Rheintochter / Rhine Maiden

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gosh she looks awesome Astro! sorry to hear about the masking tape struggle....for what its worth, I have found Tamiya tape to be the best for taping over painted surfaces but even still, there are times it will peel up the under layer of paint. This rocket is just super cool!
 
NJRick said:
gosh she looks awesome Astro! sorry to hear about the masking tape struggle....for what its worth, I have found Tamiya tape to be the best for taping over painted surfaces but even still, there are times it will peel up the under layer of paint. This rocket is just super cool!
Click to expand...

Thanks Rick....i do have soma Tamiya tape but didnt use it as I wasnt worried too much about a bit of bleed on the camo. One of these days I will get a build where everything goes right maybe :) how do people like sodmesiter do it I wonder...thay have like crazy good skills.

If the weather plays ball Rhine Maiden will get its first flight this weekend and assuming we get some video ( ie the bird flys straight and we get footage instead of a skywriter where everyone dives for cover) I will get some pics and/or vid posted.
 
I hope the weather cooperates! can't wait to see the pics!
as for Sodmeister.....he is just in a different realm than I will ever be...just an unbelievable craftsman.

Astro-Baby said:
Thanks Rick....i do have soma Tamiya tape but didnt use it as I wasnt worried too much about a bit of bleed on the camo. One of these days I will get a build where everything goes right maybe :) how do people like sodmesiter do it I wonder...thay have like crazy good skills.

If the weather plays ball Rhine Maiden will get its first flight this weekend and assuming we get some video ( ie the bird flys straight and we get footage instead of a skywriter where everyone dives for cover) I will get some pics and/or vid posted.
Click to expand...
 
LAUNCH REPORT

I finally got to fly Rheintochter today. Weather was clear and bright with minimal wind so we loaded up and set-off for a launch site.

Both flights were flown off of an Estes D12-3.

First Flight - Took off straight as an arrow with no observable body roll and flew to an estimated 200'. At ejection the parachute was ejected but failed to deploy and Rheintochter made a tumble descent into long grass with no apparent damage. She was reloaded and returned to the pad for launch No.2.

Second Flight - Took off straight and true but immediately prior to ejection the rocket veered off course violently. Ejection deployed the parachute which bought he down softly into long grass but on inspection she had cracked a rear fin in two places. Given the softness of the landing it was hard to believe the landing impact was responsible and I believe that the first tumble landing had weakened the fin which then failed on the stress of the second launch causing her to veer off course once the fin broke up enough. I just cant believe landing impact was responsible given the very soft, long and lush grass she came down in and it would explain the sudden strange flight behaviour on the 2nd flight.

It was tempting to attempt on the spot repairs for a third flight but I decided to abort and come home - any further damage to the fin would upscale the repairs from a minor repair job to possibly a larger more intricate job and I was dissatisfied with the mylar chute arrangement.

Verdict - Flies a charm and will be flying some more after minor repairs to the fin and replacement of the mylar parachute with a a bin bag chute for more reliable deployment. The recovery bay on this rocket is quite tight and the mylar chute is always a tight fit.
The basic design appears sound and the rocket showed a much higher degree of stability than may have been expected. I would bet that she needed far less nose weight than I put in and that simulation software does not accurately model the CP for this bird.

I will get a video up in a day or so so you can have a look.
 
Here's the Video

[video=youtube_share;TjDkAslJYx8]https://youtu.be/TjDkAslJYx8[/video]
 
Thanks guys...a big relief for me that it worked. I was beginning to doubt it would at times with so much against it - big draggy fins, huge nose fins and a sub calibre CP/CG relationship. Not to mention all that nose weight :)

Step 2 now is to refly it and make sure that the broken fin is ok for flight and then start Mk2 which will be a two stager. Upgrades for the Mk2 will be basswood or ply rear fins - probably basswood with a thicker card covering rather than paper to try and improve the strength. I am considering cutting a ridge into the fins and bonding in a bamboo skewer to make the fins a bit more rigid. Bit of experimenting to do to see what gives best weight vs strength.

