Quantcast

How to make a propeller driven aircraft go really fast ?

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

Speedboat100

Well-Known Member
Joined
Nov 8, 2018
Messages
1,887
Location
Europe
Risen does 312 km/h at 90 hp.



That has large wingspan...in comparison.

140 K usd.

Power to weight 0.19 hp/kg.
 
Last edited:

Speedboat100

Well-Known Member
Joined
Nov 8, 2018
Messages
1,887
Location
Europe
Rv6ejguy now you’re just making me daydream about a 3/4 scale Tsunami for sport class...

It is almost possible with Mouse Merlin engine. Me-109 had 36 litre engine and Spitfire 28 litre.

FIGHTER_comp.jpg

Sweeping the wings and moving the wing forward and putting the gas into wings is the solution IMHO.

mini2r3fo.jpg
 
Last edited:

Riggerrob

Well-Known Member
Joined
Sep 9, 2014
Messages
1,761
Location
Canada
Yes, gently swept wings help increase critical Mach number.
Many sailplanes, Formula 1 and Sport Class competitors now fly Schumann wings with elliptically curved leading edges that are gently swept. Some have straight trailing edges, but full Schumann wings have trailing edges that are slightly swept with an elliptical curve. Need composites to build gentle curves that precisely.
 

Wild Bill

Well-Known Member
Joined
Dec 11, 2013
Messages
104
Location
Vidalia, GA
I dont think it's trivial to get 1000hp and make it survive continuous use. Maybe if you use 2 engines. I believe the Pond Racer would qualify for sport class. It was fast enough it you could get some more reliable power in it.
The last time I followed the sport racing class, there was a requirement for the aircraft to be kit built.
Looking at the rules I found online that appears to no longer be the case.
Don’t see anything prohibiting twins..
Just the 1000 cu in limitation.

The pond racer was a cool design. Seems like I remember remember some having the opinion that aerodynamic wise it wasn’t that great.
Considering it never made the power it was supposed to, it turned some respectable speeds though.
 

BJC

Well-Known Member
HBA Supporter
Joined
Oct 7, 2013
Messages
12,496
Location
97FL, Florida, USA
The pond racer was a cool design. Seems like I remember remember some having the opinion that aerodynamic wise it wasn’t that great.
Considering it never made the power it was supposed to, it turned some respectable speeds though.
It is difficult (some say impossible) to have two separate engines and support structures that don’s have more drag than a single engine configuration with an engine of the same total displacement.

The Pond Racer was just another oddball design by whats-his-name.


BJC
 

WonderousMountain

Well-Known Member
Joined
Apr 10, 2010
Messages
2,143
Location
Clatsop, Or
It is difficult (some say impossible) to have two separate engines and support structures that don’s have more drag than a single engine configuration with an engine of the same total displacement.
BJC
No doubt,
.8^3 = .512 | Call it half. but frontal area = .8^2 is .64 x 2 engines. (1.28)

So if they don't go inline, or give some other advance, you're at a 5-4
disadvantage from the drawing board. Another problem with the Pond Racer was it's kinda lazy streamlining. However, the twin is proven power.
 

Wild Bill

Well-Known Member
Joined
Dec 11, 2013
Messages
104
Location
Vidalia, GA
It is difficult (some say impossible) to have two separate engines and support structures that don’s have more drag than a single engine configuration with an engine of the same total displacement.

The Pond Racer was just another oddball design by whats-his-name.
BJC
Yeah, 3 fuselage structures relatively close together along with all the intersections with the wing and horizontal stab seem like a deal breaker at unlimited speeds.

I’ve always wondered how a highly modified F7F would compete with the other unlimiteds at Reno.
Tigercats that I know of have been raced in a more or less stock configuration.
What would one do with a couple of R-4350’s and every speed mod possible?
I bet it would be be fast.
But that would be a 10,000 hp airplane against 3500-5000 hp airplanes.
 

Steve C

Well-Known Member
Joined
Oct 6, 2008
Messages
161
Location
Lodi, CA
The Pond had only 2x 3 liter engines making probably 400hp each. They planned for 600hp, but had so many problems it never ran at full power. It hit 400 mph on course with that. It's good enough for sport class.

I had a 48lb model of the PR with relatively small motors in it. It still did over 180mph. The concern over intersection drag is way overblown. It's a fast shape and it also handled extremely well. I lost an engine on takeoff on the maiden flight. It was no problem.
 

mcrae0104

Well-Known Member
HBA Supporter
Log Member
Joined
Oct 27, 2009
Messages
3,647
It is difficult (some say impossible) to have two separate engines and support structures that don’s have more drag than a single engine configuration with an engine of the same total displacement.
While I agree with this, I suspect that one of the design drivers may have been that it is easier to divide that power between two props rather than one giant one, given a small-ish airframe. Just a guess.

I'm eager to see these LS-powered contenders Ross alluded to. There have been some other weird attempts in the past...

1601678924569.png1601678958380.png
 

Dan Thomas

Well-Known Member
Joined
Sep 17, 2008
Messages
5,650
While I agree with this, I suspect that one of the design drivers may have been that it is easier to divide that power between two props rather than one giant one, given a small-ish airframe. Just a guess.

I'm eager to see these LS-powered contenders Ross alluded to. There have been some other weird attempts in the past...

View attachment 102507View attachment 102509
Looks deadly. Wonder what it's L/D might be?
 

Steve C

Well-Known Member
Joined
Oct 6, 2008
Messages
161
Location
Lodi, CA
I'm not sure if the planes he made were ever intended to fly. May have been more of a mechanical art thing.
 

BBerson

Light Plane Philosopher
HBA Supporter
Joined
Dec 16, 2007
Messages
14,428
Location
Port Townsend WA
That co-axial thing makes no overall sense. Just put all 8 or more blades on one fan like every modern jet airliner.
 

Dan Thomas

Well-Known Member
Joined
Sep 17, 2008
Messages
5,650
That co-axial thing makes no overall sense. Just put all 8 or more blades on one fan like every modern jet airliner.
I could see why he did the coaxial thing: to eliminate torque roll on takeoff and climb. Those short wings would have a hard time with that.
 

BBerson

Light Plane Philosopher
HBA Supporter
Joined
Dec 16, 2007
Messages
14,428
Location
Port Townsend WA
I don't think torque is a big problem. We have RC models with enough thrust to hover vertically. The pilot hardly notices torque with a tiny bit of aileron.
 

rbarnes

Well-Known Member
Joined
Aug 28, 2015
Messages
384
Location
Texas
That co-axial thing makes no overall sense. Just put all 8 or more blades on one fan like every modern jet airliner.
To put all the blades on the same hub would require the power from the two engines to be merged in a complicated transmission somehow. This way he just has a drive shaft from each engine going to each hub
 
Top