Curved range hoods...

[Justin Ludwig]

I'd like to open a learning discussion on building these for those that have or intend to do it.

I haven't built many - people 'round here don't wanna pay for them. I've only built 3 actually. The one I finished today is 50" wide and 38" tall, built for a 9' ceiling.

I design them in SketchUp and them import them to render with my cabinet program for the customer. I use SketchUp to dial in the radii and critique everything so I know it will work. I think there are programs out there (I haven't looked) that will do all this automatically, but I'm not willing to fork over the mullah for rare instances.

1. Build the base of the hood to specs determined by the vent hood.
1a.) Can this be standardized for 30, 36, 42, and 48" ranges? I should think so.

2. Use Sketchup (or math) to build curve and determine radius needed for sides and front.

3. Build a jig to cut the plywood skeleton of the frame. (I didn't take pics, but the skeleton looks similar to this pic [but I use more ribs])

4. Pocket drill skeleton so it's easy to mount to frame later on.

5. Figure out why the corners are a different radius than the front and sides. Anyone know? Math friends? I figure it out by determining the rise and run using scribe marks. But I'd like to know the formula.

6. Preskin with 1/8" MDF. It flexes easily and takes contact cement really well. Sides first - I clamp them to the skeleton and scribe a line to trim on the band saw. I trim +1/8" and use a laminate router with flush trim bit to fit it perfectly. I glue and screw the MDF to the frame by predrilling and countersinking the MDF on 4" centers (I don't want it to move or buckle). Then I do the same to the front. I have to be careful where my countersunk screws are along the edge when using the flush trim bit.
6a.) Flush trim along a curve isn't hard, it just has to be done free hand where only the bearing is touching material. I used a 1/4" shank, 1/2 dia x 1.5" bit. 1/8" MDF doesn't bite, especially if you trim close to your scribe line. Just be careful of the angle so you don't gouge a side or the front.

7. Apply paper back veneer (1/32) using contact cement - same as for laminate countertops. I have to apply 2 coats to the MDF, the first coat gets soaked up. First hood I built using this method had a couple bubble develop (which I stripped and sanded then reapplied with success).

8. I scribe and cut with a box knife +1/8" of the scribe line. After gluing and rolling it, I flush trim with the same method as on the MDF. I buy extra veneer in case I sneeze while trimming.

9. Use a ROS and 180grit paper to sand the edges and everything to denib. The joints are so clean you can see how they were joined.

10. Screw to the base.

I feel much more confident in building these now that I've completed 3. I'll post pics of the final product next week after it's installed and finished. And I'll definitely take detailed pics of process next time I build one.

I'd love to hear/learn about other (better?) methodologies and possible standardization. Even if it involves CNCs.

[Martin Wasner]

I'm curious what you're charging, I'm not charging nearly enough I feel and I get about $1400 on average. I think there should be at least another grand on there.

I'm on my phone and can't post any pictures, but I do it in a very similar way. Bendy ply is a godsend, but I've done a few taking 1/4" mdf cored material and grinding one of the faces off so it has a natural bend to it. When the radius starts getting tight and dramatic, that methodology fails quickly.

I usually use my box at the base to hold the ribs where I want them to be, and cover up the joint with a moulding, if I can. I had one last summer that I built really stupid, and getting the moulding to cover was a nightmare. Fortunately, it was painted, bondo saved me. lol

One thing I do is mix up glue and sawdust into a paste and smear it where my ribs meet the face layer. I don't know if it really does any good, but it makes me feel better.

[Jamie Buxton]

Here's two views of one I built a couple years ago. The kitchen is Art & Crafts style, all in rift white oak. The guts of the range hood was an insert from some high-end source -- maybe Viking? I designed to hood to fit around it. I built the hood with a bunch of bent lamination. The curved panels are made from three layers of 3 mm bending ply, covered with oak veneer inside and out. I laid up the curved plywood over a bending form in a vacuum press, and then added the face veneers in the same press. The curved ribs are also bent-laminated, but I didn't bother with the vacuum press; bending the laminates around a form provides enough pressure to squeeze the laminates together. (It did help that the oak is rift. The grain of the oak makes the glue lines less obvious.) For the panel at the end of the hood, I cut the veneer into triangular shapes, and laid them out like a fan.

