Interesting New Sheaveless Block

One more thread I will never go back to.

Holy cr*p! Are you telling me there is false and hurtful stuff on FB and/or the inner-net?

Dang, there goes my seawater engine I just bought from that nice russian dude...

I should probably go back and read that myself... They're re-opening some wells here in my region (they've been pumping for over 50 years with nary a blip on the public opinion screen) and it's got people out flipping over cars and rioting in the streets.

Where is that tin-foil hat I wear? Did I loan it to Timbo?

Way to turn a useful thread into a bunch of $#it guys.

Did you get plonked or quoned?

In a (perhaps vain) attempt to resurrect the thread, I think I found a good role.

Want to convert my trap setup to adjustable, and thinking these might be just the ticket instead of using the double block. Too much friction? is MWL of 380# enough?

Jeff,

Maybe you've been following my thread on that other beachcat site. I had the same idea, and ordered the parts. The official Nacra and C2 double blocks used in the adjustable setup are ~$55 EACH. The ronstan double block is a ~$25 part. There is a knock off of the Ronstan/Harken part but I don't trust knock off's in a safety critical application, when the name brand guys see failure.

So I went with the shock blocks at $16 a pair from a local supplier (sorry Rick I might return these don't want to double pay shipping). My intention is to splice them together to form a double block using dyneema. To be fair to Ronstan I don't think this is the intended purpose but others have done it with Antal rings. My concerns are the following:

1) MWL; in a 2:1 setup I'm 185lbs wet so you're looking at 370#'s of load on the block. Other have pointed out you may see 2-3g's of acceleration occasionally so you may apply up to 3x that number, 1110 lbs. That exceeds the breaking load of the shock block. However, it's an aluminum block so it won't just snap. It'll likely deform and since you are only applying high loads for temporary periods of time. Finally, one must remember Ronstan designed these for similar applications/load cases on kite boards.

2) Friction. I went with 3/16

(5mm) diameter line which is commonly used in adjustable trap setups. Somewhere I saw (Murrays?) the shock block ideal line diameter tops out at 1/8

. Now that I've seen that I'm going to go down to 4mm (another reason to shop locally) line, which actually increases my line cost. Previously I spec'd Excel Pro which has a 1511$# tensile strength in 3/16

diameter, but a mere 695# tensile strength in the 5/32

diameter (4mm). Hence I'll switch to a dyneema cored line, FSE Dinghy Control Line which is a nice running line and has decent price/performance ratio. In 4mm this has a tensile strength of 1574#'s. I want the blocks to explode before the line does.

I'll post photos and reviews of the system when I'm done. I'm doing this right but trying to save money where it makes sense. Also want a reliable system for ocean racing so if the shock blocks don't work they'll get returned.

Friend of mine had the new Ronstan sheaveless on his kite, I was surprised to see how tiny they are, not sure if I would feel comfortable putting any serious load on them.
Since they are probably made in a mould there is a sharp edge right in the middle of the block, noticed some line chafing there already after just a few hours of use.

I have been using these cheap (RKO i think) blocks on my adjustable trap set up for years...

I had to replace one set after a few years because they can get side loaded up and deform. I now tape or whip them together so that can't happen

Adjustable traps seem to be too much to screw with to me. I just use the standard dog bone. If I want to trap low, I use the low hole. I want to be higher, I use the high hole.

Plus, the more parts you introduce to a system, doesn't matter what it is, the more parts there is to fail. You could probably do away with the block too. Just use a sailmaker's thimble there. Other parts of that part of the trapeze will probably wear out before the wear from the thimble becomes an issue.

This is all I use, clean and simple:

I don't shackle the block on any longer, I just use a Harken 504 (I think that's the number) and put it through the thimble when I make my trap lines.

I used to always make them from the top down. I'd make the splice that attaches to the mast first, then set my handles and do the eye at the bottom. Where the handle meets the thimble it creates a wear spot and I think the solution to that is to just tie a stopper knot, (probably just an overhand knot would be sufficient), in the dyneema for the handle to stop against and have the thimble with the block an inch or two below that knot. Should be wicked durable that way.

