One-piece bumpers - What should gap be between bumper and frame?

We are building one-piece bumpers for the first time and are unsure how much to oversize them. Triple Helix appears to use a 1/8" gap on each side, which sounds pretty good, but we’re wondering if others agree. We could not find a specific acceptable gap distance in the rules.
We’re thinking these bumpers are like jeans, we don’t want them too tight or too loose, but would prefer not to remake them too many times.
Also, any other suggestions on making one-piece bumpers would be appreciated.

We are in line with Triple Helix, about 1/8" shims when we laid the bumper mounts.


The maximum gap is 1/4in in the rules (see R26), with some exceptions.

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You probably want just enough gap, so that it’s easy to install and remove the bumpers. But no more.

You might find that achieving that gap can be challenging, because of things you didn’t anticipate, such as exactly how thick the “back side” of the bumpers is, when you attach the cloth.

Have fun!


Jim is spot on, as usual;) The High Rollers build the wooden frame with a 3/16" gap on all sides to provide room for folded fabric on the backside of the bumper and interior angle brackets when used firming up the “box”. Leaves just enough room to easily slip the bumper unit on and off the frame and wood flexes enough to have tight fit where attached.

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We’ve found that adding 1/4" to the dimensions of the wood (so 1/8" on each side) is enough to accommodate fabric and other layerings but not enough that the bumpers are too loose.


At some events, I saw teams not passing inspection because the gap was to wide (> 1/4"). Some of them passed by adding a thin strip of polycarb on the outside of the frame. The danger is if your frame perimeter is already 119.5" or 119.75", you could fail for violating R3, the frame perimeter rule, depending on how many places the frame had to be padded.


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