Rigging with swept back spreaders

[gwoiler]

Hello. I have a 1999 Beneteau Oceanis 40cc with swept back spreaders and in-mast furling. The mast has too much bend. I have researched and followed the best I can, but I do not find any information how to tension the small stays that go from the outboard of the lower spreader to the inboard of the second spreader. I loosened everything up including backstays. I tightened up the main shrouds and found the mast center. I did not tighten them to a rock. I then tightened the back shrouds paying attention to mast straightness. I got them close to a rock. I made fine adjustments to the main shrouds. I then tensioned the forward shrouds but looser then the rear. I put some tension on the backstays but they are much less tension. The resulting bend was much less then previous. I went for a sail and the leeward side had a loose upper short shroud between the spreaders. I could see it flapping in the breeze. The leeward front shroud was a little looser and the main and rear shrouds were unchanged.


What is the procedure for tensioning the short stay between the spreaders? If possible, I wish there to be no bend in the mast and these short stays must have an effect not only on mast straightness, but also holding out the bend.



Thanks for your help!

[wingssail]

Originally Posted by gwoiler

Hello. I have a 1999 Beneteau Oceanis 40cc with swept back spreaders and in-mast furling. The mast has too much bend. I have researched and followed the best I can, but I do not find any information how to tension the small stays that go from the outboard of the lower spreader to the inboard of the second spreader. I loosened everything up including backstays. I tightened up the main shrouds and found the mast center. I did not tighten them to a rock. I then tightened the back shrouds paying attention to mast straightness. I got them close to a rock. I made fine adjustments to the main shrouds. I then tensioned the forward shrouds but looser then the rear. I put some tension on the backstays but they are much less tension. The resulting bend was much less then previous. I went for a sail and the leeward side had a loose upper short shroud between the spreaders. I could see it flapping in the breeze. The leeward front shroud was a little looser and the main and rear shrouds were unchanged.

What is the procedure for tensioning the short stay between the spreaders? If possible, I wish there to be no bend in the mast and these short stays must have an effect not only on mast straightness, but also holding out the bend.

Thanks for your help!

I assume you are talking about fore and aft mast bend which has impact on the in-mast roller furling.

The primary purpose of the short shrouds going to the mast from the first spreader (called D-2) is to prevent the mast at the second spreader from sagging to leeward (thwartship mast bend). It is important for the mast to be straight and in column from side to side. You determine if this is so by sighting up the mast with your eyeball right at the mast track on the aft side of the mast, when the boat is heeled over under sail. The D-2's will also prevent fore and aft mast bend at the second spreader by keeping the mast at that point from moving forward. To do so they must be firm, not rock hard.

To adjust the D-2 shrouds most riggers do so by going aloft while under sail and they take the slackness out of the leeward D-2, then tacking and doing the same to the other side. The key is to tighten enough so that the mast does not sag off to leeward at the point where the shroud attaches when you have tacked. You may hear that you could do it at the dock by heeling the boat with halyards to the next door dock and taking up some (this is, in my opinion, slightly dodgy, I won't do it, the loads can get very high, but it is done.)

I always tighten leeward shrouds just enough to keep them from flopping about when you are sailing in about 12 knots of breeze. And that is when you want to be sighting up the mast to evaluate the mast bend. More than that do it very gradually, and best with a rigger present to assist.

[s/v Jedi]

Before tensioning the capshrouds, tension the lowers and the intermediates which will limit mast bend.

Use calipers to measure distance between threaded end in the turnbuckle and write these down for future reference.

[chrisr]

if you do not understand your rigging, i'd suggest that you engage a local rigger to do it for you.

watch him/her carefully, ask questions and learn. in time you'll be able to do it yourself

it's a mixture of science and art

cheers,

[gwoiler]

Originally Posted by wingssail

I assume you are talking about fore and aft mast bend which has impact on the in-mast roller furling.

The primary purpose of the short shrouds going to the mast from the first spreader (called D-2) is to prevent the mast at the second spreader from sagging to leeward (thwartship mast bend). It is important for the mast to be straight and in column from side to side. You determine if this is so by sighting up the mast with your eyeball right at the mast track on the aft side of the mast, when the boat is heeled over under sail. The D-2's will also prevent fore and aft mast bend at the second spreader by keeping the mast at that point from moving forward. To do so they must be firm, not rock hard.

To adjust the D-2 shrouds most riggers do so by going aloft while under sail and they take the slackness out of the leeward D-2, then tacking and doing the same to the other side. The key is to tighten enough so that the mast does not sag off to leeward at the point where the shroud attaches when you have tacked. You may hear that you could do it at the dock by heeling the boat with halyards to the next door dock and taking up some (this is, in my opinion, slightly dodgy, I won't do it, the loads can get very high, but it is done.)

I always tighten leeward shrouds just enough to keep them from flopping about when you are sailing in about 12 knots of breeze. And that is when you want to be sighting up the mast to evaluate the mast bend. More than that do it very gradually, and best with a rigger present to assist.

