pvc glued seams vs welded seams

[lancelot9898]

It appears that welded seams on a PVC dinghy are preferred to glued seams but not really sure since over on the Canadian website for the Saturn Dinghy they appear to make an argument for the glued seam. Could not follow their explanation and wonder if any one here thinks that glued seams are preferred. Since I plan on rolling up the dinghy and keeping it in it's carrying case on deck, the heat alone will cause problems if the seams are glued even if it's protected from UV.

[a64pilot]

I didn’t PVC dinghies were glued?
Least I didn’t think so.
It’s my understanding that a welded joint is better, just Hypalon cannot be welded, so they have to glue it, be better I think if it could be welded?

[hellosailor]

The problem with glued seams, in any material, is that the material may not have been cleaned, prepped, and primed properly. Or the glue may not age well. In both cases the result is that the glue begins to fail, and fail often enough so that the French government used to condemn Zodiacs and other craft as they reached ten years of age. Including life rafts.

A properly "welded" seam is heated with intense high-frequency radio waves and the two pieces of material literally are fused together, melted into one unbroken piece. There's nothing to come apart, nothing to fail except a gross failure of the material itself. (Like badly cured PVC, or PVC that has been exposed to too much UV light.)

So while a welded seam can still fail--it is much less likely to fail than a welded seam. Glued seams often become a very expensive game of "whack a mole" as you try to keep patching just one more small leak after another.

Saturn? Very cost effective, apparently. How well they will age out is anyone's guess.

[lancelot9898]

The Saturn folks say the seams are hand glued while one of their resellers(boatstogo) say: "Seams are hand glued, also called cold welding or chemical welding. Glue dissolves upper layer of PVC, welding it together. Same way as heat welding, but without cracking."

Now is that sales talk??

[hellosailor]

Any above-ground pool store can sell you a vinyl patch kit. Those pools use a vinyl liner, and eventually then get punctures. Your dry the vinyl off, apply a solvent glue, apply a patch. It does, yes, literally melt the two pieces of PVC or vinyl together and "fuse" them. That's probably what the Saturn folks are saying. If it is only fusing one layer of PVC...I'm not sure that's the same as real fusion but it would certainly beat the old "glue" seams.

Bottom line, what's the warranty and do you think they will be around to stand behind it?

[danielamartindm]

Traditionally, the welded seams of PVC didn't leak, and you were far more likely to have to keep adding air to a glued Hypalon inflatable than a welded PVC one. Now, with so many RIBS and tenders being made in China, I'm hearing more stories about glued attachments (oarlocks, D rings, tube to hull, etc.) on both PVC AND Hypalon coming undone- some in very short order. Maybe cheap glue or bad surface preparation?

[KD8NPB]

Originally Posted by lancelot9898

The Saturn folks say the seams are hand glued while one of their resellers(boatstogo) say: "Seams are hand glued, also called cold welding or chemical welding. Glue dissolves upper layer of PVC, welding it together. Same way as heat welding, but without cracking."

Now is that sales talk??

It's not only sales talk, but it's also complete BS that isn't supported by science.

///

Eventually, the PVC material breaks down, releasing plasticizers. The plasticizers eat away at the adhesive, acting like a solvent. Oxidization also takes it toll, slowly pulling apart the long chains that formed when the isocyanate reacted with the polyurethane in the adhesive. As the chains shorten, the bond strength reduces, until a slight tug debonds an entire surface with minimal effort.

CSM/CR ("Hypalon") is a thermoset elastomer, so it's very stable and tends to degrade very slowly. The main killer of CSM/CR adhesive is oxidization, hydrolysis, bad application (too much/too little adhesive), bad mix (chemistry/moisture problems during assembly), and overstressing (customer abuse).

Welded PVC is unaffected by oxidization, hydrolysis or plasticizer migration. It is also significantly stronger than a glued bond. The only variables are the feed rate of the PVC and the amount of heat applied to the weld. As long as the machine is set up right, it makes the same weld every time.

[KD8NPB]

Originally Posted by danielamartindm

Traditionally, the welded seams of PVC didn't leak, and you were far more likely to have to keep adding air to a glued Hypalon inflatable than a welded PVC one. Now, with so many RIBS and tenders being made in China, I'm hearing more stories about glued attachments (oarlocks, D rings, tube to hull, etc.) on both PVC AND Hypalon coming undone- some in very short order. Maybe cheap glue or bad surface preparation?

