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Advice sought on rudder lashings

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Anonymous (not verified)
Advice sought on rudder lashings
Hi, First of all I must apologize for not actually being a Tiki builder; I'm currently building a wooden 18ft mini ocean cruiser loosely based on a double ended, long keeled George Buehler design. A friend of mine who owned a Tiki 21 many years ago suggested I use the same rudder lashing system as his Tiki instead of traditional metal gudgeons and pintles. I've researched on the web and have found several Tiki photos clearly showing the layout of rudder/sternpost lashing holes and the general rudder arrangement but I'm in need of help on how I should shape the short portions of the rudder leading edge and sternpost trailing edge where the lashings actually form the hinge. Some seem to show a fairly flat surface with radiused edges. Is this OK or should I make the bearing surfaces of the rudder and sternpost truly semi-circular? My friend cannot remember the exact construction details as he purchased his boat second hand rather than having built it, so I thought I should seek advice from those who have direct experience. Any hints would be much appreciated. Cheers, Jerry.
Anonymous (not verified)
Re: Advice sought on rudder lashings
Jerry, it doesn't take much of a radius; if I recall correctly, I used a 1/4" radius on the new rudders I built recently. What is important is the figure 8 lashing: this insures that the pivot point of the hinge is centered at the crossover point of the lashing. Thus the lashing does not rub against either the rudder or stern.
Anonymous (not verified)
Re: Advice sought on rudder lashings
Thanks Kim, I suspected that the figure of 8 arrangement would give a self aligning connection whatever the radius of the bearing surfaces but, without having a working example to study, it was a bit hard trying to visualize how it all should function. I've just glued up my rudder from 7 layers of 6mm ply to give a finished thickness of 42mm. I'll be glassing it with one layer of 400g biaxial and West epoxy plus an extra layer or two in way of the lashings. My boat is a rather chunky little affair with a full length keel/stem/sternpost measuring 5 inches wide so I need to make a separate 42mm wide mini-sternpost to take the lashing holes, which I'll through bolt to the boat's main sternpost. I've yet to decide whether to make this in one continuous length or to make 4 smaller, individual pieces, say 8 inches long. As I don't expect to exceed 4 knots most of the time I guess the low drag benefit of a close clearance between rudder and stern is something of a moot point! Do the polyester rope lashings need very frequent replacement? To someone used to metal gudgeons and pintles I must admit that using rope feels instinctively wrong, however all the evidence seems to suggest that the rope lashing system is very durable. Back in the 90s I built a Jim Brown Searunner 31 tri which I sailed to the Caribbean. I used custom made 316 grade stainless fittings for the skeg hung rudder but within 2 years of launching, and a year in tropical waters I discovered that the lower (underwater) fittings had crumbled away to almost nothing. I'd stupidly allowed a small buildup of barnacles to form on the fittings (due mostly to the sky-high cost of Caribbean haulouts!), resulting in oxygen starvation, and subsequent rapid, unseen corrosion. Hence I no longer have any faith in stainless for underwater use, and bronze castings are way beyond my budget. Using rope lashings certainly offers a simple and viable alternative. Cheers, Jerry.
Anonymous (not verified)
Re: Advice sought on rudder lashings
The lashings have a long service life, lasting up to 10 years reportedly. My boat had been switched to gudgeons/pintles [img]http://farm2.static.flickr.com/1134/1043319086_bd835a5239_o.jpg[/img] thus opening up a large gap between the sterns and rudders. So I built new rudders and went back to lashings. [img]http://farm4.static.flickr.com/3644/3557395399_1027364d7e_b.jpg[/img] Yes, stainless steel really needs air to maintain any semblance of corrosion resistance.
Anonymous (not verified)
Re: Advice sought on rudder lashings
Many thanks for the info and the photos. Your rudders are pretty much identical in shape to the one I've just made, and the lashing spacing is similar, so I reckon I should be OK. After glassing my hull prior to turning it upright I applied several coats of West epoxy mixed with a total of 4kg pure copper powder hopefully so that I can avoid the need for regular haulouts in expensive places where tides are too small for drying out. I'll do the same for my rudder but what about the rope lashings? Do you paint them with antifoul or just keep them scrubbed as best you can? Cheers, Jerry.
Anonymous (not verified)
Re: Advice sought on rudder lashings
I painted the 2 lower lashings on each rudder with the bottom paint: [img]http://farm4.static.flickr.com/3341/3648912507_eeace8ef0d_b.jpg[/img] I used West System syringes to fill the stern holes with epoxy after lashing; the rudder lashing actually runs through epoxy inlays: [img]http://farm4.static.flickr.com/3601/3494604793_c2ef014cff_b.jpg[/img] ^^Best way. . .I was in a hurry to get out of the boatyard, so I didn't inlay the sterns.
Anonymous (not verified)
Re: Advice sought on rudder lashings
The best step by step description of a very good lashing preparation is on Scott Williams site. http://tiki26element2.blogspot.com/search/label/rudders David http://www.boatsmithfl.com
Anonymous (not verified)
Re: Advice sought on rudder lashings
Hi David, Many thanks for the link to the Scott Williams website. Plenty of info and nice big, clear photos. I'd also emailed the Wharram design office with a request for help without really expecting a response, however I've just received an email from Liz at wharram.com with a scanned copy of the actual Tiki 21 rudder 'hinges' detail sheet attached! Now that's what I call excellent service. Cheers, Jerry.
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