Kayak problem: Repairing punctured polyethylene

A. Hi Keith. I'd probably "bolt on" some kind of patch piece and gasket. I've seen it welded and it was a terrible mess. Sorry, but I haven't seen high density polyethylene successfully welded or glued.

A. Keith,

Assuming and HOPING that you canoe is not made from an ultra high molecular Polyethylene (supposedly unweldable in the higher grade ranges), your best option is to take your canoe down to a thermoplastic fabricator (not a fiberglass fabricator!)and get them to weld on a patch. Mind you, the patch colour may be very different from your canoe colour ... either virgin white or Ford black!

There is no glue, no cement for hdPe.

Hope this helps.

A. The Coleman canoe owner's guide states three ways to repair the RAM-X. Write the company for instructions. I've had good results.

A. My 81 Coleman 17' canoe uses tubular interior frame for keel support. A few years ago a small stone was lodged between the frame and the bottom of the canoe which pierced through the plastic keel when I scuffed a submerged rock through some rapids. I can tell you, with 500 lbs of gear, it didn't take long to notice the leak and start bailing.

After several unsuccessful attempts, I finally was able to repair the hole by using a Weller Soldering iron to heat the surface and drip melt sacrificial PEX-A tubing on the opening. After allowing to cool, I sanded lightly and applied sikaflex or dap roof and gutter sealant to the area. After allowing to dry for an hour, I reinforced with plain old nashua duct tape and applied another smooth coat of sealant over top. To this day, it has not leaked and the sealant has resisted damage from underneath.

A. Hi Ernesto,

If you can't 'bend' the polyethylene weld rod easily, one (not very good) suggestion is to use a low density weld rod which is very flexible, unlike h.d. rod.

The other consideration is to say to yourself HOW ELSE can I fix those seats? Can you, for instance, weld on a heavy 1/2" strip along the front and back or at the two sides ... by strip I mean a 1/2" thick bar of whatever height you want. Use black Pe in preference to white.

Another idea is to remove the seats and then a) drill 4 holes in the seats (say 1/2" dia) b) weld on to the hull 4 rods of 1/2" dia ... which should extend up into the seats and can be easily welded and then ground down. But why not use something heavier like 1" dia?

Re 'bonding cements' ... ah, that's a pipe dream, I think, and sure would NOT take the vibration and flexing of the seats...

A. If you need to re-repair this section try the following.

#1. get yourself a piece of 3/4" aluminium rod x 1" long cut squarely at the ends and a short section of 1/2" all thread rod and 2 x nuts to suite.
#2. drill a hole 1/2" through at the mid way point of the aluminum across its access and insert the all thread through the drilled hole and secure it either side with the nuts. you should have a "T" shaped tool.
#3. cut the pegs off completely at the cracks, ensure that the cuts are square and clean, clean up any swarf.
#4. The tricky bit and wear gloves!hold on to the all thread "handle" heat the aluminum to 200 °C (sorry we are all metric here), once heated place one end of the aluminum to the hull and the peg to the other and apply light pressure, you will see the material bead up on and around the tool face, at this point ease up on the pressure and allow the poly to absorb some heat (count to ten).
#5. Remove the peg from the heated tool then the tool from the hull, quickly and carefully, don't worry too much if the material 'strings', put the tool aside, place the heated end of the peg to the heated section of the hull and apply light pressure so the material squashes out a little.
#6. hold until cool, 1/2 minute should suffice. Notes: Too much pressure and or heat will give you unwanted results, extra holes which I'd gladly fly over to repair.

This IS the strongest method of repair weld rod will fail in time. Don't be afraid to remove material to access the repair area as so long as it is easy to replace and don't loose the bits you take out, I speak from experience. I submit this information freely and take no responsibility to the interpretation of the method afore mentioned, but I have been doing this work for 18 years and this is the only method I employ in these repair type and instance.

Good luck,

A. Hi Jo,

You'd have to double check with a manufacturer of rotational (Engel process) ... but methinks you are up a gum tree.

