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Old Nov 10, 2012, 07:15 AM
I am actually really slow
SlowBarless's Avatar
Brisbane
Joined Jun 2008
907 Posts
Nonsense?

Ask yourself, how fast do you reckon a F5B plane running a 6kw drive would get going if you could hold the power on for 15+ seconds. Then prop it appropriately, say an 18x28/30. Still sound like a nonsense idea? There's other ways to keep the tips subsonic then just adding more blades you know.

I don't have anything against what Marcus and Ralph are doing at all. I think it's awesome work and i wish i could do what they do. Just sharing an opinion.
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Old Nov 10, 2012, 07:26 AM
Inglish Nub
Tzeentech's Avatar
Joined May 2012
150 Posts
Not more then 300kmh because the wingprofile is not optimized for such high airspeeds , the torsion of the wings would make it uncontrollable and in the worst case the wing would explode. And your powersetup would be very fast but highly inefficient.. Anrammd these setups are highly efficient ask Ralph for diagrams of his Speed or Powercrocos..
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Old Nov 10, 2012, 07:30 AM
275mph club
M. Koch's Avatar
Regensburg, Germany
Joined Apr 2003
504 Posts
HI SlowBarless!
As Tzenntech said it, we need speed, no acceleration! You have to find the perfect mixture between acceleration and speed for every plane! Big props give us huge Amps-drawings which kill our cells, as we have 10s runs and not only 2-3s for a complete speedrun! If you have batteries for us which can deliver 450A for 10s and thats for about 5-6 Speedruns in one flight, iīll be pleased to try a 18x21 on my speeder but it will end with about 350km/h and not more, so really boooooorrrrriiiiing speeds ! Donīt forget, we are running much larger pitches up to 27 on our speed props at much higher rpm!
The maximum we run on competitions are 3-folded props, when we need the thrust, which 2-blade could not give us, but we try to avoid more than 2 blades as efficiency goes down, when itīs possible! The only thing we are playing with 4-, 5- or 8-bladed props is show and the amount of sound! Unfortunately itīs not like in the US or Australia and noise is a big problem! We have large restrictions on noise production for combustion engines here in Germany which are mostly 78db, excluding elektro! But if you have a 5x5 screamer at 45000 rpm which is much louder than that, a lot of clubs get problems with surrounding inhabitants and speed planes are not allowed to fly! So the only thing you can do is getting noise down, using such high-blade props or stop flying! What is better?: Loosing a few km/h speed due to less efficiency or complete stop flying such planes and do some F3A, F3K or gliders !
These props are more for Hotliner style flying as they are producing a lot of thrust! Ralph has broken the 100 m/s vertical averaged for 2 s (about 98m/s averaged for 4s) about one year ago i think with the Chimera, so much more than the best F5B-ship is doing at the moment and this not only for 2s runs but for much longer times, if you have good eyes ! So they are perfect for fun-flying and very silent speedtrainig on every club even with noise restrictions, thats all!

@ SlowBarless
Yes an F5B ship could get much faster than 350 km/h but not much faster than 400-420, when its special biult for it without 4 flaps and thats the end! You never could build an F5B ship FAI legal as sturdy as you need it above 420 km/h! Donīt ask me how i know! Even our special modified F5B ships found their end at these speeds as torsion is to much for these high aspect ratio thin wings! The plane is still flying but isnīt going in the direction you want to fly! Not really funny for the pilot i can tell you! Kai Koppenburg, Erwin Schamburger, myself and a few others learned this lesson about 3 years ago and started then building special F3S-designed planes! The first real F3S designed plane was Michael Jakobs Eagle, for which i built the molds and planes in 2007! All others started about 1-2 years later!

Ciao, Marcus
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Old Nov 10, 2012, 07:50 AM
I am actually really slow
SlowBarless's Avatar
Brisbane
Joined Jun 2008
907 Posts
The F5B thing was just as an example. I was really refering to their drives and powersetups not the model itself. Just wanted to point out that props of that size are certainly capable of going fast and if done correctly would provide more then just acceleration.

I was just suggesting a possible alternative to running more then 2 blades. As you said Marcus, efficiency goes down the more blades you add.

Considering the trend lately for large folding props in F5D. If anything they are quicker, quieter and more capable then the tiny props.

But as you said Marcus, its all about finding the perfect mixture.
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Old Nov 10, 2012, 11:12 AM
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Mreyello's Avatar
Deutschland, RP, Niederzissen
Joined Dec 2011
806 Posts
My persomnal experience:

F5d plane, about 1 kw input at level flight:
4,5x4,1
4,7x4,7
5,25x6,25
6x10
7x11.2
11x22

all of them came out with about more or less the same speedlevel but sure with different motor Kv!!!

As in F5d, F5b, and F3speed propdiameters got bigger over the years and speed did obviously benefit, it should be alowed to ask the question:

Quote:
Have you guys thought about trying larger diameter blades? Something as large as an 18" could be worth experimenting with.?
Tzeentech, i think there is no reason to get rude and sure any question in this direction makes sense.
As SlowBarless designes and builds his own props , maybe he is just some steps ahead of you?

So whats wrong with a :

14x27
16x30
18x35
........to be continued....



Yello
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Last edited by Mreyello; Nov 10, 2012 at 11:35 AM.
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Old Nov 10, 2012, 01:19 PM
Inglish Nub
Tzeentech's Avatar
Joined May 2012
150 Posts
Show me a motor which can turn a 18x35 at reasonable RPM?