IMG_2564 copymedium.jpg

IMG_2565 small.jpg

[Martin Wasner]

Jamie, I'm not sure I've ever seen one like that. That's a neat idea. It's like a window apron.

[Charles B Wilson]

You mean a hood like this?IMG_0323.jpg

[jack duren]

There's a lot going on with those hoods. You have to know A-Z on its construction and the amount of hours to construct it. If your unsure, your in for a lot of late nights....

[Justin Ludwig]

Martin, I charge $1000 plus material. It takes me 1.5 days to build. If I had the shop to myself and didn't have to watch over my help, I could do it in a day. I tell my clients to price them else where and they quickly ask me to do it.

Charles: Yes. I don't crown mine until post installation because the crown usually ties into other cabinets along the wall.

My top nailer is a french cleat. I mount an opposing french cleat on the wall that is 2 inches shorter so I can slide the hood L/R before screwing it. Plus, if it ever has to be removed, only screws along the bottom have to be removed (problems with vents or fans will eventually happen).

I'll take pictures today of the one in the shop I just finished.

The slowest thing for me in the whole process is getting the corner ribs just right. If they aren't even with the front and sides, the 1/8" MDF will turn out wavy.
I chamfer both sides of the rib (3/4" plywood) at 45* so it will slide between the front and side ribs and also slide into the front corner of the base. After I finally figure out that radius, I'll hog the material with a jig saw, flush trim to the pattern jig, then use a bearing guided 45* chamfer bit to clip the edges (if you don't the corners will protrude 1/2 the thickness of the material- 3/8" in my case). The first pass is easy, as the bearing rides the curve. Flip it over and running the other side requires using the pattern jig to allow the router base to ride against because the bearing is now "under" the chamfer from the other side. Sound confusing? If David didn't clean my shop too good last night, I have 4 screw up pieces laying around I can take pics of.

Here's the first one I built- about 9 months ago. I didn't charge her for it (a friend and it was my first). Can you tell I live in rural America? She just loves the colors and old school oak look. Who am I to oppose?
img-5108_3_orig.jpg

[Justin Ludwig]

Here's the guts in SketchUp.

Front
hood front.jpg

Back - I leave rib inset in case I need to scribe along a wall. A block plane will easily clean up the veneer and MDF. The rest of the case gets hit with a power hand planer. Worst case I use a molding to hide stupid wall's gaps.
hood back.jpg

Corner Rib before radius - here you can see how I clip the corners so it slides into fit.
corner rib.jpg

Corner rib with same radius as sides and front - r=48 in this hood. I could not get the front edge chamfered in SketchUp, maybe some one (Dave Richards?) can tell me how to do it without losing faces.
rib with same radius.jpg

Looking down the face of the hood. You can see how the corner protrudes. It's exaggerated by 3/8 because the corner is not chamfer yet on the outside. In the shop, my radius ended up being r=39 7/8 to get everything flush.
down the line look at radius.jpg

[Jeff Duncan]

Wow, all I can say is if you triple your price your still going to be well cheaper than many shops in my corner of the country! Not meant to be a knock on you by any means, just always blows me away how much costs vary in different parts of the country! I don't do much for curved hoods, they're usually shaker style painted jobs and for those I'd start at about $2500 for a simple one.

JeffD

[Mark Bolton]

Wow, all I can say is if you triple your price your still going to be well cheaper than many shops in my corner of the country! Not meant to be a knock on you by any means, just always blows me away how much costs vary in different parts of the country! I don't do much for curved hoods, they're usually shaker style painted jobs and for those I'd start at about $2500 for a simple one.

JeffD

+1. We couldnt touch it for a grand in labor. And we are in the armpit of the universe lol.

[Martin Wasner]

Wow, all I can say is if you triple your price your still going to be well cheaper than many shops in my corner of the country! Not meant to be a knock on you by any means, just always blows me away how much costs vary in different parts of the country! I don't do much for curved hoods, they're usually shaker style painted jobs and for those I'd start at about $2500 for a simple one.

JeffD

It is amazing how varying the cost and price of things are in different places. I'm in Minnesota, and work in south Minneapolis mostly. I work on nicer homes, but they aren't the $20m monsters that are around the lakes.

