Welding Strakes on Pontoons

[MaPaHa]

I had lifting strakes added to my pontoons and as I've mentioned here a few times, there are leaks that resulted from the welds that are behind the strakes. We have pressure tested the toons and sprayed them down with soap solution and there are no leaks that can be seen around any of the welds. My tubes have a drain at the rear and do not have sections in them so water leaking in anywhere can be drained. One tube will pick up a few gallons in a day but the other one will pick up 5-10 gallons in a half day.

I'm having a hard time finding the leaks because the boat floats nicely and the top of the strakes are out of the water so when I pressurize the toons on the water I can't see anything. I've even tried opening the plug and letting the center tube (that's not leaking) fill up with water to help lower the boat in the water but it's not enough. Even if I can get enough weight on the boat to submerse the strakes what I'll find is that they leak inside the strakes and nothing a welder can get to.

My question is to the welders out there. Would it be easier to remove the strakes and start over by fixing the toons first then putting the strakes back on? Or... having the strakes welded 100% and include the strakes as part of the floatation? I've seen factory strakes welded 100% and was wondering what type of welder it would take to do this.

I am an experienced welder for steel but not for aluminum therefore, this is a project I would have done. The shop that welded the strakes on does a lot of work on pontoons but had a bad day when working on my boat. However, they are willing to make it right.

I've also considered sealing the seams with the epoxy that body shops use to glue fenders on. I think it's dupont 5200 or something like that. A friend of mine owns a fairly large body shop and he swears by it. The strakes are structurally fine except they leak. Would this two part epoxy hold with a nice bead along the seams?

With either method of 100% welding or the epoxy, the strakes would be sealed and become part of the flotation.

Thanks for your input.

Mark

 

[Blujay96]

Re: Welding Strakes on Pontoons

I would say depends on the welder. If the welder is not experienced enough they could burn thru. The epoxy wouldn't burn thru and should seal good.

 

[MH Hawker]

Re: Welding Strakes on Pontoons

But the epoxy wont last long.

 

[BrianMc]

Re: Welding Strakes on Pontoons

MaPaHa, can your hear the leak when you pressure them up? They won't be much if your only taking on 10 gals.,but you aught to be able to hear them. Do your strakes have a flange? You could carefuly drill with a small bit a series of holes through the flange behind the weld,while leaving enough of the flange to weld back later. Drill away as much of the weld as you can,then use a small sharp chisel to clean away (connecting the dots) what's in between. This should expose the pinhole which is hidden under the edge of the strake. It'll be right behind the weld,where water enters from inside the strake.

A tig can be used to puddle away the ugly left from the old weld,seal the hole,and re-weld the strake.



I'd be afraid of cracks later welding them solid.

 

[MaPaHa]

Re: Welding Strakes on Pontoons

Sorry, I posted the wrong number on the epoxy I was talking about. It's 3M AutoMix 8115 and it's used extensively in the autobody repair industry for gluing on new fenders, roofs etc. They say it's not for structural bonding (that should be welded) but once the panel is welded in critical areas then it's used as a seam sealer for the rest of the panel. The cost is around $35 - $50 for a dual tube of 200 ml and takes a special applicator gun to mix it as it's applied. It would seem to me that an car or truck would get it's share of vibration and twisting. The strakes are welded every 12 to 16 inches so there's no structural issues.

MH Hawker,
I've read about epoxy on pontoons that didn't last and like you, I'm hesitant to try any but I wonder if it's this type of material (there are several brands) or some big box store epoxy that has failed. I also wonder if it was just laid over a crack that could still move around. Have you had any experience with this stuff or heard of it being used on pontoons?


Brian,
Yes I can hear most of the leaks by using a short garden hose up to my ear but it's the general area and hard to pinpoint a specific weld. My strakes are just like your picture shows and welded in the same manner. I may be able to modify my listening tool to get more specific. I've got excellent hearing but when I took it to the welded last year he couldn't hear anything but joked that he was hard of hearing plus there was some background noise. I did it in my shop at night with everything quiet.

I'm more likely to find the leaks than they are, so what about me taking a small cut-off tool / dremel with a grinding disk and cutting - grinding away the suspected weld only so the toon could still be pressurized and then they could see the leak. Then have them re-weld as you have mentioned?

It sounds like your gut feeling is that solid welding wouldn't be your first choice or even a choice at all. I know you've practically welded your entire boat so your opinion carries a lot of weight. I was wondering if it would only compound the problem.

