90% RUHRSTAHL KRAMER X4 (1944-1945)

[Zeus-cat]

I used to play a flight sim that had this weapon as one of the loadouts for German interceptors. It was really hard to hit B-17s with this thing. You fired it from a long way off to stay out of machine gun range of the B-17s and guided it in with a joystick. I believe it had a flare in the tail for visual reference to help you guide it to a bomber. Every once in a while you would hit a plane with one, but cannons made more sense to me, even if you had to get dangerously close to the bombers to use them.

 

[t-rocket]

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[video=youtube;jX2Cd5iTs3I]https://www.youtube.com/watch?v=jX2Cd5iTs3I[/video]

 

[t-rocket]

[video=youtube;7mEAfGe1j24]https://www.youtube.com/watch?v=7mEAfGe1j24&NR=1&feature=endscreen[/video]

 

[legranddudu]

I started the work today:

- cut all parts carefully and adjust bodys and tail cones/nose cones
- adapt the front NC with inside tube and centering rings. Will host the trimm weight and possibly one Avbay, not sure yet
- clean up all parts
- cut a BIG carbon centering ring (3mm!) and a small one for the MM
- laminate a very light cardboard MM with glass sock (not in display)
- spent time wondering where I will place the Avbay, 2 possibilities: in the front NC or in a special plate mounted on the carbon ring. The Ring edge is the critical limit for anything that weights...everything behind this limit in the aft will need to be compensated with lead in the front NC...
- spent time wondering what kind of wing I will build: eventually wood, foam and carbon fabric with a carbon square holm/spar

 

[legranddudu]

some additional pics of today



Next step:
- do first set of wings as a test with different sandwiches
- cut the aft airframe

 

[legranddudu]

OK, not sure if someone follows this thread but I keep posting...

Today:
- I cut the wings out of 12mm plywood (light one) & beveled the edges
- cut tailcone for the wings to fit in place and TTW
- test fit with lot of tape..

 

[legranddudu]

Next I did put the front airframe in place and I cut the 2 wing pods to fit in position as in the original bird..

 

[Eat, sleep, and Fly]

OK, not sure if someone follows this thread but I keep posting...

Today:
- I cut the wings out of 12mm plywood (light one) & beveled the edges
- cut tailcone for the wings
- test fit with lot of tape..

View attachment 126351View attachment 126352View attachment 126353View attachment 126354

I have been pretty quiet, but I am following this! It looks to be one of the most insane projects that I have ever seen, It will be interesting!!! good luck!!!!!!

 

[pepe]

Following with great interest,good luck

 

[legranddudu]

attached the rocksim file of the KRAMER X4, with proline 7.5" components.
View attachment kramer X4 final.rkt

 

[nh4clo4]

OK, not sure if someone follows this thread but I keep posting...

Of course we do....

 

[Leo]

OK, not sure if someone follows this thread but I keep posting...

You bet we do!

 

[Getmore]

Yep this is one cool project. Some times it looks like people don't look or care but we do look and care. Love your build.

Bill

 

[beezwax]

I've followed all of your builds with great interest but this one really takes it to another level. I can't wait for a flight report, good luck!

 

[Cl(VII)]

Absolutely following. You're V2 build was a masters level class, this looks like it will be Doctoral Level...I watch as an amazed elementary schooler.

 

[bill2654]

With this thread getting over 1000 views, I'd say people are watching! I love ALL your builds.

 

[MasonH]

This is turning out WAY cool.

 

[legranddudu]

this step was a lot of work... focusing on fins and centering rings/ alignement rings..

Well 2 things on the rings: they shall center the fins but also align them. Gaining time and lot of energy... so i cut a square portion of wood on fins & ring so they can fit in each other..and get automatically aligned..

 

[legranddudu]

Next one today was to gain lot of weight on the fins..or better say wings.. at the beginning they weighted 400gr each (0.88lbs)..simply not acceptable in the rocket geometry... so I started making holes.. finally it went from 400gr down to 210gr each (0.46lbs).. I think this is OK nearly 48% saving..that shall help my CG...next step tomorrow: cut foam to fill the holes, start preparation for the vacuum phase.... a couple of hours cuting fabrics and carbon in front of me I know... good night Boston, sleep well and now safe...

 

[Daddyisabar]

Power and nose weight rule! If it wants to wobble or spin a bit on the way up think of it as more scale like flight.

 

[legranddudu]

some progress:

- fill the wings with foam, now ready to be glassed with FG and CF layers
- made a foam form of the aft fins, following scale and the lines of the airframe, to be glassed later on
- prepared one of the 4 fins with a wood kernel to give some strengh where I place the aft rail button

 

[legranddudu]

eventually I did not really liked that wooden plate so I decided to realize all fins with foam, glassed with CF. I believe this will look much greater as the wooden plate, will be lighter and much more scale, looking like the ortiginal, with more Drag. Lighter and more drag, this is good for my stability overall!!

Please note I tape sanding paper with double side tape to get the perfect concave shape of the fin to glue on the airframe....
Here the last pictures:

 

[legranddudu]

more pics from this step and finally going into the vacuum bag for 10 hours...

 

[Getmore]

Man you have one sweet shop to work out of.

 

[legranddudu]

OK this morning the fins were ready. Cut edges and clean it from curing. They are very robust and strong...and incredibly light: 60% lighter than wood..in total approx 70gr for all 4 fins instead of 172gr...this is nearly a saving of twice that amount of lead in the front (according to the different distance to the CG)...on the other end the new fins are 3x wider than wood, meaning 3x more drag..so my CP goes back and my CG forward..I just win a nice piece of stability that I do not need to gain with lead..and less lead means more performance on the flight, or less need for power, possibly cheaper to fly...

 

[legranddudu]

next I had to prepare each fin to fit to the airframe, which is at the end of the inverted NC a very round shape that change quickly in the length. Again, double-tape some sanding paper and gently sand the bottom face of the new carbon fins...perfect fit now!

 

[legranddudu]

Next was just for fun..or for the pleasure of the builder... just double tape each fin temporary to get a first impression how it looks compare to the original...I would say, not too bad what do you think?

 

[qquake2k]

It's looking great!

 

[Cl(VII)]

They look great, and you saved 300 g. Very nice.

 

[nh4clo4]

Outstanding build.