Shroud Tension

[fredanderson2000]

I recently took my 2013 MH40 to my local rigger in Solomons, MD to tighten the shrouds. He tightened them using the Selden recommended tensions (20% of the breaking strength). Hunter does not have any recommendation for the tightness, but instead says to tighten the shrouds about half-way on the turnbuckles and then go for a sail in 15 knots wind and tighten the cap shrouds until it feels tight enough (making both sides even). I should also add that the lowers were tightened to 20% of the breaking strength

When the boat was delivered to the rigger, the cap shroud turnbuckles were about 50% tight (the tension was barely registering on his tension scale), after I got the boat back they have about 5% left on tightness. My last sail on the boat was in 15-20 knots (after the shrouds were tightened). The boat felt solid and quite stiff. She sailed well and could point better than 40 degrees. About mid-day the winds were a pleasant 15 knots on a beam reach. There were no issues or concerns with the shrouds being tight enough.

Now that being said, there are some issues that have come up:
1. The forward Head door sticks.
2. The forward cabin door sticks.
3. The forward port portlight leaks.
4. Thee are 2 small cracks in the forward deck between the cabin and Anchor locker.
There is not any visible deformation of the cabin top or decks. All the floorboards fit nicely and the hatches fit well.

The questions I have are:
What is the correct tension of this B&R rig?
and
Should tightening the cap shrouds cause any of the 4 issues that I am experiencing?

 

[splax]

Well, it looks like a duck...

Should tightening the cap shrouds cause any of the 4 issues that I am experiencing? ___YES!

Your visible deformation of the cabin top or decks...-->
1. The forward Head door sticks.
2. The forward cabin door sticks.
3. The forward port portlight leaks.
4. There are 2 small cracks in the forward deck between the cabin and Anchor locker.

Your boat is a bundle of balanced forces. The stays are pulling the deck to the mast which in turn is pushing the keel away from the deck. Where you are I would call over to the guys at the Maryland Marina and ask who they recommend. I would back the tensions down about 30% and see if the issues go away and if the boat moves well under sail.

 

[fredanderson2000]

Should tightening the cap shrouds cause any of the 4 issues that I am experiencing? ___YES!

Your visible deformation of the cabin top or decks...-->
1. The forward Head door sticks.
2. The forward cabin door sticks.
3. The forward port portlight leaks.
4. There are 2 small cracks in the forward deck between the cabin and Anchor locker.

Your boat is a bundle of balanced forces. The stays are pulling the deck to the mast which in turn is pushing the keel away from the deck. Where you are I would call over to the guys at the Maryland Marina and ask who they recommend. I would back the tensions down about 30% and see if the issues go away and if the boat moves well under sail.

That was my first thought, but Hunter has not been quick on providing any recommended tension for the cap shrouds. I do not want to start backing off the turnbuckles until I get that information. The Hunter manual includes their process of tightening the shrouds (Start with turnbuckles half tight and sail in 15 knot winds and tighten the slack out of each side until they appear to be tight). Hunter also includes the Selden Manual that gives non-subjective tension information as a starting point. Since there are no backstays to keep the mast from falling forward in a blow or accidental jibe, I would believe that there is a minimum tension that is a starting point, rather than some subjective point. By the way, there has been 2 or 3 lost masts on Hunters on the Chesapeake this year (I have not heard how many Catalinas or Beneteaus lost theirs). I cannot be certain why, but it may have something to do with the shroud tension. When I asked the rigger about other Hunters, he mentioned that they just tuned one that did not register on the tension gauge - and it was a new boat.
I inquired about this on my first Hunter (when Eddie responded from the customer service desk), and got the Selden specification - the pages from the Selden manual. The windy season is starting on the bay and I would like to have confidence that the mast is not going to fall off in a spirited 20 knot gust.
If the boat is designed for a lower tension than the recommendation from Selden, then Hunter should have some engineering data that correlates to a recommended tension, we already know that Selden does.

 

[Jackdaw]

Your boats has no backstay. Your caps are holding up your mast!

For sure do the 20%. And make sure the mast has correct prebend, in particular if you use a spinnaker.

As noted rigging loads get transferred to the hull. I've heard of hull defection fore-aft due to very aggressive backstay application, but never from correctly setting base stay tune. Hum.

