Trouble shooting a slow leak

[J.A. Veil]

My Native Manta Ray 14 is only a few years old. I store it inside my walk-out basement, so it rarely gets sunlight exposure that could weaken the hull. Therefore I was surprised when I noticed a gallon of water inside the hull after a trip a few weeks ago. The Manta has its drainhole on one side rather than on the end -- this does not drain the hull effectively or completely. I had to remove the front hatch cover and first bail out water with a cup, then use a chamois to soak up the rest.

I did not think much about it until after the next trip, when it happened again. I thought that maybe I had rubbed a hole in the keel (like I did with my Ocean Kayak Drifter the previous summer), but the keel was intact. I thought that perhaps some water had entered through some of the screws used to attach accessories, so I tightened all of them (none were particularly loose anyway).

When I went out today in very calm water, there was no way that waves or spray could come on top of the hull and work into the bilge area. Yet at the end of 2.5 hours, I found nearly a gallon of water inside the hull again.

When I got home, I put one end of the kayak on my front porch and the other end on a small table on the lawn in order to elevate the boat and keep it approximately level. I then started filling the inner hull with water. After it was about 1/3 full (5 minutes of garden hose time), I leaned down and looked at the underside of the hull. I was relieved to find one location that had a steady drip of water through the hull. Now the detective work was done.

It turns out that there are 4 sets of scupper holes coming out on the bottom of the hull. Three sets come through from the top of the boat, but one of the sets is a blind tube that never reaches the top surface. I suspect it was molded into the hull for structural reasons. It was around the port side blind scupper hole that I saw water dripping from a 2" long hairline crack along the edge of the hole.

The bottom of my boat has many scratches -- cosmetically unpleasant, but of little consequence. There is no way that I would have discovered which of these was the leaking culprit without filling the hull with water and watching for the drippage.

I dried off the hull and let it sit in the hot sun in preparation for a patch job using Goop. The late afternoon thunderstorm we had in Annapolis put a hold on the job until tomorrow.

I would like to patch the crack from the inside, but the location is too far from any of the hatches into the bilge area. Instead, I plan to work on the outside and fill the entire scupper hole on that side with Goop, then feather out a layer to cover the crack with some extra overlap. I may go ahead and fill the other side too while I am at it. I have had good luck with Goop and hope it will take care of the problem (Side note: I have bought Marine Goop at West Marine before -- I think I paid more than $10 for a tube. I found regular Goop at Home Depot in the glue aisle for $5).

[DOGFISH]

You know that is interesting. We have had a couple of kayaks at the store that have had similar cracks near where the scupper hole is located, at the bottom of the kayak. That must be a stress point or cracks from the more flexible bottom connected to the more supported area of the scupper hole. I wonder if it comes from sitting in the kayak, while on solid ground or just from the flexing of normal use. While sitting on top, on solid ground, that would put alot of pressure on the area of the scupper hole. One may not normally notice, but the bottom of a kayak also flexes alot during use, from wave and water pressure. Anyone ever load the inside of your kayak and then try to get something out of a hatch after you are out on the water. I can tell you the floor rises and makes a tight fit for some items. Again, that would put more flex on that same area. I mean, it is only plactic. I suppose damage could also happen from shipping or tightening the straps down too tight during travel. That is interesting and should be something that most SOT owners should keep in mind. Thanks.

Good luck with the repairs.

[kevinfry]

I just tracked down3 small leaks on a tandem I was given. I used the forced air and soapy water method. I did not want all the weight of the water. Now I have to weld them..I have "tear repair" on them now and it worked great on my test float, but it is a temporary fix.
what "Goop" did you use? The stuff I know that is marketed as "Goop" or "Amazing goop" is not supposed to work on polyethylene?

[J.A. Veil]

The stuff I know that is marketed as "Goop" or "Amazing goop" is not supposed to work on polyethylene?

I have used several types of the Goop product before. I don't think there is much difference between them based on the ingredients listed and the range of applications. They certainly look and smell the same when you squeeze them from the tube.

