G

GRANT ED

Active Member
My dad and I have just started building an RV-7. I was thinking about extracting as much performance from my plane as possible. What "speed mods" have people done and how successful were they? I have been looking at different cowlings and have found the James aircraft site. Has anyone used this cowling? What was the result?
 
James cowl

A friend of mine is using this cowl on an IO 360 equipped RV8 and has had many many more hours of fitment problems than the stock RV cowl. Nothing seems to fit well as is the case with the RV cowl. They've had to cut the plenum, the cowl and a multitude of other time consuming details in order to make it work. We, on the other hand, have the stock RV cowl fitted to our RV6 and even though this is our first, it has gone a whole lot easier. I see him weekly and for now am very glad that we decided to forego the (claimed) added few MPH.
Pierre
 
Hmm, that does not sound to good. I have read a story on another site about a guy who used the cowl and plenum on I think an RV-6. His opion was the cowling was great but the plenum was a major PITA. :(
 
There is no silver bullet with regards to speed mods. You do what you can during construction by paying particular attention to minor details. Hopefully in the aggregate, your efforts will produce some further enhancement in speed. I focused on making the airscoop seal as tight as possible. Mainly for cosmetic reasons I made the gap between the spinner and cowl close....manageble, but close. I used flush, rather than the protruding brazier rivets on the pilot and passenger steps. The steps were then faired to the airframe by beveling and sculpting proseal around them to make as smooth a transition as possible. I installed 2 flush mounted camlock latches to secure the oil access door instead of using the kit supplied parts. All 6 landing gear intersection fairings were installed . Many people omit either the upper or lower intersection fairing on the nose gear...I didn't. The wing root fairing seal is tight and the gap between the retracted flaps and fuselage is close. I hid the GPS, VOR, MB, and ELT antennas within the airframe. I installed the wheel pants as low as I dared. The hinge pins holding the upper and lower cowls together are captured and hidden beneath a triangular shaped aerodynamic adornment rather than the 90 degree bend and screw attach the plans call for. Even the tip fairing is butt sealed to the vertical stab for maximum smoothness. Finally, I installed a Sensenich fixed pitch prop that proved to deliver the fastest cruise speed of all the props Van's tested a few years ago on the same (RV-6?) airframe. Will these varied efforts pay off? I'll know soon enough. First flight will be in the upcoming weeks.

Rick Galati RV-6A "Darla"
 
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I'm sure Jay Pratt will offer more info on this, however, his recent reports about using a Grove Gear were very intriguing to read. Supposedly it makes a world of difference to use one.

Take care,
 
I have several details shots posted that describe some of the things I've mentioned. Check out my gallery section in http://www.rvaero.com/
Unfortunately, I do not have photographs of the wingtip installed antennas posted there, but are the widely available Bob Archer design. If you do elect to purchase his antennas, I would recommend buying them directly from him rather than a traditional aircraft parts supplier. His customer service is generous, personal and freely offered.
 
Wing tip antennas are over rated

Rick6a said:
Unfortunately, I do not have photographs of the wingtip installed antennas posted there, but are the widely available Bob Archer design. QUOTE]

My suggestion is there are many places to make speed other than the antennas. I will say with good assurance that all external mounted antennas on a RV will perform much better than any internal wing-tip antenna. From flight test and classic aerodynamic calculations, at 200 MPH external antennas equivelent speed loss is as follows:

Comm antenna = 1/2 mph
Transponder antenna = 1/4 mph
VOR/GS/LOC antenna=1/2 mph
(GPS, ELT I don't mention because they can be placed under the canopy or tail fairing)

So to gain may be 1-1.5 mph you have to sacrifice performance of your Com/Nav radio, plus added weight from long coax and longer building time. If anyone says their wing tip antenna works great, I don't doubt that. However "works great" is relative and many have been very un-happy with their Wing-Tip antenna. Talking to the tower 10 miles away is not like talking to a flight service or an ATC remote transmitter 150 miles away. As far as NAV performance (VOR) I would think the range would also be limited or directional (blind spots). May be NAV is not a problem with GPS and the fact the GS/LOC is for terminal (short range) use.

