4s Cheetah prop options

[chipgibbs]

I recently finished a FighterCat Cheetah and have had it in the water once.
The build specs are: Leo 4082-2000kv, Seaking 180 and 4s2p .
I have run it with an m545 and am wondering what other props I should try.
I found no heat over 100 degrees after the maiden run.

Thanks for any advice


Chip

[Chilli]

What kind of speed did you get with the 545?

Even though temps are good. I would be very cautions going too much bigger in prop with the 180. I've got a 447 you can try for giggles.

[chipgibbs]

chilli,

I didn't have the GPS in the boat but, I'd estimate, about 45mph.
The Revolt has an 1800kv motor on 4s and this Cheetah has a 2000kv 4082. It should be faster. I just haven't had enough time in the water to get it sorted out.

I might find some water tomorrow for a run or two.

Chip

[properchopper]

Chip,

I built a Cheetah for a customer with the Leo 4082 2000KV and a T-180 run on Dinogy 4S2P 5000 65C/130C packs. With an Oct 447/3 he went 57mph on the GPS but the T-180 was 165 deg. We switched out to a CC 240 and temps calmed down even after 4 minutes.

My Cheetah with a Neu 1521 1.5D (1900KV) and a FCR 240A esc and the same packs and the X447/3 with no temp issues was near that speed by my estimate (I forgot the GPS) and next run I'm going to a 450/3 since I run that same setup in my 34"mono without issues.

I have the prop up @ 3/16" off the sponson bottoms and + 3 deg to lift the hull out under power. Love those full throttle wheelies !!!

Got bored yesterday (rained out) so added some tailfins

DSC03911.JPG

[chipgibbs]

Tony....I copied that build. Not ready to shell out more money for a new ESC.

Thanks for the response, I'll try the strut adjustment with the 447/3

Chip

[properchopper]

Here's how I have the strut adjusted for the 450/3 (447/3 in the picture). The higher the strut, as long as the blades get adequate bite, the less load on the motor/esc/batteries. You can, if you listen carefully, hear a properly venting prop.

DSC03914.JPG

[Chilli]

Here's is what a properly vented prop sounds like.............sorry, couldnt resist.

http://www.youtube.com/watch?v=xQF1aIC_xBA

[properchopper]

Here's is what a properly vented prop sounds like.............sorry, couldnt resist.

http://www.youtube.com/watch?v=xQF1aIC_xBA

And one more (Mike, this is for You, - hope you're not missing her anymore but still the NAMBA P-Ltd Offshore Record holder if it'll make you feel any better )

http://www.youtube.com/watch?v=dOPTQrj-0RM

[Chilli]

I'm missing her but no regrets on the sale to you. Glad your putting her to good use!!

[chipgibbs]

Yup, That's how I want this Cheetah to run.

[stadiumyamaha]

I've had great luck on a similar build with a x642. It's normally my go-to prop for a new 4s build. Jmo

[chipgibbs]

So I've been to the pond and clocked 47.2mph with the 447/3. Kind of a base line. Now to start making adjustments.

Chip

[chipgibbs]

Tony & Chilli

I just noticed that the rear ride pads on the Cheetah hull are off the table 1/16" when the other 4 are touching. In Tony's set up photo, you can't see this.

Should the strut adjustment be above the table? OR above the rear most sponsons?


Chip

[Chilli]

Hmmm. On my cats I want all the ride surfaces flat on the table. Some blueprinting might be in order. We'll see what Tony says.

[chipgibbs]

Ran it again this afternoon with strut raised a bit & a little positive angle. I also had the gps in it but, I flew it too fast and end overed. By the time I got the boat back,
30 min, The gps was off.....don't know why yet.

IMAG0864.jpg

Chip

[Chilli]

Go back to neutral angle, leave the strut high and give that a shot when you get a chance. The positive got the nose up a little too much. Try to only change one thing at a time. Gonna burn a few packs in my planes before the sun goes down.

[chipgibbs]

When I raised the strut, some positive feeds in. To set back to neutral I may have to trim the end of the stuffing tube.

Chip

[chipgibbs]

The CG3 Cheetah clocked a 55mph run today with an M450/3. Blew over a couple times, I need to extend the battery trays to get the CG forward bit. It's currently at about 28%.

Chip

[properchopper]

The CG3 Cheetah clocked a 55mph run today with an M450/3. Blew over a couple times, I need to extend the battery trays to get the CG forward bit. It's currently at about 28%.

Chip

Nice ! I'll be trying a 450/3 on mine tomorrow. CG is 9.5" from sponson end. I'll report.

[Chilli]

You're getting there Chip. Any change in handling with the strut raised??

[chipgibbs]

Well, the hull is aired out under speed but hooks hard when turning.

[Chilli]

I bet you are spinning out instead of hooking. Someone correct me if my terminology is wrong but hooking is when the inside sponson grabs the water too hard in the turn and thows the boat off balance resulting in a spin out or flip. You see this more often in outboard tunnels. I think your problem may be not having enough sponson in the water to hold the boat in the turn resulting the the rear of the boat breaking loose. A larger rudder can help in certain instances but I don't think it will in your case. Your learing the difference between tuning for top speed and handling. You'll have to find that happy medium between the two.

[chipgibbs]

It's more like the front tip of the sponson drops when power is reduced and the inside sponson digs in. It's not spinning the boat out but, just dragging the inside. The flips have been under full throttle straight line end overs.
I just finished the battery tray extensions so I can get the CG at 30%, This should help with the end-overs. For the turns, I either have to keep it pinned or do some hull truing as discussed in another thread.

Chip
New Image.jpg

[Chilli]

Well I stand corrected then. I've know of a particular outboard tunnel that behaves that way. You have to stay on the throttle in the turns or she will hook. Did you try any faster turns?

It's chilly out there today but no wind. I'd be running boats but have worked OT the last three weekends and am way behind on getting ready for Chirstmas. Got to burn a few packs flying at dusk yesterday though. Might do the same today.

[chipgibbs]

Where are you flying?

[Chilli]

I have a middle school accross the street from my community. I'm also a member of the Loudoun County Aeromodelers for when the soccer kids take over the fields during the spring and fall. Have you ever been to the LCAA field ???

[chipgibbs]

I haven't been to the Loudoun field. I've been flying sailplanes since '81. I do have an electric.
I usually fly at Manassas battlefield or our club field in Rockville, Md.

Chip

[Chilli]

I knew you did gliders but didnt know if you had any other planes. The Loudoun Field isnt too far away from you. I'll let you know next time I plan on going there. Looks like Carl is getting back into planes also. There are some guys that fly at Liberty Middle School just a few miles from our pond. I have a feeling we're going to be loading up boats and planes in the car next year. LOL

[chipgibbs]

I have flown at Liberty but, havent run into the other flyers.

[Chilli]

Chip, Here a few threads on RC groups that the Northern VA flyers hang out on. Half belong to clubs and the other half are gypsies that fly mostly park flyers. A bunch live in the Centreville area.

http://www.rcgroups.com/forums/showt...0979&page=1252


http://www.rcgroups.com/forums/showt...76098&page=823