Jester's 10" FAT MAN build thread!

[Jester]

I decided it's time! Been talking about it, now it's time to put up or shut up! So, here it goes. I'm starting a scratch built clone of the Polecat 10" FAT MAN. Got a copy of the original instructions from PSLimo, (great guy by the way, lots of help), some 10" concrete tube, lots of pink foam board, and 98mm motor mount tubes and coupler from LOC. So stay tuned for the play by play action, and feel free to chime in if you have any experienced advice.

 

[cwbullet]

Please post lots of steps so we can all build one!

Where did you buy the concrete form tubes?

 

[Jester]

Hey Chuck, I ordered the tubes from Lowe's online. Very few stores have the 10" in stock. I purchased 4 at around $14.00 each, and got free shipping. FYI, 2 out of the 4 tubes were actually 11" in diameter.

 

[ThirstyBarbarian]

Hey Chuck, I ordered the tubes from Lowe's online. Very few stores have the 10" in stock. I purchased 4 at around $14.00 each, and got free shipping. FYI, 2 out of the 4 tubes were actually 11" in diameter.

I don’t have experience with these tubes, but I’ve heard that concrete form tubes sometimes vary in size within their “nominal” size. And the reason I was told is so they can slip them inside each other for shipping. So they might all be labeled 10”, but vary by a bit. I was also told that if you can shop for them in person, you can sometimes find one that can serve as a coupler inside another.

 

[ThirstyBarbarian]

How are you going to do the foam nosecone? There are a few threads about foam lathes, hot wire foam cutters, and templates for guiding the cutter. Are you using one of those techniques?

 

[cwbullet]

Hey Chuck, I ordered the tubes from Lowe's online. Very few stores have the 10" in stock. I purchased 4 at around $14.00 each, and got free shipping. FYI, 2 out of the 4 tubes were actually 11" in diameter.

Thanks. A fat man is one of favorite kits. I actually have a 10 inch polecat kit in the shed.

 

[rocketace]

I am planning something similar soon, so I be watching this closely!!!

 

[Jester]

How are you going to do the foam nosecone? There are a few threads about foam lathes, hot wire foam cutters, and templates for guiding the cutter. Are you using one of those techniques?

Well, probably all of the above. I have a 12 inch bench lathe that I'm hoping will turn the assembly. I have a model train transformer and some hot wire. I will definitely be useing a template.

 

[Jester]

The body tube is cut to length. I couldn't determine for sure if it was 34" or 37", so I went with 37", and can cut it down later if I need to. I trued the cut ends on a piece of tile covered with self adhesive DA sander sheets. Placed the tube on the sheets and began turning the tube. after about 3 minutes , it's a done deal.
I also cut the nosecone coupler to a length of 7 inches, then cut a scarf for the 2 ends to meet. Put it in the bodytube with some wax paper and glued the ends. So far, so good!

 

[Pepe Le Pew]

Excellent work Jester! That is going to be one tough monster!!!

 

[ThirstyBarbarian]

The body tube is cut to length. I couldn't determine for sure if it was 34" or 37", so I went with 37", and can cut it down later if I need to. I trued the cut ends on a piece of tile covered with self adhesive DA sander sheets. Placed the tube on the sheets and began turning the tube. after about 3 minutes , it's a done deal.
I also cut the nosecone coupler to a length of 7 inches, then cut a scarf for the 2 ends to meet. Put it in the bodytube with some wax paper and glued the ends. So far, so good!
View attachment 516251View attachment 516252

Looks good!

Can you explain what the term “scarf” means? You said you cut a “scarf“ for the two ends to meet?

EDIT: I found this definition for scarf used in the building trades: “a joint connecting two pieces of timber or metal in which the ends are beveled or notched so that they fit over or into each other.”

Can you describe what you did to join the ends? I can see how the joint is not in line with the tube and is at an angle. Are the ends of that cut also beveled or notched?

Thanks!

 

[Jester]

Can you describe what you did to join the ends? I can see how the joint is not in line with the tube and is at an angle. Are the ends of that cut also beveled or notched?

