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  #1096  
Old 02-26-2017, 06:47 PM
CT249 CT249 is offline
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Originally Posted by brian eiland View Post
Did you access those memoirs of his on-line, or did you have a copy?



And why would a straight up standing mast have to be that much heavier because it didn't have a normal mainsail?

Oops, I think I found an answer to that question on that blog link...
I've got my own copy of the memoirs.

It's been explicitly said by people like Stearns since the '70s that a mainsail forms part of the structural support of a mast. That's one reason many offshore racers do not like sailing under storm jib alone.

The weight of the mast alone was obviously not a huge issue, because Hoyt felt that once the mast had been moved forward and given a conventional rig, the boat was as fast as the competition.
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  #1097  
Old 02-26-2017, 11:47 PM
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It's been explicitly said by people like Stearns since the '70s that a mainsail forms part of the structural support of a mast.
Let me ask you a question. Assume an analogous force-beam loading configuration.

Lay that mast (beam) out horizontally as a cantilevered beam with one end stuck in a wall (the deck). Now pull upwards at the tip just as the forestay does. And then in an analogous situation load some distributed weights onto the beam (outwardly from the wall) just as the mainlsail pulls on the mast tube as it rises from the deck.

Now ask yourself whether that beam (mast section on the horizontal) with the those extra weights has to be stronger than one with no added weights (no mainsail)??

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That's one reason many offshore racers do not like sailing under storm jib alone.
Now 'point loading' of the mast tube can be a different situation (where most of the loading is by a single or multiple forestays and backstays). If these are not lined-up in certain manner, then the mast tube itself has to be stronger to resist extra bending loads resulting from 'out-of-direct-alignment of the staying configuration. And if your mast is made of wood (likely for that boat), and desired NOT to be 'bendy' as most in those days were, ....then you need to build it heavier. And likely of a larger sectional shape, ....which would have been detrimental to the smaller mainsail's performance,... and a real drag factor up above the head of the mainsail (bare mast section).

Furthermore, likely that mast section was NOT of a more aerodynamic shape that we get with modern materials, but probably a rectangular section characteristic of wooden mast of that era.
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  #1098  
Old 02-27-2017, 08:45 PM
sharpii2 sharpii2 is offline
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Quote:
Originally Posted by brian eiland View Post
Let me ask you a question. Assume an analogous force-beam loading configuration.

Lay that mast (beam) out horizontally as a cantilevered beam with one end stuck in a wall (the deck). Now pull upwards at the tip just as the forestay does. And then in an analogous situation load some distributed weights onto the beam (outwardly from the wall) just as the mainlsail pulls on the mast tube as it rises from the deck.

Now ask yourself whether that beam (mast section on the horizontal) with the those extra weights has to be stronger than one with no added weights (no mainsail)??


Now 'point loading' of the mast tube can be a different situation (where most of the loading is by a single or multiple forestays and backstays). If these are not lined-up in certain manner, then the mast tube itself has to be stronger to resist extra bending loads resulting from 'out-of-direct-alignment of the staying configuration. And if your mast is made of wood (likely for that boat), and desired NOT to be 'bendy' as most in those days were, ....then you need to build it heavier. And likely of a larger sectional shape, ....which would have been detrimental to the smaller mainsail's performance,... and a real drag factor up above the head of the mainsail (bare mast section).

Furthermore, likely that mast section was NOT of a more aerodynamic shape that we get with modern materials, but probably a rectangular section characteristic of wooden mast of that era.
A better analogy would be to stand the mast up in a warehouse, put a huge weight on top, then run a bunch of strings, spaced evenly apart, along its length, to to the walls of the this warehouse. These strings would only be oriented for and aft. Along the side of this mast would be the usual set of shrouds and spreaders.

Basically, the way I see it, is the sail cloth prevents the mast from buckling forward, as its attached to the boom and has some leech tension. So if the mast starts to bend, the sail flattens a bit until it can flatten no more. At this point, the mast is prevented from buckling further in that direction.

The lift that the sail cloth provides arguably helps prevent the mast from buckling aft. But the main reason it doesn't buckle aft is because it is encouraged to buckle forward a bit, in the first place, and once buckling in one direction, it is very unlikely to buckle in the other direction.

The thing about buckling is it takes a relative weak force, perpendicular from it, to stop it in its early stages.

With a jib only, or a large jib and a very small main, The mast must be prevented from buckling at all. Hence it needs sections that are longer than normal, if not deeper too. So the mast begins to resemble a stove pipe, or wing. One possible solution is to run a second set of double lower shrouds up to the second set of spreaders, even if they have to attach to the same chain plates as the original set does.

It is for this reason, IMHO, that mast aft and jib only rigs are never as structurally efficient as fractional ones are.

Structural inefficiency usually means greater weight for the same SA. And this is absolutely fatal in competitive racing, except in situations where the CE of the rig must absolutely be moved aft.
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  #1099  
Old 02-28-2017, 03:05 PM
CT249 CT249 is offline
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/\ You nailed it, Sharpii.

Brian, many racing masts in the era were pear shaped; see Uffa Fox's books. Others were oval shaped with heavily rounded edges. And to repeat myself, if the weight of the mast was such a problem with Atrocia, why did the boat perform well with the same mast in a conventional rig?
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  #1100  
Old 02-28-2017, 04:27 PM
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Richard Woods Richard Woods is offline
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Quote:
Originally Posted by CT249 View Post
It's been explicitly said by people like Stearns since the '70s that a mainsail forms part of the structural support of a mast.
Long before that in fact. I remember being told in the 1960's that the OK mast needed the support of the sail, else it would break (I knew the worlds top wood OK mast maker and also one of the worlds best OK hull builders at that time)

Richard Woods
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  #1101  
Old 02-28-2017, 11:14 PM
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brian eiland brian eiland is offline
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Before I proceed with this current question, I would ask either of you 2 gentleman if these were 'purposeful bendy mast' utilized in that wooden mast era we are talking about??
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  #1102  
Old 03-01-2017, 06:17 AM
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brian eiland brian eiland is offline
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Here is a few photos of another 6-meter of that era, and I am guessing we can assume Atrocia's mast was stayed somewhat similar
http://www.6mrnorthamerica.com/clytie2.html

Interestingly I also found this
http://www.6mrnorthamerica.com/noreg.html
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The first race for the Scandinavian Gold Cup started the very next day. The rules for the Cup award the Cup to the first boat to win three races. After the first three races, boats which have not won a race are eliminated. The first two races were won by Merenneito and May Be respectively. May Be skippered by Sven Salen startled the fleet by "flattening down her reaching balooner" and going from sixth to first in one leg. This was the first time the genoa jib had been seen in American racing.
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  #1103  
Old 03-01-2017, 06:33 AM
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brian eiland brian eiland is offline
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Bendy Mast on early 6 meters

Seriously doubt it. I just looked thru a whole lot of 6 Meter photos, etc on this PDF and didn't find any
http://www.6metre.ch/docs/isma/2014/...wsletter16.pdf

I did find an interesting section of wood mast starting at about page 46.

Last edited by brian eiland : 03-01-2017 at 08:50 PM. Reason: spelling
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  #1104  
Old 03-01-2017, 05:08 PM
CT249 CT249 is offline
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Originally Posted by brian eiland View Post
Before I proceed with this current question, I would ask either of you 2 gentleman if these were 'purposeful bendy mast' utilized in that wooden mast era we are talking about??
No, Sixes were probably not bending their masts as we do at that time.
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