72" cat, thinking (12S) looking for some suggestions

[QST4IT]

Ok guys I'm ready to start buying some goodies for a big electric cat. Since there is a wealth of knowledge here I'm looking for some suggestions on whats worked from a few folks that have experience with big electrics before I pull the trigger. Just doing some homework to see I'm barking up the right tree so to speak. I've done a genesis with (2)6s\P & turnigy 180esc & leopard power pushing 70's with excellent run times. So I have a general idea where I want to go.

What I'm working on now is a 72" skater that I'd like to rig out with dual 12s drive lines. ESC's are really my biggest interest right now due to cost. Here is a list of what I'm thinking.

4ea 6s 4500mah (2ea) in Series (4500mah because I already own some)
Either (2) Leopard 56110's, or 5698's (budget minded, but a decent motor i've had good luck with & think will do the job)
ESC's obviously something 200amp+ would like data logging (looking for opinions from experience here)
This is all running into #6 style out drives with 15% up gearing. One line will be C\rotated
I already have drives and CR stainless props from Prop shop I think they were 6017's -5 blade

So I"m also debating between two different power setups and could use thoughts on this also. Looking at running it series for 12s (preferred) or I was thinking of the possibility of running Parallel @ 22v Just thoughts for now, can play up or down some with kv as needed.

Series--- 44.4v @ 640Kv(lep56110) + updrive ratio of 15% About 150 amps max
44x640=28160
X.15=4244
32,384 @ prop

Parrallel---22.2v @ 1100kv(lep5698) + updrive ratio of 15% Max 198 amps

22x1100=24200
X.15=3630
27,830 @ prop

Anyhow hopefully I listed all that right. Lol Again mainly looking for whats worked for others doing similar. I look forward to what you guys have for input.
Thanks

Ken

[jcald2000]

I don't think it will get on plane with the 5 bladed props at 27,000 rpm. 5 blades are used on low rpm shafts in full size boats like cargo ships at 200 rpm at the shaft.

[QST4IT]

JCald, We sling 5 blades on the real cats just fine up to 180mph they work well on the RC's also. Now pitch & dia. thats still up for play. This is the image of the 5 blades from prop shop.

[egneg]

Those 5 blade props require quite a bit of power and your run time will be reduced as well. I would go with at least a 300 amp esc.

[QST4IT]

Eg thanks for the input. Good points. Just like the real boats I know ill go through a few before i find "the prop" lol. 300esc is definately what id like. But if i find a 240 or so will do im game. Less cost is always a welcome bonus.

[keithbradley]

We sling 5 blades on the real cats just fine up to 180mph they work well on the RC's also.

What FE RCs are you running 5 blade props on and why?

I think you're unrealistically optimistic about the power required to move such a large boat. 6017 5-blade props pushing a 72" cat at 28,000rpm will not result in a 198A max current draw at 22.2v. Where did you get these numbers?

[bozo586]

not if it means

[QST4IT]

Guys thanks for the reply's. Again I didn't want this to be a discussion so much about the props. Although I am well aware of their importance. Luckily they are easily changed! I already own the 5 blades so they get a try if and when it gets done either way. I know I'll have several other sets to try down the road. Some good some not, with some 3 or 4 blades In the mix until I find "The Props"
As for the #'s It's what I've managed to pull together from the different manufacturers sites just trying to get a general idea to help pick suitable equipment with out pissing away a lot of money on things that don't work LOL. ( why i'm here asking questions) Kieth I see your point on the power issue ,guessing you mean I may need something more like 12S2p each side? leopard website suggest the 56110 for boat applications up to 70"s. So your right my big issue is supplying power enough for 2 of them with a KV , power & ESC combination that can work well. I see some have had good luck with the TP motors also, thoughts?

The #s I came up with in the examples were what the figures show it should be under no load. Obviously will be different loaded. And for clarity the Amp. #s were the Max amps as shown on the specs. for the motors. Actually the 56110 in 640kv didn't have specs on the website so 150 was mid way between the 520kv & the 780kv motors. This wasn't meant to be an estimated current draw for the total system. Sorry for the confusion on that. Its looking 300+amps for esc which is cool as I was leaning toward the swordfish 300. Again this is where I'm hoping for some help and direction.
Kieth what has worked for some of the Big FE boats you've done or seen done here? What are reasonable rpms @ the prop that you guys have used successfully? A good # for reasonable rpm range will help me with decisions for sure. Trust me Id prefer to spin these things at a much lower rpm to keep from frying ESCs or Exploding drives. I feel that even with these high #s in my initial examples that under load the rpm's will be considerably less. Thanks again.

