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ppvdw
04-21-2013, 09:48 AM
Dear,

I am in the process of restoring a Norwegian build BB17 from 1962 and am looking for ideas to improve the mainsheet system. Currently the system consists of two single sheave blocks on deck and a double sheave at the end of the boom. The two single blocks are fixed to the rear deck. All blocks are made by HYE. As you can see on the attached drawing, one of the single blocks comes with a cleat and a becket. Sail area is 11.7 square meter and loa 7.30 meter.


I'd like to upgrade to blocks with some kind of bearings (preferably in wood) and would also like to improve the purchase. However I do not want to move the sheet to the cabin floor and the middle of the boom.


file:///Users/ekppvdw/Library/Containers/com.evernote.Evernote/Data/Library/Application%20Support/Evernote/accounts/Evernote/ppvdw/content/p715/8c6d63579fa10a985e44992a53346904.jpeg



Would appreciate ideas and suggestions.


Thanks

keyhavenpotterer
04-21-2013, 10:44 AM
I'd reccomend Harken Classic 57mm blocks. The black and silver is very classic, they work very well with minimum maintainance and last a lifetime. The lower friction may mean you don't need extra purchase. Carbo blocks are good but tend to look a little too modern on some traditional boats.

Two seperate boom blocks may help spread loads over a wider area than a single point double block, which may help shock loads on your boom and its fittings.

To help you in higher wind the ratchet blocks take load off. They do switchable classic blocks with or without cleat, or 57mm carbo ratchmatics which come on automatically with load. The stand up springs or balls, keep it vertical.

With these blocks, and a low stretch dyneema mainsheet with a grippy outer, I'd reccommen Maffioli Swiftchord, in grey with a white fleck: it looks classic and matches the blocks. You might not always want low stretch if you want to keep possible gybe shock loads lower depending on the state of your boat, but generally its a good thing.

You can increase purchase with more blocks, but there is more rope moving which can get under your feet and gives slower times to quickly sheet in or out. You need to know what size mainsheet diameter you find comfortable to hold, as well as making sure its strong enough and making sure it matches your block size.

Harken do fast and slow combined mainsheet systems but that's more than you probably want unless racing.

You can put the rear blocks on a track if you want to set leach tension then play the traveller instead, a better system that allows you to set the blocks to windward, and reduce mainsheet tension in light air to prevent excessive leach tension, or set blocks to leeward in heavy air. Might be more complex than suits you or the boat, again depends if your racing.

Some people like the rear blocks held by a bridle that spans the rear deck. This lowers rope needed, and may combine this with a very powerful kicker to control sail leech tension, and use the mainsheet to pull the sail in and out with respect to the wind. Again sometime people make effort to get the deck blocks high on a pedestal close to boom level so the sail is just pulled in and out and not down as well, leaving that to the kicker.

Use harken dry lube on the blocks.

The very nice herreshoff pattern bronze blocks are available, look very nice and have ball races I gather and may be worth a good look if you want a really 'polished look'.

You can buy the harken sheaves seperately if you want to put them inside wooden blocks of your own making.

Ed

Jonathan Burke
04-21-2013, 01:36 PM
Looks like you have a 4 to one ratio there, similar to (but with a different anchor for the non working end) the '4:1 swivel base' on the document bellow. I have found this quite useful for working out what blocks to put where on main-sheet arrangements, although some of them are a little to 'plastic boat' for my tastes. http://www.jamestowndistributors.com/userportal/document.do?docId=199

You could try an adaptation of one of the 6:1 arrangements, Mr 'potterer is right about the increased amount of rope knocking around in the cockpit tho.

If you want to reduce friction, you have 2 options; 1 is to use more modern blocks which have fancy bearings and run silky smooth, but that may not fit in with the look of your boat, the other option is to increase the size of the blocks and keep the rope diameter the same, I oversize the main-sheet blocks on boats I'm building or repairing, and I find that the HYE blocks run much better this way, they also last an age and look the part without having to take out a mortgage for wooden blocks (which also hurt more than their modern equivalents, when they swing and hit you in the head).

