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Rotary Engine (Mazda/Wankel) conversions Hummmmmm!

R

Rotary10-RV

Well Known Member
As I have been rather long winded about the rotary in another thread I figured I would be true to my word and start a thread about rotary conversions. There are several types of aircraft already flying with a rotary engine. The list (and I'm sureI've left some out) RV's mostly 6's, Long EZ's several, The most interesting being that of Perry Mick who designed his own ducted fan and ran the rotary direct drive! Sadly or gladly he has since converted to a standard PSRU and pusher prop. Several of the Zenith designs are running rotaries. The biggest contributor to the rotary cause so far has been Tracy Crook (who fortunatly isn't). Tracy sells an engine control module with redundant controls for injection and ignition. Also two different PSRU's or re-drives as he likes to call them. Tracy has over 1000 hours on his RV-4 conversion. Tracy recently installed the new 2 rotor engine out of the RX-8 sports coupe called a Renesis by Mazda (Yea I know the name is weird but the engine runs verywell) He is also bulding an RV-8 as a test bed for another version of the rotary called the 20B which has 3 rotor chambers and was used on larger sedans in the japanese home market. the engine is a natural for aircraft since it is 50% larger. This is the engine about which I'm basing my own conversion. I'll be running the 20B engine in my RV-10 once completed. Mistral Engines in Florida is producing a 2 rotor that is to be CERTIFIED which will surely help the rotary in the eyes of the insurance companies. Fortunately Mistral is also going to sell parts to the homebuilder market. The reason I'm interested is that their PSRU is designed for high HP and is setup for the use of a hydraulic constant speed prop from the outset. In fact they are running this engine in a Piper Arrow now preparing for certification. The RV-10 has a wide speed range and I expect that using a CS prop is really almost a necessity. I would be interested in Tracy's unit which is much cheaper if it could accomodate a standard CS, but so far this hasn't been a priority with Tracy, he has a great deal of business already. An MT electric prop is always a possibility but is very expensive. That is a start for rotary conversions which IMO show a great deal of promise.
Rotary10-RV
Bill Jepson
 
Im with you- the Rotary looks to be an excellent aircraft motor based on reliability, durabiity, power to weight, and probably, fuel burn rates. My only comment is that the Renesis 2-rotor motor might be a better choice for your RV-10 at 230-259 HP output (in the recommeded power range, with less weight than the Lyc). You could always add a turbocharger if you need more HP later on. I dont think you will be able to convert the extra HP to speed in a 10 with the 20B, only burn excessive fuel and generate excessive heat in the process.
 
cobra said:
Im with you- the Rotary looks to be an excellent aircraft motor based on reliability, durabiity, power to weight, and probably, fuel burn rates. My only comment is that the Renesis 2-rotor motor might be a better choice for your RV-10 at 230-259 HP output (in the recommeded power range, with less weight than the Lyc). You could always add a turbocharger if you need more HP later on. I dont think you will be able to convert the extra HP to speed in a 10 with the 20B, only burn excessive fuel and generate excessive heat in the process.
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Cobra,
Reasonable comments to be sure. The 20B and 13B as well are NOT gas guzzlers in high power and high RPM use. The comment I made about the rotary being a better aircraft than car engine? The engine is more and more efficient at higher outputs, (relative to other engines), in fact Mistral is reporting slightly better fuel burn than a compareable output Lycoming. I have chosen the 20B as producing the required HP easily, rather than a higher tuning level needed for the 13B. On the weight issue the raw 20B weighs in at 295 lbs which still allows for 100+ pounds for plumbing and accessories. There are several current efforts to build and replace the iron end and intermediate housings with aluminum ones. If successful the weight savings will be drastic, 40 pounds on my engine! The 13B would save about 27 pounds. The rotary is progressing and getting better the more effort that is applied.
Bill Jepson
 
I've been lurking on the FlyRotary list for a while, and I'm kind of torn between going totally stone-age with a carbureted O-360 and 2 magnetos or building out the simplest possible Renesis installation, that is, NA 4-port with RWS redrive and ignition controller. The biggest issues that seem to be facing the rotary aviation community so far seem to be cooling, intake, and exhaust. This is because there's no best or only way to do any of them. There are plenty of ideas and examples out there and most of them work just fine, but each one is unique. This being my first homebuilt airplane, I'm not sure if I have the chops to put together a nonstandard installation which isn't recommended or endorsed by the kit manufacturer. On the other hand, I could take the savings from the rotary installation and put it in the panel.

