Dyna Jet Airplane on 90 Foot Lines

LAST EDITED ON Apr-29-04 AT 09:08 AM (CDT)
 
I met a guy at a swap meet that flies a Dyna Jet model airplane on control lines. He says his airplane is his own invention a copy of a Flite Streak with a Dyna Jet Engine mounted above the fuselage like the German V1 Buzz Bomb. It flies 145 mph on 90 ft lines. I didn't get to ask many questions the guy was in a hurry to look for bargains. This sound interesting.

I must have made a mistake in my math but I get lap time at 2.66 sec on 90 ft lines at 145 mph. Seems like it should be more like 4 second laps. The distance around the circle is 50% farther on 90 ft lines than 60 ft. lines. There must be an easy formula to calculate lap time?

The wings must be solid balsa I would think a normal Flite Streak would self distructs at 145 mph.

I have a Dyna Jet engine laying on the work bench. I could build an airplane but I would fly it only if the lines are long enough to make 5 second laps.

My question is, what diameter lines would it need? Will it have enough centrifical force to keep the lines tight? How long do the lines need to be for 5 second laps?

First, I haven't done the calculations, but on 90' lines, there's no possible way a DynaJet could push a FliteStreak-size plane at anything approaching 145mph! I flew DynaJets back in the 70s, and thin-section trainers could approach 120mph on 60' .021 cables. On 90' the line drag alone would slow it down way more. (The drag gets MUCH greater on longer lines.)

There was some interest in DJ stunt in the late 50s-early 60s, fut fuel feed and flame-out were major problems. Heck, fuel-feed and flame-out are major problems with DJ-powered speed models which fly straight and level!

I'd ask to watch a flight and have a stopwatch handy.

You are not far off with your math it rounds off to 2.66 sec. laps at 145 mph. I've seen a flite streak less wheel and fin go 110 on 60 foot lines with a .40 using bladder pressure. The flite streak used combat cat wings which are only 1.5 inch thick. I think the frame could do 145 with out falling apart, but not with 90 foot lines and not with any dynojet I've seen.

Did you roll up your pant legs in front of him or just give him a blank stare?

The formula for calculating speed is in the AMA rulebook.

--jt

>I met a guy at a swap meet that flies a Dyna Jet model
>airplane on control lines. He says his airplane is his own
>invention a copy of a Flite Streak with a Dyna Jet Engine
>mounted above the fuselage like the German V1 Buzz Bomb. It
>flies 145 mph on 90 ft lines. I didn't get to ask many
>questions the guy was in a hurry to look for bargains. This
>sound interesting.
>
>I must have made a mistake in my math but I get lap time at
>2.66 sec on 90 ft lines at 145 mph. Seems like it should be
>more like 4 second laps. The distance around the circle is
>50% farther on 90 ft lines than 60 ft. lines. There must be
>an easy formula to calculate lap time?
>

From speed and line length? Very easy.

The radius of the circle is 90 feet (ignoring the length of your arm). The total distance around the circle is the circumference, or

x = 2 x pi x radius

where pi = 3.141592... = transcendental number that is the ratio of a circle diameter to it's circumference for any circle
radius = line length = 90 feet

or x = 2*3.141592*90 = 565.5 feet

145 miles per hour = 145mile/hour*5280 feet/1 mile*1 hour/3600 seconds = ~213 feet/second

lap time =distance/speed = 565.5 feet/213 feet/second = 2.655 seconds

The line tension is the mass *V^2/r

or in this case weight(lbf)/32.174 ft/s^2 * 45369ft^2/sec^2/90feet

or weight(lb)*15.67

There's no way a stock Dyna-jet is going to fling a Flite Streak on 90 ft lines around at 145 mph. With .018 lines, fully 1.3 HP is going into the lines alone. Assuming 5 lb of thrust at speed, a Dynajet is putting out 1.94 HP. The airplane will require about 2.75HP, so the total HP required is about 4.0 HP - or more twice as much as the Dyna-jet can put out.

LAST EDITED ON Apr-29-04 AT 04:31 PM (CDT)
 
Young Daniel regularly completes the whole pattern flying 2.2 second laps with his Dyna/Ring (56' lines, eye to eye). He reports that there is no "whip-up" whatsoever, either.

See Ya

I calculate the speed at 239.8 mph. Is that correct?

Looks like a built up wing to me. I figured the wing covering would rip off at that speed.

Why does it have an engine with a propeller and a Dyna Jet engine too?

