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The chair (design) that will not go away

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Blog entry by FritzM posted 01-11-2008 03:22 AM 5144 reads 2 times favorited 26 comments Add to Favorites Watch

I have been struggling with the final arm rest/leg design of a redwood patio chair, so I thought I would document the process and the progress thus far and as it moves forward (at a snails pace).

First off, when I originally sketched this chair I fell in love. I couldn’t wait to get into the shop and get started. The need was for a set of deck chairs but i really wanted to avoid a straight Adirondack design. I was trying to get a comfortable contemporary look with both a minimal yet substantial feel. As you can see in my sketch, the integral seat/backrest thickness would have required bent ply to achieve the super thin profile. And that isn’t yet in my skill bag. I’d have to work carefully to ensure the thin design was not compromised in the final version. Here is my initial sketch. Crude but a good start.

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Here’s an image showing how I resolved some of the scale issues. This process, as rudimentary as it is, helps me envision the piece in it’s actual size. By no means is it a full mockup, but it allows me to quickly make adjustments to the design and get some real dimensional information before taking it to CAD.

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After working the design out in sketch form, I worked it up in AutoCAD. As an architect, this is the program most familiar to me and the accuracy keeps me honest. I have started working with SketchUp more, but am still drawn back to AutoCAD mainly for familiarity sake. As I developed the design further in CAD, I eliminated the height adjustment and pivoting mechanisms (shown in the sketch), forcing me to really work through the ergonomics and (more honestly perhaps) make the fabrication more feasible and bullet proof. Here are the further developed Cad drawings.

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Once I had the CAD work close I created a part list and cutting diagrams. For the curved back/seat support rails I printed out full size outline drawings to transfer (with good old carbon paper) to the final workpieces for cutting on the bandsaw. Here is a photo showing the full size printout (yep, that’s 8 ½ x 11 paper taped together). Unfortunately you can’t make out the printed lines in this image, but trust me, they are there.

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And here are the rough cut rails.

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Then a bunch of other boring milling took place to produce the 23 slats needed for the seat and backrest. Then it was on to assembly. Yes, that is my dining room table, but the work’s gotta get done and I have no home shop. I was so excited to get this started that I didn’t even bother taking the candle holders off the table….. This picture clearly shows the relationship between the curved support rails (only one of them shown here) , the stretchers locking them together and the slats. I used a bridle joint to connect the back and seat rails into one continuous rail, more on this possible weak link later. Underneath the precarious mock up is the full size printout of the original arm/leg design, more on that in a second.

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Here you can see how the rail supports, stretchers and slats relate in the actual piece. Also, this is a good image to show how I dealt with the visual “thinness” or the edge. By centering the 9” wide support rail structure all you will perceive is the thickness of the slats. Pretty much in keeping with my original sketch.

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Lots of screwin’ and gluin’ plugs goin’ on here.

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Now onto the arm design, the big stumbling block. I don’t have any process photos of the arm fabrication but they are each composed of 5 pieces of ¾” redwood sandwiched and glued together to achieve the thickness. At the connecting ends, the laminated layers are held short or let run long to interlock with eachother to form a multilayer bridle joint (I’m sure there’s a more proper name than that but I don’t know it). In the photo you can see one leg/arm assembled and one disassembled.

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Here is a plan view photo where I’m trying to resolve the location that the chair body will be positioned on the leg/arm.

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Alright, so here’s the dilemma…… I hate the wood legs! In elevation view they looked like a good compromise between aesthetically right and buildable and structurally sound. Well, the structurally sound part is workin’ but they aren’t real pleasing to the eye. They look like two heavy, clunky, unrefined appendages! So as you can see below, it has literally been shelved. The bad part is I’m super pumped about seeing this thing finished.

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So here is what I’ve come up with to get the Patio Lounger back on track. I sketched out a few idea and then put it into CAD to refine it and give it some real dimensions.

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The material will be powder coated aluminum with welded fittings to receive cross bars that will both support the chair body and give the two legs lateral rigidity. That’s my thought anyway…..

