Question about bumper materials

Is MDF allowed for bumper backing? The rules read as followed, R31. A.

“be backed by 3/4”… plywood or solid, robust wood."

Does MDF count as “robust wood,” since it is sawdust??

Regardless of whether it’s explicitly allowed, I’ve heard pretty poor reviews of MDF on CD.

Exhibit A

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I believe MDF is a type of particle board ( just with very small sawdust particles) and thus would not comply with the rule.

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Mfd is not plywood, nor is it a “solid, robust wood”.

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We built our bumpers out of HDF in 2016.

We had to rebuild our bumpers at our regional.

If HDF wasn’t allowed, MDF certainly wouldn’t be. My 2016 team shirt still has white paint on it from painting the numbers on Thursday! (I agree with the call to make us rebuild with 3/4” plywood because that was specifically called out in the rules.)

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As an old carpenter, I can tell you that MDF is a very poor choice for bumpers. First, it certainly violates the “no particle board” rule. Second, it is not very good for something that needs the kind of strength properties that a bumper does. Third, it is very difficult to fasten properly, even if you use something like metal corner braces to hold it together. Lastly, it’s very heavy for it’s size and there is a 15lb weight limit on bumpers this year.

My suggestion for good bumper wood is to use 1x6 poplar board, which is readily available at most home improvement/hardware stores. It’s already 5 1/2" wide and 3/4" thick, so all you’ll need to do is cut the sections to length. It joins very well with nothing but wood screws and glue, being better in this regard than 3/4 ply. Finally, it’s almost as light as pine (and lighter than most 3/4 ply) but very strong, so you won’t have any problems with the structure of your bumpers. And, of course, it’s solid wood and thus completely legal.

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As an RI, I would not pass MDF or HDF bumpers.


As another RI, I would also not pass MDF or HDF bumpers.

I use MDF as a cheap laser cutter test material. Don’t use it, it’s not strong enough to function as a decent prototyping material. I know from personal experience with replacing MDF board that broke on a complex prototype. ~2 days fixing the prototype due to using a bad material choice.

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