MHz mystic help

[keithbradley]

The drives are at 10° negative because the jack pads are too tall you cannot take it out. They have already been machined down to the maximum and they still have negative. It already had 1/8" machined off them because they were at a 30° negative with them the way they come. I mean pointed at the ground negative. The drives themselves needed to be lower and more inside on the transoms but even still there is no way the setup as supplied would ever be able to adjust out the negative they have in them. There are many threads with people having this same issue.

The drives that are made for the boat have a issue. You can not collapse the jack pads to get the negative out. It is a common issue that they have. It isn't anything new it is a problem most have until you find a way to fix it. New custom pads that are inside the hull and are flush so the drives can be raised flat or something.

The motors and mounts are all made custom from MHZ for the boat and you can't really move to motors back any further than they are. At this point it needs custom made pads machined to get the negative out but then it is surely going to need the batteries moved way forward or it will be upside down the first time the motors hit. Until the negative can be adjusted out it will likely not handle at low speed and be susceptible to spin out while corning at speed.

I'm lost...is this your boat or the OP's? I absolutely, positively know how to make these boats run well, with or without MHZ drives, despite your experience. I'm not sure what the point of your post is. Did you build the boat for the OP or something?

[rauldino132]

He had built the boat for me it's my boat Here are some pics. Hope this helps boat runs great and the Straits very fast just seem to spin out in the turns and it's hard to get back up and going

[rauldino132]

Couple more pictures

[ls1fst98]

It would appear to me, at least from my little experience with drives like this (only built one with similar drive) that you did not mount the drive low enough on the transom.

[danielplace1962]

I'm lost...is this your boat or the OP's? I absolutely, positively know how to make these boats run well, with or without MHZ drives, despite your experience. I'm not sure what the point of your post is. Did you build the boat for the OP or something?

The point of Raul's post is not much without mentioning what we already know what the problem is. No one can help if he doesn't even mention it.

The point of my post are that I know exactly what is wrong with the boat. Raul makes this post and doesn't even mention the issue we know we have.

The negative pushes the transom up and to the side when you try to drive away at low speed. What else would you expect with so much negative. It is going to be the same at speed also. Too much negative the transom is light and it will spin out.

What does my experience or your experience have to do with trying to get a boat to run properly when it has a ton of negative in the drives ? No one will have a way to cure that without fixing the drives first ?

Not my first boat build ya know. Been building all kinds of fast r/c boats since I was 10 years old. I am 52 now so 42 years of personal experience.


The point of my posts is to save everyone from wasting their time on suggestions that mean nothing when no ones knows the real issue because Raul's made the post and never mentions the issue we already know the boat has.



Raul mounted the drives. He mounted the drives on the transom and put them as far inside and as low as he thought he could. The area around the bolt heads are already hollowed out to get them to go in because the bevel of carbon in the corners around the transom on the inside are 1/4" thick and he didn't realize that wouldn't be low enough or inside enough.

You would think it would have had room inside so the drives could be mounted where they need to go. Or at a minimum tell you to be sure they are mounted low enough and inside enough so you don't end up with a useless build but rather tell you that you will be needing to having to hack the inside up to get them where they need to go. As the hull is now they are mounted about as low as and as far inside as you can. The inside has to be ground out and almost cut the transom free from the boat to get them to be low enough to adjust flat with the height the pads are. Even if you got them flush it would at most only be 1/8" lower and we already removed 1/8" from the pads. So they would still have ended up with negative in them.

The boat was nearly done when I put the drives back on and saw the fiasco. Rather than rip the drivelines, drives, stuffing tubes and mounts out and fiberglass up the huge holes everywhere and start over we decided to try and run the boat. Considering how much negative they have in them it actually did better than I expected it too.

Keith,
Raul just called and said you were the one with the same issue on one you built. He had already sent me the link to the thread and the fix you did to the stand that goes in the pad. That just looked too weak to consider doing. When we get it fixed we are going to do something so the integrity of the mounting isn't downgraded. Having one of the drives come loose at the back is not something we want to have happen that is for sure.

[danielplace1962]

It would appear to me, at least from my little experience with drives like this (only built one with similar drive) that you did not mount the drive low enough on the transom.

Exactly. We know that is the problem.

His picture isn't really showing how much is really there. It looks almost flat in the picture but it is far from flat.

