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Old 29-11-2008, 17:39   #1
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Getting a Cat Out of the Mud

I saw a boat today that had the rudder posts bent when a previous owner - inexpertly - extracted himself from a shoal. Not serious, and not enough to need repair. However, since my last cat had kick-up rudders (Stiletto) and my new one has fixed rudders (PDQ) I need to learn about this. Soft groundings on mud or sand are my concern.

I have read many bits in books and posts about getting monohulls off - it happens more often, clearly - but nothing about getting a cat off. Advice to heal the boat would be pointless. Getting the boat to pivot around the keel seems much more difficult. Going straight backwards seems dodgy, since the rudders are only a few inches shallower than the keel and will touch when the boat starts to lean back under the strain of a tow or kedge.

I know there is no one-size answer to such a question, but your thoughts are apriciated.
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Old 29-11-2008, 17:54   #2
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On a vessel that that has fragile running gear such as the one you described, you would want to be very careful getting it ungrounded. If I was on a job like that, waiting for the highest tide to come back in would be the best option. If it was not grounded too hard due to falling tide, I could attach lines and lightly flush away the ground under the vessel with a tow vessel,essentially digging a hole under the running gear until it was refloated and able to pull it off the shoal.
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Old 29-11-2008, 18:22   #3
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On a cat I would think that an inflatabal bag large enough to take up the intire center span between the hulls and fore and aft inflated to just several psi would do the trick..Think along the lines of the bouncy outdor contraptions for kids to play in.

Some salvor my have such an air bag.

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Old 29-11-2008, 18:40   #4
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I have float bags, compressers, dive gear and whatever it takes to salvage a vessel. I refloat grounded vessels all the time. The problem lies in the cost of the work. It is called a salvage when salvage equipment is brought out to the seen. Anytime floatbags are used, it is determined to be a salvage and the cost sky rockets. Hey that's what insurance is for. Although I have helped many people that were not insured and cut them breaks. Salvage companies take on alot of responsibility when it comes to ungrounding half a million dollar yachts and our insurance rates are very costly.

For the most part, cats can be pulled out with patience and with techniques I described above. In some cases, yes the float bags need to be deployed because wind and waves pushed the vessel to far on the shoal making it impossible to simply flush on it and pull it out even with a high tide.
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Old 29-11-2008, 19:45   #5
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i allways thought a air mattress (or two as the case of a cat)might be the savior we are all lookin for in a emergency,put it under as far as possible first then inflate it.
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Old 29-11-2008, 21:36   #6
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PDQ, not an issue

There's a big difference between theory and experience, and when it comes to going aground in mud in a PDQ 36 I can match anyone! I've been seriously aground in mud in a PDQ 36 maybe 5 times. Dragging anchor in mud more like oil, running aground in places which were unmarked, storms forcing you out of a narrow channel in blinding rain and 70 knot winds from the side. I've never ever had an issue getting the boat off or needed to be towed. The PDQ has long flat keels, so rather than sticking in like a blade would with a fin keel it acts more like a snow shoe distributing the weight of the boat evenly and makes extraction a breeze. If you actually go straight into mud, simply reverse engines and porpoise them a bit and you will be able to 9 out of 10 times extract the boat straight back. The 9 hp engine really can't put enough force on the twin rudders to bend them and the boat is very light.

If you've done a serious grounding where you can't back up, then get out the dingy and bring out your anchor and kedge yourself off sideways, being patient and allowing an incoming tide to do most of the work for you. Your going to try to twist the bow sideways to allow you to go straight out. Be prepared for an incredible mess in mud spraying everywhere. The dingy and engine I used was a 8 hp engine, so again, nothing really powerful is needed.

By the way, probably the reason that there isn't much written about getting cats extracted from being aground is it's such a non issue. Let's see, on my present cat I did it last year, again, shallow flat keels allowed me to simply steer to the side, increase the motors and get off a mud bank that I should have known was there.

Good luck and happy grounding!!!
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Old 29-11-2008, 22:26   #7
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I grounded my Privilege 39 doing about five knots on the flats in Suva Harbor in Fiji. Fortunately, I had two kids that jumped off the bows into the water, and they helped push the boat off while I applied reverse power on the engines.

The engines were ineffective in extricating the catamaran on their own. The boat was truely stuck. When my kids got in the water, they pushed the bows up and down so that there was a modest hobbyhorseing motion to the hull. The hobbyhorsing affected the way that the keel interacted with the bottom, and I was able to motor in reverse off the flats. I think that hobbyhorsing decreased the surface area in contact with the bottom at any one instant making it easier to motor off in reverse.
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Old 30-11-2008, 04:00   #8
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Quote:
Originally Posted by maxingout
... The boat was truely stuck. When my kids got in the water, they pushed the bows up and down so that there was a modest hobbyhorseing motion to the hull. The hobbyhorsing affected the way that the keel interacted with the bottom, and I was able to motor in reverse off the flats...
Quote:
Originally Posted by thinwater
... Soft groundings on mud or sand are my concern.

