modifying a staysail schooner

Discussion in 'Sailboats' started by drewcathell26, Feb 3, 2009.

  1. drewcathell26
    Joined: Feb 2009
    Posts: 17
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: albany

    drewcathell26 Junior Member

    Is is possible to modify a staysail schooner to a gaff schooner? If it is possible does it make sense in terms of performance? I am not trying to push the schooner beyond what is reasonable for a limted rig. I have an opportunity to purchase a staysail schooner but have always loved a gaff. If it is reasonable and worthwhile who would I speak with to design the changes?

    thanks

    drew
     
  2. Tcubed
    Joined: Sep 2008
    Posts: 435
    Likes: 18, Points: 0, Legacy Rep: 318
    Location: French Guyana

    Tcubed Boat Designer

    Staysail schooners can have a number of different arrangements.

    Depending on the exact arrangement , geometry , mast placement etc changing to gaff can result in substantial improvement in performance. But it all depends...

    Basically your question is too vague to be able to answer with any kind of precision as is. You need to post some pictures or post a sail plan, so i could determine what your options are. Also you need to specify what your specific objectives would be.

    I have many years of experience as a rigger on both traditionally rigged and modern boats. I have also aerodynamic training, so i believe i might be the relevant person for you.
     
  3. robherc
    Joined: Dec 2008
    Posts: 432
    Likes: 5, Points: 0, Legacy Rep: 102
    Location: US/TX

    robherc Designer/Hobbyist

    OK, I know this is completely-off-topic here, but (in light of your experience) what are the main advantage(s)/disadvantage(s) to adding reverse-marconi sails to a multi-masted marconi/bermuda rig (filling in the gaps between the lower/upright marconi sails & the following mast)?
     
  4. Tcubed
    Joined: Sep 2008
    Posts: 435
    Likes: 18, Points: 0, Legacy Rep: 318
    Location: French Guyana

    Tcubed Boat Designer

    A 'reverse marconi' foresail to fill the gap between main staysail and foremast on a staysail schooner without a boom is extremely inefficient as the sheet has nowhere to go but to the mainmast, ie on the centreline of the boat. This creates a very 'cupped' airfoil section to the upper part of that sail. This in turn creates a very large heeling moment , especially as it is so high up, and a weak forward force component. Furthermore, it will have reverse twist and/or inboard pointing leech . Additionally this shape will backwind the main staysail and mainsail.

    This problem is inherent due to the sheeting angle.

    These sails therefore require a boom or wishbone boom in order to be somewhat acceptable.

    Even with the boom though it is not so optimum as all these sails have a triangular planform which is a drastic departure from the optimum eliptical planform. Also , whenever a sailplan is so heavily subdivided there is loss of efficiency at high angles. Many slots will delay the point of stalling, but i tend to think that upwind is always the point of sail which should take optimization priority.

    This is a very deep and fascinating subject, but let me stop there for now.
     
  5. robherc
    Joined: Dec 2008
    Posts: 432
    Likes: 5, Points: 0, Legacy Rep: 102
    Location: US/TX

    robherc Designer/Hobbyist

    OK, thanks...your opinion seems to be pretty much agreeing with my calculations that they'd be farily inefficient, and disastrous in the way of heeling moment. I just wanted to get an "expert opinion" as I'm seeing them used on several "modern" rigs...so I wasnted to know if there were benefits that I wasn't seeing, or if they were just that poorly thought out ;)
     
  6. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 471, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Simply put, a staysail schooner will perform better up wind then a gaffer, but down wind the gaffer has an advantage given both fly working sails. This is especially true if the gaffer has an overlapping foresail.

    Generally the staysail schooner is a handier rig to operate, particularly if short crewed, then a gaffer. Many successful ketches and schooners have utilized a wishbone mule. Sheeting angles can be difficult, but carefully thought out rigs can work exceptional well.

    It's unlikely you'll find a reasonably modern design, staysail schooner that wouldn't require considerable effort and expense to convert to a gaffer. The mainmast will probably have to move, possibly the fore as well. This means major surgery to the yacht's hard points (steps, chain plates, torsion rods, plus deck and interior modifications, etc.) to suit the new rig.
     
  7. alberto88
    Joined: Jan 2009
    Posts: 17
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Chonburi

    alberto88 Junior Member

    just can use a full batten big roach main to increase sail area up high, and acheive the look of gaff, with better performance?
     
  8. drewcathell26
    Joined: Feb 2009
    Posts: 17
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: albany

    drewcathell26 Junior Member

    Thanks for the quick responses. I'll try to be clearer. The attached photo is of a Cheoy Lee staysail schooner which has the very reversed marconi ric that Tcubed mentioned. I am not a designer but it seemed to lack the abilty to form an effective shape to me as well.

