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Saunders JetHawk...Any builders?

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shadow

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Sep 23, 2008
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Matt,

Thank you very much for running the numbers, I greatly appreciate it!

I mistakenly wrote mixed-mode fans, when what I mean was mixed-flow fans. They're centrifugal/axial hybrid fans that have characteristics of both. Earlier in this thread you mentioned that it might be best for amateurs to look into centrifugal fans over axial fans. The mixed-flow seems like an interesting compromise and I wanted your take on them.

I've actually been researching HVAC fans looking to see if I can simply poach one of their fans for aviation use. However when I look at them they just don't seem the part - like they're too flimsy. I think the design of HVAC ducted fans seem to imply much lower rpm operation due to noise constraints.

I'm very interested in this subject and am eager to learn more.

Another type of fan, a squirrel cage fan, has always intrigued me. I own one and a number of regular house fans and I'm always impressed at how much flow I get out of the squirrel cage fan per amount of noise compared to the regular house fans. I've often wondered if there could be something there.

Cheers,
Serge.
 

rocketboy105

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I've actually been looking for a good squirel cage fan :) I'm doing all kinds of energy saving/ producing things to my girl friends house. One idea I've already validated,...putting a fan in the attic during the winter,...and blowing the warm solar heated air into the house. Free,..almost heat. ONly certain days does it work,...but if (like us) you don't mind wearing a sweat shirt part of the time,...and (you adjusting to the temp) a bit,...instead of trying to force the whole environment of obey a thermostat,...you save some serious energy that way. I'm also working on a "recouperator" a device that "pre-heats" the incoming cold water with the warm drain water from the shower so you use less "hot" to start with. I'm building the fiberglass tool as we write.

ANyway,...any HVAC fans would be horrbile for aircraft propuslion;

1) Quasi-zero pressure ratio
2) Inefficient
3) Flimsey

When I said "ametuers" and centrifugal fans,...I meant that with a good manufacturing skill set,..and sme analytical capability,...the ability to reverse engineer, copy, scale up the aero,...all that would get you away from spending the endless hours I have learning compressor aero,...and get you to a rugged,...workable, funtioning unit in the least amount of time that had adequate pressure ratio to have worth while performance.

Matt
 

avtech

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Re: Saunders JetHawk...Any builders? avtech

