Dr. Zooch Saturn 1 SA-5 Build Part 27 Details

Before cutting any of the dowel pieces, you might want to seal the wood. I used two coats of varnish, rubbed on with a paper towel. Lightly sand between coats.
The sealed dowel "ducts" will look much smoother when the paint is applied. I'd recommend sealing and sanding everything in one piece before cutting the ducts to length. It's easier to sand the dowels when the piece is longer.

In Step 10 you add all the dowels and trim pieces.

The upper LH2 Ducts glue against the body tube. I decided to sand down the side a bit so they would have a better gluing surface.

I wasn't going to sand these to a half round, but just take a little off one side for a flatter gluing area.

Dowels can be hard to sand, they'll want to roll.

To be sure the dowel would be sanded on one side only, I darkened the edge with a Sharpie. This thick line was drawn down one entire dowel.

When sanding, this line lets you know the dowel is still facing up. The line also works like a depth gauge, the more you sand off, the less of the line is left.

This is what the line looks like when a just little of the line is left, a thin line on either side of the sanded, flattened area.