My top hat has double spreaders. Ive noticed alot of the bigger boats have double but even some boats jist as a glance today around mooring like east coast 31s only have 1. Whats the benefits of double spreaders. Why wouldn't abigger boat have them.

Bigger boats do have them. Really big boats have triple spreaders. My 28 footer has
a single spreader, which I would have thought would suffice for a Top Hat. But...then again,
I don't know that much about sailing yet.

Thsnks Sam. I didnt word that post too well. Sorry! I just noticed that bigger boats than mine for eg a compass 28 and a ec31 only have single. I really love my top hat. Its.very heavily rigged it would seem for a small boat.

Mast Design relates to Column Theory a very complicated understanding of moments of inertia, forces on the spar, area of sails and configuration, material of the mast, and distance of the chain plates. Other factors are configuration of the rig either no backstay, runners, swept back spreaders or in-line.

The use of the yacht one design bay racer or offshore cruiser.

In the old days of IOR racing and before Carbon Fibre Masts I worked for Zapspar Yacht Masts at Brookvale as a mast designer the masts churned out were in their day very good we developed an excellent way of tapering the rigs and also did cruising masts and development of Formula 40 rotating Cat rig.

The S&S34 Mk1, like mine, has a single spreader. The Mk2 has a one metre taller mast and double spreader. My sisters Valiant 40 is single spreader. I defer to people like Whiteout on the design issues. Suffice to say, if the boats perform well the design is right.

Thanks alot guys!

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whiteout said..




Mast Design relates to Column Theory a very complicated understanding of moments of inertia, forces on the spar, area of sails and configuration, material of the mast, and distance of the chain plates. Other factors are configuration of the rig either no backstay, runners, swept back spreaders or in-line.

The use of the yacht one design bay racer or offshore cruiser.

In the old days of IOR racing and before Carbon Fibre Masts I worked for Zapspar Yacht Masts at Brookvale as a mast designer the masts churned out were in their day very good we developed an excellent way of tapering the rigs and also did cruising masts and development of Formula 40 rotating Cat rig.

Right on whiteout, all of the above and eccentric loading from the crane and induced bending from slugs and battens and rigging attachment points off the centroid of the section. Just leave it to the spar designer..

Triples.

and then you get boats like mine, 8 metres long with triple sweptback spreaders and basically what is called a cathedral rig.

little boat with tall rig.

My mates little Elliott 7.8 has triples but it also has a fairly flexible mast

Regards Don

My god, that Crossfire 20 with the triple spreader rig in Sectorsteve's pic must fly in light winds! That spar is a monster.

As to why a bigger boat wouldn't have multiple spreaders; certainly for a short time in the early '70s, some top racers thought that the fewer spreader the better, because of the reduction in weight and windage. Advances in design and sailcloth meant it was a short-lived period; by the mid '70s narrower, thinner-walled sections that could bend were being used to control mainsail shape, even in masthead rig boats. To keep these narrow sections up, and allow for narrower sheeting bases, people switched to putting more spreaders on.

Then when fractional rigs came along, and the mast bend could be controlled more by the topmast backstay and there was a shift towards lighter, smaller and simpler rigs, things changed again briefly, before they once again became more complicated in the search for easier tuning and more efficient aerodynamics with lighter rigs. Or that's how I understand it and recall it, Whiteout would know more.

As another example, you used to have to use truckloads of bend to depower a dacron mainsail, because the cloth itself was so stretchy. Theoretically, you may have needed (say) 6" of mast bend to make the mainsail flatter when the breeze picked up - but in practice you needed an extra few inches of bend to allow for the fact that the sail itself was stretching. The whole rig had to be designed to achieve the required mast bend.

These days the sails stretch so little that you need less mast bend to depower when the wind picks up, so the mast design can be different; spars can be bigger, stiffer and stronger so they may need fewer spreaders.

The main point is that this sort of thing is often created by multiple factors, including rating rules, advances in technology, and the flow-on effects of other design changes. So sometimes trends go back and forth; not because of fashion or because of anyone being silly (as some people sometimes claim) but because things like the available materials technology have a huge effect on design.

Illingworth actually designed the Top Hat rig with 2 spreaders in England where at least six were built but when they were built here in Australia the rig was redesigned with only one spreader.

As to the reason why and who did the redesign I have not been able to track any information down but, there is also the possibility that Illingworth himself redesigned the rig as I do know he had a lot to do with Mouldcraft [in Melbourne] who built the first 10 or so in hot moulded timber.

I do know that some timber Top Hats [Mark 0] were amateur built with two spreaders.

My East Coast 31 has a double, but perhaps that is because the original single fell over 1 day.......

Anybody got pics or details of the connection between the cap shroud and the diagonals on multi spreader rigs? I can imagine a triangular plate, but that would have alot of windage. Special swages? Tension adjustment for individual diagonals?

ill take some tomorrow before i put mast back up.

I was under the impression that the extra spreaders gave a stronger rig. Having owned two adams designed boat's a tasman 26 and my Mottle both have double spreaders. Don't forget some fractional rigs just have a diamond on the top to add strength above the forstay especially when running mast head kites.

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Yara said..
Anybody got pics or details of the connection between the cap shroud and the diagonals on multi spreader rigs? I can imagine a triangular plate, but that would have alot of windage. Special swages? Tension adjustment for individual diagonals?

Hi Yara,
I am unsure where you mean. The end of the spreaders, or the inner where the diagonal starts?
See pic for where I am thinking.

Think he means how upper shrouds are connected. Mine are between the bases of the upper spreaders that share a bolt with the upper spreader bases to the lower spreader tips that are connected with cleavis pins
You can make adjustments on mine but for now im not touching the adjusters.

And then you have continuous rigging that starts under the top spreaders, travels down over the end of the lower spreaders and down to the deck along side the cap shrouds.
Not usually seen on rigs with more than two spreaders.

Yes, at the ends of the spreaders where all three wires need to be connected, and adjustment is also required.

I run double spreaders, but nothing above the uppers except cap shrouds.
This is my upper spreader, which has only the cap shroud. The shroud is not fastened, clamp is tightened up to remove slop but not to deter movement.




This is the lowers. Upper and lower shrouds and diagonals are anchored to the spreader. The diagonals are adjusted here.

My spreaders also act as the anchor point for the diagonals. This is my upper spreader from underneath.



The capshrouds get a dirty great machined pin cut in two with a internal thread. The static loads on this are really big, it's not like a whippy 3 spreader setup. I notice I get hardly any mast bend at all.



So my only 3 wire termination point I get is at my lower spreaders with diagonal and shrouds all meeting.

I wonder if a cap shroud thats slightly oversized is an issue. Ive replaced an upper spreader and am re using the caps but the new spreader is slightly narrower than the original. Ive got rubber weld on the cap/spreader ends but there's a slight bit of play.

Thanks Shaggy. Classy bit of engineering. Wonder how they did it on the older boats.

This is mine, but that is not me {I would be wearing sandshoes]

they look exactly like mine.