Spacemonkey71

I made it to the LHS (which isn't exactly "local", like 65 miles.....) but there was a guy who was about to maiden flight his scale F16 gas turbine jet so I HAD to stay and watch! This thing took almost a gallon of fuel and when he lit it up..... OH MY GOD !!!!!!!!!!! My jaw hit the ground like the Victoria Secret's models had just strolled across the field naked! I was BLOWN away by this thing. I had to ask a few stupid questions, the prime one being, " um... how much does a setup like that run?" (this was to the shop owner NOT the plane owner... He said the engine was around $8,000 and he had about another $2,000 worth of "toys" added on [X(] a TEN THOUSAND DOLLAR PLANE ?????? [X(] [X(] [X(] )

I have to admit, when this thing took off, the noise was absolutely DEAFENING! It sounded JUST like a "real" jet taking off and when it made a couple of passes at speed, it was INCREDIBLE. He landed it dead-on-balls PERFECT too. This guy was OBVIOUSLY a heavy veteran pilot and after the flight, his hands were shaking like a palsy patient! It's great that we're in a sport SO COOL that someone with 20+ years of flying experience can STILL get that "shake" after a maiden flight! It was very, very cool

I'm glad I finally got to see one of these things flying after hearing about them for a while, but I'll be a lottery winner before I EVER spend $10,000 on something that MAY or MAY NOT turn itself into a heap of splinters b/c of a million different reasons! I thought the plane was truly amazing and REALLY incredible to see fly (and HEAR fly!) but I ain't NEVER gonna go THAT far in this sport I love flying, but there IS a limit to my enthusiasm [&:] I admire all of you out there that DO spend that kind of cash on jets, but you're playing in a league that is WAY out of my reach

Jetdesign

My Feedback: (8)

What I'd like to know is: what's the point of the turbine? In 'real-life' they are to generate power for a compressor or to spin a fan or something. Since our models don't have compressors or fans, don't they just need the afterburning part of the process?

I'm psyched you got to see the jet, I would LOVE to see, hear, (and feel?) one. I wish I had that kind of disposable income. I imagine what that guy felt after his flight is pretty similar to how I felt maidening my VII - believing in relativity.

ChuckW

Not sure what you mean. To my knowledge, model "jet" or turbine engines have a fan, compressor, combustion chamber, etc. They are pretty much mini versions of large aircraft engines.

I have never flown one of these myself but I've sat and watch many of them. I have never seen one or heard of one with an afterburner.

http://images.google.com/imgres?imgu...icial%26sa%3DN

If you ever have an opportunity to see a large jet event, do not miss it. It is an entirely different, "hard core" side to the hobby. Our club is having the anual jet rally later this month. Although I won't be able to participate, it's going to be a great weekend of watching and spending time at the field.

http://frcm.org/images/Jets2007/index.htm

These definitely aren't for beginners. It takes tons of knowledge, tons of experience and of course tons of cash.

JohnW

My Feedback: (6)

"What I'd like to know is: what's the point of the turbine?" - Power, speed, sound, smell.... Did I say power and speed yet? The model turbines do indeed have a compressor, and work on the same principle as their larger brothers. They even burn the same fuel. You can get into turbines for less than the $10K listed. Not for beginners as mentioned. In addition to knowledge and experience, I'd add discipline, i.e. ground preflight before every flight, etc. My baby's pic is attached.

brett65

My Feedback: (18)

A jet engine and a jet turbine are the same basic thing with the difference being that the jet uses it's thrust for movement i.e. "jet" and a turbine is used to drive something else for power. Helicopters use jet turbines to drive their blades, C-130s use jet turbines to drive the props. Jet engines use compressors to compress the air which makes it hot and ignites the fuel that is sprayed in, which expands to push quickly out the back (jet) or simply increase the speed of the engine connected to a drive gear. The compressor is made up of all the fans. Confused yet?

