Rheintochter / Rhine Maiden

[adrian]

Excellent work!

Take another look at the thread about the Martel, in which the builder has made a template with a circular hole and slots for the fins. Perhaps something similar would help here, especially for the six sustainer fins?

In the photos of the real thing can be seen fillets on the fins. These are strips of metal to which the fins were bolted. Are you planning to depict these? It occurs to me that if you put those on first, they might help when you attach the fins.

I'd be inclined to put the CA onto the fins before they go onto the body. That way, if anything goes wrong, you've lost a fin but you don't have to rip it off the body. It also means you don't run the risk of CA dribbling onto the body. (I know from personal experience that thin CA likes to run anywhere it can, not always where I want it to go!)

 

[Astro-Baby]

Hi Adrian,

I tried the hole cut out idea before on Bloodhound and Perseus but found it didnt work well for me, getting the template accurate enough became a challenge in itself that turned out to be beyond me.

I am going to do the fillets along with the semi body mouldings but I thought putting those on first may bring its own headaches so decided to add them later on. In part thats also to keep the weight under control. I want to see what the weight looks like with its fins on before making a final decision on the fillets and body mouldings. Its already quite a heavy bird with all that tubing for its size.

Fin number 2 of the sustainer is going on now on the opposite side to the first fin. I picked opposite sides as these will be the pair that line up with the booster fins so I wanted them as accurate as possible and it was easier to get this right while they are the only fins attached.

Much work still to do and finning the bird will take at least 10 days of time. While thats in progress I have work to do on the nose cone.

 

[Astro-Baby]

Time for an update....

I got the first two fins on the front body. I decided to do these first as the rear fins are longer and would need a different jig.

The firts two fins were the opposed fins - ie ones on identical opposite sides. These would be the ones that line up with the rear fins. Rheintochter having six fins at the front and only four at the rear means only two forward fins align with the rear (more on that later). So two fins were added that were quite level with each other through the use of a piece of balsa cut straight and then having a section cut out for the body allowing the 2nd fin being added to be totally level with the first.

Next up was to complete half the forward fins - only half ? - Yup because I wanted half a bird to check out how it was going and also to allow a good alignment of the rear fins. Again - more on that later.

The fins between the first two forward fins are set at 60' separation around the bird so I made up a balsa template to make sure alignment was good. Add in some curry paste bottles and some plastic rulers and hey presto one fin jig.

heres a pic of one of the fins being added.......

 

[Astro-Baby]

With four of the forward fins added - so half of the birds forward end (i know there are six fins but from a flat schematic point of view you can only ever see four at any one time). It was time to add the two rear fins that have alignment with the forward fins.

There is a method in this madness. With so many fins at different angles I wanted to make sure that each of the non-aligning rear fins look right with the front end. Technically it should all be perfect using set squares etc but I am never THAT precise (I try very hard but it seldom works out like that ). So to offset any small errors I wanted forward fins that align with the rear to be perfect, the 60' angled ones between them set up and then the offset rear fins so I could gauge if things looked ok looking down the bird. This sounds complicated but its easily done in fact.

Anyway with four forward fins added it was time to glue on the first of the rear fins. Done using a steel rule pegged to the forward and rear fin to ensure alignment between the two.

 

[Astro-Baby]

And once that was done rear fin No 2 gets glued on. The jig for this included a cardboard box with a slot cut out to allow the first of the rear fins to poke through and give the body enough height so no weight is put on the first of the rear fins. This is a real pain of a bird for the fins as they are so long.

The nose of the bird was supported on another jar of curry with a pair of tins propped against the downward facing forward fin to stop the bird turning in the jig.

 

[Astro-Baby]

And finally Fin 3 at the rear end gets added. This makes it a bit clearer perhaps why this order. Its easy to judge whether Fin 3 which sits BETWEEN two of the forward fins is looking ok - ie centred. In fact it needed a bit of jiggery pokery to get the fin to align well with the rear fins at 90' AND get it looking spot on between the forward fins - it does however raise an issue........

Heres fin 3 being added with some more 10c jig work plus a picture of the bird in its state after adding this one in a kind of plan form to give an idea of its overall appearance.

