Tuesday, February 9, 2016

Keeping My Mind Open

When I first started this project I felt quite committed to a junk rig for all of its advantages.  I even went so far as to commit to it with the URL of the blog.

Now, I'm not so sure given everything I have been reading about other rigs and especially with regard to the functionality I want with being able to lower the rig and get under bridges.

I find myself quite intrigued with the sprit sail.  In this comparative test the sprit sail proved to be superior to other rigs when tested on the same boat under conditions deemed fair.  One of the things discovered in the test was how much improvement was gained by the use of a small, non-overlapping jib.

That got me to thinking.  A jib, for all intents and purposes acts similarly to a leading edge slat on an aircraft wing.


I participated in the building of a homebuilt aircraft called a Zenith CH801. The fixed leading edge slats on this airplane vastly improved the efficiency of the wing.  We were up in the plane one day and with power on were able to slow the aircraft to less than 30mph indicated prior to a very gentle stall.  First used on the famous WWII Storch the slats made for an aircraft that could get in and out of places that would be unthinkable without a helicopter today.

But if a jib makes the airflow around a mainsail so much better, then its triangular shape must certainly be a detriment the further up the sail you go.

And a big square sprit sail would not benefit much up high, where the wind is, with the tiniest bit of triangle that such a jib would provide.

So why not a square jib, for a square sprit sail, on a square boat?


In this latest fantasy (which I intend to test with little Autarkia) the boat has a square jib.  There is a boom fixed to the top of the mast extending forward, with a fore stay running straight down to the bow. The jib has a 'yard' on top and a 'boom' at the bottom.  It also has a controllable sheet at the top as well as the bottom.  It in effect, becomes a fully adjustable leading edge slat for the main sail.

The main sail, is a pretty standard loose footed sprit sail.  The nice thing about the whole rig is it would come down easily.  Since the mast would be stayed (fore stay, either side and running back-stays) I could use a lighter mast, and in a tabernacle could be lowered with simple and light rigging.  The sprit itself, while quite long could be made in two sections, allowing the whole rig to be stowed horizontally without extending past the stern.

Reefing would be accomplished in the typical sprit sail fashion of 'brailling up'.


I could have well over 500 s.f. of sail area in a compact, low aspect and possibly quite efficient rig.  I'll be playing with this idea with the model.  But for today, it's back to work on full size Autarkia!

15 comments:

  1. I'm sorry.
    I can't resist.
    Forgive me..
    https://www.youtube.com/watch?v=50ARfQR8J6g

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  2. here's more on what I'm considering building.
    Ev.http://www.pdracer.com/sail/unusual/

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  3. lower the main mast (s) with a gunter.http://www.duckworksmagazine.com/04/s/articles/gunter/

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  4. This will truly be interesting to test out. If you're correct than still room for even a pretty good sized mizzen on the rear. Excellent gallows on the front for hanging foul politicians or bankers when in port or at anchor.

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  5. I'm afraid that it may work so well with the model I will be compelled to build it full size. My wife doesn't think it looks very attractive...

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  6. Are you considering the split junk rig at all?
    http://www.junkrigassociation.org/Resources/Documents/Slieve's%20Files/AYRS%20Catalyst%2037.pdf

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  7. I've looked at the split junk rig. I think that it is a great idea. I haven't completely ruled it out...

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  8. This comment has been removed by a blog administrator.

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  9. Think about the force of the jib's "yard" at the top of the mast, it's going to exert quite a bit way up there. might be easier to run a second mast up in the bow to fly the jib off of (Uffa Fox did this {but more of a way to get around some racing rules} ) Otherwise I think you may be looking at a really stiff/heavy mast or some wicked engineered staying to deal with the forces between the down force of the stay and the twisting force of the sail/wind.

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  10. Sometimes comments get doubled up...don't know why. That's why you see one deleted. Yup, I've been thinking about those forces. No doubt there'll be some playing around to do. I'm going to start with the model soon though. It should give me some kind of feel for it. I'll go flimsy on the scantlings and materials too, just to see what wants to twist or bend. Should be fun.

    Also, I've been redrawing the main - taking some of the squareness out of it and reducing the size. Can't have it as ugly as it is right now :-) As Robert Goad suggested there may be a mizzen in the works too. I'll post as it develops.

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  11. So much utility in a good sized mizzen.

    Who knows? You might be onto a radically innovative sail design here. Perhaps good to keep in mind the really nice benefits of junk rig for older people and junk rigs on the modest side at that. Once again that youtube vid of Alan Farrell hoisting his junk sail on China Cloud is instructive of how a older guy handles a junk sail. Certainly worked for him into old age. And, if we do suffer a distribution seize-up for awhile due to a banking collapse nice to know you can swap out parts with polytarps, old rope, battens out of driftwood, etc.. In the end boats can be so incredibly romantic that if a ketch rig with crabclaw main and junk lugged foresail and sprit sail mizzen does it for you then who could dispute that? IMHO though... really like your junk lug main and two sprits on each end.

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  12. Yeah I do too. Still, flights of fantasy are fun.

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  13. https://www.youtube.com/watch?v=XIBDOUSd-Ag

    Allan Farrell raising his junk rig in this vid from 1:35 to 2:10 mark.

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  14. My taste runs to this kind of innovative thinking/rig. Either way, as a voluptuous friend put it, "if ya can't hide it, decorate it!"

    I mean, they don't call it 'canvas' for nothing. 8)

    Dave Z

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