Moving main sheet position on boom

Discussion on how to make that Trailer Sailer go faster & more comfortable
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Samdowl
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Moving main sheet position on boom

Post by Samdowl » Dec 6th, '20, 08:35

We've recently moved from an Investigator 563 to a Sonata 7 to make room for a new family member. With little kids on board who like to throw hats overboard a bimini is a necessity. On the investigator a standard 2 bow fit perfectly but on this boat we're stuck in between sizes. The coamings are 1700mm apart and most biminis in that width are just too long to fit between the rear arch and main sheet. The main sheet is more or less vertical at the moment and measures 1600mm from the arch to the sheet. I've found a Kaiser marine bimini that is 1650 long. The easiest way to fit it would be to just bump the main sheet mounts forward 70mm. Will this change in angle and position effect sailing characteristics or am I overthinking things? Or should I Just get the Ocean south whitewater, leave things as they are and accept 300mm less shade? The Ocean South one does have thicker tubing so it's not too much of a concession.

Cheers, Sam

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Re: Moving main sheet position on boom

Post by Even Keel » Dec 6th, '20, 09:06

70mm won't adversely affect anything. On rotating rigs you move top blocks a lot more than that in the other direction to force mast rotation.

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Re: Moving main sheet position on boom

Post by MoodyBlue » Dec 6th, '20, 09:07

I put our main sheet 300mm further forwards on our Sonata 26. It does give extra angle when the boom is all the way out so is a good thing to do so 70mm is nothing. Sketch explaining the angles when moving traveller and or boom mounting points.
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Re: Moving main sheet position on boom

Post by impulse » Dec 6th, '20, 13:22

I think that's a bit of an ageist comment. I like throwing hats over board. 8)
Cheers Robin.

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Re: Moving main sheet position on boom

Post by zebedee » Dec 6th, '20, 14:03

I have a second mainsheet hanger further forward to allow use of the bimini. Obviously it increases the mainsheet tension required to achieve the same force x distance from the gooseneck at the boom, so remember to move the mainsheet back to the usual hanger when tacking upwind in heavier weather.
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Re: Moving main sheet position on boom

Post by Samdowl » Dec 7th, '20, 07:53

Oh, I like the idea of just hanging an extra hanger. I'll be able to hang the baby off the extra one in the jolly jumper then. I thought it would be ok, but I'm hesitant to drill more holes in the boat without checking first. Cheers, everyone.

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Re: Moving main sheet position on boom

Post by hoges1234 » Jan 5th, '21, 11:18

MoodyBlue wrote:
Dec 6th, '20, 09:07
I put our main sheet 300mm further forwards on our Sonata 26. It does give extra angle when the boom is all the way out so is a good thing to do so 70mm is nothing. Sketch explaining the angles when moving traveller and or boom mounting points.
Hi, I have recently bought a Sonata 26 and the vertical mainsheet has had me puzzled for a fitting a bimini. How does moving the main sheet forward on the boom affect mainsheet pressure? Harder to pull in? I see some 26's have the traveller across the cockpit entrance. Certainly as a cruiser I am looking for comfort rather than racing speed. Have you been able to fit a bimini that covers the cockpit?
Regards
Mike

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Re: Moving main sheet position on boom

Post by Tezza » Jan 5th, '21, 12:55

Anything is possible with a bit of lateral thinking.
Here is photo of my Sonata 6 back in the eighties by the original owner .
A bit extreme but suited his needs in FNQ
The bimini covered the whole cockpit . What he did was raise the boom on the mast by 10 - 15 cms. Build a ss bracket which he mounted on the transom using the backstay holes and running the backstay to the top of the fixture. This ss bracket also had a U welded to the top for the mast to rest in. This allowed a totally clear cockpit in the shade . I took it all off but sometimes wonder when sitting the the hot sun

And the day I picked it up.
C661D624-2654-496E-8188-E83031AB6353.jpeg
C661D624-2654-496E-8188-E83031AB6353.jpeg (20.88 KiB) Viewed 211 times
E4417E64-51E9-411D-B76A-B3E14711621D.jpeg
Sonata 6 Mango

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Re: Moving main sheet position on boom

Post by MoodyBlue » Jan 5th, '21, 13:24

hoges1234 wrote:
Jan 5th, '21, 11:18
MoodyBlue wrote:
Dec 6th, '20, 09:07
I put our main sheet 300mm further forwards on our Sonata 26. It does give extra angle when the boom is all the way out so is a good thing to do so 70mm is nothing. Sketch explaining the angles when moving traveller and or boom mounting points.
Hi, I have recently bought a Sonata 26 and the vertical mainsheet has had me puzzled for a fitting a bimini. How does moving the main sheet forward on the boom affect mainsheet pressure? Harder to pull in? I see some 26's have the traveller across the cockpit entrance. Certainly as a cruiser I am looking for comfort rather than racing speed. Have you been able to fit a bimini that covers the cockpit?
Regards
Mike
Not really, my first try was very greedy trying to fit a four bar bimini but is was a total hash up so is resigned to the shed. More recently I had a crack at a three bow bimini and it is getting close, i just need to sew the sides they they are taut. Photo shows current progress in trying to allow the bimini to be up while sailing. It may turn out to be a case of bimini only when parked up? I attempted to shorten the front bow enough to clear the boom but that upsets the bimini cover geometry.
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Re: Moving main sheet position on boom