There's no, no WAY of bonding ANYTHING to Polyethylene except for Pe to itself ! What in the heck for? And were you to do this, then the 'weight' of the metal should be LESS than the flotation (full of water!) of the Kayak otherwise you'd have an Irish Titanic Coracle!

As you know (I hope), the S.G. of Pe is around (depending on type -- h.d., m.d., l.d) 0.900 and any metal is damnably higher. I suggest that you go to a rotational moulder and watch how they make 'things' ... there's a metal mould ... you pour in so much Pe powder ... you rotate as you heat the mould so that you get even distribution ...you let the mould cool down ... but the processes max. max. thickness is l/2" and in your case, probably 1/4" is OK. If you want to do something 'different', you could ask the moulder to use two colours of PE. The first colour would be the outside colour and the 2nd one the inside colour ... also, unlike pure white PE., colours help in UV attack somewhat.

Cheers!

A. I beg to differ with Freeman Newton about the feasibility of metal coating polyethylene; - metal can be deposited onto it if it is activated correctly. The only way I know is to use a plasma discharge and then use an electroless metal deposition process with a suitable activator such as Pd/Sn. HOWEVER, the adhesion is not brilliant and it is definitely not suitable for thermal cycling because of the differences in the coefficients of expansion. Freeman is correct about the problems of density and floatation, but if you were to coat the bottom of the kayak, perhaps it would make it more stable by lowering the centre of gravity?!? Nevertheless, this doesn't answer the question as to WHY you want to do it - just to make it look different?

Hi again Jo,

Sure seems that I was wrong about coating Polyethylene ... but as Trevor C pointed out, PE has an awfully bad coefficient of thermal expansion, so a PRACTICAL solution of metallizing is not on.

Moreover to lower the centre of gravity you'd need a keel. And if you were to make a Kayak with a keel (to which lead etc weights could be bolted to) then you'd probably be the first in the world to do so.... which should make life very interesting if you are traversing any rocky rapids !

And Trevor wondered, too, WHY you were even contemplating 'metallizing' the kayak. To be different? I guess so ... but at your age and with an inquiring mind, why not ask these questions.

Re that suggestion of two colours, ah, maybe you have something there because any kayaks I've seen were just a mono colour. So if, for example, the moulder had to use 50 lbs of Pe powder for the Kayak, if he dropped in 5 lbs of a coloured Pe ... and then later dropped into the mould the balance of 45 lbs, you'd at least achieve a fairly economical boat ... but, at a guess, if you metallized it, you'd better get a big student loan!

A. Although the metal MAY be more resistant to damage from rocks, it would seriously reduce the performance of the kayak because of water flow and weight. Another point - High Density Polyethylene is not rotational moulded, it is blow-moulded. If you were going to rotomould a kayak you would use Low Density Polyethylene.

You really should take a trip to a kayak manufacturer and ask them to show you how it is done.

You are doing a Skool project right, do you really NEED to go to the complicated process of coating polyethylene with metal? From what I've experienced, you should get your qualifications the easiest way possible and go for 'revolutionary' processes later once you are established in a job/career.

A. Take a look at Verometal.com. This is a new metal coating process that can be applied as thin as a coat of paint and onto any non greasy surface, and as a Derry man you can have it applied in Ireland.
The copper coating is used as an anti foulant on boats already but any of the metals, Aluminium, Stainless Steel, Brass, Bronze, Zinc, Iron or Gunsmoke can be used.
I have used it. It looks great. It is a cold spray process involving metal powder in a resin.

Thanks, for relating the details of your success, Michael!

Yes a number of companies (Liqmet, Luminore, Metal Facades, Metalier and probably others) offer cold spray metalizing, but I doubt it will stick to HDPE which, in my limited experience, always has a very waxy feel to it. But for me the bigger question is why Jo wants a metal skin :-)
-- if it's for increased abrasion resistance I doubt that cold spray metalizing will offer any.

Regards,