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Boat on trailer, trailer on jackstands on plywood, for trailer repairs


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Before my boat can move, I need to fix the trailer. It's sitting on grass that can be wet and soft. 

The plan is to put it on jackstands, one under each rear corner, another under the tongue. (Should I use more?) Then I need to put the jackstands on something, to keep them from sinking in.

So, 2'x2' squares of 1" plywood (sealed somehow), or concrete pavers (are they strong enough)? Something else?

Is this unsafe? The trailer frame is ~2' narrower than the wheels, and the whole thing will sit a few inches higher. It may sit like this a few months, with me climbing around on it occasionally.

Boat is probably 5k LB, trailer another 2k. 

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When I have the boat sitting at home for any length of time, I always block up the trailer - don't want 10,000 lbs on the tires and suspension all the time and want the boat level to work on.  But then again, it doesn't go any place "soft" in the first place.   

Concrete blocks can work - they can also split if they aren't loaded flat and square.  Think pressure-treated timbers.  

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Jackstands on wood is a common occurrence at the Snubber workshop.  I have placed jackstands on solid concrete pavers but that makes me nervous. Never on a hollow cinderblock/breeze block.  For prolonged ground contact, might screw plywood squares to a base of pressure treated lumber (You wouldn't need 2x6s as a base; 2x4s screwed side-to-side with plywood top would work). Ensure jackstands are rated for the weight, and haven't been recalled. There was a batch of recalled jackstands (a few years ago) that would drop when jostled. I saw it on the Youtubes.

Snubs

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I'd be surprised if your trailer was anywhere near a ton, maybe half to 3/4 of that.

As for concrete pavers it would depend on what type, I have some 2ft square slabs 3 inches thick, they could easily take the weight. I also have some 18inch square 1inch slabs they wouldn't..

Personally I'm not fond of jack stands, I'd jack up each corner and place a stack of concrete blocks under each corner of the trailer, they'd act as the load spreaders as well. As long as your boat and trailer is stable you don't normally need it to be perfectly level.

Note, I mean, 18inch by 9 inch blocks, 4 inches thick laid on their side. 

Time to finish my coffee, then out to put bearings on my trailer.. supported by 4 concrete blocks in each corner. My trailer has ten inch wheels so that's enough, you might need five or six....

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The pavers I'm thinking about are the 2'x2' ones from Lowes, probably ~3" thick. I'm concerned about point loads from jackstands. ???

I would never use hollow concrete blocks, though plenty of boats are on them.

I may be able to find blocks of wood, also some 2x8 pressure treated. Will explore a friend's junk pile!

Thx

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15 minutes ago, blurocketsmate said:

The pavers I'm thinking about are the 2'x2' ones from Lowes, probably ~3" thick. I'm concerned about point loads from jackstands. ???

I would never use hollow concrete blocks, though plenty of boats are on them.

I may be able to find blocks of wood, also some 2x8 pressure treated. Will explore a friend's junk pile!

Thx

I share your concern about the point loads of metal on concrete. The pavers you describe, with the plywood laid on top, would be a safer bet. Should be fine. 

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Jack stands will go right through those pavers unless you prep the ground. Compact 2" crushed rock. 

Might consider a crib of 4x4 PT on the pavers to spread the load. Jack the corner up build a crib and set back down. You can use shims to set level at each corner. 

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I would cut up 2 by 10 2 or 3 feet long and use them as supports.  Pavers can break.  Use 4 or 5 supports.  Back 2 corners and 2 on the front corners and 1 on the tongue.  I have done that and then dropped the axel to replace the springs.  

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Cribbing as per Deks.

Never, ever, ever jack up weight on unreinforced concrete of any kind.

And more than 3 points - that is inherently unstable.

 

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^^^  Perusing the options at home stores, I was already leaning toward PT, no pavers. I think there's a pile of old 4x4 fence posts I can use. If not I'll buy some 2x10 that I was looking at. Thanks all!

 

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On 4/1/2021 at 1:39 PM, blurocketsmate said:

Before my boat can move, I need to fix the trailer. It's sitting on grass that can be wet and soft. 

The plan is to put it on jackstands, one under each rear corner, another under the tongue. (Should I use more?) Then I need to put the jackstands on something, to keep them from sinking in.

So, 2'x2' squares of 1" plywood (sealed somehow), or concrete pavers (are they strong enough)? Something else?

Is this unsafe? The trailer frame is ~2' narrower than the wheels, and the whole thing will sit a few inches higher. It may sit like this a few months, with me climbing around on it occasionally.

Boat is probably 5k LB, trailer another 2k. 

Most trailers are not strong enough for this. You must support near the center of the trailer. If placed just at the rear and at the tongue the unsupported section is too long and you can damage the trailer.

 

JJ

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I make cribs out of scrap 2x4 pieces for this sort of thing.  They are easy to nail or screw together, making a very stable base, and can be built as high as necessary.

As mentioned upthread, you want to support the trailer frame mainly near the axles, rather than at the corners.  Depending on the repairs you have in mind, you could perhaps support the springs where they attach to the axles, which would reduce the amount of loft you need.

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