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andrew(at)nzactive.com
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 Posted: Sat Sep 13, 2008 12:28 am Post subject: HR 2 - any ideas on where to start looking to make my HR2 fa |
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Hi guys. I'm about to get serious about getting a little more speed out of my Rocket. I think it's, maybe, 10 knots (or more) slower than many of the HRs/F1s I read about. TAS in level flight seems to be a hair under 200 knots, WOT, at any altitude under 8000 feet. I'm wondering if anyone has any recommendations as to resources, ie, where can I start looking for information about how to tweak a little more speed out of an aircraft? Any books, websites, companies or other resources out there on this subject?
I'm presuming it's mainly about drag, cos I have a good condition 280 hp engine, and a ROC that's as good as any I've read about. I note that the elevator is down quite a bit in cruise, and wonder if could be robbing a few knots? The aircraft also flies with a constant very slight right hand aileron down to maintain wings level, and also has a couple of external antennae. Anyone care to comment on whether any of this stuff makes much of a difference? As I understand basic aerodynamic theory, parasitic drag is squared, in terms of its impact on airspeed, so I'm wondering if even the really small things matter when you're talking about c 200 knots?
Also,the cockpit isn't well sealed. I have a flip-over canopy, and when it's closed, there's still a 5 mm gap. Is this important?
Anything else that should be looked at? At this stage, a turbine is out of the question 
Last question, I guess, is the most important. Am I being unrealistic in hoping to see TAS of 210 knots????
I'd really appreciate any comments you guys might have on this matter. I know there's a wealth of experience out there...
Andrew (NZ)
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n395v
Joined: 10 Jan 2006
Posts: 450
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| Posted: Sat Sep 13, 2008 5:43 am Post subject: Re: HR 2 - any ideas on where to start looking to make my HR |
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What engine do you have. Your speed sounds typical for a 250-260HP.
Cleaning up all the items you mentioned might give you 3-5 knots.
I had the 250 HP IO 540 and saw 195 KTS TAS below 10,000 feet at max gross.
At 13,000 I could get 200 KTS at Max Gross and with just me and half fuel I would see 205 KTS TAS.
Also all Rocket drivers lie about their speed. Well maybe embellish a little.
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Lee Logan
Joined: 10 Jan 2006
Posts: 86
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| Posted: Sat Sep 13, 2008 6:31 am Post subject: HR 2 - any ideas on where to start looking to make my HR2 fa |
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Andrew: Two sources of information come to mind, neither directly associated with Rockets but the aerodynamics and engine recommendations will be very similar. The book "Speed with Economy" by Kent Paser is excellent. The book is centered on his experiments with his Midget Mustang, but the results were spectacular. It must be said that he tried a lot of ideas and clearly spent hundreds of hours on his ideas and on various projects, but his results speak for themselves. The book is not particularly sophisticated, with hand drawings and relatively poor photographs, but (it seems to me), it is also a labor of love wherein the author was all about sharing the information and results he developed and not about putting together an artsy coffee table book on the subject. It is an inexpensive book and worth every NZ penny you pay for it!
The other source are the CAFE Foundation Reports and Aircraft Performance Reports (http://cafefoundation.org/v2/research_home.php) in general and the one on Dave Ander's RV-4 in particular. His RV-4 is faster than any Rocket (I think) and though he has gone to very great lengths to get all the speed out of it he can, there is a wealth of ideas in both the CAFE APR on his aircraft (http://cafefoundation.org/v2/pdf_apr/RV-4.pdf) and in his own writings. Anders did 250.71 mph in his IO-306 powered RV-4 during the CAFE triathlon trials. His airplane is even faster than that now, I understand. You will have a long way to go to catch up to either of these guys, but then, they are true trail blazers in speed mods on our size airplanes.
Just found most of my "speed notes" in the big database I add to everytime I come across something interesting about RV's and Rockets. Sorry, this is long, but these are some of my notes on the subject including the basics of a briefing that Dave Anders himself gave at an EAA meeting some time back that someone recorded.
"
From Dave Anders Notes:
Propeller - Inlet - Cowl relationship
1) propeller thrust distribution for inlet location.
2) boundary layer thickness at back edge of spinner and shank
of the propeller.
3) differential pressure across inlet.
4) reverse flow on standard inlets.
5) prop extension to decrease flat plate area.
Inlet (stagnation inlet)
1) shape - round = smallest surface area/volume
easiest to provide best seal to plenum.
2) size - calculated from mass flow required for BTU from
engine chart.
Mass flow = area X velocity X plenum efficiency
Oversized inlets >velocity resulting in >pressure thus >cowl drag around the inlets.