Thank you for confirming what I was thinking. After loosening all shrouds and then tightening in the correct sequence, the D2's were flopping in the wind even when the main shrouds were tight but not all the way. Then while test sailing, one side was flopping on the leeward side on tack. Bringing the main shrouds up to proper tension bends the mast more because I believe these D2's are not doing their job.

[gwoiler]

Originally Posted by chrisr

if you do not understand your rigging, i'd suggest that you engage a local rigger to do it for you.

watch him/her carefully, ask questions and learn. in time you'll be able to do it yourself

it's a mixture of science and art

cheers,

I am understanding it more and more, yes. The problem is, a fellow sailor passing though, that was to rigger school, way over tightened my back stays as if I did not have swept back spreaders. He introduced so much mast bend that I did not notice that day. He had a tension gauge and got them really tight! But this sailboat does not use highly tensioned backstays.

[s/v Jedi]

I recommend this book from Igor Dedekam. You can download it.

It has specific instructions for your type of rig.

https://www.amazon.com/Illustrated-S.../dp/1898660670

[ItDepends]

Originally Posted by s/v Jedi

I recommend this book from Igor Dedekam. You can download it.

It has specific instructions for your type of rig.

https://www.amazon.com/Illustrated-S.../dp/1898660670

Another vote for this book... It is the best. If you are doing your own rigging adjustment and you are not following a procedure written by an expert you are going to make a mess. ESPECIALLY with a complex setup like yours.

[Joli]

Swept spreaders can make tuning difficult because as you bring on cap tension you introduce bow. To prevent this you'll have to tension the d1's first. Selden has a very good tuning guide that should get you close.

HINTS AND ADVICE https://www.seldenmast.com/files/1571039872/595-540-E.pdf

[gwoiler]

Originally Posted by Joli

Swept spreaders can make tuning difficult because as you bring on cap tension you introduce bow. To prevent this you'll have to tension the d1's first. Selden has a very good tuning guide that should get you close.

HINTS AND ADVICE https://www.seldenmast.com/files/157.../595-540-E.pdf

Thank you! I have red this and everything else I can find on swept back spreaders. Yes, the D1's are key and... the D2's on this rig are too loose because I have seen them flapping in the breeze on the leeward side. They help minimize the bend also. So... Sunday I will take it all loose and do it again, this time in a better order! Thanks

[FabioC]

Your mast manufacturer (not Beneteau) should have a rig tuning guide of some sort. It may be not incredibly detailed, or not necessarily specific to your mast, but would nevertheless apply to swept back spreader mast with the same number of spreaders and the same shroud configuration as yours.

The guide will not tell you everything, but it will give you a good starting point and most importantly a few important rules of thumb, like the max tension of a given shroud (even a very competent rigger may not know the precise limits for your specific mast)

If you cannot find it online, you should call the mast manufacturer and give them the numbers at the bottom of the mast, so they can identify which mast you have. They very likely have some form of guide, and they are also usually forthcoming with information.

For example, Selden has one for every type of mast they do. You can find it online, but if you call them, you get additional useful info. Then, you probably should still hire a rigger, but having all the info will help the rigger as well.

[gwoiler]

Originally Posted by FabioC

Your mast manufacturer (not Beneteau) should have a rig tuning guide of some sort. It may be not incredibly detailed, or not necessarily specific to your mast, but would nevertheless apply to swept back spreader mast with the same number of spreaders and the same shroud configuration as yours.

The guide will not tell you everything, but it will give you a good starting point and most importantly a few important rules of thumb, like the max tension of a given shroud (even a very competent rigger may not know the precise limits for your specific mast)

If you cannot find it online, you should call the mast manufacturer and give them the numbers at the bottom of the mast, so they can identify which mast you have. They very likely have some form of guide, and they are also usually forthcoming with information.

For example, Selden has one for every type of mast they do. You can find it online, but if you call them, you get additional useful info. Then, you probably should still hire a rigger, but having all the info will help the rigger as well.

Thank you for all this! The mast is by Selden. I have gotten all they have published. I might call them next week, but have a better idea because I now understand the D2's better. Thank you again.

[Searles]

Two things to watch for ,one is don’t bend the boat ,slacken the rig off tighten the top safety line ,hopefully wire to firm ,re set the rig until the top fence wire srarts to slacken ,that’s it,no sense bending the boat ,especially going to windward .the other thing is to remember that as the rig bends aft the looward rig will slacken ,this is because the distance from the mast head to the deck gets slightly shorter ,especially with swelt back spreaders .⛵️⚓️

[Apollo19.5]

Cranking up your main (cap) strouds first bends your mast. I think you are working back to front in order. Ds first, then caps. Is it a masthead or fractional rig?

[Joli]

Originally Posted by gwoiler

Thank you! I have red this and everything else I can find on swept back spreaders. Yes, the D1's are key and... the D2's on this rig are too loose because I have seen them flapping in the breeze on the leeward side. They help minimize the bend also. So... Sunday I will take it all loose and do it again, this time in a better order! Thanks

Does your rigging terminate at deck or do you have to go aloft to tension the d2's? The d1's will be on hard, the d2's not as much. Do you have access to a Loos Gage?