How to Fill Seams and Sand Model Airplanes

When building model airplanes, it is important to remove the seams and the joint lines. For most assemblies, crack and gaps become common through fitting. The most common issues pertain to the mating lines and wing roots of both sides of the aircraft's fuselage.

Materials you'll need for this project include different grades of sandpaper, a paint brush, sharp hobby knife, a container with some water and a paintbrush. You can also add the Tenax-7R and model putty.

If you'll be utilizing hazardous materials as you build model airplanes, make sure there's plenty of ventilation throughout your working space. Check the labels and warnings on the containers of these chemicals.


The first step is to weld the right and left sides with the Tenax-7R. Using medium pressure, hold he two sides of the fuselage together. Then, touch the whole seam with the use of a paintbrush.

When you're done with the application, gradually add more pressure for the next ten seconds. Then, add another five minutes to let the weld dry up. Use the hobby knife to lightly scrape away excess chemicals.

If there are imperfections on your model airplane like pits, scratches or gaps, use a toothpick to apply some model putty. You can mask off openings or cracks with some tape. Afterwards, apply some putty and wait for 30 minutes until it dries.
When the putty has completely dries, use a 600 ALO sanding paper to sand the area to the tape's level. You can re-apply more putty if the gap didn't get filled or if the putty didn't dry up or contract to a groove in-between the parts. Just repeat the sanding process.

As soon as there's a level surface, take off the tape and start to fine sand your work. This is the most important step in building model airplanes.

Use 600 ALO paper to sand the aircraft model over sections where the Tenax-7R and putty were used. Then, use a paintbrush dipped in water to moisten the whole sanded area. Repeat this moistening process until it turns smooth. Before moving on to the next step, fry your model airplane using a paper towel or rag.

When you scale mode completely dries up, check it thoroughly. Check for some rough patches. If you find any, use 320 SIL paper or 400 ALO paper again. To complete this sanding task, you can use fine 150 SIL sanding paper in repeating the process. This will ensure a smooth and natural looking model airplane.
The last step is to paint your model aircraft.