3) round lip edge to decrease inlet stall and reduce inlet drag
Plenum design
1) uses Bernoulli's Law: volume = >velocity = >pressure
2) Greater *p across the cylinders carries off more BTU.
3) diffuser can diverge 5 deg/side ± (air flow remains attached due to >Velocity and >pressure)
4) A = area of inlet (calculated by mass flow requirement)
A = area at the rear of the effect diffuser
A = area over the cylinder and head, A area = A area
5) slowing the free stream velocity 10 - 40% >Cooling drag losses.
6) there should be no sharp bends or edges to minimize flow separation.
(My note: there's less leakage, no doubt)
Outlet - starts under the cylinders
1) area as small as possible to re-accelerate the air to free
stream condition to >drag.
2) Convergence zone leads to exit fuselage/firewall airfoil
rounded gentle curved sides should be ~ 35 deg.
3) shape - NACA studies
- straight sided rectangular shallow angle converging ramp
- ramp as parallel to free stream flow as possible at end
- width to depth ratio of ramp
a) 7 to 1 for cooling systems
b) 1 to 1 for exhausts (augmenter)
4) inlet to outlet ratio: what's recommended, what works & why.
a) stock Van's: RV4 ratio ~ 39sq" X 60sq" = 150%
RV6 ratio ~ 44sq" X 56sq" = 127%
(Dave's notes go on; he describes what he feels is a better 76% ratio, eg smaller outlet than inlet.
Obviously low speed climb condition is critical & req's more area than high speed level cond.)
******
Without debate, the hard DATA:
No leaks +
Smaller inlets +
Better shaped inlets +
Better location inlets
= less cooling drag
More esoteric but true:
Better flowing round inlets (nozzles) with airfoil profile
(not laminar but not a swirling reverse flow mess) +
Better area transitions (which could be better still **)
= less cooling drag
** Now my opinion, no data sorry, I'm convinced two separate L/R plenums are better than one big dog house plenum (Sam James). Area transition is larger than needed. Data? RV buddies have great luck with two separate plenums. You just don't need air over the middle of the case. Drag reduction is unknown, it may be small but cools nicely, so at least there's no loss & it weighs less. Another area I'd improve, leakage around the spinner. Min spinner/cowl gap is a common approach, but a seal behind the gap could reduce leakage into the lower cowl, which reduces efficiency. If air flow is out of the spinner gap it causes external plume-interference drag. Down side? Sealing is hard, and we're talking nitpick small gains, unlike the known large gain of a cowl/ring/diffuser/plenum system. Gaining 6 or 15 mph is like finding 10 or 15 HP with out burning more gas!
4. When you give the speed increase from a mod, don't just say you got 5 mph more, but say what the before and after speeds were so the percent increase can be calculated. The percent increases from each mod, expressed as a decimal, (3.3% = 1.033) can be multiplied together to give the overall increase which can be expected. One thing of note. I have noticed in my testing of RVs that the low 4.8:1 aspect ratio of the -6 causes much increased induced loss at higher density altitudes with its lower power/speed. Lower density, lower speed, higher CL, higher induced loss! As the plane's drag is decreased from mods, and the speed increases, the greater dynamic pressure will allow the wing to operate at a lower CL and decrease this loss, thus giving slightly more speed than would be expected just from the mod's percentage. For more speed from wing mods - down low - decrease area; up high, increase span with slashed tips that give more span/area!"
Hope this helps. I think there is more and perhaps more specific info on Dave Anders' work on the internet. I just don't have it in front of me right now.
Best of luck and be sure to share your results!
P.S. Are you on the South Island or North??
Regards,
Lee...
[quote][b]
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AV8ORJWC
Joined: 13 Jul 2006
Posts: 1149
Location: Aurora, Oregon "Home of VANS"
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| Posted: Sat Sep 13, 2008 6:49 am Post subject: HR 2 - any ideas on where to start looking to make my HR2 fa |
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Lee - thanks for your comprehensive post. I have the same interest as Andrew In my build. My first thought was that the engine is "advertised" as 280 and yet a dyno test might show significantly less output (as much as 8% less). Barnaby Wainfan did a remarkable presentation at OSH '08 and thrilled the crowd on this subject by his offer that Marc Cook and Kitplanes Magazine is going to offer his entire 36 months of installments on DVD.
Power always seems to get attention, then the prop and eventually all the little things that add to Real Drag Reduction. "Speed Notes" is another way of quantifying saving fuel consumption. No mention was made of the final Empty Weight. Weight creep with a resultant change of CG is also a factor.
