ZU-RVFour

ZU-RVFour

Active Member
Other than HP has anyone had any success with any easy fit speed mods. I use the -4 as a weekly commuter (and fun fly on odd occations:rolleyes::rolleyes::rolleyes:) so it works and has collected a couple "scars". Unprepared ground strips are not soft on the tight fitting wheel pants/spats and communal hangarage has left a couple dents and scratches. I am looking for maybe 5-8kts on the top end without redesigning the plane or having huge amount$ of downtime.... Thus Couple questions reagrding fairings... (please).
Has anyone fitted the fuel drain fairings with any success?
Has anyone fitted the tailwheel fairing with a full castoring tailwheel (Stainless steel Rocket steering link)?
Aileron and/or flap fairings worth the effort?

My mate has an O-360 fast back with a 3 blade MT prop and Sam Jones cowl and I keep up OK so am thinking that huge re engineering (cowl, fast back, new prop etc) is not solution. Empty is just over 1000lbs... IO-360 with Hartzell CS prop.

Reason for my question is I have taken to racing my -4 in the local derby and had limited success first time out. It an annual 650nm hop over 2 days. 325nm a day. From standing start we avg'd 175+kts which included a couple detours (mainly due to dice with a Seneca which lead us astray). While I am sure we will be handicapped outa sight next time out I would like to chase down/keep up with my mates in their beeeg bucks SR22 and the C210T....:D:D:D:D. They tend to get around 180kts from said standing start so we are not far behind and I am hoping a couple small tweaks could help...

PS
Handicap Air racing is huge amounts of fun and for the last couple years we have had a full field of 100 aeries. Below a pic summary of the most fun you can have with your headset on in our part of the world.... http://www.sapfa.org.za/race_main.php
my.php
[/URL] [/IMG]

Thanks in advance for any comments.....
 
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Hoe Gaan Dit?

George,

It's not one single mod, but a combination of several little ones that increase speed. The numbers you are posting are impressive, almost Rocket numbers. I flew my very stock 150HP RV4 for 10 years/1400 hours with no special speed mods. It performed very well and though the 180 HP guys could slowly pull away in a race, I never lost sight of them. When I wanted to get their goat I would invite them to follow me home and land on my 900' (300M) strip. I always won that one...it's not about how fast always, how slow is also important. A buddy installed a full set of James plenum/cowl/pants/wing fairings/tailwheel. I raced him before and after with almost no change. I later installed a 175HP engine and Gary Hertzler prop on my airplane and gained 15 knots at top end. HP definitely helps, I don't think you will get much more top end from yours without major mods or large amounts of Rand.

In my humble opinion the prop is the biggest speed mod you can change, I tried a total of eight over the years. Van's Pressure recovery wheel pants are a guaranteed 5 knots increase. The fastest RV4 on earth is Dave Anders. His aircraft has a number of mods including a 220 HP engine and special Hartzell prop. He has everything including the flap and aileron hinges faired, gap seals, riveted trailing edge control surfaces, fast back and plenum. You can read about his airplane in the CAFE reports link below. Of course, the RV4 VNE is still 210 MPH. Anything beyond that you are a test pilot.

Good Luck, next time you head south, stop by my friend Johan's strip near Clanwilliam!
Sien Ya!

Smokey
HR2

http://cafefoundation.org/v2/main_story.php
 
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There is an article on this subject in the january issue of the EAA rag, "sport aviation", so try to get a look at that for some simple ideas. They seemed to emphasize reducing the gaps between surfaces, like spinner/cowling gap, spinner/ prop, etc.

erich
 
Thanks guys... Have seen Dave's posts, but these are too drastic for my ability and budget... Am going to play with fiberglass (aaarg) and see what happens...
 
