Read at your own risk...

 So, it's been a while.  Lots of painting before this, but I'll fill in those posts as soon as I can get to them.

This one is more important and could actually have some info that's useful for us 5.80 guys and gals.

DISCLAIMER: This is a description of MY thought process and MY results.  Your results may vary.  Please don't copy my thoughts, designs, processes or mistakes without engaging your own brain and deciding if it will work for you.  I take no responsibility if your boat falls out of the sky into the water, onto the hard or onto someone's head.  I will disavow any knowledge of your sources or process if something bad happens.  This message will self destruct after reading.

I'm working on an internal lifting harness.  They're really nice to have, and my boat will be dry stored on a trailer in a yard.  Our club requires an internal lifting harness, conceivably because people do dumb stuff with slings.   These things include having the slings slide apart and off of the ends of the boat allowing the boat to fall out of the sky.  These things also include having the boat roll over, allowing the mast to tap someone on the head.  Boat yards use slings all the time, but they take a teeny amount of skill to use safely.  On the other hand, internal slings can be screwed up too.  As long as shackles are tightened and straps can support the weight of the boat, they work pretty well and are relatively fool-proof.  Of course, you make something fool proof and someone comes along and makes a better fool.  I try to not be that guy, but sometimes I screw up too.  This post is an effort to run the thought all the way through to the end to see if it works.  I did have a couple of other really smart guys take a look at my setup and see if I missed anything.  They didn't see anything, or they missed the same things I did.

My plan is to drill a couple of holes in the keel floor (#2 from the print, I think) that is the second back, the first one behind D'.  I plan to drill two holes longitudinally just outside of the existing keel bolts  and as low as possible.  I'll make some stainless straps (I couldn't find any shackles big enough) pass some straps though, pull the straps through the hatch right behind the mast, tie some lines somewhere from the stern of the boat to the lifting ring to keep the boat level, and lift away.

So, rather than drilling a bunch of holes in the keel floors and lifting the boat and having it fall out of the sky, destroying the boat and a year of work, I thought I'd try a test part.  I made a piece of white oak to the dimensions of the keel floor- 70mm tall, 60mm wide, length was about 600mm.  I had to laminate it.  Some of you will call BS (capitalized for your perceived emphasis) and that laminating will screw up the results because the one in the boat is not laminated.  Here's my reasoning.  First, I'm cheap.  I didn't want to buy a piece of wood big enough to cut it out of one solid piece.  This piece of really nice wood was in the "reduced" pile at my local hardwood store. Second, my biggest concern was having the wood split horizontally through the bolts and "lifting" the top of the keel floor off.  To minimize the effect of the epoxy, I put the joint vertically, perpendicular to the axis of the bolts.  This should have the least effect possible on the test.

Bow of the boat is up and to the right or down and to the left in the picture.  Gravity is in the standard direction.  I'm not a monster.
PS-I know that these boats are built in metric dimensions..  Sorry my dimensions are in inches.  If I can build a boat in metric, you can look at a picture in imperial..
PPS- Maybe I am a monster.

In the keel floor, I will coat the inside of the holes with epoxy (multiple coats) and then redrill them to make a snug fit.  This will spread the bolt load over the most possible area and provide a harder surface than the wood for the bolts to bear against.  I will also use real bolts (partially threaded grade 5 or better, or stainless steel), not the fully threaded grade 2 crap available at most convenient hardware stores.  

I really don't want to test this in the best possible situation.  I drilled the 1/2 inch/12.5mm holes with a simple twist drill.  This will tear at the grain more than a good wood drill (like a forstner bit or something else designed to cut wood) and make a weaker part by creating lots of places for cracks to start inside of the holes.  I used some fully threaded bolts and didn't epoxy the holes.  Like I said, I didn't want an ideal situation.  I want to be able to assume that my installation in the boat will be a better situation than the one I tested, and therefore stronger.

I drilled the holes for the lifting harness as close to the vertical keel bolts as I dared.  I didn't want the wood to crack and allow water in through the keel bolt holes and throughout the wood.  I also wanted the keel bolts, nuts and washers to provide some "squeezing" action to the wood to aid the wood in not splitting along the grain when lifting the boat.  This meant trying to leave some material between the lifting holes and the keel bolt holes but close enough to get some squeeze.  Arbitrarily, I chose 1" or 25mm.  With 1/2" holes, that leaves 1/2" between them.  I think that's enough.

The eye bolts on the bottom allowed me to tie some weight to the bottom of the thing.  The large washers on top of the oak simulate the square stainless steel washers that came with the stainless kit.  I probably should have made the stainless straps about an inch longer to avoid interference with the yellow lifting straps and the nuts on the eye bolts (nuts on the keel bolts on the boat).  These are about 2-3/4" bolt centers.  On the bottom, I wrapped the yellow strap around a bar that went through the lifting eyes on one side of a locomotive traction motor.  More on this in a bit.  But when I tried the lift with this arrangement, I got to 1071kg before the traction motor started lifting.  I don't (er, didn't) know what the traction motor weighs, but when I lift it with our 6000lb forklift, it helps to have a person sit on the back of the forklift to keep the rear wheels on the ground.

Assuming that the boat will weigh about 1130kg loaded, this won't be enough to be sure that my lifting solution will work.  So, I had to rearrange the lifting straps on the traction motor to lift a larger percentage of it.  Then I got the picture below...

So, I lifted it again until the traction motor came off of the ground.  I didn't see if it came completely off of the ground (I suspect it didn't).  On the other hand, the forklift kept working (hydraulic motor spinning), but the load cell stopped increasing in load.  So, the forklift maxxed out at 2949kg and/or the traction motor lifted off the ground as much as it was going to.

To make a long story longer, the load was 2949 kg (6487 lb) on a 6000 lb forklift with a 3000 kg load cell.  I didn't feel the need to get loaded up to the max on the load cell since the max wasn't much more than what I measured.  As it is, with a ~1200 kg boat (loaded, roughly, as a final guess), our final load of 2949 kg gives a factor of safety of about 2.5, which is a little thin for lifting things in general.  To compare, the factor of safety on aircraft is generally and roughly 1.5.  On the other hand, there weren't any bad sounds that came from the piece of oak, and the post testing inspections showed no ill effects on the oak.  So, at 2949 kg, there's clearly some excess capacity to carry more load, but I just don't know how much.

As Mythbusters taught us, we like to test the theory to the limits of the theory (can it lift a boat), then we like to see what it would take to create the catastrophic failure (how heavy would the boat have to be to cause the oak to fail?).  As it is, I don't have a forklift to lift more than 2949 kg, and I don't have a way to resist a load more than 2949 kg and I don't have a load cell to measure more than 3000 kg.  For now, I'm satisfied knowing that the minimum factor of safety we have for a 1200 kg boat is about 2.5.  If I have a chance to test my test parcel to failure with a load cell, I'll do it and report back.  Until then, lift safely and build smart.

5...4...3...Boom.

See? Some village is missing their idiot...  But they're not missing me much.