Jacking boat off trailer bunks

[Ixneigh]

Hi everyone. It this operation (the way I am undertaking it in these pictures) harming the boat? Ive done this once before but i only did it for a few hours. This paint needs an overnight dry.
I am going to be painting the boat yearly now. I would have liked to have the boat at a boatyard on stands, and then launched there after painting, but the yards are so busy with much larger boats these days, that they barely want to talk about my little MacGregor.
Doing this is workable for me, and the bottle jack doesn't require one to be Hercules. The cinder blocks will be replaced with a stand the next time, since they are heavy and there must be safer alternatives.

Thanks
Ix

[rsvpasap]

I have used bottle jacks with wood supports a couple of times with no problems. Harbor freight sells flat top jack stands that work particularly well.

[Ixneigh]

I need a few of those adjustable stands. Ill check around online or, the old Harbor Fright standby. There is one in the next town. Thanks.

Ix

[Russ]

This is good information. I have to admit, I have never cleaned the bottom where it touches the trailer bunks. Too difficult to reach. I may do this next time.

Obviously, warmer waters will be more conducive to growth. I imagine most boats in those places need an annual coat of antifoul.

I see a bit of corrosion on that aluminum trailer. Mine has it also. At what point should we be concerned?

[Ixneigh]

Re: trailer corrosion
It has white powder in most areas and a little very light pitting in some places. Its less of an issue where paint was spilled on the aluminum surface past. So I think I will just paint it when the boat is in the water, after lightly sanding it. Its not that difficult to lift the boat off the bunks, but arranging everything time. Rolling the boat over on the opposite bunks to do one side at a time is pretty easy and I used a much larger piece of wood for load spreading. Since this will be a yearly thing now, Ill try to perfect the operation.

Ix

[OverEasy]

Hi Ixneigh and Rsvpasap!

I missed this earlier….
The bunk block supports you came up with shouldn’t be a problem Ixneigh but if you’re gonna be doing this in a regular basis might I suggest that you take a bit of time and make a more conformal one?

I’m concerned that the bottle jack and wooden squares you are using could slip or shift catastrophically and result in potential injury or harm to you or your boat. Solely relying upon friction at an unstabilized single point loading column like a bottle Jack is precarious at best. Just a slight shift of the boat could have that suddenly popping free…. Just wouldn’t want you to get hurt.

I regularly clean and repaint the bottom and made up a stand out of pressure treated lumber that rests on the ground at the stern. (Photos below) It incorporates multiple 2x6 shims so I can adjust the height higher if needed for additional clearance such as to better fit the pressure washer wand and paint rollers. As the stand is at the stern I can easily complete that portion when I lower the boat back onto the trailer bunks.
To raise/lower the boat I use the teeter totter method using the tongue Jack, the stand and shim boards on the bunks.
First I securely chock the wheels on both sides front and rear so there is no chance for the trailer to roll.
I also use a capture pad block for the trailer Jack wheel so it can’t move in any direction.
The last thing I’d want is for the boat or trailer to wander about while I’m under it! (I might have been able to bench press the boat in my younger days but I’m not that young any more )

Once I’m sure that everything is secure I lower the tongue Jack all the way down which raises the stern. I sized the basic stand to just fit about a foot in under the stern at this point when on level ground. Please Note that the stand operates in compression, can’t spread apart and has a broad stable base.
Then I raise the tongue Jack to lift the bow up to the highest it can go. I place 2x6 shims on the now exposed trailer bunks to pretty much fill the gap (remember the stern is now resting on the ground stand).
Then I lower the trailer Jack all the way down again which again raises the stern up off the ground stand. I place additional 2x6 shims to fill the gap between the ground stand and the stern bottom. I repeat the process until at the clearance height desired when the boat is resting on the stern stand and bow.
This provides a good stable 3+ point supporting structure to safely work underneath the boat.

To lower the boat back onto the trailer I simply reverse the process.
This process always provides a good stable reliable support for the boat. This minimizes any chance or opportunities for things to inadvertently slip or shift position which could result in harm or injury to me or the boat.

The adjustable Jack stands like Rsvpasap pictured look to be physically capable of supporting the weight of the boat like the stands utilized in boat yards. But in a proper boat yard there are securement chains attached to the stands so that there is no possibility of the stand bases moving apart. Often there are additional chains provided that cross from the top portion of one stand to the base of the stand opposite to prohibit the top of the stand from possibly tilting outward. The narrower the base of the stand the higher the probability of the stand potentially tilting outwards due to the curvature of the hull. Additionally, Most boat yard stands are designed with wide bases, fixed attached pads and a tilt to one side which is faced toward the boat center. This is done to improve stability. Automotive type stands are straight up/down and are designed to only interface with a vehicles frame’s flat surfaces only in a purely vertical loading. Not angled loads which can potentially result in tipping or shifting laterally. Boards pinched on single points of contact such as the top pad of an automotive Jack stand has the potential to slip due to the lateral forces of a curved hull and/or cause the stand to tilt. Please be careful.

In my careers I’ve had the unfortunate opportunity to have witnessed many accidents and damage sites which could have been avoidable with proper planning. I just want everyone to have a long and healthy life especially if a potential incident could be avoided.

Best Regards,
Over Easy

[Ixneigh]

Hi Overeasy. Thanks for the detailed write up on that. That method had crossed my mind but I was concerned that supporting the boat only at the ends may cause the hull to go out of shape. If that is an unfounded worry, i will definitely make a back hull support and try that method.
Ix

[OverEasy]

Hi Ixneigh!

The hull is more than strong enough to support itself from the ends.
The curvature of the hull adds a tremendous amount of stiffness & strength.

Now that said, I’ve found that the boat is very stable with the system I use but I’d never allow anybody to go climbing on board while it’s up off the trailer. Not that it’s gonna break perse but it’s that a person moving about in/on the boat runs the real risk of making it unnecessarily unstable. (People do move about and can do so erratically… for a variety of reasons….a 180+ lb pinball comes to mind ) Why risk someone getting hurt? Like it or not Murphy’s Rules apply.

When I have the boat lifted up I do it so I can get a task done and then back down when the task is accomplished.
It goes back to plan the work and work the plan.
I double check that I’ve gotten anything I might need out of the boat before lifting the boat off.

I also respect that I’m not unbreakable … (I’ve broken me in the past ) … so I try to avoid getting any part of me inbetween the boat hull and any pinch point just in case… of say an earthquake anyone? (I’ve lived in a variety of places across the US and in just about every place there has been some level of earthquake has occurred that could be felt … )
A basic Mac26X or Mac26M weighs in at about 3000 lbs plus any extra stuff that has wandered aboard.
So why risk getting pinched (or worse) if something goes awry if I can avoid it?

Best Regards,
Over Easy

[Russ]

That is one impressive support bracket.

I've seen boats in yards on thin metal brackets that look so flimsy compared to that nice support.