 

[slazerow]

It would be nice if someone with a Loos gauge and Hunter B&R rig would reply to this thread.

 

[Mark48]

I have the specs for a H 34 and will try to attach or paste. Ok, I am clueless on attaching another document, send me a PM and I will respond, but here is what I have Lower stay 9/32 at 36/47 on loos scale, Middle and upper 1/4 at 40/41, forestay at 9/32 is 46/47, if you have a backstay use the same numbers based on wire size.

 

[splax]

I have a Loos gauge and a B&R rig. Makes no difference to the situation. He needs to hear someone with the same boat.

 

[fredanderson2000]

Actually, I am hoping that a Hunter technician would jump in with the Hunter recommended tension. Anything else would be subjective to wether the rig feels tight.

 

[fredanderson2000]

The dealer came back with the Hunter recommendations (based on the MH37):
RDs (Reverse Diagonals) 12-15% breaking strength,
D1 (Lowers) 15% breaking strength,
V1 (Cap Shrouds) 20% breaking strength.

I will have to have the rig checked again.

The MH37 is very similar in size and construction to my MH40, but with a single head.

I must admit that I am a little disappoint with the Hunter customer service. I delt with Hunter customer service (Eddie Breeden) less than a year ago and Hunter had answers to the difficult questions (autopilot, davits and factory visit) back to within the same day. Eddie has since moved on and customer service does not seem to be as good as it should be.
This issue about shroud tension is a serious one that is at the root of safe sailing. There have been more than one Hunter mast down on Chesapeake this past summer according to my local rigger. He was intent to make sure my rig was tight and followed the Selden procedure and tuned to the Selden specifications. He advised that this be done unless Hunter had something different. After the tune was done, we sailed in winds 15-20 with gusts into the 25 knot range in all points of sail. I can only imagine my mast falling to the bottom of the bay as I sail up the bay wing-on-wing in a 20+ knot breeze. My question was recently answered, but after 2 months (that is the entire sailing season for some folks). Yesterday I was able to sail in the 25 knot breeze confident that my mast was tight to the hull.

 

[slazerow]

The Loos gauges are calibrated for stainless 302 shrouds whereas I thought Hunter used 316 stainless (based on internet search), which has a lower breaking point. Can someone confirm?

 

[Jackdaw]

The Loos gauges are calibrated for stainless 302 shrouds whereas I thought Hunter used 316 stainless (based on internet search), which has a lower breaking point. Can someone confirm?

I've talked to Loos VP of Engineering about this. They still read (as a percentage of breaking strength) correctly. Had they read in absolute values it would be wrong.

He's an interesting guy. Never set foot on a sailboat.

 

[uncledom]

I recently took my 2013 MH40 to my local rigger in Solomons, MD to tighten the shrouds. He tightened them using the Selden recommended tensions (20% of the breaking strength). Hunter does not have any recommendation for the tightness, but instead says to tighten the shrouds about half-way on the turnbuckles and then go for a sail in 15 knots wind and tighten the cap shrouds until it feels tight enough (making both sides even). I should also add that the lowers were tightened to 20% of the breaking strength When the boat was delivered to the rigger, the cap shroud turnbuckles were about 50% tight (the tension was barely registering on his tension scale), after I got the boat back they have about 5% left on tightness. My last sail on the boat was in 15-20 knots (after the shrouds were tightened). The boat felt solid and quite stiff. She sailed well and could point better than 40 degrees. About mid-day the winds were a pleasant 15 knots on a beam reach. There were no issues or concerns with the shrouds being tight enough. Now that being said, there are some issues that have come up: 1. The forward Head door sticks. 2. The forward cabin door sticks. 3. The forward port portlight leaks. 4. Thee are 2 small cracks in the forward deck between the cabin and Anchor locker. There is not any visible deformation of the cabin top or decks. All the floorboards fit nicely and the hatches fit well. The questions I have are: What is the correct tension of this B&R rig? and Should tightening the cap shrouds cause any of the 4 issues that I am experiencing?

I would suggest talking to Seldon about the rig as they are the manufacturer of it and their engineers are the ones with the answers. I believe my Hunter manual on rig tuning is just excerpts from the Seldon manual which I also have. I would follow the Seldon manual if I were the one tuning it. Good luck.

