DaySailer.org Forum

Mine is a Schaefer setup, but basically matches the picture you posted of a Harken setup. I see you also have the jibsheets cleated to the top of the CB trunk, My old Widgeon was set up that way, have often considered doing it on my DS II. But, I remember tripping over the jibsheets a few times on the Widgeon, so will most likely stick with the original setup of the jibsheet camcleats mounted to the fairleads on the tracks. (plus, rigging them as they were on my Widgeon would mean they would run right across my Dad's lap when he sails with me and sits forward, leaning back against the aft bulkhead of the cuddy <GRIN!>!

Very nice! I wish I could get my dad on the boat. But his knees are no good anymore. Yep, unfortunately what I inherited, had to be changed. But I do love that setup now. As for the jib sheets, I have not really tripped over them. But, that is kind of all I have known really (for the most part). So, I actually remember they are there. I thought about trying to convert it to setup where I could quickly (on the water) move the jib sheets from a "cleat on centerboard" scenario, to a cleat on coming/slider track (as originally setup). When I have more than 2 people in the boat it gets crowded, and depending on who that 3 rd person is that is with me, I may forgo sailing with the jib altogether. Don't need any kids tripping and going splash.

The first couple of sails out, where I actually had some wind/tension on the jib, it was a real pain to un-cleat that jib sheet, so I am not sorry I changed it. I can actually operate it now. None the less, think the perfect jib sheeting system would include a pivoting block/fairlead/cleat combo the sat upright on the rail (so you could cleat and un-cleat by pulling up or down)... convoluted... yes. But I think it would be a bulky contraption, and furthermore I have not found parts to rig such a thing yet lol.

Going back to discussion of where to put ratchet blocks in the system . . . .
Following suggestions on the thread, I moved my main ratchet from the swivel cam on the CB trunk to my stern traveller, the only position where the sheet turns a full wrap around the block and takes full advantage of the ratchet.

Too much advantage, I have decided. There was a scary delay between giving a couple of inches of slack at the swivel before the sail actually eased. It was only a second, but with the side deck already in the water in 18kt winds, time passed slowly. The angle down to the main swivel and back up to my hand is greater than the 90-deg bends on either of the boom blocks, so rather than moving the ratchet to any other position, I am just going back to making it the last turn before the cam.

This is my engineer brain thinking out loud... But I would imaging locating the ratchet block each turn further away from the first turn in the system would slow down the release. I think the ideal location would be on the swivel cam itself, granted you have enough angle in the turn. However, when sitting inside the boat (vs on the rail) you may not have at least 90 degrees on a reach, which seems the ideal angle for the ratchet to effectively engage/hold. The next step back is mid-boom. I have a simpler vang sheeting system (no traveler), and this seems to be a fine spot for the ratchet (in my case). The ratchet does not ever really release, unless I let it completely go slack. Which seems ideal, as then all adjustments/gear shifts are minor (one gear up/down at a time) unless trouble is lurking, then a full release is available. Prior to the ratchet (and swivel cam) I am pretty sure that I shifted down to first gear every time I made an adjustment.

We don't have all the facts to form an opinion on the likely cause of what Talbot observed.

There are some differences between a 180 degree wrap and a 90 degree wrap that are independent of where along the line the block is located.

There are also differences among ratchet blocks (or their settings). There are blocks that do not ever rotate backwards. They rely on the rope overcoming the friction (which is lessened by being slack) to slide backwards through the sheave. The friction on circular wrap grows something like exponentially with angle. (I was astounded when I read that one for the first time, but explains why taking even a partial turn around a bollard with a dock line helps wrangle even rather large boats).

The amount of friction for the same line geometry can vary by a factor 2, based on the design of the sheave.

There are blocks that have an "auto" mode, in which the ratchet disengages if the pull on it (away from its support) falls below a certain value. After that, the sheave spins backward. For a 90 degree configuration, the two parts of the sheet do not pull in the same direction. This reduces the effective force on the support for the same tension in the sheet (70%). It takes less reduction in line tension to release the ratchet.

There is also the effect that, while the tension in a line roved in a purchase is ideally constant, friction in any sheave needs to be added. When you are using a purchase to move something, that friction acts to you disadvantage. You have to add its effects to the total force with which you pull at a given load. When your aim is to "hold" a load, the effect is reverse - and it's precisely this effect that we use when adding a ratchet block.

If there is substantial friction in the system between you and the ratchet block, you'll need to slack the rope more than without to get the same reduction of tension at the ratchet block. That effects both the case where the tension is used to slide the rope backward, or where the slacking signals the block to disengage the ratchet.

Finally, in a 180 degree configuration around a ratchet block, the friction may be so significant that the unreleased side holds fairly tightly while the other side is being released. Enough, for example, to prevent the ratchet from disengaging until a bit of rope has slipped around the sheave and allows the ratchet to move towards its support a bit, thus disengaging the ratchet. There may also be some effect where the tension gradually increases from the already loose end towards the tight end, as each partial circumference of the sheave adds friction.

In a 90 degree setup, if there's uneven pull on the block, it will not hang at 45 degrees. It's also able to move a bit when the "free" end of the line is released. That may aid the ratchet in disengaging.

If the sheet is (slightly) stretchy, all sorts of additional effects might be expected, especially in multi-block purchases.

