Laminate Bending Lesson #1

[Julie Moriarty]

I've seen countless examples of beautiful bent laminate projects and have wanted to do something like that but lacked the confidence. I was recently challenged with creating a bowed front for an over-the-cooktop piece with recessed puck lights. My first response was, "Do you know how hard it is to bend wood?" That was my way of saying I don't want to go there.

Last night I pulled a piece of jatoba that has been sitting in my shop since the stone age. It was 5/4 and about 4' long by about 4" wide. I figured "why not give it a try?" and resawed it to about 1/8" x 4" strips. I planed as I went along. Before I knew it I had (6) ~3/32" strips and they bowed very nicely. BTW, I don't have a steam bender.

I took two of the old kitchen cabinet doors and cut a bow in them, then spaced them about 2-1/2" apart with some "processed" 2x4's. The old cabinet doors are flat laminate and a little less than 3/4" thick. Thinking I had just created a great form, I glued up the strips and clamped them in between the forms. I was SOOOO proud of myself.

This morning I anxiously go down to the basement to see how my first bent laminate project turned out. When I loosened the clamps, the piece lost some of it's bow. I didn't expect that. Then I removed the piece and :eek:. There was two long cracks in the middle of the outside piece. Glue had oozed partly through them and the crack bulged out. It was then I learned my first lesson in bending wood - Your form has to fully support the wood, side to side, end to end, and top to bottom. Don't expect two 3/4" edge pieces to form the wood in the unsupported center.

I ended up taking a belt sander to it to smooth it out. The bulge was so bad in one area I sanded right through one of the strips.

I beefed up the forms and glued 3/16" plywood on the inside. It's clamped as we speak, waiting for the glue to set. Hopefully. this will solve the problem. I'll be gluing another strip over the one I sanded down once I'm confident the beefed up forms are ready. Fingers crossed!

[Julie Moriarty]

This is a picture of the end of the form. You can see the lack of any support in between the two 3/4" laminated forms and how the end is bowing out in the center of the piece. It was like that for about 3/4 of the length.

http://i867.photobucket.com/albums/ab233/jules42651/Woodworking/Kitchen%20Cabinets/oldbowform_zpsf536beb0.jpg

I added support blocks along the bow edge and then capped it off with plywood. Then I glued on a strip of jatoba (that somehow didn't get glued last night) over the piece I made yesterday.
http://i867.photobucket.com/albums/ab233/jules42651/Woodworking/Kitchen%20Cabinets/newbowform_zpsbef4f5d8.jpg

Top view:
http://i867.photobucket.com/albums/ab233/jules42651/Woodworking/Kitchen%20Cabinets/bowlaminate_zpse3994d4b.jpg
The piece of glued-up sapele at the top of the picture will be cut to the shape of the bowed laminate. The puck lights will be recessed in the sapele panel.

[Jeff Duncan]

Well your on your way now! A couple tips for future glue-ups....as you already learned you need to fully support the piece your bending, there's a LOT of stresses involved even on mild bends.

When you mention the piece lost some of it's bow, that's called springback. The fun thing is it will vary to a degree depending on the many factors involved with bending, though can sometimes be minimized using a stiffer glue. Another way I sometimes get around it on edge curves, (wouldn't work for your face curve), that's a bit easier is to glue up oversize and not worry about springback. Then I'll use a template and route the final curve from the glued up blank.

Another thing to keep in mind is how the piece will be used and seen. In a project like this I might have made the bend out of bending ply and added a 1/8" strip of your wood for the finished face. This gives you the same look in a cheaper and more stable form, while leaving more of your valuable wood for other projects;)

good luck,
JeffD

[John TenEyck]

If you're going to do any amount of bent lamination work, buy or, better yet IMO, build yourself a vacuum bag set up. You only need one mold and figuring out how to clamp something is no longer an issue. Thin laminations and urea formaldehyde glue greatly reduce spring back.

John

[jim gossage]

Yes, use a stiff glue like urea. There will be less glue creep and therefore less springback

[Chris Padilla]

Anytime I watched David Marks perform bent laminations, he always used MDF to get the form he wanted and proceeded to build up the form layer by layer with more MDF until he had a solid form of whatever height he needed. He then lined the form with cork and then finally laid plastic/wax paper over the cork. He also used plastic resin glue which dries hard as a rock in order to get minimal springback, as Jim above alluded to.

After curing, he would take a belt sander to grind down the squeeze out of glue to get a smooth side in order to cut/joint. The glue dries that hard...like a rock.

[Dave Zellers]

It looks like you just made one cut in your form plywood and sandwiched the strips between the two pieces (4 pieces w/ top and bottom). The arc of the face in the arch is different from the arc of the back. Ideally, you want to make those 2 cuts to make your form. If my final arch is going to be 3/4" thick, I'll lay out the form with a 1 1/4" gap and use 1/4" mdf on each side to help put pressure on the veneers and keep them flat. Use a stick nailed at the pivot point to draw the arch and you get a perfect layout by moving the pivot point by 1 1/4" for the second line.

