Same 30"cat, limited experience

[Simon.O.]

Finally got to run it today... 40-50kph,
That speed looks nice for that size pond
quite slow as I was afraid to crash:
Being cautious is good, rebuild a hull is bad
I am still an absolute beginner in controlling these things...
You are learning faster than I did.
Need a bigger rudder for sure,
I am not so sure you need a bigger rudder at all,

Cornel.
The rudder on my Cat is quite small, It is less than 1 prop dia below the prop which is a common guideline. Mine will change direction like a pinball at anything other than wot.
Your steering issue could be one of a few things and my main suspects are.

1. Rudder too large
2. Too much throw on the rudder from servo to the rudder. 30deg each way is lots.
3. Too much steering input from the driver.

I have a very basic Hitec FM pistol handset but I can alter the steering rate/throw with a thumb wheel. I use this to adjust the "sensitivity" of the steering of my boats.

Have another look at you whole steering setup and if you want to put up a few pics of the steering end of the boat and I am sure there will be some positive and helpful comments.

You have done well so far. I bet you are well happy with that !!

[CornelP]

Help!!!!!

Ok, here is the new rudder setup. A lot fore solid than the first version... Still need to make some space for the prop...
Anyway, take a look at the size, which one would you recommend in the last pic? Both are 1mm stainless steel.
Base for this rudder is a Graupner rudder, and it seems slightly wobbly... that is it will have a 1 degree deflection... on both axis... probably a washer will cure it, but is this normal?



PS the biggest problem I had was that in a straight line WOT I had to correct with 30% rudder to keep it straight. Somebody also suggested the servo is not strong enough...

[CornelP]

Finally top 70s

Finally got a decent run out of this hull...
No radar today, but a number of calibrated eyes on the pond suggested top 70s (kph). I will confirm next week, if we have a radar... This is a run on 6S, with a 45K prop, perfect combination... the only thing that got hot was the coupler and shaft, as the power was too much for my homemade ones... lost one prop and reconnected coupler 3 times. Once I settled everything, it ran stable until depletion of batteries... around 6min in total (2x3S 4200 20C series)

http://www.youtube.com/watch?v=S0Keo1CsoEU

[norbique]

Very nice cat Cornel! Good job! The wire drive is nice too. I like it a lot. I just watched the videos, and I think you should get a GPS unit to confirm speed.
I'm building a slightly bigger cat which I want to power with two motors. It came to my mind not to bother with right and left handed flex shafts, but make it a wire drive, but dropped the idea cause I haven't seen one in action until now. Now started thinking of it again. So I'm learning from you Keep on!
Norbert

[CornelP]

New hardware

Ok, after the "powerflip" last week (WOT, a bit windy, batteries too far back), it flew 5-6m at an 'altitude' of about 1m, I had to redo the strut, rudder mount and drive...

So this time I went a bit heavier: the aluminum angle is 3mm thick, the rudder mount is about 5mm. Total weight 170g, so i had to move the batteries 5mm further up front to get to 30%.
The wire is now glued with Loctite and fixed with 2 x 3mm blind nuts.

Should be solid enough... next flip will probably break the transom (although I also added some more ply...)

[Karfrik]

I believe you are gonna have to start taking flying lessons......Please take video of your next launch.....,....Albert

[CornelP]

You just tell Houston to be on standby....

[Karfrik]

Ok!!!...just don`t want to hear that famous phrase said by an astronaut in the Apollo 13 and i quote: "Houston...beep...we have a problem"......lol
Please take video..........we love videos.
By the way,go to RCG and see my latest on my CenGT 775!!!,........Albert

[Jeff Wohlt]

Your ESC cooling set up is excellent. With tubes directly on the fets you are cooling much better than plates with water tubes on the edges. You may want to shrink wrap it to keep those tubes in place...unless you epoxied them on there. Is that a plate you made for the cooling tubes?

To me you can't do a better job of cooling and that is what I will be doing with some lower amp ESCs with single layers of fets.

I wonder if you could run the tubes longer to also cool the caps on the front of the ESC...they get hot and are usually the first to go.
Nice work...I love 6S set ups. Plenty of go-go juice.

[CornelP]

The cooler is actually made of two layers of copper sheet. The top one was hammered into shape, then the tubes were soldered on the ends. The whole cooler is soldered...
I will try a set of 6 x 1000mF extra caps, with a watercooler around them, will post pics when it is ready.

[CornelP]

Excellent day out! The cat was superb, I need to go to a bigger pond... We had no radar gun today, but a couple of pairs of trained uncalibrated eyes estimated it around 80kph... and I was not able to go full throttle.
Just two problems: I connected the steering with 1.5mm steel wire and it was wobbly, I have to go back to the 2mm and get a stronger servo... or reduce the rudder size. The second one was... the wire snapped on my last run. I was afraid I donated another prop to the pond gods... but it was just the wire, easy to replace.

http://www.youtube.com/watch?v=0z7ApjNxZbw

The fast runs are not on this video... my son was sleeping on the job... next time no mp3 on the pond.

[norbique]

Hi Cornel!
What do you think why did your wire snap? Did you tun across something floating in the water?! how many cells in series did you use in the last video? And did you fit the new caps on the ESC?

[CornelP]

Well, the wire probably snapped because with the new strut the angle is a bit steeper... I should have changed the position of the tubing going through the hull. All it needs is a bit of heat on the epoxi.
I ran it on 6S, standard, the new caps were not ready... untested yet.
I need a bigger pond, to be able to reach full throttle and stay there for more than 1sec........

[CornelP]

Just because the rudder was a bit wobbly, I decided to redo the hinge... and came up with this! It should be more than enough...

[norbique]

I don't get it