The tests of Ralph showed us if u want speed get a propeller close to the 8,5x23 if you want acceleration and high vertical mount a higer diameter + less pitch. Maybe im too stupid to read diagrams and watch videos?
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Old Nov 10, 2012, 01:33 PM
Aka: Tom Jenkins
ApexAero's Avatar
Palm Beach County, Fl.
Joined Aug 2008
4,266 Posts
Hello guys! I have a question on the viability of using an aeronaut 3 bladed yoke on a 4035? also to ask politetly whom may supply a 8mm shaft threaded onthe end nicely machined with a clip groove complete for a HK4035? possibly 3 or 4
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Old Nov 10, 2012, 01:33 PM
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Mreyello's Avatar
Deutschland, RP, Niederzissen
Joined Dec 2011
806 Posts
Quote:
The tests of Ralph showed us if u want speed get a propeller close to the 8,5x23 if you want acceleration and high vertical mount a higer diameter + less pitch. Maybe im too stupid to read diagrams and watch videos?




Ralf did it his way, and it is obviously a good way,but why do you think it is the only way?

Keep watching videos and diagrams, while otherones try to find other innovative solutions!


Yello
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Old Nov 10, 2012, 02:12 PM
Inglish Nub
Tzeentech's Avatar
Joined May 2012
150 Posts
Quote:
Originally Posted by ApexAero View Post
Hello guys! I have a question on the viability of using an aeronaut 3 bladed yoke on a 4035? also to ask politetly whom may supply a 8mm shaft threaded onthe end nicely machined with a clip groove complete for a HK4035? possibly 3 or 4
PM M.Koch he can help u I think.

Eyello because he can prove that it works as he says what can you or Slowbar show us?
Anothert thing that would be interesting would be the maximum level flight speed of one of your F5d ships. I want to show you that the LP1.1 is not a bulky duck
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Old Nov 10, 2012, 02:25 PM
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Deutschland, RP, Niederzissen
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Teentech,
slow down a little!

Yello
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Last edited by Mreyello; Nov 10, 2012 at 02:31 PM.
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Old Nov 10, 2012, 02:30 PM
I am actually really slow
SlowBarless's Avatar
Brisbane
Joined Jun 2008
907 Posts
Quote:
Originally Posted by Tzeentech View Post
Show me a motor which can turn a 18x35 at reasonable RPM?

The tests of Ralph showed us if u want speed get a propeller close to the 8,5x23 if you want acceleration and high vertical mount a higer diameter + less pitch. Maybe im too stupid to read diagrams and watch videos?


Looks like I'm going to have to try this one myself.

You say if I want acceleration I should use a large diameter lower pitch prop and yes you're right. BUT what if I use a large diameter, high pitch prop and turn it at a lower rpm?

Just some generalisations (very general)

1. I still achieve the same pitch speed as the small props at high RPM
2. I still achieve the same static thrust as the small props at high RPM
3. My prop is more efficient simply because it has a more surface area.
4. My prop is more efficient because it rotates slower. No chance of supersonic or transonic flow over the top half of the blade and definitely no chance of supersonic tips. (much more laminar flow)
5. My prop is more efficient because less of it is consumed by yoke area. (larger diameter prop with same yoke size)

Just trying to convince you that there's other ways to go fast.

I've been playing around with the idea of mounting a ducted fan on an F5D airframe as shrouded rotors can be considerably more efficient then a normal prop. I've even drawn up my own ducted fan rotors which I may end up getting moulds cut for.

Point is, this is an ever changing hobby and it never hurts to be open minded about new ideas

Ben
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Old Nov 10, 2012, 03:09 PM
Inglish Nub
Tzeentech's Avatar
Joined May 2012
150 Posts
Hi Ben!

I have to admit that I feel sorry for beeing rude at first. Sorry!
I'm not entirely sure if a bigger prop means much more drag in a steep-speederlike-flying-angle. The smaller props rotate so fast that that isn't a real problem but I don't know how this will behave with a much bigger prop.
Germans also played with the idea of EDF on speeders some time ago if you like to abuse google translator u can get some ideas from this thread:
http://www.rc-network.de/forum/showt...wellenleistung
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Old Nov 10, 2012, 05:26 PM
Carbon fiber is our friend
Steve C's Avatar
United States, CA, Lodi
Joined Feb 2001
4,093 Posts
I'm not sure where you get .63 mach as a limit for tip speeds. Plenty of props are up above .80 with good efficiency. Just make sure it has the correct airfoil (no clark Y) and it's okay. It's still tough to beat the CAM 5x5 in an F5D ship after all and we run those tip speeds way up there. There's a great book by Stuart Sherlock of Supercool props and he covers this.

Steve C
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Old Nov 10, 2012, 06:05 PM
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Canada, SK, Prince Albert
Joined Jan 2006
1,258 Posts
Big Mega on 7S

Well if there was any doubt that an Ice Lite 200 can take 7S I put that to rest today

Hooked the Mega 22/60/1E up to the test stand today with my modified Ice Lite 200 (sinks and fan, no fan today though). I got a cheap Zippy 7S 3300 35C just for testing and it finally came in the mail after nearly 4 weeks

As you can see from the video there was no fire and the ESC and Motor were fine but the battery started to get hot which is expected for a 35C. During the test the voltage cutoff kicked in as the battery was really struggling with 250+ amps static but I was surprized at how well it held up to the pounding.
This setup produced 5.5KW of power with Downunder's 7x10 folders.

I am convinced that 7S will get the Monster near to or to 400kph (250MPH).

7S Ice Lite 200 test (1 min 11 sec)
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Old Nov 11, 2012, 05:51 AM
Inglish Nub
Tzeentech's Avatar
Joined May 2012
150 Posts
Quote:
Originally Posted by Mreyello View Post
Teentech,
slow down a little!

Yello
TZeentech but i know how it's meant. Time will show who should slow down..
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