A Simple Trick for Perfect Wheel Pant Bulkheads

Use safety wire to capture complex shapes.

Experimental Aviator
Updated:
Paul Dye
By Paul Dye
The wheel pant (left) needs a fiberglass bulkhead that can be created with a foam backer. But how to get the measurement and shape right without a lot of waste? Cut a length of big safety wire (you have a roll, but you hardly ever use it unless you’re working on DC-3’s …) and wrap it around the outside of the pant about where you want the bulkhead. Twist it together and make it tight to the pant.

The 25-year-old wheel pants for our F1 Rocket project had no rear bulkhead for the aft part of the pant—something that really makes the pant more rigid and sturdy. Making a bulkhead out of foam and fiberglass isn’t hard—but getting the size and shape right without a bunch of trial and error (and waste) can be tricky because the shape of the pant is not simple. Here’s a little trick—use a piece of large-diameter safety wire to figure out the shape of the outside of the pant—the inside is only slightly smaller because the glass skin isn’t that thick. The big safety wire holds its shape pretty well if you’re careful with it—and getting the shape is what you’re trying to do. You can use this same trick in a number of places when you build—just think creatively!

Slide your “form” off the pant and flatten it out, but don’t change its shape. Place it on a piece of foam and trace the outline. Cut the foam along the line and you have a bulkhead blank! Pop the foam bulkhead in place to check the fit, adjust as required, then lay up a glass bulkhead over it, with flanges bonded to the inside of the pant—you now have a much more rigid wheel pant!
Paul Dye
Paul Dyehttps://ironflight.com
Paul Dye retired as a Lead Flight Director for NASA’s Human Space Flight program, with 50 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 has built and flown an RV-8, Subsonex jet, and an F1 Rocket - in addition to the RV-3, Dream Tundra, and electric Xenos motorglider he built along with his pilot wife. His next project is a highly modified RV-3. A commercially licensed pilot, he has logged over 6000 hours in many different types of aircraft and is an A&P, FAA DAR, EAA Tech Counselor and Flight Advisor; he was formerly a member of the Homebuilder’s Council and is now on the EAA Safety Committee. He is also a member of SETP and consults on flight testing projects.

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Wing Smith
Wing Smith
4 months ago

Especially on this wheel pant shape the top and bottom curvature provides form stiffness. The large nearly flat side portions will pucker in at high speed from the suction caused by the opening around the wheel.
All you need is a 1/2″ rib on each side.
If you must use a bulkhead, poke a hole in it to equalize the pressure.

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JoeP
JoeP
Reply to  Wing Smith
4 months ago

If you’re going to poke a hole on it. do it at the bottom to allow all the moisture and debree a means to get out.

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