1.1M Cat setup help

[Jeff Wohlt]

I would stay with 6S. Yes but it has the mass to spin a decent prop without loading the motor very much I think it would be a good set up. You can run 4 or 5S to start with but it does say 6S. Looks like a well built motor for a cheapo. Screwed in rear plate, etc. Numbers are not that bad either.

Not sure anyone had seen these. I owuld have said KB 45 but they seem to be big amp hogs.

[Brushless55]

6s I think will be to much on a 2000kv motor in a big boat?
44,000rpm

[Himalaya]

I personally prefer inrunners, for :

the conviniency to get it water cooled

much faster throttle response than an outrunner having similar power capability

much higher RPM capability, wider KV choices available.

much thinner motor diameter, results in less bend angle to the flex cable and stuffing tube and thus higher drive train efficiency.

[Ub Hauled]

Here...if you want some meat and muscle. Well built and 6S on each would be great. I would not hesitate to push it to 8S either.

This is what I would use for big hulls. You need the mass of 44mm dia. Shaft is already reduced.

http://cgi.ebay.com/Large-B44-2000KV...QQcmdZViewItem

Jeff, that seems to be a nice find... thanks for posting.

[Simon.O.]

1.1m is close enough to 115cm which by a stroke of good luck is the length of the HPR 115.
Have a look here for some power ideas
http://forums.offshoreelectrics.com/...ead.php?t=7899

I'll help if I can.

[norbique]

Hi! Thank you all for your relpy!

What do you think about using two of these motors in the cat?

https://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idproduct=4937

or this one, it's quite similar to what Jeff Wohlt suggested on ebay:

https://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idproduct=4938

Simon, I hear others saying you're an expert in scratch building.
I want to ask you what do you think/recommend what would be the best way to reinforce the balsa cat?
I am planning to plank hull with 2mm balsa first, then ontop of that plank again with 0.4-0.8mm birch ply. Would this suffice for this huge boat or should I even add fiberglass to the outside/inside of the hull? Glassing the inside would be much more difficult though...
Thanks!

[EPower]

Hi! Thank you all for your relpy!

What do you think about using two of these motors in the cat?

https://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idproduct=4937

or this one, it's quite similar to what Jeff Wohlt suggested on ebay:

https://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idproduct=4938

Simon, I hear others saying you're an expert in scratch building.
I want to ask you what do you think/recommend what would be the best way to reinforce the balsa cat?
I am planning to plank hull with 2mm balsa first, then ontop of that plank again with 0.4-0.8mm birch ply. Would this suffice for this huge boat or should I even add fiberglass to the outside/inside of the hull? Glassing the inside would be much more difficult though...
Thanks!

I use KB45 motors they are great,Amp hoggers for sure but with the right prop & esc they will work fine
they are not in stock at the moment and the ETA from hobbycity is 8 to 10 weeks LOL

Adrian

[norbique]

Thanks Adrian!
By amp hog, you mean it needs a higher amp ESC than other motors would? Less efficient?
Would a 100A watercooled ESC be enough for the KB45-10L 1800kv on 6S2P A123?
And what ESC for the KB45-08L 2300kv with 4S or 5S batts?

[Simon.O.]

Simon, I hear others saying you're an expert in scratch building.
I want to ask you what do you think/recommend what would be the best way to reinforce the balsa cat?
I am planning to plank hull with 2mm balsa first, then ontop of that plank again with 0.4-0.8mm birch ply. Would this suffice for this huge boat or should I even add fiberglass to the outside/inside of the hull? Glassing the inside would be much more difficult though...
Thanks!

Expert ?? Just an enthusiast.
2mm balsa may be sufficient if you have small frame spacing and stringers.
For a hull bottom I would go with 3mm and cover with 1mm ply expoxied on. this will be very strong. i would suggest that it would be stronger and stiffer than a lot of glass hulls.
My new 30" has 3mm bottom without ply skin but as with the 4S rigger it will get a lot of varnish laid on.
Ply and epoxy are expensive for me to use on hulls so that is why I use more balsa and varnish.

Some of my work
http://forums.offshoreelectrics.com/...ead.php?t=8008
and some reading.
http://forums.offshoreelectrics.com/...ead.php?t=7494

Enjoy.

[EPower]

Thanks Adrian!
By amp hog, you mean it needs a higher amp ESC than other motors would? Less efficient?
Would a 100A watercooled ESC be enough for the KB45-10L 1800kv on 6S2P A123?
And what ESC for the KB45-08L 2300kv with 4S or 5S batts?

they do draw allot of amps i blew a TURNIGY Sentilon100A HV on the second run on 6s brought an Etti 150 race blew the capacitors on it i had it replaced and had the capacitor module fitted to it and so far so good
on the KB45-08L 2300kv 4s would be the max i would run,and start with small props x442 or similar these motors are rated at over 3000 watts
I have to say that i do push these motors to their limit but then they are cheep to replace
i gave my boat a short run about one minutelast Sunday with my new Hyperion 5500mAh/35C batt and could really feel the difference in power we will see how the motor & Esc will cope with 3 minutes runs
what esc did you want to run in it?

Adrian

[norbique]

Adrian,
I was thinking of the TURNIGY Sentilon100A HV, but replace the caps for super low ESR ones with higher capacity asap Yes, good batteries are a must. I have some A123s and they're amazing. I will use only use those in my future projects. No lipo fires, not even the thought in the back of my head it might happen anytime.
A KB45-10L 1800kv on 6S2P A123 is what I am thinking about. But I don't know will the Turnigy hold up. I'd rather go for a lower KV motor and go up with the volts.