It seems logical that the model airplane engine could go fast enought for ram air to start the Dyna Jet in flight if the dyna jet has an ignition system.

My calculations show slightly more than 120 mph.
60 foot lines (handle face to center of thrust line) requires 7 laps for 1/2 mile. 7 times 2.2 is 15.4 seconds for a half of a mile or slightly less than 120 mph. take off a couple of feet of lines and you will be slightly over 120mph but nowhere near 200+.
Bigiron

>I calculate the speed at 239.8 mph. Is that correct?

No. Speed = distance/time 56' lines +2 feet for arm+2 feet for wing = 60'

Distance around a 60' radius circle = 2*pi*radius or 2*3.1415*60 = 377 feet. Time is 2.2 seconds.

speed = 377'/2.2 seconds = 171.36 feet/second = 171.36*(3600/5280) = 116.8 mph.

>>I calculate the speed at 239.8 mph. Is that correct?
>
>
> No. Speed = distance/time 56' lines +2 feet for arm+2
>feet for wing = 60'
>
> Distance around a 60' radius circle = 2*pi*radius or
>2*3.1415*60 = 377 feet. Time is 2.2 seconds.
>
>speed = 377'/2.2 seconds = 171.36 feet/second =
>171.36*(3600/5280) = 116.8 mph.
>
> Brett

Yu rocket dudes has way tu much fun with yur calkulaysuns!
Anywhur aroun' 100+ myles pur hour is way tu durn fas' fer me!

Jake

Shame on you Peabody! Why not show the one where Young Daniel has his Dyna-Jet powered SE5-A?

Scott....I think it's a Fairley something French pusher.
He flew a 525 with that one once.

See Ya

LAST EDITED ON Apr-30-04 AT 01:08 PM (CDT)
 
Scott Riese,

Are you checking in here? Peabody has posted a picture which ought inspire you to do something really interesting with the 60-size Bi-Slob you're always quacking about.

But don't for simple parity: Your model has two wings. Install two jets.

Do be certain to place exhaust tube(s) close to rudder, as seen in above photo.

LAST EDITED ON May-01-04 AT 08:54 PM (CDT)
 
I believe a Flight Streak would hold up at that speed.I had one back in the seventy`s that was clock at 121.53 with a K&B 40 rear intake.If you find it hard to believe then ask Phil Granderson or Bart Klapinski.Phil did the clocking.And Bart flew it though the whole pattern with bottoms at 5 ft. He makes me sick.What a geat pilot.

Gordy

>I believe a Flight Streak would hold up at that speed.I had
>one back in the seventy`s that was clock at 121.53 with a
>K&B 40 rear intake.If you find it hard to believe then ask
>Phil Granderson or Bart Klapinski.Phil did the clocking.And
>Bart flew it though the whole pattern with bottoms at 5 ft.
>He make me sick.What a geat pilot.
>
>Gordy

Klapinski could get a 500 point pattern with a brick on a string!

Peab,

I think you've been living too close to that Brooklyn bridge that hucksters have offered for sale.

>Young Daniel regularly completes the whole pattern flying
>2.2 second laps with his Dyna/Ring (56' lines, eye to eye).
>He reports that there is no "whip-up" whatsoever, either.

Nice Photoshop work...

Cy

Actually, the plane in the picture has NOT been altered or retouched. Young Daniel drug the critter out at a New Years Follies 2002/2003.

Young Daniel is FAMOUS for his flying of the Double Sized Flite Streak, and does a mean bi-slob, too.

See Ya

Okay Peabody, ya got me all excited thinking about Brodaks and Danny doing his thing with his giant FliteStreak while Mary's husband plays the Star Spangled Banner Jimmy Hendrix-style on his electric guitar.
Can't wait, can't wait, can't wait!

Gary, Sounds like a bit of smoke here to me. Even in the earliest days of the Dyna Jet era did they fly on 90 foot lines. 70 was normal.
My last jet ship is in the museum in Muncie now which last flew in 1955 or 56. Too old to remember. Anyway, I'd ask the fellow for a demo.

Sunshine

LAST EDITED ON May-01-04 AT 00:19 AM (CDT)
 
I know, could't fly without a major center swivel post.
Havnt done since chuck was going for the records.
I still have ralphs u2 96" R/C plans and a german pulse jet.
Japanese f84g metal kit fs.
Roger

I think this formula will give you a pretty good approximation.

4.29(line length in feet/time for one lap in seconds) = airspeed in MPH.