Craning the swap over

[Jimmyt]

Oh Ok... I didn't realize the folks would go that high.
Now I understand

Depends on the loader, but some will go much higher than needed to swap trailers. Seems like Tom's suggestion of the wrecker might be cheaper than a loader (unless you have a buddy that owns one), though.

[Neo]

Just use a short spreader and sling it under the bow, but close to the bow you don’t really need a spreader at all (IMO) since it’s so narrow. With the stern blocked in a wooden cradle, close to the trailer or where the new trailer tail end will be, it will be very stable against roll. Then just lift the bow.
That boat is light, especially at the bow, and especially with the stern support as far forward as practical. But, get it all set up, and be able to tell them what the lifted load is and how far from the path of the trailer fenders the hook will be, which is at least 4 ft....

Ok Tom I've found a small mobile crane-truck in an industrial park not far from me. I spoke to the guy there and he's happy to do the lift for 2 crates of beer!!
It's not all plain sailing though because the site will be quite difficult to manoeuvre around and it looks like I'll have to reverse the Mac a couple of hundred meters up their lane-way.
So I've bushed the dust off of the wooden frame I knocked up a few years ago and we're going to lift just the bow with the frame firmly secured (and braced) under the stern.

So my big question now is (on a ) where would be the best place to pass the crane sling around the hull?
Where the hatch is?... or just behind the hatch? ... or further back?
Obviously the further forward the easier the lift will be but the more chance of the sling slipping or the frame falling over.
The further back the more pressure is on the sides of the hull (in case we don't have a spreader) .... In this case would it be a good idea to use "Sausage shaped fenders" to keep the sling off of the bumper line?

And yesterday I did the trick of placing the drawbar in the ground then putting my frame under the stern, then bringing the drawbar back up again. My Mac came off both its stern and mid bunks and was resting on just the bow bunk and the frame. Yes the belly is still in the dam way ... but I reckon a lift height of just 2 or 300mm (15") should be enough to pull the trailer out from underneath.

These are old photos from my previous trailer swap attempt ...

[Tomfoolery]

So my big question now is (on a ) where would be the best place to pass the crane sling around the hull?
Where the hatch is?... or just behind the hatch? ... or further back?
Obviously the further forward the easier the lift will be but the more chance of the sling slipping or the frame falling over.
The further back the more pressure is on the sides of the hull (in case we don't have a spreader) .... In this case would it be a good idea to use "Sausage shaped fenders" to keep the sling off of the bumper line?

I would not use any fenders at all, if it were me. That will widen the spread, increasing the compression through the deck, and put that side loading into the thin part of the hull, just below the joint. That joint is pretty strong, so I would just let the rub rail do its thing.

I would put the sling as far forward as is reasonable, remembering that the sling has to come up past, or inside of, the bow rail. Put a preventer on the sling, one on each side, back to the winch or some other strong point, like the stern dock line cleats. See the sketch. You can even bend the sling back a bit with the preventer (red line), so the bottom of the sling is flat on the hull edge up near the bow and the two sides are perpendicular to the point of contact at the bottom.

I don't know what the M weighs, but the X is only 2350 lb without OB (as published), and with the OB at or behind the stern support, it doesn't count (or lightens the bow a little even). So even if it is 3500 lb with OB, and with the CG of the boat just forward of the front of the cockpit (where the X CG is), you're only lifting half that or less. The further forward the slings are, and the further forward the stern support is, the less you'll be lifting. Eyeball estimate suggests maybe a third of the weight, in fact.

Also, the longer the slings are, the smaller the angle between them, and the lower the squeezing force on the deck.

Here's some random 26M in profile I found online that I butchered with rigging sketches.



Oh, and I would move that stern support further forward if it won't interfere with the new trailer.

[Neo]

I would not use any fenders at all, if it were me. That will widen the spread, increasing the compression through the deck, and put that side loading into the thin part of the hull, just below the joint.

Understood and thanks for your thoughts on that.

I would put the sling as far forward as is reasonable, remembering that the sling has to come up past, or inside of, the bow rail. Put a preventer on the sling, one on each side, back to the winch or some other strong point, like the stern dock line cleats.

Perfect .... The preventer is an awesome idea... and really addresses my big concern about the sling slipping out.

I don't know what the M weighs....

My all up weight (without the trailer) is 1,835Kgs - 4045lbs

Oh, and I would move that stern support further forward if it won't interfere with the new trailer.

Yep will do.

Thanks so much Tom

[svscott]

Here's how I changed trailers on my D.

I built and diagonal braced a very solid stern cradle, using 2x8 scrap wood with Styrofoam floor underlayment as cushion between the wood and hull. I placed the stern cradle directly under the forward wall of the lazarette at the back of the cockpit bench.

