S2 6.7 Junk Rig Conversion

  • 26 Mar 2019 22:35
    Reply # 7246665 on 6872873

    I have been following this thread with great interest, as it has drawn out a lot of very good information and much food for thought, from our experienced commentators.

    One rather crucial point seems to have been a little glossed over, and that is, choice of mast length. It seems that Scott has chosen Arne’s planform over other alternatives on offer, partly for the reason that it is important to him to keep mast length as low as possible. This is a question that I think would be of interest to anyone designing a new conversion and I would be grateful if it could be re-visited. So as not to distract from the current discussion which is ongoing in this thread, I have started a new one in the hopes of focusing on mast length.


  • 26 Mar 2019 21:37
    Reply # 7246545 on 7245846

    Anonymous wrote:

    For me figuring the yard was more of a challenge. I end up with 2” x.125 tubing, same grade. I screwed up my order for  2x.065. I’d planned to laminate a 1“ tube to the lighter 2 in. similar to what was done and shown elsewhere here. The single .125 tube is a bit heavier up high than I wanted but I was suprised to calculate that it was not by all that much. 

    https://www.onlinemetals.com/merchant.cfm?id=71&step=2&top_cat=60 

    This site lists tubing weights by size, inches and lbs., and should be helpful in making comparisons.

    I went back and looked at that. “Not all that much” ain’t very specific. The difference between the heavier single 2x.125 tube and the 2x.065 combined with 1x.065 is 26%  Which in Brenda B’s case was 2lbs not counting a few ounces of glue and fasteners. While that did not seem like much to me the reality is that at 9.57 lbs. the yard is heavier than it needs to be.  I could have cut that weight up high with better planning by going with a single tube 2 1/4x.065 in. at 5.83 lbs which I think would be stout enough.
  • 26 Mar 2019 14:56
    Reply # 7245846 on 6872873

    Scott, the battens on Brenda B are 11 ft.  The long one is probably about 12ft.. They all are 1 inch X .65in., 6061 T6. While the longer batten might have been one size up is has been fine over these past three sailing seasons.  While displacements are close, your boat is a a foot beamier, and at 22 ft is likely to carry more weight than my 19 footer. I think 1 1/4 inch  X .065 inch would give more stiffness and less weight than the 1 inch x .125.   I wouldn’t consider pipe. Strength to weight is most often much too low compared to tubing. I’d stick with 6061 T6 for it’s strength. It seems that 6061 T6 and 6063 are the most easily available grades of tubing in the US. 

    For me figuring the yard was more of a challenge. I end up with 2” x.125 tubing, same grade. I screwed up my order for  2x.065. I’d planned to laminate a 1“ tube to the lighter 2 in. similar to what was done and shown elsewhere here. The single .125 tube is a bit heavier up high than I wanted but I was suprised to calculate that it was not by all that much. 

    https://www.onlinemetals.com/merchant.cfm?id=71&step=2&top_cat=60 

    This site lists tubing weights by size, inches and lbs., and should be helpful in making comparisons.

  • 26 Mar 2019 04:33
    Reply # 7245275 on 7243174
    Scott wrote:

    Does anyone have reason to expect 6061-T6 with a 1" OD and a wall thickness of 0.065" is not strong enough for my rig?

    I would question the need to go to the expense of T6 aluminium. I had three aluminium battens on the sail we made for Footprints, (and 4 x carbon battens). The sail was 53 square metres, batten length of 6.5 meters  and a boat weight of just under 6 tonnes. The battens were T5, 65 mm in diameter and 1.5mm wall thickness. Despite numerous heavy gybes and thousands of miles of sailing, up until the time I sold Footprints just recently the battens never gave any trouble, and have performed equally as well as the carbon fiber battens. I think larger diameter with thinner wall thickness is the secret.
    Last modified: 26 Mar 2019 05:22 | Anonymous member
  • 25 Mar 2019 21:20
    Reply # 7244567 on 6872873

    Arne,

    At a 70% increase in cost and 82% increase in weight I can get 1" OD x .125" wall.

    I have been looking here and here. I hope to make a stock 12' length work for all battens except the top sheeted batten. For the 'long' batten I would buy a single 20' or 24' length and cut it down.

    Maybe the 6061-T6 0.840" OD x 0.109" ID (OD 21.336mm x wall 2.7686mm) T312 is a better option. Smaller OD but thicker wall?

    Last modified: 25 Mar 2019 21:31 | Anonymous member
  • 25 Mar 2019 19:47
    Reply # 7243911 on 6872873
    Anonymous member (Administrator)

    Scott,

    what other sizes are available near the one you mention?

    Arne

  • 25 Mar 2019 14:37
    Reply # 7243174 on 6872873

    To keep my project going I will need to make a decision on battens. I have come full circle and now I am thinking alloy battens again.

    Arne was kind enough to suggest that I look for 25mm OD and 21mm ID AL alloy (25x2mm).

    Considering the price and weight I would like to use 6061-T6 with a 1" OD and a wall thickness of 0.065". If I did the math right this works out to a 25.4mm OD and 22.1mm ID. This is a slightly larger OD but with thinner wall compared to what Arne suggested.

    I think this is the same size used on 'Brenda B'. The listed displacement I found for my S2 6.7 is 2200lbs and the Com-Pac 19 is 2000lbs. Pretty close. But on the other hand my battens will be longer than the ones that 'Brenda B' carries.

    Does anyone have reason to expect 6061-T6 with a 1" OD and a wall thickness of 0.065" is not strong enough for my rig?

    Last modified: 25 Mar 2019 21:33 | Anonymous member
  • 21 Mar 2019 16:54
    Reply # 7238244 on 6872873

    In a cambered panel sail, both the luff and the leech are concave with the sail on the floor, because of the extra cloth you've sewn in.  You won't really see what you've made until the battens are in place.

  • 21 Mar 2019 13:14
    Reply # 7237893 on 6872873

    Panels Seven, Six, Five and Four stitched together. Is the luff straight enough? I don't worry. I'm happy.

    More photos in my album here.

  • 12 Mar 2019 12:36
    Reply # 7214534 on 7214327
    Anonymous wrote:

    Whether it is good enough or not, depends on who is judging it. All I can say it that I could not make it better than that.

    So keep up the good work!

    Arne

    Thanks Arne,

    I really appreciate people like yourself who make me feel like a part of the JRA. Your encouragement from the other side of the Atlantic is helpful. And of course  drawing the sailplan and providing all the detailed instructions are a big help too!

    I now have panel 7 stitched. I find it amazing how just getting one hem folded and sewn already makes this feel more like a sail and less like just a piece of cloth. I am less sure about those wrinkles that have shown up. I hope this is an artifact of the 'barrel rounding' I want and not evidence of an error I made.

    Last modified: 12 Mar 2019 13:27 | Anonymous member
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