Not sure what good posting here was when he already knows what is wrong and never mentions it at all. I have setup and run enough cats to know they aren't going to drive with that kind of negative in the drives. It pushes the transom up and swings the boat to the side every time it is settled in the water and you try to drive away.


Raul did just enough of the build that the drives got put in the wrong place. Had they been correct the shaving of 1/8" off the pads could have got them to go flat. As it is we need to make new mount pads inside the hull somehow or redo the entire build.

It wasn't really his fault he didn't know. You would think a $900 bare hull with the drives that they make for the hull would have a instruction sheet so you don't ruin the entire build before you even get started. Even if you ground out the inside to put it lower and more inside you aren't going to get what it takes to get the drive flat. As he put them in the bolt heads were solidly on the bottom and inside because there is so much material beveled into all the corners.


Raul realizes that now but even if you could get it with the metal all the way flush with the bottom and the inside of the tunnel which you can't really even do because the screws and bolt heads prevent that from being a reality so the most it would lower the drive on the transom is 1/8" and we already took that 1/8" off the pads and there is still negative a lot of it.
Had they been the 1/8" lower and cutting the pads down would have made it barely doable for them to go flat.


Same thing on the little mystic. Built one of those and if you mount the drive as low as you could and as far inside and you could go the drive can not be adjusted flat.

[Apophis]

I have two of these hulls here right now, no problems placing the drives in the proper location. As for the smaller 840, same, I can get positive or negative in the drives no problem. I can see rookie build mistake but there are no problems with these hulls or hardware together.

Is that the water pickup tube sticking out the bottom of the hull or has it been trimmed off? I would guess that would cause some issues also, trim it off flush.

[danielplace1962]

They were flush pickups we used but they would not supply even one drop of water so we fixed them. Now we know the are working extremely well we probably can cut the tube flush. The flush pickups had no pocket to them at the back and was straight up into the fitting. That doesn't make a pickup. It does nothing. Not even a drop was hardly coming out.

But no it didn't make any difference before or after. Slow and high speed handling was identical when they were flush and the way they are now but we probably will trim them now that we are getting huge 6" steams out of the water outlets now.

The bolts that mount the drives from the inside are up against the bottom and side and even cut out some so the head will even fit. You would almost have to grind through and cut the transom free from the boat to get them very much more inside of lower but to use these drives that is what you would have to do. The radius in all the corners is huge so it would take some intricate grinding all around back up in the hole they are in.

[iridebikes247]

I have the mhz drives on my mystic, I took a few mm off the trim pedestal to take some negative out but after a few runs learned I could have gotten away without making adjustments (or very minor adjustments). As Shawn pointed out, if the pickup is protruding it could definitely cause drag.

Countless people have built these boats for Saw events, sport running, etc. The mystic has been around since 2008 and many have achieved high speeds with the stock mhz hardware.

[rauldino132]

The boat ran the same way with the modification to the water pick ups or without still the same thing I understand what you guys are telling me about moving to dries down if I do that I would only get to Boltzen and not the third one on the bottom I don't think that will hold up good enough at the speed these boats are capable of I remember seeing it on someone site someone modified them so they go neutral

[ls1fst98]

It also looks like the reason you weren't getting water, is the pickup looks like it's to the outside of the sponson, and not nearest the tunnel, more chances of it getting into air vs water I would imagine. They should be flush.

[rauldino132]

Here you go so it's not just me

[ls1fst98]

The second pic looks neutral to me. Doesn't appear to be modded....link to the thread so we can see what they did

[keithbradley]

The boat ran the same way with the modification to the water pick ups or without still the same thing I understand what you guys are telling me about moving to dries down if I do that I would only get to Boltzen and not the third one on the bottom I don't think that will hold up good enough at the speed these boats are capable of I remember seeing it on someone site someone modified them so they go neutral

They DEFINITELY don't need to go to neutral. Trust me, you will be moving them back to negative for sure.
They can be improved by moving them a bit though. If they are too far negative, the boat will be unstable at high speed. As for the cornering, there's something else going on there.

[dmitry100]

rauldino132: You should make sure that the water jackets on your motors are with the inlets facing up. Especially the one that is going out should be the top most one. That way the water fills the entire jacket before it's let out.