John Cox
From: owner-rocket-list-server(at)matronics.com [mailto:owner-rocket-list-server(at)matronics.com] On Behalf Of Lee Logan
Sent: Saturday, September 13, 2008 7:30 AM
To: rocket-list(at)matronics.com
Subject: Re: HR 2 - any ideas on where to start looking to make my HR2 faster
Andrew: Two sources of information come to mind, neither directly associated with Rockets but the aerodynamics and engine recommendations will be very similar. The book "Speed with Economy" by Kent Paser is excellent. The book is centered on his experiments with his Midget Mustang, but the results were spectacular. It must be said that he tried a lot of ideas and clearly spent hundreds of hours on his ideas and on various projects, but his results speak for themselves. The book is not particularly sophisticated, with hand drawings and relatively poor photographs, but (it seems to me), it is also a labor of love wherein the author was all about sharing the information and results he developed and not about putting together an artsy coffee table book on the subject. It is an inexpensive book and worth every NZ penny you pay for it!
The other source are the CAFE Foundation Reports and Aircraft Performance Reports (http://cafefoundation.org/v2/research_home.php) in general and the one on Dave Ander's RV-4 in particular. His RV-4 is faster than any Rocket (I think) and though he has gone to very great lengths to get all the speed out of it he can, there is a wealth of ideas in both the CAFE APR on his aircraft (http://cafefoundation.org/v2/pdf_apr/RV-4.pdf) and in his own writings. Anders did 250.71 mph in his IO-306 powered RV-4 during the CAFE triathlon trials. His airplane is even faster than that now, I understand. You will have a long way to go to catch up to either of these guys, but then, they are true trail blazers in speed mods on our size airplanes.
Just found most of my "speed notes" in the big database I add to everytime I come across something interesting about RV's and Rockets. Sorry, this is long, but these are some of my notes on the subject including the basics of a briefing that Dave Anders himself gave at an EAA meeting some time back that someone recorded.
"
From Dave Anders Notes:
Propeller - Inlet - Cowl relationship
1) propeller thrust distribution for inlet location.
2) boundary layer thickness at back edge of spinner and shank
of the propeller.
3) differential pressure across inlet.
4) reverse flow on standard inlets.
5) prop extension to decrease flat plate area.
Inlet (stagnation inlet)
1) shape - round = smallest surface area/volume
easiest to provide best seal to plenum.
2) size - calculated from mass flow required for BTU from
engine chart.
Mass flow = area X velocity X plenum efficiency
Oversized inlets >velocity resulting in >pressure thus >cowl drag around the inlets.
3) round lip edge to decrease inlet stall and reduce inlet drag
Plenum design
1) uses Bernoulli's Law: volume = >velocity = >pressure
2) Greater *p across the cylinders carries off more BTU.
3) diffuser can diverge 5 deg/side ± (air flow remains attached due to >Velocity and >pressure)
4) A = area of inlet (calculated by mass flow requirement)
A = area at the rear of the effect diffuser
A = area over the cylinder and head, A area = A area
5) slowing the free stream velocity 10 - 40% >Cooling drag losses.
6) there should be no sharp bends or edges to minimize flow separation.
(My note: there's less leakage, no doubt)
Outlet - starts under the cylinders
1) area as small as possible to re-accelerate the air to free
stream condition to >drag.
2) Convergence zone leads to exit fuselage/firewall airfoil
rounded gentle curved sides should be ~ 35 deg.
3) shape - NACA studies
- straight sided rectangular shallow angle converging ramp
- ramp as parallel to free stream flow as possible at end
- width to depth ratio of ramp
a) 7 to 1 for cooling systems
b) 1 to 1 for exhausts (augmenter)
4) inlet to outlet ratio: what's recommended, what works & why.
a) stock Van's: RV4 ratio ~ 39sq" X 60sq" = 150%
RV6 ratio ~ 44sq" X 56sq" = 127%
(Dave's notes go on; he describes what he feels is a better 76% ratio, eg smaller outlet than inlet.
Obviously low speed climb condition is critical & req's more area than high speed level cond.)
******
Without debate, the hard DATA:
No leaks +
Smaller inlets +
Better shaped inlets +
Better location inlets
= less cooling drag
More esoteric but true:
Better flowing round inlets (nozzles) with airfoil profile
(not laminar but not a swirling reverse flow mess) +
Better area transitions (which could be better still **)
= less cooling drag
** Now my opinion, no data sorry, I'm convinced two separate L/R plenums are better than one big dog house plenum (Sam James). Area transition is larger than needed. Data? RV buddies have great luck with two separate plenums. You just don't need air over the middle of the case. Drag reduction is unknown, it may be small but cools nicely, so at least there's no loss & it weighs less. Another area I'd improve, leakage around the spinner. Min spinner/cowl gap is a common approach, but a seal behind the gap could reduce leakage into the lower cowl, which reduces efficiency. If air flow is out of the spinner gap it causes external plume-interference drag. Down side? Sealing is hard, and we're talking nitpick small gains, unlike the known large gain of a cowl/ring/diffuser/plenum system. Gaining 6 or 15 mph is like finding 10 or 15 HP with out burning more gas!
