Building an RC Pulse Jet Powed Airplane.

MikeInOr said:
I thought pulse jets relied on having a certain amount of incoming air pressure to operate? I.e. The pulse jet would not ignite and stay lit until it was up to a certain air speed? Basically air speed compressing air into the intake took the place of the rotary compressor?
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The length of the exhaust tube is designed so that the inertia rush of exiting gases from one pulse creates a suction at the intake, bringing in more air for the next pulse, no moving parts other than the metal reed valve.
 
What Bob said, Bob is much better than me at explaining things in an understandable way.

Abowie said:
Pulse jet = forest fire in the making. Do test flights over water.
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Our flying field is in a flood plane and has swamp on 3 sides, (Great for keeping development away) the one side that is not swamp is the pit side which is a no fly zone.

With all the rain we get here, there is nothing dry. The electric aircraft with the big LiPo batteries are actually the most likely to cause a fire after a crash. I also do carry my own fire extinguishers with me in addition to the seven ABC extinguishers that the field owns. I have a 10 lb C02 for a fuel fire and a 2 gallon Water based for grass fire. And the fire department is within a half mile, we can see the station from the flying field.
 
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Given what this is, you might consider flying it before investing a lot of time into paint. Being blunt, there's a fair chance that this won't end well so no point making it all purdy first.
 
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My only experience with pulse jets was when I was about 16 years old (mid 1960's.) I was into U-control combat, where two planes go around circles by being restrained by the two guys who are flying them with double wires going from wrist controls to the aircraft. By pulling on the alternate wires, the plane could be made to go up or down. My poor memory seems to remember the wires being 50(?) feet long. The "pilot" had to turn with the plane so he was always facing it. The planes I built and flew were classes 1/2A and B, and the class B could go about 105 mph in those days (on longer wires.) The planes each had crepe paper streamers tied to the tail, and the game was to cut off your competitor's streamer, without crashing into his plane or the ground. It was loads of fun. The planes are super light and can turn on a dime. Needless to say, they do not last long, and it is important to be able to build them quickly and in some quantity.
It was easy to get so focused on the chase that we would follow the other plane right into the ground.

At one contest I saw a U-control pulse jet aircraft demonstrated, just the engine with a couple tiny wings hooked to the sides of it, no fuselage, and also half of a horizontal tail that had a small moveable trailing edge (elevator). It was incredibly fast. It was the only one I ever saw flying. Wait, I found a video of one:
 
Somehow the term "relaxing" doesn't come to mind.
 
I found the combat flying very relaxing. If you watch near the end of the combat vid the 2 pilot are going in circles flying and neither one is even looking at the plane they are flying, Once you learn how you can be very relaxed while flying. Now with the pulde jet speed plane, you notice the pilot is hanging onto a pole for dear life while going round and round, that does not look relaxing, but who knows, once you are used to it, it may be very relaxing, Or the relaxing part might be right after the flight while you are coming down from the Adrenalin high?

Back 50+ years ago I got started in this nonsense with U control combat. I flew 1/2A combat, Slow combat, and fast combat. The 1/2A used 30 foot lines and all the others used 60 ft lines, the lines were .018 Ø stranded (stainless?) steel lines. The Slow combat planes were around 110 to 120 MPH and the fast combat were around 140 mph I am not sure how fast the 1/2A were but I would guess they were around 60-70. With the 60 foot lines 7 laps was almost exactly 1/2 mile, so it was easy to get your speed by timing it for 7 laps. At 140 MPH from a point directly over head which is as far from the ground as you can get, it only takes 1/4 of one second to be planted into the ground, that is how long you have to decide which way to turn. AHHhhhhh the good old days. We (a group of 4 of us) were going thru a gallon of Missile Mist a week just in the 1/2A. That is a LOT of flying at 1/4 to 1/2 oz per flight. I have no idea how many gallons a week went thru the bigger planes, but we went thru several 55 gallon drums a year.
 
Well I been masking and paintin like crazy. I never realized just how much masking this paint scheme required. A painter I am not, and never will be. I just squirted on the final coat of color, Now I just need to cut and apply the vinyl graphics then clear the whole thing, then apply the final heat shields and trim tape and the finish will be done.
It does not look anywhere near as good as what most of you do. There are a lot more bumps and divots than there should be, but at 250MPH, no one will notice.

I just put the last color down a few minutes ago and will unmask it to see for the very first time tomorrow. Hoping to get to the clear coat this weekend.

I did order some Titanium bars to remake the engine mounts. I was concerned that the aluminum will be to close to some very hot parts and did not want to risk it softening while near red hot stainless steel. The other option was to make the parts out of steel but they are mounted right at the trailing edge of the wing and weight added to the tail has to be avoided, I an anticipating having to add a ton of nose weight. The TI will save some weight over the steel and be more than adequate to handle the temperatures. Hopefully I will soon have some pics out in the sun (IF the sun EVER comes out here again)
 
If you are clear coating over the graphics may i offer a suggestion that may save you down the line just incase???
There is a good chance that the stickers may cause an off-gassing problem which could ruin the paint job. To help guard against this I recommend laying down a couple nice layers of clear coat first, let dry then lightly scuff and wipe with isopropyl alcohol before adding the graphics then wipe with iso again and finish with a few coats of clear. This protects the main color work you did in case there is a finish problem. And if there is you can carefully sand off the problem down to the graphics to try again without destroying all that hard work.
 
Great thread. I fly rc planes and have seen pulse jets fly. To those who question, if you fly turbines you will be fine with a pulse jet. Just fly simpler patterns.
 
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