Anybody can take an expensive aircraft engine and put it in a small airframe and have it fly well however the expense of it all leaves it out of the reach of the common man. The ideal for the Jet Hawk was to have a jet type sport plane that the average guy could afford to build and fly. It was never intended to be a cloud burner or a cross country airplane as stated in Saunders's articles. It was for casual flying. Take off, retract the landing gear, fly around and enjoy, come back and land. I was lucky enough to be allowed to fly the prototype Jet Hawk. The prototype was a much larger two place aircraft that grossed out at almost 2000 lbs. The engine was from an old RX-3 auto. It was much more complicated then the Jet Hawk 11. It had four fuel tanks, two in the wings and two tanks on each side of the passenger seat. The landing gear was retracted by a crank located on the right side of the cockpit and would raise both main gear and nose gear at the same time. It had duel controls for pilot and passenger. It also had flaprons that were used for landing and take offs. Unlike a propeller plane that vibrates and blows air over the fuselage, tail and control surfaces which make it feel alive and dynamic, the prototype Jet Hawk felt wimpy because it was smooth and vibration free. Because or this I was afraid to climb out at more then a shallow angle. I wanted it to build some air speed. When I had gained sufficient altitude I pulled the stick back to 70 mph and was surprised to find that it would climb at over 700 feet per minute at a very steep angle. The handling was smooth and gentle with no p-effect. It was very much like the early jets and once I figured out that I wasn't going to fall out of the sky, I started to in joy the ride. The landing was smooth and uneventful. I woulld characterize the performance as being close to that of a cessna 172. The design of the Jet Hawk 11 was based on the prototype. Since I'm a plans owner and a engineer that has specialized in fluid dynamics, I would like to give you my opinion of the Jet Hawk 11 design and address some of the concerns expressed in this forum. First of all the 4130 tube frame is not heavy. Steel tube frames are used where light weight and high strength are desired such as in bush planes. (Piper super cub etc.) A lot of the early WW11 Fighter had steel tube sub frames with aluminum skins. The tail of the Jet Hawk will not fall off or flutter as alleged earlier in this thread. The combination of the steel tube frame, ridge foam and fiberglass and tail pipe make for a very strong and light tail appendage. The Mazda rotary engine is not the power house that everyone thinks it is. The 12A engine as used in the RX-3 RX-4 and RX-7 cars has only 1146cc's of displacement. It is a 7000 rpm engine. At 6000 rpm as installed in an automobile it only produces 100 hp. The 13B engine is not much better. In the Jet Hawk, because of the low pressure plenum that the engine sets in, it only produces about 90 hp at 6000 rpm. The plans call for a cross over tube from the tailpipe to the carburetor intake to try to normalize the pressure, however the whole system is working at a lower then atmospheric pressure which drops the engine power to about 90 hp. I know that some of you think that you have a 130 or 160 hp engine as mentioned earlier in this thread but the truth is that if its naturally aspirated is is only producing 90 hp in the Jet Hawk. Some of the horse power is recovered at speed due to the increased intake pressure. The fix for this problem is to run a carburetor intake tube up threw a hole cut in the engine hatch to a model 97 type carb scoop. You can make your own if desired. Use a screen instead of air filter. A air filter was needed inside the plenum because of debris drawn in by the fan. This fix should net you about 10 hp. The static thrust with the naturally aspirated 12A engine is 190 to 200 lbs. The thrust per horse power at 190 lbs of thrust is 2.1 lbs. Thats a solid 2 lbs per horse power. Two lbs per horse power is in the efficiency range of a highly loaded fan disk of the diameter used in the Jet Hawk. It doesn't matter how much you carburet or fuel inject this engine if it is naturally aspirated it will only produce 90 hp at 6000 rpm. 6000 rpm is the best speed to run the engine because of the low 4000 rpm torgue peak. The only way to increase the horse power is to increase the combustion chamber pressure. C.c.p can only be increased by NOS, supercharging or turbo charging. Various Mazda models came with turbo rotary engines ranging from 165 hp to 280 hp. 2.1 lbs per horse power at 165 hp is 346.5 lbs of thrust and 280 hp would be 588 lbs of thrust. At a 1200 lbs gross weight it would be almost a 1 to 2 thrust to weight ratio. A 1 to 2 thrust ratio is very very good. Paxton and M.P.I. make belt driven superchargers that are a good alternative to turbos. They are simple to set up and are reliable. The Jet Hawk fan uses thin wide blades made of aircraft aluminum plate. They are very strong, light and efficient and are a excellent choice for the turbulent plenum that they draw air from. Thin airfoils are used for high speed fans and wings of supersonic fighter aircraft because they are stable and are immune to airfoil compression. Airfoil compression is something that happens to thick cambered or curved airfoils at high speed. It was a problem for WW11 fighter planes causing many crashes. Cambered airfoils are low speed devices and should not be used in a high speed fan application such as the Jet Hawk. If you are going to run a turbocharged high horse power engine as mentioned earlier I would recommend using seven blades instead of the five that the plans call for. It's just as easy to cut seven blade slots in the fan hub as it is to cut five. It should be mentioned here that the hub and blades are light and contribute less gyroscopic loads on the engine then the original flywheel, clutch and pressure plate used in the automobile. High speed fans don't impart a lot of twist to the air like low speed ones do. It was found that flow fences ( see plans ) worked just as well as a stator to straiten the air flow. The tapered tail pipe speeds up the airflow and changes the ducted fan from a slow speed device to a high speed device. It also allows for sustainable thrust. What is sustainable thrust? Unlike a fixed pitch propeller airplane which screws its way threw the air and starts losing thrust as soon as it begins to move, a tapered tailpipe jet configured aircraft can actually increase its thrust as it builds speed. The Jet Hawk starts out with less static thrust then say a 172 but will maintain its thrust higher into the speed range. This usually occurs at one half of the tail pipe velocity. In other words if your jet has a tailpipe velocity of say 200 mph it will maintain its thrust to 100 mph before it starts to diminish. The Jet Hawk 11 has three air intakes, two above the wings and one large one on the bottom of the fuselage in front of the fan. The air intakes above the wings have two blow-in doors each. (auxiliary air intake doors) Blow-in doors are used to help normalize the air pressure in the plenum at low speeds. Blow-in doors have been used in all kinds of fighter jets, from early P80s, F9Fs to modern Harrier jets. Even supersonic fighters like the F5 have them. The trick with air intakes is to have just enough intake area at speed. Too much area and they will start to spill air and create drag. The designer of the Jet Hawk intended for the builder to modify the area of the bottom intake to fit the power needs of his particular aircraft. Big intake=shorter take off. Smaller intake =faster top speed. If you want speed you must modify the area of the bottom intake. The Jet Hawk 11 is a beautiful well thought out aircraft and the plans are of excellent quality. It will fly on only 90 hp and turbo charging or supercharging will increase the performance drastically. Supercharging and turbo charging are not that expensive compared to an aircraft engine. The designer recommended power augmentation (plans and information pack) because he knew that the engine alone was only part of the power potential. I've searched to find the best possible replacement engine for the Mazda rotary. At first snowmobile engines looked promising but they all require a very large expansion chamber that would take up too much room in the plenum. The Mazda 12A, 13B and RX-8 engines are in my opinion still the best engines for the job. They are heavy but are compact and allow air to flow around them easily and as mentioned above they have a lot of power potential. Another thing, don't even think about comparing a R.C. ducted fan to a full size aircraft. They have absurd power to weight ratios and carry no pay load. After visiting one of the first builders, Saunders wasn't happy with what he saw. He realized that to continue to promote the Jet Hawk he would have to give classes and seminars to educate potential builders. Having limited resources and not being much of a people person, Saunders decided to quit the plans business and pursue other interests. Saunders went on to become a award winning designer in other areas of motorsports. If you own a set of Jet Hawk plans consider them a treasure because many people have tried to design a man carrying ducted fan jet aircraft and have failed. If you want to build your own design, perhaps an all aluminum aircraft, use the Jet Hawk Plans as a Guide. Saunders set out to design a low cost, simple jet configured airplane for the average man, and in my opinion he succeeded beyond all expectations. Want to know more and see pictures? Read the last article Saunders wrote on this subject. (The March 1991 issue of Sport Pilot, Hot Kits & Homebuilts) END PART ONE.
 
