Snap Dragon
Scratch-Built Model Rocket

Part 5:   Body Tube Covers  

"Paint job" and "decals" integral with the body tube itself.   A Cheap Trick.

Click Here to skip the rambling narrative and get down to business.

I went to Maine a few years ago, arriving in early October just in time for the first light snow.  Everywhere I looked it was like a postcard.  Sigh.  

Took along a cheap little 35mm camera.  Spent over $100. for film.  Then over $200. for processing.  Whew!  Makes me appreciate the digital camera a lot more.  Many of them were bad, most of the rest mediocre.

But the scenery was so good that even the mediocre shots were appealing, and on top of that, I accidentally got a few good.  Scanned the best ones, and used one of  them for my desktop wallpaper at work.  

Someone installed a color laser printer and made the mistake of giving me access.  I had to test it to see how well it would do photos, and hey!  How about this Maine picture?  Nice shot of some tall trees, lake, and mountains in the background.  I left it laying around, as is my habit.

A few months later, I was scheduled to give a presentation at conference on psychological type in education (www.capt.org) and wanted to get folks to laugh.  I am willing to resort to the cheapest of  tricks to get an audience on my side.
 
What I wanted was a video of a homemade rocket that didn't work.  Dramatically so.  So I rolled a few tubes, put crude fins and a nose cone on one of them, and sprayed it with silver paint.  Made a little batch of propellant, wrapped a chunk of it in aluminum foil with a firecracker at the far end, and put it in the "airframe" where the motor should be.   I borrowed a camcorder, and videotaped the "launch."  

During the part about development of identity in relation to career aspirations, I mentioned that:  "...when I was in high school, I told all my friends that I was going to be a 'rocket scientist' when I grew up.  If they had known that I would become a career counselor, I might not have survived.

"Here is one of my rockets.....

(Play video... rocket smokes for a few seconds, then explodes.  Audience laughs, as hoped.)  

"Well I guess it's good that I went into counseling.  They say people go into helping professions because they need help...."

I rambled on and on, but nobody left until it was over.  Afterward, a member of the audience asked me:  "Have you seen that movie about the boys that made rockets.... forgot the name, but it's pretty good."   That was the first I'd heard of October Sky.  And it started me back into rocketry again.  So as much as I hate to admit it, guess I'm a BAR too.

Spring cleaning came to my office, and I found the remaining tubes and the Maine photo in a heap on my desk.  Hmmm.  Highly distractable, especially when cleaning, I wondered:  What if I wrapped the picture around a tube?  Found a bottle of Elmer's and did so.  Made a nicely decorated tube.  I cut the picture into three strips, and rolled a section around a different tube.  Stood up together, this made for a three-dimensional look, almost like real trees.  I envisioned making a lamp out of them but never did.  Of course.

By now, I'm sure you know where this is heading.  I could quit right here and you would figure it out.  Or you would say "why bother" and go do something else.  But that won't stop me, nooooo!  I spend most of my time talking to myself anyway, so the lack of an audience will not disuade me.  In fact, an audience that is not there is hardly disuasive at all.  

Thus I continue.

After building several airframes using posterboard tubes, I note that my fin spacing leaves much to be desired.  I have been using 1/2 inch angle iron and 1/2 x 3/8ths inch angle aluminum to provide the correct spacing from one fin to the next.  These angles are a great help in getting the fins on straight, but variations in the body tube diameter, and especially in the fin thickness, make this spacing incorrect much of the time.  The rockets fly OK, but they look kinda funny.  

I recalled a little helper that came with the Estes kits - a fin spacing/alignment guide.  It is printed on the instructions, just a rectangle with some straight lines in it.  You cut it out, wrap it around the body tube, and mark on the tube where the lines are.  This provides correct spacing, and helps (somewhat) with alignment.  

So perhaps I could make such guide for my body tubes?  I measure a tube's diameter and figure its circumference, and divide by three.  This gives me the correct spacing for three fins.  I go the the computer, create an image file and draw three lines, spaced 1/3rd circumference apart.  I can wrap this around the tube, mark the lines... Hey!  I could just glue it on with that fancy spray glue and mount the fins directly on it!  I could even use the whole length of the sheet of paper, it's gonna be wasted anyway.   And it just happens to be 11 inches long.  

I can print a horizontal line to show where the fin tips should reach, to help with fore/aft placement.  

So I print out two such guides on one sheet, and cut one of them off, a strip wide enough to go around the tube and then some, sprayed it with glue, and wrapped it around a tube....

It worked very nicely!  The fins went on straight, thanks to the angle-aluminum guide.  

They were evenly spaced thanks to the longitudinal lines, and fore/aft placement good enough that it would stand up on its own, thanks to the end-mark.   
A few falling maple leaves bring back visions of Maine... I'm using a whole sheet of paper, why print just the fin guide?  I could create fancy "decals" by printing them out and using that as the final wrap of paper.  I could easily make designs that would be a real pain to implement with paint.  I could even put photographs on the tubes!


So I went kinda wild.  And soon realized that it is really easy to do a bad job of this.  

Here are a few examples:
Fun to do, but they would make rather ugly airframes, I fear.  I'll use them anyway.  You may have seen one of them already.
  
Note that they are kinda dusky and drab looking.  These are printed on plain paper.  It occurs to me that I have some expensive glossy photo paper here somewhere..... (sound of drawers opening, cabinets rattling, things falling to the floor)  Hey!  I found it!  What luck.


Click Here to open the Word version of this graphic		 But if I am going to use dollar-a-sheet paper, I want a better design.  So I went online and found Kurt Schachner's collection of decal designs for historic Estes and Centuri models, from which this star-n-bar insignia was obtained.  