 

[Astro-Baby]

So what is this issue that I keep mentioning ?????

Well after half the bird was done I looked down the end and it became apparent something didnt look right. Looking down the nose the fins at front and rear alternate in angles. Some show a 30' separation and others a 60' separation caused by the effect of one lot of fins being 60' apart and the other lot being 90' apart.

So I went back and looked at reference pictures and realised a horrible assumption had been made. By me, the guy at Fitters and as far as I can tell by some museums (though its hard to say from some pics). I said a while back that one of the reference pics looked as though the rear fins are not at 90' but are set at a different angle. Its obvious now they are or else the bird would not fit on the launchers its shown with in WW2 footage. The rear fins in fact are set at 120' most likely.

I have knocked up a schematic to show this in the pic below.

The assumed layout is how my Rheintochter was designed but I suspect its wrong and that the real layout looks more like the one marked possible actual layout in the pic. Looking over the huge pile of reference pics I am almost sure that the possible layout I have marked up is how it looks in real life, possibly the angles are different again - its very hard to tell from most pics as they are shot with a wide angle which tends to distort. If you look at the most common pic of the bird on its launcher you can see that the assumed layout couldnt work - there would be nowhere for one of the rear fins to sit.

 

[Astro-Baby]

Arrrrggghh - so a dud assumption had been made - what I would call 'The Assumption of Mediocrity' looking at stuff and being so sure its obvious that you dont look further and ask the 'what if ?' questions. Actually I did - earlier in the build thread but put the thought aside

So what I am going to do - I could cut the 3rd rear fin off and do some more research. Its an option - but not one I will do. I may be making a mistake but I slept on it and decided that this whole thing is an experiment anyway. Who knows what the real thing looked like or worked like. There are so many conflicting descriptions its very hard to know for sure whats right so unless anyone happens to have the Rheinmetall original drawings its nigh on impossible to be sure about much.

With all that said I decided 'damn the torpedoes - full steam ahead' and carried on as planned -

Heres one of the remaining forward fins being added using another Heath Robinson jig employing some Ikea condiment dispensers and I have to say its the first time they have ever been of use as they are useless for the purpose thay are designed for (no indication of which one has salt in the design, they wouldnt grind snot, the slightest bit of resistance from a pepper grain causes the pepper grinder to fail and jam - ditto the salt one)

 

[Daddyisabar]

Yoda says "UMMMMM, Piercing the veil of darkness surrounding the Rheintochter you are."

With all the goodies and kitchen utensils acting as jigs the build is looking very delicious.

A while back I suggested to a contest team we build a two stage Rheintochter, but the guys thought it would be "too hard" and not enough solid scale data existed to win a contest. Consequently we just built a WAC Bumper.

 

[rbeard2]

I've had this one on my radar for a while too . . .how about foam core board for the rear and middle fins with balsa strips for the leading and trailing edges? A solid balsa or even turned hardwood dowel nosecone with birch ply canards? Or even omit the nose canards altogether - as stated above, there is a LOT of design variation apparent in this one so why not take advantage of that fact and make the model more stable? My approach (albeit on paper so far) has a slant towards lightening the ass-end of the thing as much as possible because with that much fin area, the CP is already pretty far aft (especially if you omit the canards). I'm thinking a BT-80 for the main tubes and a 24mm long mount for a nice long-burn E9. Maybe this year it will become more than a stack of designs, thumb-tacked to the cork board!:flyingpig:

 

[Astro-Baby]

A hard week of adding fins to the bird has resulted in the attached pictures. All of the main body fins are attached and aligned and the bird is now awaiting its canards and various body styling upgrades.

A few shots from different angles. Its uncanny how in at some angles the rear fins look smaller to the eye even though they are at least 30% bigger than the forward fins.

 

[Astro-Baby]

Finally a few pics of the canards being attached to the nose cone.

These turned out to be easier than I had imagined. The shape of them is disputable as every Rheintochter seems to have slightly different shaped ones;
Some have the leading edge turned in as it meets the nose cone, some seem to have quite complex curve at the tip while others have a simple circular tip, some have a relatively flat angle on the leading edge relative to the horizontal and some have a more aggressive angling so its hard to know what was for real on the real thing - maybe all of them or none of them.

