Finial Chiroptera

This is a finial for Halloween fences made from PVC pipe. This particular model is shaped like the head and wings of a bat.  For other finials and miscellaneous Halloween parts I might post, check out my Halloween Collection.

See below for detailed instructions.  In particular, be sure to take note of the "Pipe choice and scaling to other pipe sizes" section, as you will need to size this part to the pipe you are using.

Notes:

Though the wings look fragile, I've found that they are surprisingly durable, with all of my finials surviving weeks of outdoors exposure for multiple years (in temperatures ranging from 95 Fahrenheit to nearly freezing) plus some not-particularly-careful storage and handling in the off-season.  It was over five years after printing them that one of my four finials lost both wings (my fault), and the original print finally lost a wingtip that had been sticking around despite being partly fractured nearly the entire time.

Layer height is not terribly important for visuals, as the finials aren't usually viewed in great lighting from up close (often from the road and/or at night).  I originally printed these with somewhere between 0.2 and 0.3 mm layers.

I have included multiple historical revisions of the finial, though there's no real reason to use the older v1 version.  

There are two files for each revision.  One of these files includes built-in supports for the wings and chin.  The other file is a clean version (e.g. for resin printing, or just for adding your own supports).  Both of the v1 models also had a built-in support inside the base of the finial to support the roof of the pipe opening.  I have removed this on the v2 model, as it is not necessary due to a change in the internal profile.

I've found that the support inside the v1 base tends to stick to the build plate as you remove the part.  If it doesn't, you can break it off manually after printing if you like, or even leave it attached. It should still fit inside the PVC pipe.  However, note that it will be in the way if you want to secure the finial with a long screw through the pipe, so removing it may be desirable (or the screw insertion may break it off).

What is this for?

Faux wrought iron Halloween fencing can be made out of PVC pipe (see the Instructables link at the start of this description), and is both decorative and functional (it discourages cemetery vandalism and keeps enthusiastic ToTs from traipsing straight through your yard and possibly tripping over hidden electrical wires, gravestones, and other decor).

However, the tops of the fence posts often present a problem. You can order plastic finials online, but they come with square bases that don't work very well with the round PVC pipes. The usual solution is to soften the PVC with a heat gun enough to force the finial onto the end, squaring the circle of each post by essentially shaving off the curved sides. This is labor intensive and not terribly safe (aside from the possibility of burns, PVC is likely to give off toxic fumes when heated like this). And even then you aren't done; securing the finial usually requires drilling a hole for a screw for each post because they resist gluing.

I thought it might be better to design a finial that is printed with plastic that may be more glue-compatible, simply slides onto the end of the pipe and can be secured with a friction fit or screw holes designed right in.

If you are doing this just before Halloween, it is not terribly practical to try to individually print every finial for a full run of fence, but it can be done if you start early enough or you only need them for certain posts like I do.  These finials took a little over six hours each to print at the default scale on my old machine, but I only needed four of them for the amount of fencing that I originally built (five sections, with these finials on the middle four posts, and lanterns on the two larger corner posts).

Decoration Ideas

If your fence is situated so that car headlights will shine on it or ToTs carrying flashlights might shine on it, then you might consider cutting small pieces of retroreflective material and gluing them in the eyes as shown in my photo.  This would make the eyes flash red (or whatever color you used) as the light hits them at the right angle.

It is concievable that one could modify the model to hollow it out and add holes for inserting LEDs in the eyes instead, but that would likely require printing the finial in halves that get glued together afterward.  I'll leave this as an exercise for my fellow haunters for now.

Also, I like using something like Modern Masters' oxidizing Rust paint to make the finials look old.

Pipe choice and scaling to other pipe sizes

You can use the finial with either schedule 40 (white) or schedule 80 (grey) PVC.   Note: Black schedule 40 also exists, and could save you some painting, but it's more expensive and harder to find.  It won't matter which of these standards you use. The outside diameters are identical; only the inside diameters differ between the schedules. Since the finial fits over the pipe like a cap, we only care about the pipe's outer diameter. 

Schedule 80 is sometimes cheaper than schedule 40, but it also comes with a short flare on one end for connecting the pipes together.  You have to cut that off, so you'd lose a few inches of the pipe's length.

This finial was designed to fit a 3/4 inch PVC pipe (see below), which I chose as a compromise.  You will need to scale the finial up or down from its default size if you want to use it on ½ inch or larger pipe.   It's common to use 1/2 inch PVC for most of the fence posts, but to use some larger diameter pipe as the posts between each section of fence.  My particular fence has these finials on the latter posts, which are made of 1 inch pipe, but my original printer was not large enough to print this model at the height necessary for a 1 inch scale, so I actually use my PVC fence adapter to fit the 3/4 inch version of this finial.  Doing that also adds a bit of elaboration to the design.  (On top of all that, I also have 1.25 inch PVC at the corners of the fence.)

If you want to test the scale factor that you intend to use on the actual finial (or just want to test the fit of the part), I have included a test ring that you can print much more quickly.  You should be able to slide it on without too much effort, but it should offer at least a slight resistance to being removed.  (The snugness is less of a concern if you intend to hold the finials on with screws, as long as it fits on the pipe at all.)  You can also generate your own ring by printing only the first few millimeters of the base of the model, either by cutting it in your slicer or by aborting the print after it gets tall enough.

Some things to keep in mind are that…

1. You are scaling to fit the model to the new pipe's outer diameter (plus a bit for tolerance);
2. The common name of the pipe (e.g. “3/4 inch PVC”) is its “nominal” size, which bears little resemblance to any actual measurement you'll get off of it; and
3. You will need to compensate from an "ideal" scale factor to keep the tolerance more or less constant.  See below.

Here are a few thoughts on compensating for the most common scales, based on my testing:

• 3/4 inch pipe = As shipped, this model's base and the test ring have an Inner Diameter of 1.08 inches (27.432 mm). This equals the pipe's standard outer diameter of 1.05 inches (26.67 mm), plus a designed clearance around the pipe of 0.015 inches (so 0.03 inches total difference, or a bit more than three quarters of a millimeter). That clearance seems sufficient for a relatively snug fit.  Of course, printed parts have some dimensional variance depending on calibration and material, and the pipe also has some accepted variation, so Your Mileage May Vary.
• 1/2 inch pipe = 0.84 inches O.D. - The exact scaling factor from 3/4 inch to 1/2 inch pipe is 80% (0.84 / 1.05).  The actual number that you will need to scale the model by will probably be slightly larger than that.  That's because we'd ideally keep the tolerance constant, but scaling down shrinks both the model AND the tolerance.  This means the part may not fit on the pipe if you go all the way down to 80%.  81% is a good starting point for testing as that seemed to fit snugly in my tests.
• 1 inch pipe = 1.315 inches O.D. - For this, we have the opposite problem.  The scaling factor from the included model to this pipe is 125.24% (1.315 / 1.05).  The actual number that you will need to scale the model by will probably be slightly smaller than that.  That's because we'd ideally keep the tolerance constant, but scaling up increases the size of both the model AND the tolerance.  This means the part may be too loose on the pipe if you go all the way up to 125.24%.  I'd suggest starting around 124% to 124.5% as 125% was still a bit loose in my tests.

Version History

• 2023-10-19: Models placed in folders as per version.  v2 models posted.  The new version makes the built-in support inside the base unnecessary due to a change in the profile to a conical shape, the same as my recent update to Finial Tetra.
• 2023-10-03: First upload of Chiroptera.
• 2016-06-24-ish: Original model created