Warps and sags.

[Country Modeler]

Hello again,


I recently finnised my 2nd flying model. It is a Guillow Super Cub 95. It flys good but has a small warp in the wings and the tissue sags a little bit in the first bays of the leading edge. What are some ways to prevent/fix these problems.

Country Modeler

[Wildpig]

If the tissue sag, won't come out with misting with water or alcohol, you probably need to cut off the bad section and just put down new.

Warpage can be difficult to fix. I've heard you can steam the wings,like from an old tea kettle. This softens things up and then pin the wing flat or somehow hold it straight until it dries out.
If the wing did not have any warpage before you covered it, then you covering technique needs a modification. You might have shrunk one section on one side. Instead it might need to be evenly shrunk on both sides. Hard to say. There are other modelers on this forum that have way more experience with this than me. Might just need a little trial and error to find the best method.

[Pauli72]

One thing that may have contributed to you having tissue sag in the areas (bays) between the wings leading edge and the first stringer is not putting the tissue on in the correct direction.

Meaning that the grain direction of the tissue should run the span (length) of the wing. From root to wing-tip. When this grain direction is reversed to chordways (grain direction running from leading edge to trailing edge) your tissue will not shrink in the correct direction, likely causing the tissue sag in the front areas; and probably the cause of a warp in the wing structure .

To determine the direction of the grain in your tissue make a small tear in it. If the tear is jagged and course, that is against the grain. If the direction of your tear is clean and straight, that is the direction of the grain in your tissue. That even, clean, tissue tear should run the span of the wing, and length of the fuselage too.

All the best for your future builds and welcome to the Guillow's forum.
Pauli72

[Country Modeler]

Thanks for the tip . I will definatly check the grain of the tissue first next time!