I decided to go for the simplest design of these. The real thing has these on a shaft which I assume would be hitched to a servo for radio control. Obviously nothing so fancy for this one. I had originally toyed with the idea of having them on a dowel that ran into the nose cone below the layers of filler but an attempt at that this morning with a scrap cone showed it to be be very fiddly and not to have a good enough join to stand the shocks of model rockets.

In my original thinking I did think of drilling a hole right through, putting in a thin plastic tube and having a rod put through which would allow the canards to move. In reality it was way too complicated and beyond the resources of my meager facilities or skill.

This evening I tested another idea which was simpler and worked well which was to take a needle file and grind a slot into the nose which the canard simply drops into with some glue - this also saves the headache of sanding the caanards root to get a good match to the ogive shape of the nose. Its straightforward and very strong. The real bird has each opposing pair set slightly higher/lower but for this I am going to have them all at the same height round the nose.

The nose cone has been on the whole the hardest thing to get right and I am still not wowed with it but its as good as I can get it. In the earlier over enthusiastic reshaping of it the part that fits in the rocket tube got sanded too much and I hate the idea of loads of masking tape so I have sanded it down even more so it will fit into a BT60 coupler. The coupler will eventually be glued inside the nose of the rocket allowing for a good fit between nose and rocket without resorting to masking tape (maybe).

Overall she is looking good - better than I had dared hope at the start of the project though still a long way short of what some folk can do - she needs a lot of finishing though and she is still at least two to three weeks away from her first paint job.

ps in the background you can see a 1/3 scale (from my rocket) cut out of the bird. This was drawn up and printed onto a heavy card and then cut round to assess the CP. I done some reading and decided calculating the CP by math was going to be waaaaay over my head so went for the modeal approach. Assuming the CP is correct from that the current CG would be about right so she may not need any additional nose weight.:surprised:

 

[Astro-Baby]

Finally for now..... you will see on earlier posts when the tubes were under construction I was putting in dimensioning data so anyone could copy this - if by the end of the thread anyone wants the fin templates I will post them up as PDFs for anyone to use together with the cones and transition templates.

I cant do the nose because how I got there is a bit of a mystery even to me

 

[adrian]

Good work so far!

It's a good job you didn't "correct" the booster fins to match your "Possible actual layout" because that's wrong too. Having been close to a real Rheintochter (that photo I posted wasn't looted from the Internet!) I can tell you that, at least on the one in Berlin Technische Museum, the booster fins are 90 degrees apart, though set so that if you look head on they form an X; and that you'd need to turn that diagram 90 degrees to get the sustainer fins right because two are horizontal, not vertical. Your "Assumed layout" at least has the right fin spacing and if you rotate it 30 degrees anti-clockwise it looks more accurate than the "Possible actual layout". You're going to have to put the launch lug(s) somewhere between the fins so once the model is on the pad, it will look fine.

As for the nose fins, there's a detail which you could easily add if you wish. There's a small piece of metal each side of the fin, presumably reinforcement for where the shaft enters the wooden fin; a little piece of paper either side of the model fin would depict that nicely.

I'd say that the model so far looks accurate enough that nobody will notice the difference unless you tell them! Keep up the good work...

 

[Astro-Baby]

Yup Adrian - the small bits of tin on the front fins are where the servo axle goes and its fitted to a kind of paddle which the wooden canards then slot into. I have that yet to do along with the body mouldings between the fins at the rear and the forward fins as well plus the strakes that run along the fins at the root. Weirldy on the pics the lower fins seem to have a simple band with the strakes on it whereas the upper fins seem to slot into what looks like a machined up piece of metal. As its quite a sizable fitting I am amazed they machined it rather than just welding some angle iron on.

A ton still to do on this and I staill cant make up my mind about paint which means its going to be plain green so far.

 

[adrian]

Weirldy on the pics the lower fins seem to have a simple band with the strakes on it whereas the upper fins seem to slot into what looks like a machined up piece of metal. As its quite a sizable fitting I am amazed they machined it rather than just welding some angle iron on.

