Radiator drag

[Kurfürst]

Originally Posted by Crumpp

If you line up the altitudes and look at the manifold pressures the French recorded, they used higher manifold pressure's when the closed radiator test was conducted.

That means the speed gap between open and closed due to radiator drag is not as wide as their results.

I don't think 10 Hgmm boost difference would change anything. In real life, that's well inside measurement/manufacturing/modelling tolerance.

From the practical standpoint its not too relevant either, since 1/4 open is the speed referenced point, the temperature is stable. Fully open position has only relevance as a speed break or on the ground for example, in prolonged run up.

In short, technically it might not reach up to modern engineering standards, but its more than good enough to model a flightsim with apprx. good values.

[Crumpp]

In real life, that's well inside measurement/manufacturing/modelling tolerance.

I agree it is not going to make much difference. I just noticed it and wanted to point that out.

Fully open position has only relevance as a speed break or on the ground for example, in prolonged run up.

Exactly.

I did not think the overheat modeling was realistic at all. In general these airplanes are designed to fly with radiators closed or in the least drag position (straak) and keep the engine cooled at maximum continuous and below.

It is only in overboost conditions, high density altitude, and stressful operations such as climbing that the engine temperature becomes an issue. I tried the Spitfire Mk I out and it ran at maximum temperatures in level flight in cruise settings.

[pstyle]

Hopefully the mythical patch update will give us some radiator drag modelling.

We red's have been running about with rads wide open for months now, with no effect on airspeed... I think, in the interests of historicity that this should be fixed...

[TomcatViP]

Originally Posted by pstyle

Hopefully the mythical patch update will give us some radiator drag modelling.

We red's have been running about with rads wide open for months now, with no effect on airspeed... I think, in the interests of historicity that this should be fixed...

That's the problem of some behaviour in IL2 sim world.

Personaly I never did that and used the rad as if they were not bugged (but I am so sure they induced drag that I am thinking you are one of those that are constently midling their prop with no top perf achieved).

Hence IMOHO, it's more a bug in the behaviour of some players that the only patch that will makes this debate vanish is your own grandma modeled back on your shoulder just like the days when she caught you the finger in the jam.

[pstyle]

Originally Posted by TomcatViP

but I am so sure they induced drag that I am thinking you are one of those that are constently midling their prop with no top perf achieved
.

ooooooh, handbags.....

[TomcatViP]

To get back to the graph posted by IvanK it show us that the drag effect of the rad flap in the free stream is negligible. Most of the drag come from the free stream of air impacting the actual radiator surface inside the duct (the duct being the encasing sheet metal).

Lowering the flap increase the exit area allowing a greater mass of air to circulate trough the radiator. Since the geometry of the rad system is fixed, in the inlet portion, the air is less decelerated and then impact the rad at a higher speed. This increasing the drag of the system (but adding more cooling effect obviously).

Concerning the FM of CoD, it could be interesting to use this same value for the Spit.