C-Forum

I have a problem with my whitewater tandem and tripping boat. It is an Old Town Discovrey Scout, made of Olthylene, according to OT this is a crosslinked Polyethylene with a foam core.
What gives me grief on this boat is that the D-ring patches I have in there for my air-bags, as gear tie down and anchor points fotr the thigh straps regularly come off, which is no fun when running class 3 rapids in it.
I have tried several different glues, like glue from a canoe store that's used on Royalex, high strength spray-on contact cement from Loctite, different kinds of contact cements from the hardware store and unfortunately so far none of this glues lasted for more than one season of moderate use (3-4 weekend trips on class 2-3 water and maybe 5-6 days of spring paddling in class 3 water).
Does anyone know how I can get those darn D-rings to stay put, or do I simply have to bite the bullet and keep reglueing them every season.

Thanks!

martin

Hi Martin

First, contact SpaceCanoe - I think he mentioned at some point that he might have a glue which WOULD stick to poly(ethylene) (PE). If that doesn't work, then read on...

...and I'll try to help you out. FYI - I don't have a PE canoe myself, but I do work with PE films every day in my research. Basically, nothing sticks to PE particularly well - unless you first modify the surface of the PE to give the glue something to chemically bond to (this is how vynabond works on royalex canoes - it creates a chemical bond between the vinyl patch and the canoe hull). PE, unfortunately is chemically inert and difficult to chemically bond to. One way to modify the PE so it will form bonds is to oxidise the surface - in the lab I do this with a concentratd oxidising acid at high temperature, but somehow I don't think that'd work to well for a boat (how would you fit a boat in the beaker, to start with )

I know that in industry they sometimes surface oxidise PE using a flame treatment. I unfortunately don't know the exact method by which they do this. I know you can do it without destroying the film (this is sometimes used with packaging films), but not much more. You could try running a propane torch briefly across the surface of the hull. You want to do this just enough to modify the surface layer of the PE, but not affect the hull itself - ie. not enough to actually melt the hull. Probably best to practise on a piece of an old boat (any old kayak shoul do ) before trying it on your canoe. You could also try oxidising the surface and gluing an anchor to a piece of an old PE hull and then see if you can pull the two apart a few days later. You should also clean the surface of the PE with acetone, alcohol or something similar after oxidising and before gluing.

Hope this helps...and yes one of these days I will try this when I have some old PE plastic lying around...

Matt, thanks for your tips!
I have already tried most of them (oxydizing the surface with a torch, cleaning with acethone) but none of them seem to work.
I will fowwow your advise and contact space canoe hope he has some flue that works!

thanks

martin

I have heard of a 3m product called Jet Weld that is supposed to work, problem though is the appliator gun is supposed to be $1000. I ahve 6 Old Town to outtitt and looking for solutions myself. Let me know what you come up with

I have tried to find a good PE glue with no success. I have tried spray on, contact cement, and even a "special" PE glue from Colorado, very expensive, did not work for more than a few months. My conclusion is that glueing to PE is a losing battle. That said, here are a couple of alternatives.

I have been welding PE successfully using a plastic welder (same model that Adam has). I have only welded to repair cracks, tears and holes, never to install a connection point, but it might be possible to weld on a plastic piece that is more suitable for attaching straps (i.e. PVC is very good).

Alternatively, you could look at mechanical connections. Everyone who converts a kayak to C-1 has to face this issue, and so far as I can tell, we all use mechanical connections, whether it be tubes along the floor between the foam supports, bolt on pieces to the the hull, or attachments to the seat, you will never see a polyethylene C-1 outfitted using glue to hold down the thigh straps. You could probably do something similar for your attachment points, by connecting to the seats or the thwarts.

Daniel, which kind of PE did you weld? I heard (correct me if I am wrong here) that crosslinked PE is, unlike linear PE, not weldable, and the hull of my Old Town is, unfortunately, crosslinked PE. If welding crosslinked PE works, then that would definitely be an option.
My upper attachment points are all attached to the Seats or thwarts, the ones that I have problems with are the anchors on the bottom of the hull, particularly the crotch anchors for my thigh straps. I already thought about bolting them on, but I am not too keen on dril;ling all kinds of holes into the bottom of my canoe, if I can somehow avoid it.
Thanks!

martin

Hey!! Back from the non-internetted NorCal location and am over my shock that the Governor of California is an entry level position.
Anyway, here’s the section of the repost that might be of value to you. Let us know how it works out, and feel free to contact me and ask away;
Ric Taylor

I've got just the thing for you, 3M pretty much makes everything; in point of fact, they now have a glue specifically for linear polyethylene. It's called DP 8005 and it will glue almost anything (including concrete) to linear polyethylene. You gotta love the paddling industry; for years these idiots have been telling us that nothing works when gluing linear polyethylene, and it took me all of 7-8 minutes to find this stuff. Contact the 3M distributor near you and I'll bet they will be able to provide you with a sample. Be forewarned: it's not cheap; it only has about a 5-7 minutes working time, and it has to be applied with an applicator gun (it CANNOT be hand mixed) but it will glue anything to linear polyethylene, and I would be willing to bet that it will work for cross-linked polyethylene as well. Also, when I was talking to them about a year ago, they were talking about having a DP 8010 which had a longer working time, probably 10-12 minutes. Anyway, It worked BOMBER for installing all of my thigh straps, etc., on my Medieval, so I bet that it would work in your situation as well. Be sure to ask the 3M technician, of course.

