Mast vs boat length

Discussion in 'Sailboats' started by SeaMaster, May 11, 2022.

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  1. SeaMaster
    Joined: May 2022
    Posts: 2
    Likes: 0, Points: 1
    Location: Miami

    SeaMaster New Member

    Hello everyone, I'm humbled to have found such a great forum with so many knowledgeable sailors.
    I'm relatively new to sailboat design and standard but I could not resist to buy what I hope is a great opportunity to own a cruiser and possibly live in it for a long time.

    The brand is SeaMaster, it was out of Ft. Lauderdale and so far I have not found anybody that has ever heard of it. Anyways, the company closed down in 2005 and the had a few sailboat left unfinished. I'm pretty handy so I jumped on it and got a 54ft for $20k total.
    The boat comes with almost everything, she floats, engine runs good, has 2 AC units 2 heads, all plumbing are done, all she needs is interior work like cabinets, beds and seating.

    The boat came with a mast (laying down on deck) that is supposed to be deck stepped and is 53ft high. I read some other threads regarding opinions on the high of the mast and what I found in general is that the mast should be about 1.2 or 1.3 the length of the boat. So I'm not even at 1.0 with this mast. I understand that the taller the mast, the more sail area you get and all is better sailing, but to my purpose and general understanding, how much worst would it be to have a rigging like mine? is it really going to be that bad of a difference for let's say 0.3 less than the suggested average length?

    Also I found some insane calculations for the Sail Area / Displacement Ratio (SA/D) that is based more on the named coefficient rather than just the mast size.

    To make it short should I start looking for a used taller mast? Keep in mind I wont race with this, just cruising.

    Sail away
    Danny
     
  2. AlanX
    Joined: Mar 2022
    Posts: 91
    Likes: 18, Points: 18
    Location: Perth, Western Australia

    AlanX Senior Member

    Although mast lengths average 1.3xLOA, the sail area and configuration (type and aspect ratio) determine the mast and rigging specification.
    An estimate for a cruising sailboat is 16 to 18 (say 17) for SA/Disp^0.667, where SA is sail area and Disp is volume.
    So displacement is more important than LOA alone.

    Once you have your estimated sail area, you can look at sail and rigging configurations that may suit your mast.
    You may have to accept a lower aspect ratio then you may like. For example a Junk rig. Depends what you discover.

    If you want to design your own rigging and check the required mast section modulus google "Guidelines for Design and Construction of Large Modern Yacht Rigs".
    Or you may have to pay someone to do it for you.

    Regards AlanX
     
  3. jehardiman
    Joined: Aug 2004
    Posts: 3,222
    Likes: 673, Points: 113, Legacy Rep: 2040
    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    Welcome Danny,
    Realistically, mast height depends on what the vessel is for and where it sails. Hulls were often delivered with 2 or more mast heights. High latitude cruisers often have shorter masts than similar length or shorter racing vessels. Check the SA/D ratio for the existing rig and decide if that is suitable for what you want. If not, have a new taller rig designed, knowing that rig strength for weight aloft is going to be reduced. SailboatData.com - the worlds largest sailboat database https://sailboatdata.com/ turned up no name match

    FWIW, I also noticed these threads turned up in a google.
    54' SeaMaster Sail Construction photos https://www.boatdesign.net/threads/54-seamaster-sail-construction-photos.7759/
    Do- It- Yourselfers https://forums.sailinganarchy.com/index.php?/topic/19565-do-it-yourselfers/

    Edit: X-post with AlanX
     
  4. Blueknarr
    Joined: Aug 2017
    Posts: 1,314
    Likes: 322, Points: 83
    Location: Colorado

    Blueknarr Senior Member

    Welcome to the forum.

    At your level of experience, you won't notice or appreciate the difference of performance gained by a taller mast.

    You most likely will spend more time reefed with a taller rig than with the shorter one.

    You will notice the bigger checks associated with bigger sails.
     
    wet feet likes this.
  5. SeaMaster
    Joined: May 2022
    Posts: 2
    Likes: 0, Points: 1
    Location: Miami

    SeaMaster New Member

    Thank you guys, lots of good points and info.
    AlanX I found that if I put a 20 boom and 135% genoa I get 17.42 SA/D. I read that anything above 15 is a good midpoint and above 18 starts to be high performance with the top reaching 30 + for extreme racing

    Main sail: 556 sq. Ft
    135% Genoa: 801 sq. Ft
    Total sail Area: 1357 sq. Ft
    Displacement 44,000lbs
    SA/D = 17.42

    jehardiman those links are the boat I just bought. There isn't much info available, I have some drawing the builder (Paul) gave me and it does show a taller mast. In your opinion is deck stepped ok for a boat that size?

    Blueknarr, that's exactly the expert advise I was looking for, I think for my level of experience I'll be fine for now, put the autopilot on and read a book.

    cheers guys.
     

  6. jehardiman
    Joined: Aug 2004
    Posts: 3,222
    Likes: 673, Points: 113, Legacy Rep: 2040
    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    SeaMaster, the question you need to answer is are you going to cruise and/or single hand, or are you going for something else. Keel vs Deck stepped is not a really a difference unless you expect to be out in the great beyond and knocked down/rolled. In that case a keel stepped mast will typically leave a stub to jury rig to (i.e. the fixity of the column leads to mid-column failure above the deck rather than the whole rig collapsing off the deck.) Otherwise, it is as AlexX and Blueknarr say, how big of sails (both main and jibs) do you want to handle and pay for. By the time you get to a 50+ foot mast, a single hander will have significant issues simply with the size and weight of the sail, not to mention the power.

    Edit to add: The whole trade off between keel or deck stepped has many variables. Strength, compression post size, hull squeeze, and leakage just being some.
     
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