So I finally cracked my Prelude on a low water run. Actually it's worse than that. Both my wife and I cracked our Preludes on the same day, same run. Now I need to learn plastic welding ... or do I? It would seem like that is the best way to fix a crack in polyethylene. I've seen the videos of how to do it and it doesn't look like rocket science. But I've also seen the results. Most of my friends who have welded their boats go on to have them crack again at the weld at some point.
Is there a better way? I keep thinking of that g/flex video where they cut a rec kayak in half, glue it back together and then toss if off a bridge and its doesn't break apart.
Reason tells that I'll get a better bond with a polyethylene weld. Experience in the field, at least what I've seen or heard, doesn't suggest that really is a lasting fix.
Any thoughts? I've got time to mull it over. I just took down the spare Prelude from the rafters and ordered a new one as well. The repaired boats will end up as our backups.
Thinking outside the weld
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hankrankin
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Re: Thinking outside the weld
The video above is really good. I've done a lot of welding using that method and never had one fail.
Some comments:
- Use a scrape not a box cutter like he mentions. The scrape is just so much easier and in my opinion safer.
- Make sure you weld from the inside as well. The video only shows an exterior weld. The interior weld does more work than the exterior weld.
- Tack the crack closed from the outside, so you know it will look good. Then do most of the welding from the inside. I generally try and notch out 2/3 from the inside, then 1/3 from the outside.
- Don't be afraid to scape the notch deep. Welds fail when you don't weld all the way through.
- If your initial bead doesn't fill the whole notched out crack, don't keep twisting it in the same area to fill it. This can lead to bubbles forming. Just lay the bead however thick it is, wait for it to cool then scrape and weld again. It might take a couple passes to completely fill the crack but the end result will be solid.
Some comments:
- Use a scrape not a box cutter like he mentions. The scrape is just so much easier and in my opinion safer.
- Make sure you weld from the inside as well. The video only shows an exterior weld. The interior weld does more work than the exterior weld.
- Tack the crack closed from the outside, so you know it will look good. Then do most of the welding from the inside. I generally try and notch out 2/3 from the inside, then 1/3 from the outside.
- Don't be afraid to scape the notch deep. Welds fail when you don't weld all the way through.
- If your initial bead doesn't fill the whole notched out crack, don't keep twisting it in the same area to fill it. This can lead to bubbles forming. Just lay the bead however thick it is, wait for it to cool then scrape and weld again. It might take a couple passes to completely fill the crack but the end result will be solid.
https://vimeo.com/user32086287" onclick="window.open(this.href);return false;
Re: Thinking outside the weld
Also, if you have time to wait, shipping one of these from china is a good investment. It's way cheaper than any you will find here.
It will pay for itself in free beer for welding friends boats.
http://www.ebay.com/itm/1000W-Plastic-W ... ACA%3A3160" onclick="window.open(this.href);return false;
It will pay for itself in free beer for welding friends boats.
http://www.ebay.com/itm/1000W-Plastic-W ... ACA%3A3160" onclick="window.open(this.href);return false;
https://vimeo.com/user32086287" onclick="window.open(this.href);return false;
Re: Thinking outside the weld
Dave,
Thanks for the advice on the welding. Sounds like you've had good success with it. I do have plenty of time, so I plan to really do it right--remove the seat in one boat and the seat and a knee pad in the other to do both sides. One of the advantages over a kayak is better access to both sides of the crack.
Kaz,
I agree. Better yet, I will probably borrow the welder from my friends.
Thanks for the advice on the welding. Sounds like you've had good success with it. I do have plenty of time, so I plan to really do it right--remove the seat in one boat and the seat and a knee pad in the other to do both sides. One of the advantages over a kayak is better access to both sides of the crack.
Kaz,
I agree. Better yet, I will probably borrow the welder from my friends.
Re: Thinking outside the weld
I had a couple of K boats welded recently, the welder (who did an excellent job) did say that success depends on how much the surface of the polythene has oxidized, which depends on how much time it has spent in the sun. Your Preludes are probably older than both my boats, but it may depend more on how they are stored than age.
Of course to use g-flex you need to oxidize the surface, I wonder therefore if there is a case for welding newer hulls and moving to g-flex as they get older?
Presumably once flame oxidized to use G-flex, you can forget subsequently making a successful weld in that area.....
Of course to use g-flex you need to oxidize the surface, I wonder therefore if there is a case for welding newer hulls and moving to g-flex as they get older?
Presumably once flame oxidized to use G-flex, you can forget subsequently making a successful weld in that area.....
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NickParker
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Re: Thinking outside the weld
West Systems says that G-flex should be applied within 30 minutes of the flame oxidation for best adhesion, which implies the oxidation (at least the higher level achieved by flame treatment) is not permanent.JimW wrote:...Presumably once flame oxidized to use G-flex, you can forget subsequently making a successful weld in that area.....