PVC and TPR thermoform plastic fittings are being used more often on CSM/CR surfaces now. When the plastic starts to degrade, it debonds.

EPDM fittings last longer since it is a thermoset elastomer, but the cost per fitting is about 300% more, so it raises the cost of the boat. It is also non-recyclable.

Everyone seems to want cheap dinghies, so this is is how the manufacturers respond to reduce the price of their dinghy.

[kclancy]

I have been an avid whitewater rafter long before I became interested in sailing. I have owned many different rafts, both hypalon and PVC. Both work great but usually someone has a preference for one type over the other. It's a Ford versus Chevy type thing. Personally, I like them both. However, I would never consider buying a PVC boat with glued seams. The glued seams are going to fail and there is no way to do a good repair. I would also never, and I mean never, purchase a Saturn raft. They are cheap junk.

[Dougtiff]

AAARRRRGGGG !, back in the 80'S i purchased a new 12 foot Zodiac, the previous one [hypolong]had been a good boat, lasted many year's, i used the new boat for a short time, cleaned ,powered, and packed it up for storage, 5 year's later i unpacked it, and to my utter dismay, i found all the GLUED seams had failed, after doing some research, i found out Zodiac had changed from all Hypolong to a combination of PVC and Hypolong, this 3,000 boat was unusable and Zodiac would not stand by there product, would never purchase any of there product's ever again, no matter how good it was.

[lancelot9898]

A truly welded pvc is desirable over the glued seams so what are some of the names? I wonder if different names are actually produced on the same assembly lines in China.

[john61ct]

Sorry for OT, but I want to DIY make this stuff, not just repair.

Is the "welding" equipment just too pricey?

Any pointers to web sites or forums that discuss this topic?

[kclancy]

Originally Posted by lancelot9898

A truly welded pvc is desirable over the glued seams so what are some of the names? I wonder if different names are actually produced on the same assembly lines in China.

In the whitewater arena, the best PVC boats are made by AIRE, Sotar, and Maravia. I'm not sure if any of these manufacturers make dinghy style boats.

[CarinaPDX]

@Dougtiff: Yes, back in the late 80's Zodiak changed their process and a lot of boats developed problems. The biggest problem was that the molded rubber piece that connected the transom with the tubes came off the tubes - it was essentially unrepairable. There were a lot of nearly new Zodiaks falling apart. I remember that initially Zodiak tried to honor the warranty, but as the costs skyrocketed they went into stonewall mode. A class action lawsuit was eventually settled, for $12m IIRC. The problems were not limited to just dinghies: I knew one cruiser who had a 5 year old liferaft fail to inflate for repacking - a total writeoff.

I wasn't one of those burned, and this year I bought an aluminum PVC RIB from Zodiak - I am hoping that a quarter of a century is enough time for them to have put this behind them.

Greg

[Mike Banks]

I do not know about the dinghy brand mentioned originally-but I had an incident in croc-infested waters where a dinghy that was new but unused for a couple of years, was required to rig cyclone ropes. All went well until the seams decided to come adrift. Welded seems would certainly be better than glued.

That left me in the water with rope all over the place. I was close to the mangroves so able to get out--but fortunately a young Sophia Loren turned up on a jet ski and rescued me. It was all I could do to stop throwing myself back in.

Anyway--on examination of the dinghy, the seams were all glued and the glue had simply been no use it had deteriorated into a kind of tacky viscous goo.

OF COURSE I had inflated it and let it sit for a while before launching it--it must have been the movement while fastening the 20 mm nylon around suitable timbers and trees, that started the seam separation. Once it started--it just came apart so quickly I could not haul myself back to the vessel in time before it was just a mess of ropes and PVC.

Now I use a Polycraft dinghy. It is not quite as stable as a Zodiac, but it is far more stable that a tinny or a fibreglass or plywood dingy. My Zodiac was not much use--it fell apart at the seams too--and I had it re-glued several times.

The only disadvantage the Polycraft has, is the same as for all hard floor dinghys. It is not able to be rolled up and stashed--it has to be hoisted and lashed on to deck mounts.

Mine is filled with polyurethane foam--it is an option. That makes it recognised by SOLAS as a life raft. HUGE advantage.

https://www.polycraft.com.au/model-r...00-tuff-tender

I like to fish from my tender, it can go close to reefs, into shallow waters etc--it has built-in rod holders at the stern, and I have a Bimini fitted to provide shade while I am rowing or fishing. It rows like a dream--most inflatables row like pigs.