As soon as I can get some time I will do a better video, hopefully with more flight pics. The vids for that launch were done by my partners brother and he was were a bit surprised how fast she got off the pad hence the wobbly pics.
 
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Wunderbar!

For a rocket such as this, with those long fins and given how much effort went into it, I'd be inclined to invest in a good quality nylon parachute rather than rely on a bin bag. Flying it in minimal wind is also a good idea because regardless of how gently the parachute brings the rocket down vertically, if the wind is taking it 10mph horizontally then it will probably break a fin when it hits the ground. I believe that is what damaged the fin of my Feuerlilie F55 during its flight last year - it had a bigger parachute than I'd ever used before but there was some wind, so the rocket was going at a fair old clip horizontally at touchdown.

As regards nose weight, I reckon you got it spot on. Any less and it would most likely have been unstable, or worse yet, marginally stable. The D12 evidently has enough power to lift that weight, so it's better to err on the side of caution and make sure it goes straight up.

Well done!
 
Adrian, it was your Rheinbote that inspired me go build this one :)

I wish I could get a Nylon chute in there but one of the design hiccups was a not very big recovery bay and I doubt, based on the Nylon chute I have thats sized about right for the SLS Hustler, and so about the right dimensions for RT, it would fit in the somewhat bijou recovery bay hence the need to resort to bin bag types. Thats something that will be improved in a later build.

I am not worried too much about a crash now that I know the basic design works. It will get flown a few more times for video footage and then it will most likely be scrapped. Its fins may be used for the Mk2 version which will have slightly alteretd dimensions, tougher fins and two stages.

I dont really have storage space for too many rockets so I dont worry too much if a few get toasted. Truth to tell I enjoy building them more than I enjoy flying them. Flying them is fun but I get a real kick out of making them.

Thanks to everyone for the nice comments.
 
Donner Und Blitzen !!!!

Today the Rheintochter got its second outing and disaster struck !!!!!! I just posted in the Fire Lily thread but thought I should post here too in case anyone is thinking of building from my designs.....

First flight today was a charm, she flew straight up and recovered fine although she did tangle her shroud lines initially. 2nd flight was a disaster - she left the pad and almost immediately veered away - rather like a missile homing in on its target - she flew in a long arc back towards the ground and came in ballistic and then ejected the chute at more or less the same time as she flew into a tree. The rocket was completely destroyed by the impact - we found a few fins under the tree which were all mashed up very badly - one of them looked like somone had taken a huge bite about 2" wide out of its leading edge indicating a very violent impact speed as this was across the grain of the fin.

We couldnt get the rocket body back as it was in the upper branches of some kind of thorn tree (probably of the rocketus eatingmus variety) that was impossible to climb but judging from the fragments scattered around there wouldnt have been much to recover.

I now dont know wheteher she suffered some kind of structural/motor problem such as;

  • Fin flutter leading to a failure
  • Nose cone twisting due to its canard fins causing some kind of steering problem - this is possible
  • Flakey motor causing erratic burn

Or whether there is some kind of basic instability in the design. It seems weird that on both pairs of flights the first flight was perfect while the second flight showed a wildly erratic behaviour. On the first pair of launches I put this down to a fin issue caused by a hard landing on the very first flight but now I am wondering if she is basically unstable or marginally unstable leading to weird and erratic behaviour.

I am now planning the mark II which will be a two stager and will incorporate some changes to try and prevent this happening again - primarily;

  • Longer nose tube to make more space for recovery gear and reduce nose weight - the Mk1 had almost no space for the chute.
  • 'Keyed' nose cone to stop it twisting
  • Possibly free moving canards on small axles
  • More rigid fins - probably basswood
  • Box type tail structure as per the archive footage of the real thing to increas lateral stability and reduce fin flex

I am quite philisophical about the loss, it was a lot of work to build and obviously its a pain but it does free up space to allow the Mk2 version to be built after I do the Natter project.

