Counter-Rotating Prop Options for my 36" Cat??

[capnswanny]

Ahoy All,

I've spent that past couple days searching and trying to identify some good prop options for this 36" Cat that I put together.
Does anybody have any suggestions based on my setup??

All I've got now are the 45mm Graupner K props. I see Steve has the X442 and X447 in the store, but I'm

I've got matching sets of AQ1800KV, AQ2030kV, and soon Electrifly 2300Kv motors.
Using two AQ60A ESC's and 4S 5000mAh 40C Zippy packs FWD of each motor.
I've tested the 1800 and 2030 using 45mm carbon props on 4s. Speed with both was a very stable 40mph running a little wet.

I know I'm very limited with these ESC's and motors, but it's what I've got right now and I'm wanting to take this setup as far as I can.

It's been a great learning experience so far, and I look forward to learning more from you!!

Thanks in advance for your help,
Corey

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[srislash]

PropShop has some 4512's and 4518's. The 1.8's would be pushing the Esc's though. Most likely too much. The CNC two blades would do the trick as well. I believe Steve has em here.
Any vid of it?

[srislash]

The 2300kv's will also push those speedy's. Is she pretty light?it looks like it should be. My 37" shocker was 10lbs to give you reference .

[capnswanny]

The two times I ran I didn't shoot video...I will next time.

So I Just threw it on the Salter kitchen scale with 2-4s packs installed, reads 7lbs- 12oz, I'd give or take a few ounces.

Steve has CNC L&R 4514's (total pitch =2.52"), looks to be almost the same pitch as the current K props...but of much higher quality.


I really need to get the nose up a bit.
The motor mounts were installed when I bought the hull from Ray Fuller, and they weren't budging without taking the skin with! Batteries are as far back as they can go and they won't fit on tunnel where the ESC's are.
I hate to do it, but would it be cool to add a bit of weight to the back?

Thanks!

[tlandauer]

Thread subscribed, want to learn!

[srislash]

The two times I ran I didn't shoot video...I will next time.

So I Just threw it on the Salter kitchen scale with 2-4s packs installed, reads 7lbs- 12oz, I'd give or take a few ounces.

Steve has CNC L&R 4514's (total pitch =2.52"), looks to be almost the same pitch as the current K props...but of much higher quality.


I really need to get the nose up a bit.
The motor mounts were installed when I bought the hull from Ray Fuller, and they weren't budging without taking the skin with! Batteries are as far back as they can go and they won't fit on tunnel where the ESC's are.
I hate to do it, but would it be cool to add a bit of weight to the back?

Thanks!

Yup, she is light.That'll help with the ESC's. If you had a pair of 120's in there you could push it a bit more. My twin Geico runs Proboat 1800kv's and 645 CNC's on 5s and runs 80 amps peak. I think it is similar in weight. You will want to have the CG at 30-35%. Are those stingers adjustable?

[TheShaughnessy]

Ok I can't seem to talk myself out of posting theory with no directly related first hand experience . Now that's out of the way here is what I would do if I were you and had the options you described.

First I would ask myself, am I doing the work on these props or am I paying for a finished product. Before I answered that I would also ask, either way is this amount of money a factor right now. Ok so I'm paying for finished props and I'm comfortable paying 100 for a set but 200 for both sets isn't gonna fly, for what ever reason.

In that instance I would get the 447 and use the 1800 AQ motors. Here comes the theory.
I run a 1800 kv in a 29 inch cat and spin a 447 with minor work done. It pulls 50 -55 amps running WOT in the straights. I back off just a little to settle it down and amps will go way down,as little as 10 amps but that's only for a moment, once I get back on the throttle I see spikes in the 70-75 range and then it will settle back to 50-55.

If I did the math right you boat is about 24% bigger but also has 100% more power so I would think it would be fine. If that set up ended up running real cool or I logged a run and came back with a 40 amp average and I wanted it to go faster I would switch out motors for the 2030 kv ones.


Scenario 2 is the money or time isnt a factor and you get both then start with the 442's and work up.

