Pulley Blocks (triples) for Davits

[Papawads]

Never purchased a marine pulley block in my life.... quite clueless! I'm going to purchase 4 x triples for my new davits to lift 85kg.

I can pay anywhere from 30 to 300 pounds/euro/dollars each, and not sure which end of that scale I should be. Thoughts welcome. Views on types or makes?

Also, views on what diameter would be most welcome.

I can rebuild my Yanmar blindfolded but don't have a clue here.

Thanks
:-)

[team karst]

I just went thru this with my rib motor setup. Fiddle blocks were too long for my setup. Plus i wanted a locking cam at the top block. And a becket feature didnt exist for a double block; only for odd numbers.
Beyond that, you will want marine grade /stainless for a boat. Check out defender for options.

[wingssail]

Originally Posted by Papawads

Never purchased a marine pulley block in my life.... quite clueless! I'm going to purchase 4 x triples for my new davits to lift 85kg.

I can pay anywhere from 30 to 300 pounds/euro/dollars each, and not sure which end of that scale I should be. Thoughts welcome. Views on types or makes?

Also, views on what diameter would be most welcome.

I can rebuild my Yanmar blindfolded but don't have a clue here.

Thanks
:-)

Strength will probably not be an issue (your 85kg load) but friction will be and length may be.

Select larger diameter (2.5" or 60mm) diameter for lower friction. Roller blocks will also be lower friction.

Avoid if possible long block assemblies which would let the dingy hang lower than desirable. Install cleats on the davit structure instead of using built in cleats on the blocks.

[ggray]

Is that 85kg total, or each davit? (If we are talking for a dinghy with motor, likely more on one davit than the other).

Harken, Ronstan, and others of have a wide range, and you do pay a little more for ball bearings which would make it easier to hoist, but you can pay a lot more for lighter weight blocks--more important for racing sailors than for you.

Just know the load, and look at the specs for each block considered.

Here are ways to rig the blocks to have the axles at right angles to each other which helps to keep the loads distributed evenly. If the load is 85kg total, you probably can get by with 4:1 which may not be pictured, but easy to rig.

You may need to invert some of these diagrams for your situation, and/or delete the cam cleat as drawn


https://www.harken.com/en/support/se...ving-diagrams/

[rslifkin]

The easy button would be to buy a pre-rigged setup from a company that sells davits. Garhauer sells a set of 4 triple blocks rigged in pairs (6:1 purchase) with lines already run through the blocks and snap hooks included for just over $300, for example.

[Chotu]

Originally Posted by rslifkin

The easy button would be to buy a pre-rigged setup from a company that sells davits. Garhauer sells a set of 4 triple blocks rigged in pairs (6:1 purchase) with lines already run through the blocks and snap hooks included for just over $300, for example.

Here those Garhauer ones are in action


Very smooth motion, great shipping speed and great mechanical advantage

[rslifkin]

I have the full set of Garhauer davits on my boat (pictured below) and can also agree that their block setup works quite well. Mine are configured slightly differently than Chotu's (cam cleats are separate rather than integrated into the blocks), but the blocks themselves are the same hardware.

[TrentePieds]

Papawads wrote: "Never purchased a marine pulley block in my life.... quite clueless!"

Well, in that case you should probably get yourself a copy of Manual of Seamanship wherein all is made crystal clear. This manual was the textbook provided to boys. In this context "boy" does not mean your common male juvenile but rather a "new entry" in the Royal Navy" — a "boy seaman" who is about to "learn the ropes". As late as my boyhood, lads in Whitby and Grimsby came out of the womb already knowing these things :-!

Here is a link to "the bible": The pages you are principally interested in will be pp 62 - 78.

https://maritime.org/doc/luce/part1.php

Something you should know, something that should be written plainly and indelibly on the inside of your forrid, is the number of pounds of pull you can exert on a fall when you are standing bold upright, quite unsupported, in your cockpit and pulling horizontally. The horizontal pull will always be the LEAST pull you can exert, and it will therefore govern the kind of tackle you need to rig for a given job.

You should also learn the names of the various KINDS of tackle and their characteristic uses.

A twofold purchase is probably all you need. Look it up in the link I gave you. Given 1/2 the weight of the dinghy on each tackle i.e., 42 Kg. and the mechanical advantage of 4, which is what the twofold purchase gives, the necessary haul on each fall is only 10Kg or 22 lbs. You can do that standing upright! Thus, four double blocks from, say, Harken's should do the job for you.

Should you need to hoist something substantially heavier, you could rig up a modern-day griolet :-)

Happy hoisting :-)!

TrentePieds