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      Abbreviated rules   07/28/2017

      Underdawg did an excellent job of explaining the rules.  Here's the simplified version: Don't insinuate Pedo.  Warning and or timeout for a first offense.  PermaFlick for any subsequent offenses Don't out members.  See above for penalties.  Caveat:  if you have ever used your own real name or personal information here on the forums since, like, ever - it doesn't count and you are fair game. If you see spam posts, report it to the mods.  We do not hang out in every thread 24/7 If you see any of the above, report it to the mods by hitting the Report button in the offending post.   We do not take action for foul language, off-subject content, or abusive behavior unless it escalates to persistent stalking.  There may be times that we might warn someone or flick someone for something particularly egregious.  There is no standard, we will know it when we see it.  If you continually report things that do not fall into rules #1 or 2 above, you may very well get a timeout yourself for annoying the Mods with repeated whining.  Use your best judgement. Warnings, timeouts, suspensions and flicks are arbitrary and capricious.  Deal with it.  Welcome to anarchy.   If you are a newbie, there are unwritten rules to adhere to.  They will be explained to you soon enough.  

kubark42

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About kubark42

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  1. Low Friction Ring Anarchy

    That would probably do a great job of removing chafe issues, but it wouldn't address that soft shackles are tricker to open/close than hanks.
  2. In-boom drum for tensioning outhaul

    My calculations show that in the case of a monohull, I will either be just a smidgen on the weak side, or a few times stronger than need be, depending on the weave and modulus. Since I'm ignorant of how those eqn's arose, and they were for a different type of boat, prudence dictates I treat them conservatively. (Plus, I don't really know the provenance of the tube, aside from it being a broken spinnaker pole. My estimate of the yield strength could be all wrong.) Interesting that you broke the pin on the furling handle, that's a really thick pin on my boat! I want to say 5/16" or so, so it blows my mind that this could ever fail by torque applied from the sail. It would seem that the sail cloth would shred long before that pin breaks. I wonder if your pin/handle assembly is different from mine? I know that the Corsair manual says that reefing can be done at any point (so long as you can lock the handle), so your pin failures kind of leave me scratching my head. Thanks for the comment, though! Reading through the manual just now I finally realized that my outhaul was run wrong this entire time. The PO had it tied to the clew track, whereas I now see that the manual has it running through the clew and back to the cleat horn. I had always wondered what that horn was for, and was only using it to suck up dangling line from the outhaul. Now I see why it's important to have in my new boom design. The F27 manual does suggest that when you roll up to the reefing points, that you detach the outhaul and reattach through the new reef cringle (like you suggest). They state "This gives slightly better sail control for better sail- ing efficiency."
  3. In-boom drum for tensioning outhaul

    I really like a ratchet as part of the solution, I called Harken a few hours ago to ask them which failed first, the pawls or the bearings. They're very confident that the bearings will crush due to the load, long before the pawls break. So this is great! @Alcatraz5768, I'm having trouble understanding how you tensioned your outhaul. Did you pull on a rope or have a crank handle?
  4. In-boom drum for tensioning outhaul

    Thanks. I'm only guessing, but by having a sail that is headed toward a boomless design I think they can get more sail with less helm. However, boomless requires a more precise sheeting angle, because the boom is no longer designed to take the full horizontal load. The latest F-boats don't have a boom at all, just a sturdy reef which is stiff enough to serve as the center of the rolled sail. I don't mind futzing around in the beginning while I dial this in, it gives me something to do while I'm otherwise idle. It's fun to try to think of better ways, although I admit it's not every day I find them. Glowstick used a CF windsurfing mast, with aluminum at the boom end and G10 at the gooseneck. Frankly, I'm questioning myself because I know I don't know what I'm doing. I find little nuggets of information here and there, but I don't feel I have the experience to judge if I'm seeing the whole picture. However, the new boom did hold up fine in our speed runs yesterday, and we reached 18.4kts with 1.5 reefs (possible to have half reefs with a roller boom). So it's plausible we could be loading it even more in a huge off-shore puff, but it's hard to see the scenario by which we double the loading on the boom, the ama was already close to submerging. In my experience, the F27 is amazingly stable in a DDW scenario with the mast sheeted in hard and the traveler centered. The jib gives plenty of speed to have rudder authority, so there's no tendency to head up, and with the ultra-wide stance of the floats it's impossible to enter a death roll. Not saying this is the best way to ride out a storm, but it works great when you need a breather.
  5. In-boom drum for tensioning outhaul

