interesting mast idea

Rigging components, external fittings and Sails
northerncat
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interesting mast idea

Post by northerncat » Mon Apr 09, 2007 8:36 pm

i know that bi plane rigs are now becoming somthing exciting in the world of catamaran designing but heres an alternative that a guy building a cc40 (mike waller) is putting on his, hes got mike altering the design and configuring the rig a little so he can use it

http://boatdesign.net/articles/mast-aft-sailing-rig/

jaleel_da_sheik
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Re: interesting mast idea

Post by jaleel_da_sheik » Thu Jul 14, 2011 1:10 am

I recently re-discovered that same article and it got me to thinking about sail plans and mast options. The author seems to line out some pretty convincing points as to why this setup is worth looking into: cost savings, weight savings, safety, simplicity, etc.

Anyone out there willing to try and poke some holes in this idea? I'm wanting to hear about the possible negatives of this design. What about trying to incorporate it into an Easy build?

Regards,

'sheik

jaleel_da_sheik
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Re: interesting mast idea

Post by jaleel_da_sheik » Tue Jul 19, 2011 8:17 am

hmm, no bites.

hey northerncat, if you are still hanging around and checking this website, do you have any contact information for the guy building the waller with the aft-mast? i'd be interested in hearing his take on the design.

'sheik

rexd666
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Re: interesting mast idea

Post by rexd666 » Wed Jul 20, 2011 1:41 pm

Ok I'll bite. The main negative I can see with any rig that moves away from the mainstream is you limit potential buyers to others that also understand the benefits in your rig choice. The problem is 99% of people will look at a picture of it, see if is different and move on. FYI Bi-rig guys I respect your decisions to go that way, so no flame wars please.

Looking at this particular design I would be wondering how the mast is supported on the angle and transferring the loads to hulls through the bridgedeck, it would require 2 bulkheads to support the base and another to support the angle.
But my engineering skills extend to blowing holes in the ground only so I really have no idea, hence I am going standard rigging, and will get someone who knows what they are doing to set it up.

While not wanting to send you away from this site, you may get more bites and possibly some heated discussion over at BoatDesign, they seem to have more professionals hovering around willing to share their opinions on anyone elses choices. Feel free to link to us for the original question, all drives extra traffic our way. :D

Steve

Jim
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Re: interesting mast idea

Post by Jim » Thu Jul 21, 2011 9:03 am

A non conventional rig would have problems with re-sale for sure, but that doesn't make it a poor design or less efficient on the water. (no one is saying that here) As with most things people are like sheep and will go with what is the most common method of doing something, which in a lot of cases becomes the cheapest method as well. Nowhere is this most apparent than with anything to do with speed. Over the years I have been involved in various forms of motorsport and the theory is that the winningest car/boat/bike must be the best, not necessarily so, something totally different might be better, but the cost of development can be massive, so a lot of fantastic ideas never surface and remain as sketches on the back of serviettes.
To the Bi Rig guys, good on you and I admire the fact that your gonads are big enough to do something A "little out there".
Jim.

Mick@itc
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Re: interesting mast idea

Post by Mick@itc » Thu Jul 21, 2011 10:55 am

Hi all

I ahve an ongoing conversation with Brian Eiland about the concept and design. For me the big thing is it opens up design possibilities with the forward bulkhead. The story so far is...
As you know the concept is from the mid 70's and has hibrenated for some time, popping up every now and then. Lately there have been some boats built with the mast design and the results have been very positive from the design into reality viewpoint. The next stage of development is doing an Finite Element Analysis which will give a much better understanding of the dynamics of the structure rather than the static load designs that have been done to date. There are a few different people working on this slowly, as most things it comes down to money.
Jsut for the non tecnical of us the loading at the base of the mast resolves into three load vectors, verticle and horizontal X and Y. In laymans terms the total load is split into the three components which add up to the total load . Given it will be a pin joint for design purposes (no bending moment transfer) the horizontal loads (X and Y axis)will be taken by the "plate" element which is the deck of the flybridge. The vertical component or downward force is the one that creates the main load on the bulkhead. In theory that should be reduced becasue more proportion of the load is going into the horizontal load component. Anyway, suffices to say that the load configuration at the base and in the stays needs a fair bit of dynamic analysis to fully understadn what structures are needed where.
I for one am looking forward to it.
Yes I agree with the re-sail value it will be a smaller market, but I guess I want to keep an open mind on the design of a boat.

Regarsd
Mick
Mick
If all you have is a hammer...everything is a nail!

kjay
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Re: interesting mast idea

Post by kjay » Mon Jul 25, 2011 4:54 pm

Check this out for another idea www.sail-the-difference.com
John.

Corley
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Re: interesting mast idea

Post by Corley » Wed Sep 28, 2011 2:30 am

It's true the small area behind the mast on the mainsail has some unattached flow but it rapidly reattaches and contributes to lift, the fastest sailing boats in the world have no jibs look at iceboats, A class catamarans, C class catamarans or the wing rig on the 130mph greenbird on youtube. These boats generate lots of apparent wind and the lift/drag coefficent of the rig is vital to their success.

The major problem with A frame type rigs and single masts without mainsails is the drag that the mast section and the diamonds create as they are pulled through the air with no mainsail to reduce the drag signature caused by detached flow, the mainsail serves the dual purpose of providing the major drive to the boat and reattaching flow behind the mast. For ease of handling I can see the virtues of the rear stepped mast with furling headsails but from an sailing efficiency viewpoint It just doesn't stack up. Do a search on Tom Speer's posts on Boatdesign.net for a more technical write up on pros and cons of sloop and headsail focussed rear mast rigs.

Now it could be that the improved ease of handling is worth the loss of efficiency on a cruising boat, I think thats up to the individual to decide but I've always found with good mainsail slugs and proper lazyjacks reefing is not a huge issue.

I politely disagree with Brian's take on the reasons why sloop rigs are favoured its not a matter of being slaves to tradition racing sailors will do anything to find an edge of even a 1/10 of a knot and the sloop rig has proved itself time and time again to be the best means of extracting performance on all points of sail.
Multihull news and my projects http://trimaranproject.blogspot.com.au/
Multihull Yacht Club of Victoria http://mycv-news.blogspot.com.au/

44c
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Re: interesting mast idea

Post by 44c » Wed Sep 28, 2011 3:23 pm

Exactly right. The designers of Wild Oats etc slaves to tradition???? Canting keels and daggerboards, yet supposedly they go with a sloop rig NOT because it's fast, but because it's "traditional"? The designers of boats like Banque Populaire slaves to tradition??? I don't think so.

44c
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Re: interesting mast idea

Post by 44c » Mon Nov 21, 2011 8:31 am


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