90% RUHRSTAHL KRAMER X4 (1944-1945)

[CarVac]

How did you control deployment? It looked like it ejected way after apogee.

 

[legranddudu]

This is right. It was my mistake. Both Altimeters were setup with 2 seconds after apogee. This was nearly fatal. I will change this next flight for sure...

 

[dixontj93060]

Denis, can you comment on the flame present during the ejection charge--never seen that before? Could this be NOX leaked inside the airframe?

 

[patelldp]

Denis, can you comment on the flame present during the ejection charge--never seen that before? Could this be NOX leaked inside the airframe?

Pretty sure in other threads (maybe his V2?) he states that they cannot buy 4F black powder. The powder they use is slower burning at a lower pressure, this requiring more to eject and a little more of a "signature."

 

[legranddudu]

Thx for questioning: in fact I did not use BP but what we call "pyro-flakes". It is in fact nitro cellulose. I prefer instead of BP.
Pyro-flakes burn with nearly zero residual tracks. It is very clean and powerfull burning with lots of gaz...In that particular case I used...maybe too much of it *lol*, definitely not a NOX leak....but it is no particular problem, it just works perfect and the chute is protected anyway. In the in and outside you would find zero tracks of that ejection.
The good in nitro-cellulose: it can be send by normal post. It arrived wet so burning is impossible in transportation. You just need to dry it for a while in the sun or any device giving little heat but constantly..but not in your hoven! *lol*...I have heard stories about flying hoven doors thru the kitchen... )

In Germany Dan we can get (with appropriate permits of course) nearly every kind of BP. Only thing I missed are compressed pyrodex pellets from Hogdon. These are not imported unfortunately.

 

[bobkrech]

this is the first flight of the 90% KRAMER replica in slow motion. Happened in Italy near to Bologna in July 2013. The rocket has shown a very stable flight but...the K contrail hybrid motor unfortunately was wrongly half-filled AND in very hot conditions (34°C/94°F) at the start and could not properly bring the rocket into a safe flight level (planned 1500ft). It turned to be a 300ft jump...fortunately the parachute could prevent damages and the rocket is ready to go for a 2nd flight...

Enjoy the crash...

[video=youtube_share;kSEotPMLpBY]https://youtu.be/kSEotPMLpBY[/video]

You are very brave to launch a hybrid at 34C as it is so close to the critical temperature of 36.4C for nitrous. Most folks would not consider launching if the temperature is over 30C because of the low density of the liquid phase and the difficultly in maintaining sufficient liquid in the flight tank.

 

[legranddudu]

Bob,

you can name it... a bit scilly/stupid it was but ...we were simply too excited and 2 hours before in even higher temperatures we had a huge flight with the cowabunga XXL without any problem, so we decided to go. But the bottle was much colder in contrary to the air temperature....So we understand now that we went just that close from loosing the bird, next time we want to be much more cautious. Nevertheless I need an electronic device at the ramp to weight the bird in the tanking process. We are going to develop this quickly...

Denis

 

[Daddyisabar]

Awesome flight characteristics under power and talk about pulling it out at the last second! This one has a charmed life after only one flight. The old rocket gods must have wanted to see this one fly again, all painted up on a brisk winter's day.

 

[bill2654]

Now THAT"S some cool German engineering! Awsome rocket Denis.

 

[legranddudu]

Bob,

I found last night the real primar reason for the poor motor performance. cleaning the casing (finally) I found...the single port injector with an 1/4" presslock instead of a triple port injector with 3x 3/16" as recommended by the manufacturer to fit the XFast nozzle. The motor could not come into enough pressure and the performance was terrible. The temperature and the nitrous bottle coming to an end made the rest...

conclusion: always read the F* manual first...

You are very brave to launch a hybrid at 34C as it is so close to the critical temperature of 36.4C for nitrous. Most folks would not consider launching if the temperature is over 30C because of the low density of the liquid phase and the difficultly in maintaining sufficient liquid in the flight tank.

 

[Leo]

On Saturday I had the joy of witnessing the second flight of Denis's Ruhrstahl Kramer X4.

Even though we had scorching heat, which isn't Hybrid friendly, we all watched a fantastic flight fold before us.

I have to admit that I would have put my money down for an unstable flight but I was gladly proven wrong.

Here Denis prepping the Hybrid:

Getting closer to launch:

Last man from the launch pad:

Liftoff!!

The Kramer has cleared the launch pad under hybrid power:

Now we are in coast phase near apogee:

We have a deployment!

Chute fully deployed with a nice slow decent:

The Kramer touches down:

Here is a happy camper!

 

[Daddyisabar]

With lots of power and the right amount of nose weight any thing will fly! Hopefully this success will inspire our big V2 Hybrid flying club member to get his stuff out of the garage.

 

[Cl(VII)]

That is fantastic. I hope video will come along, I like that hybrid roar.

Congratulations, Denis.

 

[qquake2k]

Looks like it was an incredible flight!

 

[Leo]

It was a picture perfect flight. Now I hope it will get a nice original paint scheme.

 

[legranddudu]

thx Leo,

here a few more from Andreas Harder (his copyright, thx for sharing!)



The motor I used was a contrail K555 with a black gold reload, XF nozzle, 3x 3/16 injectors and the 48" casing.

 

[dixontj93060]

I think this bird has now earned its right to be painted properly!

 

[Eric1]

Thank for sharing the photos!! Great Flight Denis!!!

 

[burkefj]

That's my kind of rocket, lots of forward fins and lots of noseweight Nice job!

Frank

 

[CCotner]

Holy crap, how did I miss the original launch posts! SO AWESOME!!

 

[V2rocketeer]

very nice long boost,, sorry about the landing. I can't wait to see the next flight

 

[Albanach]

What was your motivation for the wing materials?