30" Scratch Built Cat

[lomdel]

If I decide to use two of these http://www.astecmodels.co.uk/catalog...roducts_id=553 , where can I get two counter rotating 4mm flex shafts assembled with 4mm drive shafts?

[Jeff Wohlt]

I am just finishing some bearing struts that run 4mm bearings and then it steps up to 3/16 prop stub. I am doing this because I wanted to keep the struts smaller for 2S-4S stuff. I am now working on some bigger 3/16" shaft struts with bearings. They also have a lube hole for the bearings.

I can make the shafts for you if you do not find any.

[Jesse J]

Those look GREAT Jeff. Could be the answer.

However, how does one resolve the problem of prop sizes: counter rotating come in 42mm and 47mm, nothing in between? How does one have much of a selection?

[Jeff Wohlt]

Hey Jesse. If it were me with limited choices on props then you do your build for the KV/Volts. Should be no problem running the 47s on 6S 12-14 XL. I have not done it but seems no problem amp wise.

[Simon.O.]

Those look GREAT Jeff. Could be the answer.

However, how does one resolve the problem of prop sizes: counter rotating come in 42mm and 47mm, nothing in between? How does one have much of a selection?

I have a similar issue although the whole Cat is still in the concept stage.
GHraupner have the CF props in R+L rotation in 40, 42 , 45, 48mm dia.
The pitch on these seems to be a bit of a point of discussion as some tell me they are 1.2 and others say they are 1.4.
I will use these when it come time to do a Twin cat and use rpm to get speed.
30krpm will be my min calculated shaft speed using 1.4p as a constant. IF they are 1.2 then they will unload and scream !!!!

Just a thought.

btw Jeff that work that you do is spectacular. I love it and aspire to make parts that could look half as good.

[Jesse J]

Yo Norman, how's progress? I know you are doing single drive, but this size cat is entering into the twin realm. What size motor/esc are you thinking? Batteries? Updates please

[Norman2]

30" Scratch built Cat

Hi Jesse, Well I have started the 1/16" sheeting. Did some during the week end
and some today. Will let it dry all day and start putting in flotation before I do the
bottom. Well I know I will get all kinds of feedback but I am going to start this out
with a 700 OSE SC brushed, Jetti 600 60 amp ESC. 14 NIMH 4600Mah cells, .150
flex and Octura X447, OSE IN-Line strut/rudder, Water cooling for motor and ESC.
If it floats and runs halfway decent I wil go to brushless and lipos. Did not want to
invest too much to see it sink on the first try, I have to learn how to set up cats.
I am good with my Mono but the set up is tried and tested in racing here in our
local club in LSO. Will post photos soon. Regards
Norman

[Jesse J]

I had never thought of doing decking first... Always started with bottom, sides then decking. Guess there are more than one way to skin a cat, eh?

[lomdel]

On my side, I had the balsa and ply laser-cut tonight. That was really cool to watch . I didn't have my camera with me so I took a few cellphone pics, see below.
I will post pics of the cut-outs and the pre-glue assembly tomorrow. You will see I had strut G cut in two options, one for twin motors and the other one as a single motor mount. I have actually decided on the twin 8XL on 4S each spinning X442 props set-up, but I like to have a back door open...

[Norman2]

30" Scratch Built Cat

Hi, Looking super. I wish I could have had a laser cuter near me because I spent
many hours cutting out mine with a scroll saw. regards
Norman

[Simon.O.]

I have actually decided on the twin 8XL on 4S each spinning X442 props set-up, but I like to have a back door open...

Is this cat is 30" to sponson rear or 30" overall ??
I ask because TWO 8XL's sound like a LOT of power in there. Unless someone tells you that it is certifiable madness to do so then go for it.

I'm watching this one

[lomdel]

Norman. It is a great advantage to have access to such a machine. The total cutting time for all the parts was about 25 minutes. They were cut to an tolerance accuracy of 0,1mm. The pieces fit together perfectly.
Simon. The main stringers is 770mm total length and 764mm to rear of sponson. If you think 2x 8XL is too much, what would you suggest? 2x 9L's on 3S would have more or less same rpm but be lighter and I have some 3S packs here.

[lomdel]

Here are a few pics of the cut-outs and a pre-glue temporary assembly. You will notice the two motor mount options that I can still decide on, either twin or single...

I am going on holiday for a few days so this project will be dormant for a while.

[Simon.O.]

Simon. The main stringers is 770mm total length and 764mm to rear of sponson. If you think 2x 8XL is too much, what would you suggest? 2x 9L's on 3S would have more or less same rpm but be lighter and I have some 3S packs here.

Go hard for the 8XL IF you already have them, I seem to remember that you got a few a while back.
I can not say if a pair of 8XL's is too much, I want to know if they are.
I am keen to go 8L or 10L on 4S Given that I have some good 4S packs here.
To do this I need to buy motors and speedies.
From one supplier the motors are nearly the same price for a L or XL, A 100A or 125A speedy each should be plenty.

I am still doing my research on 30"+ Twin drive Cats and would like to pop into this thread to help. If anyone objects, shout out.

I am watching

[lomdel]

I don't have any 8XL's but I do have a some 3S Lipos that I could use. To use them I must go with the 9L but I am a bit unsure... I PM'ed Reddywatts for some advice. Anyone else with suggestions would be much appreciated!