Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

2008 German Speed Cup

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Old 09-28-2008, 10:10 PM
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jetdryvr
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Default 2008 German Speed Cup

I guess the 2008 German Speed Cup was this weekend.
Here's a link to the web site:
http://www.rc-network.de/forum/showthread.php?t=118568

Here is what some guy from bavaria concluded:
Hi,
Steve ,Stefan Penz , has set the first offical record with his Hayabusa .The speed was 394 km/h,247mph .This was on Saturday ,hope to see 400 on Sunday. Steve did one pas 404 km/h,253mph .No moore info of the other pilots.
The fastes IC powered plane was 328 km/h,205mph ,who need this nitro burner .
http://www.scorpionsystem.com/about...d_speed_record/ .
Here in Laucha ,Steve set now an FAI world record ,same speed 247 mph.

To use an outrunner is simple a question of the rules. 75g/dm say low motor weight to turn a big propdia with high pitch as the prop tip speed has to be under mach 1 and you need the biggest batterie you can fit in this formula.And the plane has to withstand all this stress so it is very strong in all parts,wing and tail have to be stiff.

If anyone has anymore info please post.
Thanks,
Erik
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Old 09-29-2008, 03:49 AM
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Default RE: 2008 German Speed Cup

cool,thanks for post
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Old 09-29-2008, 05:58 AM
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Default RE: 2008 German Speed Cup

If you use this link, the language is (sorta) translated...

http://babelfish.yahoo.com/translate...rUrl=Translate
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Old 09-29-2008, 07:05 AM
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Default RE: 2008 German Speed Cup

ORIGINAL: jetdryvr

The fastes IC powered plane was 328 km/h,205mph ,who need this nitro burner .
That is wrong

The fastest successful IC powered 2008 Speed Cup runs through the optically triggered speed trap of 200 m length were made by the 10 to 15 cc planes and exceeded 230 mph...

However, the 30 years old IC powered official FAI World Record of about 215 mph still has not been broken, because the 10 cc powered WC record compliant speed planes (75g/dm^2 max wing load) had to fight with too much engine related technical trouble this weekend.

As we can see setting a new IC powered WC according to the FAI rules is much more challenging. [8D] People prefering the less difficult route should go electrics…

Besides the absense of technical problems, in general at speeds over 240 mph
[ul][*] the visibility (plane size and colour) and[*] the pilot’s flying skill (smoothness of passing the 300 m horizontal distance at low altitude with a minium amount of flight attitude corrections)
[/ul]
is the key factor for success.
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Old 09-29-2008, 07:11 AM
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Default RE: 2008 German Speed Cup

ORIGINAL: jetdryvr
If anyone has anymore info please post.
Many both general and profound info, pics and vids to the German (EURO) Speed Cups can be found here:

[link=http://www.rcuniverse.com/forum/m_3740991/tm.htm]250 mph speed! - German SPEEDCUP 2006[/link]



We have to remember that for any correct FAI World Record and German Mastership flight the planes have to stay between 35 and 5 m of altitude already 100 meters before the 200 m speed trap (see sketch below).

In fact parallelly carried out speed measurements using the Stalker Pro radar gun within the 100 m sector right in front of the 200 m speed trap showed up to 50 mph more speed than the final speed trap speed result. [X(]

So if a plane achieves an averaged trapped speed of let's say 240 mph then the entry speed during the first 100 meters in front of the 200 m speed trap was about 290 mph. At the end of the 200 m speed trap however the actual speed recorded by the Stalker gun was only about 190 mph in this example.

Clearly this example shows the importance of the FAI type measuring rules, i.e. to measure time over distance being much more objective than the isolated punctual recording by a radar gun or by Doppler audio shift (for that all Dynamic Soaring speed results cannot be evaluated objectively – sad but true).

The official speed results 2008 will be online later today...




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Old 09-29-2008, 08:15 AM
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Default RE: 2008 German Speed Cup

So if a plane achieves an averaged trapped speed of let's say 240 mph then the entry speed during the first 100 meters in front of the 200 m speed trap was about 290 mph. At the end of the 200 m speed trap however the actual speed recorded by the Stalker gun was only about 190 mph in this example.
Precisely why an event that measures speed from a diving aircraft is meaningless. Scatology is what comes to mind.
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Old 09-29-2008, 08:18 AM
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Default RE: 2008 German Speed Cup

Precisely why an event that measures speed from a diving aircraft is meaningless. Scatology is what comes to mind.
Yeah, but it makes for a good hangout day and bragging rights to the lay pilot. Without having an elaborate trap like those guys have there isn't much alternative for the sport speed freak.
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Old 09-29-2008, 09:45 AM
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Default RE: 2008 German Speed Cup