For lifting the bow, I purchased (3) 10' long 6"x6"posts and a box of 5" Fasten Master "lag bolts" to screw the structure together using random scraps of wood I had on hand. I then used (2) Harbor Freight chain hoists and a 20' strap doubled back on itself between the hooks of the chain hoists and lifted each side a bit at a time. The D has a plywood bulkhead at the forward wall of the head so that's where I located the lifting straps. I used (4) pieces of 48" long rebar pounded into the ground about 36" deep to tie off guy lines to the top of the wooden lift structure.

I am not familiar with working on the M but I'd guess that putting the straps under the forward hatch would work just fine.

EDIT: doing the swap this way enabled me to easily get the old trailer out and the new trailer under. I placed 2x10 wood blocks under the trailer tires to get the trailer as tight to the hull as possible without touching the axle crossbar. Then I slowly lowered the boat and positioned the trailer exactly where I needed it for proper fit at the bow V. Lastly, I was able to fit, shim, and fasten the 2x6 bunks under the boat at the correct angle.

[Neo]

Here's how I changed trailers on my D.

Thanks Svscott .... That looks like an awesome project.
I've considered doing something simular but I guess after all the work I've done on the trailer I'm kinda getting tired of all the fabrication work. But from a longer-term prospective I like your method because ....
# I'd be able to take my Mac off the trailer for easy hull or trailer maintenance.
# I could build another one or two frames and turn the whole thing into a Boat Garage.

But in all honesty, after recently buying the trailer I just can't justify more expense on a yacht that I've spent far more time working on than I've done sailing!

[Tomfoolery]

That’s exactly what I suggested in my first post in this thread (wooden gantry), but if you can hire a crane for the cost of a couple of cases of beer, you’ll be way ahead from a cost perspective. But one big advantage of the gantry is that you can use it again for free, like for bottom painting, since it’s already paid for.

[Neo]

Sorry Tom, I didn't know what a wooden gantry was ... and I forgot to Google it!

Actually I'm looking into this now because there's a couple of spots at my place where building a gantry might be easier than I 1st thought.

[svscott]

I don't keep my hoist permanently assembled but if I wanted to do that, I'd be inclined to buy 14' posts and cement them in the ground. As soon as I was done with mine, I took it apart and stored the wood on my old steel boat trailer along with a bunch of other scrap building lumber. If needed, I can rebuild and stand the whole thing in less than 2 hours with one helper.

[Neo]

If needed, I can rebuild and stand the whole thing in less than 2 hours ....

Gosh! ... Fancy a trip to Australia
Thanks svscott

[svscott]

If needed, I can rebuild and stand the whole thing in less than 2 hours ....

Gosh! ... Fancy a trip to Australia
Thanks svscott

Neo, you have no idea! I've never visited but if the logistics and cost of living were better, we fancy a move to Australia. My wife has brought up this topic more than once. She has a friend who relocated there several years ago, working for General Electric.

[Tomfoolery]

Actually I'm looking into this now because there's a couple of spots at my place where building a gantry might be easier than I 1st thought.

Depending on the ability to anchoring guy lines, the gantry can be as simple as an inverted U. No corner bracing needed, IF you can guy it side-to-side (looking from the bow of the boat). Technically, fore/aft guys aren’t needed when the boat is supported by it, as it’s self-stabilizing in that direction as long as the stern is solidly in a cradle (like you’re planning), but some sort of stabilizing of the gantry is needed when there is no load on it.

Like the small diagonal corner braces in the photos above. Or guy lines. Or use two legs on each side, bolted together like scissors with a small tension member (or rope) between them near the bottom so they can’t spread. If the chain hoists are anchored where the vertical legs are, then there is only some small compression load in the top cross member and it doesn’t have to be very big (or strong). There also won’t be any compression load through the deck, as if the slings aren’t bending over the rub rail, they won’t be squeezing it.

If the hoists are hung off that cross member at any distance from the legs, then it has to be sized for some bending moment where the hoists are supported. If the hoists are vertical, then there’s no compression in the cross member.

[Neo]

Thanks Tom,

Turns out we are in a heatwave for the next few days. So unless I want to get cooked I'll have to put this project off to another time and go with the crane lift on Thursday.
Fingers crossed

[Neo]

Jobs done ... a day early..... It was drizzling this morning and the revised forecast showed rain for tomorrow. So I rang the crane guy and said "how about today" and he said "yep lets do it!"

Setup ...



The jockey wheel broke .. But the forklift came to my rescue



Pulled out the old trailer... And she's floating on air!!



Then in with the new trailer... and down she goes to rest.



My thanks to all ... but especially Tom ... not sure if I would have attempted all this without your great advice.
I've yet to measure the tongue weight Tom (will come back with that) but I could see it was putting fair load on my cars tow ball.

[Tomfoolery]

Glad it worked for you.