A few days ago, Nina pointed out that GoPro cameras are not that expensive anymore. Since I always was curious how much speed she kept in foiled jibes when winging, and GoPros that are newer than our ancient 3+ have a built-in GPS, we just had to order one.
After a couple of snafus with non-fitting accessories and rotated videos, I finally got some useable footage from the camera yesterday. Here's a short video:
I can't say that I am a great fan of the GoPro Hero 7 Black. It's much heavy and slightly larger than the old GoPro 3+, and gets less than half of the battery life, even at low resolution and with image stabilization turned off. The desktop software that GoPro provides to get the GPS speeds showing in the video is poor (if you ask me about it on the beach, you may hear less "friendly" words). But fortunately, there's very nice third-party software available that even runs on Macs: Race Render. Race Render makes is very easy to add different gauges and graphs to the video that show the data from the GoPro GPS. You could also use an external GPS, but that would require synchronizing, which could be a bit difficult.
Here's a screen shot:
The movie from the GoPro 7, which I had mounted on top of my helmet, is shown as a small inset at the bottom right. The main picture is from the old GoPro 3+, mounted at the end of the boom with a ClewView. Race Render makes it really easy to synchronize the videos.
On the top right is a heading indicator; the display is adjusted to that the top is dead downwind (we'll get back to that in a minute). Below is a speedometer, and below that a speed graph. The picture above is from the jibe entry, shortly after unhooking and starting to carve downwind. The next picture is a second or two later, after oversheeting a bit:
At this point, my speed has already dropped from 30 to 24 mph. The next picture is dead downwind:
I've started to open up the sail for the sail flip; speed is down to 18 mph.
In the picture above, I'm just letting go with my back hand. The picture below is in the middle of the sail flip:
By now, my speed is down to 15 mph - I've already lost half of my entry speed. The speed will drop a bit more before I grab the boom on the other side:
13 mph is the lowest speed in this jibe, according to the GoPro GPS. I was also wearing a Locosys GW-60 GPS watch, which reported a very similar minimum speed of 14 mph for this jibe.
I was doing sail-first jibe as a practice for foil jibes. The image above is just as I am switching my feet. I'm approaching the new beam reach and have power in the sail again, so I'm not loosing any more speed.
A few seconds later, hooked in again and getting into the front strap. My speed is already picking up again.
There are a few things that I could have done better in the jibe, but that's not what the post is about. I mostly wanted to share how useful the built-in GPS from the GoPro could be together with the video when working on improving jibes, and that Race Render is a pretty cool tool for this. There's a free version that has most of the functionality, as well as several paid versions that allow customizations and removing the Race Render logo that the free version puts in the movie.
