USING A BOAT LIFT ON A SAILBOAT

p3dave

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Jun 18, 2020
6
Hunter 306 Pensacola
I have a 30 foot, 10'9" beam, 3'10' draft and I am looking at putting it on my boat lift. The lift was setup for power boats, with bunks that can be moved in an out made of aluminum and covered with vinyl or rubber. I have been looking at various modifications online, most feature a keel stand and stanchions just like a land cradle. Is there any issue with not supporting the keel and just letting it hang? Any ideas or suggestions?
 
May 17, 2004
5,554
Beneteau Oceanis 37 Havre de Grace
I have a 30 foot, 10'9" beam, 3'10' draft and I am looking at putting it on my boat lift. The lift was setup for power boats, with bunks that can be moved in an out made of aluminum and covered with vinyl or rubber. I have been looking at various modifications online, most feature a keel stand and stanchions just like a land cradle. Is there any issue with not supporting the keel and just letting it hang? Any ideas or suggestions?
Depends on the model of boat, but most are designed to have the weight of the keel supported from underneath when not in the water. If not supported the hull could deform over time. Deformation could result in a number of issues, like doors not closing properly, prop shaft alignment issues, and rig tension changes. It could also lead to “oil can” indentations in the hull where the weight is being held, again depending on the boat.
 
Jan 11, 2014
12,748
Sabre 362 113 Fair Haven, NY
Most of the weight of the boat is in the keel. It needs to be supported or it will deform the hull and possibly damage it. The boat can support the keel in the water because the weight of the keel is distributed over the entire submerged hull. The bunks or pads concentrate all the weight in a small area that is not strong enough to support the weight for any length of time.

The only time it is OK to not support the keel is when it is in the travel lift and being launched. That is a very short time, and the travel lift straps support the hull at its thickest and strongest part.

Pads and bunks only serve to keep the boat from falling over.
 
Oct 19, 2017
7,946
O'Day Mariner 19 Littleton, NH
The weight of a cubic foot of water is 62.4 pounds. If you have a fin keel that is approximately 6" wide by 3 feet long by 4 feet deep, that displaces 374.4 lbs of water. Hauling your boat out and letting the keel hang, would be the same, in this case, as adding 374.4 pounds to the middle of your boat.

-Will (Dragonfly)
 

RoyS

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Jun 3, 2012
1,742
Hunter 33 Steamboat Wharf, Hull, MA
Will, you lost me with that statement.
 
Oct 19, 2017
7,946
O'Day Mariner 19 Littleton, NH
The weighted keel hangs freely beneath the boat when in the water, except for the support of the water as displaced by the keel's volume. In the example case I used, that volume would mean the water only supports about 375 lbs of the keel's weight. The rest is dead hanging under the boat. I think I gave my example keel more volume than a typical 30' sailboat would have, to be generous with the numbers. Let's say the weighted keel weighed 2000 lbs. That means, the boat is holding up 1625 lbs of keel, just sitting in the water. I seriously doubt that hanging the extra 375 lbs would not have much effect.

-Will (Dragonfly)
 
Jan 11, 2014
12,748
Sabre 362 113 Fair Haven, NY
The weight of a cubic foot of water is 62.4 pounds. If you have a fin keel that is approximately 6" wide by 3 feet long by 4 feet deep, that displaces 374.4 lbs of water. Hauling your boat out and letting the keel hang, would be the same, in this case, as adding 374.4 pounds to the middle of your boat.

-Will (Dragonfly)
It is not about the absolute weight, it is about the area over which the weight is distributed.

Using my 15K lb boat as an example. The submerged area of the hull is around 350 to 400 sq feet. In the water, this works out to about 37.5 lbs per square foot. If the boat is placed on 4 pads with no weight supported by the keel, the weight on each pad is 3,750 lbs per square foot, 100 times the load.

Hulls are constructed with very thick keel stubs and much thinner upper sections. Again on my boat, the hull around the keel stub is over an inch thick, just below the waterline it is about half that. When the boat is on the hard with the weight on the keel, the weight of the boat in excess of the keel weight is supported by the thickest strongest part of the hull. So instead of having 15K lbs supported by 4 sq feet of ½" thick fiberglass, there is only 10K lbs supported by 1" thick fiberglass.

