How to reduce frame "twisting"

[Damion Bevacqua]

Hi everyone,

I recently built a variation of the clamp rack that was featured in fine woodworking a while back... The one with multiple hinged racks:



The problem is that the sections of the rack are sagging. At first I thought it was the hinges or the frames sagging, but it appears to be the frames twisting under the weight of the next frame.

I did build the frames slightly different from the example - mine are constructed using pocket screws and I glued and nailed a piece of pegboard on the back of each section. Also, I used plywood.

So... What do I do to strengthen the frames to prevent them from twisting? I can usually visualize something like this, but frankly I thought the pegboard on the back would help prevent this...

Any hints?

- Damion

[Thomas Bank]

I also would have figured that the backing would have added rigidity.

Are you saying that you used plywood instead of hardwood for the frame, though? That would be an issue. Plywood is... well... pliable. It isn't going to be as structurally stiff as a piece of hardwood of the same size.

[Brian Tymchak]

Damion,

Would it be possible to post a picture showing how its sagging? I'm having a hard time visualizing the issue. Also, maybe include some details about the joinery.

Somehow I missed this project in FWW. I'm going to go back and check it out since I need to build a clamp rack myself.

Thanks, Brian

[Prashun Patel]

If it's racking with a rigid back, then the back's fasteners have to be slipping, no? How about making a more rigid back out of 1/2" plywood that's glued and screwed?