Build Thread: Spudnik

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Alan R

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First of all, let's dispense with the obvious other thing this might be right now, and I will tell you that it's supposed to be a potato. My attempt at sculpting and painting (mostly painting) didn't quite match the wondrous vision in my mind.

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Alan R

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Here was the original build plan:
build mmt 18mm
epoxy plastic fork to motor tube and cr (90 degree attachment to top ring)
slit/cut body tube
slide in complete mmt and fins
cut off a few inches of upper tube for nose cone
make coupler/shoulder for nose piece
add a centering ring to nose shoulder with shock attachment point
make outside centering rings for potato wrap (wavy cr's!!!)
make 'potato' wrap around body. go all the way over the top of bt
cut potato wrap at nc point

And I will tell you that it all got scrapped in the process.
 

mbeels

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I have a lot of reaction, but I'm speechless!

That is pretty super unique, are you going to launch it? The forks part is kind of brilliant!
 

Alan R

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Yes, at one point I did work from an OR file. But OR files dont really work that good with plastic fork fins, and an elliptical body shape (yes, transitions, I know).
But it did give me the printouts for the centering rings. Whoo hoo.

I adjusted the OR file for the CR's after I made the inner tube. Rolled inner tube around a piece of PVC. It's real close to 2" diameter. You can see the completed motor mount. MMT rolled from white paper around a motor, the inner BT is rolled from kraft paper. Centering rings on the mmt are doubled up Capn' Crunch Cardboard.
Red straw on mmt is for kevlar thread shock cord attachment.

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BABAR

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Great concept.

The nose cone looks like an egg, I was thinking if it comes in ballistic, you’ve got scrambled eggs and hash browns. If it CATOS you’ve got eggs and French fries.

Some priors


Mine
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Alan R

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The nose cone looks like an egg, I was thinking if it comes in ballistic, you’ve got scrambled eggs and hash browns. If it CATOS you’ve got eggs and French fries.
ya, see the original plan up there.. it was to cut off the bt at the top for the nose and paper mache it down to make a seamless transition. I decided to just 3d print the nose. Then I would paper over the 3d printed nose also. Then I got lazy and frustrated with the sculpting. This is the 2nd nc, the first one was taller and i didnt like the look. I think it should be even shorter now.
If it catos, then, having recently returned from Spain (see my posts in the corona thread HA), I would call it a Spanish omelette - eggs and patatas. corrección: huevos y patatas.
 
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Alan R

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Originally I was going to go the other way with the forks, and cut them off at a nice angle so I'd have some good glue surface area. They would attach directly to motor tube and the top cr...
but that didnt work out, and I tore out the first one and scrapped that idea. Then I decided I could maybe sandwich the tines between some balsa. It would also look better - like a fork stuck in the tater.


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Alan R

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I had actually glued in a fork that way. Didn't like it, didn't trust it to hold up. Then ripped it out, tore out the body tube around the mmt, and re-wrapped the bt. You can see the dents from the first attempt.
Realized I could get away with just one balsa piece. All I needed was one big surface for the fork and epoxy. The balsa pieces went in, used Titebond to attach to the motor tube and bottom cr, then forks were epoxied onto the balsa.
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Alan R

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Time for rings. These go on the outside of the tube to somewhat simulate a potato shape. Just single layer cardstock, not a lot of stress on it. Doing this reminded me of building the Acme Spitfire.
Slots cut in the rings for an internal launch lug. Thanks @BABAR ! the red straw is a perfect fit - maybe too perfect?
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Alan R

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Turns out ... that red straw was just a bit too tight. too much friction. It would probably work for a couple of short lugs, but there was way too much friction over the whole length. I pulled it out.
I wrapped my launch rod with a layer of scotch tape to give it a hair more diameter, and rolled a new launch lug. Poked it down through the slots.
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Alan R

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Its too tall. No way that looks like a tater. Attached (first) 3d printed nc.
I need to cut down the length. And make it fatter. I just added a bigger ring to the center.
Looking a little better now

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Alan R

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Need to say that at this point, I tested the launch lug again and I think it shrunk while drying. Grrr. It had way too much friction. Ripped it out, and made another one. This time I put the launch rod in the red straw, and wrapped the paper on the red straw. Plenty of diameter now so it won't hang.
Notched my rings, pulled out the old one and glued the new one in.

Now I have three ways to go with the sculpting, vertical, horizontal or a spiral. Decided the spiral would probably give me the most leeway to make it look right. Glued on one strip of kraft paper wrap, and let it dry.

It didn't look good, it didn't glue good. At this point I'm getting kind of frustrated because so far i've had to do everything at least twice. Sometimes for purely aesthetic reasons, but still getting to be a pain. The original plan pretty much scrapped and out the window. By now I'm just making it up as I go.
 

mbeels

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The original plan pretty much scrapped and out the window. By now I'm just making it up as I go.
You're forging ahead in new build territory. That's pretty much how most of mine go!
 