    Correct me if you see it differently, but a free-body analysis the clew<-->mainsheet is going to exert as much force as the clew<--> strap#1 / strap#2<-->mainsheet combination will. So either approach leads to clamping forces between the strap and the boom, right? After a quick analysis, I believe that there is less friction on the boom with the proposed approach, since it is only the pinching force which provides friction, whereas in the velcro strap technique the sail load is the force. Consider the following sketch: On the left we have the velcro strap approach, on the right we have a clew<-->main approach. The black circle is the boom cross-section and the red curves are the straps. Because the force in the red line is identical between the two, it must be identical at the points P11 and P21. And it follows that the forces from P21 to P23 (right boom) are the same for the equivalent section of the left boom. Thus, because the P23 to P24 section is absent in the right boom, we can conclude that the loading on the right boom will always be inferior to that of the left boom. Since friction in this case is only a function of loading and surface area, and both the area and loading are reduced on the right boom, it will have less total friction force. The conclusion is that the strap is freer to slide fore-aft on the right boom than the left. This should mean that the clew control is enhanced when connecting the mainsheet to the strap. Does this make sense? I'll test my theory this afternoon, it's a blustery New England 30kt day here. P.S. There is a valid critique of the model above about what happens if the clew is actually touching the boom. I don't really know, to be honest, but I do know that the boom will typically migrate to the middle of the strap, so as long as the strap is sufficiently long they should not come into grinding contact.
  6. In-boom drum for tensioning outhaul

    @duncan (the other one)These guys are competitive in the fleet, and seem to have found a nice solution to putting the mainsheet on the clew. It's not complete apples-to-apples, because Glowboat's main has more roach, and thus is closer to a "boomless" main with the consequent lowering of outhaul and gooseneck loads. Still, it's a convincing representation of how it can be done, including the snapshackle which allows for easy transfer to the secondary strap when reefing, as well as a somewhat useful dually redundant system.
  7. In-boom drum for tensioning outhaul

    Tried and true is a great way to run a marriage, but a lot less fun for hobbies. I'm not expectant that I'll discover anything new, but the process is fun and the conversation and analysis leads to new understandings. Some ideas aren't done because they're hard, some aren't done because they're stupid. It's good to periodically revisit questions and see how new techniques can make hard ideas easy. If you disagree with the lack of boom vang, feel free to take it up with the F-boat crowd. It's been a very successful boat and current models don't have it. The argument is that we can always attach a barber hauler if we need it. We're getting seriously off topic, but I'm open to an argument for why the outhaul and mainsheet should be independent. I've seen the assertion, but I don't see the logic behind it. So long as the outhaul is short and doesn't stretch more than a few %, and the mainsheet is pulling at an almost 90 degree angle, the distance from the clew to the boom end stays effectively constant (it's a measurable, but not noticeable difference of micrometers). Of course, once the mainsheet carries the entire horizontal load we can see that the outhaul is no longer controlling sail shape, and that would seem bad. But in light wind this weekend, I didn't see that issue arise on my specific boom.
  8. In-boom drum for tensioning outhaul

    I think you took my answer out of context. You're claiming that the clew is less free to move than previously, and I don't see it. I also can't imagine why I'd ever want the clew to move on it's own. It seems to me that during a puff, the more rigidly mounted the clew the less likely the sail is to change shape and increase power. Sorry, I suppose I was moving a little fast. I understood that you were using an eccentric disc, which in a generalized sense is a cam of constant radius. I think that's pretty smart. I don't yet see how you modified a ratchet sheave for this, though. If you have an offset axle, wouldn't that have required drilling new holes in the sheave, and thus bypassing the ratchet? Since the ratchet is one way, how did you ease the outhaul? Did you have to access the sheave to disengage the ratchet?
  9. Low Friction Ring Anarchy

