"home made" body tube transitions

I have only made one of these critters, for my Centuri finless rocket. I used a light cardboard, made it for a BT70-BT20 transition. I actually ended up soaking it in water to get it to take the tight curvature at the top of the wrap. It turned out good, not perfect.

Now, suppose I want to make a bigger one. I'm imagining some sort of internal structure under the "wrap" to help in holding it's shape and providing some structural integrity. I want to experiment with sheet balsa/basswood, guessing they might hold their external shape a bit better than paper. Or perhaps using wood strips to completely cover the transition, sort of like plank on bulkhead ship modelling.

Have you made any of these? What technique did you use?

Thanks much,
Dave

I've used the balsa-planking tecnique on a few HPR models, most notably the 'Kone of Koncer, which was a 6ft tall K-powered 10/1 ducted conical finless rocket (all balsa) and 'Primary Koncern', a 13" diameter pseudo-Russian ICBM.

See enclosed pic of the Primary Koncern nose mid-construction.

I've found it best to tack the strips in place with cyano, use fairly thick material, and sand it back to round once it's finished. Onviously, the strips need to be slightly tapered... but I just 'winged it' and plugged the gaps where needed.

Hope this helps!


Ben

PS:, sorry, forgot to mention, these were covered with a layer of heavy glass cloth after finishing, but on models, no reason they couldn't just be filled, sealed and sanded back.

mrbus, yes water will soften the cardboard and allow you to make smaller bends but I think when it dries it ends up in worse shape.
I like to use body tube stock whenever possible because I think the finished fairing is stronger and looks a little better. I use the next larger size than the largest diameter in the fairing. I lay out the pattern so the middle of the fairing is straight down one side of the BT stock and the two fairing edges end up a bit cockeyed somewhere else on the BT. I work the small end of the fairing around small dowels or old motor tubes by laying the fairing on a sofa cushion (outside surface is face-down) and burnishing/rolling against the cushion. I work the small end of the fairing with small diameter tools; the larger end of the fairing usually doesn't need much more bending to shape. I glue a strip of scrap BT under one of the fairing edges to be joined and press that tight on a hard flat surface. After that is dry (to avoid fumbling around with loose pieces while trying to glue the other edge) I glue the other edge of the fairing onto the same strip and press that also on a hard flat surface. I sand the edges for proper fit, CA the inside of the entire fairing, and do a little 'finish' sanding on the ends.
If I get a chance when I get home tonight I will look for some old pix to post (I suspect my description might be a bit confusing?)

Poserboard, 1/64 ply, or ultra thin fiberglass (I forget the thickness I had). You can glass the transition, inside or out or eve fill it with 2-part foam if required. This ia an amalgam of various things I have tried/used. Posterboard with just a layer of epoxy on the inside is suprizingly durable. On the larger 12" Art Applewhite saucers, you spread the epoxy on the posterboard and lay on fiberglass dry wall tape.

I agree with rstaff that posterboard is great stuff to work with. It bends SUPER easy. It comes in giant sheets. It is cheap. If you need it stronger you can double it up. But one little thing I don't like is that you end up with a big 'ol edge on the outside of your fairing that you have to fill and sand to make it look good.

Yeah but some uf us build weird things and are not concerned with the details Powder is of course correct. And sanding damages the cardboard which requires more filling. Thin CA fits in the equation somewhere too. I really like the 1/64 ply...can you say 'Michael's coupon

Depending on the dimensions of the shroud, 1/64" aircraft ply. It is very easy to finish and *incredibly* strong when formed into a shroud. I did my entire 1:100 scale N1 in this as well as my 4X Mars Lander. Great stuff. I've even formed large diameter (4" - 12") body tubes out of the stuff.

