Polyhedron Model: Pentagonal Hexecontahedron

[Laurence Finston]

This is one of my treasures, my glue pot. I'm sure some of the members of this forum weren't born yet the last time I had it out, I'm sorry to say.

Since it surely doesn't belong to standard equipment for paper modellers, I thought I'd post these photos.

The bag of glue granulate reads "Hasenleim" which literally means "hare glue" in German, i.e., it's rabbit-skin glue. It is by far the best glue I've ever used. Of course, it's not the best glue for every application but for wood it can't be beat.

One thing I can't transport over the computer is the smell: it definitely kind of smells like a decaying, dead animal, but also kind of nice in a way, if you can imagine that. I always enjoyed having the glue pot going in my workshop.

I put some in to soak overnight. In the morning it will be a gelatinous mass and I can put it into the pot and let it melt. I can't remember what proportion I used to use. Tonight I started with 1:1 but that wasn't enough water. It's not sensitive, however. If it's too thick, I can add water and if it's too thin, I just have to let it cook. The pot doesn't boil it, it just keeps it in a nice melted state. You definitely don't want to stick your fingers in it, though.

The temperature doesn't need to be adjusted; you can just let the glue heat all day, if you want. I used to pour the leftovers into ice cube trays and put them in the freezer. They keep for a long time.

[Laurence Finston]

Unfortunately, the idea with the rabbit-skin glue didn't work out. It doesn't set fast enough, it's not possible to clip the faces together and it's too hard to hold them together until the glue sets. I tried some double-sided photo tape, but it won't stick to the dried glue.

I think the best (only?) way of putting the model together is to sew it. I would advise anybody who wants to build it to wait until I've revised the plans accordingly. Unfortunately, there's no way I can "un-paste" the prototype I've been working on, so I'll have to start again. At least it made it possible to discover errors with the tabs, which was its main purpose. However, I would like the plans to be for a constructable model.

This is the first polyhedron model I've failed to put together. However, the others were less complicated and had larger faces and tabs. In addition, I used Bristol board, which was much stiffer, which may have helped.

When I revise the plans, I will also make the faces and as a result the model itself bigger. At its current size, the tabs are so small that stitching might not work.

I'm going to have to look up what kind of stitch I can use and practice this. It may be awhile before this project moves forward.

So, back to the drawing board.

[Laurence Finston]

I have now added markings for stitching the model together and uploaded a new version of the PDF file to the website: https://www.gnu.org/software/3dldf/g...s/pentahex.pdf

Where there is room for a tab, the markings are on both faces that meet at an edge. In addition, on the face that doesn't have the tab, there is a "trace" of the tab in gray. This is just for orientation; the trace should not be transferred to the Bristol board, card stock, or paper. By the way, I recommend using graphite paper rather than carbon paper for transferring. It erases much better.

I have found that toner doesn't work particularly well. It smears when folding and erases poorly. Also, the gray lines on the models don't print very well. For lines that should be cut, scored or folded, I plan to replace them with black lines that I may also make thicker.

I've eliminated the thin, triangular tabs. They didn't work well when folding when using paper for the model and they are so small that making the holes for the stitching probably wouldn't have worked. I have replaced them with markings and traces on both faces, using the same shape as the tabs on the other short sides, and have added a page for separate tabs which can be cut out and used to join them using butt joints. The use of the separate tabs is optional; it should be possible to use a butt joint for the faces and make stitches from one face to the other. However, I think the separate tabs will make greater accuracy possible.

In addition, I have added markings and traces to the faces which are so close together that there were no tabs at all in the previous version.

There are now only two kinds of tab in the plans, long ones and short ones. Because I was able to eliminate the thin tabs, it wasn't necessary to increase the size of the faces and the model.

If paper is used for the model, a needle can be used to punch the holes. For cardstock or Bristol board I recommend a carbide scribe to mark the holes before driving a small tack through the material to make the holes. As an alternative, an awl could be used (for marking, not punching!). I strongly recommend marking them in this way before making the hole.

I will be adding markings and separate tabs (if applicable) to the other models as soon as I can.

I plan to try to salvage the partially-assembled model made of 170g paper. I'll try stitching it together without markings or I may disassemble it and used separate tabs for all the joins that I've already glued.

[Laurence Finston]

By the way, I recommend using stitching together with gluing. The resulting models should be quite stiff and robust, assuming cardstock or Bristol board is used. In addition, small inaccuracies tend to cancel each other out. However, if stitching is used, it should be possible to put the models together very precisely.

I plan on testing this and posting my results. However, I will first add markings for stitching to the other two sets I've plans I've posted here.