Still (not)deciding.

PS, I don't mean to ruffle any feathers. I realize that a successful installation of this kind is cause for celebration and respect. I'm also hoping that by the time I'm ready to look for an engine, all the parts I need for a rock-solid plug and play rotary conversion will be available, and that will make the decision easier.
 
John Courte said:
... The biggest issues that seem to be facing the rotary aviation community so far seem to be cooling, intake, and exhaust...
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I too am thinking Renesis and I have some very specific ideas on how to approach the cooling challenges.
The oil is a major contributor to total engine cooling because of the heat transfer through the rotors. If you can get a handle on that, you can whip the whole problem. Focus on increasing oil flow through the oil cooler(s).

-mike
 
Both water and oil cooling are important on the Wankel. The heat exchangers and ducting are critical for success and low drag. Powersport has done a nice job of this on their 2 RV8 conversions with the single inlet, divergent, under spinner duct. Bill Kay could offer some advice on on heat exchangers. Don't underestimate the task of keeping one of these conversions cool.
 
Planning on a Renesis with a Catto 3 blade. I think that the cooling issues are being dealt with by several that are already flying (Tracy, Dave, Paul, among others). These guys are essential to those of us in the planning stages, and I do believe that there will be something close to a "plug n play" install avaibable in the near future (couple of years).

Keep thinking. We'll get there, and it'll be great!!
 
Cooling the Rotary

Fellow Experimenters,
Cooling the Rotary isn't much different than cooling any other water cooled engine. You need diffuser ducting to slow the air prior to the rads, (water or oil), and good exit area (an often ignored item) with low restriction. The rotary does have a slightly higher oil cooling component than the typical piston rengine, as a percentage of it's overall thermal package. About 20-30% for those interested. You will need 2-3 cubic inches of heat exchanger per HP on the water radiators. For oil I would try to use the standard Mazda coolers if they will fit. They are an excellent cooler when tested.
I'm building an RV-10 which has plenty of under-cowl area. My plan is to run 2 radiators toward the sides of the cowl with a standard Mazda racing oil cooler under the engine toward the rear. Near standard inlets will be ducted to the radiators and oil cooler. I plan to sweep the exhaust under the engine and exit centrally in a single centered outlet. Engine mount will be bed style supporting the engine in three points a la Questair Venture.
Bill Jepson
 
Bill,
Question concerning your cooling ducts that "slow down the air". Tracy Crook had problems with his ducting at first because turbulent airflows reduced the cooling efficiency, at least before he radiused his inlet ducts into a venturi. I think you misread the comment, the idea is to provide as much air as possible, without turbulence, until it gets to the radiators, not slow it down. Slow turbulent air does pass thru dense radiator cores well.

FWIW, my very sketchy plan at this point is to place twin radiators on each side of the engine then build a streamlined scoop underneath the spinner, much like the Rockets do, to provide air to the oil cooler and the intercooler. The heated air will leave by (and cool) the turbo/muffler/exhaust pipe around the front wheel strut, below/behind the motor.
 
cobra said:
Bill,
Question concerning your cooling ducts that "slow down the air". Tracy Crook had problems with his ducting at first because turbulent airflows reduced the cooling efficiency, at least before he radiused his inlet ducts into a venturi. I think you misread the comment, the idea is to provide as much air as possible, without turbulence, until it gets to the radiators, not slow it down. Slow turbulent air does pass thru dense radiator cores well.

Cobra,
I do NOT intend to induce turbulence in my ducting. If you build a smooth sided DIVERGING duct the airflow will slow (more area) naturally. There are several texts on this. There was a well established wedge shaped duct that give uniform flow. K&W testing heat exchangers.
Bill Jepson
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Divergent ducting with a smooth transition not exceeding 6 degrees has shown to be the best. Converging the flow after the rad may help to recover the velocity before dumping it back out into the freestream. The front mounted rads used by Tracy Crook and Eggenfellner are there for packaging and ease of installation, not efficiency. The short duct length MUST cause poor pressure recovery and dumping the exit flow into the turbulent cowling flow causes higher drag. These installations cool because of high rad surface area and volume, not because they are great designs. The tight fin and tube spacing of GM evaporator cores has shown to offer high drag per unit volume and poor heat rejection at typical RV climb speeds. They work ok at higher speeds as far as heat rejection goes.