JohnW

My Feedback: (6)

Jet engine, jet turbine, gas turbine, all the same thing - Compress and heat air, throw in lots of fuel, fire!, spin whirly gig in back, watch bearing life tick away, send in to have bearings replaced, rinse and repeat. Sure, some will dump their energy into a second turbine to provide mechanical power, such as helis or turbo props, but still all the same basic gas turbine engine. - Cheers

Spacemonkey71

It really occurred to me today as I was watching this thing prep and takeoff (and you're DEAD ON when it comes to SEVERE preflight dicipline!!!) that these kind of craft are not even in the same LEAGUE of any other plane I've EVER seen! I don't think I saw a SINGLE thing inside that craft that I definitively recognized other than the fuel tank and what was (obviously) the jet engine! It was a WHOLE different type of craft! (and PERFECTLY built to scale too! This guy took some TIME putting this bird together!!!! it was FLAWLESS!!!)

....... and a GREAT way to turn a GIANT sack of money into noise!!!! I'm still dumbfounded that people ACTUALLY spend that much cash on a plane! I guess I shouldn't be TOO suprised.... I used to modify cars and I've seen $20K+ put into Honda's! (mind you, afterwards, they'd blow an 11 second 1/4 mile! >>that's in the range of a Z06!) and still drive to the grocery store!)

If you EVER get the chance to see one of these things fly, let me tell you, DO NOT MISS IT! The speed is absolutely mindblowing and the NOISE is INSANE!!!! I (somewhat stupidly) put my hand about 10' behind it near the ground while he was "running it up" and WOW![X(] That was SUPER HOT![X(] (DUH!!!!!) It smelled like burning propane too (like a gas grill on full blast waiting for a steak)

ohnoucdat

My Feedback: (16)

I was lucky enough to see several jets at a field in Hickory, NC. The sound and speed was unbelievable, Go fast turn left, that was it other than landing. Still it was like nothing I ever seen,my friend had his son there with us, he asked one of the gentelmen what he had in the jet. He answered by saying I got about as much as my wife has in her corvett. I'll take the vette you can pick up chicks in it, and it makes right turns LOL.

Jetdesign

My Feedback: (8)

Spacemonkey, what was it made of? Balsa and covering? Sheathed in wood? How big was it? And how big was the field?

Thanks for the clarification for the above question. I guess I just didn't understand the point of any 'spinny things' on a model aircraft. I saw a diagram of one model 'jet' engine, and it had some fancy static compression system built in the front of it, so no mechanical compressor. When fuel is dumped into the hot compressed air and ignited, you get thrust. On full scale commercial airplanes, MOST of this thrust is used to spin a turbine, i.e. generator, which in turn spins a fan (turbofan) or a propeller (turboprop), the compressor, and any supplies power elsewhere. I just didn't see where the model plane needed that much power, but again didn't know there was a compressor. Full scale military jets use less of the energy to spin the turbine and use most of the energy for thrust, sometimes re-igniting the exhaust gases for more thrust (afterburner). The 'spinny thing' doesn't create any kind of forward movement in the aircraft; it only generates power.

beau0090_99

Hey Gar,
When you get through school, take a turbines class, it will blow your mind. Very fun.

Anyway, you are mostly right on your assesment of turbines. Commercial engines do drive a fan, but some part of that fan(the center section) is the first stage of a multiple stage compressor(sometimes between 10 and 20 stages of compressor and stator vanes). Take a P+W JT8 used on DC-9's and 727's, roughly 50% of the air coming into the engine is sent through the engine, and the other 50% is bypassed around the nacelle and simply used for thrust. But, the 50% going through the engine is compressed to something like 17:1 and then fuel is mixed into it and ignited. The burning gases exit through the turbine stages (multiple stages) which spins the rotor(s) and turns the fan and the other stages of the compressor. Remember though, the gases leaving the back go through a convergant/divergant nozzle, which you will find out in your turbines class actually accelerates the gases past the Mach point, which creates an incredible amount of thrust. This is probably the loudest part of the process, because the gases are consistantly breaking the sound barrier (creating a static sonic boom). If you are amazed by the power of a turbine, you will be shocked by how that happens in a ConDiv nozzle. On a military jet, they do use an afterburner, but they actually inject more fuel into the nozzle and ignite that. Once that fuel is lit, the ConDiv on these jets will flex to adjust the Mach point to the narrowest point in the nozzle. On the model jets, the condiv's are fixed like that on a commercial jet, but they only use the thrust coming from the ConDiv, because they don't employ a fan that has any bypass. On newer commercial jets, with newer engines, they employ a higher bypass ratio, like 80:20, which is designed to make the engine more efficient and actually quieter.