For very thick Bristol board, it would be necessary to use separate tabs for all of the edges or to stitch over the edge, as mentioned above. I may add a version to account for using separate tabs and thick cardboard. Thick cardboard makes for a very stiff and robust model but there is a point of diminishing returns with respect to the thickness of the cardboard. I used very thick Bristol board for a project and found that cutting it was very strenuous and tedious and dulled the x-acto knife blades too fast.

[Laurence Finston]

I've now cut the model out, creased it, punched the holes for the stitches and cut out a few of the separate tabs needed for the faces that are too close together for a normal tab. Ready to start stitching the model together.

[Dave Pete]

These closed face models are challenging. Especially the last few faces as there is no good way to hold the under tab while gluing it up. I use a tacky glue which seems to work pretty well and is very inexpensive. Never considered using a needle and thread to pull it together, but that could provide an interesting texture at the edges.

[Laurence Finston]

I'm optimistic about it working. I should know in the next couple of days. I plan on leaving a lot of slack for the last faces and pulling them together from the outside, possibly by using a crochet hook.

I've been using a backstitch and I looks like it might be possible to use this stitch that way. Otherwise, I can just use single threads and knot them all on the front side.

The photos show how the stitches look. Unfortunately, my camera is not too good for close-ups. One of these days I should buy a macro camera.
I'm using black thread to make it easy on my eyes. However, it hasn't been too hard so far and I think using white or light-colored thread would be easy enough, too.

The knots on the reverse where I end the seam aren't very noticeable. They should look alright on the front side, too.

Here are instructions for backstitching: How to Hand Sew a Durable Backstitch

Here are instructions for ending the seam: How to End a Stitch: 10 Steps (with Pictures) - wikiHow

It definitely makes it easier to print out the plans onto the paper/cardstock rather than transferring it by hand. i'm using the 170 g paper and so far I'm happy with the results.

I looked into cutting plotters but it seems that they're only available for Windows and MacOS and I have GNU/Linux. I may be wrong about this, though.

I haven't been gluing in case I have to disassemble the model. It looks like it might not be necessary at all.

[Laurence Finston]

When I use Bristol board, I normally glue watercolor paper to the faces and paint it. The stitches are flat enough so that they shouldn't be noticeable underneath. With the 170g paper, the model seems to be robust enough so that I could glue lightweight watercolor paper to the faces. However, I don't yet know a way of coloring this model and I still have to get it assembled, anyway.

[Laurence Finston]

I got the two halves sewn together. The real test will be trying to close the model.

If you don't know how to sew, don't be intimidated. The skills needed can be learned in a few minutes. It does take a little while to get the hang of it but it's not difficult at all. It's also quite addictive. I've found this with needlework in the past.

For the 170g paper, it would have been better to have tabs that start closer to the edges. The way it is, there are noticeable gaps at the corners. With Bristol board, there's enough material so that wider tabs are probably not necessary.

Unfortunately, it seems like the 170g paper won't make for a model that's stiff enough so that watercolor paper could be glued to the faces. I'll know for sure when it's completely assembled (assuming it works).

The separate tabs that I made for the faces that are too close together for normal tabs were not needed. It works well to just make a butt joint and sew over the edge. It took me awhile to realize that the stitches that cross over from face to face could be on the reverse. This way, the stitches on the front look the same as the stitches on the other faces. I used a ladder stitch: https://www.singer.com/sewing-resour...-reference/218

The version I'd printed out had smaller tabs than the current version. Some of the holes tore and I used cellophane tape to patch them. This worked fine.

A short needle is necessary in order to be able to manoeuver when the model starts curving in on itself. A point isn't necessary. Having stuck myself with the needle several times today, I plan on buying short, blunt needles tomorrow.

[Laurence Finston]

Even though the toner smears, it's a real convenience being able to print out the plans on fairly thick paper. This model has 60 faces and a lot of tabs so it would be quite tedious transferring the lines by hand.

At the copyshop where I went, the 170g paper is the heaviest where it's possible to copy oneself. They do print onto heavier card stock, but in this case the personnel has to do it and there's a fifteen euro base charge, no matter how many copies they print. It would therefore only be worth doing for larger orders, which is too bad.

However, there are a bunch of other copyshops in the town where I live and one of them might offer printing onto card stock at a lower price.

I think a cutting plotter would probably be the best solution, anyway, if I can solve the problem with the operating systems. I wonder whether any of the copyshops have one. The one I went to has a professional device and it's really expensive to have them make cut-outs. The saleswoman couldn't name a price and I asked whether it was in the 10 or the 100 euro range and she told me 100. I saw a standard consumer-level cutting plotter for 300 euros new. I think they're a little behind the times at that copyshop.