Tony bullimore - design question on the forestays

[hmm]

Some people have been talking about his attempt, I just want to ask about the boat design.

Looking at photos such as:
http://www.teambullimore.com/photo_gallery/hobart_28apr07/ppages/ppage2.htm

and

http://www.teambullimore.com/photo_gallery/hobart_28apr07/ppages/ppage1.htm

My first question was the great big pole extending from the base of the mast? over the front beam and forward. What is that doing and so forth.

Which pin failed? As far as I can make out, he has three forestays but of course maybe not all are holding the mast forward as much as each other. One is attached to said pole, then so is the second one - Is the pole attached to the beam or seagul striker here?
The furthest stay is attached to end of pole (is that really a forestay or just for hauling up the jib?)
What are the wires:
http://www.teambullimore.com/photo_gallery/hobart_28apr07/ppages/ppage2.htm
from the pole to the hulls for? The hulls are held in place by the beam, the pole is held near the seagul striker, the wires are so thin I can't figure out what they are for.

Are those two wires and the attachment at the seagul striker really holding the beam (and mast) down?

edit
and does that boom have a vang - why do some cats have vangs and some not?

 

[EBoat126]

Before saying anything more can I just state that I have huge admiration for Mr Bullimore, the guy is a legend. But isn't he trying to push the now well past it's bet ENZA New Zealand around the world one more time? Multihull design has moved on, tris are faster around the world, cats will win around the cans. /forums/images/graemlins/smirk.gif

 

[fluffc]

[ QUOTE ]
My first question was the great big pole extending from the base of the mast? over the front beam and forward. What is that doing and so forth. It's [primarliy for carrying the huge load of the Asymetric Spinnaker. Effectively it's a boswprit. Taking it back to the 'strong point' at the foot of the mast, and guyed from the two hulls. Dinghies have retractable ones

Which pin failed? As far as I can make out, he has three forestays but of course maybe not all are holding the mast forward as much as each other. One is attached to said pole, then so is the second one - Is the pole attached to the beam or seagul striker here? No idea what failes, but the pole shouldn't be considered primarily as 'attatched' to the beam, as it is primarily in compression. The main forestay (not the assymetric 'stay') appears to mounted on a saddle which transmits its' loading to the beam. The inner forestay is an oddity, as IMHO it would bend the pole in the wrong direction.


The furthest stay is attached to end of pole (is that really a forestay or just for hauling up the jib?) just for hauling up the Assymetric Spinnaker

What are the wires:
http://www.teambullimore.com/photo_gallery/hobart_28apr07/ppages/ppage2.htm
from the pole to the hulls for? The hulls are held in place by the beam, the pole is held near the seagul striker, the wires are so thin I can't figure out what they are for. to hold the end of the pole in place, stopping it whipping around. Like whiskers on a gaffer

Are those two wires and the attachment at the seagul striker really holding the beam (and mast) down?Yes, and also the pole

edit
and does that boom have a vang - why do some cats have vangs and some not? can't see the boom in these pictures?

[/ QUOTE ]

 

[Noddy]

I don't know why some cats have vangs but neither of mine do (16ft & 30ft).

The wide beam and long mainsheet traveler track means that we can use the mainsheet for holding the boom down when off the wind. Not that cats are off the wind very often.

 

[AngusMcDoon]

Dragonfly tris don't have vangs either, because...

1) vang only really useful when the boom is well away from the centreline of the boat, not a common occurrence on a tri. Within the normal traveller range the main sheet is a better way of controlling sail twist.

2) if the boom is out, a downhaul from the outer end of the aft beams can be used, which gives much better leverage being at the outer end of the boom.

I expect TB's cat will be similar, so vang not really necessary.

 

[hmm]

Thanks for those detailed answers.

Cheers

 

[hmm]

Thanks

 

[hmm]

Thank you