Need Loads of help

[canadian]

Hey everyone

i am considering (well, if i can get a basic plan i will do) building an rc airplane.

i want to make a very simple plane that is powered by a pulse jet engine. The engine will produce approximately 5 lbs of thrust. i want to fabricate the whole thing myself. so i came here in search of help for the plane part. i know little about building planes, so could you please help me out? ok, so the things i came to ask....

im wondering if there is a simple wing design that i could build fro scratch. the materials would be (preferably) aluminum sheet that is bent and welded.

heres a thought i had. you know those big Styrofoam airplanes that you throw? well, what if i took the wings and tail fin from one of those and made a mold for it, then made a very thin fiberglass wing. would that work?

i am very open to ideas, so any input is very much appreciated.
i want the plane to look very simple (pretty much an engine with wings) i would like to use the engine as the body of the plane, and have a fuel tank underneath.

like i said, i am quite new at this, so if there are any pages with basic airplane construction advise, could you please tell me?

thank you much

Dave

[canadian]

http://www.futureflyersclub.com/ProductImages/born/stuntjetfoam.JPG

that is the type of plane i was thinking of butchering into a fiberglass one.

http://www2.gpmd.com/image/c/cmta1000.jpg

that is actually the exact plane i was thinking of. it has a 4.5ft wingspan.

[JetPlaneFlyer]

I don’t hear of many people successfully tacking a pulse jet model these days. Quite a few talk about it but not many pull it off. I once heard the pulse jet described as a ‘highly efficient fuel to noise converter’. Due to the ear splitting noise they are banned on almost all flying sites but I guess if you are in a very remote location you may get away with it. Do you have any details or photos of the motor?

I would however advise that if you have no previous flying experience with RC models then you hone your skills on a more conventional RC trainer model with I.C. or electric power. Flying RC is not as easy as it looks at the best of times but with an unproven design fitted with an untried fire breathing pulsejet and flown by a ‘pilot’ with no experience there would surely be only one outcome :( . Given your lack of experience it would be best to use a proven airframe of conventional construction, then convert it to suit pulsejet power. Most pulse jets I’ve seen photos of have the motor mounted on a pylon above the fuselage so this should be a quite easy conversion. Internal mounting of a pulse jet is all but impossible due to the enormous heat they give off.

There is a Yahoo discussion group called 'Jet-Ex-Press' that is primarily targeted at 'Jetex' type rocket power models, however there is quite a bit of expertise among the members there on pulsejets. If you are serious with this project it may be worth joining up.


Steve

[vintage1]

1/. Pulse jets are very noisy, very fast, and very inflammable.

2/. They are normally run exposed..the efflux pipe goes orange hot. It needs cooling. In practice in an enclosed situation this means airflow around it, and then a thin walled metal tube outside that, some fireproof insulation and then a skin. Ducting should be arranged to ad 'by pass' air round the exhaust to cool it.

3/. Aluminium is a terrible material for model planes..the strength to weight ratio is all wrong at models scales. Use fiberglass if you must, but ply/liteply formers skinned with balsa is more appropriate. I would not use foam in a pulse jet at all. Too inflammable and melts too easily. You might get away with it for the wings and tail tho, if skinned with balsa or glass.

4/. the chances of getting a home built first model with a pulse jet into the air and down again are nil. Unless in the middle of a large area the chances of it coming down and causing damage and injury are very high. It will need a pilot of considerable experience and very fast reflexes.

You are either on a road to nowhere, or the very start of a long road in which such a model MIGHT lie at the end..

Right now, with respect, you don't have the building skills, the flying skills or the background knowledge to attempt a project like this with ANY chance of success. Those can all be acquired, but it is a steep curve and will take a year or two.

Realistically, the best way to acquire the flying skills would be on a simulator, and a fast electric foam jet that will take the crashes. Something like a Picojet or Microjet. Maybe even a Zagi to start. Work up to insane power levels and then think about a real jet.


Building skills - well just build and repair that one, to start with.

THEN lets talk pulse jets ;) But not with me. I just know enough to know that I don't know NEARLY enough..and what little I do know suggests these are highly specialized tricky and dangerous toys to play with.

