Z 29 Stealth--A Scratch Build Thread

[MParker]

Welcome to my first build thread. Once in a while I enjoy building a kit but for me it's all about scratch building the unconventional.
When it comes to building stuff usually I am not building rockets, I spend most of my time building "fine furniture" so my methods may differ from what's typical around here. I'm going to walk you through how and why I do things and maybe we can teach each other something along the way.

Here we go!

The Rocket is what I am calling the Z29 Stealth. It is built around 2.56" Blue Tube and will have a 29mm motor mount. I am expecting to hear a chorus of stick a 38mm in there but that's not going to happen just yet, there's a method to my madness.

The Altimeter will be located in the nose cone and will actuate a Archetype Rocketry Cable Cutter. I haven't selected an altimeter for this yet but I am thinking it will be either an RRC3 or a Raven.


1. Print out the Open Rocket fin pattern and cut it to size.
2. Select a piece of 1/4" MDF or similar to use as a pattern. Glue the printed fin pattern to the MDF lining up the root edge of the fin with a straight edge on your pattern stock.


3. Using your choice of crosscut saw (Radial Arm, Table saw, Miter saw) cut all of the outside straight edges that can be accessed with the power saw. Creep up on the paper pattern until you are pleased with the cut.




4. Using your choice of methods cut the interior angles. I used a combination of a bandsaw and a Japanese Pull Saw to accomplish this.



5. Using a chisel (or sandpaper) clean up the edges that were cut with the handsaw or bandsaw.


6. Now you have a completed fin pattern ready to make as many fins as you want.

 

[MParker]

7. Now that we have a pattern go ahead and trace the fin pattern onto your fin stock. I am using 3/16 ply here but you can substitute your preferred material. When tracing use a wide tip pen such as a Sharpie. We'll be cutting these out with a bandsaw and our goal will be to leave 1/16" to 1/8" extra


8. Trace each fin onto the ply. I adjusted my layout to maximize usage and have some space set aside for centering rings as well


9. In our next episode we will be cutting out the rough shapes on the bandsaw and trimming with a router. Stay Tuned.

 

[Madison Alum]

Neat looking design! Couple of questions: What is MDF and why did you cut the aft corner off of the tab? Clearance for the centering ring fillet?

 

[Pantherjon]

MDF is medium-density fiberboard..

 

[MParker]

Madison alum,
MDF is frequently used as a jig making material. It is used because it cuts easily yet is durable enough for jig/ pattern use. You can find it at any lumber store.

I cut the edge od te fin tab off so that i could easily get to one of the interior angles. It wasn't required but made life easier.

 

[MasonH]

That is an interesting fin design...

 

[Madison Alum]

MParker and Pantherjon,
Thanks for the replies. I guess I am one of those who ask questions instead of looking up what MDF is.

 

[MParker]

10. Once you get the rough cutouts of each fin done you are ready to refine the profile using the pattern that we previously created. Prepare several small 1"x1" pieces of carpet tape and attach one of the fins to your pattern. At this point you can either refine 1 fin at at time or attach more fins and do multiples at the same time. I ended up doing two at a time.


11. Set your bit height on the router table so that the bearing rides on the pattern.


12. Using push blocks or similar carefully move the pattern/fin assembly around cutting the entire perimeter of the fin.


13. Now you should have a set of identical fins. You will note that there is one area where the interior angle was too sharp and it resulted in a radius there. I ended up cleaning this up with a hand saw.


14. Now we are ready to chamfer the edges of the fins. Be sure to clearly remember or identify the fin root so that you do not chamfer the root. Set the bit height so that it cuts to the exact center of the fin. Since the plywood has an odd number of plies it is easy to visually identify the middle. Cut one side of the chamfer on each fin. Since we have now cut away the edge where the bearing will ride we need to reattach the pattern and then chamfer the opposite side.


15. Now we have 4 fins ready to go!

 

[Handeman]

Very interesting the way you do the fins. I've never done fins with non-straight edges. The furniture maker is definitely coming out. Waiting on how you do the fin slots!

I also use my router table for beveling the fins, but I do it a little different since I am looking for much sharper bevels. I clamp a straight edge on the table as a guide, then use a L shaped jig that is at about a 75º angle. I clamp the fin to the jig and move the jig past the router.

 

[MParker]

Handeman,

I like your high angle beveling method. I'll have to give that a shot on my next build.

 

[MParker]

16.Using the Open Rocket Fin guide, mark the fin locations. Extend the lines using your traditional method.


17. Mark the beginning and end of the slots. Even though we are going to use a jig to cut the slots it is always helpful to have the marks.


18. The plywood is "3/16" nominal thickness but in actuality is is .198" thick so our .1875" bit will require two passes in the body tube to create the correct slot width.


19. I used my mortising jig to cut the slots. It's a good thing the fins weren't any longer, these slots are about as long as my jig will accomodate!



20. Using preset start and stop points cut the slots. After the first pass rotate the tube into position for the second slot. Be sure to "creep up" on the correct width by checking with a fin after each pass. On subsequent slots be sure to use the same rotations so that each slot is equally spaced.


21. After some cleanup with an exacto knife the slots look pretty darn good.


22. A fin test fit indicates that the fin tabs are a bit long. We'll tackle this in the next installment of Z 29 Stealth


Gratuitous dry fit.

 

[MParker]

One of the goals of this project that I forgot to state in the beginning is to use no or very little epoxy. While I have the entire west systems kit and use it when required this build will go without it and I'll be much happier as a result. This glue choice is what led me to use Blue Tube rather than FWFG tubes.

23. I measured the excess tab length marked it on the fins and then ran them across my jointer. I could have used any number of methods to do this but the jointer is just so handy!



24. The next step is the motor mount. I marked the centering ring locations on the motor tube and then applied glue to both surfaces to be joined and then slid them into place,


The tail cone and aeropack are not glued in just yet.


25. After the glue had set up i added some fillets the titebond molding and trim glue.

 

[MParker]

26. I forgot to drill this hole ahead of time..


27. I'm using a Forged eyebolt flat washer, lockwasher and nut. te lockwasher is probably overkill given the next step.


28. This is one of the few epoxy uses on this build but JB weld is the right tool for the job.


29. To install the Aeropack you will need a bit of JB weld and some laquer thinner or acetone to clean up the excess.



30. After scuffing up the motor tube with some 80 grit spread the JB weld on the mating surface of the Aeropack. Don't use too much as it will just be more mess to clean up.


31. Push the Aeropack into place and note any glue squeeze out.


32. Using the aforementioned laquer thinner clean up the squeeze out so that it does not become a problem later on.


33. Move back to the other end and tie our shock cord onto the eye bolt using your preferred knot. I used a bowline since it and I are long friends.


34. Here's how the aft end looks with tail cone and Aeropack.



In the next edition we will seal the motor mount and prepare for installation.

 

[MParker]

Instead of doing steps I'm going to be more brief from now on unless someone wants more detail.

I attached the fins to the motor mount with Titebond 2 and filleted with titebond molding and trim glue.


After gluing the fins on I decided the rocket looked a bit short so I added an av-bay and a short section of body tube.


I then sanded the fins with 120grit in preparation for sealing


The whole rocket got a coat of sanding sealer (dewaxed shellac)


Then everything got a sanding with 320grit and is ready to paint!

 

[qquake2k]

Very interesting design and build. I'm loving your tools and methods. Where did you get the tail cone?