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Bubbling in polyester skin


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Hi.  I skinned last winter with Kudzu 8oz original and painted with an oil based anti-rust enamel ( the only tintable oil base sold around here ).   The paint went on well, looks great, has worn well, but over the winter a whole bunch of bubbles have developed along the gunwhales and a few along the chines.  There were two or three small bubbles that showed up a couple weeks after painting last winter, but they have multiplied considerably in this winter's storage!  Any ideas?

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The Tadpole I have suspended from the ceiling actually did the same thing to me over the winter.  I flipped it upside down in the straps a couple weeks ago and a little bit of it seems to be coming back out.  My guess and my hope is that when the warmer weather gets here they'll shrink back down.

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Thanks, it is always good to hear that you arent the only one with a problem!  :-).    This new one is skinned in the same fabric and is ready for paint - just hoping not to have the same bubbling show up.  I am going to try an oil primer down first and see if it makes any difference.  If nothing else it should limit the color bleed  visible inside the cockpit.   

 

We are going to gently go at the bubbles on the other with an iron, see what happens.  It is my son's build, and he is very fussy about things being right.  No idea where he got that from ....  :-)

 

 Tim

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Tim,

Nice to build boats with our kids, eh?

 

Not so nice when they expose our quirks by emulating them, eh? :)

 

I have used only latex paint on my boats for years, as oil based paints and supplies are harder to come by around these parts. I am applying it to my long suffering Firefly build in a much too intricate pattern, I realize too late.

 

I honestly think some of the new latex porch and floor paints are better than older alkyd style paints. Sorry grandpa. :)

 

Good luck!

 

Peace,

Robert

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The boys got both sides of me.   They each built their kayaks about 95% by their own hand.  My oldest I had to remind several times throughout about the importance of attention to details.  My youngest I had to remind many times that it doesnt need to be "perfect", it just needs to float ...   :-)

 

Latex it will have to be for any future builds, I got the dregs of the oil based at the store.

 

Tim

 

 

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Are the bubbles a separation of one layer of paint from those below or the skin lifting away from the frame? Did you thin your first coat of paint? I'm guessing that thinned paint will penetrate the fabric better and adhere to the frame a bit better than unthinned paint. Maybe an unthinned first coat could allow the skin to separate from the frame when stressed by different shrinkage and expansion rates caused by humidity and temperature changes.

Edited by DURRETTD
Poorly worded initial comment.
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14 hours ago, DURRETTD said:

Are the bubbles a separation of one layer of paint from those below or the skin lifting away from the frame? Did you thin your first coat of paint? I'm guessing that thinned paint will penetrate the fabric better and adhere to the frame a bit better than unthinned paint. Maybe an unthinned first coat could allow the skin to separate from the frame when stressed by different shrinkage and expansion rates caused by humidity and temperature changes.

 

It is the skin lifting away from the frame.  1st coat was not thinned, and was very light.  The skin is not stuck to the frame as far as I can determine, though I am sure there are spots of bleed through where it has bonded a bit.  The kayak has been stored in a coolish basement.  

 

And Robert, no worries on the grandpa comment, I figured it was something along that lines.  And if not, I have been called worse things in my life!  :-)

 

Tim

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Just a guess but I suspect that the shrinking is the problem.  Talking to the mills fabric when shrunk will 'creep' or stretch back out after shrinking (some). But when you add paint into the mix I have no idea what if any effect that has. Things like this really make me lean toward sewing on tight to start with.

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I find it interesting that in the examples shown the bubbling is over the wood stringers.  The rest of the fabric looks tight so it doesn't appear to be a general loosening of the fabric.  Did both builders use WRC?  WRC is known for not having much pitch.  However, I have read some descriptions of old growth WRC having "oily extractions", whatever that is.  I'm guessing some kind of reaction between the painted fabric and the wood although I have nothing concrete to back that up.  It would be interesting to hear what wood Tim E and Abbysdncr used.  If the first coat of pain is thinned, could it also adhere the fabric to the wood?  Could this be a factor?  Tim E did not thin the first coat.  What about you Abbysdncr? 

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8oz original for me.  Stringers are WRC, i wouldnt consider the stuff we get here anything close to oily.  The frame did get a coat or two of danish oil though.  The rest of the skin is still tight - I dont think it has relaxed much, if any.

 

Tim

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Well, will see how my experiment works, whether it makes a difference with bubbling.  I put a coat of oil primer down first before the antirust oil based color coats.  The primer definitely does a much better job filling the weave and pinholes, but it did seam to relax the fabric a bit - the rear deck is a little floppy now.  It didnt bleed through much if at all.   Also it changed the feel of the fabric - more stiff and cardboardy than just the straight paint.  A this point, I am probably leaning towards wouldnt do it again, but will see what happens over time.  ( 8oz original polyester )

 

Sorry, the kayak is a brand Y, but the skin, lashing, and backband are Kudzu!  :-)

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It is a bubble/bulge of the fabric, no separation of the paint.  There is nothing to pop as it isnt sealed against the stringers.  

 

I am going to try putting an iron to it if I get a chance before loading the kayak up tomorrow for a trip.

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  • 1 month later...

Actually havent put an iron to them yet.  I can attest though that a 3500 mile roadtrip on the roof of a minivan, from subzero Montreal to balmy Florida and back, had absolutely no effect on the shape, size, or appearance of the bubbles.... :-)

 

Tim

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