Slipway Winch

I would suggest getting rid of the steel cable, and replacing it with dyneema line. It is pretty quickly replacing wire, but is much lighter, stronger, and cheaper. And the recent numbers indicate it is seeing a service life longer than wire on tug boats. Plus is it light enough that a single person can carry rolls of it instead of needing chase lines, guy lines, and the like.

As for the design, I can't really comment.

 

Hi Stumble,
It's good point to consider, thanks. But, I think it's more expensive than steel wires............I'll check.

Abohamza

 

Just remember that size on size is not a reasonable comparison.

Both 26.1mm dyneema and 37.75mm wire have the same breaking strength of 50 tons, but the dyneema will float, and weighs .45kg/m vs around 3kg/m (sorry had to do the conversion in my head, it is 290lbs/100foot.

Having worked with both, I can tell you it is much, much easier to work with the dyneema, and it can be spliced by hand. Not to mention if you have any concern about on the job injuries the likelihood of throwing out backs, and other lifting related injuries dyneema virtually eliminates these.


Note, I don't sell this stuff or anything, but it truly is a wonder material.

 

Its not a lifting wire that you need, a lifting wire is rarely dragged 200 foot along the ground infact very rarely does it get off the ground apart from a minute or two of max pull.

 

Probably would do less damage if something snapped too - steel cable that lets go at the attached end is very scary

 

Dyneema is totally unsuitable unless you want to replace it every month. It is a chemical based plastic, strong yes but it wont last long dragged about the floor. Dyneema although is not too springy it is more so than steel, you will get the boat bouncing up the lines, that is stopping and starting and not a constant pull. Even 50mm steel wire will do that.

Have you guys ever used a slip way?

 

Frosty,

Clearly you don't know what you are talking about on this one.

Dyneema is currently being used by a lot of lumber companies to drag trees through the forest, and are seeing a longer lifespan with it than they were with wire.

It actually has less stretch than wire cable (excluding creep) under the same load vs the same break strength, and it isinsainly better than steel when compared by size.

It has replaced a large number of steel towing lines in the north pacific and Atlantic commercial fleets.

I can give you number of river tow boat companies on the Mississippi river that have completely replaced steel for dyneema (I did the liability review for one).

a number of dams have replaces steel cable for lifting sluce gates with it.

I can go on and on. I have a huge stack of paperwork on this stuff that is what drove one tug company here to switch todyneema instead of their 6" cable about a year ago. It is seeing a better than steel service life so far, a reduction in tie up time of more than half, and they have so far eliminated lifting related injuries while doing tie ups, as well as reduced fatigue. The test boat was so successful that instead of a one year test program, it was shortened to 6 months, when the crews fell in love with it.

 

The question was have you ever used a slipway?

 

Frosty,

I have no experience with a slipway, so no my experience is not directly transferable. But I do have direct experience using dyneema in the following: long tows, push barges, lifting bridles, cranes, dock lines, anchor lines, running rigging, standing rigging, lifelines, fishing line, and shoe strings. in addition I have followed the research done by a number off forestry, tow boat publications, fishing publications and governmental industries.

There're certainly limitations to the line like any material, but they honestly have more to do with specialized applications, like high heat, or specific caustic substance issues, rather than it's general applicability. For instance the recommended replacement interval for dynex-dux standing rigging is actually longer than for rod rigging, weighs less than 1/5, and cost about half of what nitrile rod rigging costs, and about 80% the price of new wire rigging. Note that the Dux is a different material than sk-75 which is being used as hawser replacements.

 

It all sounds very good, and looks to have advantages. ( like safer on breaking recoil)
eg.
http://www.youtube.com/watch?v=GDJ3QjvRZT0

one comment on the product at that site though

"he only problem with dyneema and similar synthetic materials is when for example you take razor and touch steel rope, it holds together, and when you touch dyneema it brakes instantly.

That is the main problem when it comes to fishing line, which i used, and it has a problem of sudden and unexplainable braking... monofil is much more predictable, even if weaker."

To my mind, in a critical application like hauling big boats up slipways, unless you can inspect every metre for signficant exterior damage, you are going to breath easier with steel.

 

Rwatson,

Certainly abrasion resistance with dyneema line is not as good as with steel, and this is a real problem dealing with it, and something that has to be taken into account. On the other hand there awesome real advantages compared to wire, and these two things need to be balanced when deciding on a system.

