Unrealistic TWRs when creating replicas.

[Shaun]

So I'm creating a new line of replicas, this time using FAR aerodynamics, Tweakscale and Procedural Wings, so the vast majority of parts are stock and still have a stock look... Because aircraft in KSP are so much heavier than their real counterparts, I just match the TWRs rather than thrust. This however causes problems as the aircraft are far too slow. I realise that even if I triple the TWR, the aircraft are still too slow. For example, the real Gloster E.28 has a TWR ratio of 0.21. In KSP my Gloster has a TWR of 0.65 but for some reason can't get above 95m/s (185kts) at 10,000ft (3050m), and at sea level I can only get a pesky 85m/s max, even though my wings sustain enough lift so that the angle of attack is 0.0* at this speed and altitude.

Is FAR still 'far' off from real physics? Or is the problem from something else? I only have 2 radial intakes btw.

[Taki117]

you're talking 212.5 mph at 3km. that's fairly standard for an aircraft of that sort.

[Sirrobert]

You people are intermixing THREE different systems of messurement

[Shaun]

I'm supposed to be able to reach more than double that with the E.28; 466mph @10,000FT/3050M

- - - Updated - - -

You people are intermixing THREE different systems of messurement

#British problems; adults use imperial; kids use metric and us stuck in the middle have to use both.

[cantab]

Keep in mind that FAR doesn't consider whether or not parts are clipped into each other. If you're building replicas and they're heavy on the clipping, you'll have a shape that looks sleek but FAR will consider it draggy.

[Shaun]

Keep in mind that FAR doesn't consider whether or not parts are clipped into each other. If you're building replicas and they're heavy on the clipping, you'll have a shape that looks sleek but FAR will consider it draggy.

My craft has a load of cubic struts but I thought they had no mass or drag in the game... Physics significance = 1?

[pincushionman]

How fast is this plane SUPPOSED to go?

[Shaun]

How fast is this plane SUPPOSED to go?

338mph at 10,000ft (3050m).

[NathanKell]

You're going to need to do the following to get accurate performance:

1. Use AJE to get real jet performance

2. Match wing area (main wing ONLY, disconnect the rest, then go to FAR->Stability->Calculate to get area) and then put it all back together and calc again to get Cd to try to match.

3. Match atmospheric density (3000m on Kerbin is *not* 3000m on Earth, it's more like 5000m).

Emphasis on Point 2, especially the latter half. Do *not* expect Cd0 to just magically match if you're clipping god knows what.

EDIT: Actually, even bigger emphasis on point 1. Without AJE, "jets" in KSP are just rockets that magically use air as fuel. They are not jets, and will not perform as such.

This is E.28-inspired, and with a detuned Welland performs about right in RSS (so altitudes do match).

Edited February 8, 2015 by NathanKell

[cantab]

FAR doesn't seem to respect the physicsless flag - I've found the OX-STATs have drag in FAR. Not much, but enough to make a rocket veer off course if it's got them down one side and not the other. I don't think they'd do much to your plane though.

[NathanKell]

No, FAR does not "respect" the physicsless flag. Nothing should, especially since the making of the 3.75m decoupler (all 3-odd tons of it) physicsless is the source of full crashes.

The real issue with FAR is open nodes, however: if you use cubic struts, make sure you put antennas on any open nodes.

[Shaun]

You're going to need to do the following to get accurate performance:

1. Use AJE to get real jet performance

2. Match wing area (main wing ONLY, disconnect the rest, then go to FAR->Stability->Calculate to get area) and then put it all back together and calc again to get Cd to try to match.

3. Match atmospheric density (3000m on Kerbin is *not* 3000m on Earth, it's more like 5000m).

Emphasis on Point 2, especially the latter half. Do *not* expect Cd0 to just magically match if you're clipping god knows what.

EDIT: Actually, even bigger emphasis on point 1. Without AJE, "jets" in KSP are just rockets that magically use air as fuel. They are not jets, and will not perform as such.

This is E.28-inspired, and with a detuned Welland performs about right in RSS (so altitudes do match).

That image... How did you get the fuselage like that? Is it a procedural mod?

Having one fuselage with a couple of parts would probably solve the drag issues I'll try out AJE too.

[Van Disaster]

That is a procedural tank, that and one of the procedural wing mods makes replica building end up considerably more replica-like.

Not that that is very close...

[NathanKell]

Shaun: yes, that's with Proc Parts. Three of them, as I recall, for the fuselage, plus two for the fore and aft cones attached to the canopy. Then proc wings for all wing surfaces.

[Shaun]

I've decided the best thing to do is learn how to use FAR and AJE to an extent where I can create models as efficently as possible with good flight statistics. I've hit lucky with my second attempt; I've made a small jet capable of sustaining level flight with 0 trim, and flaps tuned so the aircraft pulls up itself and lifts off the ground