Today's Message Index:
----------------------
1. 11:57 AM - Re: HR 2 - any ideas on where to start looking to make my HR2 faster (Smoky Ray)
2. 05:41 PM - conditonal inspection checklist (Jim Stone)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: HR 2 - any ideas on where to start looking to make my |
HR2 faster
Lee,
- Awesome post! Steve Wittman once told me when he needed more speed he t
rimmed his prop an inch, and took off his shoes! His 1st C-85 would turn 40
00 RPM. Dave Anders IO-360 was built by LyCon and the special Hartzell he r
uns 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 wi
th 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 tigh
t baffles, trimmed lower cowl, RTV everywhere!
2. Wheelpants: I need bigger tires for my rough 1800' strip, but my Van's P
R 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 0 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 hott
est days.
V/R
Smokey
--- On Sat, 9/13/08, Lee Logan <leeloganster@gmail.com> wrote:
From: Lee Logan <leeloganster@gmail.com>
Subject: Re: Rocket-List: HR 2 - any ideas on where to start looking to mak
e my HR2 faster
Andrew:- Two sources of information come to mind, neither directly associ
ated with Rockets but the aerodynamics and engine recommendations will be v
ery similar.- The book "Speed with Economy" by Kent Paser is excellent.
- The book is centered on his experiments with his Midget Mustang, but th
e results were spectacular.-- It must be said that he tried a lot of id
eas and clearly spent hundreds of hours on his ideas and on various project
s, but his results speak for themselves.- The book is not particularly so
phisticated, with hand drawings and relatively poor photographs, but (it se
ems to me), it is also a labor of love wherein the author was all about sha
ring the information and results he developed and not about putting togethe
r an artsy coffee table book on the subject.- It is an inexpensive book a
nd 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 a
nd the one on Dave Ander's RV-4 in particular.- His RV-4 is faster than a
ny 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 AP
R 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 duri
ng 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 t
hese 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 ba
ck 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 th
e 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 =B1 (air flow remains attached due to >V
elocity 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 s
maller 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 ar
e better than one big dog house plenum (Sam James). Area transition is larg
er 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 unk
nown, it may be small but cools nicely, so at least there's no loss & it we
ighs less. Another area I'd improve, leakage around the spinner. Min spinne
r/cowl gap is a common approach, but a seal behind the gap could reduce lea
kage into the lower cowl, which reduces efficiency. If air flow is out of t
he spinner gap it causes external plume-interference drag. Down side? Seali
ng is hard, and we're talking nitpick small gains, unlike the known large g
ain of a cowl/ring/diffuser/plenum system. Gaining 6 or 15 mph is like find
ing 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 mp
h more, but say what the before and after speeds were so the percent increa
se can be calculated. The percent increases from each mod, expressed as a d
ecimal, (3.3% = 1.033) can be multiplied together to give the overall inc
rease which can be expected. One thing of note. I have noticed in my testin
g of RVs that the low 4.8:1 aspect ratio of the -6 causes much increased in
duced loss at higher density altitudes with its lower power/speed. Lower de
nsity, 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 g
iving slightly more speed than would be expected just from the mod's percen
tage. For more speed from wing mods - down low - decrease area; up high, in
crease 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...
=0A=0A=0A
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | conditonal inspection checklist |
Hey Guys,
Well I survived my first year in the Rocket, 140 hours or so and lots of
fun. To keep it safe and legal for the next year, I'll need to do a
conditional inspection. Anyone have a checklist they like and is set up
for the Rocket?
Just send it to me direct.
Thank,
Jim Stone
HRII
Louisville KY
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|