[Sparky Paul]

What Vintage says.
Pulse jets are poor power plants in any event.

[JetPlaneFlyer]

Here's a little video clip of a pulsejet in action... Check out the white hot metal and awfull noise (notice ear defenders on the guy operating it): http://www.youtube.com/watch?v=G7rZWBJ7ZLY

Pulsejets are very noisly and potentially very very dangerous in the wrong hands. They can no doubt be an interesting toy to experiment with but as noted above they are not a very practical propulsion system for a model.

Steve

[canadian]

ok, thanks for the honest replies.

i have the knowledge on the engine. i know how they work and how to build them.

i guess i didnt really tell you WHY i wanted to build this. the reason is, that i want to build something that will fly all by myself (well, build it myself). and i really like how pulsejets work. the purpose of this build it more to try and get something to fly, more than build an rc that i would use all the time. it doesnt actually have to be rc.

i know foam isnt the choice material but, like i said before, i would like to make a fiberglass wing and carve the foam out. or, if you have ideas, tell me.

or, are there any plans out there for a plane that i could use the wing design and match it up to the pulsejet?


heres a simple design i found. its kinda what i want, but would have a tail fin.

http://h1.ripway.com/webpilot/t_3548/page9/djs-wing.gif

[nmasters]

Forrest Eckstein... Now there's a name I haven't seen in a while. I'll have to keep an eye on this thread :cool:

[Sparky Paul]

The pulse jet models that used to be used in control-line speed had the motor totally outside the fuselage, for the heating problem.
Very few models had pulse jets internally.
The most successful were at least a two-man operation.. one man pumped the air thru the motor to get it ignited, while another held the plane back. As soon as the motor began running, the pump guy removed the pump connection and got out of the way, while the hold-back released the plane as soon as the pump got clear.
Getting the thing into the air as soon as possible so it could stay cool was paramount, it's no where near as leisurely an operation as a turbine is.
No taxiing! Release and immediately take off.

[JetPlaneFlyer]

It would be very difficult to attach the flying surfaces direct to the motor due to the extreme heat. Fibreglass, foam or wood would combust at the sort of temperatures involved, even aluminium would melt.
The only practical way I can figure is to have the motor mounted on a pylon to give a suitable air-gap between the motor and airframe. The pylon would need to incorporate some form of thermal barrier to prevent transmission of heat to the airframe.

I'd think very carefully before you attempted to fly a pulsejet 'free flight' (i.e. no control), It could easily prove lethal if it came to earth in the wrong place. I think they used to quite often fly these things 'Control Line' years ago... If you are determined to fly one this would appear the safest option

[JetPlaneFlyer]

It looks like there are some enthusiasts still flying these things:
http://www.airtoi.com/pulse.htm

[vintage1]

The only thing I would do with one is a very rarely exercised scale model V1 flying bomb.

Or a tethered car or something. No way would I try to put one in a scale model..of a normal jet. There are jet turbines for all that sort of thing.

I think I am correct n saying these things don't idle?..pretty much full power and thats it?

[BMatthews]

Canadian, my most heartfelt advice to you is lie down until the feeling goes away. As mentioned pulse jets are incredably dangerous to operate even when you know what you're doing and are incredably noisy. If you've never heard on you cannot begine to imagine just how noisy something can be. A track full of unmuffled stock cars at full throttle MIGHT be as noisy but I doubt it.

They are also an almost certian cause of a fire if it should crash while under power into something that is flammable. And even larger models will fly at well over 100 mph with one of these and would be out of sight in a blink.

If you're super keen then by all means build and run the engine. I think you'll agree with all the warnings after that. And it'll look good mounted on a wall somewhere.

I've seen pulse jet control line speed models fly and I have to say that these are the ONLY form of model that makes me want to hide behind something large and strong for my own protection.

[vintage1]

It reminds me of the time a friend from school turned up with what he prodly announced was his 'prototype cannon'

A piece of heavy steel tubing was trapped to a slab of wood with epoxy and one end had a bolt whammed into it, and a touch hole drilled into it.

