Flying at elevation

[boatdziner]

I hope that everyone is getting good flights thus far and that the planes are trimming out well. My teams this year have designed and built their own planes (again) rather than using kits. We have a laser forge and use that to cut our own ribs and wing tips as needed and then go from there. The design that is doing the best is consistently getting flights around 2:00 minutes in our 23' gym. We are in Colorado and last your our top team won states so I know that they are competitive within our state. Recently we competed in the Boyceville invitational and our plane was 10th overall with two flights that both landed on the bleachers (about 8' above the floor) so definitely not our best times. I think the top time was about 1:50 if I remember correctly.

Anyway, I know that there are compensations for ceiling height as part of the calculations for virtual events, but I am curious what they are. Additionally, I am wondering if anyone knows how elevation will affect overall time? Our gym is located at almost 7000', about 2000' higher than either or regional or state competitions and certainly much higher than other locations around the country. I continue to hear that people are getting upwards of 3:00 minutes out of their division C planes and I am wondering if there is something that we are missing with our designs or is it possible that we are losing 30% of flight time due to our thinner air?

Thanks in advance for any help,
Dan Brabec

[coachchuckaahs]

I spent a number of years in ABQ with mid and high school teams (about 5600 feet). We did not see a huge improvement in times going to sea level contests, not as much as we thought we might see. We did find that we needed to change our rubber thickness somewhat (thicker if I recall) for the heavier density air, but it was a small change. I don't think your will see much difference going down just 2000 feet.

When we would go to Nationals we would rent a gym to get some test time in the local elevation.

Helicopters was a different story. There were substantial changes needed in rubber selection with heli. Times were generally down about 20-30 seconds in Ft Collins for those coming from sea level.

Coach Chuck

[boatdziner]

We definitely don't see much going down to Ft Collins or CO Springs other than that they have much higher ceilings at the venues. It is good to keep in mind using thicker rubber for those arenas. That may also help us reach the ceiling heights.

The plane that the kids built is somewhat unique in that it has the longest dimension as the wingspan. The plane length is such that it fits diagonally across the other two dimensions. It is a bit touchy on trimming and finding the correct location of the CM has required much trial and error. The kids want to build their own props, but I don't have much experience with that. I am encouraging them to experiment with the prop pitch on their Ikara props as a starting point. With the wider wingspan I suppose that larger prop diameters could be an option.

Thanks for the insights.
Dan

[coachchuckaahs]

If flying at a larger venue than your practice gym, utilize partial motor testing. We routinely use half motors for testing even in same size gym, in order to reduce risk of getting a plane in the rafters, and to shorten test flights to make better use of the gym time. Half motor (0.75g) with a spacer (0.75g) that is 1/2 the hook to hook distance, will have half the winds, half the altitude change, and half the time.

https://www.indoorspecialties.com/artic ... Motors.pdf

Coach Chuck