If you’re asking isn’t the pressure on the forward block roughly the same as the block that is feeding it then the answer is yes, but only because the line it turning a similar angle through the block. As Keith pointed out with his Harken reference (I was too lazy to go look for it) the number of degrees a line turns through a block has a huge impact on the block’s load.
The easiest way to illustrate this is with a bungee cord. If stretch a bungee to 40 lbs and hook it on a fixed ring the force on the ring would be 40 lbs. Hook an identical cord exactly the same and the force is 80 lbs or double. The same is true for a 180° bend through a block. If the line pressure is 40 ponds it will be the same on both sides a free turning block and there fore on each leg which is double like two bungee cords. So it’s 2x on a 180° bend. Now remove one bungee and push in the middle of the remaining cord until it deflects 5 degrees. You’ll not it only takes a fraction of the 40 pounds to deflect the center of the cord a few degrees. So the angle of deflection plays a major roll in the force on the block even though the pressure on the line is constant through the control line. Phil Agur s/v Wing Tip Secretary/Treasurer Call Sign WCW3485 IC27/270A MMSI 366901790 <http://www.catalina27.org/> www.catalina27.org Vessel Doc# 1039809 -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of Joe McCary Sent: Thursday, September 13, 2007 2:59 PM To: [email protected] Subject: RE: catalina27-talk: Traveler sheeting I have a boom vang (the image pictured is not my boat), but I find it near impossible to adjust under any load. The 3:1 block just isn’t enough in anything but ultra light air. About my question about the pressure on the forward block (see picture in link below), isn’t it the same force as the #3 block in the sheets (mid boom)? My new (uninstalled as yet) traveler is also the new straight Garhauer traveler. It seems massive! Joe McCary Aeolus II #4795 West River, MD [EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] I'm no engineer, but I would think it is. Its only purpose is as a turning block. It doesn't have the same pressures as the ones between the boom and traveler. I had the original curved track traveler so I re-aligned my mainsheet control to the traveler car. Now that I have the straight track travaler (Garhauer; fantastic!), I don't need to keep it there but I still do. You should seriously consider adding a boom vang. The midboom doesn't hold the boom down quite as good as the end-boom. Your sail shape will be much better with a vang. Bob -------------- Original message -------------- From: "Joe McCary" <[EMAIL PROTECTED]> As they say a picture is worth a million words (hey I am a photographer so I tend to inflate the value of a photo a bit). The image I am referring to is: http://www.delanges.com/Catalina_27/images/Traveler_2.JPG Its from Steve’s website and shows his mid boom traveler. My rig will be slightly different, with double ended sheeting. The folks at Catalina Direct suggested I run the sheet from the edge of the cabin top (near the handrail) forward to a spinnaker block on a spring then at a 45° to the first blocks on the boom and so on. In the image above, while just single sided, he runs his sheet to the mast then down through a turning block then to a deck organizer then to the cleet. My question to Steve was, it appears the block closest to the mast is held in position by a small stainless strap with just 2 sheet metal screws instead of a full through bolted bail on the boom, is this strong enough? Joe McCary Aeolus II West River, MD [EMAIL PROTECTED]  From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Thursday, September 13, 2007 12:28 PM To: [email protected] Subject: RE: catalina27-talk: Cruiseair on C27-alternative method Joe, you should have a boom vang running at 45* from the boom to near mast base. Running the mainsheet across this same area then makes sense, plus eliminating one block from the whole setup. I think you can see what I mean from pictures on my out-of-date website: mywebpages.comcast.net/sailrmann Bob Mann Windcatcher '85 #5928
