Wet Spreaders

Dynema/Spectra climbing runners as strops

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The stainless bolts for my boom bails have worn slots in the alloy section of the boom and the whole setup looks a bit crappy. I was mulling on the idea of moving the mainsheet setup to use spectra strops rather than metal bolts and bails. Sexy too - almost like a real racing boat.

The usual plan is to have a rigger or sailmaker sew up custom spectra webbing - which is either expensive if they charge what their time is really worth, or expensive if you end up owing them a favor and buying more sails/rigging. I noticed spectra/dyneema climbing runners - basically webbing loops of various sizes - on the net from $10 to $20, which is pretty much free when compared to the usual boaty costs.

What do you all think - 22KN of climbing webbing OK for a J105 mainsheet strop? Lots of colors to choose from too. 

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Reasonable idea. Plenty strong. You'll need a way of keeping the strop from sliding along the boom. Might help to make two turns around the boom (one full turn tight on the boom) and attach the sheet block to the two loops. And keep it short so the block does not become a weapon...which means that the climbing strop may not be a good length.

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You can also make soft shackles that go around the boom, they are easier to remove if you need to adjust things and you can get the size exactly right.

A friend made a new boom for his boat and used this method for attaching most hardware.  He bolted padeyes to the boom to keep the soft shackles in place.

Those strops are useful sometimes, I've used them in a few places.  They are cheaper and easier than making a dyneema loop.

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One other thing to worry about is the geometry of the setup. The standard boom comes with standard bales that hinge forward from the center of the boom. A spectra strop will hinge forward from the top of the boom. This likely means thinking through carefully where the hold-fasts would be to stop the strop from wandering up and down the boom.

Which brings up an opportunity. I recall that my Dad's Fireball had the center sheeting moved quite far forward in the boat compared to the boom connectors (1970's vintage setup). His idea was that on a beat in heavy air, sheeting the main would drive the boom forward into the gooseneck to help bend the mast down low. A J105 is not a light dinghy, but mast shape matters. I wonder whether the same is already built into the current setup or, if not, whether moving the mounting points for the strops back along the boom would help to create this effect. Or maybe the J105's setup is too stiff to care.

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Yes they'll be fine for that size of boat. But do change them out every few years. Don't rig them in a "choker" configuration like this - it's the weakest configuration. Instead use the basket and have both ends of the sling pass through the shackle of the mainsheet block(s)

like this

 

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Climbing slings are ~2200kg in straight pull. Double that for basket. 4.5T break, 2.25T SWL, I would match the strengths on whichever blocks you've been using for your mainsheet.

 

Biggest issues to be aware of are UV and chafe. When a built "custom" loup encounters chafe, it shows on the cover and maintains full strength (also takes the UV damage) until it starts chafing into the core material. Slings will begin to degrade immediate with chafe. But they're cheap so it's easy to purchase spares immediately once you've found a configuration that works.

 

HW

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22 minutes ago, fucket said:

That can't be class legal, right?

The cam cleat or the strop?

The class does not permit changes in purchase (mechanical advantage), but does not seem to care too much about changes to the boat designed to improve mantainability, reduce maintenance costs, extend the lifetime of equipment or organize sheets and lines;  provided that there's no obvious performance advantage from the change.  Over the years inventions for barberhauling and driver-free backstay adjustment have been banned. But tiller conversions, mast doublers at the kite sheave exit, removal of windward-sheeting traveler cars and so-on have been approved. Overall I think that the class drives a very fair and wise balance between gear-nazi conservatism and anarchy - I like the approach. It requires exercise of judgment, but the class is run by grown-ups and there does not seem to be much controversy. My guess is that the strop would be judged to be legal because it helps with a maintenance problem (erosion of the boom)  and does not affect mainsheet purchase. My guess is that the cam cleats would be legal if the purpose is for cleaning up kite tails - whether or not that's actually necessary or the specific place for the cleats is questionable in the first place.   

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15 hours ago, Haligonian Winterr said:

Climbing slings are ~2200kg in straight pull. Double that for basket. 4.5T break, 2.25T SWL, I would match the strengths on whichever blocks you've been using for your mainsheet.

 

Biggest issues to be aware of are UV and chafe. When a built "custom" loup encounters chafe, it shows on the cover and maintains full strength (also takes the UV damage) until it starts chafing into the core material. Slings will begin to degrade immediate with chafe. But they're cheap so it's easy to purchase spares immediately once you've found a configuration that works.

 

HW

I forget who makes it, but someone does have a covered Dynema sling for climbing. It's useless for trad but is fine for top roping. 

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18 hours ago, ctutmark said:

On a J105

Image may contain: outdoor

I really like the shock cord setup on the spin sheet blocks. I race on a 105 and I have been trying to talk my owners into that for years. When you are using shock cord that causes that block to stand up, you throw out the benefits of those low friction ball bearings and end up chafing the shit out of those side plates.

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1 hour ago, Wet Spreaders said:

The cam cleat or the strop?