The Rhine Maiden is dead - long live the Rhine Maiden Mk 2 (coming soon !!)
 
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Sorry to hear about the fate of Rheintochter Eins.

If marginal stability is a suspected cause of the failure then I would not recommend reducing the nose weight. The longer body tube will mean that the same amount of nose weight will be more effective. And that's before you take into account the added tail weight of the booster motor(s).

A twisting nose cone is unlikely to make the rocket unstable. But if the nose cone is too loose then, as thrust burns out and the rocket starts to decelerate, the nose cone will want to keep going and may move forward slightly, allowing it to sit at an angle in the body. That would destabilise the rocket.

A dodgy motor is also a possibility, and it would be interesting to see the nozzle if the body and motor could be recovered. My A4 had one similarly erratic flight due to a dodgy nozzle which produced an angled thrust. Fortunately there are no trees where we fly and the ground is very soft. (Actually there is one tree, it's a long way out and nobody has managed to hit it yet. :))

More rigid fins reinforced by the slab side fins will help stability - perhaps the Germans had the same problem and that was their solution...

Good luck with Rheintochter Zwei!
 
Adrian - the reason for me thinking of the twisting nose cone was the canards. Film footage of the second launch on its first outing (the one where it went erratic but we got it back) seems to suggest the canards were turned round shortly after take off. ie they were square to the main fins at the start but shifted round in flight. Its hard to say for sure because the film is a bit blurred and the rocket is quite tiny in the frame plus its being observed from an odd angle. It did make me wonder of the canard nosecone was twisting like a propeller and perhaps hit an angle where it was causing the rocket to 'steer' from the canards. A less than perfect alignment on nose fins may have been the cause.

Or it might have been that the successful launches just happened to have the nose canards aligned to a position which suited well while the two bad flights had the canards in a slightly different position. Thats why Mk2 will have a keyed nose cone to eliminate that possibility. I just wish I had thought that before the second pair of launches.

The real pain is that we have no hope of recovering the rocket for examination - we would need some serious protective gear to get up in that tree - it was like trying to climb razor wire :)

Its all in the game we play I guess - losses are inevitable. I'd be lying if I said losing that one didn't make me wince at the time but hey ho its freed up some space for other builds :)

Oh the dodgy motor hypothesis - Fire Lily had two flights using the same batch and on examination of one of them there was a great amount of what looked like unburnt powder on one side of the motor - like a sludge inside of about half the thickness of the interior of the casing. Fire Lily was none the less very stable on both flights and showed no real nastiness at all.
 
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Astro-Baby said:
Adrian - the reason for me thinking of the twisting nose cone was the canards. Film footage of the second launch on its first outing (the one where it went erratic but we got it back) seems to suggest the canards were turned round shortly after take off. ie they were square to the main fins at the start but shifted round in flight. Its hard to say for sure because the film is a bit blurred and the rocket is quite tiny in the frame plus its being observed from an odd angle. It did make me wonder of the canard nosecone was twisting like a propeller and perhaps hit an angle where it was causing the rocket to 'steer' from the canards. A less than perfect alignment on nose fins may have been the cause.
Click to expand...
It shouldn't matter if the canards weren't in line with the aft fins. (They couldn't all be in line with the middle fins because there were four canards and six middle fins. ;)) If anything, it should have been more stable if they were out of line because then turbulence caused by the canards wouldn't affect the fins behind, though even that effect should be minor.

Assuming that the nose cone did twist during flight, something must have caused it. If it was a misaligned canard then it must have been seriously misaligned to produce enough force to twist the nose, in which case the twisting nose is merely a symptom, not a cause; that level of misalignment would destabilise the rocket regardless of whether the nose cone was keyed to prevent twisting. But if the nose cone was loose enough that it could be easily twisted, it would probably also be loose enough to come partially out of the body tube under inertia when the thrust burned out, which would then also likely put it at an angle to the airflow, and that would certainly destabilise the rocket. I wonder if it is possible for the body to have expanded slightly after the ejection of the first flight, making it easier for the nose to move?

