Wagner24314

I flew one of these when i was a kid for about 15 years it had a OS 61 fx heli motor with tune pipe on it. It was a blast but my old man sold it 5 years ago since i wasnt flying it any more. Also ive check with aztec he's out of country is there any one else with kits. i really want another one to biuld as a electric i want to push it past 200 mph.

crankpin

My Feedback: (15)

WHAT ??? 200 mph, electric ? Here is one from my hangar, what's the plan ? Why doe's it have to be the 8 ?

Crank

Wagner24314

i found a maker of the kit. but im planning for motor is a Neu 1512-2Y 770 KV, 100Amp esc 6 cell 5Ah lipo with that system it should spin a 11x10 at 18K rpm the head of the engine is gone and pipe so you loose all the drag and the 61 glow at best was only 1100 watts to the prop and the motor is peak 3000 watts that is going in it. also plan to gear door the nose and mains. also will make glass hinge gap covers the P-8 is so clean and stable that with a few mods it will out run some of those turbines. only plane i have now flyable is my f9f with a kj-66

crankpin

My Feedback: (15)

Take a look at the P-7, no chin on the nose, unless you need that room.

Crank

stuntflyr

That airfoil is never going 200 mph. Especially with open wheel wells on the typical retracts. Try an old Formula 1 kit instead. Thin airfoil and streamlined gear.
Chris...

MMcConville

My Feedback: (4)

True. The Phoenix 8 or 7 airfoil is much too thick to hit 200mph.

crankpin

My Feedback: (15)

A stretched Norm Page Mach One may help, but this is not practical. Wagner, what is your budget for this project ?

Crank

Wagner24314

the one i flew not that many years ago would do 170mph with a 60 heli engine. 200 isnt that much faster

Taurus Flyer

Hallo Wagner24314

Did you measure that 170 mph, and if yes, how?
With that you can estimate the power needed for 200 mph

Cees

Wagner24314

radar gun both way up wind and down

Taurus Flyer

What would be the needed "more" power 170 mph to 200 mph? Ratio?

Cees

Wagner24314

im starting with a neu motor that will turn a 11X10 at 17000 rpm the .60 would only turn a 11x7 at 15500 rpm on a good day

drag of head and pipe will be gone the motor will have easy twice the Hp

Hokie Flyer

At least 40% more.  However, I have my doubts about 170 mph.  I think 110 to 120 is more realistic.


Rob

Taurus Flyer

Rob,

That was my thinking too, 38 % more, but 11 x 10 and 17000 is probably 259 km/h max is 161 mph (100 % prop efficiency!!)
I will do a double check!

edit, I did check my calculation, correct.
Prop eff never can be 100 % so Rob's values are more realistic.

Anybody else?


Cees

Taurus Flyer

Wagner24314

When our calculations are correct, we need at least about 54 % more power, (from 161 to 200), to reach 200 mph, can you make that?
The prop must have an efficiency of 100 % than!

Cees

Wagner24314

yea we are good

Hokie Flyer

I just did a quick back-of-the envelope calculation:

Thrust = Drag

Drag = 1/2(rho)V**2SCd - Fortran notation used to denote velocity squared

I assumed air density (rho), surface area (S), and Drag Coefficient (Cd) as constants and arrived at a ratio of (200 mph) squared divided by (170 mph) squared

I also assumed prop efficiency as a constant (probably not the case) and power to thrust curve is linear (a simplification) and came out with 1.38 as the ratio.  Simplified, but a starting point.


Rob

Hokie Flyer

Wagner,

The Phoenix 7 suggestion is a good one.  The airframe is readily available and is very well engineered.  You use a P-7 ARF as a proof-of-concept plane and see how it works out before installing it in a hard-to-find classic.

I am curious if you can hit 200,  Also, I did a quick check of your power numbers.  You might need a bigger ESC.  To get 3000 watts on 6S, you'll be pulling over 120 amps.  That assumes full charge and no voltage drpression from the load.

When you fly the E-Phoenix, please post the results.


Rob

Taurus Flyer

Rob,

You are correct,.

When I calculate the needed power it is 220 % more than the moter 11X10 at 17000 of this moment. ( with 70 % efficiency of the prop).
All fast calculations!

Cees

pitstop000

My Feedback: (26)

P-8’s are not hard to find, New glass parts are readily available.


I’ll be watching this thread with interest.

Like to see 200mph out of a P-8, and e-power to boot!

doxilia

My Feedback: (3)

Maybe the 170 mph was actually 170 kph... easy for the gun to just have been in metric mode.

What about reducing the airfoil thickness in the P7/P8 rather than going to an F1 design. Going with a P8 might actually make this easier to accomplish since the cores could be cut fresh. On the other hand a P7 fuse/tail kit could be bought and a new wing made. I would want a foam core wing if aiming to hit 200 mph - that's some serious speed. Full carbon veil treatment and heck, maybe even some square CF spars lining the sides of the retract wells. Full covers and paint of course.

What kind of C rating discharge are we talking about? I know there's a guy who setup a GP revolver (I believe) with 10s. It weighed a ton (10-11 lbs I think) but it moved out in a serious way. Unlimited vertical was an understatement - it just vanished. That guy had really good eyes (or perhaps the eye in hid mind).

Cool,

its been a while since I read anyone making an equation post using Fortran notation. I might have used v^2 notation. Actually this notation is something that applications such as Firefox understand. Ever try punching in 10^2 in the FF Google field? All kind of conversions can be done.

David.

MetallicaJunkie

where do you get those tires?

remmulp

My Feedback: (6)

Rob,

Back in the seventies Dr. Maynard Hill set a speed record while working at John Hopkins Applied Physics Lab. If memory serves me the speed record was in the 180s (believe MPH). Doing some searching I noticed an article referencing Dr.Hill on wattflyer, progressiveengineer, and RCU: <cite>www.rcuniverse.com/forum/fb.asp?m=2214160</cite> (cached). Remembering the story from then he made many attempts at getting the aircraft correct and the engine properly setup (glow, 10cc) and eventually was successful at setting the record. Much could be learned from his work should this progress beyond just a discussion.

Respectfully,

Mike Plummer

Taurus Flyer

MetallicaJunkie,

You write: where do you get those tires?

We could buy these tires (wheels) in the Netherlands but that could be a VERY long time ago.
Dimensions are 73 mm 2 13/16 on it (see picture) but there is no brandname.

Reason I did show the picture was, he did write:

the one i flew not that many years ago would do 170mph with a 60 heli engine. 200 isnt that much faster
"Would"? Does that mean he didn’t measure it.

I often measure and log the real airspeed and for that I know my highest speed ever was 245 km/h (152 mph) in a vertical down line, horizontal speed 195 km/h (122 mph), pumped Webra Speed 10 ccm with Sonex pipe and own design pattern airplane. That's why I think 200 mph you will not reach with that plane, but I am curious.

Cees

Taurus Flyer

remmulp ekim,

I always do put an "enter" behind such a link you did show

www.rcuniverse.com/forum/fb.asp?m=2214160


Cees