 

[woodster]

The Loos gauges are calibrated for stainless 302 shrouds whereas I thought Hunter used 316 stainless (based on internet search), which has a lower breaking point. Can someone confirm?

the 304 ss will be stronger under the same load as it has a higher breaking strength......also as to the gauge tension they will be the same if comparing 1/4 304 to 1/4 316 on the gauge..tension is the measure of the act not the wire composition ...the 316 will over the long run loosen up sooner than the 304 because the stretch/elongation is greater under the same tension...but it is not a big deal to a coastal cruiser unless you have been battling a heavy storm for a good while ......most racers are constantly checking tension when readying for the next big race so as to have everything in good condition ...if you google the comparison of the two grades you will find a lot on this subject

 

[uncledom]

I recently took my 2013 MH40 to my local rigger in Solomons, MD to tighten the shrouds. He tightened them using the Selden recommended tensions (20% of the breaking strength). Hunter does not have any recommendation for the tightness, but instead says to tighten the shrouds about half-way on the turnbuckles and then go for a sail in 15 knots wind and tighten the cap shrouds until it feels tight enough (making both sides even). I should also add that the lowers were tightened to 20% of the breaking strength When the boat was delivered to the rigger, the cap shroud turnbuckles were about 50% tight (the tension was barely registering on his tension scale), after I got the boat back they have about 5% left on tightness. My last sail on the boat was in 15-20 knots (after the shrouds were tightened). The boat felt solid and quite stiff. She sailed well and could point better than 40 degrees. About mid-day the winds were a pleasant 15 knots on a beam reach. There were no issues or concerns with the shrouds being tight enough. Now that being said, there are some issues that have come up: 1. The forward Head door sticks. 2. The forward cabin door sticks. 3. The forward port portlight leaks. 4. Thee are 2 small cracks in the forward deck between the cabin and Anchor locker. There is not any visible deformation of the cabin top or decks. All the floorboards fit nicely and the hatches fit well. The questions I have are: What is the correct tension of this B&R rig? and Should tightening the cap shrouds cause any of the 4 issues that I am experiencing?

Fred, I have a 2006 Hunter 41 which is pretty similar. I went over something similar with Eddie Breeden a while back and the long and short of it is that the compression post should keep the mast load from distorting the deck and cause pressure on the forward cabin wall. That wall is not load bearing on my vessel and I would bank that it should not be load bearing on your vessel, that is a point I would verify with MH. I have a generic Seldon manual on my ipad which I can't seem to attach. It's available on the Seldon site.

 

[Jackdaw]

Fred, I have a 2006 Hunter 41 which is pretty similar. I went over something similar with Eddie Breeden a while back and the long and short of it is that the compression post should keep the mast load from distorting the deck and cause pressure on the forward cabin wall. That wall is not load bearing on my vessel and I would bank that it should not be load bearing on your vessel, that is a point I would verify with MH. I have a generic Seldon manual on my ipad which I can't seem to attach. It's available on the Seldon site.

Indeed.

A traditionally rigged sloop has the rig load brought to the hull via the chainplates and bulkheads, or even better by SS rods that tie the deck fitting to the bottom of the hull.

On boats where the rigging attached to the gunwales (like most modern B&R rigged Hunters), the boat relies on the hull inner grid and/or bulkheads to resist the force of the rig tension. Otherwise, the hull would want to start to fold closed like a taco.

If there is not a bulkhead at the point the shrouds attach to the hull, the grid system needs to extend to the point where the hull walls are vertical. If it does not, the hull will likely flex under the rig tension.

 

[uncledom]

Fred I would check into this very carefully. If the design of the MH 40 is such that the mast load is taken by the compression post and there should be no pressure on the bulkhead and your doors are suddenly sticking indicating pressure on the bulkhead then I would want to be sure there is no other under lying issue. I read a post by zigracer that might be relevant.
http://forums.hunter.sailboatowners.com/showthread.php?t=174805#

Here is the Seldon manual. It's generic but gives you an idea of how it all works. Grabs the hints and advice PDF.

http://www.seldenmast.com/en/technical_info/rigging_instructions.html