Erine, as I said, I don’t know if you will be able to achieve the Botts’ Ideal with the cut of your current sail. The good news is you have not bent your boom so far so so there may no be enough force involved to bend the boom.
I am not sure have both reefs tied in will change anything.
Mark Powers
I’ve been thinking about this for a couple of days, and wanted to chip in with a question and a comment.
The question. It’s been 50 years since my college physics on static and dynamic load vectors. I’m wondering if there’s an engineer among us who could comment on the concern about the force of the sail pulling on the aft reef line being sufficient to actually bend the curved aluminum tubes that form our wishbones. My guess is that the amount of force required would probably tear the sail or pull out the reef clew cringle before the booms bent. Is there an engineer in the house who could speak to this?
The comment. I was always taught regarding conventional sails that the key issue is maintaining sail shape by ensuring that the forces on the sail clew were approximately equally distributed horizontally along the foot and diagonally along the leach. So my guess is that the advice about how close the reef lines should draw the reef clew to the wishbone is really more a rule-of-thumb. I think it serves as a stand-in for making sure that the clew’s positioned right relative to the wishbone to help in maintaining sailshape. A bit above but relatively near vertically, so that the weight of the wishbone can do its job as a vang. Relatively near horizontally so that the choker can do its job; the further away the clew is, the further back you’d have to pull the choker to keep the sail from balloning out rather than flattening down.
Between the wishbone, the choker, and the topping lift, there’s probably enough adjustability to make up for minor differences in how tightly the reef clew’s pulled in. Getting the reef clew positioned as suggested by others in this thread does minimize the need for tweaking them, though.
My $0.015 (originally two cents, but nothing’s worth what it used to be).
– Bob
Me Gusta
Nonsuch 26U #233
I’m not an engineer Bob but I am a builder and I can’t see how anyone would mount the cheek block vertically on the inside of the boom if the reef line was was to be pulled tight back and near horizontal. It would seem to me that that alignment would dictate that the cheek block be mounted horizontally on the top of the boom or at least moved in that direction to split the difference. Given that they did mount it inside the boom I can only conclude that the intended lead to it is from forward.
As for the boom bending force, when you approach horizontal that is up to how strong you and your winch are, not just the pull of the sail.
As I said, not an engineer…
IMHO, both of you guys are dead right. The cheek block is not well positioned and, possibly, should be a floating block, maybe lashed to the boom such that it could assume the best position, always. I will try this approach (when the snow goes away and it’s not -20 degrees C. It’s (sort of) the same conundrum that exists with the choker cheek block high up on the mast. I, and others, have tried (and maybe stuck with) a floating block that is attached to the original choker cheek block but floats a bit forward of the mast. It will always end up in the optimum position.
Damn cheek blocks …
I’m not a builder or an engineer but I did love high school physics. In my heart of hearts, considering how far back the reef cheek blocks are, I am having a hard time imagining that normal forces in a REASONABLE wind (not a roaring gale or worse) would actually bend curved aluminum the wrong way. I think that Bob is correct in assuming that lots of other things would fall apart before the boom even thought of bending.
But, hey, what do I know !!!
Ernie A. in Toronto (where it is not nearly as cold as Maine)
Paul did have it right about the amount of damage one can do overtightening lines with a winch, though.
On the other hand, I’ve never found myself needing a winch when reefing. Can’t speak for the bigger Nonsuches, but at least in my experience, hand tightening gets the lines where they need to be as long as the sail’s at an angle to the wind which takes the pressure off, the topping lift’s a bit up, and the choker’s a bit eased.
– Bob
Me Gusta
Nonsuch 26U #233
I’ve never put my reef lines on a winch but I do understand that, on something bigger than an NS22, one may need to do that. I’d be careful, though. You can do some damage. I just daysail. If I got caught in something such that I had to use a winch to reef … I wouldn’t. I’d go with a less-than-perfect reef and put in to port … any port.
Ernie A. in Toronto
I am not an engineer nor a sailmaker/rigger so I am not arguing with Botts. I would have thought the threads in boom for the screws or rivets holding the turning block to the boom would be the first to give up.
The calculation of force need to bend the boom is probably very complicated. The boom is curved so gains some strength from the curve. The pull of the foot of the sail on the heel of the boom will (I think) try to increase that bend by compressing the boom. However, the arms of the boom are relatively straight as you move back along the boom so I am not sure how that would be taken into account, The aluminium alloy used in the boom would have to be know, along with the diameter and the thickness of the tubes. The latter two might be easier to determine. Here is a link to a calculation on the ability of aluminium to act as a beam. The load will change as the wind force picks up. Wave action will likely cause shock on a regular basis. Sort of like jumping up and grabbing the monkey bars.
Have to say I can’t do the math. I don’t even know what all of the symbols mean.
I have only heard of one Nonsuch boom failing and that was a carbon fibre boom on a 260 so the odds of one failing are not great.
Mark Powers
A number of years ago Ed Botterell made a sail for me. I was having a difficult time getting a proper shape when I reefed the sail. I met up with Ed to discuss the problem while I was in Toronto on a business trip. Another owner of a 26 in the Toronto area was having the same issue. Ed was going to the boat for a test sail and invited me along.
We headed out on to the lake in about 20 to 22 knots of true wind. The skipper asked Ed “First or second reef”. Ed replied “I don’t want a reef, I want to see how the sail sets first”. So full sail, full choker and off we went close hauled with the rail often dipping into the water.
Satisfied with the sail shape (it looked nice) Ed told us to put in a reef. I could only get the reef cringle to with about 3 feet of the boom. The sail below the cringle was blowing up over the top of the boom. Ed said grind it the reef line in. I asked how hard. He said as hard as you can you won’t hurt the sail. I was able to grind in about another 6" of line. I was sure the cabin top was starting to deform. Ed figured I was not trying hard enough so he stepped in. I am happy to report he could not pull in anymore line than I had.
Turns out even with the choker full slackened off, you can’t lift the boom with the reef lines. We were using the small cabin top winches with a 10" winch handle. The solution was to shorten the standing part of the topping lift so the boom could be raised higher.
We did not have to worry about bending the boom because we were not where close to having the reef line pulling straight across.
An old sail might not take kindly to that much force.
Mark Powers
interesting fact. If your main sheet breaks at the boom, you can regain control via the reef line. Happened to a friend with a 30 and that’s how he regained control
You got me here, Thor. The boom is way off of one side of the boat and the mainsheet snaps. Bang !! The clew reef line runs along the boom to the front of the boom and down the mast and back to you. Short of pointing the boat in the wind (which may be the solution, actually) how do you “regain control” ?? Undo the whole reef line from the boom ?? If so, why not just retie what’s left of the mainsheet to the aft end of the boom ? Neither way will you have a double purchase - you’d just have a single line.
Am I being clear ?? I do wonder …
Ernie A. in Toronto
It’s not pretty, but there is enough purchase off the reef lines to corral the boom and hold it more or less mid ships. You’re not sailing at this point just regaining control of the boom. Once the boom is more or less centred you can then fix it or tie it down.
Gotcha, Thor.
Ernie A. in Toronto