Tuesday, November 7, 2017

Trunk Floor Replacement Option

If you've owned a first generation Honda CRX, you've probably had to deal with the fiber board trunk floor that supports the carpet in the cargo area, above the spare tire.  My personal experience with these, after owning three first gens, hasn't been positive.  The factory trunk floors that I have dealt with were all in bad shape, but what can you expect from a large piece of fiber board that's been in the back of an economy car for the last 30 years.  They are susceptible to moisture, stress from heavy cargo loads, and general wear and tear.  My cargo floor finally gave up the ghost after having to support a lawn mower on a 150 mile journey.  Admittedly, that was a tall order for the 30 year old part.  I'm not discrediting Honda's decision on materials here, especially since it does a decent job for most every day cargo needs while not adding a lot of weight to the car, but there is certainly room for improvement.  My goal for the replacement part was to maintain all the functionality of the original part, but it couldn't be susceptible to moisture, dirt, and it needed to hold up better against general wear and tear.  I decided to work with corrugated plastic sheet.  I've worked with the material in the past, creating signs for various purposes, so I had an idea of it's potential.  So here is what I came up with:

-  Two white Corrugated Plastic sheets (See specs in image below)
-  I was able to find these at my local Home Depot (sizes will vary)
-  Cost - $10-15 a sheet

Tools required:
-  Large glue gun (There are two sizes of glue guns at Walmart, get the bigger one) - $8
-  Corresponding bag of glue sticks (as long as they come) - $5
-  Two cans of basic satin black spray paint - $10
-  One good box cutter with a fresh blade
-  One marker
-  Long ruler or yard stick

STEP 1: Trace floor pattern

If you're lucky your factory trunk floor will still be flat(ish) and have its original shape.  For those of you less lucky, like those who have had moisture get into the trunk causing the floor to bend or sag, you'll need to flatten it out.  This may require re-wetting the floor and then sandwiching it between something heavy and flat while it dries.  Once you have a flat trunk floor, you'll need to lay it on top of your sheet of corrugated plastic.  Try to position the floor where you are utilizing the flat edges of the plastic sheet, so you don't have to make as many long, straight cuts.  Once you've positioned your floor on the plastic sheet, grab your marker and trace the outline of the floor onto the plastic.  Make sure to trace the grab hole.

STEP 2: Cut out floor pattern

Yep, you guessed it, once you've traced your shape onto the plastic, get your box cutter or Xacto blade and cut it out.  Make sure you have a fresh blade, it will make a big difference.  Cutting corrugated plastic can be tricky and annoying.  The knife will jump between the lines of plastic in between the outer sheets of plastic.  This makes it hard to follow your traced line especially when following a curve.  Just move the knife slower in these areas.  Also, be conscious of the position of the blade when cutting.  Make sure it stays straight up-and-down so you have a clean flat edge when finished.  You will likely need to do a little clean up of the edges when you're done.

STEP 3: Fitment check

Now that you have your new floor cut out, lay it down in the trunk area to make sure it fits.  When I did it, I had to trim the edges a bit to make it fit cleanly.  Once you are satisfied with how it fits, press on the panel slightly to feel where the spare tire bolt touches the bottom of the panel.  When you locate exactly where they meet, mark the panel.  You'll need this mark later on, for two reasons.  Also, mark where the jack bracket is as well because you'll need to make sure your supports don't interfere with it.

STEP 4Cut and fold supports

Now that your new trunk floor panel is complete, it's time to add some supports.  You'll need to cut out at least three lengths of plastic panel from the remains of the panel you cut the trunk out of, and the other sheet you purchased.  You can add more supports as you see fit, just make sure they don't cause fitment issues when you install it.  Cut these lengthwise along the lines in the panels.  This is very important for the construction of the supports because you will need to cut and fold them later.  Each support can be as long as you like, as long as they don't interfere with the sides of the spare tire well.  The width should be 15 segments (areas between the long lines running across the panel).  Use your long ruler or yard stick to keep your cuts straight.

Once you've cut out all of your supports, you will need to make three cuts to each support to allow them to be folded.  This is where the width of each support comes into play.  If you look at the end of your support, you should see 15 rectangles or corrugated segments.  On one side of the support, cut through only the top layer of plastic along the 4th and 12th segment.  Then on the other side of the support, cut through only the top layer of plastic along the 8th segment.  Once complete, fold the support at each cut (fold away from the side of the cut).  If you look at the end of your support, it should look like  a 'W' or 'M' depending on how you're holding it.  See image below.

STEP 5: Gluing supports to the trunk panel

Now that you have all three (or more) supports cut and folded, you can glue them to the bottom of your trunk floor panel.  If you haven't already, take a moment and plug your glue gun in and let it warm up (don't forget to put a glue stick inside).  Before you begin gluing the supports, first position them on the trunk floor panel where you want them to be.  After cutting and folding the supports, you end up with what looks like four long flat sections connected by plastic webbing.  When you position your supports on your panel, lay the two outside flat sections flat on the panel, and then slide them towards each other causing the two middle flat sections to create a pyramid shape (make sure your supports don't cover the spare tire bolt and jack bracket mark that you made earlier).  Once the two inside sections are both at a 45 degree angle, hold the support in place and use your marker to trace the outside edges of the support onto the trunk floor panel.  You can even get away with just marking the corners if you prefer.  The angle of the center sections of each support is critical to the support's strength.  If the angle of the pyramid is taller or flatter, it loses it's structural integrity.

Now that you know where each support goes on your trunk floor panel and the glue gun is hot and ready, it's time to glue.  Since the glue cools and hardens quickly you will have to glue one side of each support at a time.  Pick one of the outside sections of each support that will lay flat against the panel and quickly apply a liberal amount glue to it.  Then flip it over and press it onto the panel and hold it for 3-5 minutes.  Make sure you apply pressure to as much of the section of support that has glue on it for the entire time.  Repeat this process with your other supports (gluing one side only).  By the time you've finished with the last support, the first one you glued should be dry so you can continue by gluing the second side.  Repeat the same process as the first side but when you press the second side down onto the panel after applying the glue, it's a little bit of a challenge to hold it place while maintaining the 45 degree angle of the pyramid in between.  As long as you use the trace marks that you put down on the panel before, it should be easy to keep a consistent angle across the length of the support.  Repeat for the remaining supports.

STEP 6:  Glue spare tire bolt patch

If you remember from the previous step, I stressed that your supports shouldn't cover the mark you made for the spare tire bolt.  This is because the part of the new floor that comes into contact with the spare tire bolt needs to be flat.  I tested the completed floor without added support at the point where it contacted the panel and it quickly started to compress the panel.  To support this contact point, cut out a small square of the same corrugated plastic sheet and glue it to the panel.  This time, instead of the corrugated lines running parallel like the supports, position the square of plastic so the corrugated lines are perpendicular to the lines in the floor panel.  Once all the glue has dried ( I waited a couple hours to be extra sure ) it's time to test the new floor in the car.  I used two full 5.1 quart containers of oil to test the panel's structural integrity.

STEP 7: Painting

This step is pretty self explanitory.  I'm not going to tell you how to paint because I'm sure you already know how, but just make sure you paint along the edges so there isn't any of the white panel showing through.  It will stick out like a sore thumb when installed in the car.  I used both cans of paint after putting down roughly three coats of paint.  Once the paint is dry ( which I recommend waiting a couple days before putting into your car so it doesn't stink up your interior ) you're golden.

I've been running this new trunk floor design for almost 6 months now and I'm satisfied with it.  It holds up to the rigors of every day life really well, including those rare trips to the hardware store.  I hope it works for you too!


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