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Old Dec 06, 2012, 01:14 PM
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New Zealand, Bay Of Plenty, Omokoroa
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Yip cool,i knew DUP was making some props,i did'nt realize they where available to us...if we ask nicely
I'm worse than a women at changing my mind on what to run,have narrowed it down to x3 dif systems thou.I'm not looking to excel at any one thing...but i do want to be able to go to a speed event and be semi compeitive,also run it at our open class,fun pylon days and also go to local flying fields and scare the crap/give all the old boys a buzz ( a hoon machine)
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Old Dec 06, 2012, 01:29 PM
2012 NZ Speedcup - 231 MPH
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New Zealand, Tasman, Richmond
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Yup, I'm making props. I'm going slow though. If you feel your order is taking too long, hassle me!! I need a good boot up the you-know-what every know and then
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Old Dec 06, 2012, 01:51 PM
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Excellent,cheers bro...what sizes are you currently making? I think i read somewhere you where doing 6x9,7x10's...
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Old Dec 06, 2012, 02:01 PM
2012 NZ Speedcup - 231 MPH
DownUnderPilot's Avatar
New Zealand, Tasman, Richmond
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I'm making 7x10 6x10 and 4.7x6.1 - all folders - although the 4.7x6.1 is in testing at the moment - the moulds are made and I can make the props, I just wanted to get that one tested first.
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Old Dec 06, 2012, 02:03 PM
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Hi all,

Those of you trying to reach max speed possible should carry as much battery as possible.
Design your system without forgetting about that.

Power comes from battery.

Random numbers (even though these will not fit in this airframe) :
Assuming all from same manufacturer and same "C" rating.

4S-5000 , 5S-4000 , 6S-3300, 11S-1500

4X5=20
5X4=20
6X3.3=about 20
11X1.5=16.5

First 3 packs can provide the same power (W) while under similar stress (per cell voltage) , but the 4th pack will be weaker.
Cube root (20/16.5) = 1.066
So first 3 packs can potentially reach 6.6% higher speed compared to the 4th.

In hot liners people draw 200+ AMPs from 2200 mAH cells for couple of seconds.
For top speed runs you'll need longer throttle use.
Think about the per cell voltage you can maintain near the end of your speed passes.

Get good quality, high C rated cells.... Carry lots of battery!!!!
Series, parallel .......what ever it takes.

-------

It is interesting to see the various setups being designed for top speed runs.


Good luck to you all,

Gryphon
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Old Dec 06, 2012, 02:44 PM
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Gryphoon,

Your calculation in general is correct,but for F5d airframes there is actually a limit which for me is allready reached when i watch most of the setup here.
F5d-Planes have to be able to take and carry the batteries, high wingloads and big fuses encrease drag a lot, these planes are designed for 1kg,most of the people here already have 1100-1200g in their F5d planes and reach somewhere arround 220mph at 1500 W or even more.

Good competition F5d with energy limit and 1000W are able to score more than 200mph at 1kg(min weight by regulation) with 1500 5S and slim fuses,without regulation 1300w and 850g should be possible,i am confident that this is at the same speedlevel than the heavy stuff.

Be aware that no 200g Motor is able to take the hole energy of a 5S 4000 at high powerlevels,it will burn before battery is empty,waste heat capacity of the motor will limit poweranyway.
So the only advantage of big battery is the higher voltage (about 0,3-0,6V) which in my experience is not able to compensate the higher weight.

Regards
Yello
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Old Dec 06, 2012, 02:46 PM
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Quote:
Originally Posted by DownUnderPilot View Post
I'm making 7x10 6x10 and 4.7x6.1 - all folders - although the 4.7x6.1 is in testing at the moment - the moulds are made and I can make the props, I just wanted to get that one tested first.

is here any different in shape, and where the hole for the yoke is between the 6x10 and 7x10 ?

