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B&R Rig Tension

Discussion in 'Big Boats' started by Don Lucas, Feb 16, 2019. Add this thread to a FAQ

  1. VanIslandGuy

    VanIslandGuy

    Joined Jan 12, 2016
    185 posts, 38 likes
    Hunter 410
    CA Ladysmith
    Hi Don,

    My old boat Bayfield 32c was cutter rigged. I used a loose gauge, tennis ball at the end of the main halyard, and a laser level, to get things set up nicely. It normally took about three or four sails before things were close to perfect. It was very simple without the diamond uppers like the B&R. Using the loose gauge was really helpful as it took a lot of guesswork out of wondering if the rig was too tight. Without it I'm sure I would have left things not tight enough.

    Now that I have the same boat as you, H410, I am way more gun shy with rigging adjustment. I've read the manual, and have stepped many masts, (used to operate the mast crane at our old yacht club), but it seems the B&R rig will be less forgiving to error. I will be getting a professional rigger who has worked on lots of these rigs to show me what to do, and record it all on my iPhone when the time comes to replace stays, or un-step the mast.
     


  2. Don Lucas

    Don Lucas

    Joined Jan 12, 2011
    762 posts, 21 likes
    Hunter 410
    US full time cruiser
    See that's part of my "issue". I had the mast and rig off the boat and then put back and had the "professional" rigger. Now the rigging is different that before so I figured I would do a crowdsourced approach and see if it was "common" . So far I don't think anyone has answered the question really on how their rigging is, which is how tight are their lower inner stay D1.
     


  3. DrJudyB

    DrJudyB

    Joined Jun 25, 2004
    279 posts, 189 likes
    Corsair F24 Mk1
    003 US San Francisco Bay, CA
    I believe the 410 was delivered with a Selden mast, but I could be wrong. Selden started supplying Hunter in the mid 1990s, iirc.

    Note that setting lengths/tension of all the shrouds Must be done in a certain sequence.

    First you must set the #1 and #2 reverse diagonal shrouds to the correct length to induce the prescribed amount of prebend. This is usually done on the dock, so you can reach the DR2's.

    Second: The mast is stepped and the cap shrouds are tensioned to 20% to provide lateral stability, and that induces additional prebend (because the spreader are swept aft 30 degrees).

    Third: you tighten the D1s to bring the prebend back to within the specified limit. 20% of breaking load is in the ballpark. But if the RDs and cap shrouds weren’t adjusted correctly to achieve the correct mast bend at the correct tension, adjusting the D1s to around 20% won’t compensate for the previous errors. .

    Fourth: The final tune is done on the water at 20degrees OD heel.you test the rig by sailing at 20 degrees of heel and adjust cap shrouds as needed under load.

    In step 3, Selden’s rigging instructions for tuning a B&R rig tell the owner to sthe D1s should initially be at about 20% of breaking load, and the pretend should be smooth between the gooseneck and masthead.

    Also, the prebend specs are defined as follows.

    If the mast is furling, prebend should not exceed 0.5% of the measurement from gooseneck to masthead. (Many sailmakers recommend a max of 2”or 0.5%, whichever is less, for a furling mast) For a non furling Selden B&R mast, use 1%.

    For a much better explanation than I have given, read the whole set of instructions starting page 53 at http://www.seldenmast.com/files/595-540-E.pdf .
     


    Last edited: Mar 5, 2019
    Will Gilmore likes this.
  4. DayDreamer41

    DayDreamer41

    Joined Oct 29, 2016
    1,232 posts, 609 likes
    Hunter 41 DS
    Un Port Huron
    @DrJudyB, I believe Don is looking for a reference to what others D1's are set to (loos gauge value) not instructions on how to get there, those have been stated several times throughout this thread.
     


  5. Scott B

    Scott B Moderator

    Joined Sep 20, 2006
    2,592 posts, 153 likes
    Hunter 33
    CA Georgian Bay, Ontario, Canada
    Where is that quote from? I've looked for that all thru the Selden info, but have not been able to find in-mast mentioned. I'm currently going through the same rigging issue on mine.
     


  6. DrJudyB

    DrJudyB

    Joined Jun 25, 2004
    279 posts, 189 likes
    Corsair F24 Mk1
    003 US San Francisco Bay, CA

    @Scott B
    That quote is from Selden tech support.
    I've been a Selden distributor (and sailmaker) for over a decade.

    Please note that 0.5% is the max prebend for a furling Selden mast. In practice, we generally prefer a little less than that for IMF mainsails. I advise people to limit prebend to the lesser of 0.5% or 2", because too much prebend increases the risk of jamming due to wrinkles.

    Judy Blumhorst
    Authorized Selden Distributor
     


  7. DrJudyB

    DrJudyB

    Joined Jun 25, 2004
    279 posts, 189 likes
    Corsair F24 Mk1
    003 US San Francisco Bay, CA
    I wrote that 20% of breaking load is in the ballpark.
    You can read it right off the scale on a Loos gauge.
     


    Last edited: Mar 5, 2019
  8. Scott B

    Scott B Moderator

    Joined Sep 20, 2006
    2,592 posts, 153 likes
    Hunter 33
    CA Georgian Bay, Ontario, Canada

    Ah, perfect. That is the info I've been looking many months to find. The "professional rigger" that set mine, googled Selden mast but failed to take into account IMF. There are very few, if any, knowledgeable in Selden masts in our area. Thank you,
     


    DrJudyB likes this.
  9. DayDreamer41

    DayDreamer41

    Joined Oct 29, 2016
    1,232 posts, 609 likes
    Hunter 41 DS
    Un Port Huron
    @DrJudyB Oh Wow, I was at the boat yesterday, opened up the cover on either side of the mast to get a luff measurement with the retrieval line and the tape measure pulled tight my prebend looks to be set more like 1% of the measurement (5"-6") from the goose neck to the mast head, it also appears that there is too much rake, but I couldn't really measure that as it was too windy to assess.
    This has me wondering if the shroud tensions are anywhere near recommended settings, I guess a Loos gauge purchase is in my near future (at least I have established an excuse to purchase one). I am having new sails made and the "P" measurement was a point of question so I figured I needed to put that to bed, the "E" measure was the same as the old sail, the new sail will have an "E" measurement just a tad shorter to allow me to flatten the main when needed, something I wasn't able to do with the old sail.
     