They do work and the front mounted rads keep plumbing short and solve many packaging problems on the RVs with deep spars. The cowlings can be kept near stock also. These are real considerations as well for any installation.

For the lowest drag, a proper divergent/ convergent duct would be used with an inlet area 25% of the rad face area, as the flow diverges, it slows down and gains pressure. Pressure differential is one of the most important factors in heat exchanger performance. The rad core needs to be relatively open with widely spaced oval (not flat) tubes for lowest core drag. Flow would then converge through a sealed duct, exiting through a controllable exit door with areas adjustable between 50-150% of the inlet area. This allows matching of flow velocities with the freestream at different airspeeds, increases airflow through the core during ground and climb conditions where mass flow is low and a large reduction in drag in cruise flight where mass flow is high.

On an RV, extensive cowling mods will be required to fit something like what is described above, ahead of the firewall. Other installations have fitted massive rads a few inches from the firewall and relied again on sheer size to get proper cooling. Very few recent installations have employed the lessons learned in WWII. I can think of Reg Clarke's Sube Dragonfly which eventually ended up with a really small belly scoop and excellent cooling and one Ford V6 powered Velocity with a P51 style belly scoop with an inlet area of only 22 square inches which also cooled very well.

A belly scoop is possible on the RV10 due to the central tunnel for internal routing of coolant lines. This allows a proper duct length and exit door configuration. It also allows cowling space for intercoolers. A word of note on intercoolers: these require 50-75% of the inlet area of the main cooling system to be 65-85% effective at high altitudes and are especially challenging in climb at high density altitudes.
 
Count me in on a rotary too! I'm planning a 13B or Renesis, fixed pitch prop, using Tracy Crooks PSRU, EC2, and EM2 at this time. I'm really hoping to see a continuous discussion here. I agree with cjenson that things will only get better within the next few years as more information and products are made available. I'm just building the wings myself so I'm a couple of years away from needing an engine for my RV-8. Which brings me to my favorite dilemma. You try to plan ahead but you know new products, ideas, or techniques will surface and some or all of your plans fly out the hangar door! Obviously the intake, cooling, and exhaust are the primary problems to over come. Those of you allready discussing the cooling and ductwork have an avid fan here! I'll be watching very closely to see how others set up their aircraft. Personally I like the KISS approach as much as possible. Massive redesigns with coolant hoses running long distances through the fuselage to a belly mounted radiator creates failure points and maint. issues that I'm not ready to accept at this time. But I'm keeping an open mind and the mental pic. of an RV-8 with a P-51 belly scoop incites the RV grin!:D Who is working on the aluminum end housings? This is the first mention I've heard of them but a 27 lbs savings would be substantial!
 
Hey Bill, what stage are you at on your RV10? I've got my tail surfaces done and am working on the rear fuselage now. I've got a QB so it's coming together quickly.
 
rv6ejguy said:
Hey Bill, what stage are you at on your RV10? I've got my tail surfaces done and am working on the rear fuselage now. I've got a QB so it's coming together quickly.
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I'm just finishing up the tail feathers. I have a slow build kit. I have the wings (still in the box) No fuse parts yet. I'm a "low buck operation".
Bill
 
rv6ejguy said:
Divergent ducting with a smooth transition not exceeding 6 degrees has shown to be the best. Converging the flow after the rad may help to recover the velocity before dumping it back out into the freestream. The front mounted rads used by Tracy Crook and Eggenfellner are there for packaging and ease of installation, not efficiency. The short duct length MUST cause poor pressure recovery and dumping the exit flow into the turbulent cowling flow causes higher drag. These installations cool because of high rad surface area and volume, not because they are great designs. The tight fin and tube spacing of GM evaporator cores has shown to offer high drag per unit volume and poor heat rejection at typical RV climb speeds. They work ok at higher speeds as far as heat rejection goes.

They do work and the front mounted rads keep plumbing short and solve many packaging problems on the RVs with deep spars. The cowlings can be kept near stock also. These are real considerations as well for any installation.