I have read many bits in books and posts about getting monohulls off - it happens more often, clearly - but nothing about getting a cat off. Advice to heal the boat would be pointless. Getting the boat to pivot around the keel seems much more difficult...
The problems associated with a soft grounding in MUD (especially saturated
or near-saturated clays), are generally related to the incredible suction force* that mud can generate - as much as 100 pounds of vacuum per square foot of surface interface, (and to a lesser extent the adhesive force). Generally, the flatter the object, the greater the suction.

Soft viscous sand can exhibit similar suction properties.

* Think suction cup or mushroom mooring.


The key to releasing a grounded keel (or hull) from mud, is to gently break this suction force.

Pivoting & rolling (monohulls), or rocking & hobby-horsing (multihulls & monos) allows water to fill the voids (between keel & mud) created as the boat is moved.

Another method of breaking the suction would be to mechanically introduce air or water into the suction interface. Use a water/air hose to break the vacuum.

This is definitely a situation where patience will win out over the application of brute force.

I have absolutely no experience un-grounding Catamarans.
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Old 30-11-2008, 07:09   #9
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Schoonerdog if you own the record for PDQs I own it for LAgoons But on the subject, usually a bit of wave action or wake is always a help. Or just wait for the tide's help. I had to wait for an entire tide cycle once! But remember you are sitting level so it's not so bad!!! If backing off I always make sure the rudders are clear, by just moving them back and forth. Then backing off is my method. It seems that going forward has always just got me stuck worse. Having two engines allows you to pivot back and forth while a little bit of reverse is applied.
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Old 30-11-2008, 07:33   #10
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Thank you all.

I feel much better now. But "happy groundings" is up there with "may you live in interesting times"; a blessing best bestowed upon someone else!
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Old 30-11-2008, 11:14   #11
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As the party of the first part, he who is being discussed here, I would like to point out that grounding a cat is usually a non-event. Grounding in mud is unlikely to cause any damage at all unless you spend a lot of time digging mud with your propellers and sucking mud through your cooling system, air-conditioning, or head. PDQ owners, as well as Seawind, Lagoon, Fontaine Pajot, Catana, and you name it other cats all ground occasionally when sailing in muddy shallow water, regardless of where; with impunity, and many intentionally dry out to do repairs and touch up bottom paint. rudder shafts get bent when a moving object encounters something underwater that is harder and unmovingl like abandoned anchors, oil equipment detritus, shipping containers, or wrecks. That has happened to you already, or it will. Plan on it, or hang your rudder on a full keel. Its a choice!

The rudder I bent (4 degrees) likely occured in a deep wake from a passing 40 ton cruiser in six feet of water. Karma.

Cats are more likely to be in shallow water simply because we can!

Welcome and congratulations Thinwater!
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Old 30-11-2008, 15:50   #12
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We got in amongst the mud a few times this year and like others have said, getting off was a non-event, we just engaged reverse and ploughed our way out. A monohul that was unwise enough to follow us,one time, wasn't so lucky.

We do carry two inflation ballons and have a big RIB. My plan, if stuck on mud or a reef, has always been to put the RIB under the bridgedeck and inflate the inflation balloons. I've no idea whether it would work and often doubt whether carrying them is worth the extra weight.

On the subject of a cat on a reef, when in Antigua we happened on a Wharram cat called Tirla the night after she had gone on a reef at Green Island. She was sitting up on the reef as right as rain, but by the time the owner had returned a few days later with a salvage boat the port hull had disintegrated below the water line. This convinced me that you have to act fast to save a cat in this situation. It would probably have been best if the owner had stayed on board and tried a combination of sail, power and kedge to get her off at any cost. Even with a breached hull she would have floated, but with no hull I guess the owner ended up just salvaging the gear.

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Old 30-11-2008, 21:48   #13
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I'll just raise the daggerboards. She draws 2'-6" then. If that doesn't work, I will stand on the bottom and push
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Old 02-12-2008, 10:20   #14
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Best case scenario. Carry 600# of mobile ballast. When aground, discharge the ballast to lighten ship, tell them to push, and feed them a beer or two when they get you off the grounding. Downside: mobile ballast blocks the view of the bow bunnies.
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Old 03-12-2008, 19:42   #15
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Excellent idea, but consider; standard bow bunnie with all accessories installed weighs approx 120lbs. 5 of these could serve double duty with no compromise to the view. Drink less beer too.
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