Another is very thin G10

For a simple but durable approach for smaller shrouds, you can just make them from card stock, but double up on them. very strong and easy to make.

jim

What I'm thinking about is a 1/17.5 Jupiter C/Juno 1. I am gathering data at the moment, trying to figure out the general construction of the thing. I found a great site on the Redstone MRBM and am extrapolating a lot of the stuff over, as they were all built on the same assembly line. It will have scale fins (if all goes well with my BT60 based test booster).
I'm fiddling with modifying the centering rings (29mm to 4"), adding the fin root extensions to the rings in the fin can area, kinda replicating the original's construction.
The fairing above the booster is the one in question. It is actually a "double taper", I may just turn the upper section out of solid something, and do some sort of built up and sheeted treatment on the larger lower taper. It will all involve a bunch of custom rings and center tubing towards the top...weight up towards the top will be "encouraged", based on CG/CP issues. I'm leaning toward either thin ply sheeting or planking.
And my mind spins with details...shipbuilding pin nails for rivets, tiny screws for the engine section/body attachment...on and on...I may just buy some parts and build up a fin can and see how that goes before I go completely nutso on this...the fin can could become anything "Redstone based", being common to all the ships...
...all the time remembering that this thing has to fly...and survive the landing...

Here's the Redstone MRBM link... https://www.geocities.com/redstone_mrbm/index.html

also, if you go to the Atlas link, theres a bunch of great detail stuff on the Mercury Atlas system...

Back to the drawing board...literally...

Thanks all,
Dave, brain damaged for sure here...

Posterboard is great stuff, if they are large enough for your project plain old manilla file folds are very nice or unsupported long transitions. multi Rings with light ply (1/64 3 ply aircraft ply) makes great lightweight interral stiffeneers for even lighter weight papers and cardstock transitions.
Powder is right on concerning wetting your material. you would end up with ruffles and ridges in all sorts of unwanted places.

If cardstock, posterboard or file card material seem to thin for your model. consider the same 1/64th or 3/64th 3 ply plywood can be rolled into fairly tight conical transitions. Polycarbonate sheeting can be had in 2' x 4' sheets in .010", 020" .030" etc. thicknesses which give an increadably smooth (and hard to paint) surface for transitions. these can by purchase thur McMaster-Carr and other plastic suppliers. I've also used a 3mil mylar available from most art supply stores that is also a good choice for large, long transitions. With most of these latter materials you'll have to watch which adhesives are best. I've also found a back up strip added to the inside of the transition allowing a butt joint on the surface is much more desirable for finishing then a lap joint.

Here's an 8" BT-80 to BT-50 cardstock (file folder) transition that is unsupported internally. it was CA soaked and sanded after assemble. The transition seam runs under the lower fin in this pic. Please note that the Fins and other details are all surface CA/Epoxy mounted only, NO thru the wall anything. I'm happy to report this Styx SS-N2 model has flown 6 or 7 times without damage to the fins or cardstock transition.
Hope this helps

Nice rocket, Micromeister. Could you tell us how you got the "flaps" detail on the fins?

I just finished a 5060 transition made from 110# cardstock for an upscale X-Ray I'm working on. Here's how I built it.

First, I calculated how long I needed the transition and the shoulders. In my case, the transition needed to be 1.7", and I set one of the shoulders to .75"and the other to 1", for a total length of 3.45". I created a cardstock tube that was 1/4" shorter than the overall length of the final piece (3.2"). Then I cut out two disks of foamcore the same as the inside diameter of the core. One disk was 1/2" thick, and went in the BT-50 end, while the other was 1/4" thick and went in the BT-60 end. I then made a 1" shoulder for the BT-60. I also made two centering rings and a 1/4" foamcore disk to go inside the BT-60. I glued the rings to the core at the appropriate places and then glued the shoulder to the rings. The shoulder projected 1/4" beyond the core - that's where the larger foamcore disk went. When dry, the core was round and square. I cut out a couple of strips of paper to build up the shoulder stops for each end (how many depends on the transition itself) and made a transition using the instructions in Stine's Handbook. This was glued in place over the stops. When everything was dry, I gave the transition part a coat of CA glue, and sanded it smooth when dry. The final result looks pretty good (can't post a pic, since I don't have a digital cam right now). I will attach a pdf of the transition parts for the upscale so you can see how every thing was made and goes together (there is a diagram of the transition in the pdf.

Enjoy!

Greg

Originally posted by Polaris
Nice rocket, Micromeister. Could you tell us how you got the "flaps" detail on the fins?

