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master of some
Those are Franz's collets, very nice stuff. I'm running those on my Exocet.
Vac-U-Tug Jr (13mph)
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Yep, those are them!
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Got a couple more runs on the boat with the new collets. Had a real nice long run last Sunday, and I was feeling really good about things... Ran real well, and very very fast. Almost ten minutes of running time, and everything running just lightly warm...Fast forward to yesterday. I ran the boat again. and was running fine for about five minutes. until I had another flex shaft bond failure. This is now the second MHZ Flex cable that their glue bond of the flex to hard shaft failed. Lost yet another prop. Quite disappointed and not happy with MHZ at all. Rewind about two weeks ago. I contacted MHZ regarding concerns about the glue bonds between the stuffing tube supports and the hull. The bonds have a lot of movement in them, and feel like the bond is separating from the hull. MHZ requested to see the issue, and I sent them a video. They replied that the glue they used must have been open for too long and didn't cure right. They offered to give me a voucher and some "free" glue to fix it, though they sent a message a day after saying they just realized they can't send glue to the US. Chatted to some people on a MHZ/HPR owners group on Facebook and posted the video there for them to see. Got various replies, from "this is normal as it's supposed to be a flexible joint" to "more proof of bad quality control; tear it all out and re-glue everything." Don't know what to do at this point. Back to the flex cable issue, I contacted MHZ again and awaiting what their response will be this time. Probably more of the same I'm sure. One thing for sure, I'm not going to keep spending $100.00 on new shafts from them (plus replacing props) if these things keep failing after a few runs....Nor am I going to buy another boat from them ever again, as they failed to deliver all the way back to when I first received the boat. Anyone have any input feedback, please feel free to share.
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What's the steps you went thru to glue the flex to drive shaft?
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They were glued by MHZ. Already Screenshot_20220925-155513_Chrome.jpgassembled flex shaft assembles
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It's more of a do-it-yourself hobby. Now you know the gluing job is not 100% so all shafts need to be redone. Burn off the glue and separate the flex shafts. Grind the flex ends, use a drill bit to clean the shaft holes. Burn off and clean everything. I use Loctite 648 retaining compound. Google how to burn off retaining compound.
You should get good at surface prep and gluing. You won't bat an eye pretty soon and won't loose any parts either. Good luck!
Fast Electric Addict!
Try Mcorp for some shafts....
Unfortunate the decline in MHZ quality. It's not supposed to be a flexible joint if everything is correctly lined up. just bad quality again.
- I can sell you a nice Hpr C5009 if you can get your money back from MHZ, it's a bare hull currently. haven't marketed it yet but it's a genuine HPR hull that's been over 120mph (200km/h+) at the munich SAW event.
Hpr 06 / 09 / 150 /185, Mhz Skater H45 hydro.
Uk SAW record holder
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Nice how big is that hpr?
Fast Electric Addict!
Same as the MHZ, 115cm approx.
Hpr 06 / 09 / 150 /185, Mhz Skater H45 hydro.
Uk SAW record holder
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Above is the YouTube link to the video of the stuffing tube movement I mentioned in my previous post today.
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Yea that's coming undone from the hull. Poor surface prep likely. Gotta remove it and start over.
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Well, as much as I didn't want to (and dreaded having to do), I took apart my boat to properly redo MHZ's shoddy workmanship. I removed the stuffing tubes, and supports. Needless to say though, it took no effort to pop loose the supports. Just as suspected, there was absolutely no prep to the hull when it was assembled at MHZ, so nothing adhered properly. Surprised the whole thing didn't catastrophically fail while I was running the boat all this time. In the process of pulling out the port stuffing tube, the tube split open on me, but I happened to have a brand new pair of replacement stuffing tubes that MHZ sent me in error when I last reordered new flex cables. So I re-bent a new stuffing tube. Will install a new one on the starboard side as well. I also popped out the water pickups, and will properly glue in new ones. I'm thinking of omitting using the oiler/bearings on this redone setup. Probably not necessary, as I don't use them. What you guys think? Any practical need to have the bearing on the tube?
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I use the grease fittings to keep water out of the hull. I put grease in a syringe with a silicone hose on the end, while slowly spinning each motor with the remote I inject the grease. That flex cable will pull it down and create a nice sealed cap at the bottom where it connects to the drive shaft. Works every time and it's super easy, if I don't do it water will come in thru the stuffing tubes.
master of some
I don't use the oiler/bearings. For the most part, if my drives are properly sealed up at the transom mating surface on the exterior of the hull, I don't have water issues inside. If the driveline is properly aligned, the bearing is unnecessary anyways.
You're going to learn a lot from this retrofit, and will be better prepared to diagnose and correct issues in the future. I learned a lot by fixing other people's shoddy work. It helps to start with a blueprint and correct details along the way. Much easier than starting with a blank canvas of an un-drilled hull
Vac-U-Tug Jr (13mph)
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I'm thinking that I may just go that route, and not use the grease bearing. I'll instead have the extra length of the new longer tubes to give me less of a gap between the coupler and the end of the stuffing tube, but still have enough room to use the flex savers.Originally Posted by fweasel
I agree that I will learn a lot doing this, as frustrated as I am about having to redo it all. For sure much easier than starting with a completely bare hull and having to do all the drilling and such, especially since I never done a completely bare bones build.
