STK: Now you have the repair done, I'm wondering if there is something that can be done to remove the extreme point loading on that thin area where the front edge of the mirage drive slot, (the root cause of your failure). This is the highest point of stress on the entire boat. If you put a mask on, in your pool, (ok I had full scuba gear on, (lol)), and have someone pedal the boat above you, (with the boat either tied to something, or pointed into the side of the pool). When pedaling, you can easily see, (and feel) the hull flexing on every single pedal stroke, ( I strongly doubt anyone has ever tried this, lol everyone chases resultant failures, never root causes, (that's just human nature(). This is called a point load and I know of no un re-enforced plastic that can withstand that kind of load very long, (there is none). Dah we are scuba divers, so I use any excuse to dive, you can also just reach under the boat with your finger, and touch the spot while someone else is pedaling in the pool to test your fixes. If you look at the front and rear of the mirage drive itself, (where it rests in the pocket) it has a narrow hard surface and two sharp edges. There are a couple things that can be done, one being spread the point load over a larger area, the other being remove any load from that area altogether.
If you put your mirage drive into the slot and click it down, then rock it back and forth in the slot, with it rocked back measure the gap that is created in the front, (on most of our boats the gap ended up being around an eighth inch). If it's not enough gap, it's pretty easy remove the click and go clips, and shim up the bases a little bit to increase the gap. On one of our boats we had to make 1/16" thick shims under the click and go latches, (but that was one out of 8 boats, (actually one out of 12 mirage slots, because 4 of the boats were tandems). If you use plastic shims they don't rust, (however the shims under the click and go latches are a last resort, (don't do it if not needed)).
I have used many different designs depending on the mood at the time, and what I have handy laying around the garage. We've been using Hobies since 2007, and have owned many of them, plus we use the daylights out of the things, (lol because we can in south florida and the keys year round), plus I'm kinda retired and have pretty much nothin else to do, so I play hard.
1. A thick piece of hard rubber (1/8"-3/16" thick, if you have enough play under the click and go clip). We just cut the rubber about 1" wide and glued it into the bottom of the slot. It worked ok, the bad spot in the center flexed much less.
2. I made a sandwich with .040" thick stainless shim stock (1/2" wide) glued between two pieces of hard rubber, (leather would also likely work). That worked a little better.
3. I also tried bondo, basically you spray the inside of the hull (the mirage drive slot area) with silicone or urethane release spray. Then gob some bondo body putty onto the front of the mirage drive, (big ole wad), then click the drive in place and let the bondo setup. Once dry the front of the mirage drive tang is the same exact shape as the slot in the hull. Of course the bondo sticks to the nylon mirage drive tang, (you can always sand it down a little so it drops in a little easier, and also fits in either mirage slot on our boat just in case we get the drives mixed up). If you ever sell the boat it's easy to chip the bondo off the drive. This worked great, and when testing in the pool there was no flex in the bad area, (it actually worked, (who knew, lol). We also did a version with a bike inner tube glued to the outside of the bondo, that also worked.
4: On one boat we bought some 1" wide 1/16" thick aluminum, (3 ft long at Lowes). And custom bent up a big flat bottom V shape. Basically start out by bending a flat bottom V in the middle, with fairly gentle curves in the lower corners. When your done you want the aluminum to follow the side walls of the mirage opening, (touching the walls), of course make sure the mirage drive still fits in. Now bend the ends so they lay across the top of the deck flat, you want the flat part around 3" long. I then sunk a couple screws into each leg on top of the deck to hold the aluminum piece in place. I then gobbed in silicone across the bottom of the slot and put the screws in. It looks like crap, but hey it works, when peddling in the pool there was no flex at the front of the mirage drive opening. However it's a lot of work to build, If you ever sell the boat you just remove the screws, pull the thing out, and fill the holes with your handy dandy Hobie welder.
Nothing needs to be done at the back of the mirage slot, there is no stress back there.
In other words there are a dozen ways to fix the issue, use any you wish, or do nothing at all, (your choice). In my case we pedaled all of our Hobies many miles most every week year round, (pedaling my boats was my main exercise program). I promised the wife in order to buy the darn boat in the first place, I committed to pedaling the boat 10-15 miles per week (year round), I even had to show her my GPS records every week as part of the deal. Our TI had a 100 mile per day range, and we regularly did 50-60 mile day trips, I always try to peddle 100% of the time, (that was my exercise program). Obviously the boats were souped up just a little. Let me make this perfectly clear, there was nothing written in our deal, how fast the boat traveled, ( a giant loophole in the agreement that I exploited heavily). BTW 15 miles at 2 mph is 8 hrs on the water in 95 degree sun, first few times out I suffered heat exposure, (boy did I get screwed in that deal I thought at the time, lol), so I modified the boat a little. Lets just say the stock boat was not quite as capable as I thought it was going to be, a rude awakening, from delusions of grandeur in April 2010 standing on the showroom floor workin out the deal with the wife, so I fixed all that.
Also I always used the huge Flex-90 eclipse fins on my boats over the last few years, (way more strain on everything). I highly suggest not using such fins without re-enforcing the mirage slot, (and many other mods). Plus your going to go thru a lot of cables, and wear out the drives quickly.
Obviously if you only take your boat out 2-3 times a year, and only go a couple miles, no need to do anything at all, we used our boats way more and way harder than the average bear.
This was just one of 50 mods made to all of our boats, to set them up for our use.
Hope this helps FE
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