There are three factory pontoon joints (every 5 feet) that each strake crosses and I can't be sure one or two of them isn't leaking. They have been repaired in the past but were not leaking when the strakes were put on. Any ideas on how to get to those other than cutting out a section of strake and butt welding it back on after a repair is made to the side of the toon?

Thanks,

Mark

 

[Scott Danforth]

Re: Welding Strakes on Pontoons

the issue is the strakes are covering up the leaking pin holes, so soap and water will not work to find the leak. the two choices you have are to fully weld the strakes, or remove them, plug the leaks and then re-weld them on.

 

[BrianMc]

Re: Welding Strakes on Pontoons

I doubt the pinholes are under the strake,unless the factory seam coincidently failed in the 6" that are covered. They will likely be right at the edge of the strake flange/under the weld. Since they were migged on I'm guessing the wire poked a hole through the puddle,then the weld bridged across. You've probably felt that scenario on steel with the wire speed set too fast. Water is entering from inside the strake seeping under the flange. Hope that makes sense.

You could eat away the weld as you described. Aluminum acts a lil different grinding though. It'll kind of smear as your grinding. It should still expose the hole,if you keep the tube pressured up as your grinding on it. Won't take much pressure,maybe 1/2-1 lb. I'm betting when you get it down really thin the hole will expose itself with soap and water. A small sharp chisel should break it loose once ground away. The reason I mentioned the small serrated bite out of the flange (approx. 1/8" wide) is to give them room to puddle the hole shut with a tig. They could then fill that little bite back in with a tig after the hole is plugged.

I wouldn't remove the whole strake,unless most of the welds leak. You should be able to fix the ones that are leaking,if you can find them. As far as the full welded strake goes I look at it this way. The way they are now the strakes are just tacked on. A full weld around the strake to seal the pinholes would essentially be creating a 40'-50' long seam to seal tight. Where as finding the pinhole your only sealing a small hole.

 

[MaPaHa]

Re: Welding Strakes on Pontoons

Brian,

That's the part that scares me a bit if they tried to weld them solid because both toons would be about 80 feet total of welding. I'm pretty sure I can find several holes by carefully grinding the weld away but not much of the strake. I'm pretty sure they can weld it and puddle it up a bit and hopefully it won't look like bird droppings.

When you weld a crack in aluminum should you drill small holes along the edge and at the ends for stress relief? Years ago I welded an old cast iron engine block for a tractor and I drilled holes at the ends of the crack and then used a nickel-arc rod. Was just wondering if it was the same principal or not necessary. It seems like I remember the guy that writes on this site that works at one of the pontoon manufactures that talked about using a drill but I don't remember exactly how he said to repair cracks. With the trouble I've had I want to make sure it's done right.

Thanks,

Mark

 

[BrianMc]

Re: Welding Strakes on Pontoons

Yeah 5150abf would be the one to answer that. I haven't welded any cracks on my tubes. I have welded cracks on thicker aluminum semi trailer frames and pneumatic tanks. On the thick stuff I actually grind a V and fill it in. I understand the principle with stopping the crack with holes though.

The work they do with a tig should look fine in the right hands.

 

[fergusmj]

Re: Welding Strakes on Pontoons

I have no technical knowledge in this area, but what about filling the toon with water and seeing there the water leaks out? A lot of water though? Again, I don't have any experience with this, but just curious if that is an option?

 

[MaPaHa]

Re: Welding Strakes on Pontoons

I tried that but got scared when they got about 1/4 full. Things went to making noise and crackling around even with them vented. I would have to get them at least 1/2 full and I calculate that to be over 2,000 lbs of water. Full water weight per pontoon figures out at about 4,300 lbs each.

It's the outer toons so I'm probably going to weight it down at the dock by letting water into the center toon and get enough blocks on it to get them underwater to see what's bubbling. I may leave it strapped to the trailer so that should help a little, but it's a square tube trailer so it's not that much weight in the water. It's kind or hard to ask a bunch of people to get on the boat and let me look for leaks even though it's not a sea-worthy issue. It's just a nuisance.

 

[fergusmj]

Re: Welding Strakes on Pontoons

wow...yep.. that's a lot of weight!

 

[HarborRat]

Re: Welding Strakes on Pontoons

To find small leaks in a car's vacuum systems they use what is called a "smoke machine". I'm not sure if the toons would be too large a volume for this to work, but maybe something to look into?

