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Aluminum Stress Cracks


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Hey guys, looking for some wisdom here. As the title says I have some stress cracks in the bottom of my aluminum boat. The crack is located underneath and partially to the side structural support in the rear of the boat, behind the driver seat. Roughly the size of a toonie. I had someone tig weld the crack closed. My question is has someone here had any experience with this type of problem? Will the weld I had done Be enough to fix the problem or will it continue to crack? Should I have a welded or riveted patch put on top of the weld? I apologize for the numbers of questions, just don’t really know how to fix it properly and permanently. Attached are pictures of the crack from the bottom of boat, inside the boat (front and back of the crack location), and with the crack welded closed. Any help or advice is greatly appreciated.  

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0F448DEB-01C5-4B76-90B8-1B1828F6F1B6.jpeg

C8B57258-CDF6-4160-9824-0CEB41CF671B.jpeg

Edited by Musky Plug
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I think you will be fine 

if there is a lot of flexing or stress that that point the aluminum around the wield will now be the weak point    But I think you should be good to go

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So the original crack... is it pushed out from the sharp corners of that welded on seat or platform channel? Did you/he stop drill the ends of the three cracks before welding that blob on there? It'll last for awhile, but I suspect it will crack open again as that channel continues to work the bottom skin. All you can do is keep an eye on it. I would have put a heavy patch on it, welded boat or not, to distribute the load. You would have to grind that weld down to do so now and I don't advise that at this stage, all  you can do is wait and see.

1409319359_boatrepairsapril42009003.jpg.dd3449695a2c5467079b7b54345861fc.jpg

boatrepairsapril42009 006.jpg

Edited by irishfield
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11 hours ago, irishfield said:

So the original crack... is it pushed out from the sharp corners of that welded on seat or platform channel? Did you/he stop drill the ends of the three cracks before welding that blob on there? It'll last for awhile, but I suspect it will crack open again as that channel continues to work the bottom skin. All you can do is keep an eye on it. I would have put a heavy patch on it, welded boat or not, to distribute the load. You would have to grind that weld down to do so now and I don't advise that at this stage, all  you can do is wait and see.

1409319359_boatrepairsapril42009003.jpg.dd3449695a2c5467079b7b54345861fc.jpg

boatrepairsapril42009 006.jpg

Yes, from the rear corner. No I did not drill stop the corners. I did not read to do that until after I had the weld done. Could I not have the welder knock down the patch enough to put on a patch or should I just leave it?

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18 minutes ago, irishfield said:

Just leave it for now and see what it does. It may last your lifetime, may last a season. How old was the boat when this crack appeared?

Ok. Trying not to open a can of worms here, however this is a used boat I purchased December last year and wasn’t made aware of these problems, I was mislead during purchase process and at the time of the purchase I was unable to water test due to weather. So it unclear as to when this happened. 
 

If a patch is needed, what type of rivets should I use or should the patch be welded?

Edited by Musky Plug
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Appears you have full access to this area on the inside, so personally I would buck solid rivets on the patch. The one I showed above had zero access and is done with mandrel pull style "tank" rivets that have solid ends vs the normal style hollow pop rivets. I don't weld any aluminum thinner than 0.125" thick and even at that I'd rivet it if I can!

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19 minutes ago, irishfield said:

Appears you have full access to this area on the inside, so personally I would buck solid rivets on the patch. The one I showed above had zero access and is done with mandrel pull style "tank" rivets that have solid ends vs the normal style hollow pop rivets. I don't weld any aluminum thinner than 0.125" thick and even at that I'd rivet it if I can!

Based on the experience of acquaintances I wouldn't buy a welded boat under .125" either, starting with an '88 Crestliner they have been bad, maybe they have sorted out the welding by now but seen too many cracks lengthwise ,  immediately adjacent to the welds.

