Mast ratios .... below vs above spreaders

Refueler

Refueler

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Standing at club rail looking at the boats here ... then looking across at my latest ... I could not avoid seeing the difference in mast ratio.

My mast has a much greater amount above spreaders than all the other boats there ....

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Mines - the red boat partially obscured by the Bav's black hood ...
 
Presumably you are ¾ rigged. If so, it looks normal to me. Your forestay tension is kept by the cap shrouds, which should be swept aft. Without teaching you to suck eggs, the cap shrouds should be set at 20% of the breaking strain of the wire rather than the 15% for a masthead rig. too much backstay tension will bend the mast as the upper section acts as a lever pivoting at the top of the forestay.
 
Looks like a typical old style single spreader 3/4 rig with a large mainsail and smaller foresail. The Bav has a 2 spreader 9/10ths rig so naturally each mast panel will be smaller.

Don't see many rigs like yours these days
 
I would see Nigel's rig as pretty ordinary for a fractional rig. ie very similar to my little TS fractional rig. It does seem to have an extreme of rig fraction. ie amount of mast above cap shrouds and fore stay. ie a 3/4 rig versus perhaps 7/8 rig for mine. It does mean a bigger main sail compared to jib. It also means much more mast bend under pressure of back stay that frees off the top of the main sail. As said the degree of aft of abeam the mast that the chain plates are set provides the support aft for the pull of the fore stay. The spreaders providing push forward against pull aft of intermediate shrouds.
So yes a fairly radical rig in terms of degrees where one might see a 2 spreader rig on a 38fter. Thing is when weather comes up you would reef main sail so in effect reduce the fraction considering that the main sail it self will provide much mast support.
So hopefully a well designed rig with no history of failure. Here is a link to a picture of Foundation 36 yachts used here for many years as one design racing yacht. No mast failures despite hard usage. FOUNDATION 36 - sailboatdata
Perhaps not so much unsupported top mast as yours but might give you an idea. ol'will
 
Its unusual as posted by other to see such rig today ...

As to mast bend etc. - she has 3 backstays .... so bend and forestay tension are directly controlled from cockpit ...

She has central to the masthead for bend ... and then backstay each side that goes to same mast point that forestay is attached - to alter forestay tension / curvature etc.

All three have winch / stoppers dedicated.

Its an interesting boat !!
 
I don't think that would have looked extreme in terms of 'fractional %' last century.

The running backstays are probably very important!
If the shrouds are pretty much in line with the mast, it makes a very adjustable rig.
Many boats that size or a bit bigger would have two sets of spreaders and intermediate shrouds, allowing a light mast section, and even more bend control, often using 'checkstays' from a sheave in the mast to part way up the running backstay.
 
Refueler said:
Its unusual as posted by other to see such rig today ...

As to mast bend etc. - she has 3 backstays .... so bend and forestay tension are directly controlled from cockpit ...

She has central to the masthead for bend ... and then backstay each side that goes to same mast point that forestay is attached - to alter forestay tension / curvature etc.

All three have winch / stoppers dedicated.

Its an interesting boat !!
Click to expand...
Sounds like you have a backstay and a pair of runners that attach at the top oif the forestay. One runner should be tensioned to support the rig as you probably do not have sufficient aft sweep on your spreaders. This photo shows clearly how much the spreaders are swept back on my ¾ rigged Westerly Fulmar and I have no runners.

IMG_3647 cropped 1000pix.jpg
 
The Running Backstays are tensioned / slacked depending on wind / tack etc. one or both depending on the action at time.

The main masthead backstay of course used when needed..... most of time tensioned and left.

The boat is 'dragging' me back into 'race mode' !! Have to brush up on various forgotten over the years ...
 
Nigel I suspect you will end up resenting those running back stays. With much tacking you will need a crew man to operate the running back stays . A friend had a 30fter with that rig (running back stays) and was constantly looking for ways to do away with them. My little boat had running back stays originally but I quickly threw them away as not needed. They can improve forestay sag. Another with a Farr 40 racer threw away the running back stays but did move the chain plates aft. Any way the critical dimension re doing away with running back stays is the dimension aft of abeam the mast base that the chain plates are mounted. If sufficientl;y aft of mast the cap shrouds will provide the support aft against the forstay pull. Unfortunately that means shrouds will foul the main sail on a run. (just live with that. The spreaders have to meet the cap shroud and in fact sweep further aft to provide push forward to the middle of the mast. (against the intermediate side stays.) It requires spreaders not just swept back but robust in that direction.
Anyway in ocean on long beats you will appreciate those running back stays. get ina tight spot of tacking you won't. ol'will
 
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