Early versions of the DIY Packraft plans can be used to make a packraft with the heat sealable TPU coating on either the inside or the outside of the tubes (see the Fabrics page for definitions of the abbreviations used here), but later versions of the plans and kits (“V2” and later) are designed to be made with the TPU side of the fabric facing out.
There are pros and cons to each approach, depending on what kind of fabric you are using and how you plan to use your packraft. Consider:
Heat sealable TPU coating on inner surface of tubes:
- Woven nylon layer protects the airtight TPU membrane from puncture
- Bottom layer of floor can be made of same pieces of fabric as side tubes, leaving no seam between the tubes and floor on the outside of the packraft
- Woven nylon will soak up water if fabric has no waterproof coating on other side, making it heavier after paddling
- Fabric threads are exposed to abrasion and may weaken over time
Heat sealable TPU coating on outer surface of tubes:
- Slippery TPU coating provides abrasion resistance and waterproofness
- Tie-downs, spray decks, and other accessories can be attached easily by heat-sealing to the TPU surface
- Air pressure could separate TPU coating from woven fabric layer over time if it is not a high quality TPU coating
- If TPU coating is breached, air pressure will be lost even if fabric is not punctured
I have tried both TPU-in and TPU-out configurations and, like the best packraft manufacturers, I have settled on the TPU-out configuration.
Note that any extremely lightweight inflatable boat is bound to develop leaks regardless of how it is put together; even the best name brand packrafts fail regularly, especially when used in moving water, but the nice thing is packrafts are easy to repair. It’s a trade-off between weight and durability. If you want a tougher boat, you’ll have to make it heavier. If, on the other hand, you are prepared to deal with the fact that by paddling over submerged rocks and wood you will occasionally put holes in your boat, then you can get by with a very light packraft.
Finally, note that the thickness and quality of the fabric and coating is just as important as whether the coating faces in or out. Fabrics in the DIY Packraft shop are custom made to our specifications with packrafting in mind; some fabrics available elsewhere have such a thin coating that they’re not even airtight, so it’s important to test samples before you decide where to purchase supplies.