1/16 Scale Cat

Quick question i want a outboard motor but dont know what one to get... I am new to all of this. So this is my idea i am makeing a catarman Sail boat. I plan to use it in wind but if it gets too choppy i need it to motor in so it needs to be not verry powerfull just enough to get it to the bank I dont mind how fast it goes... Also is there a way i could make the sails go down? I will be steering it useing a rudder useing the steering from a rc car which i will waterproof (from a cheep good for nothing chinnese toy car) which will steer it. I've got the bottom part of the hull i just need to make up the top part. Will this work? I want it to be like this:http://img.nauticexpo.com/images_ne/...aran-52473.jpg altough alot more basic :P

ryan_t888

If you were to ask your question in the sailing forum you may get better results. All the motors we use hav a lot of power. More than I am thinking you need.

Ryan

1/16 Scale Cat

ok thanks i will post it in there

stevemic

My Feedback: (5)

hI, i AM NEW TO fe, IVE RUN GAS BOATS FOR A FEW YEARS. I recently purchased a 32 inch cat with an inrunner 1880, I really need some help on choosing an ESC that will be compatable with my tactic rx tx. Someone please help I would like to run lipos...Thank you sooo much..

ryan_t888

Assuming you will run no more than 4s and the motor is an adequate size:
Castle Creations Hydra 120

Ryan

stevemic

My Feedback: (5)

hydra 120 runs 200.00, anything a lil cheaper? lol sorry but 200 is a lil steep right now lol. is that the onethat i need to get? are there other choices?

bijou

Hello.I was fascinated by these TRIMARAN boat,heare is a picture:but I can not find ANNYinformation about it!.Can some one give a hand of help with this

terryking

Hi and MANY thanks for this great thread! I am just getting back into boats and figuring out The Electric Thing.

I'll be starting out with a simpler lower-performance planing boat. Conventional hull design.

IsThere anything similar for that class of boat? I understand much of what is here is applicable.

I have sized props for fullsize boats with 200HP etc. Diameter / type from prop mfg guidelines, PITCHfrom calculating RPM, speed, and slippage.

I don't see anything specifically about PITCH here. Mostly just diameter. What am I missing??

Thanks!!
Regards, Terry King ..On the Red Sea at KAUST.edu.sa
[email protected]
Newsletter: http://redseanews.info Community Information: http://redseainfo.info

ryan_t888

I am not sure of what you mean by your first question. Similar to what? motors? hulls?

As far as props here's the lengthy explanation of why?

I look at diameter as being the independent variable. What I mean by that is, diameter is diameter. Everyone knows how to calculate this value. When a prop makes a full circle diameter is the outer sweep from the tip of the prop. This value is very easy to visualize and understand.
But what is pitch? How do you calculate that? Pitch is commonly determined by a ratio where the value depends on diameter. For a typical application where we want to travel at a decent speed, a very small pitch ratio will be quite inefficient. A very large pitch ratio will also be inefficient.

Pitch of prop = Pitch ratio * Diameter
example for 40mm prop with 1.4 as a pitch ratio
Pitch of prop = 40mm * 1.4
Pitch of prop = 54mm

This means we have a standard pitch ratio range that is best suited for our application. Every application may have a different range that is best suited. A scale type hull would use props that have very low pitch ratios. We would probably not use these in our hulls.

Diameter for a power system is a lot easier to visualize, and select a prop from. But why not calculate which prop to use instead of making a judgement based on experience???

Gas full size boats are a lot more predictable than electric boat. And especially electric RC boats. I have made several programs that calculate which prop would be best suited. Before I achieved any accuracy I had to have a large amount of variables to be input. Anything from size of hull, type of hull, down to the power system specifics.
These calculated values the selection close but was never right on. It can't and won't ever be. Full size or Hobby size. But for electric, overshooting the diameter can ultimately lead to electrical failure.

This is the reason I use diameters in the chart and greatly emphasize to always ask about prop size if unsure. The wrong kv motor on the wrong cell count, with the wrong prop is going to be very destructive. Just one of these variables incorrectly matched may experience failure.

Once diameter is selected you can start with a small pitch ratio. From here it is just a matter of experimenting with greater pitch ratios/diameters ect.

You could then calculate speed based on slippage, Loaded Prop RPM and pitch used. I would strongly advise against calculating pitch from speed desired by re-arranging your equation. Reason is, we back track to where I mention failure if the pitch you select is too great for the motor.