I'll add additional comments on Tracy and Eggenfellner set-ups. Tracy gets just adaquate cooling with his evap cores. He has the open area to allow the exit area needed.(at least better than the Subaru) I have seen the H6 Eggenfellner conversion and the right side radiator is almost touching the front of the right bank of cylinders. Not good. The exit area can be as important as inlet on a good cooling system. Tracy is limited by the small in-cowl space allowed by the RV-4. Plan for plenty of exit space for the post-radiator airstream!

Bill Jepson
Rotary10-RV
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The cooling issue Im curious about concerns the density of the radiator fins used. TCrook uses a high fin count core that blocks airflow- suggests a pretty high aerodynamic drag penalty. The use of regualar aluminum auto radiator design, with a less dense core, combined with higher speed airflow, makes more sense to me, particularly if exhaust air ducting allows low-restriction flow to the exit port(s). I have no idea if/ how much drag is reduced or how much the heat rejection rate differs.

Tracy reports problems with taxi-speed overheating, less so with high speed operation. Im a little surprised at that comment given the size/effectiveness of the "fan" up front. Might the high-density fin count in the A/C cores block airflow at both speeds to some extent, overcome by the ram-air effect of 100mph speeds?

I really like the idea he tried concerning routing a water cooling line thru the oil pan to assist the oil cooler, but I wonder if an outside-the-oilpan cooling line might be significantly safer (no chance for leaking water contaminating the lubricating oil) and almost as effective.

The other issue that really concerns me is the apex seal oilers that supply engine oil (the additives burn dirty, reduce engine life). Tracy suggests mixing 2-cycle oil with the fuel. I dont like that suggestion because a little oil in the fuel greatly increases the detonation, possibly a problem with high compression or turbocharged motors. Has anyone figured out a way to use the stock oil system for lubrication the apex seals, but supply them with clean-burning 2-cycle oil, not engine oil (Id prefer to use a good synthetic, like Mobil One in the engine/redrive).
 
Few people have addressed the liquid cooling drag issues. They simply put something on to keep the temps in check and fly it. I have flow benched various rad cores to see what matrix drag is like. The GM evaporator core has high drag but is quite efficient at heat rejection. The oval shaped tubes on some aircraft oil coolers compared to the concave GM tubes, , combined with less dense tube spacing and more open fin spacing offers far less drag. This is the route that Eggenfellner has gone with his latest cores as suggested by Bill Kay.

Certainly on the ground, the GM evap cores are essentially useless with no airflow penetrating the core from the propwash. We typically see less than .25 inches of water pressure at the face at idle. These cores were designed for centrifugal type fans to force air through them with 2-4 inches of water.

In cruise, we see 4-8 inches depending on speed and altitude and the cores function fine here. Drag is likely considerable. Our experiments have indicated that an open, relatively deep core is best suited for aircraft. An efficient duct located in the outer half of the prop arc may be able to reduce core area and volume by 50% over cheek mounted rads. Ground cooling is likely to be far superior as well. The air near the prop root is pretty dead and turbulent.

Running water through the oil works but a just adds more heat to be rejected out the rads. A proper air to oil cooler would do the same job. Typically Wankel and turbo engines need a substantial oil cooler. Again, it's hard to beat the true aircraft ones here.

Few people seem impressed with Mazdas original oil metering design and most racers remove it and simply add a very small amount of synthetic 2 stroke oil to the fuel. There does not appear to be any serious effects on octane rating. John Slade has run up to 46 inches I think on 87 octane with high compression rotors!
 
Cobra,

Regarding the stock oil injection system. Tracy sells a pump from PCV Technologies that replaces the stock oil injectors. It draws oil from a separate oil supply. There are two versions, a mechanical pump that is driven by the stock oil pump interface, and an electrical version. This solves the problem of using engine oil for apex seal lubrication, and the alleged "deposits" problem.

Some guys claim to be running the stock lubrication system without any problems, but most guys simply remove the whole oil injection system for simplicity and weight (it's not that heavy).

Tracy.
 
thallock said:
Cobra,

Regarding the stock oil injection system. Tracy sells a pump from PCV Technologies that replaces the stock oil injectors. It draws oil from a separate oil supply. There are two versions, a mechanical pump that is driven by the stock oil pump interface, and an electrical version. This solves the problem of using engine oil for apex seal lubrication, and the alleged "deposits" problem.

Some guys claim to be running the stock lubrication system without any problems, but most guys simply remove the whole oil injection system for simplicity and weight (it's not that heavy).

