Quantcast

10/23 Raptor Video

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

5761RF

Member
Joined
Nov 26, 2020
Messages
14
Flaps on the main wing will require flaps on the canard. The complexities and additional flight loads on the control systems and structures are probably pretty significant.
I believe it's safe to say Muller has no idea at all of the complexities involved in converting his throwaway statement into reality. He blithely speaks of the design change as if it is no more challenging than cobbling another heat exchanger on the aircraft, ignoring the fact that executing the same idea on the Starship overwhelmed Burt Rutan and Beechcraft while consuming a good portion of its billion dollar development costs.
 

berridos

Well-Known Member
Joined
Oct 10, 2009
Messages
1,117
Location
madrid
Dont know the effect of the prop stream, but having the cooling outlet right at the end of the fuselage were the perimeter of the fueselage is shortest, makes up for the highest pressure location. On top, as the outlet is at the prop root where minimal suction takes place i suspect that the prop stream doesnt help to reduce pressure. He needs to radically overthink the cooling configuration and get rid of criteria based on aestetics in order to make the cooling work.
Maybe an aestetically atractive location would be to place two cooling units at each armpit, right after the door and below the wing.
 

PPLOnly

Well-Known Member
Joined
Dec 12, 2020
Messages
69
I believe it's safe to say Muller has no idea at all of the complexities involved in converting his throwaway statement into reality. He blithely speaks of the design change as if it is no more challenging than cobbling another heat exchanger on the aircraft, ignoring the fact that executing the same idea on the Starship overwhelmed Burt Rutan and Beechcraft while consuming a good portion of its billion dollar development costs.
What do they know? They fitted an expensive and underpowered aircraft engine instead of a lightweight and efficient out of production car engine.
 

jandetlefsen

Active Member
HBA Supporter
Joined
Apr 9, 2020
Messages
36
Watched this video again after a long time. It seem like the bird climbs really slow. Can this be fixed in the current design? Seems like he added a lot of weight for the pressure cabin and other shenanigans.
 

rv6ejguy

Well-Known Member
Joined
Jun 26, 2012
Messages
4,080
Location
Calgary, Alberta, Canada
Watched this video again after a long time. It seem like the bird climbs really slow. Can this be fixed in the current design? Seems like he added a lot of weight for the pressure cabin and other shenanigans.
Not without losing 1200 pounds of weight and redesigning the cooling system completely, so I guess the answer is no, not with the current design.
 

wsimpso1

Super Moderator
Staff member
Log Member
Joined
Oct 18, 2003
Messages
7,650
Location
Saline Michigan
So, from earlier discussions in the old Raptor thread, I was under the impression that "cooling" could be achieved if the engine was set up properly, in particular the turbos. No?
Induction/Exhaust systems have two main problem areas: Inappropriate sizing and inadequate intercooling. The results are less power than expected from the fuel flow and higher temperatures than are wise on everything from the compressors through the combustion chamber and turbines. Then there is the interactive issue of intercoolers being part of managed air for cooling.

Cooling has two main problem areas: Poor air management and inappropriately sized heat exchangers. The result is having to trade performance against overheat risk. Then there is the interactive issue of heat exchangers being part of managed air for cooling.

The two issues are mostly independent, but share in the air management to do the cooling.

Billski
 

PPLOnly

Well-Known Member
Joined
Dec 12, 2020
Messages
69
New video, and the most efficient thing in his cooling system is the heater. I was surprised he’s still opening it as that is distorting his numbers and performance.
I’m really not clear on why his heater works so well to drop coolant temps...something really doesn’t seem right there.
 

231TC

Well-Known Member
Joined
Aug 29, 2020
Messages
104
Kind of ironic that he made such a big deal about needing air conditioning in the prototype, yet he has to turn the heat on to fly it.

He's still arguing there's no point to doing stalls. I'm still shaking my head.
 

Voidhawk9

Well-Known Member
HBA Supporter
Joined
Mar 26, 2012
Messages
462
Location
Timaru, NZ
I’m really not clear on why his heater works so well to drop coolant temps...something really doesn’t seem right there.
As I understand it, this also opens the big coolant tank in the nose, so he's flowing unheated coolant into the system, thus dropping the temps temporarily.
 