The coasts are bonkers though. Taxes, space costs, taxes, and taxes. Plus you've got a labor pool that has to contend with those issues, so you have to pay them more. Coincidently, you have to charge more. I'm guessing Justin and I have similar overhead costs being he's in Asspunch nowhere just like me.




I did this one in about a day. I don't think there's even $100 in material. I use 1/2" Baltic Birch for backs in wall cabinets, and I don't have a secondary use for the scrap, so there's usually mountains of it around for making the ribs out of.





This one up and screwed me. The radius was too tight for the idiot way I decided to build it. I wrestled with it for a few days and definitely didn't make any money on it.





I can't find any more pictures of any of the other ones I've done unfortunately.



Justin, me personally, I think you're spending valuable time drawing stuff up in sketchup that you could be using building it. I just draw them out on paper to scale. Front view, and a profile. The overall shape is easy to draw, usually just six lines, and than a hand sketch of any of the details. From there I just wing it.


A CNC could be real beneficial for making the ribs. That gets monotonous and time consuming quickly.

[jack duren]

You have to fair on the prices. You can't just blow up the price, it's only one item. If the kitchen, kitchen and baths has several unusual custom items you can kinda blow up the cost but your competitor may be less.

So far from what I've seen in the pictures aren't that complicated, but as Martin said a tighter radius changes the time frame.

Jeff.....You might get that where your at but you would go broke here in the KC area.

[Jerry Miner]

5. Figure out why the corners are a different radius than the front and sides. Anyone know? Math friends? I figure it out by determining the rise and run using scribe marks. But I'd like to know the formula.

I'll try to explain this, but I'm sure others could explain it better. It's a little like the reason a hip rafter is a different pitch than a common rafter. The rise is the same, but the run is different, because the run is on the diagonal.

If the curve on the front and sides is a circular curve (an arc with a fixed radius, i.e. part of a circle), then the curve at the corner is NOT a circular curve, but an elliptical curve.

Take a cylindrical object, like a hot dog. Slice it straight across, you get a circular cut. Slice it at a 45 degree angle and you get an elliptical shape. Same principal with your range hood. You are "cutting" the curve at a 45 degree angle, so the "hip" cut is an elliptical curve.

To complicate things even further, the angle of the bevel of the corner rib changes from top to bottom. Fortunately, this bevel angle is not critical as long as you get the plywood to take a smooth curve. The math wizzes out there could explain this better, I'm sure.

[Justin Ludwig]

Jerry, your hotdog analogy only needs mustard and a bun. I'm tracking, 100%.

About the price: if Mark is in the armpit of America and thinks my price is way too low, then I'm in the "grundle" (or taint) of America.

Let me elaborate - folks still expect to get raised panel doors in a standard 1/2" overlay (see my Oak cabinets in the pic above), installed, unfinished, no counters, with crown, for $170-$180 lineal foot (that's upper and base cabs). People think I charge a lot to finish cabinets - $50/lineal foot for stain avg and $60ln ft for paint on avg. I actually price them for square foot of face frame and square foot of doors - but to simplify for folks and bidding the aforementioned numbers get real close.

The oak job above had 54 lineal feet of cabinets http://www.ludwigcabinets.com/redoak.html. With everything you see but the countertops, she paid $15050 or $297/lnft. That's cabinets, crown, all hardware, installation, stain and finish.

Most expensive jobs I've done have gone $390/ln ft with no finish or hardware. http://www.ludwigcabinets.com/alder_select.html This job I wish I had finished as it's clear alder and blotched all to hell. He got a crew of Hispanics to paint his 8500sf home for 20k (he supplied material). It shows. I told him my finishing costs alone (material included) would have run him $14k. "Glad I hired those guys" he said.

Whatever. It's all relative.

I only use lineal feet to initial provide free estimates. I have all material costs in Cabinet Vision. I charge "material cost plus 100%". Only thing I don't charge 100% markup on is Blum undermounts, those I charge 50% because they're so expensive anyway ($24pr with 1901 locking devices is my cost). A shaker set of knotty pine or knotty alder will average $160/LF unfinished. The 100% markup covers all the labor and operating costs.

[Justin Ludwig]

Back on topic:

Here's the hood i just built. We'll install and finish on site next week.
IMG_6521.jpg

I'd love to hear about others methods - so I can adopt them or snicker at them.