[iridebikes247]

This is the kinda build where its hard to give advice, very VERY few people have built this size boat with drives like that, that hull, etc. I personally like this esc

http://keithbradleyboats.com/product/new-kbb-spec-swordfish-300/

Better wire layout, probably runs cooler, etc than standard sf 300. Correct me if im wrong but won't the prop be sitting quite deep, lower than if you used a scale arneson style surface piercing drive? If this is the case you can bet there will be more load on motor, esc, etc.

--Personally I would go with the 780kv leopard, and start on 10s. Keep an eye on temps and start with an octura x457 prop. There are quite a few mystics and hprs floating around and advice is there, its been done multiple times but this hasn't been done as much. The swordfish is an amazing esc, if this boat is setup wrong it will fry anything though. There are guys on here that can help but not many, are you on any gas forums? I'm sure as you know prop depth and drive location is important, idk it for this hull unfortunately.


Do you have any cf plate? This hull would look awesome with cf motor mounts, lipo sleds, etc.

[QST4IT]

Thanks Iride. All good suggestions. The 300esc is one that had looked at as well, and like the features. As far as the the x-dimension on these drives they will actually be similar to the surface drives with the prop shaft CL running anywhere from 1\8 to 1\4 above the bottom of the pad. Possibly even a bit higher after testing depending on prop slip etc. The drives have plenty of setback from the transom allowing for the raised height also.
I like the idea of the 780kv with the 10s. Would be a little easier on the wallet going 4-10s packs and should work well. Run time might be biggest concern I'd think.

I do mill around on some of the gas sights as well, I originally planned to go gas. But I like the electric a lot more. Once you have your setup much easier & cleaner. I agree the carbon plate would look great. I can lay some up when I'm ready.

[keithbradley]

It's not really possible to suggest an appropriate RPM range without knowing the props you will be running, but I personally think 780kv is going to be too high considering your gear ratio. Out of the motors you suggested, I would likely choose the 520kv 56110. Do you know if those drives are rated to a certain RPM?

You haven't stated what your goals are with the boat, or simply how fast you would like it to run. Once you establish a reasonable goal, you will need an idea of what props will actually push the boat. Once you determine that, you can move on to motor/RPM/voltage. If your RPM is too high, you won't be able to run a prop large enough to move the boat efficiently. Also consider that you will want 1/4" hub props on this boat (I assume that's what your drives are). I would set it up to run well with a reduced x470 and go from there. Just saying that you're going to try a bunch of props won't work. You can try different props that are similar to your original selection, but you have to have an idea of what you will be running.
You will do well to run higher voltage in a cat this size. I actually prefer 14s, but 12s is a good choice too.

[jcald2000]

Keith is right, most drives like this were originally designed for gas motors at around 18,000 rpm loaded not 30,000 rpm loaded so check with the manufacture. You might be able to upgrade the bearing ect. The other thing to watch out for is the Tq. rating for drives

[iridebikes247]

wups, didn't realize the 15% drive thing, the 520kv 56-110 motor keith rec. would be awesome with the 470 prop.

So have you decided on esc, and what kinda batteries you will be running? I hear the revolectrix are awesome, some of us have run dinogy but all that have switched to revo have noted an increase in performance. This may or may not fit your boat and is worth measuring but nonetheless something to look into, it is designed for 2p setup.

http://mbp-rc.de/Liposchienen-System-easy-move-114/450mm_1

[tazman]

JCald, We sling 5 blades on the real cats just fine up to 180mph they work well on the RC's also. Now pitch & dia. thats still up for play. This is the image of the 5 blades from prop shop.

Those look like arrow shark mc6 drives and I believe they are not geared 15 percent higher. I think only mhz z drives are geared up. I also believe that these gears are not made to be spun clockwise because they are a helical cut gear.

[DRMead]

Who makes/builds this hull?? Thanks.