do i need to grind out bubbles in fiberglass bulkhead tabbing?

[sailormanbob]

I'm putting in some plywood bulkheads, stringers, bunks, counters, and things, an I was wondering if having some bubbles in the fiberglass tabbing is going to be any sort of problem. Here are some pictures. I was wondering: leave them ?or should I grind them with my dremel and then .... leave the bare spots, put little patches of 1708, or something else? I'm not worried about strength, I don't think, because I used two layers of 1708 and its only a 20 foot sailboat. I am more worried about: is it going to do something and make the interior of the boat wear faster? Thank you in advance for any advice you may have.

[Gary Mc]

They should not be an issue, just sand it down smooth and paint it, should look ok.

[HankOnthewater]

Gary Mc, if you used two layers of chopmat, and you have large air bubbles in between them, strength is reduced, maybe not by factor of 50% but fairly close to that. By grinding the top off, you are removing one layer, strength will be certainly less than 50% of a good 2 layer-layup. Note: multi layer layup is always more then the adding up of the strength of one layer.

If it was my boat I would grind the air bubbles out and apply another fresh layer over the top. Cost is very little, just more time. Sigh, will the work never stop? If there are only one or two little bubbles, maybe grind them off and finish with whatever you were planning to do, ie flowcoat.

On edit: Sorry, do not know what '1708' is.
Another thought, for load bearing stuff, two layers may not be enough, assuming you are using 450 g/M2 or similar chopmat?

On edit#2: Is '1708' a bi-axial tape with mat stitched to that? If both are relative heavy, then 2 layers maybe enough, but I am not sure. I used bi-axial cloth but not with this name.

[atoll]

Originally Posted by sailormanbob

I'm putting in some plywood bulkheads, stringers, bunks, counters, and things, an I was wondering if having some bubbles in the fiberglass tabbing is going to be any sort of problem. Here are some pictures. I was wondering: leave them ?or should I grind them with my dremel and then .... leave the bare spots, put little patches of 1708, or something else? I'm not worried about strength, I don't think, because I used two layers of 1708 and its only a 20 foot sailboat. I am more worried about: is it going to do something and make the interior of the boat wear faster? Thank you in advance for any advice you may have.

that crappy pine plywood will rot out and delaminate, if not painted properly long before the bubbles become a problem

[Privilege]

You've done a good job and small bubbles, as seen in your photo, are not an issue at all. They will always happen on bends and around corners and the only way to prevent them is to roll your wet glass with a barrel roller but I don't bother with one unless I need a smooth finish. For tabbing bulkheads and similar, a brush or roller is fine. The ply you used is also not really an issue as long as it is fully encapsulated in resin and cloth. It will last longer than you and I.

[Boatyarddog]

Grind what you can, they will draw water.
If you think strength is an issue, reinforce. Otherwise,just recoat with resin.
It is a bulkhead,and wood.
Once you paint, you'll forget that.
Next time if you get bubbles, just cut them open before the resin kicks, and roll out

[Cheechako]

Looks like you need a roller to roll out bubbles. They are cheap.

[Cadence]

I can't tell from the pics. I'd guess the bubbles are at the joining points (corners) in the future put in filets prior to glassing or radius the up side of the ply if that's wear the problem is.

[farmall.dude]

Looks like a lot of conflicting answers... might I suggest wandering over to Boatworks Today's website and ask him? https://www.boatworkstoday.com/
Hope that's not against the rules to post the link, sorry if it is; feel free to remove it. He's got a utube channel too, lots of good glassing information!
Good Luck!

[alansmith]

Sailorman, another approach that I learned while completely glassing my boat these last couple of weeks is this:

1. Find the highest point in the bubble. Take a small drill...and drill into the hole from a vertical axis...
2. Take a syringe with catalyzed resin and inject it into that void until it overflows. Allow the resin to harden. Sand off the miniscule drips.

You have plenty of strength with what you have done. Glass and resin and mat...An elephant couldn't crush that box.

This will strengthen the void considerably and you will avoid the grinder shizzle flying everywhere. Corners are not very much fun anyways.

Much good advice about rolling out already given. Make sure all of your edges of the ply are sealed with at least resin. But I like to use 3/4 oz chopped strand mat. It is very easy to work edges with...and easy to sand down for a smooth surface and get a more polished look. But really not that necessary for edges. But Atoll is correct that the edges need to be sealed or you will have grief later when she swells on you.

[phorvati]

Folks usually reffer to those bubbles as poor workmanship. Need to do a better job of wetting out glass. Another issue sometimes is the unsaturated glass. Properly wetted glass is completely see through. Any opaque areas could be bubbles or unwetted glass or fairing compound like bondo.