Archive for the ‘ fuselage ’ Category

Fuselage shape optimization

I decided to do svn up for QFLR5 and was delighted that it has progressed further. I decided to try out fuselage shapes this time because it turned out that QFLR5 now allows larger airfoil thicknesses than 20%. Therefore here is a 26% fuselage shape I created today.

Here is how I started it:
1. I took NLF414F airfoil which I know to have very low drag value at 10 million reynolds number.
2. I decambered to it to zero camber
3. I changed thickness to 26%
4. I changed leading edge radius: 30% from leading edge, 0.8 ratio.

The simulation result gives very low Cd-value. The problem in reality is that because of all intersections, and a hatch where one has to enter the craft, the transition point is not that great as predicted by the program most likely.

Here is another simulation, transition forced at 40% chord. The Reynolds number is the same, 41 million with mach 0.29:

I further adjusted the leading edge radius, from the above, I reduced it to 0.8 again.

Here is the result KSNLFFUSELAGE3:

The simulated polar for the NLFFUSELAGE3:

Obviously the fuselage is supposed to be flown at zero angle of attack on cruise flight, but for slight side slip situations it is good to know how the drag rises on the fuselage. It also affects to the stability negatively (for example because the lift slope is not at all linear).

Potential improvement idea for use in non-steady flight: widen the low drag bucket a bit.

The airfoil shape as a axisymmetric fuselage (or as a generic pod, this works also as a engine pod), 3D illustration:

And this is how it looks from inside:

Structurally the pod requires thicker boom than the optimum and unfortunately the drag will be larger than the simulated one for the pod alone.

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Fuselage shape optimization

I decided to do svn up for QFLR5 and was delighted that it has progressed further. I decided to try out fuselage shapes this time because it turned out that QFLR5 now allows larger airfoil thicknesses than 20%. Therefore here is a 26% fuselage shape I created today.

Here is how I started it:
1. I took NLF414F airfoil which I know to have very low drag value at 10 million reynolds number.
2. I decambered to it to zero camber
3. I changed thickness to 26%
4. I changed leading edge radius: 30% from leading edge, 0.8 ratio.

The simulation result gives very low Cd-value. The problem in reality is that because of all intersections, and a hatch where one has to enter the craft, the transition point is not that great as predicted by the program most likely.

Here is another simulation, transition forced at 40% chord. The Reynolds number is the same, 41 million with mach 0.29:

I further adjusted the leading edge radius, from the above, I reduced it to 0.8 again.

Here is the result KSNLFFUSELAGE3:

The simulated polar for the NLFFUSELAGE3:

Obviously the fuselage is supposed to be flown at zero angle of attack on cruise flight, but for slight side slip situations it is good to know how the drag rises on the fuselage. It also affects to the stability negatively (for example because the lift slope is not at all linear).

Potential improvement idea for use in non-steady flight: widen the low drag bucket a bit.

The airfoil shape as a axisymmetric fuselage (or as a generic pod, this works also as a engine pod), 3D illustration:

And this is how it looks from inside:

Structurally the pod requires thicker boom than the optimum and unfortunately the drag will be larger than the simulated one for the pod alone.