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vhhjr

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Excellent summary of the Jet Hawk. Any suggestions as to how or where one could get a set of plans?

Vince Homer
 

vhhjr

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It doesn't look like the ME-162 Jethawk ever got past the model stage. I have a set of RC plans for a 162 that I reworked a bit to make a homebuilt out it it. That project never went anywhere either.

Does anyone know how many sets of Jethawk II plans were sold? I have read posts saying that sets have appeared on Ebay in the past.

Vince Homer
 

garnaut

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I'm a little late getting to this discussion and I hope avtech is still here...

I have a copy of the Jethawk plans and have studied them carefully...there are some good ideas there but the fan and duct design is very rough...

I say that as an aero engineer with considerable experience in both propulsion and airframes...Getting 2 lb of thrust per hp is not very good at all...this is a very lightly loaded fan of about 25 or 26 inch diameter with only about 100 hp going into it from that small rotary...

I have written a thrust calculator program based on momentum theory that is quite accurate...200 lb of thrust from 100 hp on a 25 inch fan equals mechanical fan efficiency of only 40 percent...that is not good at all...

A decent fan and duct should get 75 percent efficiency without much trouble at all...that would be about 300 lb of thrust from 100 hp with a 25 inch fan...

A highly loaded low bypass turbofan is another matter...here 2 lb thrust per hp is not bad...a straight jet will equate to about 1 lb per hp...

I moderate a yahoo group on ducted fan aircraft and I invite anyone interested to come and check it out and join up...ductedfanaircraft : Ducted Fan Aircraft
We have discussed the Jet Hawk quite a bit in the past and would welcome avtech's first hand flight reports in the type...

The biggest problem with the Jet Hawk is the very unrefined intake duct...really it is not even a duct as simply three opening for the air to rush in...also the intake area is not adequate by a fair margin...the result is the fan does not get enough air flow...

The space frame structure, especially the wings, is very innovative...and I think the overall airframe design is adequate...All that the airplane really needs is a well designed inlet duct...the exit nozzle does not look bad off hand but you would need to size it properly...

The fan itself can also be improved as the blades appear to be mostly flat with little or no camber...this is easy to build but it is a compromise...I agree that the thin blade sections are a good idea here due to the high subsonic mach number at the tip...

but you would want to curve the blades properly so that you get the desired pressure distribution over the convex surface especially...this is important for making lift and therefore thrust...this could be accomplished starting with flat pieces of thin plate...

