We set about comparing the new 20 and 30mm Orbit blocks with the comparable Harken and older Ronstan blocks. Basically we looked at two main categories - working loads and weights. Rob was very meticulous in his calculating and measuring, there were even spreadsheets involved. In the end we found that the numbers weren't as straight forward as we'd thought they would be and it was difficult to make direct comparisons but we've done our best.
Below is the working load data for the blocks. The main thing we found was that there appears to be no standard safety factor being applied by manufacturers to calculate their MWL (Max or safe working load). They vary from around to 2 to above 6 and it does seem to be the case that Harken's numbers are generally higher than Ronstan's. Even within manufacturers they don't appear to be standardized.
We calculated an average of all the safety factors and then used that to calculate an standardized MWL using the BL (breaking load) of the blocks. We felt this was the best way to compare strengths across the different blocks.
|Part #||BL #||MWL #||Manuf.|
|Max Work Load|
Safety Factor = 3.2203
|20 mm Singles|
|Ronstan||NEW 20 mm Orbit; single lashing||20 mm||RF25109||1210||550||2.20||376|
|Ronstan||20 mm Single Loop Top||20 mm||RF20101||1210||550||2.20||376|
|Harken||Micro Single||22 mm||H224||1200||200||6.00||373|
|20 mm Doubles|
|Ronstan||20 mm Double||20 mm||RF20202||1540||770||2.00||478|
|Harken||Micro Double||22 mm||H226||1200||350||3.43||373|
|30 mm Singles|
|Ronstan||30 mm Single Swivel||30 mm||RF30100||1650||660||2.50||512|
|Ronstan||NEW 30 mm Single Swivel Orbit||30 mm||RF35100||1323||661||2.00||411|
|Harken||Bullet with Swivel||29 mm||H166||2000||300||6.67||621|
|Harken||29mm Carbo Single (w/ swivel)||29 mm||H340||1000||330||3.03||311|
|30 mm Doubles|
|Ronstan||30 mm Double||30 mm||RF30202||2090||880||2.38||649|
|Ronstan||NEW 30 mm Double Orbit||30 mm||RF35202||1984||992||2.00||616|
|Harken||Bullet Double||29 mm||H084||2000||400||5.00||621|
|Harken||29 mm Carbo Double||29 mm||H342||1625||660||2.46||505|
We also looked at the weights of the blocks, both as stated by the manufacturer as well as our own measurements from our postal scale. For the most part they were the same but there were some small variations. We also calculated a strength to weight ratio in two ways. First we used the manufacturers stated MWL and weight and then we used our calculated MWL using the average safety factor and our own measured weight.
|Manufacturer||Block||Sheave Diameter||Part #||Man. Listed weight||Strength to weight ratio based on man. data||Weight per postal scale||Strength to weight ratio||Man. Stated Max Diam. Rope|
|Ronstan||20mm Orbit (Single Lashing)||20mm||RF25109||0.3||1833||0.3||1252||6mm (1/4")|
|Ronstan||20mm Single (Loop Top)||20mm||RF20101||0.5||1100||0.6||626||6mm (1/4")|
|Harken||Micro Single||22mm||H224||0.5||400||0.6||621||6mm (1/4")|
|Ronstan||20mm Double||20mm||RF20202||1.5||513||1.5||319||6mm (1/4")|
|Harken||Micro Double||22mm||H226||1.5||233||1.4||266||6mm (1/4")|
|Ronstan||30mm Single Swivel||30mm||RF30100||1.2||550||1.2||427||8mm (5/16")|
|Ronstan||30mm Single Swivel Orbit||30mm||RF35100||1.1||601||1.2||342||8mm (5/16")|
|Harken||Bullet with Swivel||29mm||H166||1.75||171||1.5||414||8mm (5/16")|
|Harken||29mm Carbo Single (w/ swivel)||29mm||H340||0.9||367||0.9||345||8mm (5/16")|
|Ronstan||30mm Double||30mm||RF30202||2.8||314||2.6||250||8mm (5/16")|
|Ronstan||30mm Double Orbit||30mm||RF35202||1.7||584||1.8||342||8mm (5/16")|
|Harken||Bullet Double||29mm||H084||2.5||160||2.4||259||8mm (5/16")|
|Harken||29mm Carbo Double||29mm||H342||1.8||367||1.8||280||8mm (5/16")|
So what does all this mean? Well, clearly the Ronstan safety factors are lower than those used by Harken. When we calculated the MWL based on our average safety factor this meant the Ronstan blocks generally saw their MWL reduced while the Harken's increased. This affected the strength to weight ratios in the same way.
Does this make the Harken's better? I don't really think so. The vast majority of dinghy applications see these blocks used at loads far below their MWL let alone their BL. If you are pushing the limits of the loads though, I think the data supports leaning towards the Harken products over the Ronstans.
There's also something to be said for the fact that the Ronstan blocks may just function at a higher percentage of their breaking load than the Harkens. Unfortunately I don't have the technology to test that in house - but if anyone wants to give me a load cell for free I'd gladly break some things.
The new Orbit blocks are definitely a new direction in block technology and it's great to see Ronstan pushing the boundaries of classic hardware. Using the soft loop attachments are a great idea and I think definitely something we'll see a lot more of in the next few years. They don't appear to offer the weight advantages you might expect though - the Harken blocks are the lightest in many of these categories.
If you were expected a "this is the best one" conclusion at the end of this post I'm afraid I'm going to disappoint you. I do think the 20 mm Orbit single is a pretty cool block - it's super lightweight and can be lashed anywhere you need it. I think the 29 mm Harken Carbo blocks are still a great choice for larger diameter lines. Beyond that there's no clear winner here. Each block has advantages and we didn't even cover pricing.