Tupuxuara’s wing: the humerus, radius and ulna, part 1

I started the humerus and the ulna-radio pair for each wing (click to see a larger image).

DCF 1.0

I made them hollow, using different techniques.

I printed the four views of the humerus and used them as guides to cut out four parts.


I should have cut them some 20% thinner along the middle (diaphysis), since it has a cylindrical shape. But I did not, so I couldn’t use all four strips of foam. The humerus has a prominent crest on one side so I chose the two pieces which contained it and attached their edges to the piece cut from the “rear” view. I also cut some round strips of foam to use as a guide when shaping the bone.


I glued the three sides together and let them dry. Then I squished, folded, pressed the foam to shape.


It takes some time to dry, and if you start squishing and cutting, the parts may detach. They did! I used rubber bands to keep everything in place and let it dry and started working on the ulna.


Since the bone ends (epyphisis) have an irregular format, I added a thick piece of foam there so I can carve the details out later. I still didn’t add one of those to the other side, near the crest, since I don’t have yet a clear picture of what it should look like.


While the humeri were drying I came up with another idea for the hollow long bones. Why not just roll them? There are some difficulties. The long cylindrical part of the bone (diaphysis) may change shape. It’s section may be round and wide on one end, and flat and narrow on the other (the wing metacarpal is like that). The bone may also be slightly curved. But gradual changes in section width and shape, and bending can be done very easily while gluing the cylinder. I decided to give it a try.


I cut out the whole bone from one piece of foam. Tried to squish it and curl it, but it cracked in several parts and I had to throw it away. I tried it again. This time I squished the foam well before cutting it out and it worked. I was able to curl it all the way.


You have to do all the folding before cutting the foam. It is still not that easy and if it cracks you have to start again since cracks will make it very hard to shape the bone later. When both sides were attached with glue and kept in place with rubber bands and tape, I rolled it a bit more near the centre (the glue was still not completely dry), making it narrower. I also gave it a slight bend. The result compared well with the photos. I can still improve it later in necessary and add any details, since the foam is 5mm thick and can be carved.


Now I have two humeri and two ulnae drying. Time to make the radii.


The radius is not much smaller than the ulna. It’s much flatter so I decided to not use the cylindrical technique to make it. I made a box like the picture below.


Later I will shape it by carving the edges. I used thick foam for the bone edges so they can be carved into shape later.


I also added the bone ends to the ulnae. So here is the result so far: two humeri, two ulnae and two radii.


I still don’t know how to make the other bones. I will try other techniques and maybe I will come up with an optimal one. It would be great if I could buy foam cylinders in different diameters, or if there was some kind of foam tape :).


1 Comment

Filed under Pterosaur #5: Tupuxuara

One response to “Tupuxuara’s wing: the humerus, radius and ulna, part 1

  1. Pingback: Making of a Tupuxuara | The Imaginary Pterosaur

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