MHZ XCAT 1400mm (55") build.

[Rich]

So I decided to pull the trigger and build this boat instead of the DF Annihilator. I have the hull, outboards, linkage kit, and oil ordered from MHZ. They are waiting on the outboards so I have time before it gets here. I figured that I would ask the forum what power system I should go with? I was thinking this:

leopard 4092's 700 kv
swordfish pro +II 240 12s esc with hifei high voltage caps
8mm antispark connectors
12s each side (2 x 6s 8000mah in series)
starting prop x450 counter rotating
separate LiFe pack for servos
Spektrum SR315 3-Channel DSMR Sport Receiver

I would like 60mph+ or 80mph for short bursts if that is possible

Do I need the 240's or could I go with the swordfish X+ 150 hv?
Should I do props out or in? Do I even need counter rotating props?

Any help would be appreciated.

Thanks guys!

Rich

[Rich]

Nobody has any suggestions? I am surprised.

[ArnoudRC]

Hi. On a twin cat I?d always use two different direction turning drivelines. Does not really matter on what side cw or ccw.


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[Rich]

Hi. On a twin cat I?d always use two different direction turning drivelines. Does not really matter on what side cw or ccw.


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Thanks for the info! Any ideas on the setup?

[Jesse J]

I think this is the first xcat at this scale I’ve seen on this forum.
Maybe if you give us some eye candy (photos) to inspire conversation it would help.
My thoughts:
motors: seem fine, small, but as twins should be ok.
Esc: think of load on inside motor on a turn, it’s the ripple that ramps up unexpectedly. I posted data from a twin cat that had data recorder on each motor.. biggest spike was in the ripple. So, I’d go bigger on esc than if it were a single.
Prop rotation: I like inward, just thinking of the inside motor and the rotation that would most enhance cornering on a mono. But.. Much of the commentary comes from cat trials.. and most say either is fine. I defer to them.
Please share learnings as you go.

[Rich]

Thanks Jesse J, the order hasn't shipped yet they got the material for the outboards last week. They said it will be 2 weeks from then so we will see. I'll definitely post pics when I get it. This video is what inspired me. He shows the setup at 1:48 ish. https://youtu.be/tZTARkPh-N8. It's the same setup that I posted. I felt I'd ask here to see if it was realistic.

[ArnoudRC]

Amazing handling on that rough water. Follow your build.


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[Rich]

Got the hull and outboards today! Man this thing is huge! Can't wait to get started on the build! I was thinking of building a trailer so one of my rc trucks can tow it. Carrying this thing to the lake will be kind of tough. That being said, should I go with the ZTW esc's since they have reverse? I am thinking I might need it for backing off of the trailer. I also run my boats in a narrow channel so reverse isn't a bad idea. Any thoughts on the ZTW escs?



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[Rich]

Well I got started on the build. I got a lot of goodies from ose (thanks steven!) I started by putting the outboards together. A few things to note when putting these together. The screws that hold down the motor mount that are closes to the mounting plate that goes to the transom are a pain to get to with a long cooling jacket. I would suggest you put the screws in first then mount your motor. Another tip if you get these outboards for your next project is to use the fitting that comes with the outboards to fill the oil. Its screws into the silver nose cone and you put a pc of fuel tubing to the syringe and to the fitting, then inject the oil until it comes out of the vent screw. The vent screw is a small screw where the lower unit meets the mid plastic pc of the outboard. I plan on using a through hull water fitting to run the cooling out the back of the outboard to give it a scale appearance when the boat is moving. I will attach that to a pc of tubing going to the top of the cooling jacket. Ill show a pic of that when it its done. The only problem I have is where to put the water pickup for the outboard. I was thinking of bending a pc of 5/32 brass tubing and having it mount to the cavitation plate and use it as a prop wash setup. I think it would look scale like that. Any other ideas? I really don't want to add an thru hull pickup or one that mounts to the transom if I don't have to. I am planning to use a transom mount pickup for each of the ZTW's though.GOPR1451.jpgGOPR1452.jpgGOPR1453.jpg

[Rich]

Got the outboards installed. I also got the propwash water pickup installed. I need to cut the angle for the intake bit here it is. What do you think?20201103_195805.jpg

[Jesse J]

Exciting!! What depth did you go with, propshaft center to bottom of hull?

[srislash]

Very nice project Rich, these outboards will have an adjustable ride height I assume? Prop wash looks good. As Jesse mentioned inward rotation will be best. Having the drives do the steering does change the characteristics a bunch. I tried outward and it just sucked.

[Rich]

Jessej, yes I did mount the center of the prop shaft to the bottom of the hull just a start. I noticed on the pictures on their website that they put the centerline of the prop shaft on the next step out. I'll show you a picture when I get a chance.

Srislash, these drives do have up and down movement maybe a quarter inch? I drilled the holes for the motor mount in the center of the slot so I'd have movement up and down. My first attempt at doing the holes was way off so G flexed them shut and made a template for the holes like I should have done. I redrilled the holes and they came out way better. The drive on the right though is in about a sixteenth of an inch from the other one not sure what that's going to do. We will see.

Thanks guys! More work will be done tonight. I should have a package at my door from ose today. I also have another coming from MHZ....look out for another thread soon...

[Rich]

Here is a pic of what I mean by second step. 20201106_164150.jpg

[Rich]

Did more work on the boat and gave it the maiden run!
I machined a servo mount and glued in the esc mount using the jb weld dam method. Came out good. I just need to find a way to make it spread even. I also glud in the battery mounts with this method. The cardboard is not a good idea for a epoxy dam I'll have winter to cleand that mess up.
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