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  #21  
Old 02-28-2011, 05:22 PM
prporter prporter is offline
 
Join Date: Jul 2006
Location: Vul, VA
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Quote:
Originally Posted by DesertFlier View Post
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.
Hi Desert Flyer,

What are you currently flying?
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  #22  
Old 02-28-2011, 08:38 PM
Jeff Brenhaug's Avatar
Jeff Brenhaug Jeff Brenhaug is offline
 
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Location: Minnesota
Posts: 95
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12,000' was a good number to cruise at x-ctry in the HR3 and I never went above 14 as it didn't do anything for me.
The wing is the factor and all the F1 EVO guys know that.
I didn't need more speed (I can't believe I just said thet) from the HR3, I already had that, but to go higher would require a tapered laminar flow airfoil or I was just burning gas and stressing the powerplant with high EGT's, CHT's and oil temps.
The HR2's and F1's were good down low and the F1 EVO's were good up high.
I'm sure all the armchair quarterbacks who don't own an airplane or know any different will jump in and argue.
My 2cents.
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  #23  
Old 02-28-2011, 10:43 PM
DesertFlier DesertFlier is offline
 
Join Date: Feb 2011
Location: California City, CA
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Originally Posted by prporter View Post
Hi Desert Flyer,

What are you currently flying?
Nothing. There probably won't be anything until I build it with my own two hands.
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  #24  
Old 03-01-2011, 01:21 AM
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Bill Wightman Bill Wightman is offline
 
Join Date: Aug 2005
Location: OKC, OK
Posts: 687
Default Supercharged Rocket

I've flown the supercharged F1/EVO airplane that Wolfgang built a few times. It has an IO540 with a Vortech supercharger, and produces about 360hp. Not sure how much boost the Vortech can produce, but I've seen near 40 inches on takeoff, which launches the airplane with authority.

The airplane is fast, and does pick up speed when pointed down hill pretty quickly. That's come into play recently, as I've done a bit of aerobatic instruction in it from the back seat but its totally manageable if the pilot maintains awareness and thinks ahead.

I admire your want for an airplane that can both go fast and be efficient, but the only good way to do that is to manage drag at the higher altitudes needed for efficiency. The wing is the biggest single contributing component to drag on the airplane, so its of utmost importance to mate a well designed wing to the airplane if fast + efficient is the goal.

Induced drag isn't exclusively tied to aircraft weight; its really better to relate it to angle of attack (more AOA = more Cd_i). So the operational factors that drive AOA higher also drive Cd_i higher: slower speeds/higher weights/increased load factor are typically responsible for driving Cd_i up. As altitude increases, the wing will produce more induced drag for a given TAS due to drop off in dynamic pressure with altitude.

In terms of wing design, aspect ratio has a major effect on induced drag, with higher AR driving induced drag lower. So, for good altitude operation, that translates into the need for a higher aspect ratio wing, and the EVO wing wins that contest hands down, versus the short wing Rockets.
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  #25  
Old 03-01-2011, 05:48 AM
Tom Martin Tom Martin is offline
 
Join Date: Jan 2005
Location: Ontario, Canada
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My friend and traveling buddy, Wayne Hadath, flies a fast straight wing rocket, I have an EVO wing. Although we do a lot of cross country work we rarely get extended high altitude travel, usually due to weather considerations. Year in and year out at altitudes of 8000 feet or less we burn the same amount of fuel. We always fly at 22 squared burning between 10 and eleven gph.
Two years ago on the way home from Pagosa Springs Colorado we had 3 hour leg at altitudes in the 10.5 to 13.5K range. I set up my normal power setting with Wayne off my wing. At the end of the three hour flight I had burned exactly 30 gallons and he had used an extra TEN gallons just to keep up.
With four years of effort in drag reduction I now have an airplane that is flirting with red line in straight and level flight without the expense of a turbo charger. I flew the AirVenture Cup Race this year at 17,500 feet with an average speed of 228 knots. I had to start my descent 125 miles out to keep from busting red line. I am not sure that there would be any value in adding a turbo to this aircraft. Spend your time and money on the proper wing and drag reduction.
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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

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St.Thomas, Ontario Canada, CYQS
fairleafield@gmail.com
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  #26  
Old 03-01-2011, 08:28 AM
prporter prporter is offline
 
