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02-19-2011, 05:38 PM
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Join Date: Feb 2011
Location: California City, CA
Posts: 18
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Thoughts on turbocharged Rockets?
I'm still very much in the dreaming stages of an aircraft project. The aircraft I really want is a Harmon Rocket II.
Here's my thinking:
I want cruise speeds as high as possible with fuel flows as low as possible (who doesn't?). We know the HR2 is redlined at 275 mph TAS. We can't go faster than that, but can we be more efficient?
You can pick up bits of efficiency here and there. You can use GAMI injectors and an engine analyzer to run lean of peak, lowering fuel flows. You can use electronic ignition to squeeze more power out of the engine by optimizing the timing. By carefully designing the cowling and cooling system, you can minimize drag there.
What I'd really like to build is a turbocharged Rocket. You can't fly faster than 275, but you can fly higher in the thinner air and, in theory at least, burn less fuel doing it.
So, are there any turbocharged HR2s out there, or is anyone working on a similar aircraft? Keep in mind I'm already aware of the disadvantages of cost and increased maintenance. I'm just curious to see what others with more experience might think of this idea.
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02-19-2011, 07:25 PM
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Senior Curmudgeon
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Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 15,420
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Welcome to VAF!!!!
Paul, welcome to VAF
Turbo'ed Rocket--------I like the way you think.
Good to have you here, enjoy the site.
__________________
Mike Starkey
VAF 909
Rv-10, N210LM.
Flying as of 12/4/2010
Phase 1 done, 2/4/2011 
Sold after 240+ wonderful hours of flight.
"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
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02-20-2011, 12:50 AM
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Join Date: Mar 2005
Location: Oxnard, CA
Posts: 65
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Wolfgang Meyn built a supercharged F1 Evo. I believe it was a Vortec Supercharger. N104RX. I think he sold it, but I can't remember who has it now.
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02-22-2011, 04:19 PM
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Join Date: Sep 2010
Location: Chesapeake VA 23320
Posts: 64
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Sure thing!!!
Thats what I am doing on mine, I want as many ponies as possible when needed.
TIO-540, nuff said.....
When I started racing cars I was told one thing by a great racer that was instructing me in order to get my profesional credentials, and that was:
"Always make sure you have more horsepower available to get you out of trouble than the horsepower you used to get you in to that trouble"
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02-22-2011, 07:18 PM
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Join Date: Jan 2011
Location: Ridgecrest, CA
Posts: 126
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Quote:
Originally Posted by DesertFlier
I'm still very much in the dreaming stages of an aircraft project. The aircraft I really want is a Harmon Rocket II.
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Hi neighbor...IYK here...
__________________
Dan Wright
Building RV-12 #511 in the Mojave desert (1976W reserved)
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02-22-2011, 08:30 PM
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Join Date: Feb 2011
Location: California City, CA
Posts: 18
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Thanks for all the greetings, folks!
I can't wait to get started on this. I've got the place to build it and I've got approval from my wife. I need to gather some tools and the plans and then I'll order the empennage kit.
My questions on the turbo:
How high do you need to go to benefit from turbocharging? Since the airframe is redlined at 275, we can use that as the one constant in a sea of variables. As you go higher and higher, the air gets thinner and you should need less and less power to get to 275.
However, there has to be a limit to this logic. My estimation is that at some point, the HR2's wing will be the limit. As you increase altitude, form drag decreases, yet so does lift. You have to keep increasing alpha to carry the same weight. At some point you'll reach the wing's optimum AoA, after which any increase in alpha will give you more drag than lift. But where does this happen? Hard to say, really.
Or...
The limit might be in the oxygen system. As I understand it, supplemental oxygen of the compressed gas type (as opposed to LOx) is only good to about 24,000 feet. After that it takes too much physical exertion to breathe and you'll start to suffer hypoxia. This might happen before you ever reach the aircraft's potential altitude.
Do you suppose it's better to turbo-normalize an engine or boost the heck out of it? With turbo-normalizing you're limited to approximately 300 horses. With boosting you can go much higher, with reduced engine life. The HR2 is already high on power-loading, even with a 260hp engine. I don't know if it's necessary to squeeze every last pony out of the engine. I'd just like to maintain that power up high.