More info especially about the electric speed planes:

http://www.rcgroups.com/forums/showthread.php?t=931068

http://www.rcgroups.com/forums/showp...2&postcount=27
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Old 09-29-2008, 01:58 PM
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Default RE: 2008 German Speed Cup

Hey I-Love-Jets ,
Are these planes all purpose built by their owners or are there other kits available?
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Old 09-29-2008, 02:07 PM
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Default RE: 2008 German Speed Cup

so what if it dives then levels out for speed. The dive is part of the speed
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Old 09-29-2008, 02:23 PM
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Default RE: 2008 German Speed Cup

ORIGINAL: ecoliburger

Are these planes all purpose built by their owners or are there other kits available?
Well, except for the trusty but bulky Speedcobra ( see your thread
[link=http://www.rcuniverse.com/forum/m_7985017/tm.htm]SPEED COBRA[/link] ), all other speed planes are purpose designed and built for this Speedcup event only.

It is obvious that the small amount of available basic kits are bought by people who already are registered for next years event.

It also must be noted that each airframe design and engine setup requires a matching carbon fiber propeller design.

For instance the flying wing type speedplanes powered by a [link=http://www.rcuniverse.com/forum/m_7954952/tm.htm]5-ports OPS RIRE engine[/link] do require a different prop size than their regular configurated rivals powered by the identical OPS engine.




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Old 09-29-2008, 02:33 PM
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Default RE: 2008 German Speed Cup

ORIGINAL: mk1spitfire

so what if it dives then levels out for speed. The dive is part of the speed
The dive is required to get the engines up to stage 2 resonance. Only after a dive the very high pitched props (up to 13" of pitch) are able to perform correctly.

The speed measurement itself only is applied to the 200 m horizontal sequence ( = speed trap). Even more objective would be a 300 or 400 m long horizontal speed trap but the FAI obviously prefered 200 m because of visibility and space limitations.
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Old 09-30-2008, 01:49 PM
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Default RE: 2008 German Speed Cup


ORIGINAL: I-Love-Jets

So if a plane achieves an averaged trapped speed of let's say 240 mph then the entry speed during the first 100 meters in front of the 200 m speed trap was about 290 mph. At the end of the 200 m speed trap however the actual speed recorded by the Stalker gun was only about 190 mph in this example.

Is this a hypothetical example, or are you saying that these planes would do 190 mph if flown straight and level with no diving?
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Old 09-30-2008, 06:28 PM
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Default RE: 2008 German Speed Cup

No this isn't a hypothetical example. – It mainly depends on the prop size and the available rpm & torque. So it is not only the airframe drag that slows down speed planes after the dive but the propeller and its circle in particular. [:@]

The more refined the aerodynamics of a certain airframe is (parasitic and induced drag reduction), the better that speed plane will sustain speed over horizontal distance.

And also the more efficiently these highly oversquared props will perform (non-stalling prop = efficient prop slip-stream)!

In case of such super low drag airframes and sophisticated speed prop designs the main problem is to keep the IC engine rpm within the wanted HP and torque peak.


For instance the actual F3D pylon planes are relatively slow compared to the 10 to 15 cc purpose built speed planes within the FAI 200 m speed trap.

Why? –
Although the mega-powerful MB .40 FAI pylon engines turn up to about 35000 rpm being much more than the OPS .60 VAE for instance, the pylon specific props used with the MBs do limit top speed rigorously. Because the MB .40 (or IR .40 FAI or Nelson .40 FAI) do represent ultra high-timed engines, they unfortunately cannot be used with the high prop pitches usually applied for potentially higher top speeds for the Speed Cup.

The electric motors on the other hand don’t have these lack-of-torque problems. For that we will see many new speed World Records within the F3S-F class (electric speed) in future.

The main problem within the F3S-F class perhaps will be visibility and pilot skill limits...



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Old 10-01-2008, 02:51 AM
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Default RE: 2008 German Speed Cup

Yea....The 190mph seems too slow for these planes straight and level......but I guess if you have it set up for the big dive then maybe the prop gets into its zone during the dive and falls out of its zone somewhere in the 200m section. It seems like you could do a lot of runs to figure out the ideal prop for this type of measurement.
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Old 10-01-2008, 10:52 AM
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Default RE: 2008 German Speed Cup

Finally the official Speedcup 2008 results are listed:

http://www.f3s-speedcup.de/ergebniss...sse_Laucha.pdf

Stefan Penz with his HAYABUSA set the new FAI world record of the F3S-F electric speed class:

394.3 kph (245 mph)





But also the flights of Dag Cammann-Walczak with his F3S-D 15 cc speed plane were remarkable. Achieving 383.2 kph (238.1 mph) while using an OS .91 VR-DF engine he was the fastest nitro-head this year.



