Help with Procedural Fairings please

[Tyko]

I'm trying to use Procedural Fairings to create an interstage fairing, but I'm getting really high drag - even more drag than if I just threw a decoupler on and had no shroud or anything. With the F12 Aero tools enabled I can watch the drag on the top tank of each lower stage get really high when the rocket reaches around 8000m around 300m/s

Not sure what I'm doing wrong, but would really appreciate some advice on this.

I've uploaded two test rockets made entirely stock except for PF, one using procedural fairings and the other with just decouplers and huge gaps between the stages. The one with huge gaps actually has less drag

Thanks in advance for your help!

https://www.dropbox.com/sh/s961tiv02orgyu1/AAAGbF_RKTIEgg_7MFwI8gFJa?dl=0

(these were made in KSP 1.3.1, but I've been able to replicate the issue in 1.3 and 1.2.2)

Edited November 5, 2017 by Tyko

[Ratchet Hundreda]

The problem is that the way you use the interstage part the game does not take it as shielded basically meaning that for the game's aero calculations it's as if that fairing isn't there at all. 

KSP's stock aero calculations does not account for the shape of your craft but for each specific parts own aerodynamic properties. Meaning if you don't enclose the top node of that interstage the game thinks there is nothing inside that fairing and the engine is bare open to the air for which the game's aero calculations will account drag for appropriately. The part which causes the drag is the engine. That's why you don't have drag if you don't have the engine under that tank.

If you want shape based aero calculations, Ferram Aerospace Research is the mod for you.

 

Edited November 9, 2017 by Ratchet Hundreda

[Tyko]

@Ratchet Hundreda thanks for responding, I don't follow though. In the sample Craft A that includes interstage fairings they're snugged up against the next stage as close as I can.

You said the way I used the part isn't working. How is it supposed to be used so it works?

Edited November 9, 2017 by Tyko

[Ratchet Hundreda]

Like i mentioned snugging it up as close as you can isn't enough. The interstage part has 2 attachment nodes. One for decouplers and the payload attachement and one for the top of the interstage. The top node needs to be connected to something in order for the game to recognize parts connected to the bottom node as shielded. If you leave the top node open the game will think there is nothing inside the fairing. The interstage part originally is meant for ships which stack payloades on top of each other and to shield them properly they are not meant for engine covers since you can not use them for that not in the stock game at least.

The game thinks in nodes and in part metadata when putting together how a vessel should handle aerodynamically. The Ferram Aerospace Research mod changes aero calculation so that the shape of the whole vessel is what matters rather then them sum of each parts properties. In which case the areo calculation will account for you shielding the engine from drag in this manner.

[Tyko]

The top node isn't open though. Please note the sample craft I sent. I attached the top node of the Interstage to the bottom of the engine and then used the Procedural Fairings adjustments to lower the top node down and raise the fairing sides up to shield the engine part.

[Ratchet Hundreda]

You realize that means that the engine is out of that fairing in that case? Which means that it is not shielded since it is NOT attached to the bottom or "payload attachment" node of the fairing thus it is not considered shielded by Kerbal Space Program's aerodynamic calculations. You can not shield a mid-stage engine in that interstage fairing since it is not designed to be used that way. There is NO workaround in the stock game for shielding engines they way you want to with that part. However there is a way to make it and it is by using the mod i recommended.

Since i can not explain this mechanic more clearly than that if you happened to have further questions i would suggest asking the mod author @e-dog of the Procedural Fairings mod directly on its appropriate forum thread.

[Tyko]

15 hours ago, Ratchet Hundreda said:

You realize that means that the engine is out of that fairing in that case? Which means that it is not shielded since it is NOT attached to the bottom or "payload attachment" node of the fairing thus it is not considered shielded by Kerbal Space Program's aerodynamic calculations. You can not shield a mid-stage engine in that interstage fairing since it is not designed to be used that way. There is NO workaround in the stock game for shielding engines they way you want to with that part. However there is a way to make it and it is by using the mod i recommended.

Since i can not explain this mechanic more clearly than that if you happened to have further questions i would suggest asking the mod author @e-dog of the Procedural Fairings mod directly on its appropriate forum thread.

Thanks for your continued help! I appreciate you taking the time...

Do you have a sample craft that has a working interstage fairing? You say it's not designed to be used that way. If not, I'd love to see how it's designed to be used. Did you by chance take a look at the sample craft I uploaded?

Edited November 10, 2017 by Tyko