Junk rigged Wayfarer dinghy

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  • 10 Jul 2019 11:14
    Reply # 7773141 on 7773052

    Hi Slieve,

    Thanks for your comments. I chose the Wanderer as something stable to take the kids out in that I could still move on the shore. So far I like it a lot.

    Looking at the photos there are two thoughts which come to me. In an ideal world, with and infinity thin mast I would make the slot width zero. As the real mast gets thicker I feel the slot should get wider, to let the air flow past the mast, so I suppose I think of the slot width to be proportional to the mast diameter. Thin mast narrow slot, fat mast and wide slot. You have a fairly thin mast but to my eyes the slot looks very wide, which may (or may not) lose some of the benefit of accelerated air flow. (If I sound rather vague here it's because I'm not sure but it is a thought).

    Yes - the wide gap is an accident :-) I made the jiblets from the wrong layer in QCAD, then had to figure out how to make a sail that would work without changing much.

    I'm not sure of the effect, but something in me says that a wide exit from the jiblets might help a bit. However it wasn't intentional!

    The other thought is that as you get the rig settled down it is more important to remove all diagonal creases from the jib panels than from the mains, as it is the airflow over the cambered jibs that does the majority of the useful work. Creases in the jibs distort the camber badly.

    The yard angle for no creases in jiblets and mainlets is (unfortunately) slightly different, but I will play and see what happens.

    I don't see telltales on your jibs, but they are a great help, and you'll probably find that with them streaming you'll get your 'best to windward' performance. Keeping the jibs pulling should be the key to best performance.

    Yes - these are on the todo list but I haven't had time to fit them (and probably won't this year). It has all been a bit more rushed that I would have liked.

    Cheers

    Martin

  • 10 Jul 2019 09:12
    Reply # 7773052 on 6394430

    Thanks for the pictures of your Wanderer dinghy Martin.

    Mid way between the Enterprise and Wayfarer, I've always felt that the Wanderer is an under-rated design, and it's nice to see that you're getting fun out of it.

    A stretchy nylon material should work well with the barrel cut and you seem to have the main panels well organised.

    Looking at the photos there are two thoughts which come to me. In an ideal world, with and infinity thin mast I would make the slot width zero. As the real mast gets thicker I feel the slot should get wider, to let the air flow past the mast, so I suppose I think of the slot width to be proportional to the mast diameter. Thin mast narrow slot, fat mast and wide slot. You have a fairly thin mast but to my eyes the slot looks very wide, which may (or may not) lose some of the benefit of accelerated air flow. (If I sound rather vague here it's because I'm not sure but it is a thought).

    The other thought is that as you get the rig settled down it is more important to remove all diagonal creases from the jib panels than from the mains, as it is the airflow over the cambered jibs that does the majority of the useful work. Creases in the jibs distort the camber badly.

    I don't see telltales on your jibs, but they are a great help, and you'll probably find that with them streaming you'll get your 'best to windward' performance. Keeping the jibs pulling should be the key to best performance.

    Congratulations on your good work. Keep it up. Please don't take my comments as a criticism, as I only want to say what I have found out in the past.

    Cheers, Slieve.


  • 10 Jul 2019 06:24
    Reply # 7772947 on 6394430

    Hi Scott,

    Yes - I'm happy with the sail based on my limited (light wind) experience. I did spend some time playing with various ways to cut the panels and concluded that barrel cut using my spreadsheet and a few tweaks would work as well as anything else.

    I'm not sure barrel cut would work well with a fabric that wasn't stretchy on the diagonal.

    Last modified: 10 Jul 2019 06:26 | Anonymous member
  • 10 Jul 2019 01:13
    Reply # 7771445 on 6394430

    Hi Martin,

    The sail and rig looks really sharp. Thank you for sharing the photos. If I ever get a junk rig put together and it looks half as good as yours does then I will be happy.

    I would like to know if you are satisfied with the barrel cut panels and SJR together. That method of construction looks much less intimidating to me, personally, than others.

    Your post made we wish that I had considered the SJR!

    Scott

  • 09 Jul 2019 09:39
    Reply # 7770069 on 6394430

    The panels are barrel cut. The fabric is stretchy on the diagonal so creases tend to disappear. I spent some time experimenting with fabric, sticks and sticky tape. There is a bit of extra fabric (1% of panel width) on the sides in front of the point of maximum camber plus an extra 5mm in the centre of each jiblet luff and this appears to do the trick.

    The jiblets collapse when too close to the wind, although it is possible to pinch using the mainlets alone.

    The colour scheme is (of course!) based on the JRA logo :-)

    The design is actually a merger of the Johanna and Poppy sail plans. I was actually trying to build something more Johanna-like but started cutting out jiblet panels based on the wrong layer in QCAD. Oops. A hasty redesign followed to figure out a way to use the panels I had already made and this sail is the result.

  • 09 Jul 2019 00:26
    Reply # 7769655 on 6394430

    Looks good Martin. I have just done a "first splash" with a home made SJR sail too, and I am admiring your sail. Mine was simpler to make, but I must say the Poppy profile is more aesthetically pleasing and I love that dash of yellow (custard?).

    I can't see any seams, and am curious to know how you built the camber into your sail.

  • 07 Jul 2019 18:29
    Reply # 7767423 on 6394430

    First sail today in my converted Wanderer dinghy :-)

    For those who don't know the Wanderer is a smaller Wayfarer - 14' instead of 16' - which makes it much lighter and easier to move around on land.

    Pictures here: https://junkrigassociation.org/Sys/PublicProfile/29417059/PhotoAlbums/103651223

    Very light winds today, but enough to fill the sail and get her moving nicely. Seems well-balanced and delightful to sail. A big relief - this sail has been put together against a deadline which means lots of corners were cut - so I wasn't certain everything was actually going to work.

    Last modified: 07 Jul 2019 18:30 | Anonymous member
  • 29 Aug 2018 10:19
    Reply # 6644049 on 6394430

    Here's an alternative approach to finding the righting moment - look at the breaking load on the existing rigging. The windward shrouds pull the side of the boat up, while the mast pushes the centre of the boat down.

    With the Wanderer we've got 3mm wires. These have a published breaking load of 757kg. The Talurit fittings reduce this by 3:1 (most optimistic)  to 252kg (2475N). With a distance of 0.9m from boat CL to chainplate we get a righting moment of 2200Nm. This feels about right.

    This is the breaking load, thus catastrophic failure follows overloading. With an unstayed mast we normally get some warning that the mast is overloaded so I would be comfortable reducing this figure for a junk rig.

    Does this make sense?

  • 27 Aug 2018 20:43
    Reply # 6641420 on 6394430

    I've now got a boat - a Wanderer. This is a smaller version of a Wayfarer - 14' instead of 16', much lighter and thus easier to handle onshore. Back to the calculations!

    Currently a wooden mast looks optimal. I'd be making a wooden topmast anyway so I'll see what timber is available locally.

  • 31 Jul 2018 19:30
    Reply # 6407115 on 6394430

    Thanks David - very useful information. I was wondering if the feathering issue was because the 'lift' of the jiblets is right at the luff of the SJR, thus the lower the aspect ratio the less area can be tolerated in front of the mast?

    I've uploaded the DXF (QCad) here if anyone wants to take a look. There are two SJR layers - both based on the Poppy sail. One is 'main plus jib' area of 11.4m2, the other is 10% bigger. Still early days with the design - it probably needs the boom higher.

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