Builders think nothing of using a 3 blade props (-8 MPH) or steps on their "A" model (-? MPH). You can gain speed with attention to details, rigged well and making small mods, such as fairings and a modified cowl and cooling plenum. The latter mod, cowl & cooling can produce 7-8mph more speed by reducing the cooling inlet area and cooling leakage (loss). This reduced cooling drag is one area where Van's stock design can be improved the most. For those who say this mod is not worth it, I would point to Dave Anders, Tracy Saylor and Dick Martin. All have Sam James style cowls and cooling plenums and race winning RV's. You don't have to use Sam James cowl BTW. You can modify a stock cowl and baffling very cost effectively, but like all mods it takes time, effort and money. It just depends on how bad you want it.

There is speed and then there is speed with economy as the book of the same name suggest (per previous post). One obvious way to go faster is have a pumped up engine with more HP. However to go faster also requires attention to details. First build it light and straight. Remember the fastest RV is Dave Anders highly modified RV-4 with a highly modified IO-360. At 254mph, Dave's RV is only 32-50 MPH than your typical stock RV at (200 - 222) MPH. The point is RV's are already fast and it is quite an achievement to gain any speed over the stock benchmark, much less 30-50mph which is amazing. The faster you go the harder it is to gain each MPH. However, it can be done as Tracy Saylor (+235mph RV-6) and Dave have shown. To see how Dave Anders did some of his magic, see:

http://www.cafefoundation.org/aprs/RV-4.pdf

Dave's 254 MPH RV-4 is still the current Cafe Foundation's Triaviation Champion. I would guess the average builder is not willing to make the effort Dave has, but still there is speed to be had. Except for the cowl and cooling mod most changes are measured in 1 or 2 MPH increments.
Cheers George :D

PS Suggest you look at the New Hartzell Blended airfoil constant speed prop. I agree with the previous post, if you go with a fixed pitch prop the Sensenich is a good choice all around.
Click to expand...
 
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So to gain may be 1-1.5 mph you have to sacrifice performance of your Com/Nav radio...........


I tend to agree with this point. I certainly wished to hide all the antennas but in the greater interest of enhanced communication capability, I did mount a Comant bent whip comm antenna and transponder stubby on the belly. I am based under Class B airspace. Sometimes, one must defer an interest in speed enhancement to other more practical considerations. In my case, that means willing to live with an admittedly more draggy and slightly less cosmetic arrangement. I did not mention this in my original post and regret any misunderstanding.
 
It seems like the best speed "mod" isn't really a mod at all: build it real good and straight so as to need a minimum of draggy trim tabs and rigging tweaks. For example, the vertical location of the ailerons. Another biggy has got to be the alignment of the gear leg fairings and wheel pants. Having that big old leg fairing even a little crooked has got to be a way bigger drag source than some teeny little antenna.
 
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the Need for SPEED...

I had the privilege of meeting Dave Anders at Oshkosh a few years back. I was sitting in the RV-7 demonstrator at Van's tent and this stranger starts asking ME a bunch of questions (because I had a NASA tee shirt on). Fortunately I recognized him from the many magazine and web articles I had read. I was most impressed with the PASSIONATE attention to detail he put into his RV-4 to reduce drag. He did lots of research and found what works. One idea I can share with you is the way he adjusted his landing gear leg fairings to the optimum position. He dissolved crayon (like the kids use) to a mushy viscosity with solvent. He then placed 3 or 4 dots on each gear leg fairing and flew a test flight. Upon landing he would adjust the position of his fairings based on how well the crayon (used for its color) flowed around both inner and outer surfaces of the fairing. He would then fly another test flight, repeating the adjustment procedure after each flight. When he had the solvated crayon drips meeting at the trailing edge, he then had found the optimum position of the fairings. Note that the procedure some have used of aligning the fairings with the centerline of the airplane doesn't take into account the prop wash of the propeller. Maybe it doesn't matter at 250+ mph. But I'm sure not going to argue with Dave Anders...
He had a few other interesting ideas that were surprising to me also, but that's for another day...
Don Hull
P.S. Yes a 3-bladed propeller tends to be slower than a two bladed propeller all other factors being equal. However, the 3-bladed propeller tends to be smoother. The model airplane control line speed racers used to use (I assume they still do.) single bladed props with a counterbalance on the other end!
Building an airplane is a series of compromises.
 