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02-22-2011, 09:05 PM
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Join Date: Aug 2005
Location: Atlanta, GA
Posts: 4,219
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Quote:
Originally Posted by DesertFlier
Thanks for all the greetings, folks!
However, there has to be a limit to this logic. My estimation is that at some point, the HR2's wing will be the limit. As you increase altitude, form drag decreases, yet so does lift. You have to keep increasing alpha to carry the same weight. At some point you'll reach the wing's optimum AoA, after which any increase in alpha will give you more drag than lift. But where does this happen? Hard to say, really.
Or...
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"Or.." includes several potential gotchas including:
Mach tuck.
Flutter.
__________________
Kyle Boatright
Marietta, GA
2001 RV-6 N46KB
2019(?) RV-10
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02-22-2011, 09:50 PM
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Join Date: Jul 2009
Location: Ankeny, IA
Posts: 210
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My best guess
Some practical limits I can think of, in no particular order:
1) Decreasing true airspeed redline with altitude. Redline speed is actually a function of Mach number, not TAS. This doesn't really matter at 8000, but it's a big consideration at 25000.
2) RSVM. ATC stacks aircraft closer together at high altitudes based on special certification requirements usually only achievable by jets. Without RSVM capability, you'll have limited access to altitudes above 24,000. Of course, unless you're IFR, you won't be flying above 17,500 anyway.
3) Engine efficiency. Even with a well-engineered turbocharger, the engine will most likely reach it's critical altitude in the high teens. Going higher will cost you time and/or fuel, unless you can find favorable tailwinds. At the end of the day, turbos usually fly in the mid to high teens unless weather forces them higher.
4) O2 practicalities. Oxygen systems get complicated (and very critical) at altitudes above 16,000 feet or so. The cannula can't get the job done up there, so you really need a pressure mask.
All that said, I love the idea. Due to thermal stress issues, turbos gemerally relegate aircraft engines to travel use (no aerobatics or short hops), but a turbocharged rocket would be hard to beat for xc travel by anything but a $2M turboprop aircraft.
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02-22-2011, 10:19 PM
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Join Date: Mar 2005
Location: Calgary, Canada
Posts: 5,766
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No problem to get a ton of power out of a properly built IO-540 with turbocharging. You probably don't need to exceed 30 inches to get your 275 mph at say 18,000 feet where you're still ok with the cannula. With modern turbos, the engine's critical altitude will likely be higher than your's or the Rocket's, we can jam out PRs of 4 to 1.
Aerobatics and short hops no problem. With a proper turbo and intercooler setup and proper oil cooler, thermal issues should not be a big deal but you may pay with fuel flows if you want to go fast all the time. A mask is ok to 25,000 or so but ATC won't want you above there anyway. Above 25K you need a pressure mask which is not much fun.
It can be done and it would be a cool project.  
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02-23-2011, 05:13 AM
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Join Date: Jan 2005
Location: Ontario, Canada
Posts: 1,544
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Standard wing rockets are limited by their wings when it comes to higher speeds. As you get above 250 mph added power brings an ever decreasing speed increase. It gets worse the higher you climb. This is the main reason that Mark Fredrick came out with the EVO wing and it has proven itself at both higher speeds and higher altitudes.
There is also a c of g consideration with the standard wing rocket in that you really do not want to add too much more weight to the nose.
My recommendation would be to build it as a stock set up and if in a year or so you really do want to explore altitudes add the turbo at that time. You are going to build the plane and so you have every right to modify it.
__________________
Tom Martin RV1 pilot 4.6hours!
CPL & IFR rated
EVO F1 Rocket 1000 hours,
2010 SARL Rocket 100 race, average speed of 238.6 knots/274.6mph
RV4, RV7, RV10, two HRIIs and five F1 Rockets
RV14 Tail dragger
Fairlea Field
St.Thomas, Ontario Canada, CYQS
fairleafield@gmail.com
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