Taller mast & Longer boom Question

Discussion in 'Sailboats' started by Mark Seafarer26, Aug 10, 2016.

  1. Mark Seafarer26
    Joined: Aug 2016
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    Location: Lake Erie

    Mark Seafarer26 New Member

    I currently sail a Seafarer 26 (McCurdy/Rhodes Jr.) with a 30' mast and 8.5' boom and skeg hung large rudder. Standard from factory standing rigging, and can trim sails for a balanced helm. Currently use a 155 roller genoa and unreefed full batten main most the time until 15 knots wind then add reef in main and shorten up genoa as needed. I have an oppertunity to buy the standing rigging from a Ranger 26 ( Gary Mull) including sail inventory, the boat is salvaged. The I (mast height is 33' vs 30' current), E the boom is 10' vs 8.5' current. On the Ranger the J is 11.5' vs 10.5'current. I would also add an additional lower shroud aft of the upper for additional support. What benefits would I likely see and what potential disadvantages would this proposed scenerio? Thanks in advance for your thoughtful replies.
     
  2. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    It appears that the alternate rig would be adding a significant amount of sail area. The presumption is that you will would have more power. Do you really need the presumed extra power? It is extra power only if the sails are as good as the ones that you are presently using. The boat may or may not like the extra area. It is sure to become more tender....higher CE in addition to the increased area. You will be reefing sooner You may also run into some helm balance problems. Will the rigging, particularly the chain plates, withstand the extra load? Then, of course, there is the cost factor. It is fairly certain that you already know that estimated costs of any boat project is famously an underestimation.
     
  3. Mark Seafarer26
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    Location: Lake Erie

    Mark Seafarer26 New Member

    Messabout, you nailed it on the head I am seeking more power to windward. I am planning an additional set of lower shrouds aft. Currently one lower shroud forward and one upper shroud on center line. Definitely worth considering rigging strength. Thanks also going to talk to a rigger.
     
  4. MikeDrummond
    Joined: Nov 2006
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    Location: New Zealand

    MikeDrummond Junior Member

    Here are rough and simple estimates based on assumption of sailing at the same max heel angle, say 30deg.

    The tall mast should be heavier with higher centre of gravity so there will be a reduction in righting moment, and therefore a reduction in heeling force & thrust. Based on 100kg rig weight, RM is ~ -3%. For the same heel angle, the shroud load should reduce, not increase.

    Assuming similar heel angle, sail depth and trim, the taller rig reduces the overpowering TWS to 12.5kn from 15kn. This is partly due to reducted RM and partly to longer heeling arm.

    In overpowered conditions your sail trim and performance is limited by righting moment. Rig height is not relevant because at 30deg you start twisting or reefing anyway. Speed reduction ~-1%

    In underpowered conditions the extra mast height will reduce lift-induced drag significantly. ~5% speed increase due to this drag reduction.

    I don't think weather helm will be a problem - although the thrust is further to leeward when heeled and untwisted sails, this is countered by lower thrust. In lower TWS there will be more heel with the tall rig, therefore more helm in lower windspeeds.

    The longer forestay will have more sag for the same load. Depending on the condition of chainplates etc you might want to accept 5-10% more sag and keep the loads constant.

    Mike
     
  5. Mark Seafarer26
    Joined: Aug 2016
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    Location: Lake Erie

    Mark Seafarer26 New Member

    Mike, Thanks for the input and well thought out analysis. Without a complete understanding of the physics at play this was helpfull. Is there a book you would recommend that would help with a remedial understanding of the sloop sail dynamics for the layman to digest? Thanks again for your offering.
     
  6. Chuck Losness
    Joined: Apr 2008
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    Location: Central CA

    Chuck Losness Senior Member

    You might be able to get some idea of the effect of the changes by going to the Catalina 30 forums and searching for the differences between a Cat 30 standard rig and a Cat 30 tall rig with bowsprit. PHRF of SoCal rates a Cat 30 standard rig at 192 and the tall rig with bowsprit at 168. That is a 24 sec per mile difference which is a big difference. Most sailing in SoCal is in 10 knots TWS or less so having more sail area really helps light air performance. Exception is in the Long Beach area where it can really howl some afternoons. I don't know your conditions on Lake Erie. If your typical wind is around 15 knots TWS then adding sail area would be a waste because you are already achieving max performance. But if your area is a light wind area then the extra sail area should show performance gains.
    Good luck with your project.
     

  7. Mark Seafarer26
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    Location: Lake Erie

    Mark Seafarer26 New Member

    Chuck, Thanks for this idea of same hulls etc., tall rigs vs standard rigs. I also had that conversation with a friend who had a Catalina 27 standard rig vs his newer Catalina 27 tall rig. Lake Erie can be go from becalmed to 30 knots if a squall rolls thru. but 5-15 knots is the norm. I am looking for more power going to windward so that bumping up against 3-5 footers & chop doesn't have the impact it currently does. Thanks Chuck for your input it is much appreciated.
     
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