Click to expand...

Sure Polaris:
Fins for this model started as 3/32" Basswood. After all 3 fins were cut to size and square match sanded, the control surface patterns were traced onto each side and deeply scored with a very sharp #11 knife point. Then each fin was sanded to it's airfoil shape. After shaping each elevator line was re-knifed to uniform depth before the first coat of primer. Each side was again scored with a needle point after each coat of primer and finish coat of paint. Tiny pieces of styrene rod were scrapped to the proper thickness and CAed in place to simulate the hinges after priming but before finsih coat painting.

After doing my 1st paper transition (and having found some nice programs that create them), I can see using them more...
Thin CA seems a common ingredient. My BT70 to BT20 one was rather "extreme" with a really tight curve at the small end for the rather thick material I used. I did use a couple of internal thin balsa formers to strengthen it some.

Your attachments prove that very nice results can be had using this method...really nice work!

Dave

The way I do this is to print a paper template using VCP. I use the paper template to cut out a cardstock former, and also some fibreglass (usually one light one heavy). You should transfer the tab that VCP prints to the cardstock, but not the fibreglass.

Roller some epoxy onto the cardstock former and place the light fibreglass on it. Let it start to cure but before it's fully cured, form the transition using CA to tack it in place. The tabs that VCP adds really help here.

Once it's cured you can add another one or more layers of fibreglass for added strength.

Here's some I made earlier:
https://www.nsrg.org.uk/darren/diary/20031218/Picture(11).jpg

And in situ:
https://www.northstarrocketry.org.uk/projects/tb3/construction_Cnv00023.jpg

I have never used fiberglass. Everything I have read makes it sound like a real pain to work with. Isn’t it heavy?

Originally posted by Polaris
I have never used fiberglass. Everything I have read makes it sound like a real pain to work with. Isn’t it heavy?

Click to expand...

Compared to what?

If done right, fiberglass doesn't have to add too much weight. Case in point, all fiberglass 1/8A duration models. https://www.venusrocketry.com/micromodelparachute.html

check this post
https://www.rocketryforum.com/showthread.php?s=&threadid=9987

I've made lots and lots of transistions...i really like this method the best.
As said before...thin CA really comes in handy.
Use the first link to the Shroud calc. It was easier for me to use. ::: shrugs ::: personnal preference.
If you want more details on how I made my transitions just ask.
No joke when I was done with these you would think that it was plastic...and they add little to no weight...also incredibly strong.
also if you want to use a type of wood...balsa is the way to go.
and i wouldn't suggest trying to bend it unless you are using a really wide tube. try using a paper outside and taking strips of balsa and glueing them to the inside of the paper about 2mm apart then wrap the paper around the tube.
check out this post also https://www.rocketryforum.com/showthread.php?s=&threadid=10692
it's basically a walk through on how i made the transition on this roc.
hope this helps.
if you have questions or anything ask..i'd be happy to help.
goodluck
-matt

Originally posted by rstaff3
If done right, fiberglass doesn't have to add too much weight. Case in point, all fiberglass 1/8A duration models. https://www.venusrocketry.com/micromodelparachute.html

Click to expand...

Thanks. That sure changes my outlook on fiberglass. Is there some place that covers light weight fiberglass construction techniques?

I can't remember any material on super light techniques, but I'm sure they are out there. If you don't get a response here, try contacting micromeister directly thru TRF.

Ive put together a paper conical extension for the nose cone of my BT60 Viking. The nosecone is a standard Estes ogive, but the Viking has a conical 25 degree upper section. I made it with the lower diameter of about an inch, the upper diameter .03 inch (theres a small hole in the top of the real nosecone). It was hard to get the upper curve going, ended up wrapping it around the pointy end of a pencil. Its soaked in thin CA and I am putting thick CA in it inside and out, hoping to make it stiff enough to sand smooth. It fits pretty well on the end of the cone, will probably smooth the transition with some plastic putty.

Incidently, the nosecone is currently painted with several light coats of Testor's sparycan Metalizer, no clear overcoat, I am surprised how durable this finish has turned out.

Dave