Reducing air draft calculations

Discussion in 'Boat Design' started by Manateeman, Oct 18, 2019.

  1. bajansailor
    Joined: Oct 2007
    Posts: 386
    Likes: 63, Points: 28, Legacy Rep: 37
    Location: Barbados

    bajansailor Marine Surveyor

    Hello Mark,
    Your link to the AYRS does not work, but hopefully this link will.
    https://www.ayrs.org/repository/AYRS011.pdf
    I can see why you are keen on the wishbone rig - it does seem to have a lot going for it.
    But if you are going to have a rig in similar proportion to that shown on the sail plan for Shenanigan (but cut down a bit), then you will have to make a lot of changes.
    For instance, you won't be able to have twin back stays on the main mast - the aft support would have to be via a triatic stay to the top of the mizzen (along with your running backstays).
    I suppose you could have twin backstays, but you wouldn't be able to ease the sheet on the wishbone very far before it bashes on a backstay.
    There are good arguments for keeping the staying on the two masts independent of each other.

    If you did have a wishbone, then you could perhaps have a furling system attached to the aft side of the main mast as per the Facnor link below.
    Description and technical information - Mainsail furlers - Facnor http://www.facnor.com/uk/products/mainsail_furlers/description_and_technical.asp
    As I doubt that you would want to have to hoist the sail each time, never mind bagging / stowing it when you take it down.
    If you go for a ketch rig you could have a furling system for the mainsail in similar fashion. Even with a good sail track that has minimal friction it can still be hard work hoisting a mainsail, even more so if it has full length battens.
     
  2. Manateeman
    Joined: Oct 2019
    Posts: 31
    Likes: 1, Points: 8
    Location: St. Mary’s Georgia

    Manateeman Junior Member

    Hi. Thank you for the proper link...I appreciate it . I found it an excellent reference.
    OK . What if I run the furling “ main sail “ from the top of the mizzenmast to just aft of where the main mast exits the deck. Let’s say I keep the mizzenmast at 42’ deck stepped. I haven’t scaled this out on the original drawings. I will and see what it looks like. I’m just intrigued by the idea that Bruce King used carbon fiber wishbones to “overcome” the weight issue. I’m very curious as to how everything was built and attached to the main spar.
    I hope this discussion might let us all take an additional look at this rig.
    For example. Maybe you don’t need a spar but some kind of batten or battens. Maybe the sail makers on the forum have new ideas. I’ve never sailed on a wishbone ketch.
    Anyone with first hand experience or additional references ?
    Thank you all.
    Curious manatee
     
  3. bajansailor
    Joined: Oct 2007
    Posts: 386
    Likes: 63, Points: 28, Legacy Rep: 37
    Location: Barbados

    bajansailor Marine Surveyor

    This wishbone ketch apparently is a 57' Benford design (although she looks longer than 57' to me)
    Lungta...57' Benford ketch with a wishbone sail plan. Sailed from Portland, OR to Long Beach, CA 10/12. Vessel is currently in Mexico… | Love To Sail | Sailing ships, Boat, Sailing https://www.pinterest.com/pin/567031409330838276

    And here is a 54' wishbone ketch for sale in Australia - although the photos showing the rig are not very good.
    Custom 48' Classic Wishbone Ketch For Sale | Ensign Yacht Brokers https://ensignbrokers.com.au/ensign/yachts-for-sale/used/sail-monohulls/custom-48-classic-wishbone-ketch/234372/

    Re Bruce King's wishbone ketch, I guess this must be Chanty?
    Here is a video of her - but no shots of her sailing sadly. It does show the two masts sitting on horses on the ground though.

    Tad Roberts (who posts on this Forum) was involved in her design -
    Tad Roberts, Professional History https://www.tadroberts.ca/about/history
    Attached is the only photo I could find of her sailing.
    Chanty.jpg
     
  4. Rumars
    Joined: Mar 2013
    Posts: 305
    Likes: 78, Points: 28, Legacy Rep: 39
    Location: Germany

    Rumars Senior Member

    Manatee, I think an aging sailor with a big boat should focus his atention on powered winches first, furlers second. Depending on how you feel about it you can go in-mast furling, in-boom furling or conventional stackpack with roller bearing cars. Regardless of what you favour, powered winches (electric or hydraulic) are a necesity.
    What you don't need is fighting to control a wishbone gaff. It was a nice invention at the time that did not really became mainstream, and it is not necessary now. A modern sailplan would use full batten sails with square or eliptical tops and achieve the same sail area with shorter masts or booms. All possible courtesy of roller bearing batten cars and powerfull self-tailing winches. Truth be told a modern design would use only one mast. Just to give you an ideea of what modern gear is capable of, the whole 1630 sq. ft. sail area on four sails that Brewer specified for your boat is smaller the single mainsail on an Open 60, and that is controlled with manual winches.

