Bending the panel

[kcameron]

Hi Gang,

I had a vendor do the CAD work and send my RV-4 panel to a laser cutter. Then the vendor got it back and performed the bottom bend in his shop. Since this vendor is reputable and has mostly treated me well, I won't divulge the name here.

The problem is that the bend turned out badly. The bend is right at the bottom of the rectangular radio cut-out instead of occurring about 3/16" below it as we had agreed on an as shown on the drawing. This is unsightly since it exposes the metal edge. Also, the bend is uneven so that the bottom edge is bowed up about 1/4" in the middle. I had originally planned to do the bend myself but balked after thinking about the difficulty of getting a clean bend so close to the radio opening. The vendor assured me that he could do it so that's how we went. To his credit, he's not going to charge me after it came out badly. On the other hand, he's reluctant to try again for fear that he might have to absorb the cost again.

So now I've got a couple of choices:
1) Find a local shop that can do the bend.
2) Send a pre-bent panel from Van's to the laser cutter who will charge extra toolgin costs to deal with the bend.

I'd lean toward choice 1 if I knew that the bend is even possible and where to go to get it done. Do I look in the Yellow Pages under "metal bending"?

I'm hoping this august body can lend me guidance.

[N316RV]

I think the bend you are asking for will be a problem for anyone. Bend it before the cutouts are made (or use a Van's panel) or leave the bottom of that cut out maybe a 1/2" higher and remove the material by hand after the bend.

Alan Jackson
Boeing Mech Engineer

[Mike S]

Alan beat me to it-----------bend first, then cut the big rectangular holes.

[noelf]

Assuming you want to keep the panel that you have started with, you can fabricate a right angle doubler that will nest on the inside radius of your panel. Whatever height you end up with for the doubler would require the entire radio stack to be raised that much also. The length of the doubler is whatever you decide, it can be riveted where needed, and the resulting "gap" can be filled and made to disappear.

Or you could fabricate a doubler that nest on the outside radius of the panel. This solution makes the doubler visible for all to see, so to "hide" the issue, make this one long enough to extend the entire width of the panel, and make it look like that is what is intended. You can notch the area for the radio stack, and when the radios are installed, should not be noticeable. The advantage of this one is that if you intend to install any switches on this lower section of panel , this gives you a removeable panel overlay that can be painted a contrasting color with switch labels applied.

If you don't think you can live with anything other than what you had intended, then be thankful that it was the panel and not the canopy and go ahead and get started on a new panel.

[Brantel]

There is no way anyone is going to be able to make that bend that close to those cuttouts after the fact. There is nothing left to clamp to. If it was done on a brakepress with V groove tooling, there is not enough material left on the inside of the form to prevent the panel from doing this.

This panel is toast, bend first and cut second is my vote. They can block the panel up on some tooling to deal with the flange. Or if you leave enough room between the flange and the lowest cut, the head of the machine can clear it with no problem.

[DanH]

<<This panel is toast, bend first and cut second is my vote>>

Me too, and when you lay out the new panel, make the horizontal flange about 3/4" wide. Given the large squared cutout very near the bottom, a narrow-flange panel will be weak. The cantilevered mass of the radio stack will make the bottom edge bow toward you every time you hit a bump.

[tomagin]

The other option is to weld on a strip at the bottom as the reinforcement replacing the bend. Just had a panel made by Experimental Air for my RV-8 with little unused space and an extension in the middle so I could fit two larget displays. The bottom "bend" is welded on.

[kcameron]

I spoke with the vendor today. He's going send me a new panel with the exact same layout as the current one except:
He's going to leave the bottoms of the two large openings 1/2" higher than the final dimension.
He's going to send it to me in the unbent state.

When I get it, I'll bend it myself then open the holes to the final size. Thanks, Alan (who suggested it first). That possibility hadn't entered my mind before. Sometimes, I'm far too much of a linear thinker.

To address some other suggestions:
The current layout took weeks to finalize so I'm not keen on moving anything. Besides, there's not much room for movment anyway.
With the proper bend, I'm not too worried about the panel bowing downward in the middle; even in high-g bumps. That strip of metal will usually be in tension, after-all. That said, the panel will have additional bracing so flexing should be minimal.

Thanks again,

[DanH]

<<..I'm not too worried about the panel bowing downward in the middle; even in high-g bumps.>>

Bowing aft.

[Noel Simmons]

We have designed quite a few panels and have had them cut on the local water jet. We always bend first. The water jet guy has to set the panel up on a piece of 2" foam.

Who is this guy? obviously has never cut RV panels.