Steadying sail

Discussion in 'Stability' started by fish53, Jan 22, 2020.

  1. fish53
    Joined: Apr 2018
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    fish53 Junior Member

    I'm thinking about a steadying sail for my 26' double ended full displacement boat. I haven't had much luck finding a method of calculating an effective area. I have a 28' mast available with a 9' boom and at this point I can incorporate a mast step in the deck easily. I've calculated the CLR and have room about 12" aft of that for a step. I don't mind cutting down the mast if necessary although it seems to me the higher you place a steadying sail the smaller it's area can be, whether or not that's a good thing I'm not sure.
     
  2. gonzo
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    gonzo Senior Member

    Steadying sails are usually on stubby masts. I agree that the higher the sail, the more effective it will be. However, the rigging will be applying higher forces the smaller the angle between the wires and the mast becomes. I would say that if the mast is about 70% of the length of the boat over the waterline, it will work fine. The type of sail will also have a great effect on how tall the mast needs to be. A marconi sail will need a higher mast than a lug.
     
  3. bajansailor
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    bajansailor Marine Surveyor

    Is your double ender one of these lapstrake fibreglass boats that are so popular in Scandinavia (or similar perhaps?)
    Can you maybe post a photo or two of her?
    What do you use the boat for, and under what sort of conditions?
    Many of the traditional small fishing boats in Europe would have a little gaff rigged steadying sail at the stern.
    Do you want it to just have a steadying effect, or would you ideally like the boat to become a motorsailer as a result of adding the rig?
     
  4. fish53
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    fish53 Junior Member

    It's a fishing/cruising boat that isn't completed yet, the hull is an ex-USCG motor whaleboat that I've built new decks and wash rails on, repowered and am starting the new pilothouse on soon. I have a picture of what it used to look like
    whaleboat 1.jpg
     
  5. bajansailor
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    bajansailor Marine Surveyor

    She looks very nice in this 'before' photo. Is your new pilothouse going to be significantly different to the one shown above?

    Re "I've calculated the CLR and have room about 12" aft of that for a step" - is this approximately in the cockpit above, by the pilothouse bulkhead?
    Do you want to have a jib (headsail) type of steadying sail (perhaps on a roller furler), or a boomed sail behind the mast?
    Re mast height, I am thinking that 28' would be way too tall; maybe about 15' above the cockpit floor might be better?
     
  6. fish53
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    fish53 Junior Member

    The currently contemplated pilothouse is shorter than the one shown, ending about at a point between the two side windows which places it a few inches forward of the mast location. I have considered a foresail simply for use as additional power for downwind motorsailing. I would prefer the steadying sail be on a boom aft in order to help point the boat into the wind when drifting or on the mooring or anchor. A flat sail under tension to prevent flapping would be best for that application as I expect no drive from it. Something similar to this illustration, I'm just unaware of a method of calculating an effective area. MWB 320.jpg
     
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  7. bajansailor
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    bajansailor Marine Surveyor

    Re your requirement for the steadying sail "to help point the boat into the wind when drifting or on the mooring or anchor", I am thinking that it should ideally be much further aft.
    I think that if you have a sail on the boom as shown in the sketch above, the boat will still tend to yaw about a lot, especially when anchored or on a mooring, even if the mast is behind the CLR of the hull.
    The photo below illustrates a typical arrangement for a steadying sail - it was found at this link.
    Building a hybrid fishing boat - SINTEF https://www.sintef.no/en/latest-news/building-a-hybrid-fishing-boat/

    A foresail as shown in your sketch above is not going to help much when going downwind, but it (and the boomed main) should be useful when motor-sailing anywhere between a close reach and a broad reach. Your main concern here would be the stability aspect.
    It might even be useful to have a mizzen at the stern for use as a steadying sail, along with the main mast further forward - again, if the stability can cope with this.

    Fishing boat steadying sail.jpg
     
  8. fish53
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    fish53 Junior Member

    Something more like this you think would be more flexible and useful? Obviously this is toying with the concept and I'm trying to zero what's possibly the best plan. MWBF.jpg
     
  9. bajansailor
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    bajansailor Marine Surveyor

    That mizzen sail shown in your sketch above would be a much more useful steadying sail.
    You could even make it a gaff rig, as per my photo above - by doing so you will almost double the sail area for the same mast height and boom length.
    When you are motor sailing it might be easier to just have a jib up forward and the mizzen aft.
    The centre of effort of the mainsail as shown is relatively high up - it will add a lot relatively to the wind heeling moment, while adding just a bit towards forward motion. And the logistics of stowing the mainsail on the boom could be rather difficult, unless you are 7' tall! Or you have a roller furling system, which is a lot of extra expense.

    Will you need the main(sail) boom for (eg) loading stuff onboard? If not, then maybe dispense with it? And just have a jib and mizzen for use as steadying sails?
     
  10. fish53
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    fish53 Junior Member

    I'll work on that a bit using your recommendations and see how it works out. I do want the boom for lifting purposes but if I don't need a sail on it that would simplify things.
     
  11. Blueknarr
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    Blueknarr Senior Member

    Here's an idea taken from a sailboat, but could be adapted. It allows the boom to lift and would not require a second mast. Simply attach top of sail to boom then stretch lines to the deck. It can be quite small.
    Anchor-Riding-Sails-Keep-your-Boat-from-Swinging-Streaming-Video_2.jpg
     
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  12. fish53
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    fish53 Junior Member

    Certainly simplifies things doesn't? Good suggestion, thank you.
     
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