Engines with re-sizeable bases: Drag

[Foxster]

Some of the new engines can have their bases re-sized with the slider. For instance the Cheetah, where there is a  1.875m variant and a bare variant that seems to fit OK on the bottom of a mk1 tank. 

Initial testing though seems to indicate that the drag of the engine is the same if attached to a mk1 tank for both variants. 

So, is the engine really re-sizing to fit a mk1 tank or simply losing the larger baseplate whilst remaining a mismatched 1.875m engine drag-wise?

[Temeter]

I put skiffs on two 1.25m rockets; one bare and one with the 1.875 base. No difference in drag. Strange.

edit: If below a 1.875 fuel tank (cone expansion on the rocket), then the one without base has a bit less drag. Very small difference, but even more strange.

edit2: Similar results on a 1.875m rocket with the Kodiak enginese. Left is no shrouds, middle is small shroud, right is large shroud.

The engine with no shroud has the least drag; the one with the 1.25m shrough has a tiny bit more drag, and the one with the fitting, 1.875m shroud, has the most drag. (higher mach is likely because of lower altitude)

Seems bugged. The well fitting shroud should have the least amount of drag?

Edited March 14, 2018 by Temeter

[Foxster]

I've done a bit more digging and it does looks like the drag isn't working for the new engines as I'd expect it to. 

These engines come in variants that change the size of their bases. For instance, a Mastodon (listed as a size 1, 1.5 and 2 part in the advanced mode part list) can be neatly coupled to a size 1 tank. However, this doesn't mean it is size-matched for drag purposes. Only if an engine at its largest variant is coupled to a matching sized tank (2 for the Mastodon) do you get the drag reduction of matched parts.

This really is not obvious and can easily lead to a lot of drag. 

 

 

 

Edited March 14, 2018 by Foxster

[cfds]

Shouldn't you just use FAR when you are concerned about drag? That the stock "aerodynamics" work in wonky ways is long known.

[Foxster]

57 minutes ago, cfds said:

Shouldn't you just use FAR when you are concerned about drag? That the stock "aerodynamics" work in wonky ways is long known.

This is not about aerodynamics in general. It's about the new engines apparently being different sizes when in fact there are just cosmetic changes when altering the variant. 

[klgraham1013]

6 hours ago, cfds said:

Shouldn't you just use FAR when you are concerned about drag? That the stock "aerodynamics" work in wonky ways is long known.

We shouldn't have to rely on modders to solve Squad's problems.