Mainsail outhaul block specification

DoubleEnder

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I have an old wooden sailing boat,34 feet LOA and about 5.5 tons. We are changing to a loose footed main for the first time. The Bermudan sail has about 400sq feet area and is comparatively low aspect. The outhaul system will be a 6 part purchase.
What size blocks should I use? I’ll use spectra line I think. I don’t want to oversize the blocks as I have a nice shiny varnished boom which I’d prefer not to get battered by too heavy hardware. Any recommendations?
Thank you
 

olly_love

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I have an old wooden sailing boat,34 feet LOA and about 5.5 tons. We are changing to a loose footed main for the first time. The Bermudan sail has about 400sq feet area and is comparatively low aspect. The outhaul system will be a 6 part purchase.
What size blocks should I use? I’ll use spectra line I think. I don’t want to oversize the blocks as I have a nice shiny varnished boom which I’d prefer not to get battered by too heavy hardware. Any recommendations?
Thank you

Assuming you will be using a winch still and not wating to pull it on by hand In breeze, then I would go with friction rings,
they are better at a static load such as an outhaul and you can add model car tyres to the outside to make them a bit kinder to the boom
 

bbg

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Nope. No winch, just hands and teeth. Am I mad?

Can you lead it back towards the gooseneck so there is just a turning block at the end of the boom and all the blocks hang under the boom closer to the gooseneck?
 

DoubleEnder

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9B61B753-29CC-49D6-B7B4-1EA06BEB46DF.jpeg
My plan is to have a block on the clew. The outhaul will pass round this and then forward along the underside of the boom towards the gooseneck. It will terminate in a loose block with a becket. Another line will pass around this block and around another block with a sheave about 40mm diameter that is fixed on the underside of the boom about 1/3 of the length from the gooseneck. I will work the outhaul from here; no lines are led back to the cockpit at all.
The fixed block was was originally used to tension reefing lines, but in practice I can pull in the reefs by hand if we take some pressure out of the sail. We don’t in general reef while charging along at full speed, I’m happy to slow down for a couple of minutes.

I’d like to be able to tweak the outhaul without actually having to ease the sheet. So a more meaningful purchase would make sense. I think in this system outlined above I have a 3x and a 2x purchase so making a 6:1 ratio. I’ll use something like 6mm spectra and the block at the clew and the block below the boom will be new. I’m sort of hoping for something small and light like those Harken T2 type of thing. Most of my other blocks are ash! So this is all a bit new for me.
I don’t have anything like a modern racing boat so may be in the wrong forum,but I figured you guys would know how to size and spec this sort of thing better than my usual crowd of varnish sniffers in the classic boat forum.
 

michael_w

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Just tie it off. You'll lose more speed faffing about with the outhaul than you'll ever gain by adjusting it during the race.
 

TLouth7

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It seems to me that the maximum tension you can possibly apply to the "hauling rope" is your bodyweight but this would be magnified by sweating the rope (how strong is the cleat?). So let's say Tension = 3kN max (80 kg * 10 N/kg / sin(15 degrees)). The 3:1 blocks need to be rated for that.

Tension in the main rope is 3x this so 9kN max. The blocks at boom end and clew need to be rated for that.

Obviously if you haven't got enough purchase to adjust outhaul in all wind strengths then it follows that tensions in all the elements will be higher than this.
 

lw395

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Our 40ft boat had the outhaul on a 12:1 tackle, no winch needed.
Whatever tackle you have, the clew slide will have to be pretty special to move with sheet hard in and the kicker on. If you are going to drag it out against the friction from the luff tension, you will need to seriously uprate the blocks and lines.
 

bbg

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My plan is to have a block on the clew. The outhaul will pass round this and then forward along the underside of the boom towards the gooseneck. It will terminate in a loose block with a becket. Another line will pass around this block and around another block with a sheave about 40mm diameter that is fixed on the underside of the boom about 1/3 of the length from the gooseneck. I will work the outhaul from here; no lines are led back to the cockpit at all.
The fixed block was was originally used to tension reefing lines, but in practice I can pull in the reefs by hand if we take some pressure out of the sail. We don’t in general reef while charging along at full speed, I’m happy to slow down for a couple of minutes.

I’d like to be able to tweak the outhaul without actually having to ease the sheet. So a more meaningful purchase would make sense. I think in this system outlined above I have a 3x and a 2x purchase so making a 6:1 ratio. I’ll use something like 6mm spectra and the block at the clew and the block below the boom will be new. I’m sort of hoping for something small and light like those Harken T2 type of thing. Most of my other blocks are ash! So this is all a bit new for me.
I don’t have anything like a modern racing boat so may be in the wrong forum,but I figured you guys would know how to size and spec this sort of thing better than my usual crowd of varnish sniffers in the classic boat forum.

Presumably you mean the outhaul will be made off at the end of the boom, through the block on the clew, then back AFT to the end of the boom before returning forward along the boom? That already gives you 2:1 so any tackle arrangement after that will be double its normal strength.
 

DoubleEnder

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Our 40ft boat had the outhaul on a 12:1 tackle, no winch needed.
Whatever tackle you have, the clew slide will have to be pretty special to move with sheet hard in and the kicker on. If you are going to drag it out against the friction from the luff tension, you will need to seriously uprate the blocks and lines.
Yes I see what you mean. I guess I’ll set it up with what looks about right and give it a go. I don’t really have the option of using a winch. There are halyard winches on the mast I suppose, but it would be a horrid lead and I’m not going to fit any new equipment on the deck.
 

flaming

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Yes I see what you mean. I guess I’ll set it up with what looks about right and give it a go. I don’t really have the option of using a winch. There are halyard winches on the mast I suppose, but it would be a horrid lead and I’m not going to fit any new equipment on the deck.

You shouldn't need a winch. If it turns out that whatever you fit isn't man enough to get the outhaul on hard when the sail is fully powered up (and few are without a winch) then you either need a quick sheet ease, bang the outhaul on and sheet on again, or just remember to do it before you get to the bottom mark....
 

DoubleEnder

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You shouldn't need a winch. If it turns out that whatever you fit isn't man enough to get the outhaul on hard when the sail is fully powered up (and few are without a winch) then you either need a quick sheet ease, bang the outhaul on and sheet on again, or just remember to do it before you get to the bottom mark....

Yup that is basically my approach to all trimming, including headsail sheets. I do have little winches there but often it is actually quicker to luff for a few seconds rather than try to grind. Old boat, old winches, old crew, and not much point in going nuts
 

Kukri

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Graham races his Fife... Perhaps the Bentley Drivers Club or the Bugatti Owners Club may have some ideas about staying in period and true to design whilst going a little faster. Carbon fibre inside the hollow silver spruce mast is not recommended, though...;)
 
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