3D Printing Printing Rocket Fins Open Rocket how ?

[Rustie0125]

Hey All

Been designing and testing 3D printed Fins as part of STEM project. and I have a couple of questions around simulating results here.

The fin gets printed on a 15 degree support to make sure that the layer lines is not in the same direction as airflow and the fin experiences more of a loading/compressing force.
Fin is roughly 110mmx50x6mm but has a elongated teardrop shape, you can see the 2D shape below in the orientation it will be on the airframe, The design is both structural and stability reasons which I will explain on if required but im wondering if someone has experience on how to capture and model these custom fins in open rocket.

The side profile 2D shape can be replicated and the width of the fin can be captured, but how would I go about capturing the effect the 3D shape of the fin as in On rocket ?
I know it has override field where the CD and CM can be captured so should I just do that and call it good enough ?

How much effect would the 3D shape of these fins have on the rocket vs keeping to flat 2D profile cutout like plywood.

 

[neil_w]

I would think setting the fin profile as “airfoil” would be as close as you’re gonna get in OR. It should give you a pretty good approximation.

 

[Rustie0125]

I would think setting the fin profile as “airfoil” would be as close as you’re gonna get in OR. It should give you a pretty good approximation.

Ya I tried Airfoil and it has some impact im just not sure what confidences I have eitherway

 

[JoePfeiffer]

OR's handling of airfoil shape is extremely crude. A fin will have a pressure drag on the leading edge, and a base drag on the trailing edge. The formulas calculate the pressure and base drag based on a square profile; multiply pressure and base drag by a factor I'd have to look up for rounded; multiply pressure by the factor and set base to 0 for airfoil.

 

[Rustie0125]

OR's handling of airfoil shape is extremely crude. A fin will have a pressure drag on the leading edge, and a base drag on the trailing edge. The formulas calculate the pressure and base drag based on a square profile; multiply pressure and base drag by a factor I'd have to look up for rounded; multiply pressure by the factor and set base to 0 for airfoil.

Thats my concern. the fins Im trying to play with does not only have a front and rear edge profile. I taper the fins from front to back to cause more pressure on the entire lenght of the fin. this will increase drag but should also increase stability because the fins are always under pressure. that the thinking anyway, and thats what led me to ask the question. The next step is if I want to use open rocket how would I relate those figures back to simulation. if manually computed is capture them under the override section as Drag