Once a polarizing topic, it seems we have finally stopped arguing about the effectiveness of vortex generators. Simply put, vortex generators work.
The current internet arguments seem to be about size, shape, placement on the leading edge, or a host of other important quips. We are not going to delve into any of those topics here, although there are hundreds of users on flying forums who are more than happy to argue with you about VGs if that is your thing.
The design and fabrication of a vortex generator (VG for short) can be quite simple. Many are injection molded beauties formed out of nylon with aluminum VGs often found hidden under the tail feathers of our beloved taildraggers. The question is this:
Can 3D printed components hold up to the standard operational stresses placed on vortex generators?
It seems the design constraints fall into one of the following categories:
Aerodynamic. Environmental, and Operational Design Stresses
- Aerodynamic stresses are obvious enough. The material needs to be strong enough to withstand the force of the air across the operational range of the aircraft, from spins to aerobatics.
- Environmental stresses can be slightly more complicated, but for this discussion we are referring to heat and UV exposure.
- Operational stresses are best described with the following question: Who here as ever broken a VG while fueling their aircraft? (Yes, I have too)
Can a 3D printed part meet the requirements of the above design stresses? I believe the answer is yes.
- The inflight aerodynamic stresses on a VG are relatively small. Since the VG is always angled to the relative wind the two important considerations are the mechanical connection of the VG base to the wing/tail surface and and fins ability to resist the bending moment. Proper use of fillets, clever use of the 3D printed layer grain, and a large enough base to adhere can overcome these stresses relatively easily.
- Ultraviolet light degrades most plastics and 3D printed parts have a lower heat tolerance range than injection molded parts. Specialized filaments can help overcome both of these issues, however an even simpler solution is the use of a light coat of paint.
- No matter how hard we try, we are still going to break them when fueling the airplane. The real problem then becomes availability, and this problem ends up making the strongest argument for 3D printed VGs.
Properly installed VGs on hangared airplanes will last indefinitely. Unfortunately, the same can not be said for aircraft part manufacturers meaning parts purchased today may not be available in ten years time when you break your next one off.
When purchasing your next set of VGs, what if you also were given a digital file which allowed you to 3D print identical additional VGs forever in the future?
That is exactly what we intend to do.
We are currently in a Colorado climate torture test with version 1.2 of the COLORADO CUB vortex generator. We are testing both PETG and ASA printed versions, each having minor benefits over the other.
Initial testing has shown the prototype design is plenty strong, can withstand the required temperature range, is expected to withstand the UV exposure, and can be printed in a variety of colors.
If you can't wait until we are done with testing, you may download the STEP files (with both round and flat bases) at:
http://www.OpenSourceAirplane.org
- Suggested filament is ABS, or ASA
- ASA is our favorite but...
- An unpainted PETG VG has been stuck to the outside of the shop door for ~3 months at time of writing in the direct sun. We are located at 9600MSL elevation with intense UV light year round. No degradation has been observed yet.
- ASA filament has superior UV resistance but is more difficult to print
- Print the VG vertically on the bed to orient the layers to prioritize fin strength
- We utilize 3M 468MP adhesive tape to secure the VGs with good results
If you do print and test this VG design, email dave@ColoradoCub.com and let me know your results.