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Freedom 40 Cat Ketch Junk Rig Conversion

  • 20 Jan 2017 17:34
    Quote
    Reply # 4559217 on 1424184
    Anonymous member

    Cough, cough, cough...  stirring up layers of dust of embarrassing from several years of inactivity on this project.  I was contemplating hiding from the past and starting with a new thread romantically named "Raven's Wings".  But there is such good info from everyone in this original posting so... here it goes, facing the music, Round 2.  

    Some of my original design criteria still apply, and maybe the cumulative knowledge of everyone can make most of them happen.  To familiarize the reader…  the current sail area on our boat is around 72.6 sq meters (SA/D ~ 17).  We are slow in light winds and maybe we are slow anyway  :).   In any case, sailing upwind we use one reef in 15 to 20 knots, and single reef both sails above 20 knots. Sails are baggy and blown out (1994 vintage) and there is no good way to truly flatten them instead of reefing.  Also, currently there is little gear or tankage (200 gal water, 100 gal diesel when filled) so the boat is likely more tippy than when set up for cruising.  With that in mind, this is where I am at regarding sail design:

    1.  Equal sized sails:  Starting with the front sail - a 10 deg sheeting angle to the 5th batten, constraining the sails to a straight luff, limits the boom/batten length to about 4 to 4.3 meters (depending on overlap) with the 5th batten approximately 8 meters up from the deck. Fitting a sail within those parameters, and if the same sized sail is used on the aft mast, the combined sail area ranges between 73 to 80 sq. meters (and the AR is  2.5 to 2.75).  For the smaller size, the SA/D ratio would be the same as it is presently at 17 or increase to 18.7 with the sail area increase by 1.1 if the larger possible setup is used. Either way, the CE moves forward around 65 cm from its present location.  I have no sense if this is a lot? There may be some advantages in ease of construction with only one sail size.  Then again maybe they are two different sails if the camber position is varied for each on. But the possibility of sheeting the aft sail to the transom may free up the boomkin for a windvane.  Or removing the boomkin may decrease our length on deck and save on marina fees.

    2.  Unequal sized sails.  There is room to make the aft sail larger.  The sail area can be increased to 1.2 or so of the existing and the SA/D then goes to an exciting 20.4.  This can be accomplished by making the aft sail larger and using the existing boomkin on the transom as a sheeting point.  A 10 deg sheeting angle gives room for a boom/batten length of 5 meters or even a bit larger.  The CE still moves forward of the original, but only by half - 30 cm or so.  IN the end, total sail area – if the front is at 40 sq. meters - can be as much as 86 sq meters.

    3.  Sheets/Dmin:  We would like to stay with 3x1 sheets, possibly configured like Fig. 4.35 in PJR.  This may have sufficient anti-twist.  In any case, a Dmin of 2P is about all that may fit.  Other options may be of consideration.  If the new sails are indeed as large as 1.2 of the current sail plan, reefing may be more common than now.  This may justify a single, detachable lower span  sheet that is used in light winds when managing a total of four sheet could be easier.  The upper spans may then possibly be configured as in Figure 4.10.  The Dmin would drop to 1.25P.

    4.  Camber.  Somewhere around 8% seems to be the going number.  But still on the fence – not whether the sails will have some –  but how to induce it.  Barrel, broad seams, shelf, hinged battens or some combination.   

    Maybe this is enough download for  now and for getting some input.  I have posted several design ideas in an album .  Drawing are in QCad and I will try and set up a DropBox site for the original files.

    Thanks so much,

    Erik and Evi
  • 06 Nov 2013 21:45
    Quote
    Reply # 1429325 on 1427531
    Deleted user
    Erik and Evi Menzel Ivey wrote:
    Brian - thanks for all the technical specifications. They will be helpful.  Question - looking at the photo of your sail, it appears it has some luff hollow?!  If true, do you know the purpose?  

    Also, how do you stow your sheets while sailing or not in use?  Coils?

    Erik

     

    Re the hollow - merely an attempt to produce a more interesting shape on a schooner. Most schooner luffs end up straight because often, as in our case, the masts are a shade too close together. Not spotted any disadvantages yet.


    Our mainsail sheets are stowed in coils on hooks that stick out from the central pole of the main's boom crutch. The central pole is clipped to the top of the wheel pedestal. The foresail sheets and all the other lines are in bags at the front of the cockpit. In our previous boat, a Sunbird 32, everything was stowed in cockpit lockers with lift up lids, a system that worked well unless someone was sitting on them, so sheets were often just dumped on the cockpit floor. See PJR for some ideas.
    Last modified: 06 Nov 2013 21:45 | Deleted user
  • 06 Nov 2013 02:33
    Quote
    Reply # 1428654 on 1428292
    Anonymous member
    Jonathan Snodgrass wrote:
    Kurt Jon Ulmer wrote:
    Jonathan Snodgrass wrote:Kurt Jon Ulmer wrote:

