lifting boat w/out jack stands

[passagesfromtheheart]

I watched a video of a sailor, who has a Mariner 19, do a fiberglass repair on the bottom of his boat's hull. To access the underside of the boat, he dropped one bunk on the trailer and then, on the same side in which he dropped the trailer bunk, he propped a piece of wood planking/board (2x6) under the rub rail and then secured the opposite end of the board to the ground (grass). I don't have jack stands to prop up my boat (a Legacy) and wondered about using the technique noted above. Thoughts? My boat is on gravel, not grass, too. I need to access the underside of my boat, temporarily, to work on it and so am looking for alternative options to buying jack stands.

[crazycarl]

I have done this. However I wasn't about to crawl under the boat without reassurance.

1st I used a heavy duty ratchet strap. Securing 1 hook on the to the rub rail, the strap across the top of the boat and the other end of the strap hooked to the trailer. Then I made a bracket that the trailer tires rolled onto to keep the brace from sliding out. Picture a large letter "A" on its side with one leg longer than the other. The angle was about 2* with a brace (the A's horizontal line) on each side of the legs.

[fried fish]

Safety first....
I have a 23 that I have left on the trailer while using hydraulic bottle jacks to elevate the bow first and then same on stern.
Adding 2x blocks as I went, all sitting on the center of trailer. Also adding blocks a couple of points between the bunks and hull.
My purpose was to repaint the bottom. Ultimately I got 5-7" clearance.
My bunks would not have dropped due to being a crusty salt water trailer.
I have used jacks before that I borrowed from a marina. It was easier working with the blocks. There you have it.

[Amedaius]

I'd check around your area and see if there are sources to rent or borrow equipment. Quite often you can rent such things from big box or automotive stores.

[bruce]

Long post from 2018, but it may be helpful. The PC with gear displaces about 800 lbs. SailboatData lists the Legacy displacement as 1,000 lbs. Pardon the photos!


Our trailer gets rinsed after every launch, but there is rust from the saltwater that needs attention.  The boat lives in the garage, and I wanted to leave it there while the trailer was out for service. The low overhead above the boat makes lifting from above problematic. As much as I've always wanted an excuse to get an aluminum gantry, this wasn't the time.

I only need to raise the boat about 6" to be able to slide the trailer out. The tongue jack tilts the trailer effectively, pivoting on the axle. From stop to stop, vertical travel at the stern is about 4". At the bow it's about 7". The plan was to run the tongue jack all the way down, block the stern in its raised position, and raise the tongue jack dropping the trailer away from the stern as the bow was raised. The bow would be hung from a beam, and the tongue jack cranked back down to a neutral position so the trailer could be pulled out.

In summary, the technique worked but I found it easiest to use some supplemental lifting to get the needed clearance. A lengthy description of my set up follows, please read on if you're interested.

I had thought of building stands to support the stern that would key onto the deck flange at the corners, but fitting the bearing surfaces to the flange to distribute the load was going to be fussy work, and the stands would have to have broad bases, or be effectively braced, to prevent tipping. If I was painting the bottom, it might be worth the effort, but I already had a low sawhorse I'd made that, fitted with a jig that conformed to the hull, worked just fine. The top of the jig was lined with 1/8" rubber mat to protect the hull and minimize slipping. The bottom of the hull is a shallow V with flat areas on either side at the transom. A couple of low Brownell-type boat stands would also work well.

Forward, the supports for the beam had to be spaced far enough apart for the trailer to clear. We have side bunks, so the trailer is about as wide as the boat, 6' 6". A 8' beam might work, but 10' gave more flexibility. The 4x4 I had was fine. Again, I had thought of fitting a jig to the deck flange at the bow to hang from the beam, but opted instead to use a sling aft of the shrouds. (I wouldn't feel comfortable cross loading the bow eye from above.) There was sufficient room between the coaming and the boom for the beam and the vertical clearance needed for adjustments. At least for this preliminary testing of the concept, I planned on using stepladders I had on hand for supports. Most ladders seem to space the threads about 12" vertically, the fifth step on the ladders I used were both at about 60", a couple of inches above the coaming. One of the ladders I used was a sturdy type 1A, rated for 300 lbs., the other was a lightweight household model rated at 225 lbs. Although I had my doubts about the lightweight ladder, both ladders seemed adequate.

I had  several gelcoat-friendly polyester lifting slings to chose from, and I tried several combinations of slings and shims under the beam ends to tighten the sling before lowering the tongue jack. I could get the boat hanging from the beam, but not enough to clear all of the rollers and bunks completely. There was too much settling and stretch in the system. Another issue was I was lifting back at the shrouds and not the bow. At the shrouds, I later determined, the vertical travel from the range of the tongue jack was only 3".

To supplement the lifting of the tongue jack, I tried various combinations of the three hoist/pullers I had, between the beam and sling. Ideally, I'd have a hoist on both ends of the sling, so I could lift on both sides at the same time and the sling would not need adjust under the hull. Lifting on just one side would cause a turning moment on the hull, unless the sling slipped sideways, which would be less likely as the load increased. Fortunately, we're only talking a couple of inches vertically, so any turning moment would be minimal. To keep the hoists away from the hull, I clamped a 6' 2x4 on top of the beam as a spreader.

I didn't investigate using a floor jack to lift on the keel while resetting the boat higher in the sling. If the blocking at the stern is wide enough, so the boat doesn't tilt readily, this could work. I would install blocking under the keel if the boat was to be kept off the trailer for a while. If work on the hull once the trailer is removed is planned, suitable additional support will be needed.