General questions about twin cat

[Shimpa]

hi folks,

First post on this forum, although I do read a lot, I just don't post a lot.

I'm building a twin cat, a Mystic C5000; 900mm from bow to stern.

I got all the hardware but I've been wondering about a few stuff as the project progresses. I got:

2x Leopard 3674 1650kv
TFL stingers for 3/16" modified by me to fit under the hull (they have too much positive angle stock)
TFL flex cables left and right
TFL 4519 left and right
2x Hobbywing 120A HV's (opto isolated helicopter versions that I built a custom water cooler for - old stock from old hobby, I thought I would use them on this boat).
My plan is to run this boat on 6S

The question that's been bothering me since I saw how big the 4519's actually are; I feel 120A might be a bit on the low side here. My reasoning says that amp draw will be considerably lower per motor in a twin configuration as opposed to a single drive but still these props are really big.

I do have 4S packs to maiden the boat and test temperatures but I specifically planned this to be a 6S boat and I'm just wondering if I should get a pair of smaller props. The 4519's are quite big, the blades are huge and I feel the ESC's won't survive 6S with these props.

Which (smaller) props do you propose? I would prefer an EU-based shop if possible. Bear in mind i need a counter-rotating pair. The TFL 4219's maybe? Or should l I buy the ABC's from Hobbyking maybe?

thanks in advance,

Damir.

[iridebikes247]

Your rpm is pretty low, I would start with lower pitch though. Octura 442 counter rotating set would be a good idea. If ordering from OSE he also has cnc 45mm counter rotating sets in 1.4 pitch. Anything 1.4 pitch between 40 and 45mm would be a good start.

[srislash]

Yes, I am with Mike here. A set of 442's would be wise. Those 1.9 pitch props may lift the transom to much. You will know right away shortly after launch. Your 120's should be ok but I would be careful when setting it up. You 'should' be pulling 80-90 amps peak when running well. When running well a good prop choice would be ABC 1715's.
I do recall the marine Hobbywing ESC's having issues if pushed on 6s.
I am not trying to bust your chops just giving the advice that I have from my experience. It does seem like a good setup to be honest, it is keeping it light with solid components.
I have similar parts here for a Daytona 37".

[Flying Scotsman]

I also agree the ESC's on 6s will probably cause an issue, but your well planed and thought out components are honestly very refreshing than most novice posters. Even on 4s I would look elsewhere for an ESC.

Douggie

[Shimpa]

Thanks for your reply. Honestly I thought my rpm's are rather high. 1650kv x 24V (kinda middle ground here between a full and an empty 6s lipo) = 39600 rpm unloaded. I'm taking more experienced boater's advice that my rpm's should be around 30k loaded. I feel this is close to that number, don't you agree?

Octuras are kinda hard to get in the EU, I might need to order them from OSE and wait a few weeks till they get here. Still need to consider this :)

[Shimpa]

Yes, I am with Mike here. A set of 442's would be wise. Those 1.9 pitch props may lift the transom to much. You will know right away shortly after launch. Your 120's should be ok but I would be careful when setting it up. You 'should' be pulling 80-90 amps peak when running well. When running well a good prop choice would be ABC 1715's.
I do recall the marine Hobbywing ESC's having issues if pushed on 6s.
I am not trying to bust your chops just giving the advice that I have from my experience. It does seem like a good setup to be honest, it is keeping it light with solid components.
I have similar parts here for a Daytona 37".

Thanks for replying and the advice Mike,

I've been musing over an idea to spend another 200$ on a pair of Turnigy 180's. That will keep the maiden off by at least a month but I won't be so scared to run the boat and that's what it's all about - smiling when running the boat.

[Shimpa]

I also agree the ESC's on 6s will probably cause an issue, but your well planed and thought out components are honestly very refreshing than most novice posters. Even on 4s I would look elsewhere for an ESC.

Douggie

Yeah that's probably what's going to happen. A pair of T180's and the 120HV's will wait for another project. Maybe a 12S boat.

[iridebikes247]

Those turnigy 180s are probably going to suit your needs better especially on 6s. As far as rpm goes, 1650 on 6s isn't high anymore. A few years ago it was considered high but considering the size of the cans, props we're talking, etc, it will be fine.

IMO most motors explode because people run the wrong prop, vibrations, etc. I've run 2390kv motors on 6s in a twin cat, Shawn aka Srislash I think runs a similar loaded rpm. This is definitely an "on the edge," setup I would never rec. to someone for their first boat. Sounds like you've got the right numbers and should be good to go! Just make sure whatever batteries you've got are pretty good a lot of guys on here run into problems when trying to run low C-rating batteries in higher amp setups.

[srislash]

Yeah that's probably what's going to happen. A pair of T180's and the 120HV's will wait for another project. Maybe a 12S boat.

If you run a nice setup with similar final RPM as described above with 10-12s those 120's will be plenty.

[dasboata]

I have a set of Prop shop 4514/3 I also stock abc props if ose does not have them thanks chris


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