Next year the electric boys expect breaking the 250 mph “barrier“ eventually.

The nitro guys don’t expect but hope to achieve the same, preferably with a FAI compliant F3S-C plane (10 cc + correct maximum wing load) to bust that 30 years old Russian FAI world record for IC powered speed planes.



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Old 10-01-2008, 01:22 PM
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Default RE: 2008 German Speed Cup


ORIGINAL: I-Love-Jets

And also the more efficiently these highly oversquared props
Sorry for the dumb question but , what makes more efficiently a oversquared prop ??? and also you mean on the tips or the complete blades ??? is because more total area on less diameter or is another thing ......... ???


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Old 10-01-2008, 04:43 PM
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Default RE: 2008 German Speed Cup

i could read I-L-J's posts all day long. please keep them coming. thx.

david
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Old 10-01-2008, 05:42 PM
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Default RE: 2008 German Speed Cup

ORIGINAL: SpeedBoy


what makes more efficiently a oversquared prop ??? and also you mean on the tips or the complete blades ??? is because more total area on less diameter or is another thing ......... ???
The prop choice for maximum speed is mainly determined by two variables:
[ul][*] the aerodynamic quality of the airframe[*] the available power (HP and torque peak rpm)
[/ul]


So let’s take the WESTON MAGNUM R airframe and engine combo as an example for prop selection:

According to Weston the Eurotec V1 engine - a modified Webra .50 - should be combined with the APC 8x8 or 8x9 sport prop for maximum top speed results. In fact these prop sizes do match the Magnum aerodynamic layout quite well. After all true 175 mph top speed is possible in stock configuration – not more!





But why should the MAGNUM owner not take the APC 7x10 prop for instance to gain more top speed?

Well, theoretically increasing prop pitch means increasing prop slip-stream velocity at same rpm. Theoretically the 8“ pitch of the 8x8 APC produce at least 175 mph thrust at estimated 23000 rpm (unloaded). So in this case the calculated slip-stream velocity corresponds perfectly with the real maximum flight speed of the Magnum. This "calculated versus real speed compliance" does apply for many square sized props such like 5x5, 6x6, 7x7 etc if the plane’s airframe is not too draggy.

But in case of the oversquared 7x10 prop size difficulties will occur such like
[ul][*] too much prop stall especially during take-off and during hard turns (the prop doesn’t “bite“)[*] insufficient static thrust[*] Magnum airframe drag kills prop efficiency[*] possible lack of engine torque to maintain the optimum engine and prop operating rpm
[/ul]


So this MAGNUM example shows how important the reduction of airframe drag is to effectively make use of highly oversquared prop pitches. If the MAGNUM airframe would feature
[ul][*] a sleeker and longer fuselage[*] FIRE or RIRE engine configuration[*] full engine and pipe cowling[*] a wing featuring much more aspect ratio and less sweep[*] a wing featuring a different airfoil[*] a non-flat sectioned elevator and tail fin[*] no canopy[/ul]
then the 7x10 prop size (e.g. the APC 7x10 as a continuous strand carbon fiber copy - a thicker prop hub diameter is a must!) could be used potentially leading to much higher top speeds than 175 mph with a .45 sized ducted fan engine (OPS .45 or OS .46 VX-DF) for instance.




Last not least the prop design itself is most important. There are factors like
[ul][*] prop pitch distribution per blade[*] airfoil type selection and distribution per blade[*] prop tip speeds that should be kept below transonic speeds[*] etc
[/ul]
For the Speed-Cup participants therefore a sophisticated propeller design is of major interest. It is obvious that each purpose built airframe design does require an individually matching prop design and size...
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Old 10-01-2008, 06:39 PM
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Default RE: 2008 German Speed Cup

Nice report.

Actually I believe westonuk sugest a 8x10 for maximum speed and the manifold not cut down a inch as if you were to use 8x8.

I've tried the 8x10 and its hard to launch with the static thrust. It is quick though.

I like the 9x7 for easy launching but not as much rpm as the 8x8

Heres a pic of someone elses magnum who tried to get the drag down further by enclosing his tuned pipe out of his ducted fan engine.

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Old 10-02-2008, 01:29 AM
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Default RE: 2008 German Speed Cup

Thanks for the answer I-L-J as interesting as always are you post .

Speaking about props and speed I want to know what do you think about 2 points .

*Reducing the airfoil of a prop. (as the pic below show ).
*Shortened 2" a prop .

I have reduced 1" on a prop but never 2" and I'm planning do that for a new project that I still work on it .

I have read that is a bad make either of this options , I have good results with modified props though and I really want to know your opinion about this .


The 2 first pics , show the difference between original leading edge and once reduced (10x10 APC) .
And the third show a factory 10x10 , a shortened 10x10 to 9x10 and a factory 9x10 .