This paper has some good info on photo oxidation within HDPE....the welder (who did an excellent job) did say that success depends on how much the surface of the polythene has oxidized, which depends on how much time it has spent in the sun...
http://www.bjp-bg.com/papers/bjp2003_3-4_158-169.pdf
Re: Thinking outside the weld
Hang on, oxidization doesn't reverse, it makes more stable compounds. Unless of course the flame oxidization makes an unstable oxide which then oxidizes further - consider carbon monoxide, floating freely in air it soon stabilises to carbon dioxide. Must be something like that I guess?NickParker wrote:West Systems says that G-flex should be applied within 30 minutes of the flame oxidation for best adhesion, which implies the oxidation (at least the higher level achieved by flame treatment) is not permanent.JimW wrote:...Presumably once flame oxidized to use G-flex, you can forget subsequently making a successful weld in that area.....
Re: Thinking outside the weld
Now that's getting technical. The boats are always stored in a garage and covered by a tarp, but have done their share of oxidizing on top of the car while driving to and from rivers.
I think the best course of action to try might be to weld first, then resort to g/flex if the weld fails within a short time.
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the great gonzo
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Re: Thinking outside the weld
No need to be thinking outside the weld for repairing PE boats!
Welding is the way to go on PE boats, at least as far as linear PE is concerned, which is used by just about everyone these days. Dave has some great advice for you, my technique is very similar, but I have a few variations, but both seem to give great results as far as weld durability is concerned. Here is what I learned about welding boats during the last few seasons while welding the boats, both canoes and kayaks, in the Esprit fleet in Canada, Mexico and Costa Rica. Nowadays my welds are really solid, I will gladly take any of the boats I welded down some class 4/5 water.
-You need good tools. Especially the welder. A good hot air welder has infinte temperature control and should have about a 1500W rating, IMHO. If you order on E-bay make sure that the voltage rating is 110, large parts of the world use 220 V. Get a nozzle for the air gun to concentrate the heat where yu need it, I use a 6 mm nozzle.
-Remove any outfitting that is even remotely in the way. The better the access to the damaged area, the better a job one can do. If the damage is under any kind of glued in outfitting, be sure to remove all the ADHESIVE! and to clean the area thoroughly, as dirt and/or glue inclusions in the weld will significantly compromise it's structural integrity.
-Lots of folks use scrapers to do make the V- Grove, I personally prefer a dremel with a carbide cutter, much faster on any long cracks.
-Since he highest tensile stress in a boat is virtually always on the inside, I grove about 3/4 on the inside and about 1/4 on the outside. Make sure that the groves touch, so that the weld goes all the way through. Drill the ends of the crack to keep it from propagating.
-As far as welding rods, I try to use material from the same manufacturer, but I have had a lot of success with random strips cut out of broken boats or cut out decks from canoes. The melting point and other properties of the PE that most manufacturers are using seem to be close enough for it to work, although I have been told that this is not always the case with some of the newer materials. I cut my welding rods to a width of about 3/16 ".
-When it comes to the welding, I preheat the rod to the point where it gets glossy before starting my welding. I focus the heat on the end of the rod, holding it close to the start of the crack, once it and the groove starts to melt I gently push the melting plastic from the rod into the crack, twisting it at the same time. This way the soft/melting plastic of the boat and the melting plastic of the rod mix thoroughly for a good bond. After couple of inches I use a plastic roller (drywall tape roller) to smooth out the still half- molten plastic and push it all the way into the crack.
-Don't set the temperature on the welder too high. If the plastic starts to bubble, the heat is to high, so turn it down a few notches. On the Leister heat gun I have been using I found that I had to turn the heat down to about a 4-5 out of a 10 on the dial.
-Once I got the inside welded I flip the boat over and weld the outside. If the inside was welded properly then this is more of a cosmetic weld for looks, as it is most likely already welded all the way through. Smooth out the weld or wait until solid and grind smooth.
The put in the outfitting again. The boat is good to go!
TGG!
PS: some folks use stainless steel or aluminum reinforcement mesh in their welds. I am very weary of this, as he steel and aluminum have mechanical properties that are much different from HDPE and cn thus create a stress raiser. If proper welding technique is used, they are not needed.
Welding is the way to go on PE boats, at least as far as linear PE is concerned, which is used by just about everyone these days. Dave has some great advice for you, my technique is very similar, but I have a few variations, but both seem to give great results as far as weld durability is concerned. Here is what I learned about welding boats during the last few seasons while welding the boats, both canoes and kayaks, in the Esprit fleet in Canada, Mexico and Costa Rica. Nowadays my welds are really solid, I will gladly take any of the boats I welded down some class 4/5 water.
-You need good tools. Especially the welder. A good hot air welder has infinte temperature control and should have about a 1500W rating, IMHO. If you order on E-bay make sure that the voltage rating is 110, large parts of the world use 220 V. Get a nozzle for the air gun to concentrate the heat where yu need it, I use a 6 mm nozzle.
