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How to Repair a Kayak with a Nitrogen Plastic Welder
An extreme impact with a sharp rock or other obstacle might make a crack in your kayak. The bottom of this kayak has a crack that goes all the way through to the other side. This video will show you how to repair this type of crack using a nitrogen plastic welder, the integrated airless plastic welder, blue LDPE (low density polyethylene) welding rod, and stainless steel reinforcing mesh.
You can also use HDPE (high density polyethylene) welding rod to make this repair, but we chose LDPE welding rod because it is easier to work with.
Watch us repair a kayak with an airless plastic welder (like the KCW Pro or 5700HT Mini-Weld Model 7) at this link: https://www.polyvance.com/video/kayak-repair/how-to-repair-a-kayak-with-an-airless-plastic-welder.
Always wear proper safety gear while working!
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LDPE or HDPE?
The difference between LDPE (low density polyethylene) and HDPE (high density polyethylene) is the length of the molecule chains. HDPE has longer molecular chains than LDPE and the melting temperature of HDPE is often higher than that of LDPE.
LDPE's lower melting temperature usually makes using it as filler rod easier-to-use than welding HDPE filler rod to HDPE plastics.
HDPE is also "tougher" and more abrasion resistant than LDPE, but the practical difference is minimal when doing repair work. If you need the best wear characteristics and can live with making slower, more difficult welds, use HDPE rod. In most cases, we see better quality welds when using LDPE rod for typical crack or hole repair on boat hulls and ATV plastics.
Note: This is a list of the Polyvance products that can be used to make this repair. This list does not include sanders, grinders, or other common tools you will need. If you have any questions, please don't hesitate to call technical support at 800-633-3047.
An extreme impact with a sharp rock or other obstacle might make a crack in your kayak. For example, the bottom of this kayak has a crack that goes all the way through to the other side. This video will show you how to repair this type of crack using a nitrogen plastic welder.
First, place some aluminum tape on the inside of the kayak to cover the crack if you can reach it. This will prevent the welding rod from flowing through the crack. Next, grind a v-groove into the crack using a die grinder. Rough up the plastic on both sides of the v-groove. Blow or wipe off any loose plastic pieces.
Most kayaks are made out of polyethylene, either high density or low density. Either type of rod will work when repairing polyethylene. Choose which type of rod you would like to work with, and pick the color that most closely matches the color of the kayak.
Before welding, make sure the nitrogen flow on your welder is set between 11 and 13 liters per minute. Use your nitrogen welder to heat the kayak and the welding rod at the same time. Press the rod into the v-groove and apply gentle downward pressure on the rod to melt it into the kayak. Keep the flow of nitrogen aimed just in front of where the rod meets the kayak. This ensures the two plastics fuse together. Make an even stroke with the airless plastic welder to smooth the weld.
Cut a piece of stainless steel reinforcing mesh to fit the damaged area. Align the mesh over the top of the weld. Use the nitrogen welder to heat the weld and the mesh. Use a screwdriver or other tool to embed the mesh deep into the plastic. There may be some spots where the mesh didn't get embedded well. You can use the airless plastic welder to heat these spots and then press the mesh in.
Lay another pass of welding rod on top of the reinforcing mesh. Make another even stroke with the airless plastic welder to smooth the weld. Go back with the airless plastic welder and smooth the rod into the plastic. If any pieces of mesh pop up, heat the area and push the mesh deeper into the kayak, then cover the area with the melted rod. Allow the weld to cool before moving on to the next step.
Remove the aluminum tape from the inside of the kayak. Grind a v-groove along the crack line, just as you did before. Weld one pass of polyethylene welding rod along the v-groove. Smooth the welding rod into the kayak plastic. The kayak repair is finished. Now you can get back into the water without fear of sinking!
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