Post by bachus » Jan 5th, '21, 13:44

Jeff,

If you remove the rivet / screw on the slide for the middle loop and slide the middle bar downwards, this lowers the middle of the cover giving more cover slack to allow the front bar to fall forward more. This almost allows the Castle boom to clear but not quite . . . so when sailing I loosen the front tension straps allowing the front bar to fall back just a bit - this gives the clearance required to sail - looks terrible but I still have sun cover. When no sailing - re-tension the front straps.
Jim
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Re: Moving main sheet position on boom

Post by Furstin » Jan 5th, '21, 14:31

Does your main have a small flattening reef? I just set the main to that at rear to give about 4inch or so lift to clear bimini. I never tried a bimini on the s26 just boom tent, but the boom was reasonably high.
Re:moving traveller. A must do imo as it's just such a pain across cockpit. It still has enough purchase for good leech tension.


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Re: Moving main sheet position on boom

Post by Peridot » Jan 5th, '21, 18:10

Our Young 6m had a traveller across the centre of the cockpit, first thing I removed. I have a U bolt in the cockpit floor. The centreboard comes up hard under the cockpit floor so I could not set it down in a well, compromised by protecting toes with a piece of soft rubber. Works well. The whole main sheet is removed when the boom is in a crutch. The Bunnies rope is a sop to my old age and soft hands, it lasts quite well if you keep it out of the sun when not in use. Not many of us race seriously these days so a traveller is a bit of a nuisance. An efficient kicker is much more important.
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Re: Moving main sheet position on boom

Post by roverfj1200 » Jan 5th, '21, 22:06

Northwind 7 New to this wind powered stuff

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Re: Moving main sheet position on boom

Post by Furstin » Jan 7th, '21, 00:07

Regarding removing the traveller. I could not disagree more, in gusty conditions having libs play the traveller is key, not just perf but her control, in 15knts she can keep us at 20 deg -there's no way a vang and playing main can do that, and if so, much work.


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Re: Moving main sheet position on boom

Post by MoodyBlue » Jan 7th, '21, 07:54

Furstin wrote:
Jan 7th, '21, 00:07
Regarding removing the traveller. I could not disagree more, in gusty conditions having libs play the traveller is key, not just perf but her control, in 15knts she can keep us at 20 deg -there's no way a vang and playing main can do that, and if so, much work.


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EXACTLY Matt, That was what I was pointing out in the boom angle diagram I re-posted on Dec 6th.

There may be a little more pressure on the mainsheet, but have the ability to pull directly down on the boom over a much wider angle gives much better control over the sail shape and power.
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Re: Moving main sheet position on boom

Post by impulse » Jan 7th, '21, 07:57

I reckon those snap shackles in a mainsheet system would break under any serious load.
Cheers Robin.

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Re: Moving main sheet position on boom

Post by rseydler » Jan 7th, '21, 09:37

impulse wrote:
Jan 7th, '21, 07:57
I reckon those snap shackles in a mainsheet system would break under any serious load.
all of the local OTB catamarans use them. I couldn't find the triple block that the cats use but here is a single https://www.garhauermarine.com/single-b ... 5-uag.html with a SWL of 1500kgs

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Re: Moving main sheet position on boom

Post by Peridot » Jan 7th, '21, 21:24

I don't use snap shackles, they cost too much and can open at the wrong time. (They have a MWL of 750 Kg plus). The photo shows snap hooks. The top one is Ronstan and was on there when I got the boat 10 years ago. The swivel is wearing. The bottom one is a stainless snap hook priced at $4.99, I use the same on my halyards, no worries.
My main is 15.1 sq.m (162 sq ft) and I can tension my main sheet with one hand, say 25 Kg. 4 part purchase means 100Kg. The Bunnies rope will wear out long before the clips.


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Re: Moving main sheet position on boom

Post by zebedee » Jan 8th, '21, 01:21

Peridot wrote:
Jan 7th, '21, 21:24
I don't use snap shackles, they cost too much and can open at the wrong time. (They have a MWL of 750 Kg plus).
Ronstan make a range of snap shackles with Maximum Working Loads from just 75kg (RF6080) up to 2000kg (RF6300).

Image

The key feature of a snap shackle is the ability to release quickly, including under load, when the sliding pin is pulled. If you don't need this feature then they are not the right device, not least because they are expensive. If unexpected release is a threat, remove the split ring and use a small lanyard in a loop and pass the loop through the shackle, so that if it snags on something, it is less likely to release.

Ronstan also do a single design of snap hook, RF533, rated to 360kg MWL. I have one on my mainsheet which at some time before I bought the boat has been overloaded and very slightly distorted. I suppose that means that 360kg MWL is *almost* adequate.

Image

There's a wide variety of stainless steel cast snap hooks and formed rod snap hooks available from places like Bunnings, various industrial suppliers, and yes, Whitworths:
Image

Image

- but very few suppliers offer any sort of load rating for these products. At least they are cheap.

Sam Allen have load ratings for their 3 sizes of cast snap hooks, from 50mm long to 100mm long. Wait for it... 55kg for the 50mm variant; 225kg for the 100mm version.

Because snap hooks are not closed load bearing loops, but simply a "hook" (even the caribiner style) they are are nowhere near as strong as similar sized shackles, snapshackles, or quicklinks.
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