Take a look at these:



The booster fin attachments do indeed seem to be a separate band whereas the sustainer fin attachments seem to be integral to at least the bottom of the sustainer body. Thinks: Rheinbote's first stage was the same unit as Rheintochter's, but with different fins. They didn't share common further stages, though. So Rheintochter's sustainer could be made specifically for Rheintochter. Perhaps the first stages were just made without fins, to be used as needed for either rocket, and fin attachments were added as needed?

 

[Astro-Baby]

Damn ! I have to go back to Berlin to see that Museum - I was there a year or so ago but we ran out of time thanks to other half falling over due to not looking where going and breaking arm. The dangers of texting while you walk for all to see. I laughed so hard I was the one needing oxygen

Adrian - could be on the base - while reading and pic hunting today I found a rough looking pic of a real launch where you could see staging which I haven't come across before. Your upper stage pic above tells me the wasp waist on this one is too long. Its ok - plenty of time to make another one as a two stager after I see if this one flys ok.

 

[adrian]

Damn ! I have to go back to Berlin to see that Museum - I was there a year or so ago but we ran out of time thanks to other half falling over due to not looking where going and breaking arm.

If you are ever back in Berlin, definitely go to the Technische Museum. Rheintochter isn't the only thing on display which would interest you!

Adrian - could be on the base - while reading and pic hunting today I found a rough looking pic of a real launch where you could see staging which I haven't come across before. Your upper stage pic above tells me the wasp waist on this one is too long. Its ok - plenty of time to make another one as a two stager after I see if this one flys ok.

The wasp waist may be slightly too long; the piece of body tube above it is definitely too short. On the above photo of the sustainer body, the straight body tube ahead of the fin attachment band is almost twice as long as that band, and that does not include the section represented on your model by the transition.

If you look carefully at the photos of the booster and sustainer, you can see the fins on racks in the background. The booster fins are entirely wooden with a piece of metal on each side of the root where they fit into the slots on the booster itself. The sustainer fins have the metal extending up the whole side, with only the leading edge exposed. The photo of the fully assembled missile shows a different structure, mostly entirely metal with a wooden leading edge. I don't know which version came first but I can guess why metal was preferred for these fins. Long, thin fins like this will flutter. This may be why some boosters had the slab fins. The sustainer fins did not, and the sustainer would end up going faster than the booster, so plain wooden fins would probably not survive. For the same reason, I would not trust the foam board fins suggested by rbeard2, even with wooden edges. Your laminated and CA-reinforced wooden fins have a much better chance of survival!

 

[Astro-Baby]

Here's a few more pics of the canards including one where the sloit I filed out for the last fin is on show.

The cone now needs filling, detailing and and general finishing.

 

[Astro-Baby]

And now - deh-duh !!! Roll of drums - here she is with all the major construction completed. Now needs fin gussets, the upper stage nozzles and a lot of sanding, filling and general messing about with. The targets eye view shows the fins front end on with a just a bit of 'off' so they show up better. Alignment has been amazingly good for this one.

The scale is not quite right but this one was built as a test and when I do the next one there will be a lot of mods and improvements to get it a bit more bang on.

 

[Daddyisabar]

NICE!

 

[Cookie the Dog's Owner]

Ye Gods, is that one magnificent piece of scratchbuilding!

 

[thobin]

I like.



TA

Sent from my GT-N5110 using Rocketry Forum mobile app

 

[adrian]

And now - deh-duh !!! Roll of drums - here she is with all the major construction completed.

There were probably times during the construction when you thought "What's it all for? Is it really worthwhile?" Now is when you get to take a look at the result and say "Yes!" If you don't, then I'll do it for you - YES! And if you think it looks good now, wait till it has a coat of paint...

One thing which does concern me - where is the CG when a motor is installed? I can't guess exactly where the CP will be, but I would guess that if the CG isn't at least as far forward as the sustainer main fins then the first flight will be "interesting".

 

[75Grandville]

I must say that I am in awe! I was in line at a club launch yesterday, and one member started talking to another about this thread. Naturally I had to come find it.

All I can say is WOW. Just WOW.

