B&R Reverse Diagonal Tension

Discussion in 'Big Boats' started by Don Lucas, Apr 10, 2019. Add this thread to a FAQ

  1. Don Lucas

    Don Lucas

    Joined Jan 12, 2011
    802 posts, 38 likes
    Hunter 410
    US full time cruiser
    As background: I had my mast off a few months ago. None of the "on the ground" settings were changed on the Reverse Diagonals (RD1) etc. and the rig was put back on by the yard and outside riggers they forced me to use. Afterwards my V1 cap shrouds were tighter than they had been before the mast was removed (just by feel), and the lower diagonal shrouds D1 were lossener (based on how far the screws were screwed in). The prebend all looks good and smooth, but maybe more than before the mast was removed.

    I finally have gotten underway and sailed in some high winds (all as been on a port tach). On a close reach/reach I noticed my port lower reverse diagonal (RD1) is slack. Everything else looks and feels good and all leeward shroud are tight etc. As I can't think of any reason anything on the windward side of the rig should be loose I tightened a little. But it still is loose and I haven't been out again.

    Thinking it through, RD1 is used to set the prebend on the mast before setting the mast. That is the last mention of the RDs in the instructions. The only thing I can think of that would cause RD1 to loosen under sail would be for the bend to increase, as if the headsail tried to reduce the bend RD1 tension should increase instead of loosening. In the directions the cap shrouds (V1) get tensioned first to 15-20% breaking strength and it says this will increase prebend. Then you are to tension the "lower shrouds" (D1) to 15-20% which will pull the lower section of the mast back aft reducing prebend.

    So if my D1s are too loose it seems to make sense that the bend under sail could increase beyond that which was set on the ground using the RDs and that RD1 could become slack.

    So I'm back to my last thread question of:
    -how tight are your D1s?

    And now have a new question of:
    -do your windward RD1s get slack?
     


  2. Don Lucas

    Don Lucas

    Joined Jan 12, 2011
    802 posts, 38 likes
    Hunter 410
    US full time cruiser
    Haven't heard back from the local rigging company. So ordered a tension gauge and will just do it myself.
     


  3. Don Lucas

    Don Lucas

    Joined Jan 12, 2011
    802 posts, 38 likes
    Hunter 410
    US full time cruiser
    On the off chance someone reads this and is interested in the topic:
    - tightened my V1s up some more to bring them to 19% of breaking tension (they were ar 16% prior).
    - tightened the D1s up from the 9% the rigger left them to 19%
    - this also seemed to tighten up the RD1s as they resisted the bend being reduced as the D1s were tightened up

    And I'm the proud owner of a $280 rigging tension gauge, which pretty much guarantees that the rigging will never need adjustment again :)
     


    Last edited: Apr 16, 2019
  4. DayDreamer41

    DayDreamer41

    Joined Oct 29, 2016
    1,346 posts, 674 likes
    Hunter 41 DS
    Un Port Huron
    "And I'm the proud owner of a $280 rigging tension gauge, which pretty guarantees that the rigging will never need adjustment again :)"

    So how much you want for it........
     


  5. Don Lucas

    Don Lucas

    Joined Jan 12, 2011
    802 posts, 38 likes
    Hunter 410
    US full time cruiser
    I'm going to hold on to it till I've gotten a few hard sail days in (I'm a cruiser so that might take weeks). Make me an serious offer for consideration.
     


  6. Will Gilmore

    Will Gilmore

    Joined Oct 19, 2017
    4,806 posts, 2,803 likes
    O'Day 19
    US Littleton, NH
    Congratulation Don. I'm glad everything worked out for you.
    It looks like your V1s, along with most of the rest of your rig, were undertight, afterall. How does the prebend look now, compared to before? You said previously, that the prebend looked like it was more than the last time you had it tuned. Did your adjustments change that?

    -Will (Dragonfly)
     


  7. Don Lucas

    Don Lucas

    Joined Jan 12, 2011
    802 posts, 38 likes
    Hunter 410
    US full time cruiser
    tightening the D1s (you know my original question) took out a lot of mast bend

    One of the overall lessons was: the rigger was the first time a "professional" has worked on my boat in the 9 years I've owned it. All they did was get paid to screw up my boat!
     


  8. Will Gilmore

    Will Gilmore

    Joined Oct 19, 2017
    4,806 posts, 2,803 likes
    O'Day 19
    US Littleton, NH
    That is often my experience with professionals. In my career as an independent professional, I use to tell people, "I charge for my mistakes, I just don't charge to fix them. "

    -Will (Dragonfly)
     


    Last edited: Apr 19, 2019
  9. Don Lucas

    Don Lucas

    Joined Jan 12, 2011
    802 posts, 38 likes
    Hunter 410
    US full time cruiser
  10. Don Lucas

    Don Lucas

    Joined Jan 12, 2011
    802 posts, 38 likes
    Hunter 410
    US full time cruiser
    Have spent a few 24+ hour sails sailing hard since adjusting my rig to the tensions as noted in the thread. If you do the same your rig is going to be just fine and there will be no need to adjust under sail as the leeward cables are going to remain pretty tight.

    It's as simple as that and probably well worth it to an owner to read up on, buy a good tension gauge, and do it themselves as it is to risk letting the "pro" learn on your boat. I told my "pro" what I had learned and they admitted they they didn't know (used different words that equaled this).
     


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  11. DayDreamer41

    DayDreamer41

    Joined Oct 29, 2016
    1,346 posts, 674 likes
    Hunter 41 DS
    Un Port Huron
    @Don Lucas I did buy a gauge, figured that it wouldn't be such a bad thing to have, I am sure it will get put to use around the club as well as for each springs tune up.
    Anyway this past weekend the sail loft delivered my new sails and in talking with them they suggested I back both the V1's and the D1's off (especially the D1's) check that the mast is in column, which it is, then set my V1's to 18%, then I set the D1's to 18% measured the prebend in the mast and it is now a nice smooth evenly distributed 2" at the midpoint between the mast head the the goose neck (was closer to 5" before adjustments). Once this was done I went back and looked at the V1's tension, they had dropped back to about 12%?? which is opposite to what I thought would happen. But the mast is in column and has what is prescribed for prebend on a furling rig so the next thing is to go out and sail it and see if everything stays taunt.
     


  12. Bill19233

    Bill19233

    Joined Jan 22, 2008
    457 posts, 358 likes
    Hunter 340
    US Baytown TX
    Last race I noticed the windward RD1's were going slack when close hauled on both points of sail. Local rigger that I trust and is familiar with B&R rigs is going to tune and inspect this week, it's been three years. He thought I was confused and that the leeward ones were going slack and said that's normal to see a little slack. Had to show him this 30 second video that it is the windwards. I don't think he's seen the windward RD1's loose before.

    You have to watch real close, but you can see it flop around if you're watching in 1080. I'll update with whatever they tell me they found and adjusted. They're tight as can be when sitting at the dock.
     


    Last edited: May 21, 2019
  13. Don Lucas

    Don Lucas

    Joined Jan 12, 2011
    802 posts, 38 likes
    Hunter 410
    US full time cruiser
    When I did mine, tightening the D1s didn't change the V1s tension at all
     


  14. RoyS

    RoyS

    Joined Jun 3, 2012
    526 posts, 205 likes
    Hunter 33
    US Bay Pointe, Quincy
    You are correct. You will never need it it again and it will not fit in your tool box either. Do the right thing and toss it over the side.
     


  15. Don Lucas

    Don Lucas

    Joined Jan 12, 2011
    802 posts, 38 likes
    Hunter 410
    US full time cruiser
    sold it for the $220 I posted
     


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