Greater Pitch may affect:
- Prop Slippage
- Prop Lift (Hydros typically have higher pitches ratio's for greater lift)
- Motor Load ( A motor will turn the load you hand it whether it melts from ehaustion or not / A gas engine will not turn an increased load if it does not have the power to do so)
- Speed ( Easy to understand more pitch may increase speed. But keep in mind more pitch can also slow you down. This is harder to visualize)
- Thrust ( Greater Pitch ratios may decrease thrust. Thrust is needed for maximum acceleration/getting out of the hole)


Ryan

TFLHOBBY-Candy

Thanks a lot for your info.
I am a new RC Boat model man.
with my great honour to share this interesting time with you.
I need to learn more about the boat.
If you are interesting ,pls feel free to contact with me .
I will be a good student ,and show you my harvest .
SKYPE:TFLHOBBY-Candy
MSN:[email protected]

Candy

ryan_t888

If you have a/any question(s), just post them or PM.

Ryan

TFLHOBBY-Candy

Ryan:
Thanks a lot for your reply.
After I read this topic,as I know there are 3 kinds of boats . Monon , CATAMARAN ,   TRIMARAN.
I am so missing about it ,and could you pls show me how to differentiate them.it is better explain  with some pictures.
thanks
Candy

TFLHOBBY-Candy

AH....
I find the answers on your topic
thanks a lot

Candy

1/16 Scale Cat

What waterproof servos do you use? Thanks

Liam

ryan_t888

I have never used water Proof servos. What I use is a water proof hull. In FE you must insure that the hull is water proof. If you still wish to have water proof servos. I would take your favorite servo and manually water proof it. This procedure should be searchable.

Ryan

1/16 Scale Cat

Ok, thanks i wasnt sure. my hull is watertight but wanteed to check thanks

liam

TFLHOBBY-Candy

I haven't use water proof servo too ,common is Plastic Servo 3003

BARRY.E

Hi Ryan, I have a question.

The thrust/forward momentum generated by the prop, at what point or postion in the Hull is this force appiled in these FE Boats, I would of assumed that the force is applied at the Transom through the Stinger/Strut/Brass Tube setup, but various posts mention a thust washer setup at the motor/ coupler end which would suggest that the prop force is applied at the motor location, does it actually matter if the prop force is applied at the Transom or the Motor/Mount, also do these flexi-Shafts wind up to a point where they do shorten under load and require a gap between the drive dog and the drive shaft/tube.

Barry

ryan_t888

Hello Barry

It seems as if you have already answered your question, I'll just connect the dots.

With a flex drive system the cable does tighten up to a certain extent. Due to this, a space as thick as the cable must be kept from the stuffing tube to the drive dog. Since there is space between these two components the thrust travels up the flex shaft and this is the reason for a thrust bearing. As a result the thrust does end up on the motor mount or motor can. I prefer the motor mount.

Some models use a square drive system. The thrust would typically be on the transom with this setup.

Ryan

bikenewby

Hi,

I've just got the 42" Deep V hull from Hobbyking (link below) and wondor what would be a good matched for brushless motor?
I'll go with Feigao 580XL size but still considering if I should get 1300KV, 1000KV or 750KV? The prop size is around 2.12"(Hyperformance 240 size).
What would be a matched KV if I run 6 cells? and what's about 8 cells?

Thanks in advance.

http://www.hobbyking.com/hobbyking/s...dproduct=15235

itsfishi

hi can you tell me how to work out what size flex cable to use.

thanks very much

ps great thread very informative thanks

ryan_t888

If this is not too late. I would not go any higher than 1000kv. 750kv would almost be a better choice for just fun running on 8 cell LiPo.

How much power do you plan to run? Flex cable decision depends on the amount of power or better yet the amount of torque placed on the driveline.

Here is a rough chart for size vs power for fun run type boats. This is not set in stone for example I have run smaller cable on some 2 cell hulls and currently run .187" for a 4s hull.
.125" for hulls running 2 cell LiPo
.150" for hulls running 4 cell LiPo
.187" for hulls running 6 / 8 cell LiPo
.250" for hulls running 8 / 10+ cell LiPo

Getting a little technical, A 1000W system running at 40 000RPM will not need as thick of a flex cable vs one running 1000W at 20 000RPM. At a lower RPM the same amount of wattage will produce more twisting torque on the flex cable.

Ryan

itsfishi

thanks for the info . gonna be running 3s 25000 rpm but maybe 4s aswell sometimes 3400rpm

would .130" be good or should i go .150"

thanks again

cheers

ryan_t888

.150 probably won't hurt.

Ryan

bikenewby

Hi,

Thank you for your recommendation. I actually get the 750KV to stay on the safe side, especially with the Feigao.