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Alan R

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I think the third attempt. i tried the kraft paper wrap horizontal, wrap spiral, vertical... nothing seemed quite right it was just too stiff. went back to the printer paper and brushed both sides with glue/water it really worked a lot better. its just going to need a better paint job than I originally planned.

looks pretty potato-ey to me. :D
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Funkworks

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Looks to me like nothing but your run-of-the-mill space spud.

potato moon outside box.jpg
potato moon side panel closeup.jpg

(I actually never knew this ever existed until today)
 

Alan R

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You wouldn't believe all the oddball rocket things I have laying around here. Or maybe you would :D
I might start a new gallery thread for that.
 

Alan R

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picked up some modeling clay at the $1 store. 200g for 12 sticks is somewhere around 17g/stick. One should be enough for starters. no more epoxy nickels.

This is also nc version 2. shorter looks better and a hair smaller diameter for a better fit without sanding.

At this point I only had one corner of my little bench to work on.. ha.

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Alan R

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let all that dry... paint job time.. a potato is .. tan with a darker spackle maybe? hA.

When I was looking at it after the paint job, I realized I should have done another layer, or at least patch over the wrinkly-looking spots when I was gluing the paper on. Smoothing out the ridges and craters would have really helped the looks.

After the paint is dry, add a bra strap and a parachute and we're ready to go.

I gave it a swing test, seemed pretty good, but I poked a nickel into the clay just to be safe. Now I'm waiting for the rain to stop. Maybe it'll fly sometime next week if things dry up.

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Alan R

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Oh one other mistake I made. After it was all finished the motor wouldnt fit. Grrr. Fork me. When i glued in the forks, I pushed too hard and one tine pushed all the way into the inside of the motor tube. I had to heat up a hot poker and melt it flat. Should have kept the motor in when I was gluing forks.
 

BABAR

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Maybe the old balloon trick?

Blow up a balloon the just under the size you need. Paper mache the outside, start smooth (not perfectly, but done try to get it clumpy until base layer dries. Then add your clumps and eyes. Let dry throughly. Pop the balloon.
Inside should still be round. Cut centering rings out of foam board (use a drill to cut center hole, and cut outside to size, easy to customize, plenty strong for 24 mm motors.
 

KenECoyote

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Nice "mash up"! 😆

Sorry about your launch lug woes...have you considered just making the top and bottom most centerings rings in each section have a hole appropriate for the launch rod and the ones in-between just bigger so it's easy to line the rod through? I did that for my custom break-apart Acme Spitfire.

The forks idea is awesome!! However are the forks you're using fragile? In my exp, forks like that are brittle and break easily, so they don't deal with landings well at all. I think I've come across some forks (usu white plastic) that are flexible and may impact forces better...just "food" for thought if the first launch results in broken forks. :p

Keep up the fantastic work!
 

neil_w

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The fork fins are genius. I don't know how much stability they provide, or if they'll survive a landing, but who cares? At some point the greatness of the idea outweighs the practical considerations. :)
 

KenECoyote

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The fork fins are genius. I don't know how much stability they provide, or if they'll survive a landing, but who cares? At some point the greatness of the idea outweighs the practical considerations. :)
Agreed Neil! :) That's why I said "The forks idea is awesome!!" and "...just "food" for thought if the first launch results in broken forks."

If it's built and good for a first launch, sometimes you gotta just say "fork it!" and reach for the sky! 😄
 

Alan R

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Sorry about your launch lug woes...have you considered just making the top and bottom most centerings rings in each section have a hole appropriate for the launch rod and the ones in-between just bigger so it's easy to line the rod through? I did that for my custom break-apart Acme Spitfire.
I did consider that, but I wasn't sure what the end result was going to be, so I opted for the full length lug. I saw your break-apart in the Spitfire gallery. Nice mod. Building this over ribs with the internal tube was very much like a Spitfire.

are the forks you're using fragile? In my exp, forks like that are brittle and break easily, so they don't deal with landings well at all. I think I've come across some forks (usu white plastic) that are flexible and may impact forces better...just "food" for thought if the first launch results in broken forks.
I know there are several types of forks, some are really weak and flexible - the cheap white ones, and some are extremely brittle - the clear acrylic ones.
I thought the cheap white ones wouldn't be strong enough, and I did have the fear of the acrylic ones breaking too easy.
These were free at my grocery store deli. They have ribs on the tines and handle for strength yet still have a bit of flexibility. Just perfect for the project.

I don't know how much stability they provide
I'm thinking they should work as well as Mars lander legs. They just need to create some balanced turbulence at the aft end. The handles are long enough that the total fin area is actually quite large
 

Alan R

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Where's the CP (Center of Potato)? 😁
I did make one of those cardboard cutout things the other day so I could do a spin test. It's about an inch below the fattest rib. My clay and nickel in the nose puts the CG very near the fattest rib.
 
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