Rounded fuel tanks not providing fuel?

[SignalCorps]

I installed the Kerbal stock part expansion mod (http://forum.kerbalspaceprogram.com/threads/107047-1-0-x-KSPX-Kerbal-Stock-Part-eXpansion-mod-reposted-v0-2-9-11-05-15) which gives you rounded, side mount fuel tanks, much like the monopro tanks) of either fuel or lox. I attached several of both to a large tank to give it some extra fuel, but at no time did any fuel get used from these tanks. I could do a resource transfer, but doing so with 30 little tanks while lifting off is problematic. (and attaching hoses to each tank really defeats the purpose of those tiny little things). Monopro radial mounted tanks work fine...should the radial mount mini tanks also be working? Or is it a glitch, just not programed right in the mod, or am I doing something wrong?

Edited June 26, 2015 by SignalCorps

[Mastikator]

LFO Fuel tanks tend to not give radially inward unless you put a fuel duct.

Basically you need fuel ducts.

[Streetwind]

There's no fuel crossfeed between surface attached parts at all, anywhere in KSP. Such a thing has never existed and is unlikely to exist in the future.

Seems counterintuitive, I know, since monoprop tanks obviously work But yes, even for monoprop tanks, there is no fuel crossfeed. The reason why it works is that the monoprop fuel itself is treated as a vessel-global resource. It is configured to flat-out ignore all fuel flow rules.

It's a good thing too that there's no fuel crossfeed for surface attachment. Without knowing it, you rely on that feature every day when designing rockets. Because of it, you can actually do things like building rockets with side-mounted liquid fuel stages. Radial decouplers don't block fuel crossfeed - if whatever tank attached to them was able to crossfeed with the central stack, imagine the chaos! Your outer engines would draw fuel from the central stack that you meant to reserve for your next stage. A lot of designs like this (and others) would suddenly not work correctly anymore.

Edited June 22, 2015 by Streetwind

[Sharpy]

LFO Fuel tanks tend to not give radially inward unless you put a fuel duct.

or unless they are placed on radial decouplers. That was a surprise to quite a few. (like that guy with some probes attached to decouplers, that were drained of fuel upon reaching the orbit)

[Xannari Ferrows]

You only need a single fuel duct at the end of the stack as well.

[Red Iron Crown]

There's no fuel crossfeed between surface attached parts at all, anywhere in KSP. Such a thing has never existed and is unlikely to exist in the future.

That's not 100% correct. Radial decouplers have crossfeed enabled, but it only seems to work when a non-fuel tank part is attached to them. There's also the new fuel feed rules for basic jets, turbojets, and Rapiers, which will happily drain radially attached parts of LF (and O in the case of the Rapier when in rocket mode).

[NathanKell]

The problem is not "no surface-attach crossfeed." If that were the case, 24-77s and Mk55s wouldn't work.

The problem is that surface-attach crossfeed only flows out, not in. A surface-attached part can draw from what it's attached, to, but no part can provide fuel to what it's surface-attached to.

Hence http://forum.kerbalspaceprogram.com/threads/76499-0-24-2-CrossFeedEnabler