Reasons to Reduce Mast Height

Discussion in 'Boat Design' started by CharlieDanger99, Jun 13, 2021.

  1. CharlieDanger99
    Joined: Jun 2021
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    Location: Tampa Bay

    CharlieDanger99 Junior Member

    Slowly chugging along with my Rhodes Swiftsure 33 restoration. I've gotten to the point where it makes sense to address the rotten compression post. I'm wondering if it would make sense to convert her from a deck-stepped rig to keel-stepped. My reasons for considering this:

    It is a hull-up restoration I'm doing as a hobby. When I bought the boat it was a bare hull with no interior aside from structural bulkheads, with a mast and boom. I imagine it will require a similar amount of work either way to get her in the water.

    The mast is not original, it is a Lefiell spar, 20+ years old, no major corrosion, just needs new paint, and rivets/screws in old hardware mounts. It is 4' taller than the original wooden box mast. I would lose ~5' by stepping it to the keel, but as I understand a lower aspect ratio is better for a safer boat, and having a taller mast than the boat was designed for seems like a risk factor. I don't know how much she was sailed after the mast was installed but there was some delamination in the hull deck joint tabbing I had to fix, though it was probably more an issue of age than anything.

    She has a custom 4' bowsprit of 316 stainless installed by the yard that built her, affording me extra sail area in the headsail for light winds. I plan to use her for cruising and destination trips, not racing.

    There is no standing rigging, so I will have to re-design that regardless of my decision with the mast height.

    I know that I won't get all the answers I need from a forum, so any recommendations for rigging textbooks would be appreciated. I will need to read up anyway when the time comes to rig the mast. Right now I just need to decide whether to build a new compression post or build a step in the bilge. The only major modifications I can foresee would be adjusting the spreader height and angle, and figuring out how to reinforce the coachroof where the mast would pass through, but I'm sure there's a lot more to consider. I am concerned that if I have to move the spreader mounts the old holes would be enough to weaken the spar, even if filled with screws/rivets. Is this something worth looking in to, or is the additional mast height more of a benefit? I'm aware that I can just reef the main earlier with a taller mast, but I'm wondering if the extra 4' over the original sail plan will make enough of a difference in light wind to be worth potentially putting excess stresses on the hull and deck. Again, would love some book recommendations to understand exactly how these loads get distributed in the rigging and boat, but feel free to tell me if this is a totally useless idea. My experience so far has been limited to fiberglass and plywood work, and I'm learning as I go.

    Additionally, in either case I also need to come up with a new attachment point for the mast step, so if anyone can point me toward some diy friendly solutions for that I'd love to know. It seems lefiell is not selling them anymore, but if I'm wrong, or if there's another off-the-shelf option that would work that might be ideal.
     
  2. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    Welcome to the Forum Charlie.

    You mentioned re your mast :
    So does this mean that you would then effectively lose 1' of height when compared to the original mast?
    If the mast height would then be just 12" shorter, then I don't see any reason to move the current position of the spreaders and lower shrouds.

    And with a 4' bowsprit you should still be able to set the same amount (if not more) of sail as the original, except that it will be a lower aspect ratio.
    Will you keep her as a sloop rig, or would it be viable to have an inner forestay for a cutter rig?
    A 4' extension for the base of the forestay is quite a lot really, so there might be a concern about lee helm?

    Re a good book, I have a copy of this one by Matthew Sheahan about masts and rigging, and it is excellent.
    https://www.amazon.com/Sailing-rigs-spars-Installation-maintenance/dp/0854297537
     
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  3. CharlieDanger99
    Joined: Jun 2021
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    Location: Tampa Bay

    CharlieDanger99 Junior Member

    Thanks for the recommendation. Yes I plan to add an inner forestay for rig stability and redundancy. I may look into permanently cutter rigging her but my current intention is just to have somewhere for a backup foresail, and some extra support should there be any issue with the sprit. I'm thinking about glassing a samson post up from the bottom of the chain locker so I can put a chainplate facing aft where it exits the deck, and can still use the top of the post to tie off at anchor/on a dock. I actually have some letters of correspondence from the 60's indicating that the original owner worked with Philip Rhodes, or at least his office, to design and fit the bowsprit. Seeing as she's been sporting it for this long I assume the performance must be good enough not to ditch it. In the grand scheme of the project though, shortening the headstay and converting back to the original bow mounted fitting wouldn't be the worst thing in the world if I find lee helm to be a major issue. As to your comment about the spreaders, they would be lowered 5' in relationship to the chainplates compared to when the mast was installed on a deck step if I kept them at their current height. The resulting angle of the lowers to the mast, as well as that of the uppers to the deck would be increased. In theory that might actually reduce the load on the rig, but in any case I will pick up a copy of that book and try to figure out the best plan of action.
     