    If you are designing a new rig anyway, why ketch? An equal mast height schooner will give you better sail proportions, after all that's what it was invented for.

    Here is an article about a boomless trysail rig that might interess you. Boomless Sailing - MySailing.com.au http://www.mysailing.com.au/cruising/boomless-sailing
     
  5. Manateeman
    Joined: Oct 2019
    Posts: 31
    Likes: 1, Points: 8
    Location: St. Mary’s Georgia

    Manateeman Junior Member

    Thank you both. I built a Bruce King design 31’. We tried two jibs with two poles and were very surprised how nice she ran downwind. These were on a bowsprit about four feet forward of the stem. We switched to a staysail at the stem and a big jib at the end of the bowsprit. My wife just loves the ease of motor sailing with the staysail alone. I just never thought about an alternative way of using two poles. It’s a very interesting idea. I enjoyed the article about boomless designs.
    Not sure about power winches...just a personal fear...long silly story.
    Again, my thanks. Lots of talent here and a lot to think about.
    Mark the manatee
     
  6. Rumars
    Joined: Mar 2013
    Posts: 305
    Likes: 78, Points: 28, Legacy Rep: 39
    Location: Germany

    Rumars Senior Member

    Here is another conversion to staysail schooner, this time with a homemade roller furling forecourse. CHANGE OF RIG http://schooner-britannia.com/change_of_rig.html

    You could also go for a bald headed gaff rigged schooner with short gaffs (single hailyard). Kasten seems to like them: Defining The Ideal Sailing Rig http://www.kastenmarine.com/gaff_rig.htm

    You can also go staysail schooner and simply forget about a the fore-trysail and it's wishbone and sail without it. In light weather you either motorsail under main-staysail or you could have a trysail or gollywobler made out of spinnaker cloth and use it to give you a boost.

    Downwind you have options: furling squaresail, twin headsails, asymetrical spinnakers on furlers (two of them, since you have two masts).

    You could also consider an electric winch handle, either purpose made or battery right angle drill. That is going to be cheaper than powered winches, and if it breaks you are back on grinding duty until you replace it.

    Basicly what you need is to pay a designer for his time. You explain what you want, can do, are willing to spend, and he works out the best option. For example a boatbuilder that can weld Al should not play with unapropiate sh masts, buying and splicing the correct extrusion and fitting spreaders is cheap enough.
     
  7. Manateeman
    Joined: Oct 2019
    Posts: 31
    Likes: 1, Points: 8
    Location: St. Mary’s Georgia

    Manateeman Junior Member

    Hi. I have a halyard exit hole right where the mast partners are located ...I’m not too worried about the other halyard exit holes which will now be below the deck level. I’ve thought the easiest solution is to TIG weld them. I have a friend who build racing air planes who suggested we cover the mast from heel to about a foot up above the partners with biaxial set in epoxy. Comments?
    Thank you.
     

  8. rnlock
    Joined: Aug 2016
    Posts: 72
    Likes: 4, Points: 8, Legacy Rep: 10
    Location: Massachusetts

    rnlock Junior Member

    The epoxy may not stick very well to the aluminum unless you get really fancy with the surface prep. I suppose if it was strong enough by itself, and went all the way around, that might be ok. At least if you sail at the same temperature that you glued at!

    Even with a small HAZ, isn't part of it going to be quite weak compared to the rest of the mast?

    BTW, if you shrink the rig, keeping the same proportions, the heeling moment will be proportional to the height of the mast squared, and therefore much less when its shorter.

    Seems to me that the easiest option might just be to get power winches that are really reliable. As a back up, do they make man powered winches which are geared down more than most? Pedal powered winches?
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.