Do displaced fuel tanks produce drag?

[Pie Guy]

I'm designing an SSTO and I filled some rocket tanks with oxidizer and clipped them into the main (mk2) fuselage. They are completely hidden from the outside world. Do they still produce drag as if they were exposed to the atmosphere? How do I prevent that if it's the case?

[miklkit]

Go to youtube and look up a guy called VAOS.  He did a series about SSTOs and drag.

[Lt_Duckweed]

They will still produce drag.

To prevent or reduce the amount of drag they produce you have two main options:
1. Put them in a cargo bay or fairing.
2. Use node attachment on any open nodes to reduce their exposed surface area, as detailed in this video: 

 

[Nazalassa]

On 11/10/2022 at 12:15 AM, Pie Guy said:

Do they still produce drag as if they were exposed to the atmosphere?

Yes, unless their "center" (the origin of the arrows with the 'move' tool) is within a cargo bay, a closed fairing (not a flying bowl), or an engine plate that has something of the same cross-section attached to its bottom node (it has a shroud).

Or, for some reason, parts that are attached to the top node of the same engine plate I was talking about one line ago are also shielded from drag.