Itty-bitty Harken Carbo blocks vs. 3" 75mm Classic stockers

Murrays sells pretty much only 57mm Carbos... and 16 now come stock with 40mm Carbos.

I prowled Ebay until I found a good deal on a 57mm triple block to replace the 3 individual 3" Classic Harken that came with my boat. The size difference is stunning, and I'd be tempted to run a triple Carbo in 75mm if they weren't so pricey... and relatively rare compared to the 57mm blocks.

I searched here and online looking for a comparison article between Classic and Carbo blocks to no avail... am I two decades late in asking this question and everyone just KNOWS that Carbos are better? And generally are 57mm Carbos sufficient and reliable on an H18?

Randii

57mm = 2.25", standard size block on a Hobie 18 mainsheet system. Max working load for a triple is 2380lb which is more than sufficient for a H18 mainsheet system. Just be sure to use the right diameter line. If the sheet is too fat, it won't run through the boocks well.

sm

MMMMM.... gotta love the taste of humble pie. My blocks are all 2.25-inch blocks except the Hexaratchet which is a 3-inch block.

Randii

I'm a documentation guy... give me the internet and a few minutes and I'm self-entertaining. :p

I pulled the following data from Harken’s website on their family of Carbo blocks.
Harken 40mm Carbo http://www.harken.com/productcategory.aspx?taxid=417 (all data based on swivel blocks)
Single Block: MWL: 220 kg; 485 lb . . . . . . . . BL: 735 kg; 1620 lb
Double Blocks: MWL: 220 kg; 485 lb . . . . . . . . BL: 735 kg; 1620 lb
Triple and above: MWL: 660 kg; 1455 lb . . . . . . . . BL: 1383 kg; 3050 lb
Harken 53mm Carbo http://www.harken.com/productcategory.aspx?taxid=418 (all based on swivel blocks)
Single Block: MWL: 359 kg; 792 lb . . . . . . . . BL: 1079 kg; 2380 lb
Double Blocks: MWL: 720 kg; 1584 lb . . . . . . . . BL: 1500 kg; 3300 lb
Triple and above: MWL: 1080 kg; 2380 lb . . . . . . . . BL: 2270 kg; 5000 lb
Harken 75mm Carbo http://www.harken.com/productcategory.aspx?taxid=419 (all based on swivel blocks)
Single Blocks: MWL: 550 kg; 1213 lb . . . . . . . . BL: 1650 kg; 3638 lb
Double Blocks: MWL: 1100 kg; 2426 lb . . . . . . . . BL: 2722 kg; 6000 lb
Triple and above: MWL: 1650 kg; 3639 lb . . . . . . . . BL: 4535 kg; 10000 lb

I pulled similar data from Harken’s website on their 2.25-inch Classic blocks. http://www.harken.com/productcategory.aspx?taxid=427
Single Blocks: MWL: 227 kg; 500 lb . . . . . . . . BL: 1134 kg; BL 2500 lb
Double Blocks: MWL: 454 kg; 1000 lb . . . . . . . . BL: 1361 kg; BL 3000 lb
Triple Blocks: MWL: 544 kg; 1200 lb . . . . . . . . BL: 1361 kg; BL 3000 lb
I looked at data from Harken’s website on their 3-inch / 76mm Classic blocks. http://www.harken.com/productcategory.aspx?taxid=428
This got messy! The Classic blocks are 76mm – different than the 75mm Carbo blocks, oddly enough. Harken has Small Boat Classic heavyweight blocks and… uh… ‘standard weight’ blocks and also Mid-Range Classic Blocks? The difference in the Small Boat Classics appears to be in the swivel, but there may be more than meets the eye… Harken has an FAQ article on the Midrange Classic Blocks that have some info on the blocks. They “increased the Midrange block's MWL by using a forged shackle, a larger diameter shackle pin with a higher shear value, and stainless steel straps on sideplates that wrap over the top of the block.” http://www.harken.com/article.aspx?id=12834 The blocks I have are definitely smallboat Classics, and look to use standard-weight shackles. I include this section for reference.
Single Blocks: MWL: 340 kg; 750 lb . . . . . . . . BL: 1134 kg; BL 2500 lb
Single HW Blocks: MWL: 340 kg; 750 lb . . . . . . . . BL: 1361 kg; BL 3000 lb
Single Midrange Blocks: MWL: 816 kg; 1800 lb. . . . . . . . BL: 2268 kg; 5000 lb

MWL = Maximum Working Load
BL = Breaking Load

So for a straighter comparison:
Harken 53mm Carbo blocks http://www.harken.com/productcategory.aspx?taxid=418
Single Block: MWL: 359 kg; 792 lb . . . . . . . . BL: 1079 kg; 2380 lb
Double Blocks: MWL: 720 kg; 1584 lb . . . . . . . . BL: 1500 kg; 3300 lb
Triple and above: MWL: 1080 kg; 2380 lb . . . . . . . . BL: 2270 kg; 5000 lb
Harken 2.25-inch Classic blocks http://www.harken.com/productcategory.aspx?taxid=427
Single Blocks: MWL: 227 kg; 500 lb . . . . . . . . BL: 1134 kg; BL 2500 lb
Double Blocks: MWL: 454 kg; 1000 lb . . . . . . . . BL: 1361 kg; BL 3000 lb
Triple Blocks: MWL: 544 kg; 1200 lb . . . . . . . . BL: 1361 kg; BL 3000 lb

From this, it looks like Classic single blocks are slightly stronger than Carbo single blocks for both MWL and BL, and Carbo double blocks are slightly stronger than Classic double blocks. For triples, it ain't even close -- Carbo beats the Classics significantly.

So in WAY too many words... I feel good about swapping out the three 2.25" single Classic blocks and reeving in the Carbo triple block.

Thanks!

Randii

A single triple block is definitely the way to go. The individual single blocks don't reeve well and tend to twist. They also don't sheet down as far as the single triple. Just make sure the triple block can not spin or it will tend to tangle. I used a thin piece of line between the shackle and the block housing to stop it from rotating. The block can still pivot about 90 degrees in either direction, but it can't go all the way around. You may also want to move the center boom bale back an inch or two and angle it so it lines up better with the pull of the mainsheet system. You can also double up the boom bale for added strength since the bales were only intended to take the load of 1/3rd of the total mainsheet load.

sm

Yup. The 57mm carbo triple up top works great with the stock 57mm classic triple below. There's WAY less line resistance in the system... so little that the stacked stock setup (57mm triple over 75mm hexaratchet) tends to flop over from gravity in light air (it did not do that with the stock three separate blocks) That annoyance is small compared to the free-ness of line flow, impressive even with a fat, fuzzy, older mainsheet. I was also surprised at the added length in mainsheet the resulted from moving from three singles to one triple. The more I sheeted out, the more noticeable that was.

I have the boom-bound triple set to swivel freely right now, and will add a control line as necessary. There's a stamped insert on carbo swivels that can lock parallel or perpendicular to the boom or lay down and allow a full swivel. It is slick, functional engineering.

I will probably add a quick-latch/lock up top for quicker setup and breakdown and to play with which bale I want to use on the boom.

Randii