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Badger's trim tab

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  • 18 Aug 2014 03:17
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    Reply # 3076342 on 3063851
    Anonymous member
    A very kind offer, Patric.  I know one or two junkies in NZ who might well fancy the gear, but I suspect the cost of freight might make it too costly.  But do let me know when you're ready to sell, please :-)
  • 16 Aug 2014 20:10
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    Reply # 3075860 on 3073575
    Deleted user
    Annie Hill wrote:

    A shame about the Atoms: they are a very nice gear.

    It's surplus to requirements now or at least it will be ;-) 

    I'm planning to put it on ebay or ybw when I find the time but in case you're interested I'd be more than willing to let you have it for free. No parts missing, could do with a little TLC though.
  • 16 Aug 2014 20:02
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    Reply # 3075857 on 3063851
    Deleted user

    Many thanks for all the useful input, much appreciated! I don't quite share David Thatcher's overly pessimistic view though: a skeg or long keel mounted rudder works differently to a foil shape rudder. There's no leading edge as such on the rudder itself. I know there's nothing as dangerous as a little knowledge, in particular when quoting out of context but here's what Dave Gerr has to say regarding size:


    "Rule of thumb Rudder area- Sailboats with Moderate ( Modern, long) Keels= 0.058 x Waterline length x Draft (including keel)"

    "For sailboats rudder area should be between 8% and 10% of lateral plane. The higher the aspect ratio and the farther aft the rudder, the lower the required area." (down to 6 or 7% for high aspect right aft)

    "If the rudder is on a skeg, up to 12% of the rudder area can be assumed to be in the skeg. If the skeg is larger then fine. The skeg will improve directional ability and strengthen the rudder. But the additional area (over 12% of rudder area should not be counted towards the effective rudder area

    In my case that seems to come down to roughly 0.65 m²

    I'll go with Annie's idea btw, trying to add as little as neccessary at first. Of course there'll be little harm done by increasing the rudder area above the water line to give me a straighter line for my trim tab connection.

    Wasn't planning on a lift out this year, I'll fly back home in two months and the weather isn't too promising for this kind of work. Not exactly cheap either which is why I try limiting my time on the dry. Hope to renew antifouling and do something about the outboard well opening next year, guess I'll have a go at the rudder too then.
  • 14 Aug 2014 16:54
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    Reply # 3074047 on 3063851
    Anonymous member

    Patric,

    If you made your rudder as per Annie's sketch, you'd end up with something very similar to Tystie's rudder. Wide at the bottom, with straight TE, works quite well, IMHO.
  • 14 Aug 2014 04:10
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    Reply # 3073575 on 3063851
    Anonymous member
    Patric, I am no expert, but to me it looks like your rudder has already been quite seriously modified.  My feeling is that the builder put on a skeg and copied the rudder from the 30ft dory with the long keel.  He then found is was too big and cut quite a lot off it.  You now say that you seem to have very little control at low speeds so it appears he cut too much off!  My instinctive feeling is to go for Photo 3, but somewhat adapted.  I've done a rather crude 'drawing' of it which I've put in my 'useful pics' album.  You could, conceivably add to the top of the rudder to make a straight line, or you could build out a blocking to hang off the top pintle.  When you see the picture, you will know what I'm talking about.  However, as I said, I have hardly any technical expertise and I may be talking through my hat, here.  Anyway, I hope that if nothing else you're finding it useful to be able to bounce ideas around.  Good luck.

    A shame about the Atoms: they are a very nice gear.
  • 11 Aug 2014 20:34
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    Reply # 3071087 on 3070669
    Deleted user
    Patric A wrote:

    Ok, fixed the gallery (I hope) and spoke to boatbuilder about how to increase rudder area. He suggested laminating more ply on the trailing edge and fastening with bronze bands. I'll go with stainless though since all the other fittings are 316, as is the TT.

    Instead of adding a very large area I thought of either filling in the "bottom kink" (red triangle sketch) or maybe adding that plus the yellow triangle (second sketch). Too large a rudder might be just as undesirable performancewise as a small one.


