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Alan H

putting in a keel lifting point

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After mulling over some options, I think I'm down to the point of needing to sink a couple of J or L-shaped stainless steel bolts into a ton of lead so that I can pick it up on a hoist. There's 2100 pounds of lead in a 3600 pound boat...that's the load we're talking about here.

Gut feeling is that drilling four 12-inch holes, tapping 'em, and cranking a couple of bolts in there might not cut it.  I suppose that I might drill a pretty good hole, pour epoxy into it and then use an industrial-strength s.s. expander - wedge anchor like this https://www.grainger.com/product/DEWALT-ENGINEERED-BY-POWERS-10-Stainless-Steel-Expansion-448L72

or this:  https://www.fastenal.com/products/details/2140569

but I dunno if four of those is gonna hold 3600 pounds.   That''s 900 pounds each straight-line withdrawal force and God Forbid that the hoist goes *bump* and loads it to half again that for a second.   But WTF do I know?   Hey Wise Engineer folks, what do you think?  This is ONLY for lifting the boat with a hoist, the lead is internal inside the hull..

HOWEVER..there's this:

http://catalog.fmstainless.com/viewitems/expansion-anchors/stainless-steel-sleeve-anchors-hex-nut-

 

Which basically is a chart for s.s. sleeve anchors set into 4000 PSI concrete. How that compares to lead???

http://catalog.fmstainless.com/viewitems/expansion-anchors/stainless-steel-sleeve-anchors-hex-nut-

I'd think that concrete wasn't anywhere near as "crumblyproof" as lead. However, according to that chart and 3/8 x 4 set in concrete should hold well over 3,000 pounds. If I went up to 5/8 x 4.25, and set two of them into the lead...if lead was the same strength as concrete, then  that would be 18,000 pound "strength" whatever that means. I think that's a safe margin for a 3600 pound boat.

 

My gut feeling is still that the expanding bolts ain't gonna work.  It's cause I don't know shit so I'm a'skeered.   THAT means somehow sinking 2 to 4 , 1/2" or 5/8"  304 s.s.  L-shaped anchor bolts into the lead.  I can think of two ways to do this...heat the bolts to "damn hot" but not hot enough to mess with the temper and slowly press them into the lead.  The other way is to drill/cut, melt..whatever a deep groove into the lead and shove the bolts in there. Then heat the whole area with a torch and pour hot lead in over the base of the bolt, leaving about 2 inches standing proud.

Talk to me, oh cognoscenti.

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Can you use the existing keel bolts / add a nut or put a fitting under the existing nuts?  Maybe machine a large backing plate with fittings on it?

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There are no keel bolts in this boat. The keel isn't "bolt on".  It's an Old Skool full-keel boat.  Here's a pic of a sistership hull

 

04310_image_extra_2.jpg

 

I've done a little reading.  Withdrawal force needed to yank two identical bolts out of different materials depends on the tensile strength and shear strength of the material into which the bolt is embedded. So...question is, what's the tensile and shear strength of lead, compared to concrete, since the bolts I'm talking about are designed for concrete?  Looks like concrete shear strength is 6 - 17 MPa, whatever "MPa"  is.  Tensile strength is 2 - 5 MPa...also expressed as  300-700 psi

https://www.engineeringtoolbox.com/concrete-properties-d_1223.html

OK, cool...how about lead?  - https://www.ila-lead.org/UserFiles/File/factbook/chapter2.pdf

Pure lead tensile strength is 12 - 17 MPa.  It's about 1/6th of aluminum.  The range overlaps that of concrete.  However, even a 1% addition of antimony pushed the tensile strength to 23-25 MPa.

So in other words, while lead "creeps" and concrete doesn't (much) and while concrete is killer strong in compression, in terms of tensile strength and shear strength, lead is stronger than concrete. SO..in theory, a s.s anchor bolt set into lead should in fact grip BETTER than it does in concrete.

Measurement units are confusing. Grrr.

According to this reference, which uses different units, then tensile strength of lead is 2,000 PSI.  - https://mysite.du.edu/~jcalvert/phys/lead.htm#Prop

And according to this - https://civil-engg-world.blogspot.com/2009/04/relation-between-compressive-and.html :

"Commercial production of concrete with ordinary aggregate is usually in the 3,000 to 12,000 psi range with the most common ranges for cast-in-place buildings from 3,000 to 6,000 psi."

So one reference says the tensile strength of  concrete is 300-700 psi and another one say it's 3,000 to 6,000 psi.

 

if I pick the worst-case comparison of concrete being 6,000 psi, and lead being 2,000 psi, then I suppose I might be able to say that the withdrawal strength of a bolt in lead would be 1/3rd that of what it is in concrete. if that was the case and I set up two bolts anchor, each of which is rated for 9,000 pounds in concrete, then it COULD be that those bolts would only hold to 3,000 pounds in lead. Two of them make 6,000 pounds of holding power, supporting a 3500 pound boat.  I would wish for more but that's probably doable.

I still want to hear from engineering gurus.

 

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Oh FML.

Never mind.  Just got this from the class historian.