To deal with the handle chafing the line at the thimble, I push a short cut line through the trap line (including the eye-splice tail, bend it back, and whip the line like mad. Then I put a piece of shrink wrap over it so the handle jams on the line and doesn't reach the thimble. I do like the idea of these blocks in this application because chafe at the sheave can be a real problem with the take-up tail.

I've taken that dogbone to the teeth a few times, which is why I prefer that wire loop with the plastic insert. Even when the insert/spacer fails, the wire loop remains viable.

But your setup still looks sweet. What size is that trap line to the mast?

yup , everything is a trade off. I have had them fail.

I prefer the ability to pull myself up and away from a swell in the gulf ....

I don't use those

can't miss trapeze handles

anymore ...

I had the wire rust away (where it wasn't visible) and dump me

I'm looking at the Ronstan linked blocks #RF20284. Working load 550lbs. BL 1210 lbs. These 20mm blocks come regular and high load.

3mm. I think I'd like to go smaller, but I use that same size all over the boat and I usually buy it by the spool. A spool of 2mm would last me a lifetime just using it on trapeze parts.

The 2.5mm (7/64

) Amsteel is fine for trap lines. Just be ready for it to have some initial stretch. My a-cat lines stretched about 4-6

before taking a final set.

Jake how many sails and how many times did you adjust before it locked into a range +/1 1/8 of stretch (ie Final stretch point)

It didn't take long. It was done stretching mostly after the first day. It was a good day with 12+ winds so I was on the wire most of the day. That evening I remember looking at it thinking

crap, that stretched a lot

and I had to resplice it.

how hard was it to re-splice once you tensioned the line?

Karl,
Why not just get rid of the small microblock (H224) below the handle and just run the line through the thimble. I do this and it works flawlessly. Clean and simple.

What is everybody else doing up top to prevent chafe, or are you just leaving it bare? You guys using 4 seperate pieces or 2 pieces doubled/Brummel on double hand boats?

This is what I do too an its where I'm adding Antel thimbles on the new set to cut down a little on friction compared to the normal rigging thimbles.

On my current wires I have 6 inches or so of lacing at the top which gaves me the ability to adjust the length (To allow for creep in the inital setup) and also provide this chafe guard. What a lot of people do is just thread the lines through 6 inches of normal sheaving that has been stripped from easewhere on the boat, other use some rubber hose.

With regards to minimising creep, leaving the line you have purchased in one long length do a splice at each end that will become the top end of the lines. but before you do so put an old block in the middle of line. Now tie the two spliced ends to a tree or post and connect your mainsheet block to the block you have floating in the middle and pull the whole thing towards another tree or post. Go back every half hour and make it a bit tighter. Once you're happy it is not getting any longer or the tree falls down cut it in the middle and splice on the other end. Assume you'll get another inch of creep in the final splice.

First, Jake thanks for the amsteel stretch notes I'll re-splice to accommodate. If you leave the bottom splice adjustable you can account for this in time

Karl, the dog bone works well and I think is a great option for skippers primarily buoy racing and single-handers. For a distance racing setup I like the adjustable setups. Gets my butt out of the waves, and lets me trap lower than a dog bone setup ordinarily allows as crew. Less critical for the helmsman but the crew ends up on that wire too.

I went with 4 separate lines. More difficult to manage for rigging but the splicing was easier. We have no covers at the top for chafe but am curious what others are doing. I might slip some on since I grabbed a bunch of scrap the other day.

Please elaborate, not sure what you mean here. Lacing?

My

wires

are deliberately 6" to short then I lash it to the shackle on the mast with some 2mm chord. Sorry boat lives at the club and I don't have any photos.

Got it. Thanks

Not hard at all. Amsteel is pretty easy to work with even after it's been stressed.

I cover the line with cover I strip from some Excel Racing Pro where it could chafe. It gets covered in the eye splice (at the hound) and down the mast a little where it could rub/catch the rigging.

Hi Catman,
Ronstan block you are looking for:
http://www.catsailor.com/store/pc/s... ltCnt=10&keyword=RF20284&submit=

I suggest using Rick's block posted above or the equivalent Harken. The Ronstan shock blocks are too small for this application, they are tiny! I went with a single Antal ferrul instead; 2 spliced together would be perfect but there isn't much room to splice.

The shock blocks look perfect for replacing small blocks that lead shockchord around the boat!