The Caltex Lumba makes progress
Looks great, but you need a bigger (bathtub) porcelain test tank.
Those windows are tough especially in balsa wood, it always tears and shreds. I recall the Lumba Lumba has a fairly thick hull which makes the windows look funny anyhow. I would give serious consideration to just painting them on.
Another possibility is to make a separate strip with the windows neatly cut into it and then cut out a hull section and install the strip windows and all. You can make duplicates for both sides by using double face tape to secure two pieces of wood together. Then you can use thin plywood which would give better looking windows.
Those windows are tough especially in balsa wood, it always tears and shreds. I recall the Lumba Lumba has a fairly thick hull which makes the windows look funny anyhow. I would give serious consideration to just painting them on.
Another possibility is to make a separate strip with the windows neatly cut into it and then cut out a hull section and install the strip windows and all. You can make duplicates for both sides by using double face tape to secure two pieces of wood together. Then you can use thin plywood which would give better looking windows.
The sure way to succeed is, just try one more time