-Remove any outfitting that is even remotely in the way. The better the access to the damaged area, the better a job one can do. If the damage is under any kind of glued in outfitting, be sure to remove all the ADHESIVE! and to clean the area thoroughly, as dirt and/or glue inclusions in the weld will significantly compromise it's structural integrity.
-Lots of folks use scrapers to do make the V- Grove, I personally prefer a dremel with a carbide cutter, much faster on any long cracks.
-Since he highest tensile stress in a boat is virtually always on the inside, I grove about 3/4 on the inside and about 1/4 on the outside. Make sure that the groves touch, so that the weld goes all the way through. Drill the ends of the crack to keep it from propagating.
-As far as welding rods, I try to use material from the same manufacturer, but I have had a lot of success with random strips cut out of broken boats or cut out decks from canoes. The melting point and other properties of the PE that most manufacturers are using seem to be close enough for it to work, although I have been told that this is not always the case with some of the newer materials. I cut my welding rods to a width of about 3/16 ".
-When it comes to the welding, I preheat the rod to the point where it gets glossy before starting my welding. I focus the heat on the end of the rod, holding it close to the start of the crack, once it and the groove starts to melt I gently push the melting plastic from the rod into the crack, twisting it at the same time. This way the soft/melting plastic of the boat and the melting plastic of the rod mix thoroughly for a good bond. After couple of inches I use a plastic roller (drywall tape roller) to smooth out the still half- molten plastic and push it all the way into the crack.
-Don't set the temperature on the welder too high. If the plastic starts to bubble, the heat is to high, so turn it down a few notches. On the Leister heat gun I have been using I found that I had to turn the heat down to about a 4-5 out of a 10 on the dial.
-Once I got the inside welded I flip the boat over and weld the outside. If the inside was welded properly then this is more of a cosmetic weld for looks, as it is most likely already welded all the way through. Smooth out the weld or wait until solid and grind smooth.
The put in the outfitting again. The boat is good to go!
TGG!
PS: some folks use stainless steel or aluminum reinforcement mesh in their welds. I am very weary of this, as he steel and aluminum have mechanical properties that are much different from HDPE and cn thus create a stress raiser. If proper welding technique is used, they are not needed.
Everyone must believe in something. I believe I'll go canoeing - Henry David Thoreau
Re: Thinking outside the weld
Gonzo,
Thanks for taking the time to write these very explicit instructions and advice! The only thing I didn't quite get is:
Thanks for taking the time to write these very explicit instructions and advice! The only thing I didn't quite get is:
I'm not quite sure what you mean. I'm imagining that I've scraped away a groove on both sides and that there may be the small gap by then that you could slip a sheet of paper or thin knife blade through. What exactly should be touching?Make sure that the grooves touch, so that the weld goes all the way through.
Re: Thinking outside the weld
Basically just make sure that the external and internal weld touch. Called a through weld. Here is my general process:milkman wrote: I'm not quite sure what you mean. I'm imagining that I've scraped away a groove on both sides and that there may be the small gap by then that you could slip a sheet of paper or thin knife blade through. What exactly should be touching?
- Close crack with clamps, straps, cinder block, whatever. Tack closed if you think it's necessary.
- Drill out the ends of crack from both sides.
- Start on the inside... Notch out almost through. 3/4 like Martin said. Weld it up. Let it cool fully.
- Notch from the outside until you hit the inner weld. Weld it up.
- Paddle!
Last edited by Dave.E on Fri Nov 07, 2014 1:22 am, edited 1 time in total.
https://vimeo.com/user32086287" onclick="window.open(this.href);return false;
Re: Thinking outside the weld
^thisthe great gonzo wrote: PS: some folks use stainless steel or aluminum reinforcement mesh in their welds. I am very weary of this, as he steel and aluminum have mechanical properties that are much different from HDPE and cn thus create a stress raiser. If proper welding technique is used, they are not needed.
https://vimeo.com/user32086287" onclick="window.open(this.href);return false;
Re: Thinking outside the weld
I've used both non-mesh and with mesh. Both work well. But with mesh you need to have much more material to work with so as to properly embedding it to mitigate the stress point. Had a creeker I meshed about 6 years ago and last I hear its still out there bang down drops.
Recently I had Fall Line Canoes weld my Prelude (was gonzo's) since the material was SSSSOoooooo thin (no mesh) this year. I just didn't have the time and have not done enough welds recently so I paid to have someone with more & recent experience do the weld. So far so good - I'm still boat'n it -just not bang on rocks as much.
Recently I had Fall Line Canoes weld my Prelude (was gonzo's) since the material was SSSSOoooooo thin (no mesh) this year. I just didn't have the time and have not done enough welds recently so I paid to have someone with more & recent experience do the weld. So far so good - I'm still boat'n it -just not bang on rocks as much.
Paul C.
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Official TOG Member (Team Old Guy)!
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Official TOG Member (Team Old Guy)!