Wing Keel Soft Mud In Slip

rpwillia · May 28, 2015

Should not hurt the boat

Monterey385 said:
Looking for thoughts regarding the impact of letting a 38-40 foot Catalina with a Wing Keel settle 18" into the mud during lunar low tides and 3"-4" into the mud in lower/low tides about 10 times a month.

Slip/Marina is well protected for storms and a great community.

Have seen a number of Catalina's deal with up to 30" of mud routinely ... just not sure about the long term impact.

But you will have a lot of times when you boat is not available. Perhaps you can figure out a way to dredge the slip a bit. I am guessing a 38' Catalina only drafts about 5' so if you are 18" into the mud that means you are only standing in about 3.5' of water. We had an extreme low tide along with winds a few years ago that exposed the mud of a lot of shallow slips on the Potomac years ago.

FWIW, I see on your profile Long Branch, NJ. Grew up there.

jibes138 · May 29, 2015

Take a dive with a mask and see what it looks like when it is in the mud. Is it just squashing the mud and the top of the keel wings are exposed? Or is the mud filling in over the top of the wings making it an anchor? Any wave or wind action will mean the boat has continuous motion while it is settling into the mud so that may come into play. Your keel joint is probably under 50,000 pounds or more of compression from the torque on the keel bolts. To get this compression the torque on the bolts stretches the bolts in tension within their elastic limit so they are acting like a spring. Putting tension on the bolts to pull the keel out of the mud will increase the stress on the bolts which is OK if it is within the elastic limit below the yield point on the stress-strain curve. If the load goes above the yield point you will permanently stretch the bolts that will be seen as loss of torque on the bolts when the boat returns to fully floating. The other failure mode might be compressive stress of the layup under the keel bolts. Depending on the size of the backing plates and so forth you could calculate how much force is being applied to the area from the combined force of the torque on the bolts and the added force of pulling the keel out of the mud. If this is above the allowable compressive stress of the material it will fail, if not you will be OK. So to answer your question requires an understanding of the forces involved and some easy calculations to see if the material strengths have enough safety margin to not cause a problem. So you need an engineering evaluation to get a true answer. Roger Long is a naval architect and for a reasonable retainer might be persuaded to take on your challenge to figure this out. Last known location was somewhere up the Hudson River but try PM'ing him to see if you get a response.

JK_Boston_Catalina310 · May 29, 2015

Measure the actual draft of the boat. Catalina listed my boat a 4'6" but it's closer to 5' loaded for cruising.

The Garbone · May 29, 2015

Our first boat was in a silk filled slip when be bought her. Took a good 15 to 20 minutes in reverse before she pulled her fin keel out of the mud. Had her hauled for a bottom job and she had clams on the bottom of the fin.

woodster · May 29, 2015

if you get stuck and can't pull out of it get a 1/2 water pipe about 10 ft long and hook it up to a water hose ...then put the open end of the pipe down in the water close to the keel and start washing the mud away from the keel this call called "well pointing" you can change the direction of a river doing this given enough water pressure and persistence it will also in your case free up the keel with minimal concern and effort...just a good trick to remember incase you ever need it

Chief RA · May 29, 2015

Good info Woody! Chief

Sandy Stone · May 29, 2015

I think I'd be more concerned about the rudder - on most shallow draft boats the tip of the rudder is only a few inches shorter than the keel, so you would be burying it as well. If there was any real wave action, you could put a lot of stress on the rudder shaft and bearings.

Ron20324 · May 29, 2015

woodster said:
... get a 1/2 water pipe about 10 ft long and hook it up to a water hose ...then put the open end of the pipe down in the water close to the keel and start washing the mud away from the keel this call called "well pointing" you can change the direction of a river doing this given ...

When my marina was rebuilt, they did the power washer ahead of the pilings they could drive no father. It got them additional depth to bedrock.

