Fixing Dinghy Leaks

My "Island Inflatables" 2.6M was leaking water in, and air out. Had it a while. Quite good quality,not a bargain basement Chinese import, no Zodiac either, not hypalon,quite large diameter tubes, and takes a 6-10hp outboard(mine is 6hp Tohatsu). Maybe time for a new one, but I figured I`d try fixing it.

To find the water leak,I put it on supports, on paving, to see underneath, and poured water in. A seeping leak appeared at the corner formed by the transom. I marked it,and drained the water. The transom drain plug fitting I had suspected tested fine.
To find the air leak I inflated it hard and went over all the seams brushing on soapy water, like testing for propane leaks.

Eventually I got a good bubble at a seam of a side tube, but the seam was part covered with a reinforcing join strip.

Using reinforced pvc material and Sika waterproof contact cement I patched the water leak. The patch, and the area to be patched, were well sanded,wiped with acetone, and brought together after 2 coats of glue were touch dry, followed by much pressing and pushing towards the edges.Then left for 24 hours.
The leaking seam was more difficult,I couldn`t see the defect, but knew where it was. I had some Sika polyurethane glue on hand, it`s supposed to require one surface to be porous, pvc rubber is not, after talking to Sika I ran the glue into the area. It is thin, runs well, and has gap filling ability. I saw air bubble through the glue. More glue, and let it set for 24 hours, weighted to allow flow towards the defect. Then sanded the glue smooth and followed the patch procedure.

The dinghy has 3 air chambers, each side and bow. The bow was deflating, to a lesser extent, with the side tube, but I found no bow defect. When I inflated the repaired side chamber the bow one went hard, I figure the loss of support pressure of the deflating side chamber allowed the bow one to slump towards it.

That or a communicating internal leak, but I doubt that.
I`m yet to test the water leak, but fairly sure it`s fixed. So I sent the Admiral a confident message "It`s rock-hard." We`ll see what happens when I drop it in the water tomorrow.

Bugger I guess it didnt work

Conclusion: Sika is your friend

Good job Bruce, I admire your tenacity in solving a problem !

L.

The Saturday results for anyone breathlessly following the thread. A draw:Bruce 1, Dinghy 1. No air leak, but water leaked in. A suspicious area at the transom where the rubber mounts from the side tubes attach was confirmed by pouring water at the corners and seeing it emerge into the dinghy.
I`ll throw a tube of Sikaflex at it, pumped into the corners and along the seams, if that fails that`s probably the end. I`m guessing the motor torque affects these areas by force exerted on the transom.
It is interesting getting up close with the dinghy, if I wasn`t retired I `d have junked it as uneconomic, billed work hours would quickly have paid for the new one, but it`s become a challenge. And while chronologically 9yrs old, it spent much of its life reclining on straps under the garage ceiling.
I suspect a reason inflatables seams etc give trouble is they are imported crunched and rammed into boxes to minimize shipping space,straining joins and seams. A replacement will have endured that potentially damaging process.
On the plus side, we finally fitted the St Croix crane on the FB, and used it, without undue violence to the FB, to lift the dinghy from dock to FB,with a number of the dock neighbours present to applaud. Great piece of equipment,well designed and made, totally removable if wished, save for a small baseplate.
I hope this thread helps someone else trying to extend dinghy life. It`s been challenging fun playing about with it.

Greetings,
Mr. BK. Commendable effort. In the same vein, has anyone tried tire repair compounds such as: https://www.lowes.com/pd/Slime-16-oz-Tire-Repair-Sealant/4777245

Bruce, Iv'e got a dinghy that goes very flet in between visits to the boat. Takes about 2 weeks to go down though, so I just pump it up for looks, in case a prospective buyer looks at the boat. I sort of have it half-heartedly on the market. Do you do house calls..?

RTF, my 'research" found dinghy specific liquid sealants you pour in via the inflation valve,you inflate and roll and turn the dinghy around to distribute the goo. The sellers say it is very successful(they would, wouldn`t they).I might resort to it if the soapy water technique failed to identify the air leak. It might be good on generally porous tubes, but if the dinghy is that leaky, it`s the dumpster, though I believe people do re-tube hypalon dinghies,but it is not cheap.
Sorry Peter, no house calls, find a quiet hour, go over the seams with soapy water, air leaks are easier to find and fix than water ones.
I notice my dinghy has just one overinflation relief valve, for the bow chamber. That reinforces my view the side tubes influence the bow one, so overinflation of a side chamber could press on the bow chamber, causing it to, ahem, relieve itself, and thereby relieve the side chamber.

Bruce, a mate of mine had the same transom issue on his Zodiac. He valiantly tried every fix known to man, alas to no avail.

He is now the proud owner of a new hypalon RIB.

Regarding the St Croix crane, I installed one on Sarawana a couple of years ago, great piece of kit. Though there is some rust coming through in places, despite being SS.

Andy, I attacked the transom joins with sealant, incl pumping it into the suspect corners. "Sea Trial" next Saturday. If it fails, that`s probably it.
The St. Croix instructions say to apply wax, on your experience I will, though I plan removing the mast and arm(not the baseplate) except when using it regularly. Should be 316, maybe it`s not.

Dinghy was relaunched today, 2 on board, and inside remained dry as a dead dingo`s donger, as we say here. I hope the sealing withstands the load of an outboard on the transom, the sealant used is tenacious and highly flexible, here`s hoping for another year or so.
We made up a 4 point lifting harness for the dinghy to connect to the block of the new St Croix Junior 190 crane, splicing the snap shackle and central ring attachments. Finding the center of balance to lift without the dinghy tilting took time, adjusting rope lengths to get it right.
Hopefully that`s it for a while for dinghy maintenance. One thing I learned when applying patches, is to round the corners of the patch. Looks neater, but more importantly I think it removes potential patch adhesion failure at a 90 degree corner.

Well done Bruce! Hopefully the sealant will last and you will enjoy your honorable dinghy some more years!

L.

The cure. Utility Yacht Tender / Dinghy 10 - Bullfrog Boats

Yeah, I have a similar issue with my carib 11 light as Peter. No obvious leaks but all 3 tubes gradually lose air over the course of a couple of weeks. I think it is just general decline/seams as it is a 2007 model. It's still plenty usable and looks really good so I hate to replace it.

I've been thinking of trying the sealant. A buddy used it on his boat with good results. Anybody tried it? Do you need to put a bottle in each tube?

Dougcole said:

Yeah, I have a similar issue with my carib 11 light as Peter. No obvious leaks but all 3 tubes gradually lose air over the course of a couple of weeks. I think it is just general decline/seams as it is a 2007 model. It's still plenty usable and looks really good so I hate to replace it.

I've been thinking of trying the sealant. A buddy used it on his boat with good results. Anybody tried it? Do you need to put a bottle in each tube?

Click to expand...

We've used it twice with great results. The first time on an inflatable keel we were ready to throw in the dump. The last time, 10 years ago when we first bought Hobo. We sold the 13.5' rib that came with her and hadn't found a replacement. A friend let us use his 10.5 inflatable. After 3-4 days we had to re-inflate. We couldn't find any visible leaks so we tried a sealant from Polymarine. The bottle, I think was less than a liter. We poured it into the 3 chambers via the valves, inflated and rolled the dinghy around. We did an air exchange/inflation/roll and repeated 3 times. When we returned the dinghy 2 months later it was still fully inflated. I don't want to sound like an ad but the stuff worked for us.

The only issue we had was I was a little careless pouring it into a valve and had to disassemble the valve to clean it so it would seal.