Mainsail Reef Line Load Calculation

[deluxe68]

Just heard back from Harken technical support. They recommended the Cruising 57mm ESP blocks #6059, about a hundred dollars safe load of 2205 lbs. I think I will go with the 75 ESP with a load rating of 3500 for $15 more. Thanks for everyones input.

[thinwater]

Originally Posted by StuM

All the above info is good, but remember that your slab reefing system has a double line from the boom to the clew and back to the boom, so the line load is very roughly halved.

Yes. Due to friction, it is more when pulling in, but it generally is not sheet hard then! About half again due to friction when just holding (do the experiment, depends on the line and the ring). So the holding force is probably about 1/4.


And as others have said, the reefed load at 40 knots is probably not much different from the full sail load just before reefing. That has always been my impression. Same heeling force being resisted by leach tension. Thus, reefing gear is usually the same size as full sail gear.

[Tillsbury]

Originally Posted by StuM

All the above info is good, but remember that your slab reefing system has a double line from the boom to the clew and back to the boom, so the line load is very roughly halved.

At least. I just moused my reefing lines to clean and end-to-end them and found they were on a 3:1 in the boom. I thought there was a lot of rope!

[Menlim3]

I have having difficulty chosing which deck organizer to purchase. We have a 45 ft boat. Bringing all lines to cockpit. Have chosen harken 75 esp for main halyard. Harken 75mm triple for 3 reefing lines. Newmar d2 clutches. All good for 12-14 mm rope. Which 5 sheave organizer would match? Spinlock t50 good enough?

[deluxe68]

Originally Posted by Menlim3

I have having difficulty chosing which deck organizer to purchase. We have a 45 ft boat. Bringing all lines to cockpit. Have chosen harken 75 esp for main halyard. Harken 75mm triple for 3 reefing lines. Newmar d2 clutches. All good for 12-14 mm rope. Which 5 sheave organizer would match? Spinlock t50 good enough?

I keep going back to Harken for most stuff as they seem to be more robust than most and they are typically rebuildable. I went with Spinlock XXA clutches because they had a higher load rating than Lewmar. It sucks that they only make them in singles. I decided to spend a bit more on them and will not have to worry about them being undersized. The Harken midrange is not much more expensive and the load rating per sheave jumps from 2200 to 2600 lbs. Their big boat range is 10 times the price and 4 times the load ratio, definitely overkill. We have Harken 75 ESP for reefing lines, decided to go with the black magic 75 for the main halyard.