Tracy.
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Cobra, Tracy's info is correct, additionally 2 stroke oil has a minimal effect on octane AT NORMAL PROPER MIX LEVELS. The rotary needs even less oil for the apex seals than a 2 cycle. Guys that normally mix 2 cycle in the fuel have forgotten and flown 100's of miles with nil ill effect. Mistral who are certifing a rotary are using the stock system burning sump oil. The RX-8 passes all modern smog laws while burning sump oil.(They use a electrically controlled pump with 2 inlets per rotor.) This is really not a worry (or a big worry anyway) that should cause anyone trouble. If you want the least concern or hassle run the stock system. You can get MINIMAL improvements in performance using a very lean mixture of 2 stroke oil in the fuel. (> 100:1) All the racers use pre mix because fewer parts can break. Not a weight issue the pump couldn't weigh more than a few ounces total!
Bill Jepson
Rotary10-RV
 
I just finished reading (for the first of what may be MANY times) Paul Lamars' article on engine cooling with respect to the needs of the rotary engine. If you haven't read it I've attached the link. Interesting information on duct shapes and heat exchangers. Lots of info on the site. http://www.rotaryeng.net/cooling.html
 
copterdoc said:
I just finished reading (for the first of what may be MANY times) Paul Lamars' article on engine cooling with respect to the needs of the rotary engine. If you haven't read it I've attached the link. Interesting information on duct shapes and heat exchangers. Lots of info on the site. http://www.rotaryeng.net/cooling.html
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This was extremely interesting, in fact the entire thread is! I'm not considering a Wankel but a Deltahawk and will obviously run into the same issues.

This:



looked like a very nice solution. At first I thought it looked strange because the airflow would have to change direction 90 degrees twice, but when you think about it it's just a slight s-curve. The testing setup on the truck with pitots was also very impressive, looks cheap and simple yet provides valuable data.

Is the 2-3 cu.in. rad pr HP a good universal rule of thumb? (i.e. will it apply well to a DH installation still in the pen&napkin phase?)
 
Thanks for the excellent cooling article link and info about the oil pump- I hadn't seen it on Crook's site before. Ive thought about a wedge diffuser and side mount radiator, but I like the bottom mount idea even better. Im not too wild about the bottom exhaust-shutter design; a rear exhaust duct might look and perform better. Does anyone know what radiator was used?

Im still undecided on kit and engine; right now, because of higher fuel prices in the future, I'm leaning towards the 9A over 7A, and considering either Renesis or a single turbocharged version for both. FWIW, I'm thinking a cockpit adjustable-boost turbocharged 13B is probably a better choice for the 9A (lower HP requirement, extra power-on-demand for short field takeoff), the more powerful Renesis probably better in the 7A and 10. I have not seen a source or price listing yet for the Renesis yet but imagine it should be more common in a year or two. I'd really like to see a fuel use comparison between the two motors before the final choice is made.

My experience with automotive turbocharged engines has shown that oil contmination in fuel causes a real detonation problem, at least with higher boost levels (>10psi) where tuning is near the edge. The low oil:fuel concentration with the rotary is probably insignificant, but worth keeping in mind if we go with a turbocharger.
 
While some of these horizontal rad configurations are flying and cooling fine on some Ford V6s, turning air 180 degrees always involves losses and losses equals drag. Louvers also are draggy devices. Lamar has lots of great theories but little or no practical experience flying anything with a rotary in it. Food for thought though.

John Slade runs a large NACA duct on his turbo 13B cozy for the rad and intercooler air and this is working well in Florida. Not too practical on an RV probably but I have an auxiliary rad behind my baggage bay fed by a belly mounted NACA duct. This shows about 90% pressure recovery compared to a ram duct which is remarkably good. The hard part on an RV is finding a good place to exhaust that air.
 
John Slade runs a large NACA duct on his turbo 13B cozy for the rad and intercooler air and this is working well in Florida. Not too practical on an RV probably but I have an auxiliary rad behind my baggage bay fed by a belly mounted NACA duct. This shows about 90% pressure recovery compared to a ram duct which is remarkably good. The hard part on an RV is finding a good place to exhaust that air.Today 11:20 AM
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I find it interesting that the NACA ducts will work satisfactory in this application. It seems that NACA didn't think they were exceptable because small pressure increases in the scoop would trip the air to bypass the opening. But if the heat exchanger has high porosity(low air flow restriction) a NACA duct would work ok. So my question to rv6ejguy is what kind of heat exchanger and ducting did you use to obtain the 90% pressure recovery? Also you said that this was an aux. radiator. Could you describe your eng. installation for the rest of us?

