Kiteboard Wood veneer Pressing Troubleshooting

General Discussion
1

Hi Sways,

First Build of a kiteboard with a friend, we have a problem with the veneer pressing, maybe you guys can help ??

the room is down in a cave, maybe a little bit humid, and a bit cold (its winter in europe).

Board:  136cm x 38cm x 0,9 cm approx.

Construction: Several sheets of spruce Wood veneer pressed together with wood glue. Then aimed to glass very simply with glass and epoxy.

Basic Rocker table with 4mm Plywood as base,

put veneer sheets + woodglue on it (board core),

put another 4mm ply sheet on top of veneer (just to press everything down, not part of the board),

press down. (like a sandwich).

The problem that happened: we pressed 3 sheets of veneer, left it overnight, look what happened =( . See the pictures attached.

The sheets glued together, but instead of staying flat, it had a wavy form, the difference between the up / the peak and down of those waves is pretty big, 0,5 -1 cm ! Since we put tons of pressure, evenly distributed, everything pressed flat / there was no room for moving, and the ply from the rockertable stays rigid, we want to know what caused the veneer to wave / rifle.

Our Hypothesis: We put wayyy too much wood glue.The water from the glue caused the veneer to shrink /deform, the pressure from the water entering the wood cells exceeded the clamping pressure of the press (you know like when a seed / root grows through the concrete on the street). That caused this wavy-ness.

We then did a test pressing with two very small pieces of veneer but put way less glue. it pressed nice evenly and its flat .See the last 2 pics.

 

You guys had same experiences ? What are your hypothesis?

Thanks !!!

Gabriel

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2

Humidity and to much glue may have been the reason, but you may have a problem due to wrong alignment of the veneer too. You have to switch the layers, one with the grain and the next one cross orientated. It may be much easier with a plywood core, even relatively thin, that will become laminated from both sides.
Additionally I would recommend using vaccuum, which gives equal pressure everywhere.

3

Like Surfdude said above, I would use a vacuum press. Water based wood glues will also contribute to the problem as the wood cells asorb the moisture from the glue & expand. I would glue the layers together with epoxy & a vacuum press.

4

Definitely looks like too much glue as others have said. Veneers need a very thin layer of glue. If you don’t want to use epoxy there is wood glues specifically design for veneers, cold press veneer glue. Also hide glues can be used, but they tend to be more work. To keep the glue layer thin I’ve used a small nap paint roller, but I’ve also seen people use notched spreaders.

5

There are products that supposidly soften veneers so they can be laminated easier. See joewoodworker.com for info. You may still be able to save that veneer on the board. I think you could have used pin holes placed in the veneer about 6-8 inches apart to help the glue escape from between the layers. A good idea if you try to use this laminate on your board. Vacuum is a must to move forward. I don’t think you’re going to get it completely flat on the board but with three layers you could sand it flat after appling it to the foam. I use one layer of paperbacked veneer and it is probably equal to a layer of 10 oz. glass. Three layers of wood with alot of glue should be super stout.

6

If your using a water based wood glue and intend to leave the wood grain exposed (not painted over with paint), DO NOT put pinholes in the veneer to allow the glue to escape. If you do & then stain the veneer, it won’t take the stain at the same rate & you’ll see EVERY pinhole as a “light spot”. If you leave the veneer natural, then you’ll still end up with “light spots” when the rest of the veneer darkens with oxidation from the UV rays of the Sun.

 

7

Surferdude’s comments are spot on.

Also it looks like you are using rotary-cut veneer which is not very stable because of the way it is made. So alternating the grain orientation is even more important than if you had used a sliced veneer.

I don’t know what thickness veneer you are using, but just by looking at it, three layers is not going to make a core thick enough to make a reasonably stiff board.

When I used to build a lot of wood kiteboards, I usually used 3 layers of 3mm plywood to make boards that were 9mm thick. I also laminated the layers on a form that had 3mm concave running down the center of the board (rocker plus concave) Compound curves made a bottom shape that I like, but it also made the lamination much stiffer than the same thickness with just a simple curve (rocker only).

I always used a vacuum press and epoxy. With the vacuum press I could laminate board blanks 3 at a time.