  10. Don Lucas

    Don Lucas

    Joined Jan 12, 2011
    762 posts, 21 likes
    Hunter 410
    US full time cruiser
    Where in the instructions does it say D1 should be about 20% of breaking strength?
    This is the whole question I asked basically.
     


  11. seadaddler

    seadaddler

    Joined Dec 19, 2006
    5,486 posts, 140 likes
    Hunter 36
    US Punta Gorda
    Maybe you could not flatten the Sail because it is old and all stretched out.
    Nick
     


  12. DayDreamer41

    DayDreamer41

    Joined Oct 29, 2016
    1,232 posts, 609 likes
    Hunter 41 DS
    Un Port Huron
    If I understand correctly the, "Lower Shrouds" are the D1's
     

    Attached Files:



  13. seadaddler

    seadaddler

    Joined Dec 19, 2006
    5,486 posts, 140 likes
    Hunter 36
    US Punta Gorda
    What year 410 and we all got a manual from Hunter describing how to tune the IMF mast.
    Nick
     


  14. DayDreamer41

    DayDreamer41

    Joined Oct 29, 2016
    1,232 posts, 609 likes
    Hunter 41 DS
    Un Port Huron
    Yes the sail is old and bagged out, I am having a new sails made should be done soon this will certainly allow for better performance in heavy wind conditions with improved sail shape. Even the leech cord on the old main would not stay put, the cord was worn where it was best in the cinch block.
     


  15. Will Gilmore

    Will Gilmore

    Joined Oct 19, 2017
    4,294 posts, 2,250 likes
    O'Day 19
    US Littleton, NH
    Page 55.
    "• Check that the upper part of the mast is straight athwart
    ships.
    Adjust if necessary using the intermediate shrouds. Slacken
    one side by the same amount you tighten on the other.
    • Tension the lower shrouds to 20% of their breaking load.
    Check that the mast is straight athwartships. Adjust if
    necessary using the lower shrouds on the same principle as
    above. The mast should now have approximately the same
    pre-bend as it had when it was lying on the trestles, and it will
    be straight athwartships."
    Unless I'm misinterpreting the lower shrouds and D1 being the same.

    -Will (Dragonfly)
     


  16. shemandr

    shemandr

    Joined Jan 1, 2006
    3,887 posts, 842 likes
    Marblehead Skiff 14'
    US Greenport, NY
    I think it’s standard to use the 20% of “Breaking strength” as the maximum standing rigging should be tensioned. I’m putting BS in quotes because there are measures of wire failure short of it parting. In any event rig tuning is more about length than tension. The tension is largely governed by the wire size specified.
     


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  17. DayDreamer41

    DayDreamer41

    Joined Oct 29, 2016
    1,232 posts, 609 likes
    Hunter 41 DS
    Un Port Huron
    The Selden instruction should really read, "To a Maximum of 20%" the way its stated makes it sound as if once you get 20% the rig is perfectly tuned. This is where the folding rule method makes more sense especially used in conjunction with a Loos gauge.
     


  18. DrJudyB

    DrJudyB

    Joined Jun 25, 2004
    279 posts, 189 likes
    Corsair F24 Mk1
    003 US San Francisco Bay, CA
    That’s exactly right. Tuning a rig is all about setting wire lengths so that the mast has the right shape when it’s under load. Tension on an individual wire is the “end result”of all the other wires all pulling against each other ( to resist the heeling and pitching forces) when they’re set to the right length. Wire Length and mast shape are thefirst objective during the initial dockside tune.

    Once you have the right shape, you add or reduce the tension while under sail for the final adjustment. You add or reduce tension as needed to keep the mast from a) going too far out of column when heeling, and b) banging around when you tack or gybe, etc.

    I’m not saying that wire tension is unimportant. I'm just saying that you have to focus on mast shape and wire length first, before you can finalize the tension.

    JudyB

    [Edit: commas and apostrophes needed fixin']
     


    Last edited: Mar 15, 2019
    Will Gilmore likes this.
  19. DrJudyB

    DrJudyB

    Joined Jun 25, 2004
    279 posts, 189 likes
    Corsair F24 Mk1
    003 US San Francisco Bay, CA
    Sort of, but not quite. Most shrouds (which resist lateral loading) end up in the 15 to 20% range of breaking strength at static equilibirium (steady loads) at the dock. That gives them a safety factor of 5 or 6:1.

    Stays, which resist loads fore and aft, often end up at25% of breaking load at the dock. Safety factor of 4:1.

    If the rig designer did his calculations correctly, s/he sized the wire to resist the heeling force and to protect the mast with the appropriate safety margins built in.
     


    Last edited: Mar 15, 2019
  20. Jackdaw

    Jackdaw

    Joined Nov 8, 2010
    9,851 posts, 2,905 likes
    Beneteau First 36.7 & 260
    US Minneapolis MN & Bayfield WI
    They are not the same.

    D1s are DIAGONALS, the set between the deck and 1st spreaders; hence the '1'
    Shroud are shrouds; always vertical, and often referenced as V1, V2 etc for the same reason.