Taller rig questions

Discussion in 'Sailboats' started by TADAMS, Jan 16, 2010.

  1. TADAMS
    Joined: Jan 2010
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    TADAMS Junior Member

    I am pondering increasing the rig height on my Farr design #54 and would appreciate input from this group. The boat is a 30 ft IOR design from the mid 1970's. Approx 5000lbs displacement - 1900 lbs ballast - 5'3" draft - beam 10 ft . Big main, small jib fractional rig - single swept spreaders with runners - by modern standards a very stout mast section.

    The boat was purchased as a fixer upper and is missing lots of rig parts and has no sails so it seems a perfect time to modernize the rig. Another reason to explore this idea is the mast from the boat was keel stepped and a previous owner started the conversion to deck stepping having done all the glass work to fill the deck hole for the mast. The reason for this change is that the mast is extensively damaged at the boom vang attachment point - multiple cracks extend almost completely around the mast in this area. The previous owners idea was to simply cut off the mast at this location sacrificing about 4" of rig height and use the remaining spar length stepped on deck. Of course a compression post will be added below deck. He cut the bad section out of the mast so now I have a 5 foot long section of mast that I could use to cut and splice into the remaining mast section to increase rig height/ sail area. My thought is to add approx 30 inches to the original rig by splicing a section onto the remaining mast and completing the conversion to deck stepped. This would increase the I and J measurement by 24 inches each. Sail area would go from approx 354 sq ft to 394 sq ft.

    So other factors that may help with imput / suggestions are:

    The boat has its orginal fractional rig with single swept back spreaders and running backs. I do not intend to move the speaders and know that i may create jib sheeting angle problems ?

    The boat will be club raced and a little local cruising - mostly in winds of 4-8 knts.

    Boat design details are on the Farr website under design #54

    The boat is stock in all other ways. I have conversed with another owner of this design and he feels the boat really needs the additional sail area for North American windspeeds.

    The boat does seem under rigged by todays standards

    Thanks in advance for any ideas
     
    Last edited: Jan 16, 2010
  2. Paul B

    Paul B Previous Member

    Your boat is quite under rigged for the conditions you plan to sail in. The sistership that I have sailed on in Long Beach, CA (Jabbed Again/Gizmo) had more rig added than you plan, and Long Beach is quite a bit windier than the 5 to 8 knots of breeze you mention.

    I believe Gizmo added 3 to 4 feet of rig when the original mast broke, and they sailed much better in lighter wind after that. They remained very quick in a breeze as well.

    You will have to move spreaders if you add to the rig height, otherwise the lower panel (deck to lower spreader) will be too long an unsupported span. Also, as you mentioned, the upper spreaders will now be "higher" on the rig, so they would need to be narrower or lower, otherwise you will have sheeting problems. You can't make them narrower or the upper shroud angle will be too narrow and the rig will collapse, so you need to move them down.

    If possible it would be best to stay with the keel stepped mast. Going to the deck step is going to limit your ability to tune the correct amount of pre-bend into the rig. Not to mention the spar was not engineered to be deck stepped using that section.

    Those old Farr HTs are pretty nice boats, and even better with more rig. Hopefully you can get it all sorted out.
     
  3. TADAMS
    Joined: Jan 2010
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    TADAMS Junior Member

    taller rig

    Paul - thanks for your response -

    The boat you mentioned in your response - Gizmo - was the boat as designed other than the taller mast ? I have been told design #54 tends to broach easily and some were updated with deeper rudders to correct this problem. Any thoughts or info here ?

    What is the proper placement of spreaders on a single spreader rig like mine as far as distance from deck level to spreaders and spreaders to forestay attachment point ? I have seen reference online to 50% but find that in looking at similar rigs in real life deck to spreader tends at more like 60% (Hobie 33, Laser 28, Tarten 10, Farr 1104, Farr 1020 ).

    Thanks again
     
  4. Grant Nelson
    Joined: Feb 2005
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    Grant Nelson Senior Member

    Standard is indeed between 50 and 52 percent of mast length up from the deck. Variations are possible, but as was said, the higher up you put them the weaker your mast will become and if you are already making it longer, and deck stepping it, you will already be adding to changes that are driving your mast (and standing rigging) under under the designed strength. No need to make even weaker...
     
  5. Paul B

    Paul B Previous Member

    I have never heard or experienced any broaching issues with this design. It was much better than most of the other IOR boats of the time in that regard. I only knew of 2 examples of Design 54 in SoCal, Jabbed Again/Gizmo (Long Beach) and Scrimshaw (Marina del Rey). Neither seemed to ever have broaching issues.

    That's not to say things wouldn't be improved with a new rudder. We had this discussion about changing the rudder on a Design 65 on this board a few months ago. Attached is the sketch I made over the rudder of Design 54 to try to show what I would think about doing. of course a new rudder is not an inexpensive modification.


    Different Spar Designers use different numbers. Some like to use 52% of the overall distance from the forestay attachment to the top of the house. I think Farr used something closer to 55% on the original D. 54 spar layout. I'm sure you can get the original spar drawing from Farr for little more than the cost of printing and postage.

    When Gizmo went up in their rig I recall they went to a 2 spreader rig.
     

    Attached Files:

  6. TADAMS
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    TADAMS Junior Member

    taller rig

    I have a drawing from the Farr office - as you indicated spreader placement is at 55%.

    I love the look of your rudder outline. Based on the depth of knowledge you show on your posts i have seen on this forum you must be a designer / naval architect / boatbuilder ?

    I assume the newer rudder shape would be give better control in bigger winds and with no increase in wetted area should be equal to the old design in light air ? Is there a downside to the deeper foil ? increased frontal area ?
    How big of a factor is this ? How would the two shapes compare in light wind racing ?


    thanks to all members of this forum for their responses - this site is amazing
     
  7. Paul B

    Paul B Previous Member

    The rudder sketch is just that, a quick sketch. It was done in a simple drawing program and I don't even know the dimensions. It was an attempt to show what a modern rudder would look like compared to the original.

    I have worked in a yacht design office and for a boatbuilder in the past. I've since moved on to more lucrative design/engineering/manufacturing endeavors. Now I am simply an enthusiast.


    A deeper rudder should be better in all conditions, but in most conditions it would not be significantly faster. I doubt it would make a 3 sec/mi (one boatlength per mile) difference across the range of conditions and points-of-sail.

    Of course to make something this high aspect and make it thin enough it would be a pretty high tech construction and probably pretty expensive unless you have a good connection.
     
  8. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    If the mast has severe cracking, it is not as stout as you believe. Also, stepping a mast on deck usually requires a heavier section because it is not a fix pin any more.
     
  9. Paul B

    Paul B Previous Member

    Nice job jumping in 10 days late so you can state the obvious.

    Note Post #2, paragraph 4.
     
  10. Grant Nelson
    Joined: Feb 2005
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    Grant Nelson Senior Member

    Hey Paul B. quit picking on Gonzo, after all he has 4000 posts to your 1000, so he must be more wise than you :p
     

  11. Paul B

    Paul B Previous Member

    I guess you are right. However, of the 4000 posts he has made, how many do you think are seriously incorrect? From what I see it is a pretty high percentage.

    Some other chucklehead on this site once told me my opion didn't count because I had less points than some other waterhead. At the time I didn't even know there was such a thing, and I still pay no attention to it. It is the equivalent of a high school popularity contest, with no bearing on actual knowledge or abilities.
     
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