    With 5:1 halyards, I can often sheet both sails with one hand in light wind, llke reins on a horse.
    Kurt
    Do you really mean "halyards" or should that be sheets?
    Jonathan

    [I've edited my original post. Thanks! Sometimes I make the same mistake in the cockpit...] KJU


    But at least you now know that someone has read carefully what you have written!  jds
    Indeed! Most gratifying!
    KJU
  • 05 Nov 2013 18:54
    Quote
    Reply # 1428292 on 1427546
    Anonymous member
    Kurt Jon Ulmer wrote:
    Jonathan Snodgrass wrote:Kurt Jon Ulmer wrote:

    With 5:1 halyards, I can often sheet both sails with one hand in light wind, llke reins on a horse.
    Kurt
    Do you really mean "halyards" or should that be sheets?
    Jonathan

    [I've edited my original post. Thanks! Sometimes I make the same mistake in the cockpit...] KJU


    But at least you now know that someone has read carefully what you have written!  jds
  • 04 Nov 2013 19:23
    Quote
    Reply # 1427635 on 1424184
    Anonymous member
    Hi Erik & Evi,

    Round battens and round or fat-oval yards. I agree with David Tyler. Our square booms are never in the orientation they're 'supposed to be' in.

    Loads? Good luck trying to predict the direction of greatest load on a dancing spar - PJR's scantlings give a tested guide, and modern materials allow beefing those up without getting overly heavy. 

    Stronger spars and sail corners should be used if adding camber - my thoughts on this are in the 'Merits of Flat-Cut Junk Sails' article.

    Fig 4.28 - Good to use this span lowest, where advantage for Dmin is greatest. I wouldn't turn the sheetlets upside down. 'Equal power' isn't quite equal, and better to put more power higher against twist. Also, I don't think it'll furl the same with those sheetlet lengths if you flip it.

    5 feet isn't too large a panel at the leech. Ours exceed that in the 4th panel up. Only our bottom 3 panels are parallelograms - the battens rise at higher and higher angles to the leech above there.

    Flaking rope tails into buckets / boxes has worked out best for us.

    Cheers,
    Kurt
  • 04 Nov 2013 17:49
    Quote
    Reply # 1427559 on 1427531
    Anonymous member
    Erik and Evi Menzel Ivey wrote:

    Some more technical questions - Yard loads:  I was surprised to read that some people experience "sideways" bending of the yard rather than "vertical bending".  Hope that is clear.  Without any sheets attached to it, can somebody  explain the loading in that direction.

    If one is going the route of Aluminum battens - round is easier to obtain, but wouldn't a rectangular profile be more efficient - i.e. similar to the yard above - aren't the forces in the vertical plane larger - such as sheet loads, HHP, THP?

    OK, cheers from sunny California.

    Erik
    The problem is that the yard and battens try to rotate themselves to the orientation in which they find it easiest to bend. An excessively deep and narrow yard or batten just kind of falls over sideways and bends vertically that way. I've calculated the stiffness and strength of square, rectangular and 'diamond' battens, and the sums always come out worse than for a round tube. I'm convinced that a round tube is the best shape for both, whatever it's made from.
  • 04 Nov 2013 17:31
    Quote
    Reply # 1427546 on 1427358
    Anonymous member
    Jonathan Snodgrass wrote:Kurt Jon Ulmer wrote:

    With 5:1 halyards, I can often sheet both sails with one hand in light wind, llke reins on a horse.
     
    Kurt
     
    Do you really mean "halyards" or should that be sheets?
     
    Jonathan

    [I've edited my original post. Thanks! Sometimes I make the same mistake in the cockpit...] KJU
  • 04 Nov 2013 17:12
    Quote
    Reply # 1427531 on 1424184
    Anonymous member

    [Webmaster edit: Where Erik writes 'Berry' he means Barry Stellricht'.]

    The Ketch looks like a Schooner….  

    Well, after reading comments, getting a better understanding of the recommended sheeting angles, and continuously struggling with Dmin, I’ve dropped the requirement of having identical main and mizzen sails and the sail plan has “evolved” into a schooner.  Aesthetically just fine by me.  I have posted two versions  along with some of the technical details that Berry’s Excel sheets so easily calculates.  A BIG THANKS TO BERRY FOR PUTTING IT TOGETHER.  The worksheets are a very easy way to try out different configurations, although some knowledge or willingness to learn Excel is required. 

    The little sailing we’ve done with the boat has shown it to be underpowered in less than 12 to 15 knots.  If the sails were not blown out, she should handle the nominally 790 sq ft in 20 to 25 knots, although it would not be comfortable cruising at that upper range.   So there is a need for more sail area and I’ve been shooting for +1000 sq. ft.

    I’ve come up with two schooner designs, the major difference being  seven or eight panels, and an increase in sail area on the latter from 1000 to 1143 sq ft.  I’m guessing if we would do the larger sail plan, we would be sailing with two reefs 50% of the time in the SF Bay.   It is also a different sheeting  setup and steeper angles.  (I should note that we have a 18 hp Sabb diesel with a pitching prop – truly and auxiliary engine).