"Hi Alan
Read the story in the book about the lead. It's not poured. They are blocks with glass gunk fill. Bolts right beside the existing lift points might be ok. But we all use slings."

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Slings likely best. You will need a naval architect to lift by the floors, or bulkheads, or whatever. In theory one can lift by the mast...but in practice....

Assuming you are using the typical marina hoist you will need to consider the crushing force grenerated by non-travelift slings. Spreader bars are likely needed, or even an entire rectangular frame, as the typical hoist lasks the height needed to get a vertical pull. Problematic. Maybe just use the launch ramp?

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I actually have a frame and straps, that worked for the S2 7.9, and this boat is 500 pounds lighter and almost three feet narrower. I could trim two feet out of the port-starboard tubes on the frame and stiffen it up.  I'd probably need to make at least one new strap,  Problem is, the TI Sailing Center guy says "single point lift only".

 

But that's rapidly not becoming an option.  Launch ramp. Oy, ve.

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I was going to suggest testing pull out strength with a smaller / shorter bolt to get a data point for extrapolating a larger bolt.  But it's game over on that.

Seems like the chainplates / mast / gunnels out to be strong enough.  

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If you know where the longitudinal center of gravity is, couldn't you weld up a recangular box with a x shaped cross brace to help with compression forces.  4 cables to a single point hook to attach to single point lift.  Slings off the ends of the rectangular box.  Painted little triangles on edges of deck show where slings need to be positioned.  Voila, a single point sling lift system...

That said, I'm not sure most single point club lifts have enough vertical clearance for this to work...

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If you've never drilled into lead, you're in for a big surprise and a lot of broken bits. Sling it.

Greg

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Slings with a spreader rectangular frame. 2-3" steel square tubing. Nothing fancy. 4 wire ropes or chains from the corners to a common BFS (big fine shackle).

We're only talking about the weight of a car here. (Try the frame on your car first. If it drops 6" onto the tires no big deal compared to dropping a keel boat onto concrete :)

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Once upon  time I wanted to dry sail my S2 7.9, which many of you know, has a lifting 600 pound daggerboard.  The Alameda Marina has a 3 ton hoist with two choices of spreader-bar systems. I knew that, which is why I bought the boat.  Not three months later came the news that Bay West was going to develop the Marina. I went ballistic, wrote letters to the newspaper and got evicted.  so much for launching at Alameda.

So I tried  the only other working 3-ton hoist in the Area, at  Brickyard Cove.   I made up the steel framework and showed it to the harbormaster. He said..."Your system has to be approved by **that rigging guy over there**, and we'll try it and I'll see if I'll let you launch this way."

So I went to that rigging company who will remain un-named. I COULD HAVE made the bridle out of four,  two-ply nylon eye-and-eye straps rated for six fucking thousand pounds EACH and cost $17 each.   Or  yanno, could have made some 6-foot long  s.s. cables, swaged together for a hundred bucks. But NO....no, my lifting bridle cost me over $600, as it was made by the rigger who was required to approve my setup. It's spliced and prestretched dyneema, for fucks sake. Because you know, we must have THE BEST.

And then when it was all done the overhead clearance on the whole thing was about nine inches too much. I couldn't get the hull over the safety railing. I spend almost $1000 on a lifting bridle and it's sitting in my garage doing absolutely nothing.  I sold the trailer and wet-sail the boat out of Coyote Point, which in the end might have been a better idea, anyway as it's 25 minutes form my house.

The clearance on the Brickyard Cove host 4500 pound hoist is about 13' 6".  The clearance on the Alameda Marina 3-Ton hoist is over 16 feet.  I dunno what the clearance on the TI Sailing Center hoist is.

 

Anyway, a 6' 6" spreader bar out of  2 x 8  rectangular box steel  is about  $100 in materials and $75 in welding labor. 

 

Here's a pic of a Piper OD launching with a loader at the Holy Loch YC.

 

Piper-launch.jpeg

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And a couple of Piper OD's sailing off the  Royal Gourock YC...

PiperODs_Gourock.jpeg

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Anyway, the S2 7.9 is supposed to weigh 4,000-4200 pounds.  Somewhere in there.  It's got a 9 foot beam.  The Piper weighs 3500 pounds with a 6' 3" beam.  My lifting framework actually splits in half so it's easier to store on the trailer.  I can just cut the center pieces on my current frame and make it 6' 8" wide and it'll work fine.  I  could  take off the four preposterous prestretched dyneema pieces and replace with four  double-ended double-layer nylon slings @ $17 each  I re-use the shackles and lifting ring....or if the clearance is enough, I use the dyneema.

 

I'll just have to re-size the straps that go under the boat.

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Have you looked at launching and storing at Brickyard Cove? I don't know what the height specs are for their hoist but I'm pretty sure 3500 pounds is OK.

Very close to the central bay as you know.

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Drill all the way through, enlarge an opening at the bottom, and fit a big washer and nut, then fill and fair    

 

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If that's not enough, how about drilling a horizontal hole through the keel and putting in a rod with a few tapped vertical holes. 

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