Repairing HDPE

The questions I get asked!!! Help!!! A friend has one of those el cheepo (probably Wal Mart or K-Mart) fishing boat/float/platform boats like a Sun Dolphin or Pelican (although a Pelican is better made) that he got for nothing from someone who just wanted to get rid of it. It is made of plastic, maybe HDPE, and filled with foam. It has a lot of holes. He wants to patch the holes.

I can't identify the manufacturer either. No labels, logos or HIN. It's obvious where the HIN was but it's gone gone gone.

At first I just said get a fiberglass repair kit, but then I thought about it. He can't use polyester because it will dissolve the exposed foam, and epoxy resin may not stick to this stuff. Any suggestions besides using a match, a chainsaw, or running over it with truck?

 

About the only way you can repair these roto moulded or injection moulded hulls is to weld them. It is possible to solder in new material - I believe Topper actually sell a repair kit but a good polymer stockist may have a suitable rod size. You will need to ascertain if it is HDPE or PP first so you use the correct material for the job. It should be marked somewhere in the recycling triangle either PE or PP.

If holes are as large as a fist are in the hull, forget it. We have been advised that with a boat such as a Laser Bahia anything that size, and you get a new hull and transfer all the fittings etc. Beware of certain Optimist rotomolds as they have a deficient design flaw which makes them prone to failing - lack of continouos 'bridge' low down across the hull. They are the worst and the others seem OK and able to take repairs and last.

Because both PE and PP are long chain waxy polymers virtually nothing sticks to them which is why welding is the only real solution.

 

I found a rather clever video on Youtube in which the person doing the vid is welding holes in the HDPE using scrap HDPE from bottles and a propane torch. Looks like it would work for simple repairs. As he says in the vid, not professional, but practicaL. http://www.youtube.com/watch?v=hYuGKXAYy-E

Also found some references on-line to using 3M5200 to glue pieces on.

 

Gougeon's WEST system has a 2 part flexible adhesive this has been advertised to bond PE. Their ad showed a kayak or canoe cut apart with a chain saw and bonded back together. Go check them out.. Just remembered G-Flex is the brand name.
There are lots of videos about welding rotomolded boats.

 

Alcohol wipe, flame treatment, then G/flex.

 

A lot of that is too much work, I find that a good 80w or so soldering iron does a cleaner and better job. A good plastic for repairing jobs is the lil scoop that comes with the baby formulas, use the iron to melt and flow that into the repair area. The scoop will totally and melt and the hot plastic will melt the edges of the base area and mix with the plastic. You will need to draw the base plastic into the repair area with the iron tip and mix them together a bit. Give it a good dry sanding and hit it with a heat gun on wide and will send the whole area to gloss