Im asking cause remember VooDoo said something about the 6x10 not folding out as much as the 7x10, ??
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Old Dec 06, 2012, 02:51 PM
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Yip i definitly hear where you're coming frm Gryphon for speed...
Sometimes thou less is mre-when you carry larger and larger packs with mre cells you need a larger dia prop to pull that weight alng at high speed,which means bigger motor (mre weight) to turn that prop,which means mre amps which means bigger batts so in effect your constantly chasing your tail so to speak...
I think the prop is the most important because thats the thing which translates the pwr to the ground or air in our case....Its like a top fuel drag car,you can haveall the power in the world but if you cant transfer it to the ground then your wasting your time..
A fine balance between the two,pwr to weight is the go-but yes you defintly need
the juice to keep that h.p cranking
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Old Dec 06, 2012, 02:51 PM
2012 NZ Speedcup - 231 MPH
DownUnderPilot's Avatar
New Zealand, Tasman, Richmond
Joined Mar 2006
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Yello this seems logical. In part this explains why the speedcup planes, although not F5d, have evolved bigger - because of the airframe limitations. Bigger batteries are good, so long as you have a motor/prop capable of using the extra potential power.

You end up with impractical wing loadings.

Also it's easier to see a larger plane of course....
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Old Dec 06, 2012, 02:55 PM
2012 NZ Speedcup - 231 MPH
DownUnderPilot's Avatar
New Zealand, Tasman, Richmond
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Quote:
Originally Posted by sebbe View Post
is here any different in shape, and where the hole for the yoke is between the 6x10 and 7x10 ?

Im asking cause remember VooDoo said something about the 6x10 not folding out as much as the 7x10, ??
Pretty much identical. It's possible the weight distribution is different, because the 6x10 is definitely a thinner blade. But if I put a 6x10 blade on a piece of pushrod wire and let it hang, it does so at the same angle as the 7x10. (about 5-10 from the vertical).
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Old Dec 06, 2012, 03:06 PM
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Quote:
Originally Posted by DownUnderPilot View Post
I'm making 7x10 6x10 and 4.7x6.1 - all folders - although the 4.7x6.1 is in testing at the moment - the moulds are made and I can make the props, I just wanted to get that one tested first.
DUP-the idea of a high performance 6x10 folder (no gearbox) definitly appeals to me,it opens up a new favourite pastime of mine...pwr off 1000ft dives..
hmmm a complete all rnd plane,speed,race,dive...thats what i want
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Old Dec 06, 2012, 03:33 PM
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Swt,thats one job done for today ...cut my motor choice combos frm 4 to 3(no fixed props)NICE! Thats a big acheivement for me cosidering its taken weeks of sore eyes and late nites starring in2 my phone! All gd thou..Rome was'nt built in aday and its gd times
Yip i'll be keen DUP,6x10's please...no rush thou bro,mayb rnd end of jan,but will let you know,cheers
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Old Dec 06, 2012, 03:51 PM
2012 NZ Speedcup - 231 MPH
DownUnderPilot's Avatar
New Zealand, Tasman, Richmond
Joined Mar 2006
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OK mate, I'll add you to the list. I'll contact you when they are ready.
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Old Dec 06, 2012, 04:10 PM
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My general comments were not for any classification, or point scoring.

The Swist, even though it can carry more battery than other similar size airframes, is still limited on how much it can carry.

So it should be maxed if after the very top speed possible without worrying that the pack weight is going to slow it down.
Not so sure if the Swist can carry enough battery to feed setups very far past 3-3.5KW.....The guys who run the fastest Swists would know better than me.

Ofcourse we should keep prop size and KV in mind.

.....also it is not just Watts; Given the high Watts, making sure that the chosen motor is running efficient during the few seconds needed to reach top speed.

Not enough people are mentioning their RPM that go hand in hand with their Watts.


Gryphon
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Old Dec 06, 2012, 04:12 PM
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Excellent-whats the root measurement? (where the prop bolts to the centre piece,is it like a standard size type thing)
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