Need help with FC Cheetah handling issue!!!

[straitline]

Hello Fellow OSE RC mariners. I have a serious handling issue with my FC Cheetah. let me give you my setup. TP mtr 1600KV, Ice 240 ESC, on 8s (I like speed) and I have a 452 prop. The problem is prop walk, moving thru the water slow my boat travels strait as I increace throttle it begins to go to the right. Making a strait line blast I'm constantly steering left as the boat fights to go to the right and I can see the boat fighting both inputs and not going as fast as I know it will. Does anyone have any advise on how to reduce or stop this. I just want to go fast in a strait line? Any suggestion are welcome.

[properchopper]

1600KV X 4.0V (nominal) X 8S = 51,200rpm spinning a 452(!) (in a 34.25" hull). Since you said "any suggestion welcome" I'd suggest kevlar body armor

[Doby]

1600KV X 4.0V (nominal) X 8S = 51,200rpm spinning a 452(!) (in a 34.25" hull). Since you said "any suggestion welcome" I'd suggest kevlar body armor

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[straitline]

Hey Properchopper I was hoping you would give me some input. Am I getting ready to blow this thing up or can I savage something. Down in cells? Down on prop? I love this boat and want to get it in decent running order. Right now I have no heating issues and have been running 8s since I had the boat, but I did up the prop up to a 352 from a x447. Like I said any suggestions welcomed.

HELP!!!

[Fluid]

Hello Fellow OSE RC mariners. I have a serious handling issue with my FC Cheetah. let me give you my setup. TP mtr 1600KV, Ice 240 ESC, on 8s (I like speed) and I have a 452 prop. The problem is prop walk. I just want to go fast in a strait line? Any suggestion are welcome.

You may like speed, but your boat doesn't. Okay, why? First, post a few photos of the transom from the side and the back. We need to see your setup to diagnose it. The exact motor you have would be helpful too...

Second, in theory your motor and prop could propel the Cheetah into the mid-80s. The Cheetah has too much lift for that speed unless you have made a few modifications - it will fly off the water. That large prop is part of the problem too, the Cheetah is really a 32" cat and that is a large diameter prop for a hull that size. An m645 has the same pitch as the x452 but will give far less prop walk. It will also load the motor less so that you may be able to keep your electronics from gong BOOM.

Lurkers take note: this is an excellent example of why simply adding a lot of power to a boat to go make it go fast doesn't always work. Going fast requires a system: hull-motor-ESC-packs-driveline-setup-knowledge. Oh, add hard work too.


PS: don't blow it up, send it to me, I'll pay postage......

[straitline]

Fluid... I will post some pics tonight once I get home. Great advice I will change that prop to begin, I'm don't run races but I do play at the local lake never running this boat for any long length of time. About the motor its an older TP motor with no other markings on it at all. This boat was built by Keith Bradley originally. I purchased it for a guy who hardly ran the boat he ran it on 5s all the time. Again thanks.

[properchopper]

I need to openly admit that I'm not in a position to advise on your situation. Here's why. I built two Cheetah's. They are 4S2P 2000kv / 4S2P 2040 kv builds. Mine on 4S2P 2040kv gives me plenty of satisfaction running at (or close to) 60mph. It's one of only two boats I have that I just run for pure pleasure (the other being my FE Jersey Skiff which is a gigglefest all it's own). I can blast around on my Cheetah at 60"ish"mph for several minutes with no stress on the components. I could get it to go faster but like Jay commented, the hull will quite likely get airborne a good part of the time. The nice thing about the Cheetah hull is it's ability to not only go fairly fast but corner better than the ever-popular scale offshore style long/skinny hulls. Cats are tunnel hulls; tunnels pack air to lighten them up on the water as part of their design. More speed = more lift. Too much lift and they go skyward. The Cheetah is a bit of a widebody and packs a goodly amount of air. Some builders go twins with their Cheetahs and the additional weight of a second/motor/esc/drive help hold the boat down at higher speeds but have been known to plow at certain speeds just so you know.

If I had to hazard a guess (which I'm normally against doing) I'd follow Jay's advice and prop down. I'd also volt-down before the whole drive system lets go. Also, if you haven't already done it; a skeg strut.

[straitline]

Again Guys thanks for all the great advice. This weekend I will prop down and cell down for starters to try and get some act right out of this wild Cheetah.... I love my Cat and got to get it RIGHT!

[keithbradley]

If it's a boat that I built (I only built a couple single prop Cheetahs, per customer request), I can assure you that I didn't set it up to run with that combo (1600kv motor on 8s with x452).

To answer your question, there are ways to MITIGATE the issues you are having with the boat you currently have. Tony would know more about this than I would since he has far more experience with the single prop Cheetah than I do.


If you want to go fast in a straight line without prop walk, there is a solution:

-Get a different hull. The cheetah is a poor choice for straight-line speed in my opinion. I think it's possible to keep it on the water at high speed, but it's not very efficient at 75+mph. Tony's setup is a better setup for the Cheetah. They're great for carving up the lake and having fun or oval racing.

-Go with twins. With counter-rotating props you can say goodbye to the steering issues you're having.

For reference, I run boats in a similar RPM range with smaller diameter props at well over 100mph. I'm not sure how fast you're going with the cheetah, but my guess would be that you are putting a beating on your lipos and not going much faster than you would on 6s.

[straitline]

Thanks KBB... This is the Centsle$$ boat Builty by you and you did not set it up on 8s or a 452 prop. That was my doing. Now I just want the boat to run as good as possible. Not breaking any speed records but reasonably fast. I know its not the best hull..... But I just love the shape and cool lines!! Its one of the best looking cats out there. IMO..Im just trying to get it to run best as possible. This week end I will prop and cell down and try again to get some act right out of this boat. Thanks for your input and feel free to give more!