N. Gilbert 12/2006
If you have lots of time and
patience, and want to add a unique look to your scale crawler, try this.
The soft top shown here was built for a HPI Bronco body, but the technique
will work for any style of pickup body.
First step is to make the frame. I use 3/32” copper-coated welding rod for most of the frame. It’s cheap, readily available, and easy to
form. It also comes in 1/16” and 1/8”
sizes if you need it. I clamp a piece
of 1/4" steel rod upright in the vise and use it to bend the steel around
so I get a nice uniform bend radius on each piece. I TIG weld my frames together, but you could just as easily braze
it. Whatever works best for you. I test fit each piece on the Lexan body first,
then remove it, clamp it in position and weld it. Then back to the body to fit the next piece.
Expect to spend about 10 hours on the frame.
- Start by bending a piece to go around the bed area of the
body, then bend another piece to match the back side of the cab. These two pieces will define the rest of the
frame, so get them right. Next, bend
a piece for the tailgate end of the frame.
Weld them up.
- Now add in some cross pieces and diagonals for bracing.
The frame will need to survive many rollovers without bending, so triangulate
as much as you can. Be careful not to deform or twist the frame
as you add pieces. Continually check
the frame against the body to see that it fits (let it cool before touching
Lexan!).
- Add a hoop over the cab area and fill in the top areas with
supports to stop the fabric sagging.
- Add mounting points in the corners. Here I used steel plates with small screws
welded in from above.
- Similar arrangement at the front but with the screw heads
ground flat so they don't protrude into the fabric cover.
- Once the frame is complete, file any sharp edges down and
paint it.
- Now it's time to make the fabric top. I use ripstop nylon because it has a scale
appearance, but there are other fabrics that will work just as well. I put the shiny side of the fabric to the inside,
as the duller side looks more realistic on the outside. Cut a piece oversize and place the frame on
top, as shown. You will need to mark
the frame and window locations with a silver pencil or similar fabric marking
pencil. Since you don't want the marks
to show when it's done, start with the fabric flipped over (i.e. the side that will eventually be on the
outside is currently on the inside).
- Using small paper clips, pull the fabric tight around the
frame as shown. Try to get all the wrinkles
out and make sure the directional weave of the fabric is lined up with the frame.
Take your time with this step, as errors here will show up later.
- Fabric should fit tight and square. Don't trim the fabric at this time.
- Mark all the edges and frame intersections with a silver
pencil or similar fabric marker. This
is mostly for alignment later when you attach the fabric to the frame, but will
also help in locating the window cutouts.
- Mark out the window cutouts using a ruler. Again, take care here as crooked lines will
show later.
- Your fabric should now be lined out as shown.
- Remove the fabric from the frame and lay it out on a flat
surface.
- Lay a piece of window plastic over the fabric and mark out
the window size using a ruler and a Sharpie.
Windows should be about 1/4"-3/8" oversize. I use 0.010" thick vinyl sheet for the
windows (this was purchased from the local Ace Hardware in the storm window/screen
section).
- Cut out the window. Repeat
for all the windows.
- Apply 1/2" wide double-sided tape around the window
opening. The inside edge of the tape
should be exactly on the line. Getting
it exact will make the following steps easier, so take your time. Note: if your windows are very close to the
frame (less than 1/2"), you may need to trim the tape narrower so the tape
doesn't get between the frame and the fabric and leave an unsightly lump.
- Cut out the window opening leaving 1/4" excess all round.
Cut a diagonal slit into each corner.
- Fold each edge over so it sticks down to the tape. Again, take care to get the edges straight.
- When all four edges are folded over, it should look like
this.
- Now apply another round of double-sided tape over the top
of the first round. This will sandwich
the fabric between the tape.
- Place the pre-cut window over the opening and stick it down.
Make sure there are no wrinkles and everything lays flat with no distortion.
- Flip the fabric over and check that everything looks good.
At this point, the tape will hold the windows in place until they are
sewn in later.
- Repeat for all the windows.
- All windows taped in place ready for sewing.
- The next steps take patience and some tough fingers. Using a needle and some heavy gauge thread,
sew around the perimeter of each window. I
use a backstitch so the stitches look good on the outside and have good strength.
Use small stitches for best appearance.
This takes time and patience (about an hour per window), but it's worth
it when it's done.
- It should look like this on the outside when you are finished…
…and like this on the inside.
- Now that all the windows have been sewn in, place the frame
over the fabric and align it using the marks you made previously. Note: the fabric has the correct side facing
out this time.
- Using clips again, wrap the fabric around the frame and get
it tight and square. Once you are happy
with how it fits, unclip one edge at a time and glue the fabric to the frame
with thick CA glue. Don't use too much
glue as it can soak through the fabric and leave a shiny mark that's impossible
to remove. Again, take care here to
get it right. Once the fabric is glued
in place, it's very hard to remove it to correct any errors without destroying
all the work you've put into the fabric. One thing to keep in mind about fabric tightness - ripstop nylon
expands when it gets cold and shrinks when it gets hot. It's best to do this step on a cold day so
the top will be tight on hot days. If
you fit it on a hot day, the next time it gets cold it will look like a prune.
- After the glue has set, trim the excess fabric off along
the glued edges, but leave the corners for now. It should look like this - almost done. All that remains is to finish the corners.
- Trim the excess fabric leaving about 1/4" remaining.
- Using a small flat screwdriver, push the excess fabric inside
the top.
- Now sew the corner together from top to bottom as shown.
Again, smaller stitches look better.
Keep the corner tight as you sew it, but try not to cause any distortion
to the fabric.
- Finished corner seam. Now
do the other side.
- Trim any excess fabric and tidy up the edges.
- A finished soft top.
- Mount it to your body and go crawling.