Friday, April 02, 2010

Fix a Ding in Your Canoe

How to Get a Dent Out of a Super-linear Polyethylene Canoe

Sounds kinda heroic don't it? 

Canoes with  lightweight hull designs made of a flexible super-linear polyethylene material sometimes get dents in them.  Fortunately, the material they are made of remembers its shape.  You can use this to help you repair minor dents and dings and even some major crinkles.  Mad River Canoes (tm) uses SLP construction to integrate the hull and deck structure of their Mad River Adventure canoes to provide rigidity, durability, excellent abrasion and impact resistance. Integrated polyethylene hulls balance a modest price against a very tough and virtually maintenance free design. But dents do happen. Here's how to save your boat from early retirement if you hit a rock or leave something heavy sitting on the hull in the sun! The instructions here are for dents, not holes, cuts or cracks that breach the hull. That's a different article.

Things You'll Need
  • Heavy leather gloves
  • Hair dryer or heat paint stripper
  • Patience and sunshine

First try putting the canoe in the sun and applying gentle pressure to the inside of the hull once the sun heats it up. The SLP hull of the Adventure series canoe has some "memory" and if gently heated may let you pop the dent out and restore your canoe to its original shape.

Set the canoe up on a flat spot in the sand or soft lawn. For more stubborn dents, this technique works best on a very hot summer day. Fill the canoe with water. Water is very heavy and provides the "gentle pressure" you need to push the dent out. As the sun heats the water, it also heats the hull. When heated the hull may "remember" it's original shape and pop back into shape. You may also have to press the warm hull with your hand to get the dent to pop out. Be careful putting your hand in. Sunlight heated water can get surprisingly hot. Keep an eye on the temperature to avoid distorting the shape of your canoe.

If pushing by hand doesn't work, install a brace inside the hull that presses outward against the dent. You can cut a piece of wood to size or slightly longer and wedge or duct tape it in place against the dent. You might want to place a wide square wooden foot on the undamaged side under your brace so it doesn't create a new dent where the brace presses against the side opposite the dent. Leave the brace in place for a week or so and let the sun heat up the water every day. Don't cut the brace so long it pushes the hull out of shape. Watch out for distortion of the hull. Make sure every part of the hull touches the ground firmly.

If the dent resists repair by the above described methods, you can dry out the hull and string a heavy-duty extension cord out to the canoe and plug in an ordinary hair dryer to heat the hull at the site of the dent. You have to keep the dryer moving and don't touch the heating element to the canoe. Heat the dent on the side where the dent is and gently press from the opposite side with your hand. You might want a heavy leather glove for this part since the hull will be quite hot.

If the hair dryer doesn't work well, you can use a hot air gun of the sort that's used to remove paint and wallpaper from walls. This requires even more care than with the hair dryer. If you heat too aggressively, you might melt the hull and cause a hole to form. Keep the gun moving quickly at all times in a circular motion at least 1 inch from the hull. Watch closely for glistening and melting of the hull surface.

Preventing Dents

On the Rack
Do not suspend your canoe by it's ends. If it gets hot, it could sag and warp the canoe in the middle. Support racks should support the canoe at either end about a third of the length from bow and stern.

In the River
When in moving water, try not to hit rocks. Scout your path and avoid large rocks or shallow bottoms. You may have to get out and walk your canoe around such spots in the river. Be careful not to drop your boat while launching or unloading. Get lots of help when loading or launching.

In the Drink

If the canoe turns over in fast water and fills with water, do not get in front of it. Guide it quickly to shallow water, turn it over to drain the water and pull it out.. Full of water a canoe is as heavy as the car I used to drive in college and if it hits a rock with that mass and momentum, there WILL be a dent!

In the Sun
Do not leave the canoe tightly tied down, especially in the sun. This could pull a dent into the hull from the pressure of the tie down straps. Especially, be careful of heavy duty crank down straps as they can exert serious force on the hull and cause a warm hull to buckle.

* Don't overheat the hull. You can melt a hole in the hull if you're not careful.
* Repair the dent as soon as possible to prevent it from becoming permanent.
* Don't overload the canoe either in the water or on the rack.
* Don't forget your life jacket and an extra paddle.

(c) 2010 by Tom King

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