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Old 10-02-2008, 05:39 AM
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Default RE: 2008 German Speed Cup

ORIGINAL: SpeedBoy

Speaking about props and speed I want to know what do you think about 2 points .

*Reducing the airfoil of a prop. (as the pic below show ).
*Shortened 2" a prop .
Well all of the grey plastic APC props (sport and competition D1 versions) can be nicely re-shaped (shortened + sanded).

But all APC props represent injection mold props (even the black APC props containing small length carbon fiber fabric). This type of prop is relatively cheap to mass produce.

The major disadvantage of all APC props is their blade thickness (except for the last approx. 20% of the outer blade section). This thickness is a contribution to torsional and tensile strength.

But that noticeable APC prop thickness is optimised numerically do achieve a very respectable aerodynamical performance in maybe 90% of all cases of sport speed flying (Magnum, Diamond Dust etc.).




So the question is:

Why should a sport speed pilot change the sophisticated APC sport prop design to make it worse potentially?

Worse does mean:
[ul][*] weaker (very early appearing white hair-line cracks due to over-stressing)[*] less efficient aerodynamic performance than stock
[/ul]
Reduction of APC blade thickness can potentially be paired with too much loss of structural strength.
For example German Speedcobra owners have tried to use the standard APC 10x10 prop in combination with a 15 cc ducted fan engine (OS .91 VR-DF, ROSSI R91, PICCO 90 DF etc). In order to avoid transonic tip speeds and to keep the rpm within the engine's torque peak they shortened the 10x10 to 9x10 and re-shaped the APC prop.

However, even the shortened APC 10x10 was too weak for the power of 15 cc ducted fan engines. The APC props often failed during flight but sometimes already during ground engine test runs with sudden blade throws. So the Speed Cobra pilots switched to a safe to operate carbon fiber copy of the APX 10x10, shortened to 9“ of diamenter. The cut tip ends had to be thinned and smoothened to preserve aerodynamic efficiency at one of the most important part of any speed prop.

That manual re-shaping process of the outer diameter prop section airfoil is kinda difficult. You have both to thin down the tip section and to modify the airfoil of the transition part between tip and the middle prop part. In consequence the manually altered airfoil section in most cases will harm prop performance! You have created a new airfoil that potentially is not well suited for speed...



So what to do?
Most of the sport speed projects such like Diamond Dust, Magnum or many of the German sport speed planes listed [link=http://www.rcuniverse.com/forum/m_7985017/tm.htm]HERE[/link] can and should be combined with stock non-modified props (APC, Zinger, Bolly etc). In most cases - due to the airframe drag and the available engine performance - sport speed projects simply do not require modified props! A modified prop in most cases will not gain any more top speed for sport speed projects. Safe your time and money for other, maybe non-sport speed projects instead ("real" speed projects ).


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Old 10-02-2008, 05:49 AM
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Default RE: 2008 German Speed Cup





However in case of purpose built speed planes such like the German super low drag designs mostly hand laid carbon fiber speed props have to be applied (because of the engine rpm). That CF material enables much thinner prop blades in general but also very precise prop tip shaping by sanding.

Anyway, the final speed prop design should be determined by the prop mold already. The finished propeller - after coming out of the hot (in-situ curing) mold – does not need to be shortened or thinned afterwards. And if molded correctly (identical amount of CF fiber and epoxy resin for both blades per mold) the prop is perfectly balanced already.

So the newest trend for the SpeedCup freaks is the computer aided calculated (using latest aerodynamics software) and CNC cut mold. Now prop efficiency won’t be negatively affected by the factor trial and error (sanding and re-shaping by visual judgement).










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Old 10-02-2008, 10:16 AM
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Default RE: 2008 German Speed Cup

I love jets, how do you balance your props? Or do they come out of your molds perfect!!???


I see people

1.Scrapping with a knife the trailing edge of the heavy blade.
2.Drilling holes into the back of the heavier blade.
3.Sanding the back of the heavier blade.
5.Expoxy solder to the heavy hub side, keeping tips light
6.Sanding the heavy blade tip shorter.


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Old 10-02-2008, 12:50 PM
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Default RE: 2008 German Speed Cup

Well the correct procedure to balance any speed prop is to carefully sand the upper side of the airfoil of the heavy blade evenly over the entire radius using a fine file. So we try to maintain the airfoil character as best as possible.

In case of sanding the lower side of a prop blade (often Clark-Y like flat) the prop pitch would be altered resulting in different angle of attacks between both blades...

The actual speed props over here feature different airfoil types per blade section. Also the pitch distribution varies from prop hub over blade middle section to prop tip.

The prop radius must be identical between both blades.
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