Mass reduction for removing tanks from parts?

[Galane]

I want to make versions of some parts minus the oxidizer tank, minus both oxidizer and fuel tanks, and minus oxidizer with fuel volume expanded to take up the oxidizer space. Easy to do, just add a folder under GameData and put renamed copies of the edited cfg files in it, and the part names in the cfg files also have to be changed. The tricky bits are the numerical values to change.

For example the MK2 Bi-Coupler and MK2 to 1.25M adapters. Without the tanks, but with fuel crossfeed left in, the part should weigh quite a bit less as a structural only component than just emptying the tanks in SPH. There's a lot of parts in KSP that could be much more useful (mostly due to weighing less) if they were available in such variations. With expanded fuel tankage I'd expect the dry weight to be the same or perhaps slightly less due to not needing bulkheads for two tanks. Wet weight would be the same since fuel and oxidizer are the same per unit.

Should be able to cut the weight of my plane to under 10 tons by taking a cutting torch to those MK2 parts. It only need the liquid fuel in two MK2 to 1.25M adapters.

[Kurld]

IRL the weight of the tankage is negligible compared to the weight of the fuel inside. Some tankage actually needs pressurized fuel inside to maintain structural rigidity. You might factor in a small reduction in dry mass, but it won't/shouldn't be much IMO.

[Aerospacer]

@Galane , is a simple example from stock game - FL-T400 (LFO) and Mk1 LFF (LF) - its size, volume, capacity, dry mass are equal = 0.25 t. And are have its analogue - Structural Fuselage , construction without any fuel m=0.1 t (40% of fuel tanks mass).

But your parts for plane also have a lifting coeff., and its partially mass shouldn't reduction. I suppose, for pure structural Mk2 to 1.25m Adapter correct mass is 0.14 t, for structural Mk2 to 1.25m Adapter Long - 0.27 t.

Look a kerbal-wiki for comparing.

Edited September 9, 2017 by Aerospacer
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[Galane]

1 hour ago, Aerospacer said:

@Galane , is a simple example from stock game - FL-T400 (LFO) and Mk1 LFF (LF) - its size, volume, capacity, dry mass are equal = 0.25 t. And are have its analogue - Structural Fuselage , construction without any fuel m=0.1 t (40% of fuel tanks mass).

But your parts for plane also have a lifting coeff., and its partially mass shouldn't reduction. I suppose, for pure structural Mk2 to 1.25m Adapter correct mass is 0.14 t, for structural Mk2 to 1.25m Adapter Long - 0.27 t.

Look a kerbal-wiki for comparing.

Costs should also be less.