That's it exactly, the cut and butt together seam is at an angle, not perpendicular to the ends. Makes for a much stronger seam. No notch or bevels.

 

[Jester]

Hindsight is 20/20 so I am told. I ordered the standard coupler from LOC for the ejection piston and motor mount tube. I SHOULD have ordered a stiffy instead. Sooo, I decided to wrap the inside of the coupler and piston with 2 plies of glass. I the added a sheet of waxpaper and a balloon for squeez out. while that cures, it's time to start cutting foam!

 

[Dave Frost]

Great idea with the balloons. I'm gathering parts for a 7.5 inch version. Found a plastic 7.25 inch diameter Easter egg to make a mold for the nosecone. Tubes, centering rings, and couplers have been ordered from LOC. Good luck with your build.

 

[ThirstyBarbarian]

That's it exactly, the cut and butt together seam is at an angle, not perpendicular to the ends. Makes for a much stronger seam. No notch or bevels.

Thanks! I can see how that would be stronger.

 

[hball55]

Thanks. A fat man is one of favorite kits. I actually have a 10 inch polecat kit in the shed.

Get that puppy out! That’s an order, lol.

 

[cwbullet]

I will add that to the list to build this summer.

 

[Jester]

Working on the nosecone, got the foam cut, and made a scaled up template from an Estes nosecone. Discs are glued and waiting drying time to start forming the final shape.

 

[Sooner Boomer]

Two questions:
what glue did you use to glue the disks together?
Are you going to apply glass over the disks when they're shaped. (OK 3 questions...) Could you remove the foam after glassing?

 

[Jester]

I used yellow carpenters glue to attach the discs, it takes a while to dry. After final shaping, which may include the use of modeling clay, I plan to glass over the foam. When I'm happy with the glassing results, I plan on removing the foam, and a final cleanup with acetone.

 

[crossfire]

I used yellow carpenters glue to attach the discs, it takes a while to dry. After final shaping, which may include the use of modeling clay, I plan to glass over the foam. When I'm happy with the glassing results, I plan on removing the foam, and a final cleanup with acetone.

Why take the foam out?

 

[Jester]

Why take the foam out?

The hollow nosecone is need to provide room for the extended motor mout tube, which becomes an ejection cannon for the main chute. This is one method of dual deployment on a short rocket.

 

[Highpowerrocketyahoo]

Looks good so far!

 

[StreuB1]

Really enjoying this and looking forward to how it turns out.

More pics of the NC process would be great as well!

 

[Jester]

Nosecone update pics. Template is in place on first pic. Close enough

 

[Jester]

 

[StreuB1]

Did you just turn it on the lathe with a hand held improvised tool? Thats how I did mine back in the mid 90's. Haven't done one since but this project has me thinking.....

 

[BABAR]

The hollow nosecone is need to provide room for the extended motor mout tube, which becomes an ejection cannon for the main chute. This is one method of dual deployment on a short rocket.

Love using a hollow nose cone as a space for extension of main body components. Works great for boost gliders with internal pop pods. You can extend the pod often well into the nose cone, put the nose weight required for BOOST on the forward tip of the pod, and when POD ejects (coming down by chute), you have removed all that nose weight from the GLIDER. Maybe put a coating of JB Weld Or some other protection on the inside of the cone To protect it from melting from ejection particles.

It can also provide lots of extra space for stubby rockets with rear eject. Downsize the forward end of the motor mount and extend it all the way inside the nose cone until the diameter hits the inside of the cone. Again, stick your nose weight on the forward end of the mount so when it ejects, the main rocket body section weighs less (one of the down sides [pun intended] of rear eject is usually means the main rocket body comes down pointy end first. A little rough on the nose cone tip, so any weight you can relieve on descent is a plus).

 

[Jester]

So I decided to save weight and skip the glassing of the bodytube. I won't be flying anything bigger than an L motor. I did soak the tube exterior with laminating epoxy resin. Here it's sanded afterwards and ready for the first primer coat.

 

[Jester]