    @sysunday, I'm confused which of the two is the "V" shape. I can see it both ways, although if I had to bet I'd say the one on the left.
  10. In-boom drum for tensioning outhaul

    I'm doing it that way for a few reasons: 1) the increased mainsheet angle helps transfer more of the lateral load to the traveler, instead of the gooseneck. 2) It dramatically reduces vertical loading on that section of the boom. 3) It eliminates a torque on the boom. I'm still roller reefing, though. I have to move the main to an aft strap as you point out. More annoyingly, I have to move it to that strap for raising and lowering the sail. So for that alone I'm not sure if I'm going to keep it. It seems that the odds of something going wrong during that phase are much higher than the odds of the boom breaking. I'm curious what disadvantages you see to doing it this way. I don't immediately see why the clew would be any less free to move than it was on the earlier boom, where it was shackled to an outhaul track. This is great! I love your solution of a cam. With a printed profile, you can precisely tune that to meet your exact needs (minus the outhaul stretching). Do you have pics? How did you prevent if from unspooling? And how did you apply torque? Were you happy with it in the end?
  11. In-boom drum for tensioning outhaul

    @mizzimo, the equations come from http://www.academia.edu/22299709/Calculating_Mast_and_Rigging. I've seen them in several places, and the general methodology checks out. I suspect that these approaches are highly conservative, and am uncomfortable using them without specific justification. Regarding what I mean by a winch drum, maybe I was outsmarting myself with that wording. Think of a fishing rod with a direct driven reel. This is basically exactly what I propose, and if I could find a reel which would handle the load and fit inside the 4" boom diameter I'd be done! But using a winch handle the force multiplier is going to be huge, so there's no need for gearing. I think you're right that we could consider it an unpinned structure, but the challenge is to understand how much loading there actually is. According to the NBS, the 4" CF tube I'm using, with 1/8" wall, is at around the right size. Depending on the yield stress you choose for CF, it's either slight below, or significantly above the required sectional modulus. I think my F27 boom must be the same as yours, with the anchor point being slightly in front of the reefing track. I can do this, but it'll be a PITA to reinforce the CF tube there, because I'll either have to reach inside somehow, or figure out how to glue some g10 reinforcement to the outside. Otherwise, the CF will simply split (which is exactly how it failed in its earlier life as a spinnaker pole on a 43' offshore racer).
  12. In-boom drum for tensioning outhaul

    @allene222, I see what you guys mean. However, on the F27, typically reefing is done by roller boom furling, so there are no reefing lines. I had considered exactly the plan you suggest, where there's an initial block and tackle behind the clew, in addition benefiting from an almost free cascade through the clew. However, the downside is that this still leads to substantial additional load on the boom. I don't meant to say that's unacceptable, the F27 has been an indestructible boat, with 500+ made and very few lost to structural failure. So clearly it's okay to do things the way it was done. It's a mental floss exercise to see if a better way exists. @Haligonian Winterr is spot on that the sail is not adjusted much while sailing, and with only 4:1 in my experience it is impossible to tighten under load. I'm hoping to go for more. A 1cm drum driven by a 20cm winch handle would certainly do that! I tried the new boom for the first time yesterday on a sail to Boston, in 6-10kts of wind. I think my theory is right that there is very little horizontal load applied from the clew-mainsheet strap. I was able to move it around by hand, which means it was contributing max 10-20lbs forward thrust. I suppose in a more upwind scenario there will be more friction because the straps will be tighter, but it's clear that in my configuration, the vast majority of the load will come from the outhaul. I suppose I could add an element so that drag from the strap increases, maybe gluing some thin leather strips under the straps. That would also prevent me from as easily adjusting the outhaul while under load, so I'm going to give some more thought to novel ways to do this.
  13. 4" Carbon Fiber Tube as Boom

    Took it sailing yesterday, worked out great! I even hit my head on the boom while loading it onto the car roof rack and I can report it's much softer than the aluminum boom. One issue is that it's a little more annoying to use the roller-furling part of the boom. I need to polish that part a bit, and figure out how to keep the topping lift from walking forward. Another issue I noticed is that without the bolt groove on the top the boom is a very slick place to put fingers and hands. That's a problem when you're trying to stabilize yourself by reaching out to the boom, so I need to do something to make the surface less slippery. Another thought is to wrap the boom in a single helix of fibrous rope, which will give plenty of purchase as well. Lastly, could try painting non-stick. Does anyone have a favorite approach?
  14. In-boom drum for tensioning outhaul