I am interested to see if someone has made some wooden blocks using modern ball bearing sheaves, they would be quite cool.

Hwyl
04-21-2013, 02:00 PM
What Keyhsavenpotterer said, except I'll translate "kicker" to "vang" for the non Brits and add a link to Jim Reineck's blocks http://www.bronzeblocks.com/

JimConlin
04-21-2013, 02:08 PM
If you're compelled to classic style, Jim Reineck at http://bronzeblocks.com/ can supply blocks patterned after the Herreshoff Mfg. Co. blocks, but with modern bearings.
http://bronzeblocks.com/images/boomblock.jpg

The rig you've sketched (called a 'Crosby rig' in some quarters) offers a mechanical advantage of something less than 4:1, less friction losses. It offers no control over sail twist, i.e., you don't get to pick whether the sheet system pulls the boom down or inward.
If you'd like that control and higher mechanical advantage on the sheet, and there isn't a conflict with a tiller in the region between the two deck blocks, you might consider a traveler system. These systems get complex (and expensive), so they need pretty careful planning. Study the catalogs of the manufacturers like Harken and prowl the docks.

ppvdw
04-21-2013, 03:21 PM
All

Thanks very much for the great suggestions. Originally I was thinking of wooden blocks but you have given me something to think about. Increasing the number of blocks and thus the sheet length is not particularly appealing. Solving the issue with modern blocks, including a ratchet block, seems to make more sense. The Reineck blocks are definitely a contender! They look stunning. In that case I will need to replace, over time, all the other blocks on board as well. The advantage of that solution is that it would also solve another reoccuring problem: what to ask for Christmas.
The traveller idea makes sense but would need to be fitted on some kind of bridge as the tiller is in the way. I could see an elegant bronze saddle (if that is the correct English term).

Thanks again

Jonathan Burke
04-21-2013, 04:07 PM
I think 'sheet horse' is the correct term (although there are many names, I'm sure), although these are normally just a bar that is raised of the aft deck, you may be able to get someone to cast you something that would take a track and traveler system. I imagine it would need to be pretty beefy.

ppvdw
04-21-2013, 04:13 PM
Thanks Jonathan. You are right. It is called a sheet horse. I just found a company in the UK called Classic Marine who can cast them. www.classicmarine.co.uk. These do not have a track but at least allow for a simpler sheet configuration and make it possible to control the twist of the sail a bit better.
Peter Paul

Roger Cumming
04-21-2013, 07:47 PM
A simple sheet horse can be made from bronze rod, 3/8" or 7/16" in diameter, bent and fastened to the proper length for the deck. I don't know why anyone would go to the trouble to cast something as simple as this.

ppvdw
04-22-2013, 01:09 AM
Roger, that is definitely an alternative that I will consider. Until last night I had simply not given the horse a thought.

keyhavenpotterer
04-22-2013, 04:42 AM
Better running rigging does make a noticeable difference to how easy it is to adjust the rig. This can make it more pleasant to use and the boat faster as its more responsive.

I don't know what boat or rig you have but besides adjusting the mainsheet, you can also look at having a more adjustable outhaul to flatten the sail camber to reduce power and also use the kicker instead to open the leech or use a backstay if you have one on a fractional rig. You can also run flatter sails for higher winds and point higher also.

Harken is the best, but other companies like Ronstan and Lewmar have there own similar blocks that probably work as well. There is a difference to how these top end blocks work at the start and again after a year or two. Cheap blocks will work poorly and be hard to use after a year or two. Its definately worth doing it properly if you go this route and spend the money. You can pick up Harken stuff in the sale or on ebay, but they are the market leaders, perhpas like Lewmar is with winches.

The Harken catalogue used to include calculations regarding breaking strength needed, depending on displacement sail area and rig etc, but they have standard block sizes they recommend if you just ring them.

Only down side, is the cost of good blocks and line, it can make me uneasy about leaving it on the boat, as its easily stolen. Can't live in fear, but its easy for opportunist petty theft. Unhooking it and taking it home, adds some rigging time. Though you can take it with you onto the next boat, and put the less good stuff back on.

