Any tips on jacking up a boat?

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Grounder
Bottom Sanding Grunt
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Joined: Fri May 06, 2022 6:44 pm
Boat Name: Elaine Twain
Boat Type: Douglas 32

Any tips on jacking up a boat?

Post by Grounder »

What are your tips for safely lifting heavy boats?

I have a Douglas 32 with a displacement of about 11,500lbs. It's a bit out of trim, it's sitting on a concrete pad that's more rubble than concrete nowadays. It's tilting towards the bow a little bit. I wouldn't mind jacking it up so the waterline is nice and horizontal. I think the bow needs to come up about four inches.

The keel is on a three or four 6" wood blocks, and it's supported by six jackstands and a bowstand. I was thinking I could use a 20 ton bottle jack to shift it up a bit, adjusting the stands as I go, perhaps bearing on the cut-away forefoot and supporting the jack on a cribwork. I'd build the cribwork to bear perpendicularly on the keel.

One minor complication is there is a block directly under the lower pintle of the rudder - a giant chunky bronze fitting that is somehow bonded to the hull, not sure of how that connection goes. So if I jack up the bow, it puts a point load right on that fitting. And there would be a point load from the jack itself, not sure how to deal with that.
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atomvoyager
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Re: Any tips on jacking up a boat?

Post by atomvoyager »

Welcome to PCF. I'm assuming you don't have access to a travel lift or a gantry with strap for lifting the bow. I recently had to raise the bow on my 28' Triton which is close to 9,000lbs loaded. Mine is on a trailer with six side screw pads and one at the bow and I had no problem using a similar method to what you describe. In addition to the bottle jack under the cutaway forefoot a couple feet forward of the low part of the keel, I shared the lift load by stopping the jack jack every couple strokes and retightening the forward three screw pads while loosening the aft two. The center two were near the pivot point and only need a couple adjustments along the way. It will make the lift easier and less risk of crushing the fiberglass through point loading if you share the lifting load by placing a jackstand with screw pad under the V of the bow. If you don't have a V-shaped top on that screw pad you could attach some wood to it but I'm not sure if you might need to immobilize the pivot point. If that's not available then you can make your own with a second bottle jack under a 4x4 timber with V-shaped wood blocks screwed on top. It's a heavy lift with potential for the bow shifting side to side so check that the two forward side supports are placed under bulkheads and try to share the lifting load by sequentially tightening those four lifting points. The forward two or three jackstands are only going to provide a small amount of the lifting force but I wanted to spread the loads as much as possible and they at least help a little.

You need to pick the pivot point of the boat before lifting the bow. I'd be reluctant to lift it on its rudder shoe because you might over stress the fasteners or the fiberglass they attach to. If you can accept the aft part of the keel being lower than it is now, the easiest lift is to pivot the boat on a block as far forward under the keel as possible and confirm that it is not at some weak hollow portion of the keel. I didn't want the aft end of my keel dropping closer to the trailer keel board because I need clearance under it for working on the rudder shoe so I had the aft block just forward of the shoe. But if you have enough clearance there to pivot the boat at a point midway along the keel it means you shouldn't need a second bottle jack or extra jackstand. If you don't want the aft end of the keel coming down then use a block further aft. The center two jackstands should be near the pivot point so that you don't need to adjust them so often and they can provide sturdy side support during the lift. Or if you prefer to share the lift load with them then have them further forward and tension them frequently. The aft two will need to be frequently loosened slightly when lifting but keep them in place to provide some backup side support.

To use an existing keel block at the desired pivot point you need to remove any blocks aft of that by either slightly raising the aft end of the boat or somehow cutting or chopping it out. Maybe cut the block as small as possible with a sawzall and then cut the last bit out with a chisel.

Rather than checking the waterline, I poured water on deck to check for drainage through the scuppers so rain water won't puddle and checked a level on the bunk and cabin sole. Then I did the easier job of leveling it side to side by slightly loosening the upside screwpads while tightening the lower side. Aside from ensuring proper deck drainage, doing all this leveling makes installing equipment and modifying parts of the boat easier.

Having said all this, since I'm not there and I may have overlooked some detail, you should get an expert local advice and don't rely on my opinion alone. And if at property you don't own of course you need to consult with whoever is involved. Maybe someone else here has something to add?
CapnK
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Re: Any tips on jacking up a boat?

Post by CapnK »

Hi Grounder and welcome aboard! I think James covered it well, key point being taking the time to do it in small increments and "holistically", for lack of a better word. :)
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Grounder
Bottom Sanding Grunt
Posts: 3
Joined: Fri May 06, 2022 6:44 pm
Boat Name: Elaine Twain
Boat Type: Douglas 32

Re: Any tips on jacking up a boat?

Post by Grounder »

First, thanks a lot for welcome and I'd like to take the opportunity to thank you for your videos and input on this forum. Ever think of getting a little stencil of a sailboat? You could paint it on your bow every time you save a boat from the dump. Reverse kill count. Pretty sure you've earned one on behalf of my boat, anyway.

I like what you're talking about with the pivot point, makes perfect sense. I think I'll try to get that right under the most aft part of the ballast, any more aft than that is a void for the water tank. If I can get that in position, then I can take your advice about chipping out the block under the rudder shoe and that will allow the boat to pivot further forward.

The only hitch then is if the boat gets too low at the stern, the hydraulic trailer won't be able to pick it up too easily, I don't think. They need space to get the cross beams under the keel. I'm going to have to think about that.

I'm also investigating just getting the hydraulic trailer guy here but I'd rather spend the money on something for the boat, haha.

CapnK, I'll take it slow and steady for sure! I've moved a few boats here and there using the old stonehenge methods, but they were always smaller than this one, the consequences could be severe. No rush, that's for sure.
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