I have to agree with Ola that the heat exchanger and wedge shaped diffuser mounted under the engine is an attractive arrangment. A propery designed intake that recieved some of the prop blast while taxiing couldn't hurt. I do agree that cowl flaps are draggy but if they are only used durring taxi and climb and closed durring cruise I would personally find this acceptable. Paul Lamar does have a very good piece of advice in that article and that is to find someone with a successfull installation and copy them. Then work to improve it. By the time it's my turn to fly you guys will have a good system all figured out!:D Right?
 
copterdoc said:
By the time it's my turn to fly you guys will have a good system all figured out!:D Right?
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My plan exactly! :D

The drag of the open louvers should be a minor compromise as they'd be opened fully for, as you say, taxi and climb.

I wonder if a slot like this:



could provide enough exit area while the louvers are fully closed during cruise.

I still have some difficulty imagining the air molecules dancing happily through two 90 degree bends, but it does allow for a fairly large rad face with little depth.
 
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It looks to me that Lamar's setup uses fixed louvers, making them moveable would help reduce drag in cruise but be a bit complicated. Conventional cowl flaps when closed don't really produce any drag. Louvers have pretty high plume drag. From years of flow bench studies, turning air this much involves high losses. The advantage of a horizontal rad is a gain in area and volume and space packaging. The disadvantage is drag and cowling revisions.

We use an Aero Classic oil cooler, rear mounted for the auxiliary rad. This is fed by a 3 inch NACA duct. For the complete story:

http://www.sdsefi.com/air41.htm
 
rv6ejguy said:
It looks to me that Lamar's setup uses fixed louvers, making them moveable would help reduce drag in cruise but be a bit complicated. Conventional cowl flaps when closed don't really produce any drag. Louvers have pretty high plume drag. From years of flow bench studies, turning air this much involves high losses. The advantage of a horizontal rad is a gain in area and volume and space packaging. The disadvantage is drag and cowling revisions.

We use an Aero Classic oil cooler, rear mounted for the auxiliary rad. This is fed by a 3 inch NACA duct. For the complete story:

http://www.sdsefi.com/air41.htm
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The louvers Lamar suggests are supposed to be closeable. small exit slits were to remain in the closed position. I agree that this would still have a high plume drag, but is simpler than many other setups. A typical bottom exit would be less draggy. I also did a design venting the radiators in a side slot like the Thorpe. Peter Garrison's original Melmoth design used this system to excellent effect.
Bill Jepson
 
Just an idea to throw out for comment: how about an adjustable under the propeller scoop feeding, to an angled duct to a wedge feeding an angled, mostly-horizontal, radiator, exiting to a wedge shaped collecter, feeding an underslung exit duct behind/around the front wheel.

The adjustable scoop could be opened (down) to catch prop blast at idle and taxiing, closed 1/2 for low-speed climb, and closed to the smaller cruise position for lower drag at higher speeds. In the 9A, the big/open scoop might even help to work as a speed brake to some extent for landing with a fixed prop setup.
 
cobra Just an idea to throw out for comment: how about an adjustable under the propeller scoop feeding, to an angled duct to a wedge feeding an angled, mostly-horizontal, radiator, exiting to a wedge shaped collecter, feeding an underslung exit duct behind/around the front wheel.
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Cobra you said a mouthfull! I'm no expert but I think the scoop has to be properly proportioned for the diffuser duct to work. That setup brings to mind variable geometry intakes on fighter jets and gets complicated fast! Getting more air flow through the radiators at low speeds is the key. I've read where some of the pusher installations have used fans to pull air through but shouldn't be needed on a RV. I work with turbines and dearly wish for some bleed air on my RV. I used to build crop dusters and they used bleed air to augment the oil cooler while sitting on the ground being reloaded. That PT6 could sit there all day in feather and run just fine. But when they tried going without the augmentation temps went sky high. I don't know about a variable intake but what about an aux air scoop that would feed into the existing duct durring taxi or climb and retract shut durring cruise? I'd really like to keep this simple and the less cockpit controlls and holes in the firewall the better. I'll bet that someone has allready tried some of these things and will hopefully share their results with us. It's easy to say this or that won't work untill somebody tries it. I haven't seen anything new on Tracy Crooks' site about the 20B powered RV-8. Anyone know how he is planning on cooling it?
 
cobra said:
Just an idea to throw out for comment: how about an adjustable under the propeller scoop feeding, to an angled duct to a wedge feeding an angled, mostly-horizontal, radiator, exiting to a wedge shaped collecter, feeding an underslung exit duct behind/around the front wheel.