I have my ratchet block at the forward 90 turn (from the boom down) and I chose a model with high holding power and auto release. All I can report is that that combination works brilliantly for me under typical conditions. I have the jibsheets on the same type of ratchet and just yesterday was single handing with both sheets held in the same hand.

The comment about sitting in the boat is important. In general, if the wind is light enough that I can sit on the tanks, I don't really care about the ratchet or the angle at which the line exits the system. The whole point of extra purchase or more complicated blocks is to help out when the wind is strong.

I used to make fun of the "systems thinking" buzzword when in first came up in business and education, but a boat is a good illustration of how if a solution is optimal for one configuration of equipment, uses, technique, and aesthetics, you can't change any element without changing the system. You either have to come up with a new configuration or put it back the way it was.

On the DS I that I recently purchased, I plan on replacing all the blocks for the mainsheet. I will be putting a rachet block with the cam on the centerboard trunk. I have added a rachet block into the mid-boom setup on my Mariner and have found that it has worked well. On the Mariner however, I placed the rachet block on the boom. My DS II will get a similar upgrade as well.

John

talbot wrote:The comment about sitting in the boat is important. In general, if the wind is light enough that I can sit on the tanks, I don't really care about the ratchet or the angle at which the line exits the system. The whole point of extra purchase or more complicated blocks is to help out when the wind is strong.

I agree, in light winds, there's less need for holding power from the ratchet, so if it's not optimized for holding power, that would not be critical. In (very) light winds, you do want it to release cleanly - some ratchets that don't disengage have too much residual friction (wind won't be able to push the sail out as you are turning downwind for example) and people start turning the ratchet function off, manually. (Not necessary on the one I use, the auto setting does what it's supposed to, and does it well).

If 90 degrees does not give you enough holding power in stronger winds, one option is to look for a different make of ratchet and rope. The ratchets are not created equal, and the differences are not minor. In fact, the difference in holding power can be as much as 2:1 (test results from a sailing magazine). Likewise, a very slippery rope probably defeats the purpose.

talbot further wrote:I used to make fun of the "systems thinking" buzzword when in first came up in business and education, but a boat is a good illustration of how if a solution is optimal for one configuration of equipment, uses, technique, and aesthetics, you can't change any element without changing the system. You either have to come up with a new configuration or put it back the way it was.

Sail and rig trim are good examples of that. Many adjustments are not cleanly separate in their effects. However, as I suggested above the quote, in this case, it would seem to me you do have other alternatives than just the two locations for the ratchet block that you have explored.

If any of this info helps...

I think I remember GL also mentioning that the holding power of the Ronstan is greater than the Harken auto ratchet blocks of similar size. GL uses the Ronstan if I remember correctly. I have used the Harken on my boat, which is also adjustable. I have it set to not catch until more resistance is applied than the stock setting. Also, my ratchet is on a 180 degree pull located mid boom in a 3:1 configuration (fiddle, ratchet, back to fiddle, and terminate on the ratchet becket, and done). This works great for the vang sheeting style system on my DS II.

Point is maybe a weaker ratchet or adjustable ratchet will help you get the optimal setting you need in the mid boom location, which seems to be where you are falling back to.

Getting just the right amount of slip vs. friction is tricky sometimes with ratchet blocks. Being able to ease sheets smoothly and precisely is where I want my friction point. I think that is why most people that race use the Harken manual ratchet block. Though they don't hold as well as the Ronstan, at the same diameter, they do ease very smoothly. If you want to just let out a quarter inch or an inch of sheet, it happens smoothly and without having to think about it. I've got a 75 mm on the swivel at the centerboard. Yes, it's oversized but holds just right for me in just about all conditions. The only time I switch it off is in VARY light air. In light air I would be flying the UPS and have plenty of pressure on the main.

I don't know how it is with the newer Ronstan blocks but with my older ones, which held quite well but did not ease smoothly, I would have to do a quick pull-in to get them to release when they were under a heavy load (definitely not optimal). This was on my UPS and a 180° wrap. I replaced those with Holt-Allen. They hold just about right and have just the right amount of slip, though I did go from 40 mm to 55 mm.

There are exogenous variables to consider. Such as, we owe on our taxes, and new expenditures on things like boats, musical instruments, and home decor are suspended until future notice. Well, OK, we bought a new toilet seat yesterday--you have to relax once in a while--but in general, the existing equipment is a nonnegotiable constraint on design.

Toilet seats or new ratchet blocks. What trade-offs we are forced to make

Went sailing today and due to the light winds we kept the ratchet turned off. The definitely worked better with the ratchet off. No solution for the shifty winds however. We were out 4 hours and experienced a 180 degree wind direction change. Afraid no block helps that.

John

Large wind shifts are fun. Especially in lighter airs. Was out earlier this week and a wind shift hit just while we were tacking. I kept turning, turning, turning, trying to fill the jib, and when it finally did, we were sailing straight back where we had come from. Had this been a race, we would have kicked ourselves, but we were just enjoying a balmy evening and nice sunset. We also had a moment or two where the wind changed 180 degrees between the surface and the mast top, with both sails experiencing different winds. Those are also fun.

Back to ratchets: as mine (Ronstan from about 5 years ago) disengage fully when the sheet isn't tensioned very much, they don't get in the way at all during light winds. I have another boat with an older Harken design, and that gets turned off manually unless I need the ratchet action.