CCrane2299 · May 29, 2015

I saw the owner of my marina tie his pontoon boat to the dock with two stern lines that were long enough to get the engine/prop where he wanted them. He put the engine in gear and under very light power just kept turning the engine left and right until he had cleared enough silt to make him happy. I'm sure it will fill back in over time, but it worked really well.

pateco · May 29, 2015

I dove my dock last weekend with a home made Air lift, and moved almost 3 feet of sand/old oyster shell from under my keel to under the dock against the seawall. I am going to check this weekend to see how I did when its low tide. previously, I was having to wait almost 3 hours after low tide to be able to leave my dock, and had to return at least 3 hours before the next low. That gave me only a 6 hour window to sail, even with favorable tide timings.

Crazy Dave Condon · May 29, 2015

Years ago I recall being sent a photo of a larger Catalina wing keel that physically was sitting upright on its lead wing keel with no visible signs of damage which was a testimonial t the thickness of the wings. However the rudder was off the ground. Sandy would be correct about the concern of the rudder. However mud is soft when wet. I would worry about any debri such as metal, rocks and so on if in the mud. You might want to check on that.

Why not pose that to the chief designer, Gerald Douglas, at Catalina factory in Florida for a good response.

Bill Roosa · May 29, 2015

If she hits bedrock then no damage but may tip in the slip. Some way to install a tip direction and dock lines to support that engineering would be in order.

Rick486 · May 29, 2015

jibes138 said:
Take a dive with a mask and see what it looks like when it is in the mud. Is it just squashing the mud and the top of the keel wings are exposed? Or is the mud filling in over the top of the wings making it an anchor? Any wave or wind action will mean the boat has continuous motion while it is settling into the mud so that may come into play. Your keel joint is probably under 50,000 pounds or more of compression from the torque on the keel bolts. To get this compression the torque on the bolts stretches the bolts in tension within their elastic limit so they are acting like a spring. Putting tension on the bolts to pull the keel out of the mud will increase the stress on the bolts which is OK if it is within the elastic limit below the yield point on the stress-strain curve. If the load goes above the yield point you will permanently stretch the bolts that will be seen as loss of torque on the bolts when the boat returns to fully floating. The other failure mode might be compressive stress of the layup under the keel bolts. Depending on the size of the backing plates and so forth you could calculate how much force is being applied to the area from the combined force of the torque on the bolts and the added force of pulling the keel out of the mud. If this is above the allowable compressive stress of the material it will fail, if not you will be OK. So to answer your question requires an understanding of the forces involved and some easy calculations to see if the material strengths have enough safety margin to not cause a problem. So you need an engineering evaluation to get a true answer. Roger Long is a naval architect and for a reasonable retainer might be persuaded to take on your challenge to figure this out. Last known location was somewhere up the Hudson River but try PM'ing him to see if you get a response.

With respect, this sounds like gibberish.
Dr. Rick (Ivy League PhD in ME)

rpwillia · May 29, 2015

+1 on Woody's Idea

Chief RA said:
Good info Woody! Chief

That actually sounds like a cheap and easy way to get more depth in the slip. I do know one way they install pilings down here is some kind of gizmo that goes around the piling and they hook air up to it and let it blow the sand away until the get the piling down to the depth they want. Afterward the sand just settles back in around the piling to hold it.

Kermit · May 29, 2015

woodster said:
if you get stuck and can't pull out of it get a 1/2 water pipe about 10 ft long and hook it up to a water hose ...then put the open end of the pipe down in the water close to the keel and start washing the mud away from the keel this call called "well pointing" you can change the direction of a river doing this given enough water pressure and persistence it will also in your case free up the keel with minimal concern and effort...just a good trick to remember incase you ever need it

Plus you'll be putting extra water under the keel. That oughta raise you right up!

MrBill_FLL · May 29, 2015

Try a jet nozzle on 10' of pvc connected to garden hose. I'd want to be sure there's no big rocks underneath

http://www.homedepot.com/p/Orbit-Walkway-Tunnel-Kit-53333/100127846

ifmdalvey · May 31, 2015

I may have missed something in this whole discussion, but assuming you are paying good money to the marina, why don't you request a slip that is suitable for your Catalina`s draft? rather than being stuck in a unsuitable slip.