  4. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    An additional inner forestay sounds like a good plan - we have one on our 35' boat, in what some call a 'slutter' rig. The outer forestay has a roller furling genoa, and the inner removable stay is for a hank on working job (or storm jib, but we have never used this yet). It has a Highfield lever type of tensioning device on it.

    If the current mast is 4' taller than the original design, I would have thought that you would only lose maybe 2' if you now make it keel stepped, assuming that you have about 6' of height between the mast step on the coachroof and the new keel step?
    And re the bowsprit, maybe the Swiftsure class did tend to have (too much) weather helm when heeled, hence why they fitted it?
    In which case then you should be fine with it.
    And if you keep the spreaders where they are, and their new height is 2' (or even 5') lower, then yes, by increasing the angle of the lowers to the mast (or decreasing the angle to the deck) you will reduce the load in them which is no bad thing really.
    Matt's book does explain all this very well.
     
    Last edited: Jun 13, 2021
  5. CharlieDanger99
    Joined: Jun 2021
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    Location: Tampa Bay

    CharlieDanger99 Junior Member

    You're correct about the mast height. I should clarify that when I say the spreaders will be 5' lower, I mean in relation to where they would be if I kept the current mast deck stepped, not in relation to the spreader height on the original design. As in, if I lower the mast step 5 - 6' below the coachroof, the spreaders would then be 5 - 6' closer to the deck. My only concern when writing the original post was that if the coachroof becomes a contact point for the mast, it may affect the way the shrouds handle the loads, and whether or not the spreader height would need adjusting for best efficiency/safety.
     
  6. rangebowdrie
    Joined: Nov 2009
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    Location: Oregon

    rangebowdrie Senior Member

    As typical of Rhodes, what an "easy on the eyes" sheerline, a joy.
    Anyway, (I'm no NA, just my opinions,) but their are very few of the older CCA inspired boats that would not find an extension of the foretriangle base by way of a bowsprit to be a good thing,, I'd keep it.
    Were their not two rig heights offered,, a taller one for more "performance"?
    I believe that the original masts were wood,, if so, the newer, (and taller,) alloy replacement mast could have been chosen because it offered no additional weight over the wood one.
    Cruisers generally have easier nerves when things are not so high in the air and the CE is lower, I think that a "stock" height and being keel stepped will give you more peace-of-mind when offshore.
     
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  7. phillysailor
    Joined: Nov 2012
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    phillysailor Junior Member

    I think you'll get what you pay for, in terms of opinions here and at the office cooler.

    Are you considering new sails? If the rest of the boat is a resto job, perhaps you've a sailmaker in mind. In that case, make a modest downpayment... a couple hundred purchases significantly better opinions having the benefit of knowledge, your respect and a shared sense of investment in the outcome.

    Modern sailmakers have moved away from the huge genoa sails common to that era, and might have definite ideas about how to employ roller furling gear and asymmetric chutes to increase your enjoyment of a cruising sailboat. A taller mast and a bowsprit offers options not available to your designer way back when, but he'd certainly take advantage of them now!
     
  8. CharlieDanger99
    Joined: Jun 2021
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    Location: Tampa Bay

    CharlieDanger99 Junior Member

    Thanks for the reply. She certainly is a beautiful boat, I don't think I would be willing to put this much work in if she wasn't. There isn't too much info available online but I haven't seen anything about it being offered with different rigs. I'm not too sure why one of the previous owners chose the taller mast, but there was some other DIY repair work done when it was installed according to the guy I bought her from, so maybe it came off another boat, or was in some way cheaper than a matching height spar. Either way, peace of mind while sailing is the philosophy I'm following for the rebuild, so at this point I'm pretty much settled on dropping it to the keel.
     

  9. CharlieDanger99
    Joined: Jun 2021
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    Location: Tampa Bay

    CharlieDanger99 Junior Member

    I do plan to get in contact with some sailmakers as the splash day gets nearer, but I expect I'm at least a few years out from that. I started the project while finishing my degree, so my focus is currently limited to to the interior rebuild and re-finishing the exterior, with plans to address the rigging, engine, and electrical systems when I get a full time job. I will certainly benefit from some professional opinions when that time comes, but for now I'm enjoying building up my own body of knowledge through research to be able to bring an old boat back to life.
     
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