Cruisers & Sailing Forums (http://www.cruisersforum.com/forums/)
-   Multihull Sailboats (http://www.cruisersforum.com/forums/f48/)
-   -   Catamaran Rode (http://www.cruisersforum.com/forums/f48/catamaran-rode-53835.html)

cat49 28-01-2011 05:36

Catamaran Rode
 
I am getting a 49' catamaran with a displacement of 18,000. i was thinking about a 88lb rocna with 150' of 3/8" HT spliced to 200' of nylon. My question is, is a different rope realistic? like kevlar or dyneema or spectra? if i use a snubber? Is the anchor way to big? i want something to where i do not have to worry about it at all.i want total piece of mind but at the same time i dont want to kill performance either. would 5/16"HT be better suited than 3/8"HT.

Ram 28-01-2011 05:58

I would go with twice the chain about 250 or 300 ft min- this you really need-I have 300ft of 3/4 nylon after my 250ft of chain-- chain-5/16 is too small for you-its only has a working load of 4000lbs-go 3/8HT chain the anchor is the right size and the right one- On a boat that size its not going to make any difference on weight of the extra chain and larger size on performance

cringle 28-01-2011 05:59

phone rocna ... they're very approachable and seem to know their stuff.

I don't think a kevlar rode is much of an idea ... you want something with some stretch and UV resistance. dyneema/Spectra (same stuff) is not much better as a rode - very little stretch. Use nylon.

Cotemar 28-01-2011 06:08

Cat49,

A Rocna 88 lbs (40kg) is perfect for your size & weight cat.
Stick with 3/8" HT, so you can use a larger shackel to the anchor and more room in the link to make your chain to rode splice. I would use 175' to 200 feet of chain just because the bridal to snubber eats up about 20 feet.

Mark

DotDun 28-01-2011 06:21

Quote:

Originally Posted by cat49 (Post 606672)
i want something to where i do not have to worry about it at all.i want total piece of mind but at the same time i dont want to kill performance either.

It's great you are thinking about this, but please don't be lulled into a false sense of security. There are conditions where even the biggest baddest ground tackle can let you down. Pay attention to where you drop the hook, bottom conditions, wind, wind predictions, current, other boats, and maintain an anchor alarm.

Total piece of mind and not worrying does not allow you to not pay attention!

Mark Johnson 28-01-2011 06:44

For a trimaraner like myself, that sounds like a lot of weight, but cats don't carry the chain all the way out on the bow... Plus, this is a BIG boat...

Sounds like a good safe combination, but you might want a bit more nylon. Also, use one size up HT shackle from "Crosby" that = or exceeds the 3/8" HT chain, and on the nylon... New England Ropes brait/plait construction, Mega Braid I think they call it... Is wonderful stuff! It stretches well, and is less stiff and prone to hockles than three strand. It is in a different world, regarding nylon snags in the haws pipe, from hockles!

Also... I agree 100% with the above, regarding the skill side of anchoring! 50% might be ones ground tackle, but 50% AT LEAST, is skill.

The difference between "Sailors" and "Cruisers", among other things, is anchoring skills!

Enjoy, Mark

Ram 28-01-2011 07:27

Quote:

Originally Posted by Mark Johnson (Post 606725)
For a trimaraner like myself, that sounds like a lot of weight, but cats don't carry the chain all the way out on the bow... Plus, this is a BIG boat...

Sounds like a good safe combination, but you might want a bit more nylon. Also, use one size up HT shackle from "Crosby" that = or exceeds the 3/8" HT chain, and on the nylon... New England Ropes brait/plait construction, Mega Braid I think they call it... Is wonderful stuff! It stretches well, and is less stiff and prone to hockles than three strand. It is in a different world, regarding nylon snags in the haws pipe, from hockles!

Also... I agree 100% with the above, regarding the skill side of anchoring! 50% might be ones ground tackle, but 50% AT LEAST, is skill.

The difference between "Sailors" and "Cruisers", among other things, is anchoring skills!

Enjoy, Mark

I argee 100% with you Mark-A qustion about that Mega Braid, whats the cost difference between that and 3 strand?

Mark Johnson 28-01-2011 08:05

RAM,
A few cents more per foot! Not an issue. Yale makes a similar rope that's 8 strand rather than NER's 12 strand version. I have used both, but NER has a higher WL (size for size), and being a bit firmer, might grip the rope/chain gypsie better? Yale's is a bit more flexable, but both fall in a pyramid pile like chain! I prefer the N.E.R. version...