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Catto prop?

jvarney said:
Really? I thought the CATTO 3 bladers gave us a slight increase in speed?James
Click to expand...
James I was comparing constant speed to constant speed 2 vs 3 blade. However apples and apples, constant speed and fixed pitch are two different things.

However for a fixed pitch prop, the fixed metal Sench is a good choice and I would venture a guess could be faster than a 2 or 3 blade CATTO. It depends on prop pitch and the RPM the engine is turning. A fixed pitch can get higher top speed by over-rev of the engine. (The Reno formula races rev to crazy RPM's.) More Revs = more HP=more speed (withing limits). Blade thickness is a factor in efficency. Metal blade thickness can be thinner than wood based props. Also metal is less maintenance. I don't know about CATTO but they do wrap the wood with fiberglass, so may be it is less affected by moisture and the required periodic re-torque of bolts that wood props need.

I have heard good things about CATTO performance, and one negative thing regarding a structural failure.

Cheers George
 
Archer wing tip antennas

rv6builder48138 said:
Sam Buchanan seems to think that the Sportcraft internal antenna works well for receiving VOR signals:

http://home.hiwaay.net/~sbuc/journal/sportcraft.htm

Would be interesting to hear from anyone who's installed a similar antenna for use with their COM.
Click to expand...

The Bob Archer VOR antenna in my wing tip works awesome. The Bob Archer COM antenna in my other wing tip works "acceptably" but not as well as a belly mounted bent whip. Range and clarity are not up to par with the bent whip on the belly. It's a bit "directional" as well, and I believe airframe shadowing is coming into play. That said, it serves my purpose well as a backup and ATIS-getter and stays out of the slipstream.

)_( Dan
RV-7 N714D
http://www.rvproject.com
 
Anyone know where to find the "Bullet" (might be "Silver Bullet") tailwheel linkage? It came out a little while ago, similar to the rocket linkage but more streamlined..I cannot find this guy to save my life.
 
Fast RV's

Dave Anders made his RV go fast, I'll give him that. It's a straight airplane, rigged well and has lot's of mods on it. However, what most people don't realize is his engine is putting out 230+HP. That makes a huge difference right there. He also tore out all his floor boards, rear seats and a bunch of other stuff to win the Cafe race. I even think he went to the restroom before the flight. Granted, he won but his airplane is not really practical. I've heard he can't climb at high angles of attack because he'll overheat his engine. My RV-6 goes 218MPH wide open. It has 190hp, a scoopless cowling, constant speed. prop, tight intersection fairings, wheel pants, a well fitted canopy and shear wingtips. It's also a very clean and a well rigged airplane. But the one thing I wanted to try to do it make it practical. Speed is nice but usually when you try to get more speed you loose usefullness. Plenums, tight cowls, gap seals, fairing over small protrusions, increasing HP, stuff like really subtracts from Van's idea of simplicity. Beside the wings on RV's hit a giant wall of drag at 200mph. If you want to go really fast, change the wing, install 260hp and you can go 265, land at 100mph and not climb as well. Van's has done their homework to offer a airplane that gives the best of all the worlds. Speed, beauty, utility, slow flight, handling,easy to put togther and most of all lower cost than most other airplanes.
 
Speed mods

As noted I think the thing to do cleanest job on construction possible. Any exposure is drag, plain and simple.

On my nearly completed 7 I glassed in all of the tail glass and filled the channels on the counter balances and stabilizer. Also spent LOTS of time getting the tip canopy frame to fit as perfect as possible. I have the Archer antennas and one bent whip.

One thing I did do that I gleaned from a site that I can't find now is make a fence on the wing tips. The fence runs from 25% of the chord to the tip. A friend of mine who was a big name in Soaring many years ago and a fanatic on clean airframes said that mod alone is probably good for several mile per hour. We'll see. Another thing is he says is, "add as little weight as possible when making drag reduction improvements."