He emptied out a firework banger, filled it up with about half, tapped a ball bearing down it, and we stuck some Jetex fuse in it, and pointed it at the nearest thing we could find. A cast mezak plate on the side of a tennis court, proudly bearing the makers name..about 20 meters way. We lined it up carefully at the top, thinking that the bullet drop would be pretty severe.

Then we lit it. There was a nice bang, and teh recoil shot it backwards 'Did it work?' he asked as I wandered, over the the sign 'did it hit the plate?'

After I showed him the 1/4" hole punched neatly through the 1/4" plate,with as far as we could tell absolutely NO bullet drop at all, he went very quiet..
"Well it worked, and that's the main thing: I don't think we should try it again, do you?"

We never did..


I heard via another schoolfriend that someone had tried out a twin pulse jet ME262 with reed radio gear..he said it had crashed within seconds and set fire to part of Epsom downs.

I don't think he tried a second time, either. ;)

[Sparky Paul]

...
I heard via another schoolfriend that someone had tried out a twin pulse jet ME262 with reed radio gear..he said it had crashed within seconds and set fire to part of Epsom downs.
.
I'd take that story with a dose of salts..

[BMatthews]

I just read my post and cannot believe how many spelling mistakes I made. I'm embarrased. But maybe it was just due to my fervent belief that pulse jets are best left to pass into extinction.

[canadian]

well, you'll know if i get one fired up, lol (im in delta)

[Tram]

I'd love to build one.. ;)

I say go for it canadian..

[Grejen]

I'd love to build one.. ;)

I say go for it canadian..
Sure, sure
Al. that's about as far from Vancouver B.C. Can. (and Delta) as you can get eh ? On this continent anyway. :p

[BMatthews]

About a year back I used my digicam to do a short video of the control line speed guys in our area starting and launching a model. Of course I needed my hands to run the camera so my fingers weren't free to stuff into my ears. When it caught I jumped a foot in the air not from the surprise but from the shear PAIN in my ears. Somehow I managed to film the 3 seconds needed for them to pull off the spark lead and air hose and let the demon from hell go. But my ears were ringing and dull for about an hour.

I was so worried for my camera's microphone that I ran another shot of just the guys walking around and talking to make sure it would still work.

I sure won't be doing that again without muffs or ear plugs.....

[Sparky Paul]

Sometimes I wish for a Dyna-Jet powered plane that would drown out the constant drone of the "experts" in the pits babbling on and on and on...
about stuff they have no clue about! :)

[Rodney]

The only successfull RC Dynajet in the USA to my knowledge was done by Al Signorino in St. Louis in the mid 50's. Biggest problems were keeping the jet running on takeoff, had to stuff the tank full of coarse steel wool to keep the takeoff acceleration from killing the fuel flow, had a dolly for takeoff and flights lasted at most about 3 minutes. To combat the heat from the pipe, the fuselage was painted with high temperature paint and take off had to be done as soon as the engine was started or the whole thing would catch fire (needed the airflow for cooling). If I remember correctly only two successful flights were made in about 50 or more attempts before the project was abandoned.

[BMatthews]

Sometimes I wish for a Dyna-Jet powered plane that would drown out the constant drone of the "experts" in the pits babbling on and on and on...
about stuff they have no clue about! :)


I don't know Sparky. That's a mighty tall order. You may need one in each hand for that....

[Brandano]

Has anyone ever flown a valveless pulsejet? this sort of thing: http://aardvark.co.nz/pjet/valveless.htm

[vintage1]

well that says it all about pulse jets.

Loud, almost impossible to throttle, and awful fuel consumption.

And dangerous.
:D :D :D

[Thomas B]

Long time local R/Cer and semi famous manufacturer of the Galaxy digital proportional radios back in the 1960s, Ted White, has shown me some photos of a OS pulse jet powered R/C model flying in the 1960s. Used a Jr Falcon wing. Went like stink.

All things considered, an R/C pulse jet model is usually not a good idea.