There is one at the Smithsonian Air & Space Museum about 20 minutes from where I live. I've looked at it, taken pictures, and dreamed about making one of these. I now have a fairly good idea of where my skills will need to be to make something like this, and I can say that I'm just not there yet. Which means I need to spend lots more time building rockets to improve my skills. Hmmm. Sounds like a win to me!

Seriously, thanks for sharing your build with us.

 

[Astro-Baby]

Ahem....thanks guys, you will embarrass me horribly with this praise. Its an accomplishment as yet unaccomplished though lots still to do and endless things to worry about.

I have some more pics to upload soon as all of the main work is now completed.

I will do an update hopefully tomorrow.

Adrian..to answer your CP/ CG question. My best guess at the CP based on a bit of science but a lot of guesstimation is that the CP will be slightly forward of the narrow part of the wasp waist. With a motor loaded and Rhine Daughter in its launch configuration (less paint) the CG is just aft of the trailing edge of the sustainer fins and around 1 " forward of the CP.

Thats too close for comfort in my mind but I have an issue.......with the motor onboard the bird is getting close to 250gm in weight which means its starting to get close to what a D12 can lift...at least based on engine data.
Now my SLS Hustler is around 325 grams and can be launched on a D12 but she doesn't make much height, with all the drag that RT will have plus those ludicrous canards I was hoping for a lighter bird and higher thrust to weight.

To minimise any additional weight I have to get is as far forward and as condensed as possible. So its starting to look as if lead shot in the nose cone may be the way to go. An alternate solution is to lengthen the forward part of the rocket and thereby decrease the weight needed as a longer rocket will need less weight forward. Questions with that are; Does the extension piece add more weight than it saves and, how viable is it as an idea, its means a lot of reworking and. I am loathe to start a radical rebuild because it seems a big risk and lots of headaches.

I am going to sleep on it and ponder as both solutions have their downsides.

On the whole I am happy with the build, some stuff could have been done better and the scaling is horribly wrong in places. But a lot of that was expected. mk 2 will be done better using lessons from this one.

Its first launch will have a full film crew to capture the moment of triumph or the moment when disaster overtakes the project

By the way, she hasn't been as hard to build as I had expected and lots of stuff has gone really well......i would say construction has not been harder than many of the more fiddly kits.

 

[Daddyisabar]

In the end power and nose weight are your only friends. The mighty D12 is just too heavy and inefficient. Time to hop across the pond and get some composite motors from the North American Colonies, or maybe there is a bunker outside Berlin that still has some Tonka 250.

 

[legranddudu]

very very impressive...I discovered the thread today. I am completely fascinated by your work. The Rheintochter is on the top of my projects for 2016 but in 8'. I want to run it 2 stage, full hybrid with a cluster, nearly as the real thing. First I will build a test rocket in 5.5'. At the moment an another large project absorbes my attention, so for the moment the best I can do is to subscribe this thread and enjoy every steps you publish here, a real delight...
Regards from Munich
Denis

 

[adrian]

Adrian..to answer your CP/ CG question. My best guess at the CP based on a bit of science but a lot of guesstimation is that the CP will be slightly forward of the narrow part of the wasp waist. With a motor loaded and Rhine Daughter in its launch configuration (less paint) the CG is just aft of the trailing edge of the sustainer fins and around 1 " forward of the CP.

You'd need to feed all the measurements into your choice of Rocksim, Open Rocket or VCP and see where the CP shows up. Personal experience with winged rockets says the CG generally needs to be about level with the leading edge of the wings, at least, for the rocket to be stable.

Thats too close for comfort in my mind but I have an issue.......with the motor onboard the bird is getting close to 250gm in weight which means its starting to get close to what a D12 can lift...at least based on engine data.

Estes' data says the D12-3 should be able to lift 396g. That's a 3:1 thrust/weight ratio, which I've accepted on some of my scale models as well, and which allows for a safe though low flight as long as there's not much wind. You certainly won't want a D12 with a longer delay!

