Which seam is superior in water resistance? “Plain seam VS Welt seam”

[Nenta WAKO, Dr.Eng.]

Companion forum thread to: Which seam is superior in water resistance? “Plain seam VS Welt seam”

The other day, I performed a seam test for water leakage without seam sealing tape. I confirmed why most outdoor backpacks have been made with plain seam that sews together on the inside.
It is superior to welt seam in process cost and water pressure resistance. Both of the seam types didn’t prevent water leakage, but there was a clear difference in the leak time between them.

[Dave @ Oware]

Twice as many needle holes with two rows of stitches. More leakage.

On the other hand, redundancy if one row fails and also the force on the seam is shared by the 2nd row of stitches.

 

[Nenta WAKO, Dr.Eng.]

Dave @ Oware,

Yes, and around the zipper, you should take into acount the effect of water penetration to grosgrain tapes and the zipper components due to the seam type.

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