4. When you give the speed increase from a mod, don't just say you got 5 mph more, but say what the before and after speeds were so the percent increase can be calculated. The percent increases from each mod, expressed as a decimal, (3.3% = 1.033) can be multiplied together to give the overall increase which can be expected. One thing of note. I have noticed in my testing of RVs that the low 4.8:1 aspect ratio of the -6 causes much increased induced loss at higher density altitudes with its lower power/speed. Lower density, lower speed, higher CL, higher induced loss! As the plane's drag is decreased from mods, and the speed increases, the greater dynamic pressure will allow the wing to operate at a lower CL and decrease this loss, thus giving slightly more speed than would be expected just from the mod's percentage. For more speed from wing mods - down low - decrease area; up high, increase span with slashed tips that give more span/area!"
Hope this helps. I think there is more and perhaps more specific info on Dave Anders' work on the internet. I just don't have it in front of me right now.
Best of luck and be sure to share your results!
P.S. Are you on the South Island or North??
Regards,
Lee...
[quote] [/b][/b][/b][/b]http://www.matronics.com/Navigator?Rocket-List[/b][/b]http://forums.matronics.com[/b][/b]http://www.matronics.com/contribution[/b] [b]
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smokyray(at)rocketmail.co
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| Posted: Mon Sep 15, 2008 10:57 am Post subject: HR 2 - any ideas on where to start looking to make my HR2 fa |
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Lee,
Awesome post! Steve Wittman once told me when he needed more speed he trimmed his prop an inch, and took off his shoes! His 1st C-85 would turn 4000 RPM. Dave Anders IO-360 was built by LyCon and the special Hartzell he runs turns 2850+ during races (230HP). Nemesis 1 also turned 3500-4000 rpm. My point is exactly what Tom stated, the prop and engine have ALOT to do with speed.
My 12 year old stock HR2 with a C4B5 with LyCon 10.4:1/Hartzell "D" 2 blade I have the following numbers.
1: Cowl: I need the cooling, it's 90F at Thanksgiving here! Stock with tight baffles, trimmed lower cowl, RTV everywhere!
2. Wheelpants: I need bigger tires for my rough 1800' strip, but my Van's PR pants on the 380's work great. Off to On yielded 7 knots.
3. Temps: I trimmed my cowling to allow climb CHT's not to exceed 400F.
4. Speed: Low altitude 27 squared=200 Knots, many GPH!
8500' 20/2300 = 185KTAS at 11 GPH.
For me the best news is at 16"MP and 2150 I can cruise at 155 knots at 7GPH all day and my CHT's never get above 300F and oil stays at 180 on the hottest days.
V/R
Smokey
--- On Sat, 9/13/08, Lee Logan <leeloganster(at)gmail.com> wrote:
| Quote: | From: Lee Logan <leeloganster(at)gmail.com>
Subject: Re: HR 2 - any ideas on where to start looking to make my HR2 faster
To: rocket-list(at)matronics.com
Date: Saturday, September 13, 2008, 2:30 PM
Andrew: Two sources of information come to mind, neither directly associated with Rockets but the aerodynamics and engine recommendations will be very similar. The book "Speed with Economy" by Kent Paser is excellent. The book is centered on his experiments with his Midget Mustang, but the results were spectacular. It must be said that he tried a lot of ideas and clearly spent hundreds of hours on his ideas and on various projects, but his results speak for themselves. The book is not particularly sophisticated, with hand drawings and relatively poor photographs, but (it seems to me), it is also a labor of love wherein the author was all about sharing the information and results he developed and not about putting together an artsy coffee table book on the subject. It is an inexpensive book and worth every NZ penny you pay for it!
The other source are the CAFE Foundation Reports and Aircraft Performance Reports (http://cafefoundation.org/v2/research_home.php) in general and the one on Dave Ander's RV-4 in particular. His RV-4 is faster than any Rocket (I think) and though he has gone to very great lengths to get all the speed out of it he can, there is a wealth of ideas in both the CAFE APR on his aircraft (http://cafefoundation.org/v2/pdf_apr/RV-4.pdf) and in his own writings. Anders did 250.71 mph in his IO-306 powered RV-4 during the CAFE triathlon trials. His airplane is even faster than that now, I understand. You will have a long way to go to catch up to either of these guys, but then, they are true trail blazers in speed mods on our size airplanes.
