{"id":983,"date":"2011-11-07T16:13:05","date_gmt":"2011-11-08T00:13:05","guid":{"rendered":"http:\/\/svrainshadow.com\/?p=983"},"modified":"2024-06-14T09:21:09","modified_gmt":"2024-06-14T17:21:09","slug":"boom-teardownouthaul-revealed","status":"publish","type":"post","link":"https:\/\/svrainshadow.com\/?p=983","title":{"rendered":"Boom teardown–outhaul revealed"},"content":{"rendered":"

OK, so the sailing season is over for us, and I have started several projects, including tearing down the boom.<\/p>\n

Trevor (Ronar M) on the Nic 38 forum<\/a> described the outhaul system as \u201cpoxy\u201d which exactly describes how it is.\u00a0 You have to pull very hard on a little \u201cstring\u201d that comes out of the boom \u2013 and at the front of your mind as you are doing this, is that if it snaps \u2013 ping, overboard you go.\u00a0 I\u2019d measured it as only having a 3:1 purchase.\u00a0 Not much.<\/p>\n

Yesterday I took the main boom off Rainshadow, and today I tore the boom apart to get into the innards where the outhaul mechanism is.\u00a0 That was the first challenge \u2013 undoing all the fasteners that hold the boom ends onto the main tube.\u00a0 There were mostly all seriously stuck because of the corrosion between stainless and Aluminum.\u00a0 I used impact drivers, a torch, acids, lubricants, etc.\u00a0 In the end I had to grind off some and drill out the screw.\u00a0 Now I will have to tap some of these holes a size larger later.<\/p>\n

Once the fasteners were out, the boom ends came out easily \u2013 the anodization was still good on the inside.<\/p>\n

At the forward (mast) end, there is a double block held in place by an aluminum rod that passes through the boom.\u00a0 The ends of the rod had been hammered down so that it would not come out, sort of like a giant rivet.\u00a0 I had to grind off one end slightly and then bang it out. I\u2019ll have to replace it now, perhaps with a stainless bolt.<\/p>\n

\"IMG_2964\"<\/a><\/p>\n

You can see it here before I took it apart. The giant rivet runs left to right at the back behind the block.\u00a0 The line exits the boom at the right.\u00a0 The hole at the left is for access for\u00a0 lubricating the sheaves (that\u2019s what I do).<\/p>\n

\"IMG_2970\"<\/a><\/p>\n

At the left, shown taken apart,\u00a0 is the rod that holds the block in place.\u00a0 In the picture, the block is rotated 90 degrees relative to the rod so you can see the sleeve that fits over the rod.<\/p>\n

Next, as you move aft, you get to another block that is connected to the end of the stainless steel cable that is connected to the slider where the clew is fixed.\u00a0 This block has the end of the \u201cstring\u201d tied to its becket.<\/p>\n

\"IMG_2968\"<\/a><\/p>\n

That line travels back to the double block, around the first sheave, then back to the aft block through the sheave and back to the last sheave on the double block and then out the side of the boom where its cleated off.\u00a0 If that\u2019s not confusing enough, suffice to say it\u2019s a three to one purchase.<\/p>\n

The cable attached to the block above leads aft and around a sheave in the end piece of the boom, and then exits on top where it is attached to the slider in the groove on the top of the boom.\u00a0 \"IMG_2963\"<\/a><\/p>\n

This is the slider (upside down).\u00a0 The top part slides in the track on the top of the boom.\u00a0 Note the missing black plastic spacer at left.\u00a0 The cable is swaged to a threaded rod, which has a nut with a split pin to stop it coming off.<\/p>\n

Other notes, the cable is about 9 feet, and the line is about 21 feet.\u00a0 I\u2019m quite sure the line is not the original.\u00a0 The boom had obviously been disassembled before (and equally obviously was they also had trouble getting fasteners apart).\u00a0 About half of the original screws had been replaced with hex heads.\u00a0 Next time use Tef-Gel<\/a>\"\" ! (See the update for August 2016, describing how some screws backed out, possibly because the Tef-Gel was too slippery. Next time I am using Loctite in situations like this where the fasteners are subjected to vibration and variable loads).<\/p>\n

I am considering how to modify this.\u00a0 I think I\u2019m going to add a second block and line at the end of the cable that would double the purchase.\u00a0 However, that would reduce the range of motion of the slider and mean it needs more line.<\/p>\n

Update: December 18th, 2011.<\/strong><\/p>\n

Finally decided to implement the idea above.\u00a0 I decided I didn\u2019t want to detach the stainless cable from the block used in the 3:1 purchase, so I simply added a new block in the 3:1 section to replace it, and used it for the 2:1 purchase part.\u00a0 So now, starting from the aft end of the boom, the outhaul cable runs around the sheave at the end of the boom, and forward until it reaches the first block.\u00a0 This block has one line around it \u2013 going from the front of the boom, around the sheave and back to the start of the 3:1 purchase.<\/p>\n

\"IMGP0737\"<\/a><\/p>\n

Next, the 3:1 purchase starts with a block with becket.\u00a0 The line travels the same way as before, around a third block (the original one) at the front of the boom.\u00a0 It exits the boom starboard as before.<\/p>\n