I'll shoot some "proper" sized pictures and post.

Darwin N. Barrie
P19
 
Hey darwin,

I just saw an rv the other day with the ends of the h-stab and counterweight areas filled in like yours. How does one go about filling them in? I'd like to do it, but am a little concerned about the fillers coming loose at the wrong time.

Steve Zicree
RV4 finishing
 
Aden Rich said:
My RV-6 goes 218MPH wide open. It has 190hp, a scoopless cowling, constant speed. prop, tight intersection fairings, wheel pants, a well fitted canopy and shear wingtips. It's also a very clean and a well rigged airplane. But the one thing I wanted to try to do it make it practical. Speed is nice but usually when you try to get more speed you loose usefullness. Plenums, tight cowls, gap seals, fairing over small protrusions, increasing HP, stuff like really subtracts from Van's idea of simplicity.
Click to expand...

Are you saying that the mod's that you've made (no scoop) and where you've exceeded Van's max recommended hp and speed for the 6 are the only 'practical' deviations from Van's vision?


Aden Rich said:
Beside the wings on RV's hit a giant wall of drag at 200mph. If you want to go really fast, change the wing, install 260hp and you can go 265, land at 100mph and not climb as well.
Click to expand...

Dave's plane does 250+, climbs at 3300fpm and lands the same as a -4 with a 4 cylinder engine. I'd estimate that less than half of his speed gain is from power increase, the rest is from detailed drag reduction (weight reduction has a very small effect on speed e.g. 160lbs = -1mph). The Rocket clipped the wings and has around 300hp and still got crushed in the CAFE by a guy who did his homework on his aircraft mission...

Aden Rich said:
Van's has done their homework to offer a airplane that gives the best of all the worlds. Speed, beauty, utility, slow flight, handling,easy to put togther and most of all lower cost than most other airplanes.
Click to expand...

Who's world? Nothing gives the best of all worlds.

Low cost is great for selling kits but not all builders are trying to fly on the cheap. Keeping it simple keeps the cost low and reduces build time, but not everybody wants to fly the cheapest simplest plane built in the fewest hours.

I'd really like to hear what people have done to increase power, decrease weight and drag regardless of how long it took to build or how much it cost.

Chuck
 
Speed mods

szicree said:
Hey darwin,

I just saw an rv the other day with the ends of the h-stab and counterweight areas filled in like yours. How does one go about filling them in? I'd like to do it, but am a little concerned about the fillers coming loose at the wrong time.

Steve Zicree
RV4 finishing
Click to expand...

Hi Steve,

I scuffed everything in the channel as best I could, cleaned it thoroughly and then cut some structural foam to fit with it hanging over slightly. Mix some micro balloons and epoxy into a thick mixture. Generously apply to the channel and push the foam in. Once cured block sand the foam flush to the metal. I used 1" wide glass cloth over the edges and let it cure. Then I cut an over sized piece of cloth and covered the entire width. Once cured I sanded off the excess cloth from the edges and sanded the other cloth surfaces.

Now is where you get the look. Mix some micro and epoxy, fairly thick, and apply with a squeegee to fill any low spots. Do this on the channel side and top and bottom of the surface. Block sand until you think you have it smooth. Get some gray sandable primer and spray the area. Block wet sand. This will expose bad areas. This is an iterative process but the results are worth it. Once you get to a point of spot filling, I use Glaze filler. Continue this process until it is perfect or you can live with it.

I'll send some photos if you are interested.

Darwin N. Barrie
Chandler AZ
 
Maybe you could sneak into an ANG base and snag a few of those JATO assist rockets they use on the C-130's to help them get off the ice quick...Maybe two under each wing should get you to 400mph or so in not too much time ;)

Wouldn't reccomend it, though...

I'm actually really interested in this. If racing cars has taught me anything, it's that all the little things add up. Reducing drag is an excellent place to start, but I'd also be interesed in knowing what kind of things you can do to the engine without adding too much extra fuel. Can parts be lightened or balenced better? Can you port/polish heads and intakes? Anything?
 