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Maybe Mods

I have an RV-6A that I have been modifying over the past 5 years to gain more speed. Many mods do no good so you have to consider taking them back out as you put them in. I do not know how the inside of an RV-4 cowl works so I have nothing to say about that except by working with the air flow in the lower cowl with baffling I was able to pick up my largest speed gain - 4 kts. This was after many dismal failures. "Close all the holes and remove or fair in all of the protrusions" is a good general objective in your experimenting. Three things I did may work on your RV-4, shorten the wing span by building new tips, use gaffer's tape to close the attachment access openings in the elevator and rudder (much more difficult than it sounds) and add subfairings to the wheel fairings down to 3/4" above the ground and minimize the tire gap (may be dangerous on a tail dragger).

I read the article on speed mods in the January 2009 EAA Sport Aviation and I think it was heavily edited or the writer didn't really have anything significant to say. A book that I found very interesting is "Speed With Economy" by a man named Kent Paser.

Bob Axsom
 
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Bob Axsom said:
I have an RV-6A that I have been modifying over the past 5 years to gain more speed. Many mods do no good so you have to consider taking them back out as you put them in. I do not know how the inside of an RV-4 cowl works so I have nothing to say about that except by working with the air flow in the lower cowl with baffling I was able to pick up my largest speed gain - 4 kts. This was after many dismal failures. "Close all the holes and remove or fair in all of the protrusions" is a good general objective in your experimenting. Three things I did may work on your RV-4, shorten the wing span by building new tips, use gaffer's tape to close the attachment access openings in the elevator and rudder (much more difficult than it sounds) and add subfairings to the wheel fairings down to 3/4" above the ground and minimize the tire gap (may be dangerous on a tail dragger).

I read the article on speed mods in the January 2009 EAA Sport Aviation and I think it was heavily edited or the writer didn't really have anything significant to say. A book that I found very interesting is "Speed With Economy" by a man named Kent Paser.

Bob Axsom
Click to expand...

I don't think shortening wingspan my modifying the wingtips will help that much. Dave Anders is using the first generation "sheared" wing tips which actually add a small percentage of wing area. These tips are available from Vans as stock on newer kits. As Bob mentioned cooling drag is usualy the big culprit in stock airplanes.
YMMV
tm.
 
rv-4 speed

You won't find much speed in those high dollar aftermarket items in my opinion. Smokey hit the nail on the head with the prop. If you want it to go fast make it lighter and get a good efficient prop. It sounds like it does ok now. If you turn up the rpm's you will get a little more hp. If you want to see
some real speed numbers go the sportairrace.org and browse the race results.

Chris Murphy race 34 rv-4
 
A Little more Info on the Tips and Tires

IMG_3233.jpg


This is a photo taken of my plane taken after the last 2008 race at Taylor, Texas. If you should decide to try the span reduction and wheel sub fairings here are a few comments:

Wingtips:

1 - I made the tip molds out of 3/4" plywood for the base and pieces of 2x4s band sawed to a little oversized shape and glued to the base plywood and adjacent 2x4s. The molds were planed and sanded to final shape, painted with polyurethane, waxed with mold release wax from Aircraft Spruce and mounted on a work table made out of 2x4s and 3/4" plywood with galvanized steel pipe and end mount plates bought in the plumbing supply section of Lowe's.

2 - The shape of the tips viewed from above is a duplication of the lower surface of the airfoil. The front view shape is a rounding off from the top and bottom.

3 - An 0.016" 2024T3 aluminum stiffener/closure plate is pop riveted into the rear of the tip opposite the aileron with the flanges pointing into the wing tip. This eliminates the pocket created in the standard stiffener installation.

4 - The tips are 3 layers of glass cloth and EZ-Poxy resin using 24 hour hardener.

5 - I used a mix of floating and non-floating platenuts riveted to the the inside of the tips with a narrow 0.016" aluminum doubler strip sandwiched between the fiberglass and the platenuts. The required plate nut rivets are all that hold the aluminum strip in place.

6 - The tip mounting holes are 3/8" in diameter to accommodate the existing dimpled wing skin mounting holes.