To reduce cost, some people use smaller blocks that are still load rated enough. This limits line diameter to a smaller size, so you can run a thinner cheaper uncovered strong dyneema line through most of the blocks then leave it covered or splice it to thicker covered comfortable line where you hold it. Uncovered dyneema is not so dear and will run through the smaller blocks with ease. The ultra special mainsheet outer coverings also are designed to resist it tangling up.

If you make rope stropped wooden blocks, it will cost very little. You can make a sheave, but buying a bearing sheave will improve performance no end. If you want wooden blocks, if I remember there is a very good account of making them and preserving them by Pete Culler in 'Pete Culler on Woodenboats'. Book is very good, with a good section on oars too and I think there was an article in Woodenboat magazine not so long ago on making metal strapped wooden blocks.

ppvdw
04-22-2013, 05:18 AM
Thanks Keyhavenpotterer - I have a fractionally Bermudan-rigged sloop. Sail Area: Main- 11.7 m2 and the Genua - 12.5 m2.
Apart from backstays we have the other trim options but all can do with some optimizing. Sofar we have focused on making the hull sound again. You are right on the need to select good quality blocks. The good news of living in Switzerland is that I am a bit less concerned about folks nicking lines and blocks. I'll have a look at the book you mention but am not sure that making them myself is the right option for us.

allene222
04-22-2013, 09:46 AM
If you are not concerned with the weight of the blocks and go away from the wood idea you might consider Garhauer. They are solid and will last forever at about 1/2 the price of the lighter plastic versions from the high end companies. I use the stainless steel versions as I like that look but they also have aluminum ones. If you don't want to get a new mainsheet you are stuck with 4:1 unless you don't mind limiting how far the boom can go out. We found that having an auto hex-ratchet was a great addition allowing us to still control the mainsheet with high loads. That takes some of the desire for more purchase away. We like a fixed cam cleat, no swivel, after trying several different arrangements.

Ian McColgin
04-22-2013, 10:03 AM
I like double ended sheet systems as a great way to get away from travelers, which tend to jam especially in a gybe.

A double ended sheet for the rig as drawn would require a double block at each corner of the stern and a triple (or three seperate, or a double and a single) on the boom. So the line goes through one, to the boom, back to the other on that side, to the boom, through a block on the other side, to the boom, and back out the other double.

To save on investment, since you've already got one double and two singles, I'd just buy another double and another single, put the doubles down on deck and rig the three singles on the boom maybe in line about 6" apart from each other.

The double ended rig requires that you have reasonable line management habits and that you keep one eye out for "walk" - the tendency for one side to get all the way out. The nice thing about it is that you can short tack without fiddling but on longer bits if you really want good control you can more pull the boom in with the weather side or down with the lee side.

If you're racing and have the crew, put a person on each end so that when you gybe you can get the sail in double quick.

The now ubiquitous ball bearing blocks were pioneered for iceboats with their very high tech high loading. The have some slight utility in some racing classes. In regular boats a little inefficiency in ease of trimming is actually not noticable while for easing, especially in a gybe, friction is your friend. So get some nice blocks that fit the style of your boat but look to durability and safe working load and try not to worry about roller bearings versus ball bearings maybe in two chases versus just an axel.

G'luck

ppvdw
04-23-2013, 01:36 AM
Thanks Ian.
That is a very interesting and appealing solution you propose and maybe easier and cheaper to implement than adding a horse. On a boat with a 2.05 meter beam the two blocks on deck are not that far apart anyway. Line management will indeed be a challenge but worth a try for a season. I should have enough used blocks in my basement to set up a trail version before investing in new blocks.

By the way there is a German trading company specialised in traditional boat gear called Toplicht www.toplicht.de. They offer compact reasonably priced blocks from teak or ash with roller bearings and messing sheaves - ca. 60Euros for a two sheave. (as well as the expensive varieties ... ). How would you belay the ends? On a cam cleat or on a simple old fashioned cleat.

Have a great season

ppvdw
04-23-2013, 01:53 AM
Here's the link to the English page with the yacht blocks http://www.toplicht.de/en/shop/schiffsbloecke/yachtblock/klassische-holzbloecke