Drag reduction is the way to go

xl1200r said:
Reducing drag is an excellent place to start, but I'd also be interested in knowing what kind of things you can do to the engine without adding too much extra fuel. Can parts be lightened or balanced better? Can you port/polish heads and intakes? Anything?
Click to expand...
Reducing drag is the easiest most efficient way to gain top speed.

I don't think the mods you give as examples on a Lyc will give much return on a 2,700 rpm engine. Balancing has limited effect and almost none on HP. If Carburated you don't want the intake ports too smooth because the roughness keeps the fuel atomized. Also porting the head area, removing material has some major draw backs, like cracks. The heads don't have a lot of extra meat, but if you must Lycon could help you.

Other proven and time honored Lyc mods: Higher compression, yes; Electronic ignition, definitely; Run at higher RPM, yes, every 100 rpm is worth 3-5 hp. (Lycoming warns against RPM greater more than 5% over red line, and even than only inadvertent and momentary. Of course racers fly into the 3,000 rpm range. Than the prop is an issue? The Hartzell I have is good for (by type certificate) 2,900 rpm with 180 HP engine.)

Bottom line HP does not add much top speed. 10 hp may only give you 3 mph, where simple clean ups can get that much with out burning more fuel.
 
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Let's try this...

It seems the go fast guys at some point always pump up the engine thereby clouding the effect of the other mods. With that in mind......

How about we talk Dave Anders into putting a stock carb'd O-320 back in his RV4. Then we can take his speed numbers in this configuration and compare them to Van's stock data.

Now THAT would be enlightening.

John
 
gmcjetpilot said:
...A fixed pitch can get higher top speed by over-rev of the engine. (The Reno formula races rev to crazy RPM's.) More Revs = more HP=more speed (withing limits).

I have heard good things about CATTO performance, and one negative thing regarding a structural failure.

Cheers George
Click to expand...
The one negative I found (Search this forum, it is here) related to a Reno racer running at those crazy RPM's. A blade was thrown, resulting in a crash.

Traditional wisdom is three blades are better in climb than two but two are better in cruise. I believe this is due to the extra blade.
 
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Yes to SJ Cowl, Plenum, Pants, Archer too

I know of one or two people with -8's who had trouble fitting their cowls. Maybe they were earlier models. I think my SJ cowl fits pretty well and I'm not skilled with glass. The plenum was worth it and not difficult. Here in Michigan on a warm day my oil temp is 180. Today at 31 deg. it was 140. I will actually have to mask it off. It's the el cheapo from Van's. The engine is Superior XP-IO-360+ . My greatest spread on CHT is 20-25 deg and I haven't even implemented Sam's recommendation on the lower shroud gaps yet. I also need to adjust the front dam on the right side. It's #1 and #3 with the greatest spread. Bottom line is that I'm using less air and getting better cooling than with standard cowl.

My Archer wingtip antennas are 50-50: VOR best I've experienced. COM - not acceptable for XC and I will be putting in a bent whip on the belly. COM practical range is 20 NM or less and works better going away from the station. I installed it at an angle to get all the available vertical polarization. Radio is an SL-30. The avionics shop checked for standing wave ratio and reflected energy and said it was good. It's just that you can't get a good COM signal in and out without better vertical position.

I cannot be certain because my fairings are not on, but I'm getting a true 156 kts at 2690 rpm at DA 9000'. Prince P-Tip FP composite prop. I also have big brackets on the wheels which will hold the pants eventually. If I get 20 kts from fairings, that will be 176 kts= 202 mph at 75% or less. I think I will have to adjust the prop some, too, so the results may go up. Van's numbers for this airplane: 197 mph.

PS - I left off the steps for whatever that is worth in knots.

Yours may vary, as they say.
 
Why no negative ("reflex") flaps?