Check out Wiki pedia, I am sure they have more info about this, but I would recommend digging into it, it is a lot of fun, and a very cool concept.
Regards,
Curtis

beau0090_99

Gar,
To your point about the fixed compressor thing, what you might have seen is a RamJet. It uses a diffuser, which is just a way of slowing down the gas using Bernouli's principle and then a ConDiv to blast the gases past the mach point, but these need to be moving already at speed to generate compression, so you would find them on a air to air missle which is launched off of a wing.
C

MinnFlyer

My Feedback: (4)

RC Ken and I just got back from the D.O.G.S. show in Dayton, Ohio where (among other things) there were many jets. We got some great pics and videos which will be posted in our write-up in RCU Magazine which will be posted very soon!

bruce88123

Don't know if you you know it or not but commercial airliners don't use afterburners and some of them develop more thrust per engine than ANY military engines do. The British SST aircraft did have afterburners on it. The new F-22 jets do NOT have afterburners but still obtain high mach numbers via "super-cruise" technology.

RCKen

My Feedback: (9)

Here are some of the craft that had turbines in them at the DOGS show. And yes, the Huey is powered by a turbine. It was truly an amazing model, as you can see in the picture, it's hard to tell it from the "real thing".

Ken

Spacemonkey71

Garc, the plane might have been a Skymaster F16 (....I think - but I could be WAY wrong on that! I know VERY little about jets!). It had about a 40"-50" wingspan, was ~60"-70" long(?). It definitely was NOT made of balsa or covered; it had a hard "shell" on it (maybe a fiberglass overlay? or a thick plastic? totally not sure). Under the "shell" was wood, but I don't think it was balsa, it didn't "look" right to be balsa; the grain wasn't as fine as balsa usually is and I don't know how balsa would hold up to "blast furnace" level heat - even with a TON of shielding materials. Like I said, I know almost NOTHING about RC jets. The VERY 1st one I ever saw was yesterday and I just happened to be there when the guy was maiden'ing it. It was just dumb luck that I got to see it up close and watch it fly.

At a guess, I'd estimate that the field there is about 450'-500' long and 250'-300' wide and laid over with "putting green" style golf course grass; very short blades, very dense, VERY nice! Big 400 acre cotton field on one end and a few trees at the other end and the opposite side are some trees too. It's an EXCELLENT field!

The shop I'm talking about is Mac Hodge's shop "Hodge's Hobbies". He flies a GIGANTIC B-29 that's been featured in several magazines (it's something like a 20' wingspan - no kidding!). Hit http://www.hodgeshobbies.com/home.html for his webpage. He's got tons of pics of his shop, the field, different "special" planes that have flown there. People come from other STATES to visit his shop > it's THAT good! The shop is like CandyLand for RC nuts My wife has basically FORBIDDEN me to be within 20 miles of it because there is NO way to go there and NOT pick up SOMETHING because he has EVERYTHING imaginable (and a few things you can't imagine too!).
He's even got a beautiful yellow labrador named "Servo"

Mac's plane is going to be featured at the Warbirds Over Atlanta 2008 just north of Atlanta, off of Ga400. Hit www.gmarc.com for more info on it. I WISH I could be there, but I've got family obligations I can't get out of (YET!!!)