The curvature of the blades and the angle at which they are arranged (stagger angle) determines the flow passage between blades which should be of a diverging section area...like a diffuser...this is what imparts the pressure rise that we need in order to make thrust...

the stator is likewise a diffusing passage and serves to straighten the flow and further increase static pressure...so it is unwise to leave out the stator...

the inlet duct is probably the most challenging aspect of a ducted fan design...At speeds up to about 200 mph you want a converging duct that will accelerate the flow and will increase mass flow also...this is opposite to a turbofan duct which is a diffusing duct that decelerates the flow...this is because turbofans normally fly at about M 0.8 and the flow at the fan face needs to slow down to about M 0.5...

With a slow flying aircraft we have the opposite situation...

The rotary engine is a good choice...and you can get a lot of power from a naturally aspirated rotary engine...the stock RX8 2 rotor engine makes close to 250 hp but at a high rpm of about 8500...

The best way to boost power is to install peripheral intake ports...Paul Lamar has a website and discussion group that is in the forefront of rotary engines for aero use...he has dyno tested a stock RX8 engine with P-ports that makes over 260 hp at just 7200 rpm...the video is on youtube...

Turbocharging and supercharging are good but I would first start with a p-port engine...you will have 250 hp engine any way you slice it...the RX8 being a bit better than the 13B...both being the same 1300 cc displacement...

A 250 hp p-port engine and a properly designed fan of 25 inches will give 600 lb of thrust provided the duct is working well also...that is enough thrust for a 1 to 3 ratio on a 1800 lb airplane...you don't want the ratio to be less than about 1 to 3 if you want good takeoff and climb performance...

Bottom line is that the Saunders Jet Hawk looks like a well designed airframe that should fly well and avtech's pirep bears that out...but the airplane desperately needs a properly designed fan and especially inlet duct...that would make this airplane truly live up to its potential...

Regards,

Gordon Arnaut...
 

Skygeezer

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Re: Saunders JetHawk...Any builders? avtech

Fascinating. The little I know about the Jethawk comes from ducted fan design groups. In those forums the Jethawk is considered a very poor design. The thin airfoils and accelerating duct are the opposite of what is wanted in most aircraft applications. I have the plans, and can't say that I am impressed by the overall building techniques. Blow in doors and cheater holes are the absolute last thing you want according to the design engineers I have talked with on the forums. One of the reasons for the failure of most ducted aircraft designs is the assumption that because such an aircraft looks jet-like, it should perform like a jet. That isn't the case. Attempts at high speed high pressure fans and ducts don't work well. What moves a ducted fan design is mass flow, with the design of the intake lip being critical to performance. I am certainly not an engineer and only know what I read from those who are. Amazing divergence of opinion from Avtechs post.
 

avtech

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Re: Saunders JetHawk...Any builders? avtech

There are fifteen types of engineers. Out of those fifteen types of engineers there is only one type that has the education and qualifications to judge the Jet Hawk. That type of engineer is an aerospace engineer. All the aerospace engineers I know are very impressed with the Jet Hawk. Discussion Groups Are fine and computer programs are great but nobody seems to get anything done in a practical since and theres a lot of negativity out there and I think that is because Saunders left the Jet Hawk design unsupported. I'm a fan of the design and I knew Saunders and I know why things were designed the way they were.
First of all the JetHawk was designed over 35 years ago in the mid 1970s. Saunders goal was to design a simple to build jet style aircraft that the average guy could build and fly. A lot of the negativity comes from the R/C ducted fan people so I would like to start there.
Your average run of the mill R/C ducted fan aircraft has drag producing wide open intake ducts that flow air back to a powerful engine and then to a tail pipe with a opening of no less then 90% of the fan swept area. This arrangement allows for maximum static thrust and with a light wing loading these aircraft are able to fly around in circles at speeds below the stall speeds of most full size aircraft. These R/C aircraft fly on static thrust and are very limited in top speed. This is the type of R/C aircraft that the critics think that the Jet Hawk should be patterned after. The serious high speed R/C ducted fans such as Paul Ivey's modified B.V.M. Viper that set the R/C ducted fan speed record of 255 mph use small air intakes with a fan swept area of 80% and a tail pipe exit area of 70%. This 80% intake and 70% tail pipe exit formula reduces drag and increases tail pipe pressure. The result is high speed. It does however sacrifice static thrust in favor of dynamic thrust. The Jet Hawk uses this 80%-70% formula. According to Saunders, open air testing with the engine and fan would produce over 300 lbs of static thrust. He also said that in that configuration the thrust would diminish to almost nothing at 65 to 70 mph. As installed in the Jet Hawk the fan would produce only about 200 lbs static thrust but would still push hard at speeds well over 150 mph. That confirms my own experance with the Jet Hawk in which it felt a lot stronger once in the air. END PART 2
 
