Rode calculation

[Rum_Pirate]

Found this :

Determining how long your anchor rode should be is as simple as multiplying the deepest water you expect to anchor in by 8. ​

​

As for rope size, the rule of thumb is 1/8" of rope diameter for every 9' of boat length.​

What are your (helpful and polite) comments/suggestions?

What to you use to minimise chafe?


PS The vessel I am concerned about is a Corsair F-27 trimaran, i.e. main hull 27'0"wth a beam from outrigger to outrigger is 19'1".

 

[Tranona]

*8 is a bit OTT. Rope rodes are less common over here, but mixed chain/rope are. Chain for the first bit is helpful if only for abrasion where it lies on the seabed. Chain also gives catenary which is useful for reducing scope when anchoring in crowded places - reduces swinging room in lighter conditions and provides some shock absorption.

Unless you habitually anchor in demanding conditions a chain/rope combination of, say 10m of 6mm (1/4") with 40m 12mm (1/2" 3 strand or Octoplait would be good for anchoring in up to 10-12m water.

Length of boat is a crude measure as your tri is a very different beast from a 27' deep keel sailboat. The key thing you need to consider is the load placed on the boat, primarily by wind then weight. Multihulls and modern high freeboard, low underwater area boats generate far higher loads than older style low windage, deep bodied boats of the same notional length.

All a bit academic as the sizing suggested is plenty strong enough for any of them. you won;t get anywhere near the limits even with the best anchor!

 

[William_H]

Thickness of rope rode must be dictated by what is convenient to handle in pulling it all up. So nothing less than 10mm diameter. Perhaps 12mm for larger boat. I would think breaking strain of 10mm would be adequate. Plus of course the thinner rope will have more stretch/elasticity. As an anchor is seen as safety item length should be at least 30m. ol'will

 

[Rum_Pirate]

Am temporarily using 1” main with 3/8” ‘bridles’ to each outrigger.

thinking of going down to 5/8” main.

 

[Refueler]

*8 is a bit OTT. Rope rodes are less common over here, but mixed chain/rope are. Chain for the first bit is helpful if only for abrasion where it lies on the seabed. Chain also gives catenary which is useful for reducing scope when anchoring in crowded places - reduces swinging room in lighter conditions and provides some shock absorption.

Unless you habitually anchor in demanding conditions a chain/rope combination of, say 10m of 6mm (1/4") with 40m 12mm (1/2" 3 strand or Octoplait would be good for anchoring in up to 10-12m water.

Length of boat is a crude measure as your tri is a very different beast from a 27' deep keel sailboat. The key thing you need to consider is the load placed on the boat, primarily by wind then weight. Multihulls and modern high freeboard, low underwater area boats generate far higher loads than older style low windage, deep bodied boats of the same notional length.

All a bit academic as the sizing suggested is plenty strong enough for any of them. you won;t get anywhere near the limits even with the best anchor!

One of your shortest posts ! But one that I agree with 100% ... not that anything I agree with is necessarily correct !!

The point of windage and lack of underwater body is often forgotten by many. I have maintained for years that a small motor boat with very little in the water can skit about and put far more strain on an anchor system than many realise.
Tri's ... Cat's .... similarly .....
Even that Devils design of McGregor 26 can be more trouble at anchor than a Centaur or other 26ft traditional boat.

The snatch of such boats can be surprisingly sharp and strong.

Anyway - I am a chain only rode unless I am really deep water when my chain is then backed up by octoplait rope. To give an idea ... only time I see that rope is once per year when I drag all out and check chain and rope condition.

 

[simonfraser]

rode x wind beaufort number works for me

 

[Plum]

rode x wind beaufort number works for me

I assume you mean depth x Beaufort?

Www.solocoastalsailing.co.uk

 

[simonfraser]

I assume you mean depth x Beaufort?

Www.solocoastalsailing.co.uk

yes

 

[Boathook]

Found this :

Determining how long your anchor rode should be is as simple as multiplying the deepest water you expect to anchor in by 8. ​

​

As for rope size, the rule of thumb is 1/8" of rope diameter for every 9' of boat length.​

What are your (helpful and polite) comments/suggestions?

What to you use to minimise chafe?


PS The vessel I am concerned about is a Corsair F-27 trimaran, i.e. main hull 27'0"wth a beam from outrigger to outrigger is 19'1".

As per others 10 metres of 6mm chain and then 12 or 14mm 3 strand 'nylon' or anchorplat. For that combination 5 times depth (from bow roller to seabed). How much rope you will require you need what depth of water you will normally anchor in and then add some spare.
To minimise chafe on the rope I use flexible plastic tube slipped over the line.

 

[vyv_cox]

I remember watching boats lying to anchor in Tranquil Bay in the Ionian. Tranquil Bay does not always live up to its name but on that day it did. Wind was very light and highly variable, blowing from every conceivable direction for short periods of time.

The anchorage was crowded as usual. One boat, around 32 ft, was on a rope rode. Everybody else was on chain. The one on rope was an absolute nuisance, colliding with at least three other boats that I saw as it reacted to wind changes far more rapidly than anyone else. A kellet might have solved it but a nuisance to deploy. Chain is really the only answer for extended cruising in popular places

 

[boomerangben]

I remember watching boats lying to anchor in Tranquil Bay in the Ionian. Tranquil Bay does not always live up to its name but on that day it did. Wind was very light and highly variable, blowing from every conceivable direction for short periods of time.

The anchorage was crowded as usual. One boat, around 32 ft, was on a rope rode. Everybody else was on chain. The one on rope was an absolute nuisance, colliding with at least three other boats that I saw as it reacted to wind changes far more rapidly than anyone else. A kellet might have solved it but a nuisance to deploy. Chain is really the only answer for extended cruising in popular places

Sounds like time for Norfolk Broads style mud weight secured to the quarter. Or the kedge on a short rode