Is That Bolt Hollow?

hollow-bolts

Why yes…yes it is!

One of the clever inventions we ran into at AirVenture this year was on display at the Click Bond booth. Click Bond, makers of a wide variety of adhesive standoffs and other aerospace fasteners, has come up with an interesting way to save weight – a fraction of an ounce at a time. These bolts are designed to replace solid bolts in non-structural applications – such as holding wire bundle clamps to the Click Bond standoffs.

The bolts are hollow, from the head down into the threaded portion, and are made that way by drawing the raw material into a die. Not only are they hollow to save weight, but they feature a captured washer as part of the head design – so that you don’t end up with loose washers floating around in hard to reach locations. And not only does the head feature a standard wrench interface, the hollow portion is also molded so that you can use an Allen wrench if you so desire.

Now you probably wouldn’t use these to hold the wing or tail on to your homebuilt – but if you are really serious about saving weight wherever you can, these might be the ticket when holding non-structural panels in place, attaching Adel clamps, or fastening anything that doesn’t need to carry a huge load. The ones we were handed were standard AN3 size, and they are reputed to be 50% of the weight of a stainless steel alternative.

How much weight can you save? Well that depends on the number of fasteners you have in your airplane that could be suitably replaced by these little gems. For most of us, that’s not a lot. Of course, if you’re building a Boeing, the weight savings can easily reach into the hundreds of pounds! More interesting, I think, is the shear ingenuity of the hollow bolts. They are just so clever, I feel like I need to install a few just so people ask about them.

Paul Dye

Paul Dye, Kitplanes® Editor in Chief, retired as a Lead Flight Director for NASA’s Human Space Flight program, with 40 years of aerospace experience on everything from Cubs to the space shuttle. An avid homebuilder, he began flying and working on airplanes as a teen, and has experience with a wide range of construction techniques and materials. He flies an RV-8 that he built, an RV-3 that he built with his pilot wife, as well as a Dream Tundra they completed. Currently, they are building a Xenos motorglider. A commercially licensed pilot, he has logged over 5000 hours in many different types of aircraft and is an A&P, EAA Tech Counselor, and Flight Advisor, as well as a member of the Homebuilder’s Council. He consults and collaborates in aerospace operations and flight-testing projects across the country.

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