Boat leaks, hull structure on 22 foot north river.

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Boat leaks, hull structure on 22 foot north river.


Post by dflorea » Fri May 12, 2017 7:45 am

Is there a way to check the hull. Brackets etc. visually for problems (cracks or leaks) on aluminum hull. I'm a novice with alloy boats and I'm looking for a used boat to buy. The reason I'm asking is that I read in another post how An aluminum manufacturer had leaks on motor bracket.

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Re: Boat leaks, hull structure on 22 foot north river.


Post by Chaps » Fri May 12, 2017 9:18 am

With boat on trailer fill the bilge or the bracket with water and see if any water leaks out
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Re: Boat leaks, hull structure on 22 foot north river.


Post by kmorin » Sun May 14, 2017 5:06 pm

dflorea, I don't have tons of photos of welding errors, mainly cold laps or crater cracks; to show as examples. Those are the most common welding flaws you'd find visually inspecting a welded boat.

One post, or anecdote about a leak in one bracket is kind of thin to base any assumption there will be leaks commonly in a welded aluminum boat. When I built full time in the 70's and 80's I had many years of leak free boats but I did air pressure test the voids/flotation cells to insure integrity. So, I'm cautioning you not to take one tale of woe as a rule of thumb about the entire industry of either production welded boats or one-off & short-run builders' products.

With that said, weld regularity or uniformity is a good sign of welder skill, practice, correct welding adjustments and weld integrity. I'm not saying that all welds that look good ARE sound welds, but I'm saying that a full time welder usually puts down a uniform bead, that is welder is likely to be using the correct preparation and settings to get those beads; so uniformity is a good indicator of sound welds.

Next, let's dig a little into uniform welds- if the weld you inspect is a hull seam (?) then it will be tied into other adjacent welds since we don't usually see welds from bow to stern without stop. The tie-in or lap or start stop areas are a very important place to look. If a weld has three main points - beginning, the run, and the end- the more uniform they are- the more experience that welder probably had when the weld was put in.

If you see a lump of weld every 10-12" or so, and that lump is higher than the rest of the weld around it: THEN look closely at the lumps' edges. When you start a MIG (metal inert gas or wire feed) weld there are 'cold laps' or places where the weld is not fully fused to the metals it joins- not all welds are like this mind you- but if you see a lump- then take time to look where the 'lump' melts to the two parent metal pieces AND the end of any adjoining welds.

If there is a black line, instead of a flowing of melted metal- this can indicate a cold lap or place where the two welds are not fully welded and that is potential leak area.

The more experienced aluminum MIG welder and boat builder using these skilled craftsmen will most often cut the first weld out to a hollow place in which to put the next weld's first few puddles of weld. Further, the skilled welder will begin 1/2" away from the 'tie-in' and as the arc "iights up"/begins/initiates will rapidly move the torch to the right (discussing a right hander welding from right to left) and tie the newly molten puddle to the hollow that has been cut in the end of the old weld- and then reverse the weld continuing to the left.

This 'race tracking' done by a long time MIG welder will leave the overlap or tie-in of the two welds very hard to spot- and the fusion of the welds is usually very good too.

So one of the ways to critically examine welds is to look at the tie-in's where welds begin to see if they're fused fully- both from weld to weld and the weld's fusion to the two parent metal edges.

At the end of a MIG weld the arc core reaches down into the parent metal if the weld is correctly adjusted. If a welder simply lets off the gun/torch/wire feeder trigger the weld instantly stops but... the aluminum of the weld puddle is still molten. As this molten puddle cools it will form a crater crack. The reason for this crack is the very high heat of the molten metal being heated by a welding arc means the aluminum is very expanded. Almost 20% larger in volume at the very core of the weld (hottest spot in the puddle) so when them alloy plus filler wire metal cool- they contract. The cooling contraction from full weld to room air temp usually leaves a crack at the very core/center/middle axis of the formerly wetted puddle.

To avoid this, most experienced welders either #1 whip the wire out of the puddle, (not always possible) or #2 double back one puddle. (some welding power supplies allow a programmed slowing of wire to the puddle, reduction of welding power, and gradual slowing of heat to the weld while still adding enough wire to avoid much weld shrinkage/contraction/crater cracking. I'm not discussing those programmable power supplies here.)

If a MIG weld is going to be part of a long seam- chines, keel, sheer, deck.... etc. then whipping out is fast and reduces both cratering and prep for tie-in. MIG weld is 'whipped out' by simply leaving the trigger on, and rotating the wrist holding the gun very rapidly while simultaneously letting go of the trigger. This leaves an increasingly smaller, narrower, thinner puddle 'smeared' into the weld area. What it also does is to mean the weld's 'smeared' end has little or no crater. So you can tie-in the next weld with little or no gouging by power tools, and no crater to weaken the final weld.

This method won't work well for a series of 'stitch welds' tying a flat bar stringer/longitudinal/"long" to the hull as those welds won't become continuous and need to be fixed length and end without any tapering off or craters.

The other method of ending a MIG weld is to change speeds at the last puddle and move 180 for one puddle and let off - this will leave any crater as a surface dimple to the existing weld, it will have no depth to the crater since the weld will be ontop of the last puddle in the same bead.

Either method of ending a weld can be done with very different levels of skill (6 string guitars are remarkably the same but the sound different people can produce from the same essential instrument is a matter of skill) and produce different looking welds.

But one way to determine if a boat was welded with high skill or low is to pay attention to the welds' beginnings and ends- they speak for the welder and the builder and will help you predict the quality of welding in that boat.

Kevin Morin
Kenai, AK

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Re: Boat leaks, hull structure on 22 foot north river.


Post by dflorea » Sun May 14, 2017 9:26 pm

Great! Thanks for the info. I've seen mig welding in action in a bronze sculpture class and have seen continuous thick seems one inch thick welds on plate Steele. I'm familiar with "running the bead". Seams, and puddling. Being an artist I can recognize good craftsmanship. I will examine the hull and motor bracket more closely after the bank accepts my offer and when I sea trial. Thanks for your feed back. I've been burned on boat purchases two times.

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