Raising and shortening mizzen boom

[moseriw]

as the mizzen is the sail that drives you upwind - not a good idea.

[psk125]

Originally Posted by moseriw

as the mizzen is the sail that drives you upwind - not a good idea.

Isn't the mizzen often not used going upwind because, being backwinded by the main, it fails to generate much driving force?. Many ketches and yawls were designed to benefit from racing rules in the '60's that didn't penalize them much for the mizzen sail. Racers would not bother to hoist the mizzen for upwind work, and then spread them and mizzen staysails and mizzen spinnakers for going downwind.

[waterman46]

Originally Posted by moseriw

as the mizzen is the sail that drives you upwind - not a good idea.

Relative sail area of main+genoa to mizzen would determine if it makes a difference upwind. Most authors I've read characterize the mizzen as a "reaching" sail. And it's good any time in a blow, but not for upwind.

Upwind it's mostly the slot between the foresail (jib, genoa, staysail, etc.) and the main that drives boats whether sloop or ketch.

How does the helm balance without the mizzen upwind? If mizzen is needed for balancing the helm, then it's useful upwind, but it isn't for speed unless there is a strong lee helm (boat wants to fall off course downwind unless corrected). Unless there is a a strong lee helm w/o the mizzen, I don't think there is any difference in speed.

In our ketch, I have tested this many times. So we seldom use the mizzen upwind unless the main is down or double reefed and the wind is >30 knots or we are not trying to get upwind. In normal conditions with full main or even single reefed, upwind the mizzen doesn't make a whit of difference in speed or helm and probably just adds as much drag as it does forward thrust.

[kenbo]

The sail plans of the Shannon 38 and Offshore 41 are considerably different. The Offshore 41s mizzen is a much smaller percentage of the total sail area. This is not the case with the Shannon 38.

Your boat your call but I'd get the opinion of a respected sailmaker as to what you might likely expect the sailing difference to be.

[kenbo]

Originally Posted by waterman46

Relative sail area of main+genoa to mizzen would determine if it makes a difference upwind.

Upwind it's mostly the slot between the genoa and the main that drives most boats whether sloop or ketch.

How does the helm balance without the mizzen upwind? If mizzen is needed for balancing the helm, then it's useful upwind, but it isn't for speed unless there is a strong lee helm (boat wants to fall off course downwind unless corrected). Unless there is a a strong lee helm w/o the mizzen, I don't think there is any difference in speed.

In our ketch, I have tested this many times. So we seldom use the mizzen upwind unless the main is down or double reefed and the wind is >30 knots or we are not trying to get upwind. In normal conditions with full main or even single reefed, upwind the mizzen doesn't make a whit of difference in speed or helm and probably just adds as much drag as it does forward thrust.

I fully agree that the helm balance should be fully tested and understood before any changes be made. Your sail plan is very different than the Shannon 38, a cutter ketch with the foresail on a bowsprit. My guess based on the relative size of the mizzen it plays a significant role in helm balance. But only on water testing will tell.

[waterman46]

Originally Posted by kenbo

I fully agree that the helm balance should be fully tested and understood before any changes be made. Your sail plan is very different than the Shannon 38, a cutter ketch with the foresail on a bowsprit. My guess based on the relative size of the mizzen it plays a significant role in helm balance. But only on water testing will tell.

Yes, and I've often wished I could move center of effort forward a bit by installing a bowsprit, but that would be a big project.

For the OP, if you go sailing and compare performance with full mizzen and a single reefed mizzen, that should give you an answer close enough. I assume you only need to raise the mizzen boom a few inches, not feet.

[Sailmonkey]

Originally Posted by moseriw

as the mizzen is the sail that drives you upwind - not a good idea.

Depends on the boat.

Our mizzen doesn’t drive much, but it does balance the Genoa.

Off the wind I strike it because it just causes the stern to slew around.

[Cheechako]

Originally Posted by moseriw

as the mizzen is the sail that drives you upwind - not a good idea.

Yeah, that's why all the racing boats have a mizzen....

[DarwinHolmstrom]

This is very helpful. Thank you. You all are explaining things that I've noticed and have been trying to figure out. Unfortunately I'm on Lake Superior so I won't be able to go out and explore all this until the water gets a little less hard.

[CarlF]

Call Bill Ramos at Shannon. He'll check with Walter who designed it. Won't cost you anything. They'll probably remember your boat too.

He'll tell you exactly how it will affect sailing - I doubt he'll much like putting all that hardware on the stern - but it's your boat

Theres a good Shannon Facebook group.

[DarwinHolmstrom]

Originally Posted by CarlF

Call Bill Ramos at Shannon. He'll check with Walter who designed it. Won't cost you anything. They'll probably remember your boat too.

He'll tell you exactly how it will affect sailing - I doubt he'll much like putting all that hardware on the stern - but it's your boat

Theres a good Shannon Facebook group.

Thank you! I'll contact him tomorrow. I've always wanted an excuse to contact them. I'm not crazy about messing up Sarah Belle's beautiful ass either, but since I'll be living aboard her solo, hopefully for the rest of my life, this seems like the most manageable solution.

[cowtownsrevenge]

I have done this, just as your thread says, I had no effect on sailing after the refit. However I did add a 4 blade feathering propeller.
I cut off 1 metre off the boom, and 400mm off the sail. I believe the vessel now holds a better course but may be due to the new prop.
The vessel is a 40ft islander long keel, ketch.

[DarwinHolmstrom]

Originally Posted by CarlF

Call Bill Ramos at Shannon. He'll check with Walter who designed it. Won't cost you anything. They'll probably remember your boat too.

Bill remembered everything about my boat! I had a very nice conversation with him. Shannon is a great organization and Bill is a great guy. He said that the end result would be similar to what Cowtown posted above. Thank you both.