My wife gave me the basic guidelines for a
planter box she wanted me to build. First,
keep it cheap. Second, she wanted an "L"
shape. Third, she provided some rough dimensions.
The design was up to me. Logic
seems to abandon me when I design something,
and this project was no exception. A
nice, straightforward box with square corners
should have been the default. But after some
doodling on paper, I decided to build a planter
with flared sides and rounded corners.
First, the inexpensive part
I looked around my shop and found a scrap of
¾" treated plywood left over from another
project. This made a good bottom for the
planter. I found enough ¼" lauan plywood to
make the sides, and I made the molds for the
curved corners from an empty cardboard shipping
tube. As for the design, I decided on a
flare of 15° for the sides and a radius of 2⅝"
(the radius of the shipping tube) for the corners.
On the sheet of ¾" treated plywood, I drew
the "L" shape, using the dimensions specified
by my wife. For the round corners, I used the
cardboard shipping tube to lay out the curve.
The edges of the plywood base have a 15°
bevel to provide the flare for the sides. I cut all
the straight line sections on my table saw and
sawed the round corners with a saber saw set
at a 15° angle.
I ripped the ¼ lauan plywood into pieces
about 15" wide (tall) to make the sides of the
planter. Because the sides are leaning out 15°,
the plywood sides are wider at the top and
narrower at the bottom. I set the miter gauge
on my saw to 75° to cut the ends of the lauan
pieces. These pieces were glued to the 15°
bevel previously cut on the bottom piece with
a uniform gap left at the corners. The sides
were also filleted to the bottom to provide additional
surface area for the glue joint.
The gap at all the corners would be filled by
laminated fiberglass; however, I needed a temporary
mold to bridge the gap between the
plywood sides and give the proper curved
shape to the corners. I sawed sections of the
shipping tube long enough to be used as male
molds. I applied packaging tape to the cardboard
for mold release, but cooking parchment
paper or waxed paper would have
worked just as well. I cut the bottom of the
tubes to approximately 23°, so they rest on the
bottom piece. Masking tape secured the sections
of tubing at the top and one drywall
screw in the bottom (Photo 1).
|1-The planter began as sheets of ¼" lauan plywood temporarily connected by sections of 5¼" diameter cardboard shipping tube at the corners. The shipping tube held the plywood sides in position while acting as a mold for laying up permanent fiberglass corners.|
I applied a thick mixture of WEST SYSTEM®
epoxy resin and 410 Microlight™ filler to the taped surface
and applied 6" fiberglass tape to the wet mixture.
I smoothed the fiberglass with my hands
to distribute the 105 epoxy resin and 410 filler evenly below the
cloth (Photo 2) and applied neat epoxy to finish
wetting the cloth. After allowing the
coated fiberglass to cure, I feathered the edges
of the tape and applied one layer of 6 oz cloth
to the entire outside of the planter, followed
by several coats of neat epoxy to fill the weave
of the cloth. This layer of cloth ties the entire
box together (Photo 3). When the epoxy
cured, I faired the outside of the planter with
lots of sanding. I drilled several ¾" drain holes
in the bottom (Photo 3) and later glued on
wood pads so the planter would have a little
air circulating under it (Photo 6).
|2-The ¼" gap at the edge of the plywood sides was filled with thickened epoxy. A layer of glass tape was laid over the corner and smoothed into the thickened epoxy. The glass was then wet out with epoxy and the edges were sanded smooth when cured.|
|3-After the mold/tubes were removed, a layer of 6oz cloth was applied to the exterior. Holes were drilled in the bottom for drainage.||6-Blocks were glued to the bottom for air circulation and the sides were glued to the trim.|
At the top edge of the planter, I trimmed the
excess fiberglass and ground the corner pieces
even with the plywood edge (Photo 4). To prevent
moisture from attacking the plywood, I
coated the inside surfaces with a couple of
coats of epoxy.
|4-Excess glass was trimmed flush with the edge of the plywood, and the interior was given a couple of coats of epoxy.|
|5-The top trim was made from redwood with cedar corners. The square cedar corner blocks were fastened to the end of the redwood strips with biscuits. The blocks were later trimmed to shape and the edges of the entire trim assembly were eased with a round-over bit.|
Next, I fabricated and installed the top trim
that covered the raw edges of the plywood
and fiberglass. It was made from redwood
with cedar corners for contrast (this was the
one area where I departed from my wife's
original specification of "cheap"). To
rough-out the trim ring, I cut square corner
blocks and fastened them to the end of the
redwood strips with biscuits (Photo 5).
The square blocks made installing the biscuits
much easier than trying to work with rounded
corners. The blocks were later rounded with a
saber saw and the edges of the entire trim assembly
were eased with a ¼" radius
round-over bit. Epoxy fillets fastened this assembly
to the planter sides (Photo 7).
I coated the top of the planter with 105 epoxy resin and WEST SYSTEM 207 hardener and then varnished with
3 coats of Captain's™ 1015 Spar Varnish. The sides were painted with the house paint I use on the trim of my house (Photo 8).
|7-When the planter was properly positioned, the sides were attached to the trim with short fillets.|
|8-The finished planter. The trim was coated with 105/207 epoxy and finished with spar varnish.|