The Hatschek Hook

Bob Hatschek designed his hook in 1976 and started selling it in 1977. By the time production ceased, he'd supplied well over 1000. I still have six with serial numbers ranging from 018 to 1141.

This wasn't the first commercial hook. Elton Drew's Maxaid twang hook has that honour, but the Hatschek was the most popular commercial hook until Makarov, Kochkarev and Stamov started selling models and accessories.

The Hatschek was designed from the outset for volume production and to minimise the man hours required to make each one. All parts were made using jigs and simple tools, so no measurement was needed to make a hook. It was designed when circle tow was just becoming popular and models still used all-wood, open structures. The first World Champs where most competitors used circle was 1975 at Plovdiv and the hook was available just in time for the 1977 World Champs in Demmark. In this era most unlatch tensions were in the vicinity of 4 or 5 pounds (2 - 2.5 Kg), so later criticisms of the hook because of its spring strength are a little unfair.

Complaints that its size made it fiddly are likewise unfair: this picture shows clearly that the body of the hook is the same size as the M&K hook:

The hooks compared: Hatschek s/n 018 on the left and a recent M&K standard hook on the right

The only major differences are:

• the M&K hook and latch are considerably larger.
• a Hatschek can be adjusted entirely from beneath the model while an M&K needs access from above (glide and circle turn), below (unlatch tension), front (straight tow) and the rear (zoom rudder). In short, a Hatscheck generally comes out of the model only for servicing and can be adjusted in situ with an Allen key and a screwdriver while an M&K needs special tools or removal from the fuselage to change some settings.
• a Hatschek's normal mount is easier to move fore and aft to correct the hook position than a typical M&K mount.

With hindsight, the only real weakness in the Hatschek is the scissor spring, which Bob used because it has more of a snap action than a normal compression spring, and the limited space available for it. Both factors severely limit the unlatch tension. It was plenty for the early years, when we flew 100% wooden wings at 4 to 5 lb unlatch tension without premature unlatching being a problem. As soon as carbon spar flanges came in with balsa/glass D-boxes (around 1983) the wings got stiffer and no longer damped out sudden loads so we had to put up the unlatch tension to the 7 to 8 lb (3 - 3.6 kg) mark to avoid premature unlatching in turbulence. This is pretty much the Hatschek spring limit. I stayed with Hatscheks until I went to the full carbon structure which can't be flown below about 15 lbs (7 kg), even set up for zoom launches, due to the extreme wing stiffness and the consequent lack of gust damping. As a result I started moving over to M&K hooks in 2001 after 24 years as a happy Hatschek user.

If the Hatschek had been 2-3 mm taller and maybe the same amount longer it could have taken a heavier, more durable scissor spring. If it was 6mm taller I think simple re-engineering could have let it use a conventional compression spring. The zoom rudder adjust collar could have been made bigger in diameter and used as as the tension adjustment with the main spring fitted round the hook shaft. The tension adjustment grub screw could have been replaced by a longer machine screw, extending up in front of the compression screw as the zoom rudder stop.

Commercially available hooks, excluding those only sold pre-installed in ARTF models, have only been available from a small group of suppliers. For completeness, here is a list of the main suppliers:

• Maxaid. This was a twang hook designed and sold by Elton Drew from early 1975.
• Hatchek. Designed by Bob during 1976 and available from early 1977.
• Schmidt. A Lepp-type hook made from metal and brown plastic mouldings. It was quite a large unit, supplied with a brown plastic mounting. The hook was hung from the mount.
• Stamov. The Viktors, Stamov and Isaenko, popularised this design. It is a sliding plate type that is usually sold without a mounting.
• Denken. These were a blue anodised Lepp type, made and sold from Bulgaria by Alexander Denkin.
• W-hobby. This is a sliding plate type, usually sold as part of a drop-in unit that incorporates a clockwork timer and an integral hook mount.
• Makarov & Kocharev designed and sell a machined and anodised hook. Its inverted L mounting is designed for attachment to the right side of the fuselage.
• Duniev. This was a cheaper knock-off of the M&K hook.
• Vasily Beschasny sells a Lepp type that is suspended from an overhead mount.