single spreader rig

[brm3]

I would like to know if anyone might have the answer to a question related to the location of a single spreader rig. More like does anyone know the ratio as to figure out proper placement of the said spreader? Thanks

[brittlee]

this is very nice and easy forum

[Ian McColgin]

So many "it depends" here. My old Alden schooner had the main spreaders about 5/8 up but the fore spreaders were more like 4/5 up. Both hollow round wooden masts keel stepped, Double headsail rigs have different loads, as to gaff rigs. Solid or hollow wood, round or oval or box section, aluminum, carbon, deck versus keel stepped . . . And all that's before we look at sail area, porportions, hull's power and heeling moment . . .

One really fun thing is to talk to a good marine engineer who has attempted to rethink the stay locations and scantlings on an L Francis Herreshoff rig. Dude was cagey, to say the least.

If it's not a large rig and you've over-built anyway and especially if you don't like paying for someone to figure it out correctly, put the spreaders somewhere between 5/8 and 2/3 up or, if a gaff rig, just above the unreefed throat, and tell the world you don't need no stinking naval architect.

G'luck

[Brion Toss]

Hi,
Spreader location is partly about unsupported length (Euler), and partly about staying angle (Pythagoras). On gaffers, the spreaders are crowded up to make room for the throat of the gaff (unless it is on a track), This makes for a very long unsupported length below the spreaders; fortunately gaffers tend to have less compression load that Bermudian rigs, but they still need relatively stiff, heavy masts to prevent their being too, um, lively. The spreaders on Ian's schooner were almost certainly placed there with regard to a gaff rig, and you will even see such a placement on schooners that were long ago converted to Bermudian or stays'l.
If you have a standard Bermudian rig, the rule of thumb for single-spreaders is to have them about 55% of the distance above deck. This makes for a suitably stiff lower section, without the need for ridiculously long spreaders. If the mast is designed with this in mind, and you crowd the spreaders up even a little bit, you'll be vulnerable to buckling.
So, what kind of rig is this?
Fair leads,
Brion Toss

[brm3]

Bermuda and thanks! Funny enough found a thread on sa that quotes Bob Perry as saying 54%. It's nice to see every ones on the same page and a kudos to you! Thanks again,