Folding Kayaks Forum

leaking sponson
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Author:  overland [ Wed Oct 11, 2017 10:13 pm ]
Post subject:  Re: leaking sponson

I just repaired four leaky valves on my Pakcanoe. The leaks were where one poster here has said: where the valves fit over the rubber tubes that lead to the sponsons. The valves themselves didn't leak, but air was seeping out where the tubing is inserted into the valves. I talked to Mike at Pakboats, who suggested I put some glue where the tubing fits into the valve and let it flow down in there. I used two coats, and it seems to have worked.

Author:  KerryOnKayaks [ Sun Nov 12, 2017 10:40 pm ]
Post subject:  Re: leaking sponson

Update on the leaky sponson project:

After buying materials to make all new sponsons for the pair of Pakboat Swifts I bought last summer, I decided to make one last attempt to salvage the original, but defective, ones, before I cut them up to re-use the Boston valves on them. The recurrent problem, even after re-coating the insides with marine sealant, seemed to be that the heat-seal welded seam between the dual tube assembly kept failing due to pressure from the tubes when I pumped them up fully. As the seam ruptured between the segments. it would peel off the vinyl coating on the inside and the fabric there would slowly leak through the weave again.

So I took the deflated assembly and ran a line of stitching down the middle, directly over the welded the seam. I knew this would cause leakage due to the needle perforating the material, but I then inflated the tubes and poured 2 ounces of the marine raft sealant into each, closed the valves and tumbled and rolled them to distribute the liquid sealant evenly throughout the inside of the bladders. As expected, some of the sealant oozed out along that center stitching line. But I let the sponsons cure for two days, periodically deflating and re-inflating them so that the solvent vehicle for the sealant could evaporate.

I'm pleased to see that they seem to now be holding air pretty well for extended periods but I still hesitate to inflate them to full pressure. Before I do so I plan to paint both sides of the stitch-line with with Aquaseal to seal it up firmly. I am hoping that once this is done the sponson will be able to withstand full inflation.

I'll update as the project proceeds.

Author:  KerryOnKayaks [ Wed Nov 22, 2017 12:06 am ]
Post subject:  Re: leaking sponson

I think I'm going to throw in the towel on the defective sponsons and make new ones. Stitching the central divider seam, coating the stitching with H-66 and adding a second round of internal sealant still didn't make them hold pressure. The heat-sealable nylon from DIYPackrafts in Canada is on the way.

I did use the marine raft sealant on one of the inflatable seats (same fabric as the sponsons and with the same problem of air leaks at the site of welded seams.) It seems to have worked pretty well and maintained full inflation for several days, even after I sat on it for a while. I could see where a bit of the sealant seeped through along a couple of the "quilting" seams that create the pockets in the seat.

So I still think that liquid latex sealant is a good product for pin holes and slow leaks in normal inflatables.

Author:  Alv [ Wed Nov 22, 2017 12:23 pm ]
Post subject:  Re: leaking sponson

Even if you could make the stitched seam hold pressure, you would still have the problem that air would leak from one cell to the other. I don't see how that could be prevented. If you then puncture one cell, air would leak from both, and you would lose the security of having a backup cell.

Author:  Alv [ Thu May 17, 2018 2:14 pm ]
Post subject:  Re: leaking sponson

We finally have the repair patches for mini boston valves. In case you have a different kind of valve on your boat, we are shipping the patches as sets of 4 with the valve complete. $20 per set plus shipping. You can use the adhesive from the repair kit - or we have the adhesive available too.

To install, you have to cut out your old valve and glue on the patch where the old valve was. Then you glue the patch on over the hole. A new mini boston valve has been welded to the patch. A PVC valve to make it last long and using a new interface glue that we have not seen any issues with.

Author:  EisMan [ Tue Jun 19, 2018 11:33 am ]
Post subject:  Re: leaking sponson

KerryOnKayaks wrote:
I think I'm going to throw in the towel on the defective sponsons and make new ones.

I too am up a creek without sponsons, how did your project turn out to make new ones?

Author:  KerryOnKayaks [ Sat Jun 30, 2018 12:26 am ]
Post subject:  Re: leaking sponson

Eisman: i have all the materials and tools but the sponson project landed on the back burner in May due to other commitments including buying a 128 year old house up the street as a rental unit and having to do some work on it to make it fully functional for my tenant. Ironically I bought the place in part so that I had flat property on which to build a shop and storage for my kayaks but the work involved in prepping the place means I have not had a kayak in the water so far this year!

