hatch replacement partners? flat sail vs camber?

<< First  < Prev   1   2   3   4   Next >  Last >> 
  • 23 Dec 2015 22:23
    Reply # 3716595 on 3712908
    Deleted user

    Thanks for all the fantastic info! I had a realization yesterday after re-reading pjr, Arne's docs, and C and SJ docs for the billionth time. I think I now have a working understanding of how the rig works, how to determine the proper mast position, and how it integrates to my boat effectively.

    I have decided I would like to try and avoid going through the hatch unless necessary, and if I have to, not more then a 6 degree forward rake.

    I am very interested in the Split cambered junk, because it seems to have a lot less rigging then a Cambered PJR style like Arne does.  The thing I really like about going the route of Arne, is that if I don't like the camber, it would be a lot easier to just convert it to a standard flat PJR rig.

    I have also determined that the construction method of the partners and mast step is open to full interpretation, long as the pieces are stout and overly strong.

    I finally understand what PJR is trying to communicate! Now I am off to design many different paper variations of the sail plan to determine what rig will work most effectively with the available mast locations. Waiting on my replacement copy of Van Loan's book to compare the rig details with all the others!

    A Brief summary of conclusions: (please point out if they are wrong!!!)  

    The PJR flat sail and following the PJR directions is a proven, low cost, simple, reliable, and seaworthy system. Any deviations from the PJR flat sail plans will induce issues that need to be solved and require more tweaking, maintenance, rigging, and cost. This is a tried and true proven system, nothing experimental.

    PJR Camber sail- This will cost more, require more attention to stresses, more work, has developed a lot since its inception. Can be a seaworthy rig, but requires more fore thought, planning, and might not be as reliable or safe as the flat PJR if one is caught in extremely heavy weather. Pros- Windward performance, quicker then I can paddle a canoe. More power in the sails.

    Cambered Split Junk rig- less rigging required then PJR Camber, balanced, seems like a great rig. To be honest, I feel that a properly built PJR Camber and proper split cambered rig may perform very similarly, I am not convinced the split panels provide a drastic boost in performance over a well made non split sail. I don't know, It would be interesting if wind tunnel results existed. I think there are other variables at play such as drag from the mast ect. On the other hand having the split panels seems to make sail construction easier, if you understand how to make the shelf foot jibs, and the round a broad seam mains. I am still confused on the whole S and CJ  sail making procedure, so if some one can link me to some photos, I will probably be able to figure it out. I have to do more research on how people using this rig in the open ocean feel about it. 

    You can create camber by force or design into the battens, or you can add camber in the fabric.

    I still have to review the van loan work and I still no nothing about the fan sails. More work to do! After I play with and figure out each different variation on the sail plan, I will be able to choose the one that makes the most sense to my boat and needs. 

    Happy Holidays!

  • 23 Dec 2015 13:27
    Reply # 3715867 on 3712908
    Anonymous member (Administrator)

    I agree with Slieve.

    In fact, I would not want to fit a JR mast in the BM mast position for another reason: The original mast step (if deck-stepped) would have to go, and the partners would anyway have to be re-made to take the stouter JR mast. If you, for some reason, some day would re-convert the boat back to Bermuda, you would then have a much bigger job ahead of you.

    However  -  IF the BM rig is a typical partial rig with the mainsail being twice as big as the jib, you may possibly get away with not moving the mast, in particular if you go for a JR with big balance, like Slieve’s split JR, or like the sails on Paul J Thompson’s La Chica. In fact, the first year I sailed my 18’ dinghy, Broremann, with a JR, I just borrowed a mast and planted it in the original position (see here). This was 250mm aft of the position I had planned. I kind of got away with it, thanks to the big rudder, but there was a noticeable increase in weather helm over that with the Bermuda rig.

    Later, in 2011 I fitted a new stouter mast in the designed position, and was much happier with that (see here).

    Cheers
    and Merry Christmas to everyone,
    from Arne

     

    Last modified: 23 Dec 2015 16:01 | Anonymous member (Administrator)
  • 23 Dec 2015 12:04
    Reply # 3715802 on 3712908

    I don't know where this myth has come from, but Poppy's junk mast was moved forward from the Bermudan position. I've yet to see a two sail Bermudan rig mast that does not have to be replaced further forward.forward.

    Merry Christmas,

    Cheers, Slieve.

  • 23 Dec 2015 08:34
    Reply # 3715541 on 3712908
    Have you considered a Split-Junk-Rig as an option?>>> I believe Slieve McGalliard got away with not having to move the mast position on his boat "Poppy". Might be worth checking out.
  • 23 Dec 2015 02:31
    Reply # 3715049 on 3712908

    Some suggestions and thoughts....  post a drawing showing the Bermuda rig overlayed with the new junk rig.   There are some nice odrawings of the Colimbia 26 MII cross section that may help people provide more feedback.  I am guessing you are trying to preserve your v berth and prevent having to cut another hole in the deck for the mast.   In any case,  10 degrees may be a lot of rake.  Whereever you decide the mast should endup,  do a quick cardboard mockup and see how it affects your v berth,  including getting in and out and sleeping.   Going through the hatch will eliminate the hatch as a source of light and ventilation... unfortunately most things on a boat are compromises.

    Exterior plywood,  sealed in epoxy should work.  Rather than planing it to some angle. maybe cut the hole at the angle of your rake -  for small amounts of rake it is possible that you can cut the hole  straight and cast the partners or use the more traditional wood wedges to get your angle.  


    Erik

  • 22 Dec 2015 21:39
    Reply # 3714774 on 3714431
    James Hleba wrote:

    Hello and thanks for the input!