 <\/p>\n

\"IMGP0738\"<\/a><\/p>\n

One problem I had to solve was how to attach the fixed end of the 2:1 line.\u00a0 The simplest solution was to drill a 1\/4\u201d hole through the front of the boom on the port side at the bottom, where the gooseneck narrows.\u00a0 I drilled the hole and reamed it out with a Dremel tool to remove edges.\u00a0 The line passes through the hole and is terminated with a stop knot.\u00a0 It\u2019s easy to pull out (when the outhaul is not under tension) and inspect for chafe.\u00a0 We\u2019ll see how it holds up. I\u2019ll probably add some chafe protection to it.<\/p>\n

Lastly, the line I used is some 3\/16\u201d Samson Ultra Lite<\/a>, which has a core of Dyneema and a polypropylene cover. The Dyneema means it should not stretch much (a good thing when the wind gets up).\u00a0 I had a length of this from a previous project (that didn\u2019t work out).\u00a0 Problem is that this stuff is really hard to splice because it\u2019s so small and tightly woven.\u00a0 That\u2019s why I used a thimble and simple knots instead of splices. This stuff is immensely strong so I don\u2019t care if it loses half its strength at the knots.<\/p>\n

The line for the 2:1 purchase is about 16 feet, and for the 3:1 is only about 10 feet.\u00a0 I may shorten the latter once I get the sail on.\u00a0 No need to have unused line dangling on the boom.<\/p>\n

Anyway, the resulting systems works great \u2013 at least on the bench.\u00a0 I have about 1 or 1.5 feet of motion of the outhaul, more than I need.\u00a0\u00a0 Very keen to see how it works out in practice.\u00a0 The 6 to 1 purchase seems very effective. I can put a lot of tension on the outhaul with just one arm.<\/p>\n

Update: April 7, 2012<\/strong><\/p>\n

The plastic bearings on the outhaul slider were worn, and one broke off as I was messing with it. \u00a0I replaced these with nylon bushings that I got from the local Henerey’s Hardware Store. \u00a0They are just under 0.5″ ID, 0.75″ OD and about 0.375″ long. \u00a0I cut them to a length of 0.25″. \u00a0I then soaked them in very hot water for a few minutes and forced them over the barb at the end. \u00a0It took some persuasion with a wood block and hammer to get them to stretch over the lip. \u00a0But it worked well, and they fit nicely into the boom and won’t come off. \u00a0We’ll see how they hold up over time. \u00a0The original bearings are just plastic, they don’t seem to be anything special. (See update below for August 2016, when the slider failed, breaking at the piece of metal that runs through the track in the boom).<\/p>\n

\"\"<\/p>\n

 <\/p>\n

Update October 2012<\/strong><\/p>\n

The summer is over and our sailing trip to Canada and around Vancouver Island gave plenty of opportunities to use the outhaul. \u00a0It works **great**. \u00a0The purchase makes it possible to tighten the outhaul under most conditions with ease. \u00a0Only when the wind is up and the sail is fully loaded does the purchase not enable me to tighten it. \u00a0Luffing momentarily does the trick of course. \u00a0And I’ve no worries about the damn line breaking. \u00a0The only change I’d make is to ensure it won’t hang up on any fasteners that stick into the boom too far. \u00a0Some of the fittings were installed by previous owners with very long screws, and the blocks on the inside can run into these when the lines are not tight. \u00a0Easy to shake loose though. \u00a0Someday I’ll shorten some of them, but for now, it works just fine.<\/p>\n

Update August 2016<\/strong><\/p>\n

During our Pacific crossing this summer, we had four weeks of mostly non-stop\u00a0strong winds, and during this time the outhaul failed in two ways: the slider holding the clew to the boom broke off, and the internal lines twisted and could not be pulled. \u00a0The metal plate between the internal and external parts failed from what looked like metal fatigue. \u00a0Fortunately, with a loose footed main, the clew simply lifted a little higher off the boom. \u00a0Also, the lines twisted and became stuck when the outhaul was pulled in tight which was what\u00a0we wanted for 95% of the time. \u00a0But it was a bit unnerving.<\/p>\n

I will be replacing both internal blocks with blocks that have swivels to hopefully eliminate the twist that was likely caused by the wire under tension untwisting a little. \u00a0And I will replace the wire with a piece of dyneema, shackled directly to the clew of the sail rather than the slider. \u00a0I will add a loop of Amsteel around the boom and through the clew to keep it within a couple of inches\u00a0of the boom.<\/p>\n

I also have found that fasteners protected with TefGel do indeed come out after several years with little sign of corrosion. \u00a0However, the constant shaking and movement of the boom seems to lead to some of the screws on the boom backing out. \u00a0I will be replacing the TefGel with some Loctite-Blue, hoping for good corrosion protection without the problems with fasteners falling out.<\/p>\n","protected":false},"excerpt":{"rendered":"

OK, so the sailing season is over for us, and I have started several projects, including tearing down the boom.<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3,9],"tags":[60,61],"_links":{"self":[{"href":"https:\/\/svrainshadow.com\/index.php?rest_route=\/wp\/v2\/posts\/983"}],"collection":[{"href":"https:\/\/svrainshadow.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/svrainshadow.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/svrainshadow.com\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/svrainshadow.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=983"}],"version-history":[{"count":33,"href":"https:\/\/svrainshadow.com\/index.php?rest_route=\/wp\/v2\/posts\/983\/revisions"}],"predecessor-version":[{"id":1422,"href":"https:\/\/svrainshadow.com\/index.php?rest_route=\/wp\/v2\/posts\/983\/revisions\/1422"}],"wp:attachment":[{"href":"https:\/\/svrainshadow.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=983"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/svrainshadow.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=983"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/svrainshadow.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=983"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}