Main-less rig

[brian eiland]

..... a LOT of discussions of A-frame type rigs.
http://www.boatdesign.net/forums/boat-design/wishbone-sailing-rig-1999-3.html

I just went back thru that discussion thread looking at all the posting for details that have been experimented with. I made some notes of postings I wanted to remember and/or look at a second time. Perhaps I should publish those notes?

Here is that list of postings on that subject thread that I found most interesting to review,...in anticipation of providing a new A-frame style rig alternative on a new 'picnic/weekender' catamaran design I am contemplating.
...word document

 

[brian eiland]

By now many of you readers are aware of my affinity for the mast aft or aft mast sailing rig concept. For the most part I am content with this being a singular mast column, stepped a little further aft on the vessel, and canted forward approx 10 degrees.

However, I’ve had more than a few people interested in alternative rigs ask about my rig and bi-podded rigs in the same questioning. Now, I was always enamored with bi-pod mast rig aboard Olaf Harken’s ‘Procyon’ vessel.

So here I present some variations of the mast-aft rig configured with a wishbone/bipod mast column. There is a wide based version, and a narrow based one. And with each of these there are two different spreader arrangements that affect the very important cap shroud angle. Modern mast and rigging materials could very well make these unusual rigs a viable entity

 

[Spiv]

So here I present some variations of the mast-aft rig configured with a wishbone/bipod mast column. There is a wide based version, and a narrow based one. And with each of these there are two different spreader arrangements that affect the very important cap shroud angle. Modern mast and rigging materials could very well make these unusual rigs a viable entity

Brian,
I will go for the wider rig, but stepped against the saloon sides, in that way support could be created on a bulkhead, all the way to the bilge if necessary.

If we use lower shrouds, we have to make sure they do not interfere with the mizzen (?? is this the name of the sail we want to use??).
I think that the backstays should be attached to the transoms, to get better angle.

What do you think of this drawing?

I see Matthews has brought devastation to your coast, I hope you have not suffered damages.

 

[brian eiland]

I'm going to have to give the whole idea some new thoughts.

And you are correct I was right here in St Augustine for that hurricane. Fortunately I did not suffer to much damage to my homestead as I was a few miles inland. But others around me did, and I've been helping them clean up the last few days. Falling limbs got a few roofs, and we've had to put tarps over them temporarily. I lost power for about 16 hours, but many are still without for several days now.

The ocean side residences took quite a beating from the sizable storm surge.

 

[brian eiland]

Is a furling main safe when singlehanding?

I found this to be an interesting and informative posting,...

http://www.cruisersforum.com/forums/f122/is-a-furling-main-safe-when-singlehanding-175698-18.html#post2352480



Great thread with lots of differing opinions and personal views. Some more strident than others but nevertheless interesting. Some of the opinions seem to be based on theory and not real world experience but are mostly worthwhile reading and considering for their diversity of views.

I realise that this thread has probably run to its logical conclusion but I thought it would be valuable to at least make the following information easily available to all who may venture this way in the future seeking information on furling main sails.

I attach a link to the ongoing SSCA Equipment Survey dealing with main sail furling / reefing and the overall analysis HERE.


I attach a link from that same survey of all the opinions expressed by owners who actually sail with the type of equipment that they are commenting on HERE .
It is quite a long read but very interesting and revealing and it is very germane to the extensive discussions that have been going on within this thread.

The one take away message for me is that there are failures in all systems from the simple to the more complex. All systems work flawlessly for some sailors yet other sailors have monumental problems with these same choices of equipment.
Probably the major difference here is that the operators of the various types of systems are the one thing where it is impossible to compare like for like.
No one system is right for every sailor with their own particular situation given the the inherent differences in the individual and indeed where they sail and in what they sail.

And for an interesting comparison I add the link for the analysis of those sailors who sail without an in mast or in boom furling system HERE .


When one compares the Breakdowns/Unit and Breakdowns/Year data for both the in mast units and those with battens/sliders it shows that there is a slight difference but overall the reliability is within what most (but not all) sailors would be prepared to accept for the perceived advantages that each system provides. (Please do not turn this into a mathematical argument about percentage increases or decreases).

What is obvious and revealing is that generally whichever system you choose they are mostly realiable and that is good news for all of us.

We are lucky to have so many choices to suit our own personal situations and budgets.

Now let's get that mainsail furled away neatly.
AussieWayne

Thank you to the SSCA for compiling all this information and much more.
There is lots of useful information on equipment and systems of all types
HERE .

 

[brian eiland]

Wishbone Boom

Hello all

My two cents on the mainless rig as I see this dicussion heading

- the bi-pole rig has one very severe engineering compromise it must cope with. It has to do with the compression loading on the rig.

The basics of compression loading are worked out using a formula called Eulers (say Oilers) column buckling formula. It takes into account the length and the cross sectional area of the column in the following way

P(critical load) = Pi Squared x EI/L squared

E is the Youngs modulus of the material and
I is the second moment of area of the section
L is length

Increasing the E or stiffness helps buckling resistance in a linear way. Twice as stiff gives twice as much buckling resistance BUT
Calculating I is tricky and basically it goes up exponentially (measured in the fourth power) as you increase the size of the section. A section only slightly larger can have twice the buckling resistance of smaller section.

The result of all this is that it will always be lighter, cheaper and less windage to support a compression load in a single compression member - one mast. Bipole rigs will have to be heavier than a single mast and weight up high is a no-no as well as increased windage. At least in all the cruising cats I know of there have been no issues with the main box beam. It is very easy to reverse engineer what works and fit this in with the accommodation so getting away from a single mast form an engineering standpoint is not necessary.

As to the stay behind the mast. I have seen this done with two cranes hanging out the back of the mast - really bad idea. It was on my mums cat and if I did the stay up tight then the mast would threaten to come down as it was heavily loading up the back of the mast. It also was a dog to windward. She got a normal fully battened main and the boat sailed much better.

I think it is a really good idea to have a rig that works super well to windward. In the 5 trips north I have done it is always a little hard to get south. On the Ozzie east coast you wait until the northerlies come. Just a couple of hundred miles south they are getting northelies but up at Cairns or Lizard island you still get southerlies. We have often used the good windward performance of our cat (and previous tri) to get south when the trades have eased and gone slightly east. Once south we have better chance of getting tailwinds. My wife prefers sailing to windward on our cat (as long as we can lay the course) So I would counsel a careful overview of the positive aspects of the normal sloop rig. I certainly enjoy my windward sailing and have not enjoyed sailing on cats where this ability has been compromised.
cheers

Phil Thompson

I've recently run across a few of your postings, ....and I'm going to look for more. I found your use of a wishbone boom very interesting. I've sought to utilize one on the mizzen sail of my aftmast rig.

http://www.boatdesign.net/forums/multihulls/open-bridgedeck-catamaran-design-53066-2.html#post734669


http://www.boatdesign.net/forums/multihulls/open-bridgedeck-catamaran-design-53066-2.html#post734731

Brian Eiland

 

[brian eiland]

I'm having a lot of fun reading back thru this subject thread and the 'Aftmast rigs' one,.......but i am limited in typing any replies as i broke my right wrist recently,...and i am right handed.