Harken 29mm Blocks

Harken 29mm blocks, also known as the 29mm Carbo range, are one of the most widely used pieces of dinghy sailing hardware in the world and consistently one of our best sellers here at Sailing Chandlery. The 29mm sheave size sits in a sweet spot that works brilliantly across a huge range of dinghy applications, from control line systems on smaller boats right up to mainsheet and jib sheet systems on larger performance dinghies and small keelboats. They are built from Harken's tough glass fibre reinforced composite material with free-running ball bearings inside, which keeps friction to an absolute minimum and makes every system they're part of noticeably easier to trim. With breaking loads of up to 907kg on some versions, they are incredibly strong for their size and weight, and they come backed by Harken's five year warranty.

Harken 29mm blocks are used on an enormous variety of boats, which is exactly why they're so popular. On the ILCA and Laser, they're a go-to choice for cunningham and vang systems. On the Topper, 29er, RS Aero, and other performance single and double-handed dinghies, they appear in mainsheet systems, jib purchase systems, and a wide range of control lines. On catamarans they're commonly found in jib sheeting systems and cascade vangs. Even on larger keelboats and yachts, the 29mm Carbo blocks are regularly used for lightly loaded control lines where a small, lightweight, and reliable block is the right tool for the job. If you're unsure whether 29mm is the right size for your specific application, just get in touch and we'll help you work it out.

Both are 29mm Carbo blocks with the same excellent ball-bearing system, but the way they attach to your boat is completely different. The standard Carbo block uses a conventional shackle or fixed head to connect to a fitting, strap, or deck plate, which is the familiar setup you'll find on most boats. The T2 soft-attach block is a genuinely clever bit of engineering: it has no metal shackle or rivet at all, and instead uses a length of high-strength Spectra line that you can tie, splice, or lash directly to almost any point on your boat. This makes it significantly lighter and lower profile than a shackled block, and it's a popular upgrade for performance sailors who want to reduce weight aloft or in critical parts of the rig. The T2 is particularly well suited to vangs, traveller controls, cunninghams, and mainsheet systems on smaller dinghies like the Optimist.

Harken 29mm blocks accept rope up to a maximum of 8mm in diameter, which gives them a step up in versatility over the smaller 16mm and 22mm blocks in the range. In practice, most dinghy control lines running through 29mm blocks will be in the 6mm to 8mm range, though the blocks also run happily with thinner lines if the system calls for it. As with all blocks, it's worth staying within the recommended maximum rope diameter rather than trying to force thicker line through the sheave; an oversized rope adds friction, makes the system heavier to operate, and causes unnecessary wear on both the rope and the block itself. If your lines are consistently thicker than 8mm, it's worth considering a step up to the 40mm Carbo range.

Harken 29mm blocks are built to last and genuinely need very little attention to stay in great shape, but a simple routine after every sail will keep them performing at their best for many seasons. The most important step is rinsing them with fresh water to flush out any salt that's worked its way into the bearings, as salt build-up is the main cause of sluggish, stiff-feeling blocks over time. Every few months, a drop of a light lubricant such as McLube on the bearing will keep everything spinning freely and help prevent corrosion in the internal components. It's also worth giving the composite body a quick visual check for any cracking or damage, particularly if the blocks have taken a knock, and checking that shackle pins and attachment points are still secure. With that level of basic care, your Harken 29mm blocks should give you reliable, low-friction performance year after year.