Even with the weight supported by the keel, the hull will deform as it sags over the keel and pads. When properly blocked, the deformation is small measured in fractions of inches, but it happens.
 

reworb

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Apr 22, 2011
234
Beneteau 311 Ft Myers Beach
All of the sailboat on lifts that I have seen around here have a central beam on which the keel sits and props to "balance the boat" I have kept/ keep two sailboats on a lift both were/are wing keels not sure how it would be in the case of fin keel. I would be happy to post a picture of my Beneteau on the lift if you would like to see.
 

HMT2

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Mar 20, 2014
900
Hunter 31 828 Shoreacres, TX
All of the sailboat on lifts that I have seen around here have a central beam on which the keel sits and props to "balance the boat" I have kept/ keep two sailboats on a lift both were/are wing keels not sure how it would be in the case of fin keel. I would be happy to post a picture of my Beneteau on the lift if you would like to see.
Yes please!
 

p3dave

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Jun 18, 2020
6
Hunter 306 Pensacola
Thanks for all the responses so far, inherently I thought the keel needed to be supported but didn't know the reasoning behind it. Would love to see any pictures of your boats on lifts. I have seen a bunch on the net!
 

reworb

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Apr 22, 2011
234
Beneteau 311 Ft Myers Beach
Here's a couple of pictures I just took with my phone. Yeah I know I need bottom paint, I'm waiting till August when sailing is unbearable around here
 

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HMT2

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Mar 20, 2014
900
Hunter 31 828 Shoreacres, TX
So, it strikes me that if your boat is up on a lift and dry. Then you will need to use a different kind of bottom paint then you would if the boat was in the water all the time? Yes?
 

reworb

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Apr 22, 2011
234
Beneteau 311 Ft Myers Beach
Yes, there are basically two kinds, hard and ablative. For a boat that is going to dry out more than 72 hours you should use ablative.
 
Dec 25, 2000
5,909
Hunter Passage 42 Shelter Bay, WA
Our area has a hard storage marina for boats of all makes up to 36'. The marina uses a for and aft fork lift between the fin keel to move, launch and stow these boats without any issues as far as I know (no direct experience due to the larger size of our 42' boat.
 
Jun 8, 2004
10,376
-na -NA Anywhere USA
Having designed a few sailboat lifts, the keel which carry’s the weight needs to sit on a keel tray with supports to keep the boat upright. I have seen air tank style lifts as well. You need an experienced builder who has done a few with sailboats
 

p3dave

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Jun 18, 2020
6
Hunter 306 Pensacola
Here's a couple of pictures I just took with my phone. Yeah I know I need bottom paint, I'm waiting till August when sailing is unbearable around here
Thanks for the pictures and the advice about the bottom paint.
 
Jan 19, 2010
1,272
Catalina 34 Casco Bay
When afloat, your keel is dead weight and pulls against the flotation of the hull. The is zero support from the water to your keel. As long as the lift is rated for the weight of the boat and the hull is properly supported you should have no issues... But why couldn't you support the keel. A keel support that this to each bunk would bolster them against splaying.... You just need to establish a good reference system so that can repeatedly spot the boat in the desired location...
 
May 17, 2004
5,554
Beneteau Oceanis 37 Havre de Grace
When afloat, your keel is dead weight and pulls against the flotation of the hull. The is zero support from the water to your keel.
Like dlochner said above, the keel is pulling down in both cases, but in the case of the boat lift the weight is concentrated on the relatively small area of the lift supports. In the water the flotation distributes the force over the whole wetted surface area, and that’s how it’s designed to be.
 
Dec 28, 2015
1,897
Laser, Hunter H30 Cherubini Tacoma
I'd start with the spec weight of the lift and make sure it can handle the boat. Most scissor type lifts in my area have a 4k limit which you can find fairly regularly now for sale due to the newer boats (wakeboard/surfing) are needing larger lifts. A mechanical lift the size to lift a 10k boat would be significant. Through the manufacturers guidance, I upgraded my lift from 4k to 6k via bracing and trussing some components but my lift is galvanized steel and easy to alter. I needed a couple extra 1000 pounds capacity but not the step up in size. Unless it is a swing keel I can't image finding a regular lift (not make specifically for a sailboat) that would accommodate the keel due to the lifts cross members structures but I know there are out there.