I also screw the plywood to the "processed" 2x4's taking great care to square the top and bottom to each other. Then add some blocks that just touch the tangent of the arc to provide support to the middle. Plus, if you have to use a glue like Titebond you can reduce spring back by leaving the form clamped for a week.

[Roger Rayburn]

I'm with Chris. It's impossible to have too many electrical outlets or too much chrome on a motorcyle. It's also impossible to use too much MDF to create SOLID bent lamination forms that support the entire structure. I wax all of the form that even MIGHT come in contact with the glue. I don't have a steamer, so I soak the strips for as long as it takes to get them to bend to the arc "comfortably". I also clamp the parts in the form overnight without glue so that they sort of want to hold their new shape. That gives me some recovery room if something cracks or otherwise fails to cooperate. (It's a hobby for me, so I don't have deadlines). The next day I apply the glue. They are still pretty damp at that point, so I use urethane glue because it doesn't creep and it likes the moisture.

[Chris Fournier]

One thing I've noticed about the form in the picture is that it looks to me like a single bandsaw kerf was made following the desired arc and this single cut produced the male/female portions of the form. For a really good form the male and female portions of the form should take into account the thickness of the lamination. With really carefull construction I have never found it necessary to line the form with a soft material like cork.

[Julie Moriarty]

Wow! Some great replies and information! My only education on bent laminations has been through videos, not how-to videos, just ones that show the woodworker doing the work. One (http://www.youtube.com/watch?v=EBgoDrKO2OI) I saw used some glue that looked like two part epoxy. The other (http://www.finewoodworking.com/how-to/video/the-coolest-cutting-board-ever.aspx) used Titebond III, for a cutting board. I kind of followed the second one for this project.

I laid some mineral spirits on the piece and placed it in front of the sapele panel that I'll be forming to the curve.
http://i867.photobucket.com/albums/ab233/jules42651/Woodworking/Kitchen%20Cabinets/jatoba_lam_zps66b65188.jpg

I'll probably cut down the height of the piece a bit but have to leave enough height for the recessed pucks to fit. I haven't yet decided how far out this will project from the wall. It just has to be far enough to provide good down lighting.

http://i867.photobucket.com/albums/ab233/jules42651/Woodworking/Kitchen%20Cabinets/cooktop_cabs_zpsaa1b76fa.jpg
I'll mount the whole thing between the cabinets in the above picture. I'm thinking (4) down lights to illuminate the cooktop. The cabinet doors and the sapele panel the down lights will be cut into will be dyed the color of the sample panel in the pic. The faces you see in the wall cabinets are pull-out spice racks. I want to bring the sapele-jatoba piece out far enough so the face of the bow center will be plumb with the face of the base cabinet. But I have to make sure I don't block access to the pull-outs and that I leave a reveal on the soffit above.

What I'm not sure of is how I will trim out the bow. All the cabinet doors have a 45 degree bevel on the outer edges. I could do that to the outside of the bow but I'm not sure about the inside. I could also rout in something fancier but I've only got 1/2" to work with.

Any ideas would be appreciated.

Right now, this is kinda what I'm thinking
http://i867.photobucket.com/albums/ab233/jules42651/Woodworking/Kitchen%20Cabinets/CooktopCabLites_zps014f7c4c.jpg

[Jeff Duncan]

I'm just curious, if your installing the piece as shown, where's your hood going to go? I don't know what the codes are for your area, but even outside of them I wouldn't want a gas cooktop with no hood. And that's going to determine how your curved piece works within the space.

JeffD

[Julie Moriarty]

I'm just curious, if your installing the piece as shown, where's your hood going to go? I don't know what the codes are for your area, but even outside of them I wouldn't want a gas cooktop with no hood. And that's going to determine how your curved piece works within the space.

JeffD

The vent is a downdraft pop up unit. It goes up 15", has a 600CFM blower and requires 8" round duct. Our old cooktop was a downdraft where the vent was in between the burners and required only 6" round duct. It worked like crap but it passed inspection. But thinking back, I don't even remember the inspector looking at the appliances.

The work is coming along nicely. I cut the width of the bow down to 3-1/4", put a tiny 45 degree bevel on both the inside and outside and sanded it to 220. then I routed in a 1/4" dado to receive the sapele panel. So far, so good. I really thought I'd be seeing more of Murphy sticking his nose into this project. I'm happy he's been mostly absent.

http://i867.photobucket.com/albums/ab233/jules42651/Woodworking/Kitchen%20Cabinets/jatoba_lam_02_zpsdedff1f3.jpg

The inset in the upper left shows the dado cut for receiving the panel. I'll float the panel in front. There's a 3/8" reveal on the inside of the bow and that should leave me enough room for the recessed puck lights. I don't have any more jatoba from that piece I used for the bow. It's a very different grain from the other jatoba I have in stock. I'll have to resaw some jatoba for the sides and back and hope it blends okay with the bow.

I'm actually enjoying this. :)

[Jeff Duncan]

Ahhhh well that's a different story, I've only done a couple of kitchens with downdrafts so didn't recognize it!

Sounds like everything is coming along and certainly looks good so far!

JeffD