Out of interest, what batch number were those D12's?
 
I will get a batch number tomorrow for you.....

The heat expansion thing might have legs - after launch No1 the rocket felt abnormally hot (at least compared to other rockets I have) - especially around its mid section - at the time I was a bit surprised as the ejection charge would have been through the centre tube and the midsection was made up of 2 or three tubes with air gaps. At the time I noticed it but paid it no attention. After the crash I did wonder for a time if the heat may have caused some kind of weakness in the glue but I find that hard to believe.
I have a chair made using the same glue (TiteBond II) and thats been out in blazing heat before with no problems.

BUT - now you mention it I do wonder if there was some kind of expansion issue - your loose nosecone theory may indeed be a cause. Given its canards if it were dislodged in anyway it would have very bad effects.
I will take a look at the pad camera and see if it was still brining at high power when the rocket went wildly off course.

A heat issue may well explain why flight No1 was OK and flight number 2 was erratic - on both occasions. Perhaps the broken fin was caused by the landing on the first trial and not as I previously thought a weakened fin breaking up. Tougher and more rigid fins I think will help cancel that out on Mk2.

My bet is there was some kind of structural failure caused by the rear fins failing - this was evident after its first trial launches but I was reasonably sure that the failure was caused by a hard landing that weakened the fin. It may well be your original ideas about fin flutter were on target and the long rear fins just cant take the stresses.

A lot of this I am only going to find out by doing it all over again - joy :)

I may build the next one at a slightly smaller scale to improve power to weight.
 
From what you say, at two separate flying sessions Rheintochter flew perfectly first time and then went nuts on the second flight. This implies something that changed after the first flight, messed up the second flight, and was then reset in time for the next flying session. This is one reason why I suspect the loosening of the nose cone. (That plus your analysis of the video indicating that the nose cone had moved, which shouldn't be possible unless it was fairly loose, otherwise any twisting force caused by a misaligned canard would have caused the whole rocket to twist.)

The idea of one of the long fins being weakened by the first flight and causing the rocket to go off course on the second only works if you then fixed the fin afterwards, making it strong enough for the first flight of the second session, then it (or another fin) weakened again and caused the rocket to go off course again on the final flight. Slabs on the sides of the booster fins will help the booster but won't do anything for the big fins on the sustainer. On the other hand, unless you figure out some way to deploy a parachute from the booster, it's going to come down hard while the sustainer will certainly have a parachute...
 
Astro Baby, I was wishing to maybe build a large scale model of the Rheintochter. Where did you come across your set of scale drawings. Would you be willing to share them with me.

John Boren
 
I haven't seen Astro Baby post in a long time. I'm not sure if she is still active right now, so I'll try and answer for her. I'm pretty sure that Astro Baby made up her drawings based off photos, a book on German secret weapons, and a model she owned. She was aiming at a sport scale model and adjusted tube sizes to match what was available.
 
She used to be active on the Cloudy Nights astronomy forum but I didn’t find her handle in the members list.

Possible that she used a different userid over there...been so long that I don’t recall her handle. I do remember her account of carrying her large telescope up and down the stairs from her flat.
 
Uncle Scary said:
I haven't seen Astro Baby post in a long time. I'm not sure if she is still active right now, so I'll try and answer for her. I'm pretty sure that Astro Baby made up her drawings based off photos, a book on German secret weapons, and a model she owned. She was aiming at a sport scale model and adjusted tube sizes to match what was available.
Click to expand...

John I own a copy of the German secret weapons book. It has a drawing labeled as1/48 scale but with no dimensions. I'll be glad to scan it for you. Just let me know how to get it to you.
 

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