Just found most of my "speed notes" in the big database I add to everytime I come across something interesting about RV's and Rockets. Sorry, this is long, but these are some of my notes on the subject including the basics of a briefing that Dave Anders himself gave at an EAA meeting some time back that someone recorded.
"
From Dave Anders Notes:
Propeller - Inlet - Cowl relationship
1) propeller thrust distribution for inlet location.
2) boundary layer thickness at back edge of spinner and shank
of the propeller.
3) differential pressure across inlet.
4) reverse flow on standard inlets.
5) prop extension to decrease flat plate area.
Inlet (stagnation inlet)
1) shape - round = smallest surface area/volume
easiest to provide best seal to plenum.
2) size - calculated from mass flow required for BTU from
engine chart.
Mass flow = area X velocity X plenum efficiency
Oversized inlets >velocity resulting in >pressure thus >cowl drag around the inlets.
3) round lip edge to decrease inlet stall and reduce inlet drag
Plenum design
1) uses Bernoulli's Law: volume = >velocity = >pressure
2) Greater *p across the cylinders carries off more BTU.
3) diffuser can diverge 5 deg/side ± (air flow remains attached due to >Velocity and >pressure)
4) A = area of inlet (calculated by mass flow requirement)
A = area at the rear of the effect diffuser
A = area over the cylinder and head, A area = A area
5) slowing the free stream velocity 10 - 40% >Cooling drag losses.
6) there should be no sharp bends or edges to minimize flow separation.
(My note: there's less leakage, no doubt)
Outlet - starts under the cylinders
1) area as small as possible to re-accelerate the air to free
stream condition to >drag.
2) Convergence zone leads to exit fuselage/firewall airfoil
rounded gentle curved sides should be ~ 35 deg.
3) shape - NACA studies
- straight sided rectangular shallow angle converging ramp
- ramp as parallel to free stream flow as possible at end
- width to depth ratio of ramp
a) 7 to 1 for cooling systems
b) 1 to 1 for exhausts (augmenter)
4) inlet to outlet ratio: what's recommended, what works & why.
a) stock Van's: RV4 ratio ~ 39sq" X 60sq" = 150%
RV6 ratio ~ 44sq" X 56sq" = 127%
(Dave's notes go on; he describes what he feels is a better 76% ratio, eg smaller outlet than inlet.
Obviously low speed climb condition is critical & req's more area than high speed level cond.)
******
Without debate, the hard DATA:
No leaks +
Smaller inlets +
Better shaped inlets +
Better location inlets
= less cooling drag
More esoteric but true:
Better flowing round inlets (nozzles) with airfoil profile
(not laminar but not a swirling reverse flow mess) +
Better area transitions (which could be better still **)
= less cooling drag
** Now my opinion, no data sorry, I'm convinced two separate L/R plenums are better than one big dog house plenum (Sam James). Area transition is larger than needed. Data? RV buddies have great luck with two separate plenums. You just don't need air over the middle of the case. Drag reduction is unknown, it may be small but cools nicely, so at least there's no loss & it weighs less. Another area I'd improve, leakage around the spinner. Min spinner/cowl gap is a common approach, but a seal behind the gap could reduce leakage into the lower cowl, which reduces efficiency. If air flow is out of the spinner gap it causes external plume-interference drag. Down side? Sealing is hard, and we're talking nitpick small gains, unlike the known large gain of a cowl/ring/diffuser/plenum system. Gaining 6 or 15 mph is like finding 10 or 15 HP with out burning more gas!
4. When you give the speed increase from a mod, don't just say you got 5 mph more, but say what the before and after speeds were so the percent increase can be calculated. The percent increases from each mod, expressed as a decimal, (3.3% = 1.033) can be multiplied together to give the overall increase which can be expected. One thing of note. I have noticed in my testing of RVs that the low 4.8:1 aspect ratio of the -6 causes much increased induced loss at higher density altitudes with its lower power/speed. Lower density, lower speed, higher CL, higher induced loss! As the plane's drag is decreased from mods, and the speed increases, the greater dynamic pressure will allow the wing to operate at a lower CL and decrease this loss, thus giving slightly more speed than would be expected just from the mod's percentage. For more speed from wing mods - down low - decrease area; up high, increase span with slashed tips that give more span/area!"
Hope this helps. I think there is more and perhaps more specific info on Dave Anders' work on the internet. I just don't have it in front of me right now.
Best of luck and be sure to share your results!
P.S. Are you on the South Island or North??
Regards,
Lee...
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