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MHZ got back to me this morning after I answered some questions they had regarding my setup. They are assuming that the problem with the cables ungluing was caused by too much pitch props, and said they only use a pitch of 1.4. I'm currently running 48mm x 2.65 pitch, which surely is a lot more pitch than what they use. Started with 3 bladed and switched to 2 blades, which seemed to run much smoother than the 3 blade. They advised to make sure my setup didn't start cavitation, which isn't good for ESCs. The boat seemed to run great on these props. It planed out really quickly, and I didn't really notice any excessive cavitation. There was only some notable heat in the motors themselves; ESCs, connectors/wires, and batteries were all just lightly warm. Once everything is back together though, I am going to re-program the ESCs for a softer acceleration, as right now when I slowly apply throttle, the boat starts off slow, and if I'm not too careful as I increase the throttle, the boat will suddenly launch out of water like a rocket. Kind of scary!
Back to the props, MHZ said if I want to proceed with using my current props, the only solution would be to have specially modified prop shafts with a deeper milling for more attachment inside of the flex and prop shaft, which they said they would do the modification if I choose.
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I don't know about that bro that sounds like tall tales. Feel free to post a picture of your flex cable that came undone.
I got 1/4" of their drives and they put down 8kw each. I don't see those coming undone anytime soon.
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They might be giving me B S. I don't know. Worse comes to worse, I'll have to source somewhere else (preferably in the states) who could make one piece cables suitable for my setup. Pic of my flex that came undone below...
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If the left side is the drive one, the cable wasn't cleaned enough to remove the coating so the retaining compound could adhere. There should be no black left just shiny metal. Also, the shaft needs to be cleaned inside and scored with a drill bit for good adhesion.
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Yes, the left side is the end that went into the stub shaft.
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Its been awhile since I last posted something here, so here's an update on where I'm currently at regarding the rework of my Mystic's stuffing tube assemblies. I received new stuffing tube supports and water pickups along with new flex cables from MHZ back at the end of September. Then this project (as well as everything else) got shelved because my family and myself all came down with COVID, and were out of commission for almost three weeks. All doing much better now though! Just started fidgeting with the boat again the other night, and I trial re-installed everything back into the hull with the new parts. The MHZ stuffing tube supports are kind of a pain to work with, but looks like I have things looking pretty close to where they need to be. I yet have to rough up all the gluing surfaces in the hull, so all parts adhere properly this time when I glue everything back in place. Was going to use JB Weld epoxy; if anyone knows of or recommends something better, please feel free to advise! I used JB to re-glue a stuffing tube support that unglued on my 56" Genesis, and it ain't going anywhere now! I have pics below of how everything looks. If anything is of concern or doesn't appear right, please inform me. I hope to get everything glued back in shortly, so I can get the boat put back together. Hopefully this rework will make for a more reliable and solid setup.
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master of some
Its hard to say, I don't see a lot of epoxy around the water pick-ups or the stuffing tube mount. Pick-ups aren't structural, I get it, but I would mask off a rectangle around them and cover the entire thing to get a strong bond. Same with the stuffing tube mount. There's not a lot of surface area where it attaches to the hull, so you need to build up a perimeter of epoxy around it to create some additional stability and surface area for adhesion.
It looks like you might have added some JB Weld to the motor mounts, specifically the bottom edge, facing the rear of the hull. I would have made the joint slightly wider, again, more surface area. When I glue in motor mounts, after I tack them in place with a little CA, I lay down the epoxy in several steps, positioning the hull in a different orientation each time, to let gravity do its thing. Bottom, both sides on one face, then again on the rear face. When there are no rear motor mounts in place (impossibly on an outrunner motor), the bulkhead mount can never be strong enough.
Vac-U-Tug Jr (13mph)
Member
I didn't glue anything in yet. I only set everything in place in the hull to see how it all ines up, and get the stuffing supports in the right position for correct alignment. I will mask everything around the area to make it neat, and will cover the whole area and across the pickups with epoxy when I do glue everything in.
As for the motor bulkheads, they were glued in at MHZ when I got the boat, and "so far" appear to be solid. But of course that's what I thought about their gluing of the stuffing tubes and supports...
master of some
Ah, ok, that explains why it was so difficult to see epoxy laid down.Make sure to sand and clean all mating surfaces.
If that were my hull and some of the epoxied parts already let loose, I would grind out as much of the existing motor mount epoxy with a dremel, prep the surfaces, and re-epoxy it. The hard part is done for you, knowing where to position the motor mounts. If you prep and re-epoxy one face of each mount at a time, it should be a pretty simple job.
FYI, JB Weld can be dyed with black epoxy dye to improve the finished aesthetic appearance.
Vac-U-Tug Jr (13mph)
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