The class does not permit changes in purchase (mechanical advantage), but does not seem to care too much about changes to the boat designed to improve mantainability, reduce maintenance costs, extend the lifetime of equipment or organize sheets and lines;  provided that there's no obvious performance advantage from the change.  Over the years inventions for barberhauling and driver-free backstay adjustment have been banned. But tiller conversions, mast doublers at the kite sheave exit, removal of windward-sheeting traveler cars and so-on have been approved. Overall I think that the class drives a very fair and wise balance between gear-nazi conservatism and anarchy - I like the approach. It requires exercise of judgment, but the class is run by grown-ups and there does not seem to be much controversy. My guess is that the strop would be judged to be legal because it helps with a maintenance problem (erosion of the boom)  and does not affect mainsheet purchase. My guess is that the cam cleats would be legal if the purpose is for cleaning up kite tails - whether or not that's actually necessary or the specific place for the cleats is questionable in the first place.   

 

I hadn't looked at measurement rulings in some time, I'll be damned:

 

Quote

RI-16-01
Soft Shackles

Q1:  Is it permissible to use spectra shackles in place of stainless steel shackles?
A1: Yes. Soft shackles may be used anywhere stainless steel shackles are used. This includes not only sheet, halyard, and outhaul attachments, but also “Ti-Lite” and similar blocks designed to be lashed rather than shackled. This rule interpretation supersedes RI-02-15.

Q2: Is it permissible to replace the boom bails with strops?
A2: Yes, the boom bails can also be removed and replaced with strops. Although not required, owners are encourages to have these strops professionally installed due to the high shock loads these strops must handle and the need to ensure they do not slide along the boom.

Q3: Is it permissible to use a strop to attach the mainsheet blocks to the traveler?
A3: Yes. This rule interpretation supersedes RI-02-01. Essentially, a strop could be considered a very long soft shackle. As with boom strops, it is recommended that such a strop be professionally installed to handle the high shock loads it will experience.

 

As far as those cam cleats go, I'm pretty sure some boats came with them so they are probably legal because of that.

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Dyneema slings are totally great - have used them for a long time for many different applications on boats - always carry some extras on whatever boat I sail as they are also great for a quick juryrigging job.  Easily last a couple of seasons and you can see when they start deteriorating.

 

For your application get the widest ones you can find to distribute the load on the boom as much as possible - you can get them in widths up to about 20 mm but they are not as readily available as the more common narrower ones

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51 minutes ago, Christian said:

Dyneema slings are totally great - have used them for a long time for many different applications on boats - always carry some extras on whatever boat I sail as they are also great for a quick juryrigging job.  Easily last a couple of seasons and you can see when they start deteriorating.

 

For your application get the widest ones you can find to distribute the load on the boom as much as possible - you can get them in widths up to about 20 mm but they are not as readily available as the more common narrower ones

Mammut I believe makes the widest dyneema ones. 

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59 minutes ago, Christian said:

Dyneema slings are totally great - have used them for a long time for many different applications on boats - always carry some extras on whatever boat I sail as they are also great for a quick juryrigging job.  Easily last a couple of seasons and you can see when they start deteriorating.

 

For your application get the widest ones you can find to distribute the load on the boom as much as possible - you can get them in widths up to about 20 mm but they are not as readily available as the more common narrower ones

Mammut I believe makes the widest dyneema ones. 

 

Looks like these might be your Goldilocks.

https://www.backcountry.com/mammut-magic-sling-12.0?skid=MAM00T3-BL-S120CM&ti=U2VhcmNoIFJlc3VsdHM6c2xpbmc6MTo0MDpzbGluZw==

 

 

HW

Edited by Haligonian Winterr
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I have been using these for a couple of years.  I wouldn't go back to using the stainless bales which will be removed at the next opportunity.  They do need to be rotated often to prevent chafe, and they sometimes slide forward on the boom when sailing downwind.  I sometimes worry about dynamic loads, but we have had full-on crash gybes with the mainsheet accidentally jammed with no issues.

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14 hours ago, dash34 said:

I have been using these for a couple of years.  I wouldn't go back to using the stainless bales which will be removed at the next opportunity.  They do need to be rotated often to prevent chafe, and they sometimes slide forward on the boom when sailing downwind.  I sometimes worry about dynamic loads, but we have had full-on crash gybes with the mainsheet accidentally jammed with no issues.

1_inch_stainless_steel_footmans_loop.jpg

Footman Loops

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17 hours ago, dash34 said:

I have been using these for a couple of years.  I wouldn't go back to using the stainless bales which will be removed at the next opportunity.  They do need to be rotated often to prevent chafe, and they sometimes slide forward on the boom when sailing downwind.  I sometimes worry about dynamic loads, but we have had full-on crash gybes with the mainsheet accidentally jammed with no issues.

In the above pic you can see the wichard eyestraps we used to keep the loops in place. These are slid into the sail track and held in place with machine screws. On the 105 with a clew slug we added a cutout in the sail track just aft of the aft-most loop

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1 hour ago, ctutmark said:

On the 105 with a clew slug we added a cutout in the sail track just aft of the aft-most loop 

That's a bonny idea even without the boom strop.s

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