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So, in summary thus far, I’ve designed and built a chair body that is quite comfortable and meets my design concept I was going for.

As I mentioned earlier, there is a weak link with the chair body. After gluing up the seat and back support rails with a bridle joint, I wanted to test its strength so I put a moderate amount of pressure on it, and whamo, it blew apart. At the time, I was only testing one individual rail, so I figured that once the two rails were joined with the stretchers and the load was spread more evenly via the slats, it would be stronger. This has worked out so far, but because I have only tested the seat while it is on the ground and leaning against a wall, I haven’t yet given it a full, real world test. If it does fail, the easy solution will be to consider this a mock up and make the final version(s) with hardwood rails.

I will update when I’ve taken the next steps.

Thanks for reading.

Fritz

-- Fritz Oakland, Ca http://www.muegenburg.com (dedicated to my other hobby)



26 comments so far

View Blake's profile

Blake

3442 posts in 3337 days


#1 posted 01-11-2008 04:17 AM

I wish I had your design sense. But I actually found myself really interested in reading about your process. Thanks for chronicling it in such detail.

-- Happy woodworking! http://www.openarmsphotography.com

View GaryK's profile

GaryK

10262 posts in 3451 days


#2 posted 01-11-2008 04:18 AM

Great post! Lots of good information. I have a chair or two on my list of things to make.

-- Gary - Never pass up the opportunity to make a mistake look like you planned it that way - Tyler, TX

View Karson's profile

Karson

35035 posts in 3863 days


#3 posted 01-11-2008 05:07 AM

As I was reading that I thought to my self. What about the base being a reverse curve like a rocker but upside down. That bring the back and the base into similar but inverse curves. Your wooden designs show a flatsided curve. maybe make it more flowing

The arm could then be assembled off a tangent from the base curve and attached to the back as a support.

I’m not a designer. But, that how I’m visualizing it.

Great info.

-- I've been blessed with a father who liked to tinker in wood, and a wife who lets me tinker in wood. Southern Delaware soon moving to Virginia karsonwm@gmail.com †

View Kaleo's profile

Kaleo

201 posts in 3602 days


#4 posted 01-11-2008 11:51 AM

fritz-

This is a great design. I really love it. I wold look into using a finger joint there instead of a bridle. Only because it provides more long grain to long grain glue surface. But other than that it is a beautiful design.

-- Kaleo , http://www.kalafinefurniture.com

View rikkor's profile

rikkor

11295 posts in 3337 days


#5 posted 01-11-2008 11:56 AM

What a fascinating process to watch evolve. Thanks for so much detail.

View Tomcat1066's profile

Tomcat1066

942 posts in 3258 days


#6 posted 01-11-2008 01:50 PM

Very cool design! I’m definitely impressed with your design sense. I was having self esteem issues with my design ability before I read your post. Now? Let’s just not go there ;)

Seriously, I can’t wait to see the finished chair.

-- "Give me your poor tools, your tired steel, your huddled masses of rust." Yep, I ripped off the Statue of Liberty. That's how I roll!

View Mario's profile

Mario

902 posts in 3514 days


#7 posted 01-11-2008 03:09 PM

Thank you for this post, it is nice to see how others work through issues and especially someone like yourself as an architect.

-- Hope Never fails

View MsDebbieP's profile

MsDebbieP

18615 posts in 3623 days


#8 posted 01-11-2008 04:24 PM

awesome.
You sure put a lot of work into the plan and what a great chair!

-- ~ Debbie, Canada (https://www.facebook.com/DebbiePribeleENJOConsultant)

View motthunter's profile

motthunter

2142 posts in 3261 days


#9 posted 01-11-2008 04:47 PM

its amazing how much time goes into a single item to get it just right

-- making sawdust....

View Damian Penney's profile

Damian Penney

1141 posts in 3454 days


#10 posted 01-11-2008 05:04 PM

Very nice chair. For a base/arms I think a triangle would work pretty well. One side on the floor, one side parallel to the seat, and then a vertical piece at the front. Use a bent lamination to get some nice curves on the corners, and it would look great. You’d connect the two triangles with a rail behind the seat similar to how an adirondack is constructed.