ONCE YOU USE THIS STUFF, YOU WILL NEVER USE THREE STRAND AGAIN! The rope to chain splice is "really different", so the first one is a challenge, then they become no problem.
Mark

thinwater 28-01-2011 08:26

I think no one explained a key difference between chain and nylon:

* Chain absorbs the impact of waves by forming a catanary due to weight. The Rocna folks do not completely agree with this logic in extreme conditions; you can go there web site and read the explanation.
* Nylon absorbs energy by stretching as much 30% before breaking, with a working stretch of 5-10%.

The problem with Spectra and other high tech lines is that they do neither; no weight and no stretch. A snubber can help, but only when used in combination with chain or nylon. I also wonder how to handle the Spectra, since the windlass will be sized for nylon.

Additionally, 90% of the cat sailors use VERY strong bridles because they do not want failure; a boat with a failed bridle can damage the windlass and/or sail the anchor out. Generally, each leg is the same as the rode, and so is actually stiffer than the rode. This is rational on a multihull. However, the result is that a bridle is not actually an effective snubber.

I agree with the crowd, that you anchor and chain choices make sense; not unlike mine, but proportionally larger. One other problem with 5/16" chain is that it will restrict your nylon rode size.

Cotemar 28-01-2011 08:45

Here is a picture of my 200 feet of 8 strand plait rope & Chain splice.
Very easy to do.

http://www.cruisersforum.com/forums/...tml#post452041

Mark Johnson 28-01-2011 08:50

I agree with the above points except one... Multihull sailors need not, and should not, use a bridle of the same dia size as the rope portion of the rode! NOT EVEN CLOSE! It needs to stretch, and the load is evenly divided between the two legs!

I use a 30' X 3/8" bridle! If it fails, I never have the chain or rope portion of the rode, fixed by the windlass. That end of the rode is fastened with a chain fork to a stout cleat, or if it is the rope portion of the rode, it is fastened to that same cleat! This way your relatively weak but stretchy bridle has a backup that doesn't put a load on the windlass at all.

In named storms, I use an alternate... HUGE 40' long X 5/8 double braid nylon bridle!

Although my small 3/8" bridle has gotten me through countless 65 knot thunderstorms, with no problems at all, and it is about all I ever use.

The point above is a good one however, you need a stretchy bridle, more than strong one, since we have a back up!

Mark

cat49 28-01-2011 12:55

thanks for all the info i will go with a nylon/chain rode.....my next question is, is a 3/8"HT chain big enough or should i go up one more size also the rocna 88 should i go up to the 121? is that that just overkill? i want something that will hold in a hurricane force conditions. keeping in mind that the cat is only 18000lbs. loaded.

cat49 28-01-2011 12:56

also what do people recommend for a second anchor? and rode?

Cotemar 28-01-2011 13:08

cat 49,

Recommend a Fortress with 50' of 3/8 ht chain and 200' of 8 brade for your 2nd anchor.

Here is what I did for a 36' cat
http://www.cruisersforum.com/forums/...tml#post316215

thinwater 28-01-2011 13:37

Quote:

Originally Posted by Mark Johnson (Post 606824)
I agree with the above points except one... Multihull sailors need not, and should not, use a bridle of the same dia size as the rope portion of the rode! NOT EVEN CLOSE! It needs to stretch, and the load is evenly divided between the two legs!

I use a 30' X 3/8" bridle! If it fails, I never have the chain or rope portion of the rode, fixed by the windlass. That end of the rode is fastened with a chain fork to a stout cleat, or if it is the rope portion of the rode, it is fastened to that same cleat! This way your relatively weak but stretchy bridle has a backup that doesn't put a load on the windlass at all.

In named storms, I use an alternate... HUGE 40' long X 5/8 double braid nylon bridle!

Although my small 3/8" bridle has gotten me through countless 65 knot thunderstorms, with no problems at all, and it is about all I ever use.

The point above is a good one however, you need a stretchy bridle, more than strong one, since we have a back up!

Mark

Exactly. In my case I use a strong bridle because I have a fiber rode, I don't care about stretch, and it was the rope I had. I think this is common practice, particularly on cats, when the windlass is mounted on one hull.

I also think that the stretchy bridle makes even more sense on a tri; the legs are longer and it might actually help, where on most cats they are simply too short to contribute useful stretch. there are a great many people that believe a 6' snubber is effective; really, a snubber needs to be ~ 10-20x the greatest wave height to do much. 40' is more to the point.


All times are GMT -7. The time now is 04:41.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2018, vBulletin Solutions, Inc.


ShowCase vBulletin Plugins by Drive Thru Online, Inc.