One battery cost me nearly 300mps top speed

[Klapaucius]

This plane maxed out at 600 mps (it exploded not long after) but the point is, it is fast for a Goliath powered aircraft. I added one Z200 battery between the cockpit and the nose cone, and slid the cone back to hide it.  That one change cost me 300 mps in max speed.  That's just weird.  Oddly, the antenna on the back has not had any noticeable effect.

 

Any thoughts?

https://kerbalx.com/Klapaucius/Gertrude

[linuxgurugamer]

The antenna probably diesnt have any drag.

The battery, on the other hand, does

[Xd the great]

Well, that is the stock aero system. Stuff does not cover up each other. Basically cargo bays and fairings are, well, less useful.

Far might help, if you are willing to install mods.

[overkill13]

The Z-200 battery is a 0.625m part.  The body of your craft and nose cone are 1.25m parts.  In addition to the fact that clipping things over or under other parts does not significantly reduce drag (often increasing it, actually), the non matching node sizes are well documented as an absolutely unforgiving producer of drag at supersonic speeds. 

Place a Z-1k battery (1.25m) inline.  Despite the increased mass, the two matching nodes will do wonders.  You might even see decent results from one or two Z-100s attached radially if you just get rid of the mismatched nodes.  Otherwise change the nose or tail to a FL-A10 structural piece, a Z-200 battery and a small nose cone, though, from the looks of things, it's probably too short or ugly for the design.  Clip the batteries into the structural pieces if you find them ugly, but at least match up the attachment nodes for best results.

[Klapaucius]

Thanks @overkill13. That explains a lot.  It makes perfect sense actually that mismatched nodes will create drag--that's a big eddy for air to get trapped in.  I've got to remember, as both you and @Xd the great said, that clipping and hiding parts behind fairings does not work as it does in the real world. 

Ironically, I originally had the larger battery inline, but I wanted to clip the battery just for looks, and the smaller worked better for that. No matter, there is a enough power generated by the engine just above idle to recharge the internal power enough for the antenna to work.

Edited July 14, 2018 by Klapaucius

[blakemw]

Hiding stuff inside fairings and cargo holds DOES work, though when things are attached to the walls the game might convince itself that the thing is really not inside the cargo hold. But if anything is offset deeply into the cargo hold it'll definitely be removed from the airstream.

To clear up any confusion here is how it works:

Node attachment: What a thing is attached to and relative node sizes matters*, offsetting and clipping doesn't matter in the slightest.

Cargo holds/fairings: The things physical location relative to the cargo hold/fairing matters, the part it is attached to does not matter in the slightest. (yaaaay!)

 

* There is a limited exception when dealing with truncated cone parts, for whatever reason you can stack parts like mk1 command pods on top of each other or place a part matching the bottom node on the top node (i.e. putting a 1.25m fuel tank on top of a mk1 command pod) and the game considers this to be properly streamlined.

Edited July 16, 2018 by blakemw

[Foxster]

On 7/16/2018 at 3:28 PM, blakemw said:

* There is a limited exception when dealing with truncated cone parts, for whatever reason you can stack parts like mk1 command pods on top of each other or place a part matching the bottom node on the top node (i.e. putting a 1.25m fuel tank on top of a mk1 command pod) and the game considers this to be properly streamlined.

Good info here. There's a similar story with some of the new engines. 

You need to look at the mesh shape/size to know what parts will fit together for low-drag purposes. It is often unclear in the stock game but there are mods to display the mesh outline of parts. 

[XtraChrisP]

Clipping things into each other is purely cosmetic.  They aero physics calculations will apply drag to all parts as if they were fully exposed to the air.  And like others have stated, abrupt size mismatches will absolutely kill you.  Use adapters, fairings, and cargo bays to keep your draggy bits out of the airflow.