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Old 26-09-2019, 02:37   #1
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Placing reefing blocks.

Hi all,

I need to move the reefing blocks on the boom as my new(ish) main has different reefing ratios to the old sail. (The new main has much more aggressive reefing, as per the advice of my favourite sailmaker. )

Is there some kind of formula to allow me to calculate to correct position for the blocks?

I kinda feel it should be in a ratio equivalent to the reefing ratios.

Matt
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Old 18-11-2019, 22:00   #2
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Re: Placing reefing blocks.

My experience of the staysail is it is only effective upwind. So I would consider focusing on close sheeted positions. Looking at converting my decksweeper to a furler.

Neil
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Old 19-11-2019, 06:20   #3
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Re: Placing reefing blocks.

Block directly under clew.

Raise sail, eyeball it. Mark new location, install.

You'll love it!

Ann
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Old 19-11-2019, 13:00   #4
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Re: Placing reefing blocks.

Quote:
Originally Posted by JPA Cate View Post
Block directly under clew.

Raise sail, eyeball it. Mark new location, install.

You'll love it!

Ann


I feared it would be something like that.
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Old 19-11-2019, 13:07   #5
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Re: Placing reefing blocks.

Block 45 degrees behind clew cringle when it's down on the boom.
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Old 19-11-2019, 14:11   #6
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Re: Placing reefing blocks.

Quote:
Originally Posted by Cheechako View Post
Block 45 degrees behind clew cringle when it's down on the boom.

+1 w/a slight angle back so you can tighten the foot better. Rather than installing the reefing block directly to the boom could add a small section of track for the blocks. With the blocks on the track you can move the location of the blocks for the "best" position.
Something else you may want to look at are Antal reef blocks added to the leech of the main. We added these to our main and it significantly reduced friction, making reefing quicker/easier.


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Old 19-11-2019, 16:50   #7
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Re: Placing reefing blocks.

Quote:
Originally Posted by Cheechako View Post
Block 45 degrees behind clew cringle when it's down on the boom.
Quote:
Originally Posted by Bill O View Post
+1 w/a slight angle back so you can tighten the foot better. Rather than installing the reefing block directly to the boom could add a small section of track for the blocks. With the blocks on the track you can move the location of the blocks for the "best" position.
Something else you may want to look at are Antal reef blocks added to the leech of the main. We added these to our main and it significantly reduced friction, making reefing quicker/easier.


Bill O.
+1, this has been my approach in the past but I never considered there might be a formula to get it better!
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Old 19-11-2019, 18:19   #8
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Re: Placing reefing blocks.

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+1, this has been my approach in the past but I never considered there might be a formula to get it better!

Side effect of being a mathematician. I am always looking for a formula.
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Old 19-11-2019, 18:32   #9
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Re: Placing reefing blocks.

If your main is loose footed, put the reefing blocks in the END OF THE BOOM.

Run the reefing line through the block, up to the reefing cringle, then down to the boom with a loose loop around the boom.

The reefing line will self adjust by sliding out the boom as the reef is cranked in.

In the end it will apply proper tension (as if an outhaul) and also pull the clew down to the boom.

No measurements needed.
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Old 19-11-2019, 18:43   #10
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Re: Placing reefing blocks.

Quote:
Originally Posted by wingssail View Post
If your main is loose footed, put the reefing blocks in the END OF THE BOOM.

Run the reefing line through the block, up to the reefing cringle, then down to the boom with a loose loop around the boom.

The reefing line will self adjust by sliding out the boom as the reef is cranked in.

In the end it will apply proper tension (as if an outhaul) and also pull the clew down to the boom.

No measurements needed.


Darn, thatís a very interesting solution but my boom bag makes it impossible. But I can see how it could work very well.
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Old 20-11-2019, 05:46   #11
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Re: Placing reefing blocks.

Quote:
Originally Posted by wingssail View Post
If your main is loose footed, put the reefing blocks in the END OF THE BOOM.

Run the reefing line through the block, up to the reefing cringle, then down to the boom with a loose loop around the boom.

The reefing line will self adjust by sliding out the boom as the reef is cranked in.

In the end it will apply proper tension (as if an outhaul) and also pull the clew down to the boom.

No measurements needed.

... and this is where the addition of Antal reef blocks makes the whole system work better due to less friction. My sail maker had never put them in until I requested them, now he highly recommends them for all new mains.


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Old 20-11-2019, 10:08   #12
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Re: Placing reefing blocks.

Quote:
Originally Posted by wingssail View Post
If your main is loose footed, put the reefing blocks in the END OF THE BOOM.

Run the reefing line through the block, up to the reefing cringle, then down to the boom with a loose loop around the boom.

The reefing line will self adjust by sliding out the boom as the reef is cranked in.

In the end it will apply proper tension (as if an outhaul) and also pull the clew down to the boom.

No measurements needed.

That's how Dragonfly does it.
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Old 20-11-2019, 13:35   #13
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Re: Placing reefing blocks.

Quote:
Originally Posted by wingssail View Post
If your main is loose footed, put the reefing blocks in the END OF THE BOOM.



Run the reefing line through the block, up to the reefing cringle, then down to the boom with a loose loop around the boom.



The reefing line will self adjust by sliding out the boom as the reef is cranked in.



In the end it will apply proper tension (as if an outhaul) and also pull the clew down to the boom.



No measurements needed.

+1

Thatís how it is with our main and three reefs. The stack pack bag has reinforced cut outs to allow the line around the boom to go vertically up to the clew block (first and second reefs) or LFR (third reef).

The line around the boom provides the downward force and the sheave at the end of the boom (could be external cheek block) provides the outhaul force. And you have 2:1 and reduce the force on the reefing line.
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Old 21-11-2019, 01:52   #14
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Re: Placing reefing blocks.

Quote:
Originally Posted by fxykty View Post
+1

Thatís how it is with our main and three reefs. The stack pack bag has reinforced cut outs to allow the line around the boom to go vertically up to the clew block (first and second reefs) or LFR (third reef).

The line around the boom provides the downward force and the sheave at the end of the boom (could be external cheek block) provides the outhaul force. And you have 2:1 and reduce the force on the reefing line.


Thanks for this. Youíve made me realise it may still be possible to do this on my boat. Ironically, the reason for my original question stemmed from my concern about cutting the slots in the boom bag for the reefing.
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Old 21-11-2019, 11:30   #15
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Re: Placing reefing blocks.

Quote:
Originally Posted by GILow View Post
Thanks for this. Youíve made me realise it may still be possible to do this on my boat. Ironically, the reason for my original question stemmed from my concern about cutting the slots in the boom bag for the reefing.

Is your boom bag attached to your boom via bolt rope? If so, cutting and patching is your only choice. But if itís attached with slides, just slot the reefing line between slides vertically below the clew itís for.

Note, put a bowline (or splice an eye) in the end of the reefing line. Arrange the eye at the top edge of the boom on the side you want the reefing line to go up to the clew (typically the opposite side to where youíve got the sheave or turning block). Then lead the reefing line around the boom, through the eye, then up to the clew.
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