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avtech

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Re: Saunders JetHawk...Any builders? avtech

Why does the Jet Hawk use a plenum intake system? After the failure of the P-59 in the mid 1940s Lockheed was commissioned to build a new jet fighter for the U.S. The fighter was known as the XP-80 (F-80 Shooting Star). The turbojet engines of the time were very low powered so every effort was made to design the XP-80 as light and efficient as possible. The plane had small intakes for low drag that opened up to a very large chamber where the engine set. This chamber is called a plenum. A plenum is like a calm deep spot in an otherwise raging river. The intake air is slowed and flows very smoothly over and around obstructions on its way to the fan. The Plenum intake design became the standard for all the early jet fighters because of its simple efficient design. The plenum design insures an even distribution of pressure across the face of the fan with out using long complicated and heavy intake ducts.
Why does the Jet Hawk use thin fan blades? The fan or rotor in the Jet Hawk is built in the accepted manner (Ducted fans for light aircraft by R.W.Hovy) and the plans provide drawings for a device that puts the perfect helix in the blades. The blades are light, strong and efficient and they use the same profile as the ones used in the high by-pass turbofan engines used in passenger jets. END PART 3
 
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avtech

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Why doesn,t the Jet Hawk use a stator?
A properly built stator that actually works needs to have a blade at a minimum of every 30 degrees of fan sweep. That would be a minimum of 12 blades. The problem with stators is that they produce a lot of drag which cuts thrust. Some of the early gas and electric R/C ducted fans used stators, some with as many as 15 blades, however because of thrust losses they reverted to the familiar four streamlined engine supports that we see today. These engine supports have 90 degrees of open space between the blades and do very little to stop the swirl of the air. The good news is that this swirling air is not as important as you might think. The burner nozzles on the inside of many turbojet engines were set at an angle to provide the best push on the turbine blades. This had the side effect of causing the exhaust gasses to spin down the tail pipe. The engineers weren,t concerned about this spin. They were more concerned about having enough tail pipe pressure because tail pipe pressure is what makes a jet work. I know what you,re thinking! What about the stators in the high by-pass turbofan engines used in commercial passenger planes? Well believe it or not these stators are used for noise control. The stators focus the air strait out the back of the engine and over the hot blast of the core turbine. This slower moving ducted air prevents the noisy shearing action between the high speed turbine blast and the outside static air. Years ago engine manufactures experimented with removing the stators and even the ducts from the fans. The efficiency of the engines went up as much as 50% however the noise levels also went up to unacceptable levels. The following is a list of those engines; (GE 36 UDF) (Prate&Whitney 678-DX) (Rolls-Royce RB 3011) (Progress D27). Saunders tried all kinds of stator designs, including bifurcating the tail pipe, and found that in each case the thrust went down. What worked the best were the simple angle aluminum flow fences that are called for in the plans. END PART 4
 