The adjustable scoop could be opened (down) to catch prop blast at idle and taxiing, closed 1/2 for low-speed climb, and closed to the smaller cruise position for lower drag at higher speeds. In the 9A, the big/open scoop might even help to work as a speed brake to some extent for landing with a fixed prop setup.
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Cobra,
There are several designs for wedge shaped inlets, for the EXIT to be truly effective you need space for the air passing through the radiator to start flowing again usually 2-4 times the radiator thickness. So for a 2inch thick radiator you should have at least 4-8 inches of clear box before trying to do anything with the air (LIKE TURNING IT) to get best effectiveness. The wedge shape exit would make 1/2 your radiator inneffective.
Rotary10-RV
 
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This thread has really helped to spawn new ideas. I don't know how well the geometry inside the cowling would work out, but angling a radiator inside the duct should allow a mostly-straight path from front scoop to cowl exhaust- the "wedge" would not really require the air to make 2- 90 degree turns :confused:

Im thinking of a cooling system sort of shaped shaped like a snake that swallowed a rabbit here...with the radiator buldge more wide than tall.

Another idea: why not attach small-diameter fan blades behind the propeller, possibly as part of the spinner, to feed air to the radiator ducts at low speeds- possibly a ducted fan that would look i bit like the old radial engine cowls?
 
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You can turn air pretty efficiently 90 dergrees or even more if it is done with long radaii and or large cross sectional areas. Unfortunately under an aircraft cowling, you usually have neither considering the flow rates involved- in the ten's of thousands of CFM. Some aircraft have this done right. I was looking at a turbone Lancair IV yesterday. Engine compressor is fed by twin large NACA duscts on either side of cowling. Cross sectional area of cowling smoothly increases for almost 2 feet and makes a gentle 90 degree turn to the rear mounted compressor. Beautiful and very efficient I would think based on my 20 years of running a flow bench.

NSI does something similar for RVs using the stock inlets and glassing a duct inside the cowling turning the air 90 degrees to a central mounted rad and exits the air out the stock exit duct. I have heard some reports obout marginal performance however and there is a LOT of ductwork here. Elegant but clunky and complicated at the same time.

Bottom line is that it's hard to fit a good, LOW DRAG rad design under the stock RV cowling using factory inlets and exits.

The fan idea is a bust because they simply block flow at flight speeds. Removed quickly from the FW 190 for instance. Even electric fan block flow in flight so much thought has to be given here for ground cooling solutions and rad area vs. volume.
 
rv6ejguy, I read your website until the eye was large and dry last night. First let me commend you on your perseverance!

Then I'd like your (any others') input on this crude concept. I've used the Deltahawk since that's my first choice but it would apply to any installation I guess.

A little disclaimer. Scales, shapes, positions and angles are all subject to freehand error and a growing frustration with the open source image editor, Gimp. :D



Rad in yellow, ducting in brown with an adjustable cowl flap sticking out below.

Loosely based on this: http://www.rotaryeng.net/Shark-mouth-SV.jpg

The engine is 23" wide, so I figure the rad would be about 22" wide, 2" deep and 12" long. This gives 528 cubic inches of volume, just over 2.9 cubic inches per HP for a 180 HP engine. In their Q&A, Deltahawk says required heat rejection is about 110K Btu/hr/100 HP, do you think my suggested rad would be enough?

A 230 cubic inch oil cooler would go in the rear, upper area of the cowl.

I'd need some space near the firewall for exhaust and air exit so the rad exit has to be slightly short. A (crescent? triangle?) slit in the cowl flap should perhaps provide some additional exit area in cruise.

The intake is quite narrow in my freehand drawing, but it could be pretty wide.

