When a plastic kayak develops a crack it can seem like the end of the world. Most kayak outfitters will tell you to scrap the boat and buy a new one. The ones that will tell you about plastic welding often won’t do it for you because it is an inexact and messy process that they deem could open them up to liability. This leaves you to figure out exactly what they are talking about and how much the equipment will cost you to do it.
Fret not, you can plastic weld your kayak yourself without the official tools for the job, providing you’re ok with the repair not looking like new when you’re done. Here’s a guide to help you determine if you will be able to plastic weld your own kayak repair.
The Difference Between Linear HDPE and Crosslinked PEX or XLPE
Plastic kayaks are made of Polyethylene, otherwise known as PE. PE is like a magic material that has revolutionized the industries that use this plastic. The very same chemical properties that make HDPE extremely durable and flexible also make it extremely resistant to glues and adhesives, making plastic kayak repairs a real hassle.
The type of PE that is used determines whether or not it can be plastic welded. There is linear high-density polyethylene (HDPE) and there is crosslinked polyethylene (PEX or XLPE). While there are technical attributes of both, the gist of this for plastic welding purposes is that:
- Linear HDPE Can Be Plastic Welded
- Crosslinked PEX or XLPE Can Not Be Plastic Welded
The non-technical reason for this is because existing linear high-density polyethylene will melt and mix with added high-density polyethylene. When it hardens the substance will be one unified material. Crosslinked high-density polyethylene, because of how the materials are chemically connected and bond to one another, will not simply melt and combine into new material. Therefore, any material that is melted into crosslinked PEX will remain distinct from the existing material. So, while you might fill in and cover up a crack, it is not sealed and repaired as one material.
Determine Which, Linear HDPE or Crosslinked XLPE, Your Plastic Kayak is Made of?
So, if you want to plastic weld your kayak, you’ll need to keep your fingers crossed that it is linear hope. Honestly, in most cases you’re gonna be in luck as most plastic kayaks are made of the linear type. However, you’ll want to make sure. So do some research. Start with the company website and go to your model of boat. Under technical specifications, it will probably spell out the material used. In many cases however it might just say HDPE without the type. In that case, call manufacturer and ask. You should also tell them where the crack is and ask for their advice on repairing the kayak. Also ask if the damage is under warranty or if they’re able to help fix it.
If you aren’t able to get an answer to your question, there is another way to tell. If somehow you’re able to get some shavings of the material from the kayak, you can cut them apart and then melt them back together. Yes, this means taking a chunk out of your kayak. But, perhaps you already have some excess material from cutting out a hole and installing a kayak hatch, for instance. Otherwise, the kayak cockpit combing is usually a spot with thick plastic that wouldn’t be highly compromised by shaving off a few slivers.
Place a flame next to the two pieces of plastic you want to melt together and heat them up. You don’t want the flame to touch the plastic, but rather simply heat them up. Using a screwdriver you can work the material together and into each other. If the plastic melts and rehardens together, congratulations you have linear HDPE. If the material does harden but remains distinct from each other, you’re out of luck and you probably have the crosslinked kind.
Determine Your Next Steps
So, once you know what type of HDPE your kayak is made of you are ready to move on to the next step. If it’s linear, it’s time to gather the needed materials and plastic to weld your kayak. If your kayak is Crosslinked PEX or XLPE, you’re not out of luck yet. There are still some things you can do to repair your kayak depending on where the damage is. Also, it should be noted that many people have claimed to be able to weld crosslinked kayaks by filling in the crack and surrounding areas with linear HDPE. Technically speaking, this isn’t welding. However, rather than throw a kayak out it might be worth a try.
Every kayak, crack, and plastic is different. There are no warranties implied in this procedure that the type of plastic your kayak is made of can be plastic welded, that the crack won’t leak once welded, that the crack won’t get worse and that the structural integrity of the kayak won’t be compromised.