Hi Jose, 

these don't look too bad.  especially for a first effort. 

if you have not filled the weave yet, i would just sand over these bubbles to open them up (kind of like how you open a blister on your skin) and epoxy over them with epoxy as part of your filling the weave process.  you will find if you just take a little sanding block with 80 grit sandpaper across the top of these bubbles, that the top of these 'blisters' will first turn white, then come off.  vacume the dust out and then just proceed with filling the weave.

they are small enough that its not worth patching, but bubbles like these do often end up becoming  place that water will find its way to later so i would address them per my suggestion..  

anyway, i have built a lot of boats and have seen these before, and based on what i see, that is how i would handle these.

h

   Thank you so much for taking the time to look at the photos and responding. That is better news than I expected. Is there a size of blister at which yo would consider patching or filling in?

Hi Jose, 

the first level concern regarding bubbles is,  'are you creating a space where the water can get into the wood?'  there are two ways this happens: 1) you have a place that is not coated with epoxy (potentially under a bubble) or 2) you create pocket which can hold water against the wood leading eventually to the water intrusion (again, a bubble is a great candidate for this).  so by opening up a bubble you can ensure the wood that was underneath it is coated with epoxy and by opening it up, you get rid of a place that can hold water against the wooden core.

fwiw, in the old days, in many cases, plywood was simply painted with epoxy to ensure it was waterproofed.  however, it is typically much sturdier to maintain the epoxy encapsulation of the wood if it is part of a layer of glass....and that has become standard practice in many cases now.

the next concern with bubbles is that the strength of the boat.  these are really composite boats...not wood boats.  there strength is a function of a 'sandwich' of epoxy/glass, wood core, epoxy/glass.  this works similar to a corrugated piece of cardboard....a light and stiff composite becuase of how it all works together.  but when the glass is not bonded to the wood (e.g., underneath a bubble), you don't get this effect.   that said, a small bubble is not really going to effect strength....and so for me,  i only go to the trouble of a glass patch when my bubble is larger than a square inch or more.

anyway, these are just my personal guidelines.  like i said, in some cases the glass is really there for enuring waterproofness of the core.  in certain cases, it is really needed for strength.   most of the smaller plywood boats actually have plenty of strength  with just the wood. so while i have given a general view of not patching unless the bubble is an inch or more....how i behave also depends on where the bubble is and what kind of boat i am building.

hope this helps

h

   Great response hspira! Thanks

Warren

   Thank you for the detailed explanation h. This is very helpful. This is my first boat and I am learning every step of the way. 

J

Thanks for the post Jose.  The same thing has happened to me.  Did they sand down nicely?  Mine look like they may be between the two layers of glass rather than between glass and wood was that the case with yours?

I have still got 3/4 of the interior to glass.  Has anyone got any hints on how to avoid them?

Paul

   Paul,

Yes, I have been able to sand them down. I did not have the issue of them being between layers. To avoid them I think 1) be careful to check your work right after glassing and squeeze out any potential spots 2) lay the glass very neatly to begin with, 3) I suspect some of the small one could be caused by glassing if the temperature is rising, 

Jose

 Thanks Jose

Good to know that sanding works.

I have been glassing the interior one section at a time which for a beginner makes it easier to learn from my mistakes.  Working in slightly warmer temperatures and with warmed epoxy seems to have made the job easier - the glass seems to wet out better with runnier epoxy.  Pricking any bubbles with a sharp craft knife while the epoxy is still wet seems to help - some just collapse under their own weight.  On this last section I made a conscious effort to use less epoxy which also seemed to help - it seems easier to shift the bubbles when the weave is still prominent than when it is well soaked.

Just the bow section to go now, then flip it over and work on the outside.

Paul