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Thread: Gaff Jaws - New Tumbler

  1. #1
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    Default Gaff Jaws - New Tumbler

    A recently acquired boat (5.1m lapstrake, open sail/row, 10sqm gaff sloop) is undergoing a bit of R&M (repair and maintenance ). After doing a bit of internet and forum search, I realised that the 'gap' in the gaff's jaws should actually be filled by a tumbler.





    Unfortunately many of the previous good posts no longer have their photos...

    The Gaff Rig Handbook has a few small diagrams showing the general looks of a tumbler. So far from forum posts, I have determined the following:

    • tumbler height is 3x gaff jaw width
    • pivot point is just (10%) above centre of tumbler so that is stays vertical
    • edges should be rounded/radiused
    • leathering and greasing recommended

    Anything else?

    I am considering using white oak offcuts that are available.

    Does anyone (e.g. Chris Gerkin, Mike Hanyi, T.Kamila) have any detailed pics/drawings of what one should look like?

    The unanswered question of course is why - if there was originally one - did the tumbler break...
    Last edited by Songololo; 03-07-2013 at 09:50 AM.

  2. #2
    Join Date
    Aug 2005
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    central wisconsin
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    Default Re: Gaff Jaws - New Tumbler

    although it would be nice to know why it broke, it's pretty impossible to say......
    it is a small piece. my guess would be from wrong grain orientation and drying out. possibly improper wood for the task.
    the important feature is that you know it should be there.
    grain orientation would be my best bet. when it broke, the growth rings were likey parallel to the pin and it sort of split in half at the hole, off the pin.
    white oak is a good choice, i would think ... keep the growth-rings at right angles to the pin it pivots on( in other words, the growthrings should run fore and aft through the piece) and parallel to the mast up and down. try to find a piece from a large tree so that the growth rings are as straight as possible through the piece.
    it should look just the the bigger boys, just smaller in overal size. extend the full fore and aft dimension of the tumbler above and below the pin a little further up and down, so it tapers a bit quicker to the ends to keep as much material around the pin hole as possible. but be sure to remove enough material above the pin to allow it to pivot enough without binding when the gaff is peaked up hard. along with the reasons above, that could be why the original broke.
    Last edited by merlinron; 06-07-2008 at 08:22 AM. Reason: typos

  3. #3
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    Default Re: Gaff Jaws - New Tumbler

    A correctly proportioned sketch of the gaff jaw and a first pass at a tumbler is shown below:



    How far into the jaw area should the tumbler protrude? In the above sketch I have it flush with the inside (i.e. boom) faces of the jaws (see first post for a clearer view of the recess for the tumbler).

    Here are some gaff and jaw diagrams:







    More gaff info on the Gaff Rig Page:
    Last edited by Songololo; 03-07-2013 at 09:53 AM.

  4. #4
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    Default Re: Gaff Jaws - New Tumbler

    deep enough into the jaws so that the upper corners of the jaws don't contact the mast when peaked up as much as possible. it's hard to say exactly, it depends on your sail. either too deep into the jaws or not deep enough will give wrinkles to the throat area of the sail. it's an area where there will always be some wrinkling, the idea is to have as little as possible.... a compromise between peaked hard and loose. you can get an idea by laying out your sail and measuring the distances and arrangement of luff and gaff atatchment. the tumbler should take up any space left with the sail layed out flat on the ground with boom and gaff in place. it's almost trial and error. don't be afraid to add or subtract a little material from the tumbler after it has been installed to get that area as smooth as possible.

  5. #5
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    Default Re: Gaff Jaws - New Tumbler

    Here is what the new tumbler looks like, leathered, oiled and waxed!





    This was the first piece of leathering that I have done - definitely room for improvement.

    Changes made from original tumbler slot and attachment:
    • replaced 3mm riveted rod with 4mm rod having threaded ends and cap nuts (easier to make repairs)
    • increased the tumbler travel angle to correctly reflect the 40 gaff peak angle

    Having had a look at the direction of bend of the previous tumbler pin and noticed what looks like a small tumbler travel angle, I can imagine that the previous tumbler probably broke as a result of the tumbler travel angle being too small and thus not being able to accommodate the 40 degrees when the gaff peak was fully raised...
    Last edited by Songololo; 03-07-2013 at 09:53 AM. Reason: Typos

  6. #6
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    Default Re: Gaff Jaws - New Tumbler

    you are ready to go!

  7. #7
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    Default Re: Gaff Jaws - New Tumbler

    George, interesting schooner you have there! These gaff jaws seem to have been modified? How was the tumbler travel angle determined?

    http://lh4.ggpht.com/georgelewisray/...jpg?imgmax=912


    http://lh4.ggpht.com/georgelewisray/...jpg?imgmax=912
    Last edited by Songololo; 06-20-2008 at 03:02 AM.

  8. #8
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    Default Re: Gaff Jaws - New Tumbler

    I inherited the gaff jaffs and have fabricated a replacement saddle for the foregaff because it was binding on the shrouds. Tom Colvin, saw pictures of the jaws and emailed that he "almost lost his lunch" they were so ugly. They are at least stout and so far mostly trouble free. It will be later this year before I get a chance to update the project photos and get back to seriously thinking about such things again.

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