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Gluing problems.

G

Guillaume Saucier

Joined
Jan 4, 2026
Messages
18
Points
48

Allo everyone,
Am I crazy, or gluing laser cut pieces is hard because the glue does not stick well on the laser burnt cut?
I'm building a frame right now, it's not the first one, but I keep seeing jointed parts separate?
Help anyone?
 
Thing is, the burn marks are in a zigzag joint which is already loose, so it's hard to sand AND will increase the looseness...
 
Corsair said:
use needle files in the joint. You will find the triangular file to fit great most likely. :)
The other option would be to glue some scrap on the outside, overlapping the joint.
Click to expand...
I will do that, I'm a bit maniac as far as frame straight is concerned.....
 
there is a thread here on SoS that tested different glues

Test of Different Glues on Differing Surfaces

In preparation for assembly of my Bonhomme Richard cross section, I am looking at different types of finishes (in particular Wipe-On Ply varnish and wipe-on Danish Oil). I'd love it if you would stop by there (Signet's Bonhomme Richard Cross Section). Since I've been told to never glue to a...
shipsofscale.com
 
Last edited:
Dave Stevens (Lumberyard) said:
there is a thread here on SoS that tested different glues

Test of Different Glues on Differing Surfaces

In preparation for assembly of my Bonhomme Richard cross section, I am looking at different types of finishes (in particular Wipe-On Ply varnish and wipe-on Danish Oil). I'd love it if you would stop by there (Signet's Bonhomme Richard Cross Section). Since I've been told to never glue to a...
shipsofscale.com
Click to expand...
Thanks a lot!!
 
Guillaume Saucier said:
Allo everyone,
Am I crazy, or gluing laser cut pieces is hard because the glue does not stick well on the laser burnt cut?
I'm building a frame right now, it's not the first one, but I keep seeing jointed parts separate?
Help anyone?
Click to expand...
You should scrape or sand off the laser burn
 
Guillaume Saucier said:
Allo everyone,
Am I crazy, or gluing laser cut pieces is hard because the glue does not stick well on the laser burnt cut?
I'm building a frame right now, it's not the first one, but I keep seeing jointed parts separate?
Help anyone?
Click to expand...

For the most part, successful gluing requires both mating surfaces to be flat and clean—free of grease, dust, and dirt. It helps to think of glue as creating a very thin film that bonds the two parts together; it is not meant to fill gaps or compensate for a poor fit.

Laser char itself is not the main issue. The bigger problem is that laser cutting often leaves a slightly zigzag edge, making the surface uneven. In addition, the laser beam cuts at a slight angle, so when parts are glued together, this can leave small gaps between the parts and weaken the joint.

Because of this, surface preparation is key. Light sanding or scraping of laser-cut edges greatly improves contact and joint strength.

Here are my Glue recommendations
  • PVA / wood glue should be the primary adhesive for structural joints. It provides working time, allows minor adjustment, and forms a strong bond when surfaces fit properly.
  • CA (cyanoacrylate) works best as a positioning or tacking aid to hold parts in place while the PVA cures. Used sparingly, it can be very effective, but it should not be relied upon to compensate for poor fit or gaps.
  • Thick or gel CA can be useful in non-structural areas, but excessive use often leads to brittle joints and alignment issues.
In short, good fit first, glue second. The better the surface contact, the stronger and more reliable the joint, regardless of the adhesive used. Always use adhesives designated for the given jobs!
 
All good advice here. I've relied on sanding/filing to ensure a smooth fit but have also heard that rubbing the char with isopropyl alcohol helps.
 
" AI Overview -
Wood char (charred wood) does not accept PVA (polyvinyl acetate) glue well primarily because the charring process destroys the porous, fibrous structure of the wood that PVA relies on for adhesion. "

As I found out recently, for the same reason - destroyed porosity - PVA does not work on wood stained with nitro stain that I use.
Other types of stain will most probably do the same.

That creates a problem - for example staining/sealing the deck planking after it is laid. Then later on trying to glue all the fixtures to the deck.
Or staining the 2nd planking, and then later fixing wales and fenders.

What do you do? Use CA?

cheers
.
 
Last edited:
aussie43 said:
" AI Overview -
Wood char (charred wood) does not accept PVA (polyvinyl acetate) glue well primarily because the charring process destroys the porous, fibrous structure of the wood that PVA relies on for adhesion. "

As I found out recently, for the same reason - destroyed porosity - PVA does not work on wood stained with nitro stain that I use.
Other types of stain will most probably do the same.

That creates a problem - for example staining/sealing the deck planking after it is laid. Then later on trying to glue all the fixtures to the deck.
Or staining the 2nd planking, and then later fixing wales and fenders.

What do you do? Use CA?

cheers
Click to expand...
Yes for that reason I don't do any staining or varnishing until everything is in place. It makes the staining/varnishing more challenging, but the last thing you want is for bitts or fife rails to come off while you're rigging.
 
Guillaume Saucier said:
Allo everyone,
Am I crazy, or gluing laser cut pieces is hard because the glue does not stick well on the laser burnt cut?
I'm building a frame right now, it's not the first one, but I keep seeing jointed parts separate?
Help anyone?
Click to expand...
I havent encountered this issue. Probably because I lightly sand the charred marks to remove them.
 
aussie43 said:
" AI Overview -
Wood char (charred wood) does not accept PVA (polyvinyl acetate) glue well primarily because the charring process destroys the porous, fibrous structure of the wood that PVA relies on for adhesion. "

As I found out recently, for the same reason - destroyed porosity - PVA does not work on wood stained with nitro stain that I use.
Other types of stain will most probably do the same.

That creates a problem - for example staining/sealing the deck planking after it is laid. Then later on trying to glue all the fixtures to the deck.
Or staining the 2nd planking, and then later fixing wales and fenders.

What do you do? Use CA?

cheers
.
Click to expand...
I use medium viscosity CA. No issues yet.
 
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