Really nice work so far though (and the metal would be cool too, I just like the thought of keeping it all redwood)

Damian

-- I am always doing that which I can not do, in order that I may learn how to do it. - Pablo Picasso

View Harold's profile

Harold

310 posts in 3310 days


#11 posted 01-11-2008 07:32 PM

I think Karson’s idea is really interesting. I like your concept sketch Fritz and the simple base/arm does work well with the back and seat.
Now I hope I haven’t overstepped my bounds but Karson’s suggestion sounded very simple and I sketched up my interpretation of his comments on the curved base. It does compliment the back and seat well and it has a organic flow, which would tie it into it’s surroundings very well. I’m assuming a pool deck or perhaps a lania overlooking the water. karsons idea

I do like the concept and the rough sketch works very well for me. Sometimes I will get distracted by the “how” and begin to make compromises in the design which almost always end badly.

So, thanks for posting this, it is interesting to read how others approach design issues. It really is a help for me personally.
take care,
harold

-- If knowledge is not shared, it is forgotten.

View FritzM's profile

FritzM

106 posts in 3275 days


#12 posted 01-11-2008 08:08 PM

Wow! Thanks to everyone for the feedback and input. I am reminded that this is one of the great benefits of Community. Peers sharing ideas, inciting new visions and congratulating one another for the small victories that keep us invigorated about our craft.

Harold, first off, thanks for blowing my sketching out of the water…... man, you’ve got skills! I love your and Karson’s take on a possible design. Thanks for putting down your thoughts and taking the time to scan & post!

Kaleo, An alternative joinery technique most definitely will help. Thanks for pointing that out as I would like to see the whole seat body remain the same wood.

Damian, it sounds like your idea is similar to Harold’s sketch only rectilinear with a vertical support on the front. I like that idea as it may help accentuate the subtle curve of the seat.

and here I thought I was getting closer to finalizing the thing. one step forward, four steps back :)

Thanks again everyone!

-- Fritz Oakland, Ca http://www.muegenburg.com (dedicated to my other hobby)

View Damian Penney's profile

Damian Penney

1141 posts in 3454 days


#13 posted 01-11-2008 11:23 PM

I also love the base of the Thos. Moser vita chair, which is also done with tapered laminations.

vita chair

-- I am always doing that which I can not do, in order that I may learn how to do it. - Pablo Picasso

View FritzM's profile

FritzM

106 posts in 3275 days


#14 posted 01-12-2008 01:19 AM

Ditto, that’s a great chair!

Alright, here is a rookie question, any references for creating tapered laminations. I get the basic form, glue, clamp of bent laminations, but how do you cut such a thin workpiece appropriate for bending with a taper….? anyone?

-- Fritz Oakland, Ca http://www.muegenburg.com (dedicated to my other hobby)

View Harold's profile

Harold

310 posts in 3310 days


#15 posted 01-12-2008 03:42 AM

I use a tapering jig that I run thru my drum sander, depending on the type of wood you use, a planer would also work if the blades were sharp. My jigs are made from MDF I rip a 3” piece of MDF, this gives me alittle room (1/2”+/-) on each side of the material I intend to taper. I will take two strips that have a line snapped on them that represents the taper I want and then screw these two to the “jig” using the line to achieve the taper. I use my router to remove the material in the jig where the wood will sit. (the router base plate rides on the strips attatched to the sides, acting as a depth guide for the router) After I rmove the strips, I end up with a piece of MDF with a shallow tapered recess. I rip the material I plan on using for the laminations on the table saw, adding a 1/16” or more to fat end to allow for planing and or sanding.(BE CAREFUL RIPPING THIN STRIPS! keep you blade low and use a thin push stick) I don’t use male/female forms because the final thickness of the laminations must be exact, instead I use a steel caul, a suitable piece can be found at HD the 1-1/2” wide x apx 1/4”thick and is 4’ long. I have some pictures I will try and find them.

-- If knowledge is not shared, it is forgotten.

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