    I have been going through this site digging into all the great content. I am adjusting to the layout and am now figuring out how to navigate more effectively. The more I read on this site, the more open to interpretation building the rig seems to be. I am definitely confident building the partners and mast step are safely DIY doable.  I think the 10 degree rake towards the bow is necessary if I end up going the hatch insert to preserve as much functional space as possible in the V-berth. I still have to figure out the pro's and con's of having the rake. It complicates things in building the partners.

    Maybe I can make a flange from several layers of plywood glued and bolted together, and take it to a cabinetry shop and have them plane the bottom layer at a 10degree angel prior to mounting it to the plywood hatch insert.   

    If any of you can point me towards the advantages and disadvantages of a raked mast, it would be fantastic. PJR has a very short sparsely detailed section on it.

    Your idea for making the flange from plywood glued together makes sense.  Use epoxy and don't put in any bolts, or at least don't put in any bolts until the cabinetry shop has run it over their plane, or whatever tool they choose to use.  They won't appreciate having them in the way!

    A drawback of a steeply-raked mast is that it is more difficult to climb up and down because gravity makes you swing around to the front.  That's the only drawback I can think of.  

    Last modified: 22 Dec 2015 21:40 | Anonymous member
  • 22 Dec 2015 18:30
    Reply # 3714431 on 3712908
    Deleted user

    Hello and thanks for the input!

    I have been going through this site digging into all the great content. I am adjusting to the layout and am now figuring out how to navigate more effectively. The more I read on this site, the more open to interpretation building the rig seems to be. I am definitely confident building the partners and mast step are safely DIY doable.  I think the 10 degree rake towards the bow is necessary if I end up going the hatch insert to preserve as much functional space as possible in the V-berth. I still have to figure out the pro's and con's of having the rake. It complicates things in building the partners.

    Maybe I can make a flange from several layers of plywood glued and bolted together, and take it to a cabinetry shop and have them plane the bottom layer at a 10degree angel prior to mounting it to the plywood hatch insert.   

    If any of you can point me towards the advantages and disadvantages of a raked mast, it would be fantastic. PJR has a very short sparsely detailed section on it.

    Has anyone tried to make a wood form mast step, have it about an 1 1/2 in larger in diameter then the mast. Drill a bolt hole to put a mast bolt, rub the wood form with release compound and pour cement about 6 to 8 in deep? I have cemented flag poles into the ground before and they are still holding well. Just musing any how.

    Happy Holidays!

  • 22 Dec 2015 07:49
    Reply # 3713613 on 3712908

    Hi James,

    We had a Bermudan rig with ~720sq.ft. and gave our junk rig ~810. No regrets, because of the easy reefing and relatively less drive (from flat sails) in light air.

    Our sails are flat-cut. There's no consensus about flat vs. cambered sails as to which is 'better,' but a suggestion some of us accept is that cambered sails are well-suited to coastal, moderate wind and chosen-weather sailing, while flat-cut sails are well-suited to open ocean, passage-making and heavy weather sailing. There's heaps to read about all aspects of the rig, in the newsletters and articles hereabouts.

    Best of luck with your rig!

    Cheers, Kurt

  • 22 Dec 2015 00:17
    Reply # 3713198 on 3712908

    I used Yeong style mast step and partners built up using fibreglass in a conversion some time ago. This must be the easiest technique for a mast that is not perpendicular to the deck, or in your case, a sturdy plywood infill in the hatch opening.

    When I sold that boat, the new owner took it away on a truck. When he tried to extract the mast, it wouldn't come out and the crane lifted the front of the 3 ton boat off the ground. My mistake: I should have bored an air hole in the step to prevent that vacuum from forming.

    As for your question on flat vs camber, that must be one of the most hotly debated subjects in this forum. There are powerful arguments on both sides. Good luck.

    Happy winter/summer solstice to all and fair winds for 2016.


    Last modified: 22 Dec 2015 00:32 | Anonymous member
  • 21 Dec 2015 18:42
    Message # 3712908
    Deleted user

    I hope all of you are staying warm and dry during this holiday season!

    After much head scratching about mast placement , how to mount the step, where to put the mast hole ect, my copy of Practical junk rig has lent me some clues. I think I may finally see the light! I also, think I may be able to DIY this job, with the assistance of a local yard to step the mast.

    I noticed according to the Practical Junk rig, that PIlmer used an insert from where the hatch used to be to avoid having to cut the deck up for reinforcement. What other boats has this been done on? Anybody use a hatch insert and also set the mast angle at 10 degrees? I am not having luck finding any details about other people who have use a hatch insert for the mast partners, so if anybody out there can share some links with me it would be much appreciated.

    I would like to run an aluminum flag pole through the hatch at a 10 degree angle, stepping the mast to the keelson in a similar fashion to the way it was done on Yeong with a molded GRP cup. I am still working on trying to determine the proper size mast I will need.

    Since my current pointy top rig has a sail area of 310 sqft I am looking to build a sail around 345 sqft. Does this sound right?

    I see there are a few methods to create camber, but a lot of people still choose to go with a flat sail. Why? I am currently leaning towards Arne Kverneland's method of adding camber, but I am still researching. What problems are encountered that would make a flat sail more desirable if any?

    Thanks for all the help, and I would greatly appreciate it if you guys can share some examples of using a hatch insert for mast partners, and mast stepping using a grp molded cup. 

    Happy holidays!

<< First  < Prev   1   2   3   4   Next >  Last >> 
       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
                                                               - the Chinese Water Rat

                                                              Site contents © the Junk Rig Association and/or individual authors

Powered by Wild Apricot Membership Software