I broke my boat

I found a two inch crack, in the boat, at one of the side braces of the seat. It is at the bolt attaching the seat to the side. Is there a new glue that will fix it? I’m thinking about using wide stainless washers inside and out. I’d welcome any advice. It’s a Pungo 120 and it is around 6 years old. Thanks all.

G flex
http://www.westsystem.com/ss/repair-kits/#plastic Might be worth a try. Most adhesives don 't work well on plastic boats, but Some folks have reported success with G flex.

There’s a procedure called plastic
welding that may help, but you have to find a welder who is competent. Ask at your poly kayak dealer.

G-flex might work, but it works better when the surfaces to be glued are open, so that they can be briefly torched to oxidize the surfaces.

Doubt you can fix a crack with glue,…

– Last Updated: Jan-20-14 9:49 PM EST –

...unless the strength of the adhesion is as great as the strength of the original plastic. Unfortunately, poly is famous for things NOT sticking well. Gluing together that tiny surface area within the crack itself sounds like wishful thinking to me, as the smallest bit of deformation across the crack will produce enormous stress within the glue connection. Maybe it can be plastic-welded, but if you don't have that option, I'd be tempted to form-fit a thin sheet metal patch (stainless steel), preferably on both sides, clamped over the plastic with several tiny bolts. Yeah, it will look like hell, but it will stop the spread of the crack AND it will distribute the stress applied by the seat over an amount of surface area that is hugely greater than what was originally the case, so it should never fail again. By the way, once this is done, you just bolt your seat connection at the same location, right through the patch.

If you CAN plastic-weld the crack and even if that makes it as good as new, I'd still want to do something to better-distribute the load that caused the crack in the first place (similar procedure as above), but that's assuming the crack came about because the load on the seat is greater than what's typical. Otherwise I'd expect it to fail again. If the load on the seat is not so great, meaning the original failure was a freak occurrence, I'd have some faith in a good plastic weld (it still wouldn't hurt to add another bolted connection or two).

Shaping sheet metal to match compound curvature would take some finesse (relief cuts with overlap), but if the curvature at the cracked location is simple or only slightly compound, it's a very simple job. Chances are, a patch that's just a two or three inches wide is more than enough, reducing the degree to which you need to match whatever complex curvature there might be.

Harbor freight sells plastic welder
About $40 I think. There are youtube videos on how to do it. I haven’t done it myself but a reoccurring theme I’ve heard is practice on something else first!

I would have to see it, but…
I would think that G-flex wetted out fiberglass would work well and then use the large stainless washers like you thought.

Call West Systems up, and they will walk you through the process

jack L

thanks all
Thanks for the repair advice and suggestions. I think I’ll use some glue AND add a stainless ‘washer’ to both the inside and outside. It won’t look all that great, but should prevent further cracking…I HOPE! Be safe all, and enjoy short day

If G-flex adheres reasonably well, …
… I’d agree with Jack’s recommendation. Relying on adhesion of a patch of material (in this case, fiberglass cloth) would be far better than gluing the crack or even placing glue under a washer due to the large surface area involved (so there’s minimal stress on the adhesive). And just as when doing any other kind of hull repair this way, the patching should be done both inside and outside.

crack repair

– Last Updated: Jan-21-14 12:19 PM EST –

In order to effectively repair the crack you are going to have to unbolt the seat on the other side and move it enough so that you can get to the crack from both the interior and exterior of the hull.

The crack will need to be first "guttered out" a bit on both sides. You can use a scraper with a V-shaped tip, or even an old "church key" beer can opener for this if you have one. An alternative is a Dremel type rotary tool with an appropriate sized grinding tip. The idea is to create a smooth, V-shaped opening half way through the thickness of the hull from both sides. This will allow you room to get polyethylene melted into the full depth of the crack, if you use thermal welding, or get epoxy into the full depth of the crack, as well as create more bonding surface for the epoxy if you use G Flex.

I would probably give thermal welding a try if you feel up to it. There are a bunch of youtube videos demonstrating this process using anything from purpose made thermal welders, to putty knives heated up with a propane torch, to heat guns, to soldering irons.

Basically you need some polyethylene rod or material, a heat source, and some tool to smooth the molten poly into the crack and fuse it with the hull. Here is a youtube video demonstrating the process that shows not only the use of a rotary tool, but also the Harbor Freight welding tool mentioned above:

You can find quite a few other plastic welding videos with a simple search.

As was suggested in the video, I would check with Wilderness Systems to see if they could provide you with welding rod (don't worry about the color). Remember to "terminate" the crack on both ends with an electric drill and bit as shown in the video.

The reason I would probably try thermal welding first is that it has the theoretical potential to return the cracked area to nearly new strength. Although G Flex does work well on linear polyethylene if used exactly per directions, I don't think the bond will ever be as strong as the original unbroken poly.

If you don't feel up to thermal welding, I would repair the crack using G Flex thickened with silica powder. Referring to the link that angstrom provided, what I would recommend is the 650-K repair kit. Don't worry that West Systems calls this an "aluminum boat repair kit". The resin and hardener in this kit is the same stuff as in the 655-K kit, but the 655-K epoxy and hardener are somewhat thickened. The unthickened G Flex is better for wetting out fiberglass cloth, which you are going to need to do.

