Internal Mainsheet - how good are they?

Moderators: Shu, rand

Post Reply
EdS
Posts: 188
Joined: Mon Aug 06, 2012 12:06 pm
Boat Number: GBR 1524

Internal Mainsheet - how good are they?

Post by EdS » Mon Apr 29, 2013 12:07 pm

I realise it all depends on the set up, but assuming you get a smooth system working .


Pro's i can see
using the ratchet in reverse (good for light winds and leech tension)
and having a self adjusting rear triangle (especially with a raking rig) is appealing,

Cons
but are internal mainsheets smooth to operate
reliability given the increase complexity?

Just interested in opinions, I have the relevant sheaves and a plan for fitting them, but wanted to see what the consensus is.
Roaring Forties GBR1524

joe.bersch
Posts: 127
Joined: Wed Jul 16, 2008 2:47 am

Re: Internal Mainsheet - how good are they?

Post by joe.bersch » Mon Apr 29, 2013 2:25 pm

Ed:

I am a big fan. If you change your rake frequently they are a real asset. Properly rigged they are very smooth simple and reliable. Do it. You won't be sorry in my opinion.

Joe

EdS
Posts: 188
Joined: Mon Aug 06, 2012 12:06 pm
Boat Number: GBR 1524

Re: Internal Mainsheet - how good are they?

Post by EdS » Mon Apr 29, 2013 2:35 pm

Thanks Joe,

Do you support the block running inside or just it just hang down when not under tension?
have you gone 2:1 or 3:1

I have the holes in the boom, just need to make up the sheave mounts to fit.
Any idea what length the 1:1 lines need to be?
Roaring Forties GBR1524

User avatar
Shu
Posts: 814
Joined: Sat Sep 23, 2006 4:46 am
Boat Number: USA 1183
Location: San Diego (sort of)

Re: Internal Mainsheet - how good are they?

Post by Shu » Mon Apr 29, 2013 9:30 pm

Ed,
I used to have the internal system. It was very smooth and reliable. It had a 2:1 internal purchase, which coupled with the angle of traingle equated to about 1.4:1 when trying to get leach tension in light air. I would recommend a 3:1 internal purchase for this system, which should give about 2.1:1 true purchase.

When you sailed with me I had gone to a true 1:1 connection to a fixed bridle, coupled with the 2:1 internal purchase. This gave a true 2:1 purchase, but as you pointed out, gave up some ability to completely center the boom.

I have since gone with a 49'er style split mainsheet, which has an external 2:1 after the split with no internal purchase. This gives about 2.7:1, and works very well. The downsides are: the bridle, coupled with the split gives twice as many lines to swim through in a capsize, and I seem to rotate the jib cleat one way, which eventually twists the split sheets around each other.

As for length of the 1:1 lines: Try to use as much of the length of the boom as possible. If you don't have an internal web in your boom, you are ahead of the game. This is sort of a trial and error exercise; you want to them short enough to be able to crank on the leach tension when raked back (not super critical unless you get caught in 6 kts with full rake), and you want to be able to ease the boom out a few inches from the shrouds. A good starting point is to have them the length from the exit at the forward end of the boom to the entrance block, plus the distance from the entrance block to the boom block, and then the distance from the boom block to the dead end at the gunwale plus a little for splices or knots. You can trim them from there once you have the rig up and hoist the main. I hope this makes sense.
Steve Shumaker
USA 1183

EdS
Posts: 188
Joined: Mon Aug 06, 2012 12:06 pm
Boat Number: GBR 1524

Re: Internal Mainsheet - how good are they?

Post by EdS » Wed May 01, 2013 12:06 pm

Thanks Steve,

You have added another option. What does the 49er set up offer over a traditional 3:1 with a fixed bridle?

I am tempted by an internal mainsheet with a 3:1

The only issue i have is that my boom has holes drilled for through deck blocks out towards the clew but they are not parallel to the boom but down at around 30 degrees, which is probably why it isnt there anymore.
If i enlarge this hole so the same fitting can be mounted horizontally is this going to be a major problem for the boom strenght?
I guess photos will help.

The other question is what size are the blocks coming out of the boom normally?
Roaring Forties GBR1524

User avatar
Shu
Posts: 814
Joined: Sat Sep 23, 2006 4:46 am
Boat Number: USA 1183
Location: San Diego (sort of)

Re: Internal Mainsheet - how good are they?

Post by Shu » Wed May 01, 2013 4:56 pm

Ed,
I think the 49er setup allows you to go completely external to the boom, or at least eliminates any purchase systems inside the boom. I never had any problem with the internal purchase though.

Whenever I'm cutting into a carbon tube, I first add at least two layers of 200 gm cloth in the general vicinity. One at 0-90, the other at 45-45. More if it's a highly loaded area, like the gooseneck area of the mast, or the vang attachment area of the boom. Make sure any corners of the hole are smoothly rounded!
If it's already reinforced in the area, you should be fine.
Steve Shumaker
USA 1183

Post Reply

Who is online

Users browsing this forum: No registered users and 1 guest