Remove the Mizzin mast?

[fgraham]

I have a Hereshoff design sailboat that has the mizzen mast removed and the boom extended to create a sloop. L Francis Herreshoff designed it as a Ketch. Won't this throw everything out of balance? It sails smoothly when the wind is not really strong.

[sainted]

In theory, removing the mizzen will pusg the center of effort produced by the rig forward off the center of lateral resistance of the hull. Doing so would cause lee helm, Eric would dramatically affect the vessel's ability to go to weather. Often when re rigging a ketch as s sloop, the main mast is moved aft to balance the center of efforts properly. If you can get the original sail plan for your vessel, you can figure this all out pretty easily. The center of lateral resistance will be marked pin the drawing. The center of effort for the old rig will be marked on the drawing as well. Draw the new main sail triangle on the sail plan and find its center, which will be its center of effort. Compute the square footage off the main. Draw a line connecting the center of effort for main and fore triangle. Find the proportion of the fore triangle to main triangle sail areas. That is, sixty/forty or fifty-five/forty-five. Make a mark on the connecting line brethren the triangles that is proportional to toy calculation. For example, if the ratio is fifty fifty you'd put the mark in the middle off the line. That's your new center of effort. If it's behind the center of lateral resistance, you'll be ok. If it's in front, make the main bigger or move the mast further aft.

Form there, sail trim. Have fun!

[fgraham]

I wonder why on earth would anyone change a Herreshoff Diddikai that way? He thought it was his best design although there were only 7 built. Mine is the 1946 Natoma.

[Sailmonkey]

Maybe it was a great design that sails better without the mizzen.

Why the same question?

http://www.cruisersforum.com/forums/...ed-196876.html

[Dave Humphreys]

If you can, return the rig to its original configuration as a Ketch. It will look right, sail better, and give more sail options for a variety of wind conditions. My Allied Princess 36 was designed as a Ketch but they also made a sloop version by moving the mast abaft around 2 1/2 feet and lengthening the boom. If the mod you have did not involve moving the mast (really difficult) it IS out of balance!

[Cheechako]

It may be fine. Let's face it, few sail with the mizzen up anyway! The boom was extended so they tried to offset the potential imbalance. The "lead" used to predict balance is a guessing game at best, as many designers admit. Many designers also created boats with way too much weather helm. Then there is the sails themselves. The balance on a boat with a 150 Genoa vs a 100 jib is different. Every time you change a sail or reef the balance is different. It's a moving target. I wonder what the reputation for weather helm is on the Diddikai design? How does it sail?

[IslandHopper]

Originally Posted by Sailmonkey

Maybe it was a great design that sails better without the mizzen.

Why the same question?

http://www.cruisersforum.com/forums/...ed-196876.html

And...... http://www.cruisersforum.com/forums/...ma-195926.html

Op, have you tried asking the question of the previous owner(s)? did you enquire before buying?

[Mainebristol]

Originally Posted by Cheechako

It may be fine. Let's face it, few sail with the mizzen up anyway!

? I can't recall the last time I failed to set mine. The boat balances better that way. I tend to drop the main if I get too much air, but never the mizzen.

Besides, I like having more strings to pull.

[IslandHopper]

Originally Posted by Mainebristol

? I can't recall the last time I failed to set mine. The boat balances better that way. I tend to drop the main if I get too much air, but never the mizzen.

Besides, I like having more strings to pull.

Correct, in my case the Mizzen is usually the first to go up and last to come down.....

[Cheechako]

Originally Posted by Mainebristol

? I can't recall the last time I failed to set mine. The boat balances better that way. I tend to drop the main if I get too much air, but never the mizzen.

Besides, I like having more strings to pull.

Yeah. Just thinkin' .......I would say 80% of boats I see out have the mizzen furled. Offshore work is probably a different thing though.

[Bill O]

We use our mizzen often, but many are now so tuned in to the sloop rig, they never did/don't realize the benefits of the mizzen. This is explained in other threads, so I'll not going into it here.

With the increased boom length you'll probably see good light air performance with a relatively easy helm. As the wind picks up, with the center of effort (CE) now moved back (due to the longer boom/foot), more weather helm will be noticed with a full main. To move the CE forward and ease the helm, you'll need to reef the main.

Bottom line, you'll need to reef the boat earlier than with the shorter boom, but the boat should sail fine. Also you will not have the benefit of the mizzen, which quite frankly I have grown to understand/appreciate and would make it difficult to go back to the sloop rig.

It would be a fairly sizable expense to re-rig it back to a ketch unless you had all the old parts. Also it depends on your intended use if it worth it. If you are going out for day sails, probably not worth it. For cruising short handed would consider it very useful.

Bill O.

[Cheechako]

Originally Posted by Bill O

We use our mizzen often, but many are now so tuned in to the sloop rig, they never did/don't realize the benefits of the mizzen. This is explained in other threads, so I'll not going into it here.

With the increased boom length you'll probably see good light air performance with a relatively easy helm. As the wind picks up, with the center of effort (CE) now moved back (due to the longer boom/foot), more weather helm will be noticed with a full main. To move the CE forward and ease the helm, you'll need to reef the main.

Bottom line, you'll need to reef the boat earlier than with the shorter boom, but the boat should sail fine. Also you will not have the benefit of the mizzen, which quite frankly I have grown to understand/appreciate and would make it difficult to go back to the sloop rig.

It would be a fairly sizable expense to re-rig it back to a ketch unless you had all the old parts. Also it depends on your intended use if it worth it. If you are going out for day sails, probably not worth it. For cruising short handed would consider it very useful.

Bill O.

I think you got this wrong Bill, he's more likely to have lee helm without the mizzen right? I dont think they could make the boom long enough to counteract that!

[Bill O]

Actually I'll tell you how I know this to be true (at least on our boat) and it all depends on where the center of lateral resistance (CLR) location is in the boat.

We added a hard top bimini dodger so I could fit underneath it, and with that we had to raise the boom almost 2'. We had a new main made with a longer foot and a longer Hall spar from a J130 to compensate for the lost sail area.

When we did test sail (just w/main & head sails), we did see the need to reef earlier than before (to reduce WH) but had better light air performance. So comparing apples to apples in our own boat I'll say it was true and the longer foot caused more WH.

[TrentePieds]

In pictures of Natoma she LOOKS unbalanced without her mizzen. Without a lines drawing and a sailplan (as modified) there is no way of knowing if she is, except by the helm she carries when sailing.

On the surface of it, I would expect her in her current configuration, even with a longer boom, to carry lee helm, and that is not good!

IF you have a sheer plan of her, finding her Centre of Lateral Resistance is easy enuff. Drawing a sailplan, e.g. for a cutter rig, is also simple. PLACING the sail plan foe'n'aft to get the lead within acceptable bounds is what is so much fun given the structural constraints of the boat "as is".

Why don't you see if you can find a sheer plan and then come back to us?

I had a Seabird once that had been similarly buggered about. There are lots'n'lots of boat owners about who think they know better than the designer of their boats :-)

TP

[Bill O]

fgraham,
What kind of helm are you seeing with stronger winds? Does it want to go upwind strongly or fall off the wind?