Sailboat standing rigging question
Discussion
I’ve been searching high and low trying to find an answer but all the articles I have found do not address the issue.
For clarity this is for a radio control model (1.7m long with 1.9m mast) but I believe the science will be the same. The drawings for the model don’t answer the questions either.
So, I have a deck stepped mast. Cap shrouds with spreaders, one set of lower shrouds, forestay & backstay. I have chainplates with multiple holes horizontally. The mast will be raked back about 50mm.
Now the questions.
• Should the cap shrouds attach to the chainplates in line with the mast base or in line with the (raked) mast top?
• Should the lower shrouds attach at the same place (or close)?
o If they should attach away from the cap shrouds should that be fore or aft?
o Or should I have 2 sets of lower shrouds and attach one each side of the cap shroud?
I’ve been finding plenty about tensioning rigging which will apply, but not with the same figures, but it all assumes the yacht builder put the chainplates in the right place all along.
Thanks in anticipation.
Steve
For clarity this is for a radio control model (1.7m long with 1.9m mast) but I believe the science will be the same. The drawings for the model don’t answer the questions either.
So, I have a deck stepped mast. Cap shrouds with spreaders, one set of lower shrouds, forestay & backstay. I have chainplates with multiple holes horizontally. The mast will be raked back about 50mm.
Now the questions.
• Should the cap shrouds attach to the chainplates in line with the mast base or in line with the (raked) mast top?
• Should the lower shrouds attach at the same place (or close)?
o If they should attach away from the cap shrouds should that be fore or aft?
o Or should I have 2 sets of lower shrouds and attach one each side of the cap shroud?
I’ve been finding plenty about tensioning rigging which will apply, but not with the same figures, but it all assumes the yacht builder put the chainplates in the right place all along.
Thanks in anticipation.
Steve
Short answer, any of those options can be found on various rigs over the years.
Longer answer.
Having the main shrouds in line with the mast foot allows the shrouds and spreaders to keep the mast straight side-to-side, while fore/aft bend is controlled by lower shrouds/checks stays/running backstays/inner forestay. Backstay takes the main forward drive of the rig.
A dinghy rig will have the shrouds significantly back from the mast foot, spreaders angled back to control mast bend, no backstay.
A typical small yacht like mine is halfway in between, there is a backstay, but it is sharing the forward drive with the shrouds which are significantly behind the mast foot. The backstay is used to control mast bend. That's with 'fractional rig' where the forestay and jib go about 3/4 of the way up the mast.
The spreaders are angled, the lower shrouds go to the same chainplates as the main shrouds.
An older style small yacht with masthead rig might have in-line shrouds and spreaders, with fore-aft bend control by fore/aft pairs of lower shrouds.
On a model, you probably have a stronger mast proportionally, with a yacht, it's a balance of more complex rigging allowing a lighter/slimmer mast, and also adjustable bend while sailing. On bigger boats, we're also concerned about the rig 'pumping' as we go over waves.
We also have to consider the effect of spinnakers and spinnaker poles trying to bend the mast.
How far back the shrouds are dictates how far you can let the main out downwind, this probably matters more for a model?
Raking the masthead back behind the shroud base is often done even in dinghies with no backstay.
Longer answer.
Having the main shrouds in line with the mast foot allows the shrouds and spreaders to keep the mast straight side-to-side, while fore/aft bend is controlled by lower shrouds/checks stays/running backstays/inner forestay. Backstay takes the main forward drive of the rig.
A dinghy rig will have the shrouds significantly back from the mast foot, spreaders angled back to control mast bend, no backstay.
A typical small yacht like mine is halfway in between, there is a backstay, but it is sharing the forward drive with the shrouds which are significantly behind the mast foot. The backstay is used to control mast bend. That's with 'fractional rig' where the forestay and jib go about 3/4 of the way up the mast.
The spreaders are angled, the lower shrouds go to the same chainplates as the main shrouds.
An older style small yacht with masthead rig might have in-line shrouds and spreaders, with fore-aft bend control by fore/aft pairs of lower shrouds.
On a model, you probably have a stronger mast proportionally, with a yacht, it's a balance of more complex rigging allowing a lighter/slimmer mast, and also adjustable bend while sailing. On bigger boats, we're also concerned about the rig 'pumping' as we go over waves.
We also have to consider the effect of spinnakers and spinnaker poles trying to bend the mast.
How far back the shrouds are dictates how far you can let the main out downwind, this probably matters more for a model?
Raking the masthead back behind the shroud base is often done even in dinghies with no backstay.
Steve_D said:
I’ve been searching high and low trying to find an answer but all the articles I have found do not address the issue.
For clarity this is for a radio control model (1.7m long with 1.9m mast) but I believe the science will be the same. The drawings for the model don’t answer the questions either.
So, I have a deck stepped mast. Cap shrouds with spreaders, one set of lower shrouds, forestay & backstay. I have chainplates with multiple holes horizontally. The mast will be raked back about 50mm.
Now the questions.
• Should the cap shrouds attach to the chainplates in line with the mast base or in line with the (raked) mast top?
• Should the lower shrouds attach at the same place (or close)?
o If they should attach away from the cap shrouds should that be fore or aft?
o Or should I have 2 sets of lower shrouds and attach one each side of the cap shroud?
I’ve been finding plenty about tensioning rigging which will apply, but not with the same figures, but it all assumes the yacht builder put the chainplates in the right place all along.
Thanks in anticipation.
Steve
On my boat - 1980 vintage Westerly, the cap shrouds attach in line with mast base and I have 2 sets of lowers from below the spreaders, set fore and set aft, both by about 2' from the cap shroud. That's my main mast, mizzen has wire going left right and chelsea..For clarity this is for a radio control model (1.7m long with 1.9m mast) but I believe the science will be the same. The drawings for the model don’t answer the questions either.
So, I have a deck stepped mast. Cap shrouds with spreaders, one set of lower shrouds, forestay & backstay. I have chainplates with multiple holes horizontally. The mast will be raked back about 50mm.
Now the questions.
• Should the cap shrouds attach to the chainplates in line with the mast base or in line with the (raked) mast top?
• Should the lower shrouds attach at the same place (or close)?
o If they should attach away from the cap shrouds should that be fore or aft?
o Or should I have 2 sets of lower shrouds and attach one each side of the cap shroud?
I’ve been finding plenty about tensioning rigging which will apply, but not with the same figures, but it all assumes the yacht builder put the chainplates in the right place all along.
Thanks in anticipation.
Steve
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