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I would like to do my own bottom painting also. I have a couple of Ideas I modeled in Google Sketch-up using 4x4's, 4x2's and a 4x6 in view 1. Replacing some of the 4x4's in option 2 with automotive stands. The jacks were downloaded from the Sketch-up warehouse.

I'm trying to save a boat buck by doing myself but it makes me really me nervous.

Bluecrab wrote:I would like to do my own bottom painting also. I have a couple of Ideas I modeled in Google Sketch-up using 4x4's, 4x2's and a 4x6 in view 1. Replacing some of the 4x4's in option 2 with automotive stands. The jacks were downloaded from the Sketch-up warehouse.

I'm trying to save a boat buck by doing myself but it makes me really me nervous.

I would be real nervous with option 2 (jack stands). I feel the tops are to narrow and could just be a pivot point. If I used them, and I wouldn't I'd make darn sure the boat can't move fore/aft resulting in the crosspiece coming off of them possibly.

If you used two jack stands one in front of the other on each side with a piece of heavy steel square tubing between them and the crosspiece on top of the square tubing I'd feel pretty comfortable. The jack-stands should almost be touching each other. I wouldn't want to use the jack stands on anything but a hard surface (concrete/asphalt) though.

Option #1 looks the best and the most proven, but make sure the 4 X 4's are good wood.

Good luck and be very careful,

Sum

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Sumner wrote:
I would be real nervous with option 2 (jack stands). I feel the tops are to narrow and could just be a pivot point. If I used them, and I wouldn't I'd make darn sure the boat can't move fore/aft resulting in the crosspiece coming off of them possibly.

Thanks for the response. I agree, I modeled it to see what it would look like because axle jacks had been mention in and earlier post (see below).

AJ wrote:2. Insert two axle stands chocked with timber to protect the hull and lower jack so that the stands take the boats weight.

.

Wally

Well last year I trialled Lanolin grease but the boat wasn't in the water for more than 6 weeks at a time, there wasn't a lot of build up compared to other years and we were in more tropical waters but the best part was when we got home I just spent an hour or so with the pressure washer and it was clean or near enough with just a hint of grease.
It probably would have been better still if I had hit it immediately after pulling out of the water will certainly be spending half an hour rolling on the grease again this year.
Only problem I encountered was the grease collected a bit of dust when moving prior to it going hard.

Bluecrab-
I agree on option #1. 6X or 8X blocking timbers are desireable & managable, but I've used solid concrete blocks to support the boat while working on the trailer. This block configuration was stable enough for me to be on the boat as well, but if I were to spend any time under the boat, the blocks would be cribbed for stability in any direction.


Carefully done, automotive jackstands would work, but for that route, I'd prefer & reccomend Brownell Boat Stands. Maybe a local boatyard or equipment rental shop would have some proper boatstands to rent.

Re the axle stand option: I used squares of scrap 25 mm ply about a foot square each between the axle stands and hull (making them much like a small Brownell stand), with the stands about 700 mm apart on the flat surface at the stern. Personally I 'd prefer to rely on a properly engineered stand than something my limited carpentry skills could knock up, but others may differ. Agree that you need to do this on a firm surface. Also I would not do this without having either the bow or stern sitting on the trailer at any time, with the wheels chocked. The boat felt solid using this method.

Cheers,

AJ

So OK you get the boat on the stands but how do you get the trailer out and besides for painting you then have stands to paint around instead of a trailer?

Boblee wrote:So OK you get the boat on the stands but how do you get the trailer out...

Archived thread link:
http://www.macgregorsailors.com/forum/v ... ks#p124201

K9Kampers wrote:I believe the process has been described here before, but it's a simple tho time consuming process, a couple of hours to half a day, depending on your energy level.

Use a rolling floor jack, solid blocks (wood or concrete), 2x & plywood shims.

Park the trailer tires on 2x pads. Crank down the tongue of the trailer as far as you can. Block the transom of the boat, raise the tongue enough to block it, then retract the jack & place a block under the jack foot/wheel. Jack up the tongue as high as possible. Block the bow of the boat. Lower the trailer to level.

By now, there should be enough clearance between the boat & trailer to move the trailer. It may be necessary to remove the 2x pads from under the tires to gain more clearance. Now the work begins...

The rest of the task is a process of moving the trailer forward to the bow blocking, then block again behind the trailer's cossmember/axle, then remove the forward blocking. Continue the process, moving the trailer ahead until it clears the boat. Add blocking to make four points of contact.


Reverse the process to put the trailer back under the boat.

In every step of the process, BE CAREFUL and think about what you are doing.

Boblee wrote:... for painting you then have stands to paint around instead of a trailer?

Paint what is accessible, let dry, then place new blocks before removing original blocks to paint the rest of the hull.