Truly good news if that 3M product works. I tried an expensive, specialized glue from Colorado that was "guaranteed" to work on polyethylene, needless to say my thigh braces came off in the middle of a drop.... Now I am not too keen on glueing.

I have welded cross linked polyethylene, and I think one of my weld jobs was on superlinear polyethylene. I don't think it matters much, I believe that the common belief that you can't weld (you fill it in, linear or cross linked) polyethylene is incorrect. The welding process basically melts the plastic, and when it cools the added plastic (the weldment) crystallizes along with the old plastic, and presto, you have a boat just like new.

You cannot do this with plastics that refuse to melt (polycarbonate comes to mind), you need to bond to the surface for them (i.e. glue). However, so far as I know, both forms of polyethylene melt just fine, so can be welded. It is possible that melting and cooling superlinear polyethylene may cause it to recrystallize as cross linked polyethylene, since I believe the superlinear form requires a catalyst (metallocene) to form, and the cross linked form may be the chemically preferred form. Do we have a chemist to answer this?

At any rate, I have a welded DOM-41 in my garage, definitely cross linked, with a weld job that cannot be distinguished from the remainder of the boat without extremely close inspection, and the crack was three inches long and about 1/2 inch wide at the front, so I rest my case for cross linked......

Dan
I'm looking into welding a Pyranha Micro 250 made out of High Density Polyethylene - a form of cross link - I beleive (ok I've posted on this before).
I'm looking for tips and tricks relating to this. Any thoughts / suggestions?
These folks ( http://www.urethanesupply.com/ ) replied that you can weld this stuff so I'm thinking hard about getting a welder too!
They may also be able to talk to the PE issue - glueing verses alternatives!
Thanks
Paul C.

Aside from being a reasonably good song from Radiohead...

Polyethylene as a plastic is manufactured in a variety of densities, and two fundamentally different chemical forms. The density is typically described as low density, medium density, and high density. I think that virtually every boat is made from high density polyethylene, since it is stronger and stiffer than low density material. Obviously, you could save a little weight using the same thickness of low density polyethylene, but I don't think the boats would hold up.

So, when you order an "ultralight" version of a boat, such as the Riot DOM ultralight series (I think they are discontinued), my understanding is you get a thinner boat, still made out of high density polyethylene.

Within the world of high density polyethylene, there are two distincly different forms, one known as cross linked, the other known as superlinear. In reality, there are a large number of "in between" forms. Polyethylene is a polymer, meaning it is made of thousands (or possibly millions) of linked identical units (called monomers). Sheets are made by melting beads of plastic supplied by a manufacturer such as 3M, then cooling the melted plastic and rolling it into sheets. I think that many of the boat manufacturers have rotomolding equipment, that allows them to form half a boat at a time, then essentially melt the two halves together, but I am really not too sure about the details.

That said, whether you get cross linked plastic (where the monomers join together in a 3D lattice) or superlinear plastic, where the monomers link up into straight chains that are millions of units long, depends on the catalysts you add to the cooling plastic, and the exact details of the process.

The boat manufacturers spend a lot of time arguing the merits of cross linked versus superlinear, and I don't really know which is "better". Supposedly, the superlinear can be recycled, whereas the cross linked cannot, but I don't really know if this is true, and if there is even a market for recycled linear polyethylene. There is a lot of talk about the supposed inability to weld one type of plastic versus another.

In my experience, cross linked plastic (found in all boats more than about 2 years old) welds just fine. I don't know how to tell superlinear from cross linked by looking at it or testing it, so I don't know if I have welded superlinear plastic. All the boats I have welded have been older, beat up boats, probably all cross linked PE. My guess is that superlinear will weld just fine also, but perhaps someone has experience and can share it.

Rotomolding is actually a bit different from what I've observed , and is really kind of neat. Big, hollow metal mold with injection ports. They inject the plastic in, and rotate the mold (for even distribution) as they cool it (I *think* the mold is heated up more first, but I really don't know). The cooling rate actually effects the boat size ! But when you pull it off the mold it's a big, hollow object. The cockpit is then cut out, finished off, the foam and seat / pedastal put in, as well as grab loops, then the Coast Guard (or serial) number is stamped in (hot metal object or scribing tool, depending on year of boat / company).

That said, "composite" (aka glass, kevlar, carbon) boats are still more fun

Martin;
I should addend my post to say that I have not seriously stressed these straps that I glued in. They are holding up fine, but haven't been seriously used/abused as of yet.
Sorry for any confusion;
Ric

Space Canoe, I guess I'll be able to tell you how strong the DP8005 adhesive (still have to find it up here in Canada) is nect year, as soon as the spring paddling season starts, since I have a tendency of misscommunication with my paddling partner, usually during spring paddling in classIII rapids when paddling tandem , which usually leads to spending some quality upside down , which will put plenty of stress onto the D-Ring anchor points .

martin

Hi Martin

I was doing some research on the 3M website about these products...they do now have the DP8010 glue out with a longer working time....they list working time for the DP8005 as 2.5mins and for the 8010 as 10-12 minutes. The full product name is 3M Scotch-Weld, Structural Plastic Adhesive DP-8010.

Hi Matt,

Thanks for the info. I have some problem getting these adhesives here in Canada, but through work I can fairly easily get my hands on Loctite adhesives.
You would not happen to know by any chance if Loctite has an equivalent adhesive in their product line.

Thanks,

martin