[heliman420]

im more of a heli guy myself but... for the last 4 years i have been studying pulse jets(ram jets, chineese valveless jet, lockwood hiller valveless and the common valved pulse jets), i have not built one yet, just done alot of reading and blueprint studying, i always wanted to buld one and put it into a plane, there are many pulse jet sites out there, this one in particular has some good BPs www.pulse-jets.com the one that stood out for me was ("craft plane") http://www.pulse-jets.com/count/pulse.php?ID=17 this little engine could supposedly power a small model, a year ago i saw a pic somewhere of this engine actually built, with a tiny tank and all, but i lost the site. this little engine uses only one valve, from what i understand it uses a simple 1 reed design and not a multiple reed like in the other models, the reed valve is made from .006 1/2 inch tempered feeler guage stock. i would suggest building something like this due to its size, PULSE JETS ARE VERY LOUD AND DANGEROUS AS HELL,i would take precautions in building any size of pulsejets.


(canadian) you can go to www.ridgeflyers.com in delta i know they fly micro turbines, there maybe pulse jets also but im not sure.

[heliman420]

a little update, i found some pics and build threads on the little engine on that site in the forums section, seems to need a lot of tinkering to get the unit to work but some people have got it to run perfectly, some videos of the engine running can also be found there, from what i undestand it make little thrust and has to be build light and to the exact specs of the plan ("tail pipe lengh criticaly important") to be able to power any type of craft, or to even run for that matter, making the spray bar seems to be the most complicated part of the build, all the info you need is on one site :)

theres a much simpler engine anyone can build, its called the lockwood hiller valveless pulse jet, its basicly a u shaped pipe thats has a large expansion on one side, but i wont go into details as there are sites for that, hope that helps you somehow :)

[SR71AK]

True Pulsejets are noisy but NASA and DARPA are spending big bucks on research. Noise yes, but, still possible.

I used to own a 1950's F94c Starfire and Tiger M1 Pulsejet. I sold them on eBay for over $1700 last Sep. The instructions said not to run it for over 20-seconds statically. The model was aluminum and the pulsejet fit inside. It was made by Suzuki Edwards.

I plan to install a pulsjet into a paper cardstock airplane. THe model is taking shape and should be ready for the engine installation this weekend.

Thermal barrier? I'm using ceramic paper sheets 1/8" thick. 2300 deg F max temp.

The model is a Fieseler Fi 103. It is a basic, simple to build model. It is also fairly strong. 55" Long with a 38" wingspan, RTF-weight will be around 3-lbs.

The pulsejet will reside within a paper nacelle that has 3-layers of the ceramic paper rolled into different sized tubes. The tube closest to the pulsejet will be in a cone shape trying to get some augmentation.

The third layer/tube will be glued to the actual card stock paper using high temp gasket sealer to create an additional air insulation space.

The valveless pulsejet has the following specs:
-3/4 lb wt
-2" Combustion chamber dia
-7/8" Dia x 10" long tailpipe
-Approx. Thrust = 1.2 lbs
-can be fueled by a small disposable bottle/tank of propane

Been designing/re-designing almost 1.5 years so far. Will soon know if it works!

BTW-Ceramic sheets are available from http://www.mcmaster.com/ along with just about anything else you can imagine!

http://www.beck-technologies.com/ Great videos, good designs, explains why some pulsejets don't throttle so well (Spot welding).

Mike

EDIT: Forgot to mention how the ceramic is going to be mounted. The first rolled "tube" of ceramic paper will be double-walled cone shape. It will be held in shape by the use of stainless steel wire frame and thin stainless steel wire will be weaved and wrapped to create a thermal insulation blanket.

The engine itself will be mounted to a small stainless steel strip 1/2" wide that will be "strapped" around the engine tailpipe.. The stainless is attached to a very thick lamination of paper card stock.

The model itself will tested to withstand 12lbs before the first flight. If not it won't go until It is able to pass a simple 4-g load test.

Launch will be by a "catapult" launch system.

My last attempt made it to 8lbs before deforming and tearing. This next design is smaller and heavier. (42" wingspan down to 38"). Problem is it decreases my air space insulation in the engine nacelle. Hopefully not too much though!

The real question and point to this whole project was the design challenge. I've tried several different answers, but not the right one yet!

Will it ever actually fly? Depends on many things-I'm not qualified to fly it, will someone that is be interested? Actual flight might just be limited to one if any!

It will however be run statically on the ground! Several times!