Rigging Single-Line Reefing for Tartan 3800

[flyhume]

Hello everyone. New owner of a Tartan 3800. She has the original Offshore Spar boom and is capable of an internal Isomat type single-reefing setup. However, the reefing lines, internal shuttle blocks, and double block that attaches to the top of the vang bracket are all missing. At this point, I’m planning to rig as original per the attached image.

Before I order parts, I’m curious if other have their reefing set up this way and how it performs. I know this will have more friction than a single-line system but I prefer fewer lines leading back to the cockpit and I'm not racing. I’m planning to go with either 3/8" or 5/16" Dyneema.

Thanks in advance, and if you have any other suggestions or recommendations, please feel free to share!

 

[Foswick]

Welcome to the forum. I don't have much to offer on this, but I didn't want your first post here to go unanswered for long.

I have used a similar setup on a race boat I crewed on. Works fine - pretty common setup. The additional friction is more than offset by the mechanical advantage.

You "could" simplify the rigging by removing the mechanical advantage of those mid-boom blocks. But, given your main is about 310 sq/ft, and the boom is already designed for this (just missing some parts), I think I would rig it as in the diagram. If you ever have to reef the sail in fresh conditions and can't completely get the wind off of it, you'll really want the advantage and might struggle to properly reef without it. Sounds like you've already made that assessment.

My boat is 35 feet LOA and I don't find I need the advantage. But ... I have a ketch rig, so my mainsail is quite small for a 35-foot boat, compared to a sloop. (My mainsail is just 207 sq/ft - so not a good comparison to yours.) Also, if I am unable to safely reef, I can always drop my main entirely and just use the jib and mizzen - which works great. So, I am less concerned about having to reef a sail that is still partially loaded with wind.

 

[Ted]

I have a similar setup on my C&C 110 with an Offshore Spar boom. My main is 349 square feet. There are a pair of "balancing blocks" inside the boom. These equalize the tension on the luff and outhaul lines. They do very little to increase the mechanical advantage of the reefing system. The single line makes it easy to reef from the cockpit. If your reefing lines are run through grommets in your mainsail like shown in the drawing, I'd suggest that you add some small high load blocks at those locations. A lot of friction can be eliminated there.

 

[Foswick]

They do very little to increase the mechanical advantage of the reefing system.

You know what? I stand corrected. Ted is right. Intuitively, I calculated that it would halve the force required, but it doesn't. For either rig (with or without the floating block), there is a 4:1 advantage (ignoring friction). In both cases, you pull in 1 foot of line to move the sail down 3 inches.

The key efficiency advantage is that the system doesn't use both grommets as pulleys, and the grommets are high-friction. Without that floating block, both grommets act as pulleys. With it, only one has to. But, as Ted suggested, you can reduce that.

Interesting - I've been thinking about this wrong for years.

 

[BarryL]

Hello,

As mentioned, it's a good idea to reduce friction in the reefing lines where the lines go through the reefing points. I used to use blocks but they are heavy and expensive. My sailmaker suggested low friction rings and those work very well. No moving parts, light, easy to use.

First pic is with a block (that eventually exploded), Second is with LFR.

Good luck,
Barry

 

[Foswick]

... in fact, this kind of sent me down a rabbit hole this morning, reassessing my understanding of this. Now that I do the math, I am convinced that, if you ignore that grommet friction, this system is less efficient than a simpler solution with no floating block. I actually can't see the advantage of the floating block. It does add the friction of two pulleys in place of the tack-end grommet acting as a pulley. And, friction at that point fights equalization of force. So, I can see some incremental benefit ... maybe. But, then again, I'm not sure that we don't prefer force being applied a little disproportionately to the forward grommet.

But, you could simplify the aft-half of the rig by fixing the end of the line on the shuttle, then aft around the turning block and so on, you have the same advantage but with one fewer pulley. It isn't intuitive, but that aft pulley on the shuttle actually doesn't do anything for you. Seems like it should, but it doesn't. In both cases, there is a fixed amount of line in the aft end of the system. Moving the shuttle one foot forward moves the grommet the same distance, whether the rope is fixed to the boom and goes around a pulley on the shuttle or it is fixed directly to the shuttle.

It makes me wonder why this is such a common design.

That said, I do know that some boats are rigged as I described - where the floating block has a pulley and a becket rather than two pulleys. I am convinced it is the better solution, but before this morning, I would have sworn it wasn't.

But, I do stand behind my revised position that you're just as well off without the floating block, especially in you use some low-friction solution at the tack grommet. Any advantages would be slight.

I am genuinely curious, though. Am I wrong on this? I don't think I am, but I was wrong the first time.

 

[dLj]

Hello,

As mentioned, it's a good idea to reduce friction in the reefing lines where the lines go through the reefing points. I used to use blocks but they are heavy and expensive. My sailmaker suggested low friction rings and those work very well. No moving parts, light, easy to use.

First pic is with a block (that eventually exploded), Second is with LFR.

Good luck,
Barry

Very nice use of low friction rings!

dj

 

[jssailem]

When considering the elements of friction in the rig, one assumes that the sail is pulling hard against the reef lines. If you reduce the force created by the sail, the friction on the reef lines is also reduced.

When slab reefing (I know old school, but it appeals to my theme "Sail Simple"), I bring the helm up short of dead into the wind, maintaining steerage with the jib/genoa. I then ease the mainsheet and the main halyard. At the mast, I pull in the outhaul on the first reef and secure it. I pass the luff reef kringle over the reef hook and then tighten the main halyard. Reef done.

Yes, this requires the use of a jackline, and harness + tether by the sail handler, but it is quick direct action that resolves the issue with few moving parts to fail.

 

[flyhume]

Hi All - Thanks for all the responses and recommendations! These are all very helpful. I'm not a great physics mind, but I think I understand the simpler approaches to rigging this. The attached drawings are how I visualize both - One without the shuttles, and one with an internal block with pulley and becket. If something looks off, please let me know. After reading Ted's reply, I also checked with a buddy who owned a C&C 110 in the mid 2000s (also had a red hull). He said his was rigged with both internal shuttles with double pulleys and said it worked fine. I will add the LFRs on the main reef points too.

 

[Sailfanatic]

The diagram at 3:30 in this video has fewer blocks and worked quite well. I would hesitate to skip the shuttle blocks inside the boom. You aren't likely to be able to find actual shuttle blocks, instead can end-to-end two swivel singles.