Edited by dave524
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51 minutes ago, irishfield said:

Appears you have full access to this area on the inside, so personally I would buck solid rivets on the patch. The one I showed above had zero access and is done with mandrel pull style "tank" rivets that have solid ends vs the normal style hollow pop rivets. I don't weld any aluminum thinner than 0.125" thick and even at that I'd rivet it if I can!

Would I be able to get the solid rivets at brofasco or a similar place? And should I use 3M 5200 on the patch as well? 

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I use Sikaflex1A building aircraft floats (or Rona now has Sikaflex as well that's near as good for about $7.50 a tube). No need to blow your funds on 3M5200. I have a bit of rivet stock for my own use, but anyone can buy from www.aircraftspruce.ca and get the proper larger heads for marine use. 

 

Inventory 034.JPG

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2 hours ago, irishfield said:

I use Sikaflex1A building aircraft floats (or Rona now has Sikaflex as well that's near as good for about $7.50 a tube). No need to blow your funds on 3M5200. I have a bit of rivet stock for my own use, but anyone can buy from www.aircraftspruce.ca and get the proper larger heads for marine use. 

Would these size rivets be appropriate? 
 

https://www.fastenal.com/products/details/11138207

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2 hours ago, Musky Plug said:

Would these size rivets be appropriate? 
 

https://www.fastenal.com/products/details/11138207

All depends on your patch thickness, boat hull thickness and if you want to tie into that channel as well. Rivets need to be the total of all material thickness + 1.5 x the rivet diameter to get a proper "shop head" when you buck them tight. 5/32 diameter would probably be large enough, not sure you need to go up to 3/16ths... but those are the right larger heads that get used on boats..

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On 5/30/2020 at 5:24 PM, grimsbylander said:

You should just drive it to Penetang! :rofl2: 

 

I’m willing to travel  lol 

 

On 5/30/2020 at 6:20 PM, irishfield said:

All depends on your patch thickness, boat hull thickness and if you want to tie into that channel as well. Rivets need to be the total of all material thickness + 1.5 x the rivet diameter to get a proper "shop head" when you buck them tight. 5/32 diameter would probably be large enough, not sure you need to go up to 3/16ths... but those are the right larger heads that get used on boats..

Ok awesome. Thanks. 
 

I wasn’t able to take out the boat today. Hoping I can make it tomorrow after work. Will post how I make out. 

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  • 1 year later...
Posted (edited)

Hey guys, long story short I my boat is taking on water again this time I think from somewhere under the bunks. Dropped the boat in last weekend for the first time and almost immediately started taking on water. I noticed when my boat didn’t even out on plane. Took the boat out and a fair bit of water drained out. I have looked at the areas inside the boat by removing the back deck but I could not see much. I have also re assessed the plug the live well hoses and intake and the bilge system both are in working order. In order to see the areas I must lift the boat up. I have found boat jacks but are these worth spending the money on or is there a better/ easier solution?  A friend of mine also suggested first filling the boat with some water to see if it leaks from the suspected areas instead of spending the money on the jacks? I have done this with small tin boats but not a boat of this size. Any help is appreciated.  
 

Edited by Musky Plug
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Are you 100% sure the livewell lines aren't leaking? Put a plug in the livewell drain hole in the transom, and try again? Where are you located? What size boat is it? 

To get my boat off the trailer I used my trailer tongue jack. Crank it all the way down as far as it will go, then block the transom solid. Now, crank the tongue jack all the way up and the transom will lift off the trailer. Once you have the jack all the way up, block under the keel at the bow, and let the jack down enough that you can see the whole hull. I have done this several times to replace my trailer bunks over the years, and once to paint the boat. It works, just make sure you have it blocked up good and solid. 

S. 

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Yes, I’m fairly certain that they aren’t leaking. I used blue tuck tape over the drain holes of both live wells and poured 5gallons of water in each live well. I had the back deck removed and did not see any water anywhere, and no water leaked out from behind the tape. It is a 05 16.5 crestliner fish hawk. I am located in the burlington area.
 
what did you use to block the transom? Do you have any pictures? 

