f3d

Hallo Speedfreaks,

hier some pictures from my new speedmodell for the German Speedcup in 3 weeks in the class 3 up to 15 ccm.

Two MB FI engines with fat pipes will give the 2,25 kg speedmodell power for more than 400km/h.

The same modell with 1 engine and 1 fuselage and same wing did with 1 MB FI engine close to 400km/ in the class 1 up to 6,5 ccm.

We will see what das speed trab will say

Best regards Michael

soarrich

My Feedback: (98)

What is the reason for the reversed NACA duct?

f3d

The Naca duct is the outlet for the very hot air from the bagside of the engine , exhaust stack, The hottest part of the engine.

I have made a lot of different tests to find out the best colling system for a speed engine and what you see is far the best.

1. The head of the engine is in the cooling air and the ramp behind creates a underpressure for the NACA duct. Very effective sugtion.

Left and right you see inlets for the pipe colling.

Engine colling and pipe colling are separetet.

Works very well under all weather conditions.

Best regards Michael

soarrich

My Feedback: (98)

Michael
Very well thought out, except the reversed NACA duct, it's not helping.
Do you post videos of the speed trials?
Good Luck on that 400Km/h, that's about twice as fast as I've ever flown![sm=thumbup.gif][sm=thumbup.gif]

vicman

My Feedback: (10)

Very cool!

f3d

Hallo Rich,

the reversed NACA outlet is only a optical benefid but working as well as normal opening. I understand your information about the working function of the NACA inlets and the benefits but here it is not a matter its only nice looking.

But thank you for this information.

Best regards Michael

spykster

What a handful, have you flown it yet? How do you launch it?

Great job, love the finish.

Good luck.

Kmot

My Feedback: (24)

That airplane is gorgeous!!

I can't wait to see it and HEAR it on video!

Good luck with your speed attempt and I hope you bust through the 400 KMH barrier!

HighPlains

My Feedback: (1)

This may be the first model ever posted in this forum that meets the definition of "Extreme Speed". Wicked looking design.

bob27s

My Feedback: (19)

Sexy machine .......

Looking forward to seeing flight results

Traditionally, twins end up slower than single engine when it comes to prop driven. Fuselage create far more drag than most people realized.

But........ this is going to be fast in any case... [&:][&:]

wyo69cowboy

My Feedback: (2)

Looks very cool! I don't know how you guys can see these little planes moving that fast, especially in colors like that lol. It would be a pile of splinters before I knew which way was up...

HighPlains

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If the wing is 30% of the drag normally.....it might less than 20% with this design.

f3d

Hallo highplains,

I can´t follow your calculation.

The airframe is the same as it is with 1 MB Profi pylon engine. Now I add 1 fuselage and 1 x6,5ccm MB Profi pylon engine. OK a little more track with one more fuselage but dubble power. All the rest, wing, stab .. is the same.

With 1 engine the modell did 390 km/h ( 240mph) and I think now it will do 253 mph.

Best regards Michael

HighPlains

My Feedback: (1)

The one minute calculation:

30% of the drag is due to wing, therefore 70% of the drag is from everything else.

Double everything else, so you still have 30 + 70 + another 70, now equals 170%

30 divided by 170 is now 17.6% of total. Rounded up to less than 20% of total drag is wing.

It should go like hell, but with perhaps 70% more drag than the single engine version but 100% more power, who knows.

Regardless, it is a cool looking bird, and I wish I could see it fly in person.

BiggerDanno

Looks like it's doing 200 mph sitting still!!

daven

My Feedback: (1)

Very nice, well done.

hotrodblazer

I would love to HEAR it in person!!

cncswiss1

I am in awe! so cool.. should be a hoot to fly, and sound AWESOME..

HighPlains

My Feedback: (1)

Michael, I think your estimate is pretty much spot on.

If you could double the power with the same drag, then your speed could increase to 302 mph.

But if the drag goes up by 70%, then the speed drops down into the 250 mph range with double the power.

However, there are several unknowns:

A substantial amount of the power comes from the potential energy of the altitude being turned into kinetic energy during the dive. Since you have a weight limit based on wing (and horizontal tail) area, that is not likely doubling. So the available power is not going to truly double over the single engine version.

Second unknown is will the engines perform as well due to vibration from one effecting the other.

Third unknown is will the closeness of the fuselages create higher drag due to mutual interference.

Forth and final question, will the props interact well so close together, especially the wake from each and their interaction.

Many known and unknown problems that you face with this design. I would really listen to it closely when you shut down the engines and are still at speed. Hopefully it will be very quiet.

f3d

Hallo highplains,

I agrree 100% with your all your points.

I see your are a speed expert.

In the near future with better weather I am waiting for I will make some flights.

But the motor sound on the ground with 2x 30000 rpm/m * is a concert.

Best regards

Michael

HighPlains

My Feedback: (1)

Michael,

All of us on this side of the pond hope it flies well and meets your goal. Please keep us informed and maybe a video or two without any music or noise so we can hear it go.

Good flying,
Bob

f3d

Hallo Bob and all speed freaks,

here a short video with the 15ccm speedmodell on the German speed championship.

The modell was the winner in the class 3 up to 15ccm with 240 mph on a 200m distance

Have fun.

http://www.youtube.com/watch?v=IUxu9QfYDFk

Best regards Michael

soarrich

My Feedback: (98)

Wow! Good job. [sm=thumbup.gif][sm=thumbup.gif]

I thought it would be hard to launch, but with that much power I guess it doesn't rely on the wing to climb away from the launch.

js3

My Feedback: (3)

A concert indeed!

Kmot

My Feedback: (24)

Gaawd!