    I'm sailing a trimaran, and when the boom-vang padeye popped off last year (fatigue cycling on a 25-year-old part), Ian Ferrier and the rest of the F-boat crowd assured me that if I was using the vang, I was sailing too far downwind. The consensus is it's faster downwind to sheet in and head up for boat speed, or, if I really wanted to sail that far off the wind, use a barber hauler from a float. So the vang is gone from the design. I've looked around for data on spec'ing outhaul loads, and came up empty. It's reasonable to assume that since the outhaul is the only lateral load on a the sail, it is the source of all boom loading (this assumes that the mainsheet is (almost) vertical). Thus, lacking a source on outhauls which says otherwise, I'm going to assume that the outhaul tension is equal to the boom design force. The Nordic Boat Standard (NBS) design equations for my boom suggest a maximum design load of 7000N, or about 1400lbs. Now, it seems grossly incorrect to use monohull design standards for multihulls, and it is. However, lacking another source, it seems reasonable to start there and get orders of magnitude right.[*],[**] According to my understanding of NBS, the ultimate boom design strength is to resist this compressive buckling load, so it makes sense to seek to avoid an extra 1400lbs of force in the system just because I didn't think things through. If it's the best way to do it, I'm cool with that, at least I'm aware of the design trade-off. One thing to consider about the outhaul is that the max design load only applies to the static system, that is to say you'll never expect the human to be able to increase outhaul tension at a moment when the sail is maximally loaded. So we have two design points, one is the maximum force the system needs to be able to sustain, and the other is the force the system needs to be able to exert when being trimmed. This actually makes the problem a lot easier, which is why you can design a typical 4:1 outhaul system which can sustain a 1400lb peak load. A winch drum, without the gears, seems like a very light and compact way to locate the outhaul purchase system behind the clew. It has the advantage of having a potential for a huge force multiplier, and the torques are small when compared to the side loadings. So the upshot is that when you design a purchase for a 7kN load, it's already sturdy enough for 50Nm (the torque a typical human can generate on a winch handle). I'm glad to hear that this has been tested by the lead screw @allene222 mentioned, and maybe it was rejected as problematic because of the KISS principle @duncan (the other one) brings up. However, I don't agree that a single drum mounted on a spindle with no extra parts is significantly more complex than a series of cascaded pulleys going the length of the boom, and it certainly seems like the inertia for a drum (think how light bicycle sprockets are) will actually be less than the combined inertia of pulleys, mounting hardware, and rope. Assuming a drum is a good solution mechanically, one thing I don't immediately see is how to block it from being back-driven. I could put a jammer cleat just behind the clew, which would nicely transfer the load to the boom, but I don't quite see how I easily release tension. It would be a one-way process. Plus, I'm not sure a simple jammer won't slip in a 7kN scenario. P.S. I'll see if I can work out some of this in drawings to help show the concept. [*] A rope which with a >1400lbs breaking load is dirt cheap these days, e.g. 7/64" (2.8mm) dyneems goes to 1800lbs. Go to 5/32" for safety factor, and if you want to tie knots instead of use splices opt for 1/4". This approach seems pretty consistent with the outhaul sizes I see on big boats, where you can have something as big as a 1/2" line. [**] I wish the NBS equations for boom moment of inertia mentioned where the outhaul purchase was in their design. From the resources I've found online, they simply don't mention it. Perhaps on captive footed sails with a boom vang the ultimate stresses requ
  15. I have a 4" CF tube which I just turned into a boom, and am now in need of an outhaul. I was thinking an in-boom purchase system, which places a big section of the boom under a double helping of stress, isn't ideal. Instead, I think it'd be fun to try to do this with a drum, and figure out how to do a force multiplier. Has anyone ever seen something like this done? It seems so easy and robust, I figure there must be something I'm overlooking. Printing parts up on a MarkForged means I can reinforce everything with continuous strand CF, so if strength was the limiting factor I think I can get that sorted out.