However lets put this into perspective. Dyneema's individual fibers are actually more resistant to abrasion than steel fibers of the same size. While this is hard to swallow remember the size of the fibers in wire rope will be much larger than dyneema fibers. In practice dyneema is abrasion resistant enough that gloves made from it have replaced pretty much every other material, except in some very high abrasion jobs where a blend of dyneema and wire are being used.

As for cutting it with a razor blade. I guess it is possible when dealing with fishing line and other micro-lines, but the splicers I know who deal with it are using ceramic "never need to be sharpened" knives to cut the stuff, and are replacing knives every 10 splices or so. In short, unless you are deliberately trying to cut this stuff it is almost impervious to abrasion in normal use (again they are using it to drag trees out of forests in lumber operations).

As for using it uninspected... I can't really speak to the specific application, however, and I am repeating myself, this is not traditional line. It really is a huge step forward compared to steel, and other aramid fibers. Just do a google search for dyneema abrasion and you will see what I am talking about.

As for cost... (from McMaster Carr for the cable, West Marine for the dyneema)

3/8 7x19 ss cable 4.37 a foot with 12,000lbs breaking str
3/8 7x19 steel is 2.70 a foot With 15,000 lbs breaking str
3/8 12 strand dyneema is 2.57 a foot with 19,600 lbs breaking str.

 

Guys, this poster is talking about a several-hundred-ton capacity railway and to me that means at least 1.25 inch diameter flexible steel wire rope, probably 6x19 or 6x37. There may be better materials.
In my experience (and I have helped build, used, and hauled many boats, on several railways), we used wire because it was best available for the job at the time.
I have not worked with other materials for this particular job, but I've towed with others and did have a 3" diameter bluesteel tow rope break at the top of the thimble of the spliced eye (for camera we had to tow from an underwater eye on the bottom of the stem) from distortion and bollard pull, and put this $5million dollar floating set onto a nasty reef in the Bahamas one very nasty night.
Luckily it was high tide and we blew across with inches under the flat bottom, taking one big breaking sea aboard, completely swamping the generators and toilets, and scaring the crapola out of all of us.
Here is the shipyard launching this very heavy (about 100 tons) steel and timber set with a dead lift. Gotta trust those (wire) straps.
On a railway, the rope you use gets dragged back and forth in whatever material the rails are set down upon, so this could be sand, mud, rock, shingle etc. The entire length of line is subject to this steady abrasion. Floating line is an interesting concept and might keep this to a minimum but only below the waterline.
The usual rig is two triple blocks, one with a becket, giving 7:1 to the powerful drum on the winch and two singles on the other end, one with a becket, for the down haul going to the whip drum, giving 2:1.
In hauling you slack the down haul and wind up the engine and up she comes, dripping barnacles. Going back down is more delicate, since you are pulling with the down haul and holding the car back with the brake on the other drum so it doesn't run away.
This was using WW2 ship's deck cargo winches, a standard design world wide and still rusting away in the back of marine scrapyards everywhere. As built they used a 6 cyl gas or diesel engine of maybe 75 hp, but the large one at Bob's Boatyard in Sausalito when Don Bailey ran it had been modified to a chevy v8 and needed it. This was the 400 ton capacity car, the others were <100 ton capacity.
The new rope materials certainly sound interesting since those industries that traditionally use wire are changing to the new stuff so it must work well for them, but personally if I were setting up a railway to haul 300-400 ton boats I'd do it the old way because I know it would work and I wouldn't lose anything in development of something new.

 

Why Safety Factor=1.75?

 

How does your boat get into the cradle?

I am a marine engineering. I have a case about slipway planning(the boat tonnage is 190ton), but I don't have the experience about getting the boat into the cradle, Can you show me the experience? Especially how to get the boat's hull fit the cradle? During the process, need any divers or tug boat? Thanks for your reply.

 

It depends. The usual ways csar is a flat platform of steel beams with a system of sliding or pivoting support arms.
When hauling a boat out, the vessel is gently guided over the ways car and tied to it, then the car is hauled up the track just a little, enough for the keel to touch, then the arms and supports are adjusted to keep the vessel upright, and then they are locked in place.
When all is secure, the car is slowly and carefully hauled up the track. Often additional shores are added after the boat is out.
A fitted cradle is not used on commercial haulouts in my experience.