Ok, dumb question: Why don't RVs use negative flap settings to get more speed in cruise? I've been flying a CTSW recently and it uses -6 flaps to increase cruise speed. Some sailplanes also use negative flaps.
 
the_other_dougreeves said:
Why don't RVs use negative flap settings to get more speed in cruise?
Click to expand...
The short answer is that you wouldn't get anymore speed. Negative flap settings are useful when you have a highly cambered airfoil which RV's do not have. If I had to guess, I would say a negative flap setting would actually increase drag on an RV.
 
John_RV4 said:
It seems the go fast guys at some point always pump up the engine thereby clouding the effect of the other mods. With that in mind......

How about we talk Dave Anders into putting a stock carb'd O-320 back in his RV4. Then we can take his speed numbers in this configuration and compare them to Van's stock data.

Now THAT would be enlightening.

John
Click to expand...
Make it simple...horsepower means fuel burn. In this year's AirVenture Cup race, Dave Anders went 244 mph over the 410 nm. I went 210. After the race, I talked to Dave, and he told me he burned 35 gals total. I also burned 35 gals total. So, his airplane has that much less drag than mine.
 
I believe the RV-10 has some negative flap. I assume it is for cruise speed puposes. Anyone? Alex D.?

Joe
 
Engine mods cost money, airframe mods save money?

John_RV4 said:
It seems the go fast guys at some point always pump up the engine thereby clouding the effect of the other mods. With that in mind......

How about we talk Dave Anders into putting a stock carb'd O-320 back in his RV4. Then we can take his speed numbers in this configuration and compare them to Van's stock data.

Now THAT would be enlightening. John
Click to expand...
That is a fair point. You are right the REAL go fast guys are pumping their engines up. Dave's RV-4 is NOT a daily flyer. He also overhauls his prop and engine very frequently as a preventative measure. He is a dentist and makes some coin. I understand he (rumor mind you) he does dental work for "Lycon", California custom high performance builder, getting quid pro quo engine work or at least a discount. Any way Dave's IO360 makes crazy high power, well past what most people are willing or able to do.

Anyway Van wrote a little article on Dave's plane with a little pencil paper analysis breaking down what and where the speed came from. I don't have the article handy but it was interesting.

My guess is Dave's engine puts out say 230 HP? Guess but taking stock numbers he should go. A stock RV-4 with 180HP is listed at 212 mph top speed.

212 * (230/180)^.33 = 230 mph.

So he gained 18 mph over a stock 180 hp engine.

If his top speed record is 250 mph, 20 mph is from airframe modifications?

To answer you question a O-320 (Carb of FI makes little diff) a stock 160 HP RV-4 has a listed top speed of 205 mph. Assuming the airframe mods would give you 20 mph as I estimate Dave's RV-4 mods did, the top speed would be 225 mph!!!! That is 225 mph on 160 mph. THAT'S VERY POSSIBLE AND REALISTIC. Sam James claims 8 mph for the cowl alone.

Kent Paser ("Speed with Economy) claims he got his Mustang II up to a 239 mph top speed. He started at 175 mph. The Mustang II is a good plane and has a lower drag high speed wing. Of course it does not fly as nice as a RV from what I have been told. Van flew Dog fights against one and waxed the Mustang II's tail. The RV can make tighter turns and pull ups, while loosing less energy, no doubt in part due to the NACA 23013.5 wing. Also the Mustang II does not have the STOL abilities of the RV.

Airframe and cooling drag reductions is fertile ground and ripe for harvest. Engine mods are not fruitless, but they are very expensive and have significant effect on engine life and fuel economy.

Sure you can go faster with BOTH airframe drag reduction AND engine increase. However the engine Dave has is very HOT, and he has had to tear it down a few times over the years at less than TBO. I am not sure all where voluntarily, meaning the engine was continued modified or was showing early signs of distress. Dave is a perfectionist so if its not right he will take it apart. Most of us don't have to money to overhaul engines any old time.
 
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Go Fast?

Tailwind! I averaged 225mph from ABI to JYL last Saturday, with a fuel stop. A 35 to 40 knot tailwind is the best speed mod ever!

