Level 2.9 MadCow Super DX3: No Fiberglass, No Carbon Fiber, no sweat ...

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Apr 8, 2012
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This is a continuation of my previous build thread: Level 3 MadCow Super DX3: No Fiberglass, No Carbon Fiber, no sweat ... ?

The actual build with pictures in the above link starts on the second page (post #41):

Well, after ~ 2 1/2 years fallow, I've restarted work on my extreme kit bash of a Madcow Super DX3:
recently christened "Leapy McWonder Woody"

I've been working on it for a few weeks and taken some pictures.


Above shows the completed external "cage" (on the right.) The "centering" rings
alternate 10 ply 1/4" plywood and 1/4" solid walnut plywood. The vertical pieces
between the rings are 10 ply 1/4" plywood.

In the middle of the picture is a standard 36" Super DX3 body tube. And on the left is
several Madcow couplers glued together. These slip into the body tube for (hopefully)
overkill strength.


Above is the completed 75mm motor tube assembly. The 36" body tube with couplers
slips over the top half of the motor tube assembly. The body tube will come down to the
middle double-wide walnut centering ring. This will leave the part showing in the first
picture exposed to the breeze.


Above is the transition for between the 4" body tube section an the 3" motor tube section.
I wanted to make sure that the shock cord/drogue chute wouldn't get hung up on the step
when I am loading them. Space will be tight, so I need make use of the top part of the motor tube.


Above is a 4 braid of 1500 lb Kevlar cord. (You can see a 3 braid of 2000 lb
Kevlar in the right transition picture above.) It's kind of irrationally, but standard
rocket Kevlar shock cords seem "too expense". So I Google'd around looking for
something cheaper. Turns out Kevlar rope, etc is expensive. However, I found
1500 lb and 2000 lb cord that is a little bit more reasonably priced. So I've been
braiding it to the size I want. It takes a while to do, but it like knitting;
something you can do while your mind is otherwise occupied.

I recently decided that a plastic nosecone won't do. So I got some 13 ply 3/4" birch plywood
so I could create a wooden one. Can you say "69 ply nosecone?"


The first thing I did was create a profile. I put the plastic nosecone in a body tube and held
the body tube down with my "box-o-lead-shot". I used a jerry-rigged ... well see the picture.
I traced around the nosecone to make a pattern.

Above is the nosecone blank with the pattern overlayed.


The blank started out really heavy.


But after some freehand hacking at the table saw, it's not quite as bad.

The blank is not glued up yet and I will be cutting out the interior so that the walls
of the nosecone are ~ 5/8" thick. I'm guestimating that it will be under 2 lbs when
finished, but who know.

More to come when I have some more progress to show.
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It would be totally cool to say no epoxy was harmed in the making of this rocket....
It would be totally cool to say no epoxy was harmed in the making of this rocket....
I am using epoxy, but I don't think I've harmed it.

If I was epoxy, I'd want to be used. In fact, having to stay in my tube/bottle/can until no good, that would be epoxy abuse.
I've made significant progress so I thought I'd do an update.

I hollowed out the nosecone blank slices:

blankGutting1.1500.jpg blankGutting2.1500.jpg

Which cut down the weight a bit:


(Above is after the slices were epoxied together.)

Next I hacked stuff at at 45 degree angle:


and then at 22.5 degrees:


Then I marked on at 45 degree using the pattern so that I could
take off the corners on the upper part of the nosecone:


Next I did a little free hand hacking on the table saw.

After that I created the shoulder. At first, I tried to do it with my
belt sander, but that was slow and hard to keep to just the shoulder
area so I switched to a shoe rasp:


It was quite a bit of work, but it turned out pretty well:


As you can see in the photo, I taped just above the shoulder
cut so that I didn't cut where I didn't want to.

Next up was to create a negative mold of the Super DX3 plastic nosecone.

I want this so that I can accurately compare the wooden nosecone to the original
while I was shaping it.

The idea is that I'll sprinkle a bit of lamp black (soot) into the mold and push
the wooden nosecone into it. Whatever comes out black need to be loped off.

I used fiberglass tape and laminating epoxy to create the mold.

I talked with various rocket buddies about how to do this. One person emphasized
that I need to be very careful to make sure that I only fiberglass ... ah ... the monotonically
increasing part of the nosecone. He had horror stories about this so I took it to heart.

In this picture:


you can sort of see at the bottom some polyethylene that I wrapped around the shoulder area.
(I didn't think to take a better photo.)

I wrapped paper around the shoulder until it was slightly higher than the end of the nosecone.
Then I wrapped the polyethylene over that and used some smooth shiny "electrical" tape between
the polyethylene and the bottom of the nose cone.

