Origami chair redesign: a fiberglass exterior

June 16th, 2013 by SLSolarz

Hey, thanks for checking out my blog!  Last week I promised to write about creating the exterior of my chair.  Below, I describe my thought process around editing the seat shape, choosing a color and an exterior finish.  I also discuss the mistakes I made and how I corrected them.

Between layers of fiberglass and resin I sanded from 80-150-220 grit—a mistake.  Because resin will drip, I was limited to applying it only to surfaces that were level.  I then had to reposition the chair and again apply resin only to the level surfaces.  All of the sanding and limits to resin application meant that it took several weeks just to apply one layer of resin to the entire chair.

Between layers of fiberglass and resin I sanded from 80-150-220 grit—a mistake. Because resin will drip, I was limited to applying it only to surfaces that were level. I then had to reposition the chair and again apply resin only to the level surfaces. All of the sanding and limits to resin application meant that it took several weeks just to apply one layer of resin to the entire chair.

First, I needed to ensure that the ergonomic seat I had just carved from spray foam and covered in body filler would be comfortable for any adult.  Minne-faire was approaching, so I decided to display my unfinished chair in order to collect some data about the comfort level of the seat and whether or not I needed to edit the shape.  My carving mistake was quickly revealed:  every woman who tried the seat loved it and every man found the back half of the center ridge too high!  Oops!  Luckily, that was an easy fix.

Second, I considered the color.  I could not decide between bright orange and white so when I invited visitors to try out the seat, I also asked them to vote for a color.  Their choice was clear:  classic bright red!

Throughout the dried, but not yet sanded, layers of resin (the shiny areas in this photo) appeared dozens of small mars and dents—with every single layer.  This was one clue that resin alone was going to be insufficient coverage.

Throughout the dried, but not yet sanded, layers of resin (the shiny areas in this photo) appeared dozens of small mars and dents—with every single layer. This was one clue that resin alone was going to be insufficient coverage.

Third, for a sleek, contemporary look I decided to give the chair a fiberglass finish.  Most of the chair received one layer of fiberglass and 4-5 layers of resin.  The seat and back were coated with 3 layers of fiberglass cloth and 5 layers of resin.  Between each layer I sanded the resin from 80-150-220 grit which turned out to be a mistake.  Each non-final layer of resin should only be sanded to 80 grit so that the next layer will easily adhere.

The extra sanding did help by yielding a perfectly smooth surface before applying the next layer of resin.  However, despite the smooth application surface, each new layer of resin consistently produced substantial mars & dents.  I seemed unable to pour a smooth layer of resin which made me wonder if I was ever going to be happy with the finish.

The white circles in this photo surround dark spots on the seat and back.  Those are not shadows but, rather, the dark green body filler that I used when I ran out of pink body filler.  It is showing through 3 layers of fiberglass cloth and resin.  This was my second clue that fiberglass and resin were going to be insufficient coverage.

The white circles in this photo surround dark spots on the seat and back. Those are not shadows but, rather, the dark green body filler that I used when I ran out of pink body filler. It is showing through 3 layers of fiberglass cloth and resin. This was my second clue that fiberglass and resin were going to be insufficient coverage.

I thought that using fiberglass resin would negate the need to paint the chair because the resin can be tinted with universal pigments (the kind that your local paint store uses).  The hardware store where I bought the resin threw in the pigment for free and I combined them in a plastic bucket.  The resin color looked perfect in the bucket!  But once on the chair I realized that resin is super translucent because it contains no opaque base.  Therefore, the 2 different colors of body filler I used on the seat were very visible, even through 3 layers of fiberglass cloth and resin!

If I ever do this again, I will make sure that the color of my chair before laminating is consistent throughout. With an even-colored base, the tinted resin and fiberglass cloth would have been adequate coverage.  Still, to get a smooth surface I would have to spray the resin rather than pour or brush it on.

The difficulty in achieving a smooth surface combined with the translucency of the resin made me realize that I must paint the chair.  After pricing High Volume Low Pressure (HVLP) paint spray guns ($180), primer spray guns ($50), paint ($100), and the rest of the equipment I would need to do the job myself, I decided to save some money and have my chair painted at an auto body shop ($250).  But this will be my final step and there is a lot more to do before I get there.

Next time, I will discuss the influence of Converse All Star sneakers on my design.

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Origami chair redesign: fixing FLW’s problem?

May 28th, 2013 by SLSolarz

Thanks for checking out my blog post!  As I promised in last week’s entry, this week I will reveal whether or not I solved Frank Lloyd Wright’s design problem.  The Origami Chair famously has a tendency to tip forward; especially as the sitter scoots forward in preparation for standing up.  Wright’s solution was to add anti-tipping feet; he added metal caps to make the extra pieces look more intentional.

This photo provides a good view of FLW's anti-tipping feet.  They are the pieces of ply with the metal tips.

This photo provides a good view of FLW’s anti-tipping feet. They are the pieces of ply with the metal tips.

My thought was to make the front feet larger, providing a greater surface area and, therefore, a lesser proportion of the sitter’s weight on the front corner of the feet.  Good idea??  I originally made the feet about 4″ long (a 25% increase from the FLW model) and then sliced off a couple of inches from the bottom of each side of the chair, doubling the length of the feet.  Result??

I still had a tipping problem.  The seated person wasn’t in any danger but the experience of getting up from the chair could still be a bit startling–not a desirable quality for a chair!

I considered tossing the chair out and moving on to another project until a fellow member of Twin Cities Maker mentioned that a chair with a tipping problem might make a great rocker.  Thus began a new design!

So, next I carved a model rocker out of polystyrene foam.

Here the foam rocker is taped to the table to approximate how it would look once attached.

Here the foam rocker is taped to the table to approximate how it would look once attached. The paint chip that I have taped to the side is a color I considered for the chair.

Determining the arc of the rockers turned out to be quite a research project.  Eventually, I found a simple formula for finding the length of the radius of the circle from which the arc should be drawn.  That is seat height x pi.  I brought my model and 2 tubes to a steel-bending expert.

One of my rockers is finishing its final bend. This machine has a limit of 2 in diameter metal.

One of my rockers is finishing its final bend. This machine has a limit of 2 in diameter metal.

Next, I made several steel plates to screw to the feet and tail of the chair so that I could connect the chair to the rockers.

Positioning the chair, just right, onto the rockers was challenging.  If there is a next time, I will get help holding the chair as I weld it to the rockers.

I propped the chair just as I wanted it to sit on the rockers so that I could design the hardware to connect the front feet.  You can see on the left that I used a plate welded to a square rod to connect the tail.

I propped the chair just as I wanted it to sit on the rockers so that I could design the hardware to connect the front feet. You can see on the left that I used a plate welded to a square rod to connect the tail.

 

Next week, I will discuss creating the exterior of the chair.

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