Designing a packraft with flat seams?

[Apope]

I was reading about the latest Anfibio ultralight packraft and something jumped out at me. “The entire boat consists of only three main segments (compared to normally 11 individual segments). This is achieved through circumferential, horizontally arranged seams (instead of several radial seams).”

https://www.packrafting-store.de/Packrafts/Anfibio-Packrafts/Anfibio-Nano-RTC::939.html

 

I did some Googling and I found this guy who designed a minimal packraft using the same idea.

http://blog.hillmap.com/2013/03/designing-minimal-packraft.html

Is it possible to design a simpler, lighter packraft with only flat seams to weld? Definitely the more more complex the shape the more seams, but can you still end up with a modern packraft shape (extended stern, pointed bow)?

Has anyone played with this idea? What kind of CAD software would be needed? I found a technique was developed by Disney in 2014, but can’t find any further resources or instructions. There’s also a plug-in called ExactFlat for Fusion360 but I can’t tell if it will work for inflatable materials.

 

Aaron

• This topic was modified 4 years, 1 month ago by Apope.
• This topic was modified 4 years, 1 month ago by Apope.
• This topic was modified 4 years, 1 month ago by Apope.

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[Apope]

Thanks for the replies and info. I did download Rhino 360 and I’m going to play around with some different ideas. I have no idea how construct longitudinal seams that are as strong as radial ones, but several of the European packrafts seem to use them in whitewater versions, so I’m interested in learning more.

 

 

[kfrosty]

Hi Aaron, I’m interested in what tools people are using as well, but I have some info to add as well.

I don’t think flat seams (sometimes called pinch seams) like in the examples you provided are as strong as the lap seams like in a typical packraft. The pressure is more directly trying to tear the seam apart. Here is a youtube video about seams (for pool toys, but the idea is similar) https://www.youtube.com/watch?v=9F0fjaHhgzo

The other factor with this simple approach is that you get wrinkling which is a cosmetic issue and could affect the drag in the water. Wrinkles might be a more likely spot for holes to show up as well. But that’s just a guess. These wrinkles come from the inflation process causing compression in parts of the fabric. To avoid wrinkles, the final inflated packraft shape should be made of what are called developable surfaces. This special class of surface can be flattened into a flat pattern without warping. Cylinders and cones are classic examples of developable surfaces which is why you see the tubes of many inflatables taking on these shapes.

I’m working on some inflatable designs for fun. I’ve been using FreeCAD for making the 3D shape. You can then inflate the shape in Blender with the cloth physics pressure option to get an idea about wrinkling and the actual inflated shape. Blender also has a Paper Model plugin that says it can make flat plans of developable surfaces, but I haven’t got that to work yet. I haven’t found these tools to be particularly user friendly so I’m hoping someone else chimes in with other inexpensive software packages.

-Kevin

[Matt (Admin)]

The short answer to your first question is “yes,” and the short answer to the second question is “no” – you could make a packraft with only flat seams, but that would be stretching the definition of “packraft”… something like the Klymit LiteWater Dinghy is about as close as you can get.

That Anfibio packraft you linked to has a flat seam around the outside, but the cockpit seams are not flat. I made a prototype like that a few years ago and when it was done I didn’t think it was worth pursuing any further.

[Author]

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