That worked pretty well and I only had to whack on the mold quite a bit with a rubber
hammer to get it to pop out:

... To be continued. I've reached the 10 pix limit for the post
(curious limitation. I can just make another post and have as many pix as i want, right?)
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As I was saying ...

The polyethylene worked pretty well and I only had to whack on the mold quite a bit with a rubber
hammer to get it to pop out:


Forgot to mention in the previous post: I used orange oil as a release agent. I bought
some spray-on designed-to-be-a-release-agent stuff, but when I went to grab it, it was gone.
(I.e. I couldn't find it in my oh so neat and tidy rocket lair.) It probably got knocked behind the
drier or something by ... ah ... hum ... the dog. Yeh, that's the ticket!

If you look closely under the head of the hammer, you can sort'a see the significant
indentations that were made while I was whacking. (Another pic opportunity missed :)

Next up: Shaping

My intent has always been to use a belt sander to do the shaping. (Why do it the easy way
with a lathe when you can do a crappier job doing it by hand.)

So the first step was to jerry-rig a laptop shaper:


This actually works pretty well. As I was shaping, it seemed that if I started at the
bottom of the nosecone and held the nosecone at a 45 degree angle to the motion of
the belt and rotated the nosecone while slowly moving toward the tip, it was "automatically"
smoothing the irregularities out.

My theory is that at an angle, the low part of the rearward part is coinciding with the higher
part of the more forward part (or vise-versa.) I might be totally out to lunch on that, it's an
intuition. I have a long was to go, we'll see.

Here's a couple of pix of the current state. Note that the weight has crept down just a bit more.
not sure if 2 lbs is realistic (but I still have a lot of material to remove):


Above you can sort'a see the arches that will show on one set of sides.
These are more visible than the pic shows. They should be even more
prominent with a coat of epoxy clear coat.

This pic shows the 90 degree rotation side of the nosecone:


To my eye, the above pic shows how far I have to to go shape wise.

Never the less, it looks surprisingly good for this early stage.

More to come when I have something significant to show.
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I've made a bit more progress.

I've been concerned about the current fin attachment robustness for a while now. The existing design
didn't seem as strong as through the body (because there isn't a body.) So after much pondering,
I came up with "the FrankenZipper project":

frankenBrace1.2048.jpg frankenBrace2.2048.jpg

The new rectangular braces are rock maple that I made from my son's old wooden blocks.
They are 1 3/4" long, 5/8" wide and 1/4" thick. I am no longer concerned about the fins coming
off. The fact that it's likely much dragier is just a extra bonus.

I've also made progress on the nose code. It's fairly close to done:


So far, the fiberglass mold hasn't been too useful. It's just showing me a couple of nickle sized
patches are "too high".

I don't think making the mold was a waste, however. It was my first fiberglass lay-up and it went remarkably
well (especially given my ability to channel Lucy Ricardo without thinking about it too much.)

I now I have confidence that my first tip-to-tip won't be a scary mess.

I also have a couple of re-purposes ideas for the mold. Either it will be a "condom" to protect the nosecone
for travel (or other protection needs) or I'll use it for the nose cone of another rocket I'm planning to build.
(Yes, my parent's grew up in the depression, why do you ask?)

As I've gotten closer to the right shape for the nosecone, working on it has gotten more nerve-racking.
I've already taken off a bit too much in a little 3/4" patch near the shoulder (hence the masking tape.)

I've had moments of "f**k it, I'll just finish the tip and call it good" (It's still a bit square-ish.)
But I'm not there yet. Likely the next "oops" will define when it's "good enough".

Looking forward, I just need to do a little reinforcement work for the rail buttons and then I'll be ready
to glue on the body-tube-couplers-complex and the rear section will be done (Yeh!)
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I finished shaping the nose cone. (Yeh!)

noseconeDone1.jpg noseconeDone2.jpg

I used the belt sander some more and when it was close but not so close that
I was going to go too far any second, I switched to a rasp.

With the rasp, I could more easily feel where the "not round-ies" were compared
to the belt sander. It turned out mostly round. From 3 feet away, it looks perfect.
If you hold it in your hands and rotate it, you can feel that it's not quite perfect.
I.e. it's perfect enough.

It's weighs a little under 2 1/2 pounds. I could try to carve out some of the extra material
on the inside, but it's not worth it. And I figure nose weight is good for stability.
(Since I can't throw this puppy into rockSim, putting my thumb on the scale (so
to speak) is a good thing.)

