Plastic welding?

Well it's a welding query, just not my usual metal variety.
Bought a couple of kayaks today, with a couple of minor dings so have been onto Youtube to do my apprenticeship on plastic welding, and it seems the best way to do it is with a plastic welder - who'd a thunk it? Seems Leister is the professional one for $1000+, or these on Ebay for $20

• https://www.ebay.com.au/itm/500W-220...AAAOSwXxhZ9ozr

Anyone had a go at plastic welding with a hot air welder? I have a normal heatgun and was immediately suspicious of Youtubers using something that would heat such a large area and turn my kayak to goop, so one of these finely directed hot air guns look the deal. It's only $20, but my usage would be very low so would not consider any professional heatguns.

All advice greatly appreciated.

I've done a fair bit of plastic welding , mostly it was 30 years ago using a $600, pro level welding gun.
Have also tried it using various ordinary hot air guns and unless they have fine nozzle and fine grained temperature control they are a PITA to use.
The more of a newby you are the more you will need the temperature control and a fine nozzle gun

I have recently been using a GMC hot air gun that has good fine grained temperature control and a reasonably fine nozzle.
I would not even bother with that ebay unit.

You will also need some welding rods - they have to be of EXACTLY the same material as the stuff you are welding otherwise it won't work.
Do yu even know what your canoe is made of?
You will need to do LOTS of practice beforehand so you will need some sheets of different thickness of the material and practice welding these before you go near something like a canoe.
Start off with some thicker material eg 4/5 mm and then graduate down to the same thickness as the canoe material. It is very difficult to completely make thin material water tight without a lot of practice.

Plastic welding is not like metal welding, unless you have a lot of experience it leaves the material more brittle and likely to crack fro any future strains than the original material. As well as sealing up the cracks in objects it pays to add strengthening plates of plastic over the top of the crack if you can. If it is a curved surface you will need to heat and curve the strengthening plates as well as straight plates may add too much tension to the joins.

Now that you know all this you might find it quicker and easier to see if you can find a repairer to do the job for you :D

I had to plastic weld a plastic fuel tank on our mower (Cox) I could not get it fuel tight, no spurts jest seeps. So I smothered the weld with Stag goo, it holds fuel now and I saved $100.

Look up kayak repairs on the internet.

None of the Australian proponents of kayak repair mention hot air guns or plastic welding.

From what I can see it is all 2 pack epoxies and pulling dents by applications of boiling water and suction pads.

Grahame

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Originally Posted by Grahame Collins

None of the Australian proponents of kayak repair mention hot air guns or plastic welding.
Grahame

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Funnily enough, one of the first YouTube clips I saw was from East Coast Kayaking here in Oz and that is exactly what they do:- https://www.youtube.com/watch?v=GWtgkLyqkZ0

Their use of the narrowly focused heat gun is what prompted my query.

Hi jabell,
Agreed. My error! It was one I missed.
The point is the ones I did find, did not use the heat gun and I query why?

In the YouTube example you gave, the repairers used the Leister plastic welding gun, basically the Rolls Royce quality of heat guns.

I used and demonstrated a Leister plastic welding heat gun for high school students for years in completing PVC projects.

While they are very good units there is still a certain amount of technique required and a lot of it is the filler rod angle, set gun temperature, travel speed, gun distance, standoff and pressure applied to the filler rod. Just knowing when and where to use the different techniques takes time. There is a great deal of difference between plastic welding something heavy and thick like a keel verses welding a thin hull section as thin unsupported or braced areas will warp .

Good luck to you, should you choose to use the $20 heat gun.

Grahame

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Originally Posted by Grahame Collins

There is a great deal of difference between plastic welding something heavy and thick like a keel verses welding a thin hull section as thin unsupported or braced areas will warp .
Good luck to you, should you choose to use the $20 heat gun.
Grahame

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Well for $20 I'm going to take a punt. I accept all the points you make, and I'll practice on scraps for while to see if I think I can do it successfully. Its got to be better than my big heat gun or soldering iron, and I have 40+ years of passably competent shed work to fall back on so I'm hopeful. :)

I really appreciate you taking the time to add your comments and experience!

I would probably try a Leister knock off before spending $20 on that thing. Also comes with all the required nozzles to feed the plastic electrode though. https://www.ebay.com.au/itm/1500w-Ho...EAAOSw4DJYlvKs

Going back 20-30 years from when I used to paddle kayaks, the Leicester welder was the go to tool. Are they dings or holes / tears?
For holes / tears V grooving the joint was essential and finding the right filter was always a pain. Shaving a strip of plastic from around the edge of the cockpit was easiest if it was a small repair.
Also most kayaks are cross linked polyethylene and back then the filler was non cross linked. The joints were never 100% like a proper fusion weld in steel.
HTH

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Originally Posted by Com_VC

I would probably try a Leister knock off before spending $20 on that thing. Also comes with all the required nozzles to feed the plastic electrode though. https://www.ebay.com.au/itm/1500w-Ho...EAAOSw4DJYlvKs

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Ended up getting something in-between:

https://www.ebay.com.au/itm/1080W-Pl...72.m2749.l2649

Better than the small one I initially listed, and hopefully for the small amount of maintenance I'll be doing it will suffice. An interesting variation on the Leister model with the pump and heatgun separated. I'll post back on its usefulness in a week or two.

I used on of THESE stuck onto an Aldi gas powered butane soldering iron/micro flame heat gun to join a couple of bits of drainage channel together; the material was about 3mm thick. It worked surprisingly better than I expected it to.

Essentially you have a BIG soldering iron tip with a hole through it. My method was to produce a double bevel on the two pieces and run the "iron" slowly across the first side of the joint area; slowly feeding the filler rod through the hole until the molten "pool" is visibly being produced. Then the join was repeated on the other side but as half of the weld had been done the heart could be increased.

Plastic welding is less predictable than metal welding I'm finding - I clearly need to practice!I've ordered a fusion tip for it, and some ready made HDPE rods. I'll get some decent pics of it and put them up in the next few days.

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Originally Posted by jabell

Plastic welding is less predictable than metal welding I'm finding - I clearly need to practice!

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I did say that.

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You will need to do LOTS of practice beforehand so you will need some sheets of different thickness of the material and practice welding these before you go near something like a canoe.Start off with some thicker material eg 4/5 mm and then graduate down to the same thickness as the canoe material. It is very difficult to completely make thin material water tight without a lot of practice.

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I've ordered a fusion tip for it, and some ready made HDPE rods. I'll get some decent pics of it and put them up in the next few days.

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If you purchase HDPE sheets you can cut strips off to use as rods and practice on the welding the same sheets . Then you know the rods are exactly the same as material you are welding.