Hopefully that helps a little with deciding whether or not the bigger hull will push the 60 amp esc's ( I run a turnigy 120) to the breaking point with 447's

One thing to remember is the carbon props flex more under load and actually lose some pitch so a 45 mm CuBe will pull more amps then its carbon counterpart

[axel]

First the Carbon have a true pitch of 1.25 , so with metal 45 size you get true 1.4 pitch.
If then everything still stays cool you can try the x447 or ABC 1816 but they have 1.6 pitch so careful.
I would try some Aluminum 45 with 1.4 and if still everything is cool try the 1816/3 .

[jcald2000]

Move the esc's to in front of motors and shorten their wires to motors and put battery's where esc's were.

[capnswanny]

Thanks, I tried that, but there's not enought room under the hatch to fit the batteries on the tunnel.

Move the esc's to in front of motors and shorten their wires to motors and put battery's where esc's were.

[axel]

leave it as is by getting faster the COG will have to be placed more forward, just try and see

[capnswanny]

I haven't played with the 3 blade props yet, is there a significant change in amp draw (Temps) for similarly sized 3 vs 2?

First the Carbon have a true pitch of 1.25 , so with metal 45 size you get true 1.4 pitch.
If then everything still stays cool you can try the x447 or ABC 1816 but they have 1.6 pitch so careful.
I would try some Aluminum 45 with 1.4 and if still everything is cool try the 1816/3 .

[capnswanny]

I was hoping for that :pray:...the faster I go, the more air I pack, the more lift I get, the looser I run.

leave it as is by getting faster the COG will have to be placed more forward, just try and see

[capnswanny]

I hadn't considered the amount of flex on the carbon props...thanks. I wish I had logging, I would be interested to see the difference in load on these setups with two. That was one thing I was wondering, could I swing a bigger prop that I normally do as a single?

I like the x447 idea on 1800, I will order those and give them a shot. I think I might order the x442 as well, might work detongued with the 2300's.
Of course the CNC 45mm will probably work well with the 2030.

Payday is in two days!

Do you think delifting them a bit (back/barcut) would help given my COG?

Ok I can't seem to talk myself out of posting theory with no directly related first hand experience . Now that's out of the way here is what I would do if I were you and had the options you described.

First I would ask myself, am I doing the work on these props or am I paying for a finished product. Before I answered that I would also ask, either way is this amount of money a factor right now. Ok so I'm paying for finished props and I'm comfortable paying 100 for a set but 200 for both sets isn't gonna fly, for what ever reason.

In that instance I would get the 447 and use the 1800 AQ motors. Here comes the theory.
I run a 1800 kv in a 29 inch cat and spin a 447 with minor work done. It pulls 50 -55 amps running WOT in the straights. I back off just a little to settle it down and amps will go way down,as little as 10 amps but that's only for a moment, once I get back on the throttle I see spikes in the 70-75 range and then it will settle back to 50-55.

If I did the math right you boat is about 24% bigger but also has 100% more power so I would think it would be fine. If that set up ended up running real cool or I logged a run and came back with a 40 amp average and I wanted it to go faster I would switch out motors for the 2030 kv ones.


Scenario 2 is the money or time isnt a factor and you get both then start with the 442's and work up.

Hopefully that helps a little with deciding whether or not the bigger hull will push the 60 amp esc's ( I run a turnigy 120) to the breaking point with 447's

One thing to remember is the carbon props flex more under load and actually lose some pitch so a 45 mm CuBe will pull more amps then its carbon counterpart

[capnswanny]

I only have a single 120 now or I'd try the 45's on the 1800 at 5s, the AQ ESC's really stick me at 4s...makes it a little more challenging
If I pull the stingers and do a little more grinding I can get a couple more degrees up, right now they are adjusted slighly positive as far as they will go.
Looks like I'm sitting at 36.11% COG right now...dang!

Yup, she is light.That'll help with the ESC's. If you had a pair of 120's in there you could push it a bit more. My twin Geico runs Proboat 1800kv's and 645 CNC's on 5s and runs 80 amps peak. I think it is similar in weight. You will want to have the CG at 30-35%. Are those stingers adjustable?