The sponson build will probably start week after next. I got heat-sealable vinyl coated nylon and Boston Valves from DIY packraft (the ones that Alv of Pakboat is now selling would have been a better deal but they weren't available yet -- in fact I was the one who suggested he have them made.) And I bought a Black Beauty hobby iron on Ebay to do the seam sealing, which will probably be tedious due to the length of the tubes. The site has excellent instructions and patterns for building inflatable boat components, by the way, as well as a range of materials. I also bought a quart of vinyl glue (H-66?) in case I find the heat sealing process lacking. I may try to make plain vinyl sponsons as well, like the traditional Feathercraft tubes, using the glue and experimenting with 8 and 12 ounce vinyl yard goods that I bought at a fabric store. I may try an overlapping side seam rather than the face to face welded seams that are apt to split under high pressure, like the sponson in my first FC (Kahuna) that ruptured over an inch along one edge seam when I neglected to relieve the pressure before loading it on the roofrack for the drive home on a hot day.

Author:  EisMan [ Mon Jul 02, 2018 12:11 am ]
Post subject:  Re: leaking sponson

Thank you! That is some good info, Since I posted last, I purchased materials from diy packrafts. After doing some welding testing I am certain you nor I will need glue, it welds so strongly that you almost cant pull it apart by hand. The only thing I haven't decided on is if I should fold the material in half with the TPU faces touching much like the oem sponsons, or if I should face all the TPU outward and seam it together with a 1 inch wide joiner strip. Using a joiner strip will likely result in a stronger sponson because the material is being pulled rather than split so to speak. The benefit to putting the two faces together is that there is extra material to poke the holes for tying it to the inside of the boat, but may be weaker, but I have no doubt that either way will be way stronger than the oem sponsons.

Im about to get this underway too and ill post my results here.

Author:  KerryOnKayaks [ Sat Jul 07, 2018 5:09 pm ]
Post subject:  Re: leaking sponson

Yes, I've been having the same dilemmas in deciding how to construct the sponsons. I have never entirely liked the way that the Pakboat parallel sponsons are made of two pieces bonded around the perimeter and then heat-sealed between the compartments. That is a LOT of stress on those welds from both sides. Those bonded divider seams are what failed massively on the failed sponsons of the 2 Pakboat Swifts that I acquired and am trying to restore. While I know that in those cases it was defective material (the vinyl coating failed to bond to the fabric substrate and peeled loose) it still seems like a design vulnerable to mishaps.

One design I have considered is making single tubes and then sewing a dual sleeve of nylon fabric with extended edges with grommets or buttonholes for securing the assembly into the frame and a stitched seam between the two compartments. This would be sort of a hybrid between the Feathercraft design of having removable vinyl tubes in nylon fabric sleeves and the Pakboat model of having the sponsons directly attached to the inside of the boat with cords. One advantage of the sleeves is that the sponsons themselves are protected from abrasion and damage -- and you could construct spare sponsons that could be easily installed in the field if you were on a remote trip.

I'm eager to hear what your experience is going to be with the DIY materials. I would really like to start on my own project but I have such a list of other commitments and responsibilities at the moment that the box of components is just sitting there making me feel guilty. And I have one of the Swifts set up in my basement and it is just such a nice looking boat that I really want to try it out!

Author:  geoffrose [ Sun Jul 08, 2018 11:20 am ]
Post subject:  Re: leaking sponson

About time I reported back in. I started this string with leaking problems in the valves of my Puffin. All 4 leaked, two so badly I could not use the boat.
I am happy to report that the 4 replacement valves I got from Pakboat did the job. Installation was straight forward. The patch that the valves were welded to was wide enough to make the glueing easy enough - room to wiggle. One of the values seemed to have the same problem as the old valves - leaking air at its base, but dribbling glue into the base seemed to catch the leak.

While I was at it, I bought and have attached a 4" removable skeg from Pakboat. Another success. I was never happy with the way the boat tracked, as I weaved a lot if using strong strokes. Now it tracks much more like my Quest 135. I was concerned about the skeg running aground in shallow areas or drag over beaver dams etc, but it does not appear to be a big issue. The skeg sits well behind my butt, which means its base is above the lowest point in the boat. It also has to be placed off the centre line to glue firmly, meaning it is only at about 70 degrees to the water. Finally, the skeg bends to the boat because the boat skin is flexible.

Author:  EisMan [ Mon Jul 09, 2018 2:01 am ]
Post subject:  Re: leaking sponson

Ive got one down 3 to go, yes 2 boats. So far you can pump these up like a car tire, well almost, this material is no joke wayyy nicer than oem. I sealed it with tpu facing together, that way I could fold the material in half and only do one weld seam. I made the seam about an inch wide so I could poke holes for the elastic bands that hold it in the boat.

I went with single chamber for ease of assembly but I couldn't see any problem with running a seam down the center to make it a dual chamber this material is incredibly hard to pull apart so separation of the center seam seems unlikely.


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