Lowering the Boom (as in, no boom)?

[NotCook]

I'd like to extend Loyalist's discussion further on the question of eliminating the boom entirely. In our case, I'd like to eliminate the mizzen boom entirely. We are contemplating installing behind-the-mast furling, eliminating the boom, and allowing it to be loose footed just line the genoa. This would allow us to install a realistic bimini over our quarter deck. With the mizzen boom bottom at about 5'10" above the deck, it is too low for a practical bimini, yet high enough to be a pain to drop and cover the sail. A furler would simplify sail management dramatically.

So, one of the questions Bob asked was about just having a sheet (to the traveler), and the furling line. How dramatically would this impact performance and sail trim options? I expect it would require a slightly smaller sail, since the end of the boom currently extends beyond the traveler, but I think we can live with that. Racing isn't relevant to us, either. I think we will have plenty of mizzen to balance our headsails, particularly given that our mizzen mast is nearly as tall as our main - unusual for a ketch.

Likewise, we would eliminate our mainsail in favor of a mizzen staysail, again, to simplify sail handling. Our intention would be to eliminate the main boom as well, and continue to sheet the main directly to the (former main) traveler. Again, this would reduce the sail size somewhat. On the otherhand, if necessary, we could add a topsail to the existing main mast, utilizing the existing main sail track.

So, the benefits of the furling, and eliminating the booms, are obvious. We'd like to hear the drawbacks from those of you who might have insights. I realize most are not familiar with sailing ketches, but the function of the boom, and what it adds to the sail trim should still translate.

 

[vhoisington]

Sounds like you will give up a lot of sail area. Not sure its a real consideration but something to consider. Also, you've now put much of the load on the Mizzen mast, is it setup for this amount of sail area?

One other thing to consider, each sail, as a part of the original sail plan has a Center of Effort (COE), moving things back to the mizzen probably changes this considerably and now much of the effort is centered around the mizzen instead of the main. Depending upon how the underwater parts (keel, rudder, etc. are set up, each with their own COE), the boat will behave differently on all points of sail. You'r proposed changes move much of the driving forces much further back on the boat, that beam reach you now enjoy won't balance as well and will tend to round up since the COE on the sail plan is now behind the COE of the keel/rudder. I'd talk to a good naval architect who can do the math and provide the right calculations to see what you could expect.

Good luck,

 

[Davidasailor26]

I don't know that you would be able to have much sail area at all to keep the sheeting angles any good. If you bring a sheet up from the traveler the sail will need to be small enough so that the line bisects the angle between the foot and luff. That seems like it would be hard to achieve unless your travelers are very far back. The other problem is that when sailing off the wind you'll be sheeting from the clew all the way inboard to the traveler. That will probably put a lot of curve in the sail, making it very inefficient and adding heel angle.

 

[JohnShannon]

How about a wishbone boom instead? I think that would generally raise the height of the boom in most places

 

[capta]

Without a mizzen boom you won't be able to use it very far off the wind, nor can you get the full advantage of a mizzen staysail, as it should sheet to the end of the mizzen boom.
I think a much better option would be to raise the boom and gooseneck to a height you can live with. You'd loose a bit of sail area, but not the use of the mizzen off the wind or mizzen staysail.
Most boomless sails are between the masts, like a staysail rigged main on a ketch, or boomless foresail on a schooner.