    Wow, I just had a look at the photo of your rudder and no wonder you have been having steering issues. I am half way through building a new rudder for my own 10 metre boat and am enjoying the project although yes, you do need some space to do it. Rather than try and patch up the old rudder you should really build a complete new rudder. I found this web page to be very helpful in terms of design and a basic how to put the rudder together:  www.paceship.org/how_to/rudder/asp I don't think this will work as a link but you should be able to find the page easy enough.

    Good luck with it.

    Last modified: 11 Aug 2014 20:35 | Deleted user
  • 11 Aug 2014 19:41
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    Reply # 3071029 on 3063851
    Deleted user

    At least I'm not the only one having trouble ;-)

    "Thank you for all of the photos and drawings. I have just spent a while with our engineer discussing how the Trim Tab could be mounted to the stern of your boat. Firstly, he has pointed out that he never fitted the system to a boat of your type and it is not proving to be simple!"
  • 11 Aug 2014 15:03
    Quote
    Reply # 3070669 on 3063851
    Deleted user

    Ok, fixed the gallery (I hope) and spoke to boatbuilder about how to increase rudder area. He suggested laminating more ply on the trailing edge and fastening with bronze bands. I'll go with stainless though since all the other fittings are 316, as is the TT.

    Instead of adding a very large area I thought of either filling in the "bottom kink" (red triangle sketch) or maybe adding that plus the yellow triangle (second sketch). Too large a rudder might be just as undesirable performancewise as a small one.
  • 11 Aug 2014 12:50
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    Reply # 3070412 on 3070227
    Deleted user
    Annie Hill wrote:
    Patric A wrote:

    No love? Seems my questions go down like lead balloons.

    Sorry, Patrick, my computer has been away for an upgrade, so I have been offline. (But how about posting an 'avatar' so we know who we're talking to :-D)

    There used to be an avatar but seems to have fallen by the wayside somehow ;-)
    The fora can be a bit of a challenge when you don't own a Mac/Win/Linux PC, still no joy with the "link button". New avatar uploaded though!

    Pete could answer this more fully, but doesn't seem to want to contribute to these fora.  We had problems with the servo-pendulum in the Falklands, because just about every time we went sailing, we got kelp caught around the paddle and the break-away did just that.  So we decided to fit a trim tab so that it wouldn't catch.  If my memory serves, we used the same paddle (maybe scarfed on an extra piece) and the reason that we placed it as we did was to have it vertical.  We used information from Bill Belcher's book to make the decisions.  The trim tab worked better than well - it was the best self-steering gear that we had on Badger, with the added advantage that it was easy to override in moments of stress and controllable with a 'Brown Stick' which meant that one effectively had down-below steering: great for dodging lumps of  ice, fishing boats and steamers!

    Yeah that's one of the reasons why I decided against pouring money in an overhaul of my s/h Atoms gear. Not to speak of the plumber's shop that would have been neccessary.

    Thanks a lot for the shot of Elise N's rudder, that looks much nicer than mine. More powerful too and fitting a trim tab would be straightforward.

    I'll try fixing the issue with my gallery from the public library computer.

    Google shows "autosteer" "hydra" right on top, that's the one I'll be fitting. For several reasons I decided against DIY, mainly because living aboard means you'd be building this thing in your tiny bedroom.


    Again thanks for the replies and sorry if I sounded a bit frustrated, blame it on the monsoon like weather!

    Decided not to ask Hydra to modify the trim tab and rather do something about the rudder when I take the boat ashore next year.


    Patric
  • 11 Aug 2014 09:22
    Quote
    Reply # 3070371 on 3063851
    Deleted user

    Hi Patric, we've been out cruising in remote areas so didn't see your post earlier. I detached Ashiki's trim tab and threw it in a dumpster, it was really hard to get it to work properly (prefer to make a new one, simple one from steel if we pursued that path again). I suspect the problem was it wasn't offset back from the rudder as Graham has his, and I think Annie's Badger was that way too. Without that extra leverage the trim tab would drive the vane not the other way around.

    Belcher's book hasn't been that successful for us - maybe ours is one of the "difficult" boats. 

    We'll need to have Ashiki on the hard to do the job properly, but we may just opt for a tiller pilot instead, better in light winds..  and use the space left by the wind vane for another solar panel.  Presently trying to get direct vane to tiller to work, not promising, need to move the attachment points again.

    I agree with your decision on the rudder, that one doesn't look so good.
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