To minimise any additional weight I have to get is as far fowarda nd as condensed as possible. So its starting to look as if lead shot in the nose cone may be the way to go. An alternate solution is to lengthen the forward part of the rocket and thereby decrease the weight needed as a longer rocket will need less weight forward. Questions with that are; Does the extension piece add more weight than it saves and, how viable is it as an idea, its means a lot of reworking and. I am loathe to start a radical rebuild because it seems a big risk and lots of headaches.

Lengthening the rocket is a good way of moving the CG forward, and the mass of the extra body tube should not have much effect compared to the movement of the weighted nose. And I have already suggested that a longer forward body tube would also make the model more accurate. You'd need to cut the tube somewhere aft of the nose transition, make two couplers to stick into a short piece of tube which will become the extension, then glue the whole lot back together. It's slightly complicated by the fact that, as I recall, the model has an inner tube which would need to be extended the same way, but should still be viable. You can make a coupler by cutting a short piece of body tube, slitting it lengthwise and rolling it in on itself so that it just fits into a piece of the same tube. But you're probably going to need the lead in the nose as well - the longer body tube just means you won't need as much of it.

On the whole I am happy with the build, some stuff could have beend one better and the scaling is horribly weong in places. But a lot of that was expected. mk 2 will be done better using lessons from this one.

It's a good idea to build a rough version first just to see if you can get something like this to fly. If it works, then put more effort into a more accurate version. I've done something similar with Seaslug - the crude test version has already flown successfully, the accurate version with detaching boosters may actually be completed one day.

I'm looking forward to seeing the launch pictures and video. After all your hard work, I really want the rocket to go straight up!

 

[Astro-Baby]

very very impressive...I discovered the thread today. I am completely fascinated by your work. The Rheintochter is on the top of my projects for 2016 but in 8'. I want to run it 2 stage, full hybrid with a cluster, nearly as the real thing. First I will build a test rocket in 5.5'. At the moment an another large project absorbes my attention, so for the moment the best I can do is to subscribe this thread and enjoy every steps you publish here, a real delight...
Regards from Munich
Denis

I would LOVE :sigh::sigh: to build a bigger version with a seven motor first stage (kind of like the real thing) and obviously with a two stage design. As noted at the start of the build thread though, for me its impossible. I did some rough drawings at the start and to get a 7 motor booster even using small 18mm motors ended up with a bird with a wingspan so large it would have been impossible to transport plus my partner would probably kick me out of home if they thought they were going to have a monster missile sat in the corner of the flat. I only live in a tiny flat you see with little storage. Space is so tight that losing a rocket is almost a mercy as it frees up space to build another one. Rheintochter will be the last build for me until something else blows up or is lost so I have space.

A two stager would be the next build probably - I might build a smallish Fire Lily first though to use up some scrap bits left over from Rheintochter. Lord - so much to build and so little time (and storage space) - theres Scmetterling, Enzian, Sea Dart, Talos - every day I come on here more stuff gets added to the list

Adrian - a Seaslug would be fabulous but I can see some real headaches with that - like the boosters incinerating the main tube with those forward boosters. As you know I have been trying to get started on a Sea Dart but stuff just comes along which is more interesting. Interesting motor data you give for the Estes D12 - I made a note that its 286gm - I must have scribbled it down wrong - duh!

I think what Rheintochter has taught me most is that I am probably done with kits - mind you the TLP Talos would probably get my attention if they release it I had imagined a scratch build would be a lot of headaches and for sure there are headaches (and heartaches) on the way but its also a lot more of a challenge and I like that - the brainbox gets a bit hot at times but thats ok and I enjoy the challenge.

The problem with extending this build versions nose length is there are inner tubes to the main bird and getting everything to align afterwards may be tricky. Having slept on it I am going to see just how much weight ends up being needed to balance her. I have to get some lead shot and test this out. If it exceed max lift off weight I will have to try for an extension - I can mock one up using some couplers and spare tube just stuffed into the front of the rocket as it is to get some idea.

Anyway in the meantime here are some more pics showing further construction.

This is the wrap around for the booster with some strakes added. Its not as long as on pics due to a mistake. The holes in the strakes were to simulate the bolt holes on the original but after all the strakes were done I didn't like the look of the holes and filled them in again when the strakes were blended to the wrap around.