Recent Chine Extrusion Experience

General boating discussion
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Re: Recent Chine Extrusion Experience


Post by alumioforte » Thu May 03, 2018 10:24 pm

Good points Kevin. I would far rather pay for an extra hour or 2 to get it welded. I know that some production builders like Alumaweld prefer the cleaner look of an unwelded exterior chine, but what looks nice in the showroom must stand the test of mother nature..and she dont care about looks.

I agree with your point, that if taking the time to weld those is that big of a deal, why not focus the attention elsewhere to minimize weld time! I am keeping my eyes on the adhesive industry; the aluminum F150 has no welds in it. A bead of aluminum adhesive at least could at least reduce this problem.

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Re: Recent Chine Extrusion Experience


Post by MallardRain20 » Sun Jun 17, 2018 1:54 pm

Just to clarify. If they are welded both inside and outside the hull there is no problem. Or is there a preferred method of construction that you see.

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Re: Recent Chine Extrusion Experience


Post by kmorin » Sun Jun 17, 2018 5:26 pm


IMO the chines built with the slotted extrusions should be welded inside and outside AND pressure tested to 3-5psi.

Many MIG welds have root porosity (gas pockets), just as many have cold lapped starts, and either condition can lead to a sealed void made at shop temperatures (60-80F). The gases inside the sealed extrusion is at the volume of proportional to the temperature it was sealed. That means; if the boat is put in water (most water) the temp drops 30 to 40 deg.s F; there is a vacuum formed inside the extrusion so this DP will try to 'pull' water in- the water is actually forced into any flaw by the pressure differential- inside the void compared to the ambient pressure outside.

In the opposite case; the same sealed chine (without pressure test) is heated by sitting on the trailer in 100F sunlight-and if there is a flaw in the weld seal (?) gas expansion will expel much of the gas from the "sealed chines slots": (let's say) that evening the boat is launched and left in the water overnight. Now the vacuum (relative differential pressure/DP) is much larger- greater force trying to get water into the "sealed" seam.

So, I think any void in any boat that is sealed by welding needs to be pressure tested to insure the integrity of the welds- so the void can have truly sealed welds. This will insure no water is pulled/pushed into a void (of any kind) and left to start a crevice corrosion cell.

I usually join the chines of most hulls sheet-to-sheet; edge-to-edge. If there will be a outside shape/extrusion added on to the chine, I usually A) stitch weld and make a drain path, or B) Seal weld and pressure test ( this latter option is much more expensive for the owner). There are good reasons to consider the huge mass, slotted chine extrusion for impact resistance and construction time reduction- but IMO if they're not built-in wisely, I think they will reduce the potential life of the boat.

NOTE: I expect the life of a welded boat of 5086 and 6061 to be 75-100 years useable life; TBD when more time on the originals is obtained.

Hope to have answered the question MallardRain20?

Kevin Morin
Kenai, AK

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Re: Recent Chine Extrusion Experience


Post by alumioforte » Sun Jun 17, 2018 6:33 pm

Well written, Kevin. Good points.

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