I too have read the caution about using Goop on polyethylene. I tentatively used it to mount a transducer in my Drifter many years ago. It worked great, and I had no problems. When I bought the Manta Ray 3 years ago, I used Goop inside the hull to fasten the transducer. Once again -- no problems. Last summer, I found a 1 cm wide hole in the rear of the keel of my Drifter caused by repeated short drags across a driveway. I patched it first with a thick layer of Goop, then laid a piece of metal over the area and added several more layers of Goop to seal it in place. Even after placing a full tube of Goop directly onto the polyethylene, I had no troubles.

[J.A. Veil]

You know that is interesting. We have had a couple of kayaks at the store that have had similar cracks near where the scupper hole is located, at the bottom of the kayak. That must be a stress point or cracks from the more flexible bottom connected to the more supported area of the scupper hole. I wonder if it comes from sitting in the kayak, while on solid ground or just from the flexing of normal use. While sitting on top, on solid ground, that would put alot of pressure on the area of the scupper hole. One may not normally notice, but the bottom of a kayak also flexes alot during use, from wave and water pressure. Anyone ever load the inside of your kayak and then try to get something out of a hatch after you are out on the water. I can tell you the floor rises and makes a tight fit for some items. Again, that would put more flex on that same area. I mean, it is only plactic. I suppose damage could also happen from shipping or tightening the straps down too tight during travel. That is interesting and should be something that most SOT owners should keep in mind. Thanks.

Good luck with the repairs.

I rarely if ever sit on the boat while on dry land. Nor do I use roof racks for most of my trips (I shove the kayak in the back of my minivan). However, what does happen nearly every time I launch and retrieve is that the stern is floating in the water while the bow is on the beach. That does create a situation in which the entire hull may try to flex slightly from end to end. I am a large heavy guy, which adds more strain the midpoint of the hull (more or less where the crack occurred). I guess I need to be more careful about getting the boat fully in the water before boarding.

[kevinfry]

That is good news on the goop. My holes are small enough that I may try to patch them that way until winter then do some welding....that is if it cold be removed easily....ever do that? I have been using some goop products like a liquid gasket when attaching pad eyes and such, I was just afraid to depend on it to fix a leak.

[J.A. Veil]

Follow up and lessons learned

Here is what I did to repair the leakage and a report on how it performed.

I started on Monday morning after the dew dried. Before adding Goop, I looked closely into the scupper hole that was adjacent to the culprit crack. To my surprise, the supposedly solid upper end of the blind tube was riddled with small holes. This may have been due to gas bubbles in the polyethylene during the molding process. I was unable to tell if the holes penetrated all the way through into the hull cavity.

I filled the entire scupper hole (1" across and at least 4" deep) with Goop, then smeared some around outside the scupper opening to cover the hairline crack. This seemed like a good idea, but ended up being a mistake and cost me several days in slow drying time. The Goop dries in less than an hour when applied in thin layers. However, when applied as a thick mass, it remained rubbery and did not dry after a full afternoon in the 85 deg sun.

At that point I realized that I would need to move some of the Goop out of the hole. I took a large nail, poked down into the center of the scupper tube and lifted some of the contents out of the hole. I smeared it around on the hull bottom. I ended up doing this nearly 10 times on Mon - Wed. Finally by Wed afternoon, I had removed enough content from the scupper hole so that what was left inside had dried hard. However, by doing that, I changed what was a reasonably clean job cosmetically into a mess.

This morning, when I venture out of Sandy Point, I took the Manta Ray and gave it a trial by fire. I paddled out to the West Shore rock pile and back in 1.5 to 2.5 ft waves. The boat was definitely bounced around today. To my great pleasure, after bringing the kayak out of the water several hours later, the inside of the hull was dry!

In retrospect, by smearing multiple layers around the outside of the hole and building up at least 1/4" of thickness around the culprit crack, I probably made a more structurally sound repair than I would have if the bulk of the Goop made a solid plug inside the scupper.

[kevinfry]

OK you convinced me....i am going to fix my pinhole leaks with goop too. Seems to be sticking well enough