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Old Jan 25, 2012, 03:54 AM
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Big Ceres (and other heavyweight) prop set ups

We got a bit sidetracked in another thread talking about power for the heavyweight planes (my Big Ceres is 162oz, 4.6kg). Doing a traditional hand launch on a plane like this requires a large unstalled prop (or you are asking for a crash on launch).

I'm running:
Plane: Baudis Big Ceres
AUW: 162oz ~ 4.6kg
Motor 1512/1.5y/f/6.7
Prop: rfm 20x13 (straight spinner)
Battery: 10s 3300mah hyperion 35c
ESC: Castle Phoenix HV 140
Watts: ??? (coming soon)

The plane flies fantastic and "light" for the weight, though landings are a bit long. More prop diameter and pitch wouldn't hurt (it does slow down in a climb and while fast for it's size, it's not blistering by any means).

I believe RASA makes a 20x15 now, that may be interesting to try on these large set ups.
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Old Jan 25, 2012, 06:24 AM
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Good idea to arrange a thread for this so we dont mix up too much and doesnt get OT in another thread.

It will definitely be interesting to both test and to see whats out there in regards to props for larger planes like the B.C

My own BC is not arrived yet but is scheduled coming from Baudis in end of January, so I am excited to get my hands on that fine bird.

I still intend to use my F5B setup (1512/1.5D/6.7) with the GM 18 x 21 prop on 6s and 5s batteries. The virgin throw/flight i will use a very light battery in the 2600 class size just to have flown it and get the sense of how it behaves.
This setup is capable of approx 7KW, so with the proper ramp setting to avoid prop stall I truly believes it creates the thrust to lift off properly.

Nevertheless, I see the advantage of having larger props availability but hopefully there will be prps made with slightly larger pitch than the 20 x 13 typical.

regards

Řystein
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Old Jan 25, 2012, 07:44 AM
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Hi everybody, new thread for these beast are very wellcome hehe...
What's into my Big Ceres:

Motor: Hacker C50-13L/f/6.7 - 1870KV
Prop: GM 18x21 but moving back to RFM 20x13 (straight spinner)
Battery: Turnigy 8S 3000mah 40C - plannning move to 10s
ESC: Castle Phoenix ICE2 HV 120
Watts: 3000W
amps: 100

I did the mods suggested in old Big Ceres Thread, when the flap and aileron servos goes I put 2 layers of carbon and then boxed the servos, I put big horns for flaps as well, this mods stop the flutter problems I saw in the first few flights, now I can dive from the hell to the ground without fear the plane explode in air.
I used Hacker Motor just cause I have this one sitting here, I really like Neu motors too.

Question: Combatflier, I think your setup is around 5KW, do you use throttle on switch?

Cheers,
André
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Old Jan 25, 2012, 07:58 AM
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Do you posess the empty weight of the B.C ?
In any matter, I will weigh mine when it arrive and post here.

What lay up do you guys have ?

Mine is ordered as Strong version (160g Carbon layup) and RDS for the wings.
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Old Jan 25, 2012, 09:14 AM
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sorry, I didn't weight mine when empty.
my version is the standart one but seems really solid for what it's made for,
I think all versions are strong but need specific improvements as I sad before,
go for strong version if you want to DS this monster
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Old Jan 25, 2012, 10:44 AM
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Quote:
Originally Posted by combatflier View Post
We got a bit sidetracked in another thread talking about power for the heavyweight planes (my Big Ceres is 162oz, 4.6kg). Doing a traditional hand launch on a plane like this requires a large unstalled prop (or you are asking for a crash on launch).

I'm running:
Plane: Baudis Big Ceres
AUW: 162oz ~ 4.6kg
Motor 1512/1.5y/f/6.7
Prop: rfm 20x13 (straight spinner)
Battery: 10s 3300mah hyperion 35c
ESC: Castle Phoenix HV 140
Watts: ??? (coming soon)

The plane flies fantastic and "light" for the weight, though landings are a bit long. More prop diameter and pitch wouldn't hurt (it does slow down in a climb and while fast for it's size, it's not blistering by any means).

