I've been using a custom jib with my AI for a while, and it's obvious that it boosts the performance under certain conditions, but I was curious how much of a boost I was getting. I finally figured out how to extract the telemetry data from my GoPro camera, so I made a (very long and very boring) video of sailing back to the Santa Cruz harbor yesterday, with a speedometer included on the video.

It takes a while to get going, but from about the 2:30 minute mark to about the 5 minute mark, I'm averaging about 6.75mph with both main and jib. Then I furl the jib, and the average goes down to about 4.75. That's a speed increase of more than 40%, which is more than I expected, and my guess is that, percentage-wise, that's pretty close to the max improvement that I can get.

In any case, under lots of different conditions, the jib does give a noticeable boost in performance. Of course, there is no free lunch--setup is a bit more involved, and there are more ropes to deal with.

I have a GoPro Hero 7 black, and it will record GPS and other telemetry data. My question is...

Is there an easy (and preferably free) way to edit videos (on a Mac) so that I can include speed and such on the resulting videos? The no-longer-supported desktop version of GoPro Quik supposedly will do this, but when I add any gauges to the video, the video itself disappears--just a black screen, except for the gauges. All of the normal video editing software that I can find (Camtasia and PowerDirector, for example), don't deal with telemetry data.

I had a spare 12" x 12" sheet of 0.080" kydex, and decided to try to make a Hobie turbo-like fin out of it. I heated the kydex with a heat gun, and formed it around the stainless mast. The rigidity of kydex is supposed to be similar to PVC of the same thickness, and kydex is very easy to form when heated and it's impact resistant (it's often used for holsters and sheaths, for example).

I was not expecting it to work well, as I've tried semi-rigid plastic before (as have other experimenters on YouTube), and it failed badly, in the sense of being much harder to pedal and yielding way less power, as compared to real Hobie fins. So, I was pleasantly surprised when my kydex fin worked very well. In fact, I could not tell the difference between this and standard Hobie fins.

I suspect that the key to success is the bungee cord that I used to connect the fin to the Mirage drive, as opposed to making a rigid connection. In the video, you can see the overall action of the kydex fin is very similar to the Hobie fin, due to the added flex provided by the bungee cord.

Not sure if this will be a long-term solution, but it I plan to do some more experimenting to find out...

https://youtube.com/shorts/1uiTd46DlFA

I've decided to try to make my own trampolines for my AI. I'll use different material than what Hobie uses, but the dimensions will be the same as the standard Hobie trampolines.

One slight problem.... I can't seem to find the precise dimensions of the Hobie trampolines listed anywhere online. So, if anybody who has them could measure and post the size here, I'd appreciate it (or better yet, if you are nearby, I could stop by and take some measurements). This will be for a pre-2015 AI, in case that matters...

I think I've probably watched all of this guy's videos by now. I never realized that filleting fish could be so interesting...

https://www.youtube.com/@reedthefishmonger/videos

I've been trying to put together a second AI from a Hobie Adventure (older version of Revo 16), and it's complete, except for the mast. The official Hobie mast is over $800, and I don't think it is even possible to get the pre-2015 version. So, I decided to try a windsurfer mast.

I found a used 460cm (15' 1") 90% carbon mast for $200 (no shipping, no tax), so I figured it's worth a try. The mast is exactly the same length as the Hobie mast, it's about 1mm narrower at the base, 2mm narrower at the top, the thickness at the center coupler is 1/16" (Hobie is 3/32"), and it weighs 3.86lbs (about 1/2 the weight of the Hobie). I did a few flex testing experiments, and as near as I can tell, the windsurfer and Hobie masts are virtually identical in that respect.

I bought the Hobie mast base and collar and attached them to the windsurfer mast (rivets for base, G-flex for the collar). The mast top piece seems to be currently unavailable, and since it fits inside the mast, it would not work without major modifications anyway. So, I made a little dohickey out of a solid piece of 1.5x1.5x3 inch piece of starboard plastic (not easy without a lathe...). That slips into the top of the mast. I've also got a mast topper that I use, which is the secret ingredient that makes it possible to fly a second sail (jib/genoa or spinnaker), and I figured out how to add that to the top. That was actually a bit tricky, as the sail is not a standard Hobie sail--it's from Intensity Sails, and was super-cheap (like $200, although, unfortunately, they don't sell AI/TI sails anymore). The non-Hobie sail has a narrower sleeve, so I could not slip 1.25" PVC pipe through it, and had to use some narrower (but, supposedly, extra-strong) below-sink PVC instead.

The only things remaining are to spray paint the mast-topper tube, and put one bolt thru to connect to the top of the sail, which should be done in a day or 2.

I might try to replace the mast-topping tube with aluminum tubing. I'd also like to redo that white starboard plastic piece in aluminum, but I don't have a metal lathe, and that would probably be beyond my limited angle-grinding skills.

The lighter weight aloft will be great, but a broken mast would certainly be no fun. A jib definitely puts some extra stress on the mast too.

I was hoping to test it out this weekend, but it looks like the wind will be practically zilch after Wednesday, so I might have to wait a bit to see if it'll hold up. In any case, I still need to find some battens, so if anybody knows where I can get 3/16" fiberglass rods in 10' lengths locally, LMK. I can find them online, but shipping is pricey.

A bunch of pictures...
 

My Hobie Adventure was making a creaking noise that seemed to be coming from the "click-n-go" thing (holds the pedals to the kayak). So, I wanted to remove the click-n-go things, but one bolt was stubborn and got stripped. I drilled off the head (luckily, no damage), but now I've got to get the bolt out.

Any suggestions?

I found YT video where a guy makes DIY fins for his mirage drive (it's a long and rambling video, but if you look at about 1:40, the set on the right is the one that seems to work reasonably well):



I might try something similar, as I need a couple of pairs of turbo fins, and the authentic Hobie version costs $70 each, while even the fake ones are $40 each.

But, I was thinking that it might be possible to create a mold from a turbo fin, and then make fins similar to the real deal using pourable liquid rubber. I'm wondering if anybody has any idea what kind of rubber the fins are made from, or any knowledge of a pourable version of rubber that might hold up to the abuse that the fins take...