cutting plywood to fit curves

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andyklier

2004 2800 LONG wheel base
hello this my first post. i just bought a nice 2004 2500 with the long wheel base and i'm converting it into a home. right now i'm buying appliances but i'm out there working on the van daily cleaning it out, moving bench seats around. today i bought some paneling i'd like to use to cover two of the windows. it's 3/16" ply basically. i wanna cut it to fit in the curve of the fascia that goes over the cieling of the van.

any tricks to transferring the curve of a window to a piece of plywood? i have some ideas but wanted to see what you guys have come up with.
 
OrioN

OrioN

2008 2500 170" EXT
andyklier said:
... that goes over the cieling of the van...
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I before E except after C, and sometime Y...

I like to make templates for curves or cutouts out of mdf (1/4" to 1/2" depending on whether I use the template with a trim router to make the cuts) and/or hard cardboards first, to make sure I got the measurements correct and 'tightness'/fit.
 
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geoffs

geoffs

2003 T1N 316CDI LWB
I've found 3mm MDF good for making templates. Thin enough to work with but stiff enough to hold the curve.
 
geoffs

geoffs

2003 T1N 316CDI LWB
Amboman said:
Just like a wooden boat "steam" solves any wood bending problem...
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Spent the day doing just that, steam bending ribs for a boat repair!
Not MDF of course. Apart from not steaming well, I'd get thrown out of the boat shed if I even mentioned the word:bash:
 
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gary 32

gary 32

07 ncv3 pv
andyklier said:
hello this my first post. i just bought a nice 2004 2500 with the long wheel base and i'm converting it into a home. right now i'm buying appliances but i'm out there working on the van daily cleaning it out, moving bench seats around. today i bought some paneling i'd like to use to cover two of the windows. it's 3/16" ply basically. i wanna cut it to fit in the curve of the fascia that goes over the cieling of the van.

any tricks to transferring the curve of a window to a piece of plywood? i have some ideas but wanted to see what you guys have come up with.
Click to expand...
4 strips about 3" wide, 1 for each leg of the rectangle, scribe each to fit, (round corners etc.), then hot melt the corners together to form the rectangle, 1/4" plywood is best.
Draw the rectangle on your finish piece then take the pattern apart clamp and route off each leg (pattern) with a flush cutter, bearing on top.
 
Frosty_1

Frosty_1

Member
gary 32 said:
4 strips about 3" wide, 1 for each leg of the rectangle, scribe each to fit, (round corners etc.), then hot melt the corners together to form the rectangle, 1/4" plywood is best.
Draw the rectangle on your finish piece then take the pattern apart clamp and route off each leg (pattern) with a flush cutter, bearing on top.
Click to expand...
Can you explain hot melting plywood?
 
gary 32

gary 32

07 ncv3 pv
We use polyurethane hot melt glue for strong bonds in 20-30 seconds, that can be dis assembled with a chisel and without destroying the pattern, or are strong enough to stay together on their own for long periods of time.

The first 2 photos show a pattern laying in the fore ground, 1/8" x 1 1/2" poplar ply hot melted together, for the cavity under an NCV 3 passenger seat then the resulting box for a 12" sub and amp box.
 

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N

NBB

Well-known member
If you use a pattern, you are doing the job twice. It might make more sense for something like the speaker box above, less sense for general cabinetry matching curves of the van. The latter will add up to a LOT of pattern making.

I make very rough cuts of the curve, leaving a few inches extra material. Position the piece and use a compass to scribe the line. Adjust the compass to a point where zero material gets removed. You are tracing the curve with the "point" of the compass, and copying that to your workpiece with the "pencil" side of the compass. Do not rotate compass as you trace. After you scribe the line, make your cut leaving still a bit extra material, depending on the complexity of the curve and your comfort level. Repeat process w/ compass as necessary. Sometimes you can use one finished piece to trace on to other pieces. See "My Climbing Rig" in RV write ups for examples of results.
 
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gary 32

gary 32

07 ncv3 pv
NBB said:
If you use a pattern, you are doing the job twice. It might make more sense for something like the speaker box above, less sense for general cabinetry matching curves of the van. The latter will add up to a LOT of pattern making.

I make very rough cuts of the curve, leaving a few inches extra material. Position the piece and use a compass to scribe the line. Adjust the compass to a point where zero material gets removed. You are tracing the curve with the "point" of the compass, and copying that to your workpiece with the "pencil" side of the compass. Do not rotate compass as you trace. After you scribe the line, make your cut leaving still a bit extra material, depending on the complexity of the curve and your comfort level. Repeat process w/ compass as necessary. Sometimes you can use one finished piece to trace on to other pieces. See "My Climbing Rig" in RV write ups for examples of results.
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NBB I respect your opinion, here's mine:

Pattern making and proper space documentation are always challenging exercises.
The best way to document conditions such as a floor to ceiling, wall to wall panel or space with 4 sides fit is a pattern where you can fit one vertical or horizontal at a time.

I have learned enough to respect everyone's opinion but if I am paying and it's my dime your better know how to make and fit a proper pattern. I am still humbled by the challenge of being a cabinet maker for 37 years and custom shop owner for 30. LOL
 
Altered Sprinter

Altered Sprinter

Happy Little Vegemite
Roof is mark and back scribe not that easy.there are other ways such as back measuring with a center axis, and use of boards left to right for accurate cut-outs.Only required for full sheets.
Sides and floors use, Heavy weight paper felt or similar product, that does not stretch or distort.
One paper template is cut out and taped down to a working surface substrate, back scribe with a pencil to mark out final cut.Trace this on to a suitable final Ply MDF composites that's front coated or Masonite [Water proof] and then trace with scribe the template image onto the board, then cut, some planning or sanding will be required on wheel wells and corners.
I can run photos up as availability of time restraints it takes an hour to set up to snap.
Foil:thinking:
Richard
 
N

NBB

Well-known member
The other problem with patterns is that you are stacking up tolerances. I see no value in making a pattern unless you plan to produce many of the same part, and even then the first usable part can be the pattern. If you are following curves in the Sprinter, especiially a wall or ceiling that has a panel installed, and you want less than an 1/8" or so of error on a visible seam, it's unlikely you'll find two cuts to be the same.
 
geoffs

geoffs

2003 T1N 316CDI LWB
One thing I've found does work is a piece of closed cell foam. I had a stack of this in some equipment I got from China recently

This is a template I made of the roof line of the van so I can make a jig to bend some ply to suit. The foam is about 12mm thick and flexible and can be pushed into a curved area if required. I trimmed this bit to a rough fit and then used a felt pen to mark the curve which I then cut to size with a sharp knife. Scissors work well too.
The foam is not expensive to buy but you may be able to pick up pieces for nothing as it's a common packing material these days.
 

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