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Hi,

I built two 3d printed wings and covered them with four layers of fiberglass. The problem is, they take in water from the trailing edge where two sides join. To fix this, I added a strip of fiberglass to the trailing edge , and poured epoxy over the trailing edge. Thus the trailing edge of the wing is extended by about 0.5cm and the previous trailing edge is sealed with a thick layer of epoxy... Anyway... I flew the wings again, and they still take in water from the trailing edge... I am at loss about how this happens... Maybe it's not a good idea having any air inside the wings... Don't know... Can someone please explain how this may happen?

Hi,
handlaminated? How is the finish? Spackle and gloss or nothing.
How do you see that the trailing egde is the cause?
I would suggest to check for pinholes. With thermal differences from land to water and the bending under load while flying one tine hole can mess up everthing.

Dirk

laminate is almost always porous

3DP better for templates or molds.

Are you sure it is the trailing edge? I am thinking it might be leaking in thru your bolt holes. If you did not do a solid infill on them or fill them before laminating them.

Make two tiny holes apart, fill with 2 part PU foam from one hole...

dirk8037 wrote: ↑

Wed Jan 06, 2021 10:20 pm

handlaminated? How is the finish? Spackle and gloss or nothing.
How do you see that the trailing egde is the cause?
I would suggest to check for pinholes. With thermal differences from land to water and the bending under load while flying one tine hole can mess up everthing.

Hand laminated then vacuumed with clothes storage bag. Glossy epoxy finish, and then spray can paint over that. I know it's the trailing edge, because water seeps from the trailing edge slowly when I get back home. Small droplets form at the trailing edge slowly. I weighed the wing, it's taken in about 50 grams of water in one session.

tomtom wrote:laminate is almost always porous

The boards and wooden core wings I built with the same epoxy and glass are water proof. But these wings are not:( There's probably something more to it. Maybe the air inside...

TheJoe wrote: Are you sure it is the trailing edge? I am thinking it might be leaking in thru your bolt holes. If you did not do a solid infill on them or fill them before laminating them.

I have oversize holes filled with epoxy.

Here is a pic of wings before I extended and sealed the trailing edge:

More pics here:
https://www.thingiverse.com/make:801338

downunder wrote: Make two tiny holes apart, fill with 2 part PU foam from one hole...

These wings have an infill pattern that will prevent foam from spreading, but for future wings, I may choose an infill pattern that can be filled with foam.

I actually made the same wing but laminated it with carbon. I have not tried using it but I'll submerge it and test to see if it gets some water in the core.

Cubic infill. It forms closed pockets. You can't print with big layer height though, the infil walls slope at about 45 degrees. Also, change your extrusion width from % to absolute, say you have a 0.4mm nozzle, set the extrusion path to 0.45mm. This will lay down wider tracks that seal better over the layer underneath.

fluidity wrote: ↑

Thu Jan 07, 2021 10:15 am

Cubic infill. It forms closed pockets. You can't print with big layer height though, the infil walls slope at about 45 degrees. Also, change your extrusion width from % to absolute, say you have a 0.4mm nozzle, set the extrusion path to 0.45mm. This will lay down wider tracks that seal better over the layer underneath.

I already used cubic infill, but that's probably not enough to make it waterproof. As for extrusion width, with a 0.4mm nozzle I sometimes go up to .6mm wide extrusions. Maybe it leaks at the seams. I do not remember what kind of seam placement I picked.