Vigilant1

Well-Known Member
Lifetime Supporter
Joined
Jan 24, 2011
Messages
5,760
Location
US
I just uploaded Part 2 of my vids on liquid cooling last night:

Maybe Peter could watch these and see how others have done it successfully.
Thanks, Ross, great video.
1) Some aspects of achieving low-drag liquid cooling may not be obvious
2) The above has been known, and solid approaches have already been researched and widely promulgated for at least 75 years. But, first a person needs to know that they might not know everything already.
 
Last edited:

rv6ejguy

Well-Known Member
Joined
Jun 26, 2012
Messages
4,080
Location
Calgary, Alberta, Canada
A lot of cooling research was done in the 1940s and forgotten by many with the introduction of jets but if you dig, it's available. Several NACA papers exist online.
However many people don't know or don't care about cooling drag and slap some dreadful things together, just as we see on Raptor. There are very few good examples of low drag liquid cooling on new aircraft which is why I made these 2 vids. Also very little applicable data on small aircraft radiator design available, period.
 

berridos

Well-Known Member
Joined
Oct 10, 2009
Messages
1,117
Location
madrid
Excellent video. So much condensed information. I am surprised the voodoo dismissed the boundary layer splitter. Why did you choose to keep it?
 

rv6ejguy

Well-Known Member
Joined
Jun 26, 2012
Messages
4,080
Location
Calgary, Alberta, Canada
Excellent video. So much condensed information. I am surprised the voodoo dismissed the boundary layer splitter. Why did you choose to keep it?
Frontal area is the killer at 480 knots... Voodoo is strictly a race/ record aircraft. 4000hp, heavily cooled with spray bars and ADI. Ingesting the boundary layer didn't seem to harm the speed of this aircraft. The builders know a lot more about this aspect than I do.

On my aircraft, the rad was placed against the belly skin so I had X frontal area to contend with. The inlet didn't need to be very big so the rest of the duct was just shaped for minimum drag.
 

wsimpso1

Super Moderator
Staff member
Log Member
Joined
Oct 18, 2003
Messages
7,650
Location
Saline Michigan
New video, and the most efficient thing in his cooling system is the heater. I was surprised he’s still opening it as that is distorting his numbers and performance.
I’m really not clear on why his heater works so well to drop coolant temps...something really doesn’t seem right there.
The heater is most likely thin enough to be able to drive significant air through it, and thus reject a significant dose of heat. It does seem to be rejecting as much or more heat than the base radiator and duct scheme.

Early on temperature vs time data was being shared, but flight conditions were constantly changing, so estimating delta T's and time constants were impossible to determine. Now thermal performance data is not being shared, so we are in the dark.

The coolant temperature drops we have seen have been largely a matter of having the heater loop cold, and suddenly opening the loop, so that dose of cold coolant is dumped on the system, giving a quick cool. After the heater loop has been on for a bit, temps do climb again.

Billski
 

wsimpso1

Super Moderator
Staff member
Log Member
Joined
Oct 18, 2003
Messages
7,650
Location
Saline Michigan
Excellent video. So much condensed information. I am surprised the voodoo dismissed the boundary layer splitter. Why did you choose to keep it?
Ross has also shared elsewhere with us that his splitter has another function, that of preventing the radiator duct from ingesting a plume of hot air coming out of the cowling and coming out of the exhaust pipe. Russell achieved that goal by having his cowling exit to one side of the airplane while the radiator is to the other side...
 

SuperSpinach

Active Member
Joined
Apr 20, 2020
Messages
39
Location
France
Thank you very much for those two videos ! I watched the first one and was waiting for the second to come out. They are both very interesting !
 

rv6ejguy

Well-Known Member
Joined
Jun 26, 2012
Messages
4,080
Location
Calgary, Alberta, Canada
Thanks guys. I see lots of people struggling with cooling auto engines. Hopefully these vids will lead them down a better path with less do-overs. I probably have 50+ hours into making these 2 vids so I hope some folks find them useful... I know I had very little to go on when I redid my setup.

I'm going to relax on the next few vids and do some easy ones.
 
Top