Simon,
Thanks again for your help. I was to use 2mm balsa on the bottom too, but I'll listen to you and use 3mm on the bottom and 2mm elsewhere. Also I will use 0.8mm ply on the bottom and 0.4mm ply everywhere else epoxied. I can buy the ply at relatively good price.

EDIT: Thanks for the balsa build thread link. Now I'm afraid All my bulkheads are from 5mm hard balsa. Except for the last one where the shafts will go through, that one is 5mm ply.

I must build my boats extra strong, but not only because of speed. Last weekend I ran across a bough floating on the surface of the water with my Hydromite. It threw the little boat half a meter out of the water. Luckily I only bent the turn fin, nothing else was damaged.

[EPower]

Adrian,
I was thinking of the TURNIGY Sentilon100A HV, but replace the caps for super low ESR ones with higher capacity asap Yes, good batteries are a must. I have some A123s and they're amazing. I will use only use those in my future projects. No lipo fires, not even the thought in the back of my head it might happen anytime.
A KB45-10L 1800kv on 6S2P A123 is what I am thinking about. But I don't know will the Turnigy hold up. I'd rather go for a lower KV motor and go up with the volts.

Simon,
Thanks again for your help. I was to use 2mm balsa on the bottom too, but I'll listen to you and use 3mm on the bottom and 2mm elsewhere. Also I will use 0.8mm ply on the bottom and 0.4mm ply everywhere else epoxied. I can buy the ply at relatively good price.

You don't really have to replace the ones on your esc just add some to your batt wires and try to keep them as close as possible to the esc side of the batt wires have a look at the picture

Adrian

[norbique]

I mentioned replacing the ones in there since I'm going to disassemble it to add water cooling anyway. But your setup is easy to make, thank you, I'll consider it!

[crabstick]

Hi Norbique,

For your build I would recommend thin ply!! it will last a lot longer. there is a lot of load on the hull and hardware at 100k and can bend rudders and struts if they are not up to the job. I have recently finished building a 35 inch cat with ply after my previous balsa cat self destructed on a blowover... sure its heavier, but I have a lot more confidence in the strength of the boat.Ply is pretty easy to work with as long as you have a steady hand, a sharp hobby knife and a steel ruler.
From the examples I have seen and read about IMO a 40 inch'ish light twin 8xls on 4s each should be able to reach that 100k for sport or SAW runs.
The KB45 8L is a motor I am curious about and if it goes as good as the specs it might be another option, they are a bit heavier than the 540xls. power to weight to consider, also load on the hull.

IMO I think you may have to purpose design the hull, with minimal lift in the tunnel, because as the boat goes faster and faster more lift is obviously provided from the larger volume of air passing through the tunnel and then over she blows!!! lol we dont want that

for batteries if you dont want to spend a squillion, these could be an option
run 2p to each esc.. Obviously get the best packs you can afford, but if you are on a budget, these might be the ones to get.

https://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=8916&Product_Name=ZIPPY_Flightmax_2650mAh_4S1P_30C_

I have recently got some of these and am finding them good so far, they were 40degC after running my cat today and all cells were within .02 of a volt per cell of balance after running. Setup was the KB45 8xl on 4s2p for about 4 mins on m447, speed is around 70kmh in calm water, All in all im not too happy with the KB on 4s at the moment, I might get the 8L and try it. So duee to my findings I would NOT recommend the KB45 8xl for 4s, they are just too low in KV and you have to run giant props.

Those motors Jeff posted the links to look the same size as a kb45, but has detachable endbell by the looks! wonder what it goes like


For the Caps - checkout Shultze's website, theres a howto there

Cheers!

[EPower]

Hi Norbique,

For your build I would recommend thin ply!! it will last a lot longer. there is a lot of load on the hull and hardware at 100k and can bend rudders and struts if they are not up to the job. I have recently finished building a 35 inch cat with ply after my previous balsa cat self destructed on a blowover... sure its heavier, but I have a lot more confidence in the strength of the boat.Ply is pretty easy to work with as long as you have a steady hand, a sharp hobby knife and a steel ruler.
From the examples I have seen and read about IMO a 40 inch'ish light twin 8xls on 4s each should be able to reach that 100k for sport or SAW runs.
The KB45 8L is a motor I am curious about and if it goes as good as the specs it might be another option, they are a bit heavier than the 540xls. power to weight to consider, also load on the hull.

IMO I think you may have to purpose design the hull, with minimal lift in the tunnel, because as the boat goes faster and faster more lift is obviously provided from the larger volume of air passing through the tunnel and then over she blows!!! lol we dont want that

for batteries if you dont want to spend a squillion, these could be an option
run 2p to each esc.. Obviously get the best packs you can afford, but if you are on a budget, these might be the ones to get.

https://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=8916&Product_Name=ZIPPY_Flightmax_2650mAh_4S1P_30C_

I have recently got some of these and am finding them good so far, they were 40degC after running my cat today and all cells were within .02 of a volt per cell of balance after running. Setup was the KB45 8xl on 4s2p for about 4 mins on m447, speed is around 70kmh in calm water, All in all im not too happy with the KB on 4s at the moment, I might get the 8L and try it. So duee to my findings I would NOT recommend the KB45 8xl for 4s, they are just too low in KV and you have to run giant props.

Those motors Jeff posted the links to look the same size as a kb45, but has detachable endbell by the looks! wonder what it goes like


For the Caps - checkout Shultze's website, theres a howto there

Cheers!

4s for that motor is not enough juce m8 i have some 6s 4500 mah zippys you can have, might not be able to handle the power LOL