    So, unless there is a lot of encouragement, maybe 7 panels is OK.  Some general specifications of the present design are:

    Main Batten and Panel Dimensions (ft)

    Len

    Luff

    Leech

    Boom (12 deg angle)

    15

    Batten 2

    15

    4.0

    4.0

    Batten 3

    15

    4.5

    4.5

    Batten 4

    15

    5.0

    5.0

    Batten 5

    15

    5.0

    5.0

    Batten 6

    15

    5.0

    5.0

    Batten 7

    15

    0.5

    7.0

    Yard

    15

    0.5

    7.0

    Yard Angle

    62.9 deg

    Sling Point (%aft)

    45%

    P/B Ratio

    0.27

    Sail Area

    453 sq ft


    Mizzen Batten and Panel Dimensions (ft)

     

    Len

    Luff

    Leech

     

    Boom

    (12 deg angle)

    17.5

     

    Batten 2

    17.5

    4.0

    4.0

     

    Batten 3

    17.5

    4.5

    4.5

     

    Batten 4

    17.5

    5.0

    5.0

     

    Batten 5

    17.5

    5.0

    5.0

     

    Batten 6

    17.5

    5.0

    5.0

     

    Batten 7

    17.5

    0.5

    8.1

     

    Yard

    17.5

    0.5

    8.1

     

    Yard Angle

    62.9 deg

    Sling Point (%aft)

    45%

    Aspect Ratio

    2.24

    P/B Ratio

    0.23

    Sail Area

    547.0

    Brian - thanks for all the technical specifications. They will be helpful.  Question - looking at the photo of your sail, it appears it has some luff hollow?!  If true, do you know the purpose?  

    Kurt - thanks for checking in and the references.  I'll study both those sail plans.  As you can see, the lower panels are smaller in order to take advantage of your sheeting setup.  And then I do increase to P = 5ft for the upper ones.  Is that too large? I was wondering - in PJR for the Fig 4.28 sheeting arrangement, it seems like one can either have the lower sheet at 2P and the upper at 2.5P or the flip.  Angles change slightly, but the final length is shorter if the upper is at 2P and the lower at 2.5P.  Any thoughts?

    Also, how do you stow your sheets while sailing or not in use?  Coils?

    Annie - thanks for the  welcome and the pep talk.  :) I am concerned about handling and performance... Where we are presently day sailing, being able to point is important.
    And I would love to take the boat on a couple of the more friendly races we have here.

    Some more technical questions - Yard loads:  I was surprised to read that some people experience "sideways" bending of the yard rather than "vertical bending".  Hope that is clear.  Without any sheets attached to it, can somebody  explain the loading in that direction.

    If one is going the route of Aluminum battens - round is easier to obtain, but wouldn't a rectangular profile be more efficient - i.e. similar to the yard above - aren't the forces in the vertical plane larger - such as sheet loads, HHP, THP?

    OK, cheers from sunny California.


    Erik

     

    Last modified: 06 Nov 2013 21:34 | Deleted user
  • 04 Nov 2013 11:16
    Quote
    Reply # 1427358 on 1424184
    Anonymous member
    Kurt Jon Ulmer wrote:

    With 5:1 halyards, I can often sheet both sails with one hand in light wind, llke reins on a horse.
     
    Kurt
     
    Do you really mean "halyards" or should that be sheets?
     
    Jonathan
  • 03 Nov 2013 18:17
    Quote
    Reply # 1426947 on 1424184
    Anonymous member
    Hello Erik & Evi,

    You're obviously approaching this rig change with intelligence and attention to detail. It's going to be good!

    With 5:1 sheets, I can often sheet both sails with one hand in light wind, llke reins on a horse. There is a lot of length in the sheets, but it's useful. Sometimes I unsheet the top batten for a 4:1 system, by unhitching the end of the sheet from its batten and tying it to the deck (for coastal and light conditions.)

    You noticed the changing panel size I used in mehitabel's sails. It does help the Dmin, which lowers the sail a little, and also makes the first reef a 'balancing' adjustment. The other change-from-PJR that I wrote about, apparent in the upper panels, enhances fan camber - I think it's also worthwhile.

    You've probably considered flat-cut sails and decided to use some form of added camber instead. I'll only suggest moderation and a bomb-proof top 2 panels, cut flat if you intend open ocean sailing.

    With perfect foresight, I would have left another metre on the foremast, for the reason Brian mentioned, of allowing another (small, lowest) panel in the foresail. Leaving your masts as they are seems best to me.

    If you haven't given Paul Thompson's 'La Chica' and 'Aphrodite' rigs a study, you might gain some ideas there.

    Best of luck.

    Cheers,
    Kurt
    Last modified: 04 Nov 2013 17:29 | Anonymous member
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