Sadler 25 conversion..

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  • 28 May 2020 10:15
    Reply # 8997323 on 8800878
    Anonymous member (Administrator)

    I too think that for ultimate strength of the yard, it would be wiser to have the thin tube on the top. However, we should be working far, far from breakdown loads here, so I don’t worry about that.

    As for aerodynamic benefits, my guess is that Slieve is right, but it will be fun to try, anyway. I plan to renew the lashings at the sling-point this summer (Dyneema, this time), so may just as well turn the yard upside down while I am on it.

    Arne


    Last modified: 28 May 2020 10:15 | Anonymous member (Administrator)
  • 28 May 2020 08:58
    Reply # 8997225 on 8800878

    ...smaller one on top it is then, thanks guys

  • 28 May 2020 05:35
    Reply # 8996984 on 8800878

    Structurally the larger section will be better in compression so the smaller tube should be on the tension side of the yard, the top.

  • 27 May 2020 23:09
    Reply # 8996445 on 8800878

    "Do you have any thoughts Slieve?"

    Silly question Paul, I stopped thinking years ago!

    Actually it is not a silly question Paul. It is an extremely important one and one to which I wish I had the answer. This afternoon I tried to define the type and direction of flow over a yard angled at 30° and many words later have come to the conclusion that with the wide range of wind speeds and angles of attack we can really only guess what the flow is at the head of the sail at any one time.

    I am convinced that the tip vortex is being pushed up along the yard at about 30° and exiting the sail right at the tip which is what is wanted and helps explain the rigs performance, and that would suggest Arne's latest double tube yards should be better than the earlier girder one I copied from him for Poppy, but as to which tube should be on top, my guess is the smaller one, but note the word 'guess'. Which ever, I suspect the difference will be minimum and not worth worrying about.

    Cheers, Slieve.


  • 27 May 2020 14:04
    Reply # 8995283 on 8800878

    Great

    thanks David


  • 27 May 2020 13:03
    Reply # 8995179 on 8800878

    6mm eyeplates, and M6 screws, I think. I don't suppose the shackles in your blocks will be any larger than that. If you have a 3:1 halyard and put two single blocks on two separate plates for it, it's a very reliable setup.

    Yes, I'm happy going up the mast. 25mm screws with all their length fully threaded into nylon have immense holding power. Put them in with thread locking compound for extra peace of mind.

  • 27 May 2020 12:41
    Reply # 8995143 on 8800878

    Thanks Arne, I was just curious as to whether the smaller tube was better for resisting compression, or elongation, hence the question. Actually I think I’ll go and sit on it to find out. 

    As to whether the orientation gives any aerodynamic advantage, my yard is only at a 30deg angle unlike your 70deg so maybe not eh. Do you have any thoughts Slieve?

    David, for the masthead fitting I have ordered the Nylon 6.6 as you suggested. 
    Should I use 6 or 8mm Eyeplates for my 30m2 Sail, and what size bolts? You used 8mm set bolts on yours, but partly as you said you had difficulty with crumbling when you tried to cut a 6mm thread in your PVC version. Also would you be happy going up the mast with set bolts holding you, if not would you recommend through bolting the eye bolts  ( that would of course entail having two of the eyeplates a little higher/lower, and having a larger bore hole down the centre so the cables could bypass the bolts..)?

  • 25 May 2020 23:07
    Reply # 8992074 on 8800878
    Anonymous member (Administrator)

    Paul
    First of all, that new sort of yard ‘just happened’, back in 2012, on Edmond Dantes, since the aluminium supplier/welding shop, was about to go on holidays. I then just received the yard tube and a batten tube, and decided to try if it worked this new way. I reckoned that the main tube was almost strong enough, and the batten tube would only add some stiffness in the vertical plane. This is needed on cambered panel sails, since all the vertical loads move out to luff and leech.
    This worked perfectly well, and since then I have rigged two more boats with that sort of yard (Frøken Sørensen and Ingeborg)

    Actually, recently I have been pondering if I should turn the yard upside down, as you suggest. Before re-installing it, I would like to bandage it along its full length (I would probably just stitch on more of that PVC canvas I use at the mast. The foggy idea around this is that the 70° yard, which actually is a big part of the luff, would form a round wing-like leading edge, which would do some good to the sail.

    I would encourage you to try it, yourself. I can see no structural problems with it, at least.

    Cheers and good luck!
    Arne


    Last modified: 26 May 2020 13:38 | Anonymous member (Administrator)
  • 25 May 2020 17:42
    Reply # 8991602 on 8800878

    Hi,

    Here’s my double tube Yard a la Arne that I glued and bolted yesterday.

    I really like the idea, another elegant and simple solution- beats having to learn to weld.

    I’d like to say it went really smoothly, however..

    After applying the bead of glue (Sabatack 750) I didn’t realise that I’d smoothed it down over the edge of the masking tape. When I removed the tape the glue had already started to go off, so it lifted all oalong the edge. No problem I thought I’ll apply more tape and smooth it all down, only to find I’d run out of tape. With the glue rapidly hardening I smoothed it down best I could, and in the process of trying to clean it up left smudges and lumps everywhere.
    I tried wiping with acetone which helped, but realised I’d have to use so much to clear it all up that there was a danger of it dripping on the glue line which may threaten it’s integrity, so I just left it all to harden. 
    I’m now an expert at getting hardened sealant off aluminium- scrape the worst with a credit card, then rub with fine wire wool and water.

    With the double tube yard I see that Arne has rigged his on Ingeborg with the smaller diameter tube uppermost, is this critical Arne, or could I rig mine with the larger tube on top?

  • 24 May 2020 11:49
    Reply # 8989593 on 8800878

    "Maybe my imagination, but it also seemed to heel less for similar speed when beating and was definitely less roll-ey in gusts on the downwind legs."

    That was also my impression. I found that I was frequently over-canvased being still totally under control I just enjoyed going faster. Over-canvased didn't have the same meaning as control was maintained, but the speed was up against or above the displacement speed in a heavy non planing hull. I found it so easy to sail that I became a bit of a hooligan overtaking faster designs.

    Great fun.


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