Please help me tune my Cat

[de-pro]

This is my first Cat which I recently bought from Ben at Fightercat. The hull is a Rivercat and the electronics consist of a Leopard 4082 1550kv and a Turnigy 180A ESC. Batteries are a pair of Gens Ace 3s 5000 40c.
Basically this video shows her maiden voyage and I tried to keep the location of the batteries and the height of the strut at a neutral position.
You see quite a few speed runs in the video, what you dont see is quite a few flip overs
I would appreciate any advice you may have to keep the boat from flipping over on WOT. I basically ran most of the speed runs at 3/4 throttle. The boat is fairly nimble but seems a tad light on the front. Quite a few whillies if I am not watching my throttle finger. I know this boat is capable of doing much more, but keeping the boat planted at WOT runs seem to be a challenge for me.
The batteries are sitting at as you see in the attached photo (CG is approximately 25cm in from the transome) and the the strut height is roughly at +2 or 3 deg.
I am guessing the first thing to try is moving the batteries forward? how about adjusting the strut further downwards.
your comments will be appreciated

FighterCat final 003.jpg

[jamespl]

Try moving the strut down. On my genesis i have it so the angle of the prop is level with the bottom of the boat and the batteries about 2 inches more forward than you have them. This keeps her pretty stable at full throttle.

[jamespl]

Hope this gives you a better idea.



---
I am here: http://tapatalk.com/map.php?ytswrp

[de-pro]

moving the battery 2" forward will be a bit of challenge on the ESC side. please keep in mind the Genesis is 5" longer but I would certainly try moving the battery forward.
I have the picture with the strut height. Its about 29mm from the top of the drivedog to the bottom of the bracket right now. It was around 4-5mm higher during the speed runs.

Strut height.jpg

[keithbradley]

Set the boat on a counter top with the prop hanging off the end. Push on the front of the hull until it sits flat on the sponsons (the rear of the sponsons will raise off the counter). In this position, set the angle of the strut at zero.
Then, move the batteries forward a bit. They do not have to be even, you can move one side up to the ESC and move the other further forward.
If the boat starts running "wet", move then back a bit.

[de-pro]

Thanks Keith, I will try that. I assume always start the strut angle at zero and play with the battery placement?
when do you need to go positive angle on the strut?

[lenny]

That was not a blow over, The transit was coming out of the water at the last speed run.
It started to prop walk at 5.44 to the left and spun out.
I think all cat like to run at neutral.

[de-pro]

sorry lenny, I went frame by frame but couldnt see the transition. It sure wasnt a blow over. the boat dipped in the water at the last seconds and started spinning out and eventually capsized.

[Alexgar]

i run my apparition cc1515 t180 and m545 i put my cat on my kitchen table and lay the strut flat and level to the surface im not sure of your speeds but im getting high 50s

[JonD]

That was not a blow over, The transit was coming out of the water at the last speed run.
It started to prop walk at 5.44 to the left and spun out.
I think all cat like to run at neutral.

I'm still learning some of the terminology. Please bare with me. Could someone please explain what " a blow over" is, and what prop walk is i.e cause and effect.

De-pro, I'm running a Genesis (which I guess is somewhat similar) with the same 4082 1550KV motor, T180 and 6S set up as you. For what it's worth (and I'm fairly new to all of this), I have found good maximum speed stability (60 mph) with the strut level, or slightly "prop down" at the rear (do you call this positive or negative angle ? )

Also I have my CG fairly forward i.e. 0.33 which seems to be pretty much to the forward end of the recommended range that I have seen posted on this forum. Not that that figure would necessarily apply in your case, but it would seem to me that a forward CG is a safer bet than rearward, to start with

Jon

[Fluid]

I run my Skunkworks cat (splash of the RiverCat) in the high 80s through the time traps without blowing over....very often. Your boat is propped to run in the high 50s. IME this hull does not want the CG too far forward, nor does it like the strut flat on the table. When mine was set up that way it would not exceed 60 mph and it plowed heavily. First, I'd set the strut 1/8" above the table and flat. Use a 1/8" thick piece of wood to set it. Use a 3/16" gap between the drive dog and the end of the strut. Toss the teflon washer. Set the CG between 8.75" and 9" ahead of the sponson transoms. If you cut the rudder shorter, that was a mistake as a longer rudder will help prevent spin outs and hooking.

Your power setup is designed to run at full throttle. Running extensively at part throttle is very hard on the ESC and it will eventually give out. You can go to an x442 prop to keep the speed down at full open. Another option is to use a different prop design - I used Prather props on my record runs with this hull. A Prather 220 or 225 may work better than the Octura. Roll into the throttle over a period of 2-3 seconds from start to WOT. See if these changes work, if not report back and we'll try something else. These hulls tend to warp after they come out of the mold and that effects their running characteristics. No two will use exactly the same setup.


.

[de-pro]

Great info . Thanks Fluid.
My CG is currently set at around 10". I will use the 1/8" height from the bottom of sponson to adjust the strut. Will toss the teflon washer and I always have a good gap in behind the drive dog. Didnt touch the rudder except drilled the water intake holes bigger. This is a 110mm rudder. I figured the boat has another 5-10 mph when hit the WOT. Would an X series prop be of any help or stick with M. I have a 42x55 or x642 I can try. My goal was to hit 60 with this boat. certainly will need lots of learning before coming close to your max numbers.

I run my Skunkworks cat (splash of the RiverCat) in the high 80s through the time traps without blowing over....very often. Your boat is propped to run in the high 50s. IME this hull does not want the CG too far forward, nor does it like the strut flat on the table. When mine was set up that way it would not exceed 60 mph and it plowed heavily. First, I'd set the strut 1/8" above the table and flat. Use a 1/8" thick piece of wood to set it. Use a 3/16" gap between the drive dog and the end of the strut. Toss the teflon washer. Set the CG between 8.75" and 9" ahead of the sponson transoms. If you cut the rudder shorter, that was a mistake as a longer rudder will help prevent spin outs and hooking.

Your power setup is designed to run at full throttle. Running extensively at part throttle is very hard on the ESC and it will eventually give out. You can go to an x442 prop to keep the speed down at full open. Another option is to use a different prop design - I used Prather props on my record runs with this hull. A Prather 220 or 225 may work better than the Octura. Roll into the throttle over a period of 2-3 seconds from start to WOT. See if these changes work, if not report back and we'll try something else. These hulls tend to warp after they come out of the mold and that effects their running characteristics. No two will use exactly the same setup.


.

[keithbradley]

Thanks Keith, I will try that. I assume always start the strut angle at zero and play with the battery placement?
when do you need to go positive angle on the strut?

That's what I do. Honestly I can't think of a time I needed to go positive on strut angle, unless it was on a boat that wasn't built correctly or at speeds higher than the hull is meant for. Most of the cats I have ran do best with a neutral setting, and then strut hight can be adjusted from there. I can't remember exactly where my strut was set, but I think mine was just a bit "off the table" too, as fluid said his was. My cat only ran 60 so it wasn't quite as critical, but it ran well at that speed.
Also, if you're running a gap at the drive dog, I assume you have one piece flex shafts, right?

[Alexgar]

Thanks for the advice fluid I'll raise my strut a little (1/8) and see if I can get more speed a cc1515 on an m545 I thought would get better speed since my df29 is as fast with less resistance but the m prop keeps the boat pretty balanced , should I 5s it?

[Make-a-Wake]

That was not a blow over, The transit was coming out of the water at the last speed run.
It started to prop walk at 5.44 to the left and spun out.
I think all cat like to run at neutral.

Yep, spinout

.......sideways...............................then backwards