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2 hours ago, Musky Plug said:

Hey guys, long story short I my boat is taking on water again this time I think from somewhere under the bunks. Dropped the boat in last weekend for the first time and almost immediately started taking on water. I noticed when my boat didn’t even out on plane. Took the boat out and a fair bit of water drained out. I have looked at the areas inside the boat by removing the back deck but I could not see much. I have also re assessed the plug the live well hoses and intake and the bilge system both are in working order. In order to see the areas I must lift the boat up. I have found boat jacks but are these worth spending the money on or is there a better/ easier solution?  A friend of mine also suggested first filling the boat with some water to see if it leaks from the suspected areas instead of spending the money on the jacks? I have done this with small tin boats but not a boat of this size. Any help is appreciated.  
 

The last think you want to do is put a lot of water inside the boat, boats are made to keep water out, not in.  The stress is a whole lot more.

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I put about 8” of water in my boat last year.  It was leaking a lot. The plug wasn’t tight enough.  The screws though the transom for the transducer.   Lots of rivets and must be a crack under the keel.  Paint can stop some of the leaks.    I put some silicone on it and I’m going to get a second bildge pump.   It gets water in it when it rains anyway.  
 

keep working on it you’ll get it stopped.  

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On 6/6/2021 at 12:39 PM, Musky Plug said:

Hey guys, long story short I my boat is taking on water again this time I think from somewhere under the bunks. Dropped the boat in last weekend for the first time and almost immediately started taking on water. I noticed when my boat didn’t even out on plane. Took the boat out and a fair bit of water drained out. I have looked at the areas inside the boat by removing the back deck but I could not see much. I have also re assessed the plug the live well hoses and intake and the bilge system both are in working order. In order to see the areas I must lift the boat up. I have found boat jacks but are these worth spending the money on or is there a better/ easier solution?  A friend of mine also suggested first filling the boat with some water to see if it leaks from the suspected areas instead of spending the money on the jacks? I have done this with small tin boats but not a boat of this size. Any help is appreciated.  
 

You might want to join up at tinboats.net.  There are guys on there that are a wealth of information on tin boats.

https://forum.tinboats.net/

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The 1st thing I thought when I 1st read your post was how blessed you are to know exactly where your crack was. I know folks that have been searching for the source of leak(s) on both glass and aluminum boats. The 2nd thing I commented to myself was what a mess the welder made of that repair. As I read on I am so glad you are listening to Wayne/Irishfeild as how to repair a crack. I can see that the ends of the cracks avenues were not drilled, the drilling of a hole at the end of a crack in metal, every metal that cracks that I am aware of anyway, will hopefully stop cracking at that point, it interupts the crack so to speak. The 2nd pick Irishfeild has provided of a repair is what your repair. I have to ask how old the boat is. There are experts out there that insist all pleasure boats. both tin and glass have a best before date depending on manufacturer, maintenace, good or bad, how used or abused for example. My Starcraft is a 96', 25 years old, experts say it's best before date is 18. Used like it was about to break, never WOT, maybe 3/4 of red line, once a year maybe wide open to clean carbon like our excuse in the old days to drive the family car like it was stolen. I am looking for a leak now, not surprised nor upset.

Listen to Wayne. If you want many good opinions join iboats.com. It's a boating forum with over 100,000 members World wide. I have been a member for years and the opinion Wayne gave is exactly what you will get there; , regardless I highly recommend iboats. It's an easy forum to follow, well organized and well monitored, no children unlike many forums. 

Edited by Old Ironmaker
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I think their best before date is probably calculated with algorithms relating to people puttering about to the ones that launch and go full throttle 3 feet past the dock and pound 4 foot waves.  Mines a '96 and no leaks either, but, I'm of the belief that if you want to wreak it, it can be done on your own dime.

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