Btw, on the webpage there's a "history" of the B29 build. The "original" one crashed about 10-15 years ago, so this is "incarnation #2" he's got now. I've uploaded the only picture I could find of the current one on the webpage (it's a small picture, but with Mac behind it, you get the idea of the scale of it; MASSIVE doesn't even BEGIN TO DESCRIBE THIS BEHEMOTH!) It still drops Yeager's Bell X1 out of it's "belly" while in flight though! (yep, you read that correctly, he has a SEPERATE plane, the "Bell X1", mounted BENEATH it and it "drops" it into a "rocket flight" while it's in the air, just like Yeager's soundbreaker!)

I think Mac's motto is something like, "If you're going to GO, go BIG and with STYLE!" He's a great guy who runs a great Class A shop!

brett65

My Feedback: (18)

HOLY CRAP! There's a dude sitting in the side door of the huey! If the blades weren't white, I would say that you took that of a real one and were just pulling our leg!

DadsToysBG

My Feedback: (35)

Don't get the wrong idea about jets. Many of them can be had for 5 to 8k. That puts them in the same price range of GS and thats only for the first one. I've seen jets hang on the engine and do 3-d. I've got my first one used ready to fly less the engine and with a new P-70 I'll have less then 5 in it. Dennis

RCKen

My Feedback: (9)

In the last issue of MA they talked about getting started with turbines. A turbine trainer can be set up for $3,000-$4,000. While not cheap, it's not as bad as a $20,000 scale jet


Ken

hungryandbroke

I'm thinking about putting a Turbine on my Goldberg Piper Cub.

The os 46ax I have on it is about wore out.

CGRetired

My Feedback: (1)

Now consider the scale (not sure of the scale level but it was huge) model B52, with 8.. count em... 8 turbines. There is a thread here somewhere about the one that crashed in England. Consider the cost of that crash!!


Link:

http://video.google.com/videoplay?do...73582041454459

CGr.

brett65

My Feedback: (18)

Yeah, you can see the guy crying at the end, I almost don't feel sorry for him cause he knew how much of a risk he was putting his money in.

Spacemonkey71

"Don't get the wrong idea about jets. Many of them can be had for 5 to 8k"

....oh, now that you put it THAT way, they sound reasonable.... heck, buy 2, they're small <jk>

I can already hear this conversation, "Honey, I know we need a good used Honda Accord for the kids, but I REALLY want this jet!"

ohnoucdat

My Feedback: (16)

Lmao Well you could just get 1 jet and the honda, sorry you couldn't get 2 jets, get the jet that does 3-d if you can only get 1. This I gotta see lol

Bob Mitchell

Oh, it's real all right!. I'm in Lexington, KY, only about 90 minutes south of Dayton and I believe that the Huey belongs to one of our clubmembers, based on the nose art and the pilot/gunner figures. He first brought it out at out Warbird flyin a few weeks ago, but a leaking oring prevented him from flying it. About a week later I arrived at the field just as they were mounting it back on the dolly he uses to transport it. It had landed just moments before I got there.

Up close the detail is just awesome.

Bob Mitchell

They are awesome to hear and watch. I saw my first turbine flight about 3 months ago at the Kentucky Jets fly-in about 40 miles from Lexington. There was a guy flying a large F4 (8-10' fuselage) and it was a thing of beauty. As you said, the sound is the same as full scale. The mini turbines have the same working parts as full scale jets.

Last month's MA had an article about scale turbines that was very informative. They've come far enough now that the computerized control units have made start up essentially push button, with the ecu monitoring key temperatures, etc to bring the thing up to idle power. I saw the F4 with a couple of hatches removed and the wiring/plumbing is intimidating looking to say the least.

Unfortunatly I also saw my first jet crash. Another large F4 lost power downwind and relatively low. The pilot had good control but unfortunatley was not able to completely line up with the runway and came in at about a 30 degree angle upwind. The ground slopes down on the far side of the runway, and he lost sight of the plane just a few feet off the ground. The next thing you saw after the tail disappeared over the slope was the bouncing cartwheel.