Wheel subfairings:

1 - I bought modeling clay and shaping tools from Hobby Lobby and created a mold right on the airplane between the existing fairings and the tires.

2 - The existing fairings, the clay and the tires were covered with mold release wax and I applied the first layer of fiberglass and EZ-Poxy right there in the hangar on the airplane.

3 - After curing I jacked up the plane and removed the first layer of the subfairings and took them home to finish in the garage. I made some simple stands to support the parts off the bench but the remaining 2 layers were applied without molds.

4 - The subfairings were cut in two at a rearward angle and a three layer overlapping gap closure flange was added to the front half.

5 - I used the existing hardware for the side mounts but I added one plate nut at the front and one at the rear of the existing fairing. The mounting holes are all 3/8" in diameter and the mounting hardware is #8 stainless steel screws and dimpled washers.

6 - The subfairings can be removed for non racing situations but so far I have left them on.

Bob Axsom
 
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Seal the rudder and elevator hinge lines?

The one simple and cheap speed modification I have been thinking about is this. I come from the glider/sailplane world where all the control surfaces have gap seals.

I have been wondering if putting mylar tape down the rudder and more importantly, elevator hinge line, to seal up the gap, would have a noticeably beneficial effect. Has anyone experience of this?

On a -4 the flaps are sealed by the hinge and the ailerons I presume are designed to have the gap, but at the backend any flow through is leakage which must surely reduce efficiency.
 
Not really

smokyray said:
Removing that nosewheel might help too....:)

Smokey
HR2
Click to expand...

The subfairing on the nose gear was extremely surprising - it alone increased the speed by 3 kts. I haven't been beaten by a side by side tail dragger since that went on. I suspect the that dirty skag hanging off the back of taildraggers even at the high speed angle of attack causes as much drag as my nosegear. There is no way to really tell but the race results seem to bear that out. If you get a chance to look at the Bruce and Steve Hammer's super fast Glasair taildraggers you will see that they have the tail strut and wheel faired to form a single streamlined protrusion with a single pivot line extending into the slipstream. Most taildragger builders don't go that extra distance to figure out how to do this and actually implement it. Of course if you look at the photo of the RV-4 of the man that started this thread you will see that there is a lot of main landing gear tire showing in the stock configuration which indicates potential speed gains are present. I have all three tires tightly faired down to 3/4" from the ground and special chocks made of 3/4" aluminum angle are visible in the photograph of mine. Surprisingly, I saw very little gain in speed from the subfairings on the MLG (they are the newer design while the NLG fairing is the old semi-flat sided model) but they are there for what I can get out of them.

Bob Axsom
 
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Roughing it...

Bob,

Absolutely, every bit of fairing helps, unless you have to complete your mission on my 1800', very rough strip. That's where utility outweighs a knot or two of speed. Suprisingly, going to larger tires and opening up the Van's PR wheelpants didn't rob me of one knot of speed. The obvious best scenario would be to eliminate the gear altogether, retracting it with the weight penalties, complexity and maintenence. My answer was to keep my rough field capability and solve the speed problem with horsepower, lots of it!

Good on you for figuring out ways to go faster, I have to figure out ways to go slower...:)

Smokey
HR2
 
ZU-RVFour said:
Other than HP has anyone had any success with any easy fit speed mods. I use the -4 as a weekly commuter (and fun fly on odd occations:rolleyes::rolleyes::rolleyes:) so it works and has collected a couple "scars". Unprepared ground strips are not soft on the tight fitting wheel pants/spats and communal hangarage has left a couple dents and scratches. I am looking for maybe 5-8kts on the top end without redesigning the plane or having huge amount$ of downtime.... Thus Couple questions reagrding fairings... (please).
Has anyone fitted the fuel drain fairings with any success?
Has anyone fitted the tailwheel fairing with a full castoring tailwheel (Stainless steel Rocket steering link)?
Aileron and/or flap fairings worth the effort?