I glued the lower body tube onto the motor tube assemble and added 15/15 rail buttons
on stand offs. Here's a picture (with the nosecone where the electronics bay will be):


All well and good. However, the next bit didn't go as planned. ...

The top 7" of the body tube does not have internal couplers to strengthen
it. I was concerned that this might be a weak point that could cause problems.

My first thought was to glue on (say) 1/8" by 3/8" by 12" sticks every (say) 30 degrees
around the top of the lower body tube. However, I came up with a "much better" idea:
wrap 1/16" birch plywood around the top of the body tube.

I steam bent the plywood around a spare body tube and wrapped it with cord then let it
dry. It worked, but when I removed it from the form, it sprang back to to sort
of a C shape. No problem, I said. (Well, perhaps ...)

So I glued the plywood around the body tube. The plywood was only 12" wide so I
had to add a 1" strip to completely wrap the body tube. Here's what it looked like after
I sanded around the 1" strip to make it round. (Since the plywood wasn't completely bent,
The ends pointed up a bit. There was CA glue under the tips, so ... No Problem ... right?)


I actually like the way it turned out. "Cool, you can see the plywood layers"

But then I tried to fit the electronics bay into the top of the body tube. It didn't
fit. WTF? It turns out that the funky not-quite-the-right-shape plywood wrap distorted
the shape of the body tube:


So I tried to squish it to be round, but that didn't work and sort of "broke" the body
tube a bit (I'll spare you the boring details.)

My first thought was to make a "centering" ring for the outside to force the tube
to be round:


That sort'a worked, but it still wasn't completely round. Arg, the centering ring took
a while to make.

So I decided that I would just have to sand out the inside of the body tube so that
the electronics bay would fit. Given that it was a bit broken, I decided to wrap the top
bit with 1/32" plywood. Here's what that looked like:


After a lot of sanding, I was able to get the electronics bay to fit (rather nicely.)
I guess any landing you can walk away from is a good landing.

So the lower section is finished, the electronics bay fits, ... all good.

And to get a feel for how it's going to look, I popped a 12" body tube on top
of the electronics bay and added the nosecone:


The "real" top section will be around 36" long so the "real" rocket will be about
2 feet taller.

It's getting close. I'm excited. I think it's shaping up to be a super-(wacky)-cool rocket,
despite (or because of?) the recent adventure.

Stay tuned ...
I talked about rail button reinforcement in a previous post.
Here's what I was referring to:


The rail button screw (#8 ~ 1 1/2" long) goes through the pine upright
between the oak pieces. The oak pieces are glued to the motor tube,
centering ring and upright. They are also screwed into the shock cord

shockCord bulkhead.500.png

I added the same sort of oak reinforcement pieces 2 other places 120 degrees
apart. You can sort of see one of them to the right in the first picture.

They also have screws into the bulkhead. I added these to make sure the
shock cord bulkhead was secure and wouldn't pull out. What can I say,
I like belts and suspenders.

I also wanted to show a close up of the bottom rail button attachment:


I created two little oak pieces that butt up against the vertical plywood
piece and the rear centering ring ("thrust plate".) Over these I glued
a piece of maple. It's a bit hard to see, but I also created an oak piece that
is curved to match the centering ring on the bottom and flat on the top.
This piece is the same height as the top of the maple piece. Over
the top of both pieces is a flat piece of oak.

At first I try to create a piece of oak that was cut out to do the job of
all the pieces described above. That was hopelessly difficult, so I punted.
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The nosecone is now (really) finished.


After I finished shaping the nosecone, there was still more to do. I wanted to use
the nosecone to house my BeeLine tracker.

I've created electronics bays in three of my nosecones. In each case I've use threaded
rod. The problem with threaded rod is that it is conductive and therefore would interfere
with the BeeLine transmission.

Given that the nosecone (and lots of other parts of the rocket) are wood, I wondered
if I could use a wooden dowel to mount the sled for the tracker.

So I bought some 3/8" birch dowel and a tap and die set.

Creating threads using dies made for metal: not easy:


When I first tried to create threads on the dowel, it didn't go too well. Even using the
coarse threads (16 threads be inch) I ended up just stripping off the outer layer of the
dowel leaving almost no trace of threads.

With some practice, I was able to create some pretty ragged threads:


In the above first try, I used CA glue on top of the parts of the threads that were missing
and then ran the die over the threads again. This didn't work very well because the CA is pretty
brittle. I decided to start over.

I was definitely getting better at running the die. In the second try, I used 5 min epoxy
to fill in the places where the threads were missing:


Not too bad. I tried to improve the above by added epoxy to the areas that were still
sub-standard. This didn't work because I waited too long and the epoxy became too

I decided to make one more try. Although not perfect, it turned out significantly better:


In the above third try I used AeroPoxy. With the low temperatures in my garage this time of year,
the epoxy took a long time to cure. This made it much easier to catch it while it was still
slightly soft but not gummy.