With a small smoke machine you could pull a slight vacuum on the toons and see where the smoke sucks in.

https://www.google.com/search?q=smo...sm=122&ie=UTF-8#q=smoke+machine+to+find+leaks

 

[arntarchie]

Re: Welding Strakes on Pontoons

get a stethoscope from the drug store, just like your docs. you will still need to check each weld but it makes it vary easy. when you come to a leak you will hear it. I am a welder by trade 35 years, I would love to see a photo of one of the welds, hard to say right now what happened to there welds a lot is going on with aluminum, my first GUESS is he used a mig gum, got to buzz en along and didn't clean the base metal good enough and got bad Fushun under the weld. aluminum must be clean to get a good weld. I would also ask if the logs had the plugs out at the time they were welded, if not the log can pressurize from the air inside being heated and blow out the molten metal and form a pin hole, it doesn't take much presser at all,
In any case you after you find a bad weld you should be able to cut out the weld with a 4" grinder without cutting into the log, clean it up and re weld.

 

[High Cotton]

Re: Welding Strakes on Pontoons

I wonder how much of a PITA it would be to seal them with a good sealer from the inside if that's even possible. Might require removing them..

 

[MaPaHa]

Re: Welding Strakes on Pontoons

I hadn't thought about the vacuum approach or the smoke. The smoke idea might work if I filled the strakes with smoke and put pressure in the toons. It might stir around in the area of the leaks. The vacuum could work as well.

arntarchie,
If you saw the welds it wouldn't take you long to figure out what happened. The guy that did the job no longer works for the welding shop but I know he used a spool gun that had a roll of wire at the welding head rather than at the machine. I'm not sure if that's still called a mig or not. The shop does a lot of aluminum boat and pontoon work but almost all of it is done with TIG. For some reason the guy decided to use the spool gun and I'm pretty sure he hadn't done many pontoon jobs with that welding machine from talking to him.

I need to step up from the old "garden hose to the ear" and get a better listening device. I think that would help a lot. I think my approach should be to find and fix the welds rather than cutting them off or welding them solid. You and BrianMc are both experienced welders and are saying the same thing.

One last welding question... where the strakes cross the pontoon joints every 5 feet, would it be better to weld across the joint or stay away from them an inch or two on either side? I want the strakes to give as much support as possible to the joint area.

At one time the joints had some leaks and were repaired but some of the repair welds are behind the strakes. They cracked when the boat was a twin toon while bouncing down the road on the trailer. The joints that cracked were the ones right above the axle hangers. Once I added the third toon and added a center bunk it took the pressure off the outer toons and had no more leaks there. I've also reinforced the trailer with a 3" x 4" x 1/4 angle iron down each side of the trailer the entire length. The strakes themselves should help give new support to the old toons also.

Thanks,

Mark

 

[Scott Danforth]

Re: Welding Strakes on Pontoons

I would take it back to the welding shop and have them repair the issue. if you paid for a service, you should be satisfied with it.

a spool gun works great for putting down large welds, especially in 1/4" or thicker. however the 'toon logs are much thinner

 

[BrianMc]

Re: Welding Strakes on Pontoons

I'd stay 4"-5" away from your tube joints incase you ever need to weld on the joint. At least you'd have the option of cutting a section of the strake out for access. That area of the joint should still be pretty stout without welding across it.

 

[arntarchie]

Re: Welding Strakes on Pontoons

Just from what you have said it sounds like you have a weld quality problem. and just because they don't leak air dosnt mean you have a good welds. Strikes put a lot of leverage stress on the welds and the thin skin of the log you will need to check for water all summer long. The guy may not work there any more but you still have a jacked up boat. I would find a 3rd party to look at what you have, a welding instructor from the community college or a welding inspector so you know what you have you could be chasing this problem for some time and my even need to get legal with the slop.

 

[MaPaHa]

Re: Welding Strakes on Pontoons

Thanks for the input.

At this point I'm trying to get the best outcome even if I have to put some work in it myself. Yes, in theory I should be able to distance myself and have them fix it but I'm concerned on "how" they fix it for the long term of the boat. That's a good point about any poor quality welds even if they don't leak. There is a lot of pressure there.

I'm going to try the stethoscope and/or see if any of my friends have a ultrasonic leak detector so I can find the welds or area of the leaks and then make a note of the poor looking welds on top of that. The owner of the welding shop has fixed a few of the leaks and the repairs he make look OK. He and I both are at a loss on how to find the rest of the leaks but you all have given me some good ideas on how to proceed.

After I do the test in my shop I'm going to take it to the river and get the strakes under water one way or another and pressure test them. Then I'll have some solid info to go by.

I'll keep the progress posted. Thanks,

Mark