I used Word to make the gradient and the fin covers.  Yeah, why not cover the fins too, save a lot of sanding, painting, etc.  Besides, the paper serves to reinforce the wood, so I can use 3/32 inch balsa and it might not break right away.  

Here is a Word doc with 3 fin covers on it.  Guess I should work up a design that gets  3 fins plus tube cover on one sheet.  

I have a variation in yellow and blue.
And another one with a Boy Scouts motif
The wrap should be about 3 inches wide.  The body tubes average about 0.9 inches, so the circumference would be 2.82 inches.  Divide that by 3 and you get 0.94 inches between fins.  Since the paper thickness will add a bit, I am using a fin spacing of 1 inch here, and it is about right.  Fine tuning may be helpful, but this is good enough for a start.  


Here I am sizing up an ugly tube to see if it can be recovered.  Decided against it, thinking the extra coating of paper might make the new alignment lines incorrect.  I made a new tube instead.  
Sprayed the wrap with Super 77 and rolled it on.  This is easy!  

But I forgot something....
There were a couple of gaps in the final edge.  I had failed to pre-roll the edge.  That was not necessary with the plain paper, but this photo paper is much thicker and stiffer.

Elmer's didn't work, it just yawned wide open again.  So I tried a little super-glue and guess what!  It works really well.  
Note that I'm holding the edge down with a thick plastic bag.  Getting CA'd to something is funny when it happens to someone else....  Super glue doesn't seem to stick to polyethylene baggies at all.
So here is another wrapper.

I'm doing  the pre-roll thing this time.

Glued it on, and it works great.  No loose edges.  

Fin Covers 

You might have noticed the gaily-colored trapezoids on the printout.  Those are fin covers.  We need some fins to cover.
Here I'm cutting fins from 3/32 inch thick balsa.  The strip is 3 inches wide, so I split it in half.  
Thus each 6-inch section makes 4 fins.  The leading and trailing edges of these fins will be rounded or tapered with sandpaper, as illustrated on the Fins page.

 
A colorful trapezoid is cut out, with a lot of extra paper around the edges.  It is folded directly down the middle so that the colored stripes are symmetrical and even on both sides.

This is a test-fitting to make sure it goes in OK.  It does.  

Good way to get stickyfingers. But when I set the paper down, the spray blows it over!
Guess I could use a clothespin or something.

If you want the bond to be extra strong, spray the balsa with glue too.  

Fin is inserted into glued paper...

...folded in a Ziploc bag, and pressed firmly. The bag keeps my sticky fingers from adhering to the paper.  Don't want to leave any fingerprints, do we?

This procedure creates a fin packet, a colorful fold of heavy, glossy, pretty paper with a balsa fin somewhere inside it.  

By pressing at the edges with a fingernail, I find where the balsa begins and lay a non-skid ruler along that line.  Sharp knife is used to cut away the excess paper.  

I notice that it is so easy to cut through the balsa like this that I don't even notice when it happens.  Ruined a fin that way, but it suggests another technique, to glue paper to balsa, then cut it out.  

Root edge of each fin is sanded to remove excess paper and make the edge flat and true again.  The remaining paper flares out a little.  

I leave this frilly edge on believing that the tiny tendrils will make for a better glue joint.  

The aluminum bracket is rubber-banded to the body tube and aligned with one of the fin index markers.  A dollop of Elmer's is spread along the root edge, and the fin pressed into place.  After about 30 seconds, the aluminum guide is moved to one side so that the fin does not get stuck to it.  The fin is allowed to dry for a few minutes before adding the next.

Falling Fin Syndrome

When I first glued these fins to the body tube, they kept falling off!  Apparently, the glossy photo paper does not absorb Elmer's Glue as readily as plain paper.  I feared I would have to find a different glue.  But I left one sitting for 15 minutes, came back and tried to pull it off.  It did not come off easily, it was stuck on pretty well.  So I left it to dry overnight, and the resulting bond was quite strong.  So Elmer's is fine.  One must take a little more care in the beginning, and have a little patience in the middle for a good result at the end.  

Trailing Edge Surprise

Here is a bonus.  I hadn't planned on this and so did not do it very well.  

Instead of trimming the paper right up to the balsa, I left 1/4 inch or so and presed the edges together.

It made a nicely feathered trailing edge.  I'll try to do it better next time.  

But compared to the first of these I made with a very square end, the paper taper is grand.  
The edges can be trimmed with scissors so they are all even.

Here is that better job I promised.  Note that the fin itself is inside a covering of heavy polyethylene (a Ziploc freezer bag) to protect the finish.  

It worked!  The two on the left were done with the clamps, the one on the right wasn't.  It  can be fixed with a touch of super glue, but I prefer to do a good job to start with.  

I like clamps.  Clamps are good.

The left model uses the paper nose cone illustrated on that page.  It looks kinda awkward.  It needs a paint job.

The red nose cone is one I turned on a wood lathe.

Top Coat

This printed photo paper stays kind of "sticky" for a long time.  So after drying, I give it a couple of coats of clear "top coat" lacquer.  

This makes it much less sticky and more water resistant.  I understand that there are special fixative sprays for inkjet photo-paper.  Perhaps I should get some.  But this Plasticoat lacquer works petty well.

So far I have this one gaudy design.  More a test of concept than anything.  How about some of you rocket artists designing better ones and sending them to me?  I would be delighted to post any that you submit, with your permission, of course.

A good starting point might be Ye Olde Rocket Shoppe which offers a nice collection of decal designs from historic Estes and Centuri kits, as well as plans for many olde and newe rocket designs.  

Deepest thanks to  Kurt Schachner for collecting these the decal set from which I obtained the star-and-bar, and to Scott Hansen for putting them on the web.

Next:  Finishing up!

Jimmy Yawn
jyawn@sfcc.net
Recrystallized Rocketry

rev. 12/18/05