When I ran the die over the "just right" epoxy, it created long continuous "chips" like you
might get on a metal lathe. It was very satisfying.

I use this "third try" dowel in the nosecone:


I created a bulkplate to attached the u-bolt to:


Here's a picture of all the parts of the nosecone:


I'm really pleased with how it turned out. Final weight: just under 3 lbs.

Still fiddling with the airframe:

One day while looking at the lower section of the rocket, I realized that after the
frankenZipper upgrade, the part just above it was now the weak link. Remembering from
my 8th grade geometry class that triangles are always rigid, I decided to add cross
members in all the little square boxes:


I cut and belt sanded 3/8" dowels into the proper shape and then AeroPoxied them in.

I only had one more thing to do and then the airframe would be finished.

Upper body section:

The upper section of the rocket is made from a 31" Madcow 4" body tube.
I added couplers inside for strength:


If you click on the above, you can see some cut outs I made with a Dremel tool
using a diamond burr.

I had to cut these out because when I made sure there was enough space for the 3 1/2"
nosecone shoulder, I forgot about the wing nuts that attach the bulkplate to the

Wood paneling:

I paneled the upper section with two wraps of 1/32" birch plywood:

Arg. I've once again reached my 10 pix limit for a post. More "real soon now"
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As I was saying ...

Wood paneling:

I paneled the upper section with two wraps of 1/32" birch plywood. The 1/32" plywood is
thin enough that I didn't need to steam bend it. I glued it and then wrapped it with string
until the glue cured:


Here's how it looked once I sanded the area where the final 12" wide piece of ply started
(on the left) and ended (on the right.)


Airframe finished:

Some pix of the finished airframe:

airframeFinished.jpg airframeFinished.2.jpg airframeFinished.3.jpg

Here's a link to hi-res version of the above:

Well, that's a tank!

You say that like it's a bad thing. :)

Actually, it weighs 14 lbs 3 oz. The fiberglass 4" Madcow DX3 XL weighs 14 lbs
in parts alone.

Wood is an amazing advanced composite material. I'm planning to fly Woody this
summer at Back Rock.

My current thought is:

MudRoc: 54mm K805 maiden flight (or something with more ave N.) K2050(?)

MudRoc or Aeronaut: max K or small L

Aeronaut or XPRS: max L

The motor tube is long enough for an Aerotech 75/7680. Once I have my level 3,
I'd like to fly it with M1850W.

I'll be getting first hand experience as to whether this tank is up to the task(s)
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Hey, some people like to needle the sky, some like to float, some like to punch the sky right in the face. It's all good!
That is amazing work!

The nose cone and body structure alone, but threading a wood dowel? Fantastic.

Please tell us you're just going to varnish or polish the forward section. That graining deserves to be seen!
That is amazing work!

The nose cone and body structure alone, but threading a wood dowel? Fantastic.

Please tell us you're just going to varnish or polish the forward section. That graining deserves to be seen!

Thanks. The photos don't really do the grain justices. Parts are very striking.

I'm planning to use epoxy clear coat:


It's made for creating the very thick, clear finish on wooden bar tops.

I've used it before to protect the flimsy paper on a crayon rocket I built.
It creates a beautiful, crystal clear, hard finish.

It has a very low viscosity. For the crayon rocket, I hung the body tube vertically
and use a sponge to wipe it on starting from the top. Any excess flows down and forms a
annular "drop" around the bottom of the tube. I periodically wiped this excess off
until the clear coat hardened enough to stop flowing.

This mechanism leaves the surface very even with no blemishes. Much, much nicer
than any finish I've ever be able to get with spay paint or a brush. (As I've mentioned
before, I'm a bit of a klutz. So being able to get such a nice finish is amazing to me. *)

I just need to wait for the weather to become reliably warmer. The instructions for
the clear coat call for temperatures above 75 degrees.

* I hope I didn't jinx it by saying that. :)
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Leapy McWonder Woody's altimeter bay was inherited from his late father
"Leapy McWonder Moose":


Luckily, it was built like a tank (to coin a phase.) :)

In this picture, you can see the Madcow body tube I shrunk and epoxied
into place (the end is the shiny black ring an inch or two in):


Upgrade to redundant everything:

I had "a series of unfortunate events" with dual deploy a few years back.
Sadly, Woody's father was one of the victims.

