
• Now draw a line which connects the CE’s of both sails.
• Work out the area of each sail
• Express each as a percentage of total sail area and mark this on the line connecting both CE’s. (E.g. if the sail areas were equal the balance would be 50% or half the length of the connecting line. A “third” of the area (as you mentioned) would place the CE at 2/3 along the connecting line towards the larger sail.
2. From that point, draw a line perpendicular through the waterline and that will be the CE of the RIG.
3. The CE of your leeway resisting force (whatever you choose) should then sit about 11 – 15% (as percentage of LWL) aft of the perpendicular you have just drawn.

Looking at the illustrations as supplied, I detect that too much power will be generated forward causing extreme lee helm. Although the mast is amidships, the centre of effort of the dominant sail (jenny) would be considerably forward of that point forcing the CE of resistance too far aft. An “eyeball estimate” of what is drawn would place the CE of resistance on a perpendicular roughly the aft of the cabin. This would make for quite extreme handling.

What you want can be achieved – just play around with these figures, balance everything out and you’ll soon be in the ball park.
Good luck!!

 

Perhaps I am misreading something here but when you say
"Looking at the illustrations as supplied, I detect that too much power will be generated forward causing extreme lee helm. Although the mast is amidships, the centre of effort of the dominant sail (jenny) would be considerably forward of that point forcing the CE of resistance too far aft. An “eyeball estimate” of what is drawn would place the CE of resistance on a perpendicular roughly the aft of the cabin. This would make for quite extreme handling."
something reads a little funny.

If the CE of the sail is far forward wouldn't the CLR...being 11-15% of the DWL aft of the CE of the sail also be relatively far forward...somewhere around the middle of the cabin?

Steve

 

Lewis,

What Trev is talking about is center of area, not CE, so you need a fudge factor to make it work.

Big genoas make it difficult to modulate power while sailing, in puffs, they tend to power up instead of down.

How about sticking the rig in the bow instead?

Yoke.

 

In short, very poorly.

Such rigs have been tried even to the point that there is only one sail with the mast well aft and only a roller furling jib, or genny.

Can't change sail area without lousing up balance and a small mizzen is not up to maintaining balance.

Rig is highly stressed trying to hold adequate forestay tension.

Winching one huge foresail in tacks would be a killer to old arms.

Getting caught in a sudden blow could be a catastrophy even if the rig stays up. You can luff a mainsail but trying to luff a big genny doesn't work very well.

None of the attempts I know of have been successful enough to be copied.

Even with the disturbance of the mast, cat rigged boats are a far better solution.

It's not considered a good idea but maybe you can find the secret, if there is one.:idea:

 

What if you drop the bowsprit and reduce the forsail down to the size of the foretriangle. Then add a boomless main that sheets midway up the mizzen. It'll get you away from such a large piece of canvass hanging of of your forestay, move your CE aft and give you more options for reducing sail and still maintain good balance. You should also reap the performance benefits of a multisail system.

Good luck.

 

Somebody else's idea.


http://www.runningtideyachts.com/assets/515profilesailplan.gif

 

Wow, that has to be the worst thing I've ever seen in my life!

I think your idea of the small jib and adding a main by far the most sensible idea so far...

 

Oh, I don't know. The mast will punch through the cabintop long before the aft shrouds yank the transom out of the boat. That rig is not the worse I've seen, but it's close.