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PVC (Vinyl) Fabric - ability to follow a curve?

Posted: Wed Apr 09, 2014 9:15 pm
by crizere
Hello everyone, I am looking for some advice from someone who has used PVC fabric (Vinyl coated polyester)
which I have never worked with.

I want to build a single chine boat from two pieces of ply wood with approximately the profile shown,
joining them a "hinge" of fabric. The idea comes from Tom Yost's Falco, but with only a single chine.
boat profile.png
boat profile.png (991 Bytes) Viewed 960 times
In this way it could be folded flat, but thwarts would be inserted to hold it open and force the boat into shape.
(see pictures, apologies for their poor quality) I realize this boat would be very unstable, I plan to attach an outrigger.
Boat fold.jpg
Boat fold.jpg (11.71 KiB) Viewed 960 times
It seems that for the fabric to follow that curve at the bottom, it would need to stretch some what in order
to follow the curve while also being flat against the plywood in order to bond and make a seal.
I am also somewhat concerned about the ability to join the gently curving bottom portion and that straight
bow portion without gaps and leaks.

I suspect it is possible to do so because of the way Mr Yost constructed the Falco, but want input
from someone who has worked with the stuff.

If it seems like it would be challenging,
I have wondered about using a heat gun to help stretch, or shrink portions of the material to help it make
the curve. I read an article about an upholsterer using a heat gun when covering certain pieces of furniture,
to help the fabric make curves, but don't know if it was the same type of fabric or straight vinyl.

If PVC won't work, I think I could use an uncoated polyester or canvas and paint it,
as this seems to be the way people have done the hinges in plans I have found for the boat pictured
in the black and white photo. However it seems that PVC fabric is a tried and true and I would prefer
to use it if possible.

Fiberglass with GFlex epoxy also seems an option, though I hope to use epoxy primarily as an adhesive,
because I am a cheap skate.

I am sure that my post is horrendously unclear, please let me know how I can clarify,
and thank you in advance for any advice.
FoldingKayak0001.jpg (9.11 KiB) Viewed 960 times

Re: PVC (Vinyl) Fabric - ability to follow a curve?

Posted: Sun Apr 13, 2014 2:52 pm
by gmchris

I did my 'falco' style boat using this type of pvc coated polyester material. It basically has no stretch to it, maybe only one or two percent, so although it may start to follow the curve, it will wrinkle once the curve tightens. I think it would be neater and easier to cut a piece for each side and allow an extra 20mm along the bottom of side 1 to curl over as a flap to glue onto the bottom edge of side 2. I found that by folding the fabric to mark where the edge will be, then masking off with tape and gluing up to the tape, a real neat seam can be made. I have tried heat welding but although it is quick and easy to do, the fabric around the weld can pucker and ripple so it's not a pretty job. And using glue I had no problems with water tightness, but heat welding may not be so reliable. I also tried to stretch by heating but the fabric showed through the pvc where it got thin and generally looked bad, but that was just my experience.

Re: PVC (Vinyl) Fabric - ability to follow a curve?

Posted: Thu Apr 17, 2014 4:14 pm
by crizere
Thank you for your reply, I really appreciate it as you have tried some of what I was thinking.
gmchris wrote: think it would be neater and easier to cut a piece for each side and allow an extra 20mm along the bottom of side 1 to curl over as a flap to glue onto the bottom edge of side 2.
Just to make sure I understood what you meant, you were thinking of something like this:
boat hinge.png
boat hinge.png (4.1 KiB) Viewed 939 times
Do you think the bond will be strong enough with that little surface area?

Again, thank you very much.

Re: PVC (Vinyl) Fabric - ability to follow a curve?

Posted: Tue Apr 22, 2014 8:40 am
by gmchris
Yeah the diagram you have drawn is what I meant. 20mm overlap may be a bit shallow so go up to 30mm if you like, but my boat is holding fine on 20-25mm overlap seams. I have used hh-66 and painted it on,and also pvc flexible glue from a 25ml tube with good results. I paint both surfaces, let it dry for 4-5 mins, then give it a quick breeze with the heatgun just to make it extra tacky, then stick together and immediately run over giving a good press with a wallpaper roller. Try not to pull apart as I found it doesn't achieve full strength till overnight, but then it is as strong as the original fabric. I tried to pull a test join apart after 24 hrs and the fabric ripped at my pliers not the join!