Anchors & Multihulls

[44'cruisingcat]

It's not so rare on the East coast of Aus. Some big tides in Qld, and many river anchorages in NSW, make this a reasonably frequent situation.

[Kiwikat]

We went to an open day at the local marine precinct at the weekend, somewhere in excess of 40 cats up there on the hard. Interesting to observe that approximately 95% of them anchored from the front beam or close to it. Nearly all of those ones also had some form of passerelle which our FP does not.

Still thinking that with our setup the boat does not seem to move around at anchor as much as other cats that we have observed but this could just be an illusion

[tuskie]

Originally Posted by Kiwikat

Still thinking that with our setup the boat does not seem to move around at anchor as much as other cats that we have observed but this could just be an illusion

When the anchor is deployed the attachment point is usually the forebeam ends/hull bows. This is pretty much the same for most cats, whether they have anchors stowed on forebeam or bridge deck. So, the amount they move around at anchor should be due to other factors such as windage, weight, wetted area, etc.

However, if your cat has an anchor stowed in the bridge deck, as your Bahia has, it must have a fairly long bridle. Perhaps it is this longer bridle that reduces boat movement at anchor? I personally favour longish bridles, each "arm" length about 120-150% of beam, but many prefer shorter. Just a thought, I don't have many!

[tomfl]

Originally Posted by tuskie

SNIP

However, if your cat has an anchor stowed in the bridge deck, as your Bahia has, it must have a fairly long bridle. Perhaps it is this longer bridle that reduces boat movement at anchor? I personally favour longish bridles, each "arm" length about 120-150% of beam, but many prefer shorter. Just a thought, I don't have many!

Still experimenting with bridle length. One thing I have noticed is that there is normally a little tide/current where I anchor. As a rule I start off with both sides of the bridle the same length, but after a while I will look at the Windex and if the nose of the boat is not pointing directly into the wind I may adjust one side of the bridle a little longer to try and have the bow point directly into the wind.

This is easy to do on my Seawind as I just let out a little line around the cleat on the bow of one hull. Not sure how easy it would be to do on an FP.

[Heath68]

In the Mahe 36 we were in we seemed to swing like mad.. I discovered that by lengthening the bridle to allow the weight to sit on the bridle rather than the anchor I minimised this.. so I ended up thus:

[AD28]

I think this might clarify:

http://www.amazon.com/Multihull-Seam.../dp/189866031X


A good start for bridle length is 2xBeam overall, ergo each leg is equal to the boat's beam. And yes, there should be a catenary of chain between the anchor locker/windlass/stopper and the bridle (as shown in the pic). Otherwise, the boat may as well not have a bridle.

[smj]

Originally Posted by AD28

I think this might clarify:



http://www.amazon.com/Multihull-Seam.../dp/189866031X





A good start for bridle length is 2xBeam overall, ergo each leg is equal to the boat's beam. And yes, there should be a catenary of chain between the anchor locker/windlass/stopper and the bridle (as shown in the pic). Otherwise, the boat may as well not have a bridle.

We've used a bridle on a nylon rode with good success. Will keep the boat pointed into the wind without the catenary of the chain.


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[AD28]

Chain or rope, you want your rode to have a catenary between the boat and the bridle. Else the system rides the rode and not the bridle, that is to say, pull will be on the "central leg" and not the two bridle arms.

[smj]

Originally Posted by AD28

Chain or rope, you want your rode to have a catenary between the boat and the bridle. Else the system rides the rode and not the bridle, that is to say, pull will be on the "central leg" and not the two bridle arms.

You are absolutely correct, the pull should be on the bridle and not the rode. If not then the bridle is useless.


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[44'cruisingcat]

Originally Posted by Kiwikat

We went to an open day at the local marine precinct at the weekend, somewhere in excess of 40 cats up there on the hard. Interesting to observe that approximately 95% of them anchored from the front beam or close to it. Nearly all of those ones also had some form of passerelle which our FP does not.

Still thinking that with our setup the boat does not seem to move around at anchor as much as other cats that we have observed but this could just be an illusion

It probably is. It always looks like a boat is moving more from off the boat.

[Seaslug Caravan]

Originally Posted by 44'cruisingcat

Wind against tide. The current holds the boat with it's stern to the wind, the wind drives the boat forward.

yes, depending on the boat, this forward rush can be quite severe. Enough to snatch the anchor out of the bottom, or if not, make movement around inside the boat, interesting to say the least (enough to throw one off their feet).

Its not just limited to cats that can't lift their underwater foils and rudders.

I watched racy Stealth 12 meter with foils retracted sailing around its mooring
(literally doing 360 degree rotations) in strong wind against tide conditions. Mini keel cats nearby were sitting stern too wind with their underwater drag dominating over their windage.

I have found for my situation that lashing my tillers hard over in these conditions doesn't allow the vessel to get a good run up on the rode and the vessel tends to lie quietly to her tackle.