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#12881
I would like to have panels with topstitched diamonds on the pontoon seats I am redoing. I'm worried about water infiltration. The foam wil be covered with silk, but it seems to me that the skrim and back of the vinyl will get/stay wet. How would I be able to make the seats waterproof in this case? (Or in general, are topstitched seams waterproofed in some way?)

I did a quick test, and using sunguard B92 with a #18 needle, a bit of water on the front quickly seeped through to the skrim.
By Rug Dr.
#12884
That's life, water will get into any stitch. I've been building boats for a long ass time, it's just the way it is. The only NO NO with boat interiors is "NEVER KNEEL OR STAND on it". Pleats, french stitch, water will get in, cover the foam with plastic, use plastic backed scrim as well.
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By BigRig
#12887
@Rug Dr. ,

I would like to know more about the plastic. Is this a particular gage of clear vinyl plastic you are referring to ? I have not used a plastic backed scrim yet either.
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By Adam12
#12889
I like to try to give it a way to breathe whenever possible. Using underlining mesh on bottom or back. Cant stop water getting in, i like try to help it get out. Plastic backed scrim sounds quite interesting though
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By John
#12900
@County Line Custom I agree that there is no reasonable way to avoid that. I have seen people use HH66 vinyl cement brushed to the back side of seams. That probably helps a lot but would take a considerable amount of time.

Also there are varying opinions about wrapping the cushions in plastic. Some people believe it helps others believe it makes it worse. In my experience I think the wrap makes it worse because the water still finds a way past the plastic wrap and now that water its trapped in the cushion to mold. Every marine cushion I have ever uncovered that has that wrap the foam is still soaking wet. My opinion is at least the vinyl cover is breathable and will allow the cushion to dry. I also recommend to my boat customers that they should install vents in their boat cover. Otherwise you will have mold problems when those cushions try to dry out and the moisture is trapped in the boat by the cover.

@BigRig The plastic wrap we are talking about is called cushion wrap, silk wrap and probably multiple other names like everything in upholstery. Its a very thin plastic material similar to what painters use to cover furniture. This plastic is soft and thin and wont make a crinkle noise when you sit on it. It also works well for sliding on tight fitting back rest and head rest covers because it can be left on under the cover.
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By MalcolmM
#13325
For a cushion back on a boat I made, mounted vertical, I installed small grommets along the bottom to let water drain out. Every time someone leans back on the cushion air is pumped in and out of it. I also used uncoated acrylic fabric so the heat of the sun would evaporate any moisture right through the fabric. For a seat cushion or mattress I would also use uncoated fabric, and sew in a large bottom panel of pvc heavy duty mesh. I have used heavy duty screen door mesh and find its very tough material. Sailrite sells a sample foam box with a variety of regular, closed cell and drain through foam so you can see and feel what the products are like. For a seat bottom I would use a layer of closed cell foam, punch drain holes in it, then use the drain through foam on top to make a laminate. For interior I would likely Dacron wrap, but for exterior probably not. Make sure your construction techniques account for somewhere for the water to flow or wick out. Vinyl can easily be substituted for acrylic, but making sure drainage is not obstructed as vapor will be trapped in the cushion.
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By anna2008
#15787
If you want to build a bench seat for your boat, I will give some tips for you about this DIY project. Depending on your DIY boat seat design, you might want to drill mounting holes on the hull’s inside surface. You can mark the location of the mounting hardware to make drilling more efficient and accurate. Secure the angle bars on the boat’s interior sides with heavy-duty screws. Place the bench seat on the angle bars and fasten them with screws. Do not forget to add washers and gaskets to the screws to minimize water ingress.

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