In addition to this kit, you will need some denatured or isopropyl or rubbing alcohol and an inexpensive hand-held propane torch. You will also need to buy, beg, borrow or steal a small amount of fiberglass cloth. Someone on this forum can probably send you a small amount in an envelope. I would recommend 6 oz/square yard weight.

To repair the crack with G Flex, clean it well on both sides with alcohol. In order to get the G Flex to bond to polyethylene you must first pretreat it by passing the tip of a propane torch flame over the repair area exactly per the instructions that come with the G Flex. I have found it is best to to this in dim light so you can clearly see the inner blue cone of the torch flame. This is what needs to contact the plastic. You don't want to melt the plastic, just pass the torch over it to oxidize the polyethylene (temporarily). If you can't or don't do this, the epoxy will not bond.

Now prop the boat up on its side and put some clear plastic packing tape to seal the crack on the other side so the epoxy does not drip through. Mix up a small batch of G Flex epoxy and thicken it a bit with the colloidal silica powder included in the kit. The dental syringes in the kit are useful for getting the epoxy down in the depth of the crack. Pull the plunger out of the syringe and pour the epoxy into the barrel, then put the tip of the plunger back in the barrel, invert the syringe and expel the air. You may need to use a couple of epoxy applications on each side to completely fill the crack. I would overfill it a bit, then sand the surface of the repair down smooth and flush with the adjacent hull so that your fiberglass cloth lays down smoothly over it.

Even in the (unlikely) event that you can plastic weld the hull and restore it to its original strength, unless you back up your repair with cloth it is likely to fail again, since it failed in the first place. As suggested by Jack, I would apply a fiberglass patch on both sides of the crack.

Cut a piece of cloth big enough to overlap the sides and ends of the crack by at least an inch, or as close to it as feasible. More than an inch doesn't hurt. You should mark the area your cloth is going to cover and lightly sand that area of plastic with 80 grit sandpaper, then wash it well with alcohol. You will again need to flame treat it with the propane torch. You can moisten the area the cloth is going to cover with some unthickened G Flex epoxy, then lay your cloth piece down, and wet it out with more unthickened epoxy. To completely fill the weave of the cloth will require one or two more applications of epoxy. Whenever applying another layer of epoxy over a prior epoxy application that is fully cured, you must first wash the cured epoxy to remove any "amine blush". Wet sand the repair after the epoxy is fully cured and cover the cloth with some spray paint that approximates the color of your hull. The paint will protect the epoxy from UV exposure. G Flex does not cure clear like some other epoxies. It will cure to a honey color, so the repair will be visible, even if you did thermal welding with color-matched poly rod.

Repeat the fiberglass cloth repair on the other side of the repaired crack. You might even want to use a second layer of fiberglass on the interior of the repair, slightly smaller in size than the first. After sanding and painting you will need to redrill a hole through the cloth repair to remount your seat.

I have a polyethylene C-1 that had the cockpit coaming completely cracked off over about 1/3 of its circumference. I repaired the crack using thickened G Flex epoxy, then backed the repair up with fiberglass cloth as described. I did not use thermal welding as this was a boat constructed of cross-lined polyethylene and thermal welding does not work well on cross-linked poly. Most makers use a high-density linear polyethylene these days. My cockpit repair has held up well so far.

Plastic repair
New member here but I’ve been repairing boats for a couple decades. As others have said, welding, and or using G-Flex(sometimes used along with fiberglass) are good methods for repairing polyethylene.

I just got off the phone with Confluence Watersports (1-800-595-2925. There were three different materials used on the Pungo 120 Kayaks…

1: Linear, poly

2: Duralite (harder to repair than linear)

3: Ultralite (which has the look of fiberglass/kevlar)

They need the serial number to verify which one it is.

For a crack like you describe, and if its Linear Polyethylene, a repair with G-flex and some fiberglass seam tape would most likely be your best bet(can’t say for sure as I haven’t seen the crack) to strengthen the area around the seat mounting holes. Maybe use two or three layers of different width seam tape. Once cured, drill new holes thru the fiberglass.

I repaired a gentleman’s WW Kayak recently where the nylon webbing tie down had ripped the cockpit rim off the front of the boat while pulling into a parking garage. I couldn’t get to the inside of the crack very easy so I used the G-flex/seam tape combo both inside and out. Its sturdier now than when new!

I also used the same technique to repair a Old Town Loon tandem kayak that had a huge tree limb fall on it and ripped the cockpit rim and deck

Sorry, I’m not familiar enough with Duralite or Ultralite materials(yet) to recommend a preferred method of repair.

Good luck!

Thanks again all!
Super helpful posts. I thank you ALL. I’m going to drill the ends of the crack, scrape it out a bit and weld it, then use Gflex. I keep glass cloth on hand…from too many years with wooden boats. LOL I shall then put stainless plates inside and out and through bolt my seat back in. Thanks again. Be safe all…Spring is on the way now!!