Join Date: Jul 2006
Location: Vul, VA
Posts: 316
Wink

Wolfgang's turbo'ed Rocket was fantastic. He did a superb job on building it as well. He is a real craftsman. I wanted to do something similiar as his, but came to the conclusion that (for me, anyway) the cost, plus the many, many hours of time that would be needed to get it to fit, and tweaking it for proper operation would have taken away the pleasure of flying it, and the actual numbers in cruise didn't increase that significantly. As others have posted, you would be limited by the Vne which would be realized much sooner before you even got close to the output of the TC/SC. The CHT's will also require you to ramp up the fuel flow and thus eat into your economy somewhat. On paper, the economy (MPG) turns out very, very close with the SC vs normally aspirated. For the people with Rockets that "merely" pump out 260 HP, I have yet to talk to any of them that were not thrilled with the performance they got out of them- climb, or cruise(Having said that, my engine puts out 290+ HP). With 260, Vne is still something that they have to pay attention to as they frequently flirt with that number. I think the real performance you would be looking at with the TC/SC would be the climb- now, that is someting that we ALL can agree on would be awesome!

OK, as you all now realize, the real reason I have to "poo-poo" the TC/SC set-up is because it is beyond my price/skill-set abilities, and my rant merely makes me feel better for not having done it.

Look around and find a "stock" Rocket to get a ride in- I think you would agree that there is really nothing lacking-
My .02.
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  #27  
Old 03-01-2011, 10:43 AM
rocketbob's Avatar
rocketbob rocketbob is offline
 
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Quote:
Originally Posted by Tom Martin View Post
Two years ago on the way home from Pagosa Springs Colorado we had 3 hour leg at altitudes in the 10.5 to 13.5K range. I set up my normal power setting with Wayne off my wing. At the end of the three hour flight I had burned exactly 30 gallons and he had used an extra TEN gallons just to keep up.
The thing that one has to keep in mind about the EVO is that the additional wing area produces both more induced and parasitic drag. The three other penalties are reduced cg range, ailerons that are heavier, and an additional 75lbs to the empty weight. With all of Tom's speed mods and with Wayne having a stock airframe, burning the same speeds/fuel burns, negates some of the strong points of the EVO wing for I would venture to say at least 99% of the flying I myself typically do. This is why I never felt favorably about the EVO after flying it for a dozen hours. Wasn't a game-changer for me. The short stubby wing still works well for me.

The other question I have is what if one just added to the wingspan of the sport wing and beefed it up accordingly to have the same area as the EVO, if one would get similar performance up high. The RV-10 exhibits some similar characteristics in this regard so I'm not convinced that tapering a wing offers up as many advantages as one might think.
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N9187P PA-24-260B Comanche, flying
N678X F1 Rocket, under const.
N244BJ RV-6 "victim of SNF tornado" 1200+ hrs, rebuilding
N8155F C150 flying
N7925P PA-24-250 Comanche, restoring
Not a thing I own is stock.

Last edited by rocketbob : 03-01-2011 at 10:51 AM.
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  #28  
Old 03-01-2011, 11:18 AM
molson309 molson309 is offline
 
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Location: Longmont, CO
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Quote:
Originally Posted by rocketbob View Post
The thing that one has to keep in mind about the EVO is that the additional wing area produces both more induced and parasitic drag.

--snip--
IIRC, the EVO wing has slightly less surface area than the square wing, by a couple of ft^2. You are correct about the extra weight - I was told that this wing was originally designed for a heavier airplane, so it is stronger than needed for a Rocket airframe.


There are definitely tradeoffs with the EVO wing, but I really like the high altitude performance as well as the slow speed landing characteristics. My EVO Rocket lands slower - by seemingly a significant margin - than my RV-7A.

Mark Olson N407V RV-7A N16XV F1-EVO
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  #29  
Old 03-01-2011, 11:58 AM
nucleus nucleus is offline
 
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Location: Bozeman, Montana
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Quote:
Originally Posted by molson309 View Post
IIRC, the EVO wing has slightly less surface area than the square wing, by a couple of ft^2.

Mark Olson N407V RV-7A N16XV F1-EVO
Regular wing: 104 Square Feet
EVO wing: 102 Square Feet
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  #30  
Old 03-01-2011, 03:18 PM
rocketbob's Avatar
rocketbob rocketbob is offline
 
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Quote:
Originally Posted by nucleus View Post
Regular wing: 104 Square Feet
EVO wing: 102 Square Feet
My memory fails me...I thought there was a few more ft. of area on the EVO.
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Bob Japundza CFI A&PIA
N9187P PA-24-260B Comanche, flying
N678X F1 Rocket, under const.
N244BJ RV-6 "victim of SNF tornado" 1200+ hrs, rebuilding
N8155F C150 flying
N7925P PA-24-250 Comanche, restoring
Not a thing I own is stock.
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