I'll try drawing some more accurate cowl shapes once I can use Gimp without tearing my hair out and then ponder the pain of a custom rad and custom cowl vs the ease of just ordering an O-360...

(Btw, this is only a learning exercise, I'm years away from any project)
 
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You should be ok with those rad volumes and areas if the duct works well. Might consider guide vanes to turn the air more efficiently. The duct is pretty short so the pressure recovery might not be stellar. I'm tearing my hair out over my RV10 rad setup right now plus I have intercoolers to fit as well. That Lyc is looking pretty good right now!
 
yeah, he has done quite a bit of flying, and his engine is a junkyard special. some of the links don't work on his sight, so i don't know how up to date it is.
 
crazy thought....

Before anyone t's off on me, let me provide this disclaimer 1- I don't have my instrument cert (yet), nor do I [b=B]plan[/B] to fly into icing conditions or need anti-icing. I only ask this question because I'm spending too much time thinking about the cooling system that's years away. :eek:

Has anyone considered routing some antifreeze from a liquid cooled engine through tubes of some sort in the leading edges of the wings? I wonder if it would work, and just how much cooling could be derived, and how much weight it would add.....

Ken
RV-10 rudder
 
What about a radiator that has it's fins aligned differently. Like say at 45 degrees instead of 90? Wouldn't that keep a lower frontal area and not have to bend the airflow path around as much?

airflow.jpg
 
2 RESPONSES Icing and angled fins

It hasn't proved effective to route the coolant thru the leading edges. Too hard to communicate the heat to the LE. Several attempts have been made to use the wing as a plate radiator as well. They never worked as well as a standard style heat exchanger.
With respect to the angled fins issue; NACA tested many different types of ducted radiator and found that the angle made little difference. (I know this seems counter-intuitive.) Best results were with either a wedge inlet with wide open exit, or at least 4x the radiator thickness. (which could hapen inside the cowl) Drag of a ducted radiator that REVERSED the flow direction 180? made little difference on drag provided the exit wasn't exposed to the inlet airstream.
Bill Jepson
Rotary10-RV
 
Mazda 1991 13b

Hi! I am looking at a rv4 kit that the owner has a rebuilt Mazda rotary with the gear box and engine mount. What is it worth? I would like to put a O-320 in.
Thanks
 
Kinda like saying "I'm looking at a car. What's it worth?"

Devil's in the details.

Charlie
RV-7 Renesis FWF work
 
I built a 13BT set up for my RV-8. It's got the Airworthiness Certificate, but I haven't flown it yet. Still tweeking the engine, very close.
These things are highly specialized. They reflect the imagination and skill of the builder.
Mazda rotary engines are well proven, and give good service. the devil is in the ancilliary equipment that supports them.
You may have a well engineered and skillfully crafted unit, but how can anyone know until it actually runs?
Is this an unfinished kit RV-4 with a pile of Mazda parts, or has it been assembled and flown? Or somewhere in between? The reduction gear, fuel and ignition controllers, engine mount, intake and exhaust manifolds are major factors in determining value.
Pictures would be good too. I'm always interested in other rotary powered aircraft.
 
Mazda Rotarys

As they've mentioned, the "Devil's in the Details". There are folks out there who would snap up a well built 13B as a FWD installation. Much will depend on how well the intake, exhaust, radiators, etc. were fashioned as well what type of prop speed reduction gear it has, as well as computer and coils. The engine mount is another area that could add or subtract from the value of the a/c. I paid $5500 for my Rotary engine in 2006 that had been flying on a Glastar and I hoped most of it would work on my RV-9A project. That was ultimately a mistake since the prop, radiators, intake and exhaust manifolds were all not usable on my fuselage. I knew the engine mount would not work before hand and still have that if anyone knows someone with a Glastar who wants to install a 13B in it! :)

Doug Lomheim
Finishing an RV-3 restoration
Returning to the 9A w/13B FWF stuff this winter!
 
Ask Dave

In one of the news stories covering the BCA flyover in Kansas City a few weeks ago I saw a Navy Blue RV-6 vertical stab with N4VY stenciled on it. This is Dave Leonard's (goes by Rodoc here) 13B turbo. He would probably be a good source of info.

Tom
 
Hi Jon!
Yep, that's us.
Hope all is well with you. We sure like N725RV. Maybe you will find and finish a part built RV-4. It's a good way to get back in.
Scott & Marilyn
 
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