Concrete blocks are not suitable for this, solid or otherwise. The failure mode for blocks is catastrophic collapse, aka, crumble. If you are underneath when this happens, you are SOL. You are much safer with wood blocks which dont crumble in failure.

You certainly have enough blocks under there to have a hefty safety margin in tensile strength so Im not saying you were flirting with death - in particular, if you bought new blocks and used them for this purpose, you would be ok as configured. However, a year from now, especially if these blocks are left outside in the weather, how much of the safety margin remains ? Hard to answer. Safety questions which are hard to answer are often the beginning of the cascade of events that lead to accidents.

You can use the trailer itself as a jack, to transfer the boat to blocks where the support is in a different place than the bunks. Then after painting the boat bottom everywhere but the supports, lower the boat back onto the trailer and finish the places where the supports were.

First lower the front of the trailer as far as it can go. I removed the wheel and put a solid plate on the jack to let it get lower. PLace concrete blocks under the rear of the boat almost at the transom, and as far apart as possible still under the almost flat bottom. I was able to put two concrete blocks side-by-side, and a third on top to make a really stable support for each side of the hull. Top off the concrete blocks piers with a wooden pad of square-cut pieces of 2X8, or 2X12 to spread the load. Made the supports at the back as high as possible under the boat.

Then at the bow, start raising the trailer with its own jack, and in a few inches, the stern of the boat will begin to rest on the rear supports you made. The concrete block pyramids will hold the rear as the trailer pivots on its axle. When the nose of the boat is raised as high as your trailer jack can go, make a stack of blocks under the trailer where the A frame and cross members meet the tongue, as high as possible. Then lower the trailer onto this block stack, and keep retracting the trailer jack until you have it all the way up. Then build another stack of blocks under the jack, and start jacking the nose again. When you have the nose just a tad higher than the stern, build a block stack under the front of the boat, just in front of the centerboard slot, and behind the trailer bunks, a single center support for the front. The boat has a moderate V shape there, and I used a very dense PVC foam block that would only compress a little, to take the boat's weight and conform to the shape a bit. You could just cut a block of wood slightly V shaped to do the same. Then lower the boat jack until the boat rests on the front block stack, and the boat is completely off the trailer, by several inches at all points. You can make more space between the bunks and the boat by raising or lowering the front and back of the trailer, without touching the boat. The trailer is trapped under the boat by the block stacks, but you could move it a few inches forward and back without disturbing the blocks that hold up the boat.

After painting the bottom, except for the three blocking points, reverse the procedure for putting the boat back onto the trailer, by first lowering the jack, and continueing the reversal process until the boat is back on the trailer. Then the stern can be painted easily, as it sticks way past the last bunk, and the one spot in the front behind the front bunk, as well.

I found the boat to be very stable when under the three points of support, and went aboard several times, moving about freely with no rocking or any sort of motion. By leaving the trailer under the boat, you always have a safety margin when working under. You do not have to launch the boat to change the support points.


very stable, no rocking, notice load spread by plywood or flat boards on top of concrete blocks





The standard wheel can be re-installed easily, but I prefer the flat plate adapted to fit under the jack post, instead of the wheel.
It spreads load better, and seems to be more secure, especially if you want the trailer to stay in place. Also avoids flattening the wheel if inadvertently left down with all that weight. It is held on by the same pin, and raises higher to allow the trailer to go lower in front.
(That allows the rear to lift higher)

The blocks stacked this way are not going to collapse or crumble.



The clearance between the bunks and the boat is adjusted by tilting the trailer back and forth on its axle. Of course when the maximum clearance is made in front, the rear is toucning, and visa-versa. By using the trailer's own jack, it's no problem. There is enough room to use a orbit sander and paint roller, everywhere but the fenders area.

ALX357 wrote:You can use the trailer itself as a jack, to transfer the boat to blocks where the support is in a different place than the bunks. Then after painting the boat bottom everywhere but the supports, lower the boat back onto the trailer and finish the places where the supports were.
Then at the bow, start raising the trailer with its own jack, and in a few inches, the stern of the boat will begin to rest on the rear supports you made.

I would not do that if I were you!!
That nose or tongue wheel was not made to support that much weight, trust me. I learned the hard way. I tried exactly that, and bent the bejesus out of the wheel frame. Yes, it looks like solid steel and cannot be bent, but it does bend, even the replacement wheel I bought bent too, I ruined two wheels, took me twice to learn my lesson. Use a 2 ton car jack to hoist the front end of that trailer up and save yourself the grief of crunched wheel housing.

One advantage you and guys have over some of us is that flat hull in the back makes thing somewhat easier .

Put me on the "don't use concrete or cinder block" list . Your life is worth buying some wood blocking even if it takes you an extra day to get some before starting the job.

c ya,

Sum

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The nose wheel has been replaced by a flat plate. You need to look at the photo.

The concrete blocks are stacked so the web is vertical.

The trailer is still under the boat.

I am a carpenter, and understand the forces at work.