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avtech

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If you are unhappy with the design of the Jet Hawk then lets take a look at all the other man carrying jet configured ducted fan aircraft. 'Oh wait a minute there aren't any!" The closest we can get is the Davis cold jet. So lets talk about that shall we. Around 1975 Gilbert Davis showed up at Oshkosh with Bob Nikkel. Davis had built a really cool miniature F-80 replica for Nikkel called the YF-80 Windstar. To power it Davis was promoting a ducted fan configuration called the D-340 cold jet. It was supposed to push the YF-80 to 300 mph. As you can imagine it stirred up quite a bit of excitement. They sold a lot of information packs and investors were lining up. It even caught the attention of some famous people like Bill Lear. The D-340 used a 350ci V8 engine connected to an up drive that turned a one foot diameter fan at 18,000 rpm. It had eighteen stainless steel fan blades that needed to be machined to a very close tolerance along with an equal number of stator blades. The whole unit along with the gear box was extremely expensive to make. Even with the turbocharged V8, the D-340 cold jet wasn't able to produce even one pound of thrust per horsepower. It was found that the cold jet wasn't able to fit inside the YF-80 so a 2/3 scale T-33 replica was started but not finished. The heavy V8 engine and the inefficient cold jet fan system spelled doom for the project. The whole project cost about $150,000.00 in 1970s money and was a total and complete failure.
Contrast that with the Jet Hawks simple and inexpensive fan system that is able to produce 2 lbs per horsepower static thrust and about 3 lbs per horsepower dynamic thrust. The prototype Jet Hawk cost only about $6,000.00 to build. In the 1980s the Jet Hawk appeared in all the aviation news publications including Jane's All the Worlds Aircraft. When the Cold Jet resurfaced it was configured like the Jet Hawk's thrust system except it used ducts instead of a plenum. It's not certain if Davis knew about the 80%-70% formula however he was definitely on the right track this time. Unfortunately he died before he could build it. Drawings can be seen on the Flying Wing web sight.
A designer has no control over the quality of workmanship of the plans builder and very few builders even attempt to follow the plans. This is evident in the following story. There was a builder in northern California who was complaining that his jet would only go 120 mph and wanted Saunders to come and look at it. The Jet Hawk cockpit is designed so that the control stick linkage runs under the frame and inside a fiberglass tunnel. This allows the pilot to set in a low reclined position as in an F-16. This position improves the general aerodynamics and looks of the aircraft. The builder had moved the linkage up inside the frame and put long supports under the seat so that he could set up high like in a truck. The canopy then had to set way up in the air to clear the pilots head. He also didn't bother to properly shape the foam for the fuselage aft of the canopy. Those modifications not only destroyed the aerodynamics but also the looks of the aircraft. On the other hand every once in a long while there will be a builder that will actually follow the plans and do good quality work. Years later I met such a person and his naturally aspirated jet would fly at close to 150 mph. 150 mph matches the specs of Saunders own Jet Hawk II.
Saunders is indeed an aviation pioneer. He was able to do what nobody else was able to do. Not Coanda, Not Caproni, and not Davis. He is considered a genius by all who know him.
If you have read my five posts, then you already know more about ducted fans then 99% of the people out there, certainly a lot more then those guys at Mass Flow.
At this point I would like to say goodbye and wish you all good luck in building and flying your own jet.
AVTECH.
 
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bmcj

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Delving way back to post #68 (https://www.homebuiltairplanes.com/forums/general-experimental-aviation-questions/1836-saunders-jethawk-any-builders-5.html#post36864) and looking at this concept...

2785d1231243935-saunders-jethawk-any-builders-piston-driven-ducted-fanwith-turbo-thrust.jpg

I see what the designer was thinking, but also understand why it would not work as envisioned. This is really nothing more than an overly complex piston engine turbo/supercharger hooked to a less efficient propeller system. This (correctly) discussed in the posts that followed.

Now onward to my question: The big, in-duct turbocharger I can understand, but what is the smaller turbine-looking device higher up in the exhaust system? Did the designer forget that he had a big unit below? Now, add a combustion chamber and secondary turbine stage in the duct and then maybe...

Just curious... "Enquiring minds want to know" :gig:

Bruce :)
 
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bikeface

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Hi to everybody, ok i did start the jet hawk back in the 90's BUT i had it redesigned(as many did). It would have been a 2 place with a Mazda rotary turbo engine and new fan system with stator made from carbon composites.
Now the bad news, i ran into the british PFA who said "no way". A new aircraft, new engine, new propultion, too dificult to licence and test, so i gave up.
Now the good news, i still have somewhere the Fan system plans, so if anyone would like them i can scan and send. Plus any pics i still have of the project.
One thing i will say is that i regret everyday that i didnt complete it.
 

bikeface

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By the way, has anybody thought about a twin fan driven off one engine( like an A10 say). not my area of expertise but im sure it can be done using lightweight motorbike shaft drives etc.
 

Vigilant1

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It looks to be a power recovery turbine geared to the crankshaft.
Agreed, that's what it looks like. Turbocompounding has great promise for Wankel engines due to the highly energetic exhaust flow (hot, and not slowed by exhaust valves). Some proponents (notably Paul Lamar) believe a turbocompound Wnakel can give BSFC numbers considerably better than piston engines, but we still await a proof-of-concept installation (as far as I know).
 

plncraze

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Bikeface, I sent you a private message about your offer of Saunders info.
 
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