All joking aside, I am Pierre's buddy with the PITA James Cowl/Plenum. Two words: NEVER AGAIN! If you want details on the James stuff, call me. Too long to put in writing and I do not want to turn this into a flame. Just for the record, I plan to use a showplanes cowl and a Barefoot Billy pleunm on my 8 currently under construction.

Still waiting on the Van's RV-8 Fastback yeah or neah.
 
<<Still waiting on the Van's RV-8 Fastback yeah or neah.>>

Robby, yeah or neah on what aspect? If you're considering a Showplanes fastback kit, I have one fresh off the truck. You'll welcome to ride over here and check it for quality or whatever.

Dan Horton
Montgomery AL
(based 08A)
 
Hard Knox said:
...
All joking aside, I am Pierre's buddy with the PITA James Cowl/Plenum. Two words: NEVER AGAIN! If you want details on the James stuff, call me. Too long to put in writing and I do not want to turn this into a flame. Just for the record, I plan to use a showplanes cowl and a Barefoot Billy pleunm on my 8 currently under construction. ...
Click to expand...
Robby's was, Will James admits, an early one. Now my count of two with bad experiences is back to one. Mine (-7A) was good. Newest version is probably better. I don't blame Robby for his POV, but I'd do it again. Different strokes...
 
Mod stock cowl and baffle kit?

There is always making your own low drag cowl and sealed plenum from a stock cowl and baffle kit. That may not be easier but is the way I am going and in progress. I just liked the new Van's epoxy cowl too much to switch to the James cowl. Besides James did not have a short cowl and I was committed to using a standard compact hub Hartzell. As far as the plenum it's easy to put a stiffened metal top on the baffle kit and form a fiberglass transition between the plenum and cowl (rings), with a piece of inner tube or wet suite as a flexible connection. If it was not mentioned, Randy documented his trials and tribulations with the James cowl on his web site: http://www.romeolima.com/RV8/Cowl.htm
 
George-

Can you post some pics of your progress? I am interested as I do not want to use an extended cowl on my -8. Alternatively you can email me at tmshort_at_gmail.com

Thanks

Thomas
 
SJ Cowl - short

Just FYI - The James Cowl is available in "short" version - same length as Van's I believe.
 
Grove gear

txaviator said:
I'm sure Jay Pratt will offer more info on this, however, his recent reports about using a Grove Gear were very intriguing to read. Supposedly it makes a world of difference to use one.
Click to expand...
I'm thinking of Grove Gear. Any more info on this?
Jay, you out there?

Cheers,
 
TShort said:
Not for the -8 ... at least I don't think it is.
If so, that would be great!

Thomas
Click to expand...

You're right, Thomas...see below copy of email:

Zzoom
RV8QB
Wiring


Hi Roy,

You are correct. I believe the Catto prop is a standard wood hub
dimension propeller and would require a 4" extension with our RV-8
cowling. Thank you for your interest none the less and good luck with
your project.

Liz

RC Lewis Jr wrote:
> /Hi!
>
> I believe I was told that you only have the long cowling, for the RV8,
> necessitating a long prop extension./
> /My engine is an AEIO-390 forward facing injector using a Catto prop.
> I do "not" want to use a long prop extension, so if the cowl will be
> available only in the "long" version, I guess I can't use it. I
> believe my Sabre extension is 2 1/4in?/
> //
> /If the cowl is available in the Van's stock length, please let me know./
> /Thanks!
> Roy/
 
Negative flaps.....

You guys with the aerobatic wings are trying to get what is built into the RV-9/9A and RV-10. The wing there is a Roncz airfoil. The front of it is a bit steep, but the reverse curve across the top of it does what you are trying to get with the "negative" flap position. Like the man said, a tail wind always helps, and I try to fly all my cross country trips above 10,500 MSL to catch a tail wind. The true airspeed for my heavy RV-9A is around 160 MPH using a 160 HP O-320, and a Hartzell CS prop at 2300 RPM. It will go faster at the expense of more fuel burn, but I am happy with 5.5 to 6 GPH at 160 MPH TAS way up high and lean.

Jerry K. Thorne
East Ridge, TN
RV-9A N2PZ
Hobbs = 210.2 hours
 
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