I've been asked to make a curved kitchen hood, but I have a few concerns

1. How do you miter the edges that swoop down to make the curve? In this case it's painted, so I'm sure I could use 1/8 or 1/4" MDF and overlap it, then use a high solids primer and then won't need to miter

2. If this were a stained or clear finished hood, how do you miter the swoop and would you use kerfcore? I know contact cement on even NBL is a bad idea, but I don't see any other way around it and I'm not sure how to miter the swoop.

See pic. Forget the vertical strips in the center. This is an ideas pic from the customer

TIA for help

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I don't mitre the corners. Paintable I just do a butt joint using a sled to ride on the ribs and cut the skins to fit the front face. I typically use 1/4" veneered material, run it through the widebelt to knock the veneer off one face, which causes the material to naturally curl up.

If stain grade, I do the same, but veneer the faces after the skins have been adhered to the ribs.

Karl,

What do you use to adhere the veneer after the fact?

I've pretty much made that exact hood. Make the rib sub-structure and then use 1/8" bending poplar to cover it. I used yellow glue on the edge of the rib and staples to hold the Poplar down. After I used a PL adhesive on the edge of the rib and the rear of the poplar to doubly sure there was no release. The joint is just a butt with the front face overlapping the side pcs so no gap shows on the front.

Putty and sanding the staples and sanding resulted in a smooth curved surface.

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Or you could buy it from Stanisci Design and know exactly what it cost and sell it for a sure profit.

Bill

Contact adhesive to stick down the veneer.

You want to do just like Leo did and cover the joint between the curved section, and the skirt. That area can get a little gnarly sometimes if you try and get it right to the skirt. Doable, just unpleasant for me

We do it the same as Leo and Karl, Butt joint with plenty of glue... Molding at the seam. We use 1/4 mdf for the faces, pre bend them in clamps and wet the one side down so it naturally starts to cup.

"Or you could buy it from Stanisci Design and know exactly what it cost and sell it for a sure profit."

Or, another avenue. There's likely a shop near you that makes them. You might view them as competition, but they aren't. I try and keep money local whenever feasible. Making friends with other shops has never bitten me either.

I make curved hoods occasionally for other less capable shops. Either because of a lack of bandwidth, or skill set.

I've got a fairly slick, (slick, not perfect), parametric one in my cabinet software that cuts the ribs and framework on the router
My math skills aren't strong enough to know how to cut the hip, but some day I'll figure it out. Right now the ribs that die in space, they are mitred on the cnc and everything falls together so nicely at assembly. Which makes skinning them that much easier.

Curved hoods are not difficult, they're just time consuming and fussy.

Another tip, and this is likely going way overboard. I take a mix of sawdust, (stuff from the castle machine is really perfect for consistency), and make a bog. After the skins are attached, I smear it on the backside making kind of a fillet. Not like the steak, like the weld. I don't know if it's necessary, but it makes me feel better. When everything dries, tapping on it feels pretty solid.

Karl,

Fillets are a very strong way to build structures out of ply that mix flat and curved sections. We use them in boatbuilding. They are typically done with thickened epoxy resin. I don't know if your particle board bog is the equivalent. Sounds a little sketchy. Modern plywood boats can be made by drill holes in the seams. Pull them tight with zip ties. Then do a decent sized epoxy fillet to make a waterproof, super strong joint with no fasteners.

Working on fibreglass catamarans is where I got the idea from.

I don't know about sketchy. It either helps or it doesn't. I don't really see what problems it would create if it didn't help.

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Lots of places make these shipped to your door for 1200-1500 or ish.

I have bought several and they are built just like you are doing except the faces are made of kerf plywood and they have figured out the arc to make the two pieces come together .

The miter is cut at a 45, then fillet with glue . The face seam of the miter is tight, but the back side isn't everywhere. I would guess they cut the parts first with a large v bit and then kerf on the CNC .

Parts appear to be about 300 worth so I would guess that there is about 900 or so on the table to be made . So better have it figured out , or at least systemized with a few basic patterns if one wants to make any money building them .

We have made some in house but they don't really work out money wise . They take too much time. Now we just buy them unless it's really custom and the sell price warrants or.

Regarding the swoop having a 45 deg miter, the easiest way I could see that being done would be on a 5 axis CNC . I unfortunately don't have access to one.

We all know what a horrible idea it is to use contact cement, even on NBL, especially on painted jobs.

Karl,

I ment that your bog may or may not work( ie sketchy). Epoxy fillets will 100% work. So, why use glue/wood bog? It’s not rational.