I believe RASA makes a 20x15 now, that may be interesting to try on these large set ups.
Are you running this setup now or is it what you are intending to fly?

With regards to another prop. May i suggest a 3 bladed 20x13 prop?

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Old Jan 25, 2012, 12:10 PM
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Quote:
Originally Posted by jjmouris View Post
With regards to another prop. May i suggest a 3 bladed 20x13 prop?

What specific brand are you suggesting ?

What about a GM 3 blade, would that be a good solution ? Would like to have some more pitch than the 20 x 13.
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Old Jan 25, 2012, 12:49 PM
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I do use throttle on a spring-loaded switch with all my planes. I think the plane was probably around 5kw when the batteries were fresh, but with time I would guess IR has increased, vdrop has increased, and the power is probably lower now (high 4's?). If the weather works in my favor this weekend I will put unilog on it and find out.

Joe, I'm already using this set up, I like it for the most part. To prevent controller burn out perhaps a 3 bladed 17x13 set up would be better? I believe my controller is already just about at its limit, bursts are a bit longer (4second range) on a plane this size as compared to a high powered F5B model. The power to weight ratio isn't even close.
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Old Jan 25, 2012, 01:13 PM
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I bet your HV140 can handle 180amps for your 4 seconds....
You can try new batteries 65C discharge, for sure it will give you more amps, watts, etc...
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Old Jan 25, 2012, 01:23 PM
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Well, i would suggest trying a 3 bladed prop in general. As long as bigger blades are not available this is a good option. More blades also gives much more blade area vs not to much more power. From adding 1 blade (2 to 3) you only get about 20% more power, not 50% as you might expect. This means more lifting area at the cost of only very little prop efficiency (3 vs 2 tip vortices). I really like the 3 bladed GM 18x23 prop i have here, it's been great trying it out in F5B and i plan to use it again soon. It would however be better suited to a bigger plane and this is what it eventually will get used for on my Viking. You could try a 3 bladed GM 18x21 or a 3 bladed Pils 17.5x17.5 if you can talk Georgi into making you one.

combatflier, my numbers in the calculator would suggest more then 5KW, more like 6KW peak but i would guess since the climb lasts longer where the power is much less, you are running lower power on average. I don't think your ESC is at it's limit at all, but then that is my oppion. Note that i did nearly 7KW with a P85HV, yours is much bigger.

In the end, i think you will need to use a combination of a serious outrunner (Scorpion) with a gearbox in those huge planes like the Big C to get a really big prop spinning on the nose. Custom designed and hand made prop.
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Old Jan 25, 2012, 01:40 PM
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I did actually send Georgi a PM a few days ago asking him for making me a 3 blade 18 x 21, but no feeback so far. Is it any other options to get in contact with him ?

Woudl the aeronaut 3 blade spinner Esprit have cope with high powers on a suitable blade (like a RFM blade) ?
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Old Jan 25, 2012, 01:51 PM
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Interesting, I would have thought the 3 bladed prop would pull a lot more juice. When you ran the 18x23 3x blade, how many watts did it pull and what was the prop RPM?
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Old Jan 25, 2012, 03:29 PM
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Quote:
Originally Posted by combatflier View Post
Interesting, I would have thought the 3 bladed prop would pull a lot more juice. When you ran the 18x23 3x blade, how many watts did it pull and what was the prop RPM?
No prop RPM, sorry.
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Old Jan 25, 2012, 03:49 PM
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Motor wind and cell count could get us a rough estimate, if you have that. I'm trying to determine how many amps I would be pulling on a 10s 1512/1.5y/6.7 set up with that prop. I'd imagine I would have to go down to 8s or 9s, but it may ultimately be worthwhile. I also have an ICE HV 160 (both a lite and regular version) that should come back from CC eventually...
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Old Jan 25, 2012, 03:59 PM
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This thread needs a video... Of course one by Martin
Big Ceres E - Summer Flying (5 min 34 sec)
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