My mate has an O-360 fast back with a 3 blade MT prop and Sam Jones cowl and I keep up OK so am thinking that huge re engineering (cowl, fast back, new prop etc) is not solution. Empty is just over 1000lbs... IO-360 with Hartzell CS prop.

Reason for my question is I have taken to racing my -4 in the local derby and had limited success first time out. It an annual 650nm hop over 2 days. 325nm a day. From standing start we avg'd 175+kts which included a couple detours (mainly due to dice with a Seneca which lead us astray). While I am sure we will be handicapped outa sight next time out I would like to chase down/keep up with my mates in their beeeg bucks SR22 and the C210T....:D:D:D:D. They tend to get around 180kts from said standing start so we are not far behind and I am hoping a couple small tweaks could help...

PS
Handicap Air racing is huge amounts of fun and for the last couple years we have had a full field of 100 aeries. Below a pic summary of the most fun you can have with your headset on in our part of the world.... http://www.sapfa.org.za/race_main.php
my.php
[/URL] [/IMG]

Thanks in advance for any comments.....
Click to expand...


I have a new RV4 (-MUMY) Superior XP IO 360, Hartzell blended airfoil CS prop. I have Lightspeed Elec Inition instead of the right hand Maggi. Top speed, gps tested several times at all hights and wind conditions, plus checked on both my steam driven 3 1/4 ASI and Dynon EFIS, shows 189kts, 215mph. ( of course after testing I never deliberately exceed the VNE). Weight seems to have little to do with it as my aircraft is H E A V Y! 1117lbs. This is due to the fact that I have fitted everything and chips to the aircraft. Including;- Side panels in the cockpit full of switches and stuff, strobes, nav lights, landing lights, centre console, two radios, two installed GPS's, autopilot, alt hold, Dynon, IK tech engine monitor, MP3 player, carpets, elec flap system, ATC clearence recorder, ASI and throttle lever in rear cockpit, and a heavy customised paint job. After 44 years of flying and 65 years on the planet, for me aero's are a thing of the past. Like many I built my 4 as a fast tourer. I think the electronic ignition and the fact that the engine had extra balancing during assembly by Eagle Engines is responsible for the extra UMPH! If you havn't done so already I think you could do worse than try a the Lightspeed stuff. As I said, I use one Lightspeed unit. I have kept the Port Mag for the wife and kids (Total power failure and electronid IG does not mix).
Happy Landings

Stan G-MUMY
 
Yes......

rjtjrt said:
Has anyone tried converting tail wheel to a tail skid to get extra speed?
John
Click to expand...

.....on a Cassutt I built. Just completely remove the whole TW assembly and fab a skid. My Cassutt had a leaf spring off a small car for a tailspring. I drilled a hole for a 1/2" bolt and added a fabbed up tailwheel fork and wheel. For racing I removed it. It will slide around with brake and there's plenty of rudder available.

FWIW, we've had several Agwagons completely break the tailspring on landings and they're still quite controllable with brake and rudder.

Regards,
 
Not the only game in town...

The Lightspeed ignition is OK and works fine but I have installed the Electroair Ignition alongside a Mag in 3 RV's with outstanding results. Jeff Rose's original design provides smooth operations, increased fuel economy and no mag drop as well as more HP. 10 times the spark volume (compared to a mag) and a longer burn over the stroke of the cyllinder equate to more efficient burn and power! I installed the original system in my RV4 in 1997, it now has 1300 hours! The new systems are even better.
With six cyllinders, it really makes a big difference.

Smokey
HR2
www.electroair.net


My Rocket weighs about the same as G MUMY!
 
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rjtjrt said:
Has anyone tried converting tail wheel to a tail skid to get extra speed?
John
Click to expand...

Not a tail skid but I had a skateboard wheel housed in a model airplane wheel fairing and fly it without springs. It was the last modification that I tried and I could not measure any performance gain. ymmv
tm
 
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