    My goal is to leave the masts where they are, change the main and fore to gaff rigs and add topsail above each.

    I haven't tried to attach a photo before so I am not sure how this will work.

    Let me know if you need further information.
     

    Attached Files:

    Last edited: Feb 4, 2009
  9. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 471, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Nope, it can't be balanced well with the masts in those locations and gaffheaded sails installed. The CE would move considerable aft of it's current location and the yacht would go "lee" on you.
     
  10. drewcathell26
    Joined: Feb 2009
    Posts: 17
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: albany

    drewcathell26 Junior Member

    I was hoping to not only keep the masts in place but keep the center of efforts close to the same as well. The following is a poor quality photo shopped version of what I had in mind. In the photo the center of effort seems to remain the same. I have no idea if the sail shapes are appropriate or not.
     

    Attached Files:

  11. Tcubed
    Joined: Sep 2008
    Posts: 435
    Likes: 18, Points: 0, Legacy Rep: 318
    Location: French Guyana

    Tcubed Boat Designer

    I think you ' re thinking pretty logically but you still haven't stated what your precise objectives are in doing rig changes.

    Seeing the first picture , it is in fact possibly one of the worst examples of a mule i have yet seen.

    That boat is quite small and does not need the sailplan so divided.

    I agree that moving mast positions is suddenly a lot more work, so would avoid such drastic changes.

    It is important to realize that if the center of effort is lowered it must also shift aft to achieve the same balance, but will be less affected by heel.

    You seem to anticipate shortening and/or lengthening spars.

    I would recommend; leave the foremast same length. Lengthen bowsprit and cut down mainmast. Have only a main tops'l , set on its own spar and made quite generous. I would also make the foresail overlapping, since the masts are quite close together. You probably don't want to mess with the jibs but if you had one self tacking jib instead it would be more efficient and you would end up with only the foresail to deal with when tacking.

    I disagree with PAR's last post.

    I also, PAR, do not understand how someone of your authority can come up with such a generalization as <<<Simply put, a staysail schooner will perform better up wind then a gaffer, but down wind the gaffer has an advantage given both fly working sails.>>>. What aerodynamic reasoning did you use to make that claim?
     
  12. Tcubed
    Joined: Sep 2008
    Posts: 435
    Likes: 18, Points: 0, Legacy Rep: 318
    Location: French Guyana

    Tcubed Boat Designer

    Here is a very quick and crude picture of what i'm imagining spur of the moment. Needs refining obviously. The foretriangle could just as easily be jib and stays'l instead. the boom could be a foot or two longer two to get some more area low down. Cutting the masts removes weight high up which does wonders to righting moment , not to mention windage.
     

    Attached Files:

  13. timothy22
    Joined: Feb 2008
    Posts: 95
    Likes: 6, Points: 0, Legacy Rep: 76
    Location: florida

    timothy22 Junior Member

    You can spread out the expense a little by just going to the gaff foresail, leaving the main as is except for removing its forestay and adding a spring stay. Several great old schooners were designed this way by John Alden and others. This will give you half the look you are going for, at considerably less than half the expense. Then you can be sailing whilst saving up to rerig the main and fore triangle.
     
    1 person likes this.
  14. Tcubed
    Joined: Sep 2008
    Posts: 435
    Likes: 18, Points: 0, Legacy Rep: 318
    Location: French Guyana

    Tcubed Boat Designer

    That is a very good alternative also.
     

  15. drewcathell26
    Joined: Feb 2009
    Posts: 17
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: albany

    drewcathell26 Junior Member

    Thanks again for all the good ideas. Doing the changes in stages would be a real help.

    As to my real objective... I love the look of a gaff rigged schooner. I have seen staysail schooners, Cherubini come to mind, that seem to have a real grace under sail. The schooner I am looking at does not seem to fit in that category. That may be a result of what you describe as "the bad mule plan". I am aware of the old saying that it is nicer to sail near a schooner than on one. I know they typically don't perform as well as other rigs. That being said I am willing to tolerate that loss of speed. I have sailed for years on boats that were not racing boats and have enjoyed the speed at which I sailed. At times right past larger, faster boats. There is nothing about the staysail rig as currently photographed that appeals to me in appearance or function.

    I realize the boat is small for a schooner rig but I am trying to keep the size manageable (even if I am not keeping the rig manageable). These questions are simply a last ditch effort at creating my dream boat before I give up and buy a great 37' cutter.

    Adjusting the spars, sail and rigging is a completly acceptable list of tasks. Particularly if they can be done in stages as timothy22 suggested.

    Regarding the comment suggesting increasing the roach I am not a fan of roach or battens at all and would rather have a leech line if the sails are to be new or cut.
     
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.