It really bummed me out for a while. But I came out of my (rocket) funk
when I decided that redundant everything was the way to deal with
"failure was all too often an option." Since I went with "all redundancy, all
the time" I have had perfect dual deploy every time. Knock on wood (so to

Leapy McWonder Moose's altimeter bay was set up for non-redundant dual
deploy, so I needed to upgrade it.

When I built the altimeter bay initially, I super-sized it. It was made using
two Madcow couplers glued together. And fortunately, a jumbo altimeter bay
needed a jumbo altimeter sled so I had plenty of room to work with:


In the above picture, the 9V battery box on the left is new. Its made of
hickory. Why did I make it out of hickory? Because: I could, I had some
and (irrelevantly) it has the highest bend strength of any wood.

Here's a close-up so you can marvel at it's wonder:


Wires and switches, and wing nuts, oh my!:

Redundant everything means lots of wires:


The cable with red, white and black wires is for an optional
extra loud PerfectFlite StratoLogger 100 speaker:


The speaker is the round, black thingy top left. It is, in fact, pretty darn loud.
Sadly, the StratoLogger 100 isn't made any more. Lucky for me, mine
survived all my dual deploy mishaps.

I also had to add a switch:


The new switch is on the left. I've had several people recommend this
type of switch.

The labeling offends my "Mom! The carrots are touch the mashed potatoes!
Fix it! Fix it!"
inner OCD. But I'm a grown-up, I can handle it. I did have
to decide if on is "110" or "220". I think we can all agree that all right
thinking people would choose 220 for on.

I also had to orient the switch so that the screw-driver slot is pointing vertically
when the switch is on (pointing to the sky.) This was kind of a pain-in-the-ass to
do because the switch was covered in epoxy and the wires were making it rotate,
etc, but it had to be done. You can also see that when I installed the first
switch long ago, I did it so green is up. Duh. :facepalm:

Wing nuts? What's so special about wing nuts? We don't need no stinking wing nuts!

I was wandering around McMaster Carr a while back and stumbled onto 4-40 wing nuts.
I didn't know you could have 4-40 wing nuts. So bought some. They're pretty nice for
altimeter mounting when you want to be able to move altimeters easily:


And that concludes this heart warming story of how a daddy rocket's heart went on
to help his son "get his wood on".
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Well the weather is still too cold for epoxy clear coating and
my L3 cert (attempt) 4" Madcow fiberglass DX3 XL kit still hasn't
arrived. So I have "too much time on my hands."

So I decided that Leapy McWonder Woody needs to learn how to whistle:


I have always enjoyed it when rockets whistle when they take off.
Unfortunately, none of my rockets have ever done it. I'm not sure why
some rockets whistle. I've conjectured that it's split fins, but I think
I've hear rockets without split fins whistle.

Rather than leave it to chance whether Woody whistles, I decided
to force the issue and get a real whistle.

I know that some whistles won't work if you blow too hard, so I decided
to buy several kinds:


I've created "sleds" for each of the smaller kinds and glued some "ears"
on the train whistle. The sleds attach to the rocket with 4-40 machine
screws into these mounting blocks:


The whistle on the left of the line-up picture is a "siren whistle ring."
Here's a close-up:


I remember these fondly from my childhood. This was the first kind
of whistle I thought of for a whistling rocket. Unfortunately, it doesn't
look like these are made any more. I had to buy a "collector's" item
on E-bay. I'm not going to mention the "I just gotta have it" price I paid.

I'd be interested in hearing from anyone who knows or has a theory about
how whistling rockets work.

* full quote:

"Oh, maybe just whistle. You know how to whistle, don't you, Steve?
You just put your lips together and... blow."

Lauren Bacall to Humphrey Bogart in "To Have and Have Not" 1944
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I got an e-mail from Michael Klett RE whistling rockets:

Very cool. I love the whistling rockets, too. Split fins or fins with holes seem to do it more.

The Madcow 2.6" Army Hawk MIM-23B (https://www.madcowrocketry.com/2-6-army-hawk-mim-23b/) seems to be really good at it. It's on my build list. Use a fast burn motor to reach max velocity right off the pad and after the motor burns out you can hear the whistle on the way up before it gets too far away.

There was one launch where I was out looking for an Estes Swift or Mosquito that my son flew and was well away from the launch pads. There was an HPR rocket that went up but no event or ejection. It was coming down in a flat not too far from me. About 300 yards up the nose found its way towards the ground and it just accelerated into a Lake Stake landing 50 yards or so away from me. But that last 300 yards sounded like the bomb footage from the WWII movies. It was thrilling and chilling at the same time. I loved it!

So someday I'm gonna build that Hawk. Someday...