MADCOW 4" FRENZY CARDBOARD ROCKET... A BUILD THREAD #1

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Maybe it was 'you', David, who mentioned the twisting thing!

'Twas I also in a PM.... minimalistic. Less connections to fail. I've never had twist and tape fail, ever. Just put a long wire on switch terminal and fish it through one of the vent holes BEFORE assembling av-bay. Easy-peasy. Just cut off the twisted portion after each flight.Never try to re-use.

Ca works just as well for coating. I just don't care for the stink, eye burn. I wait till I'm glueing something, then take the left over and thin it a bit. I'm cheap & hate wasting glue.
 
'Twas I also in a PM.... minimalistic. Less connections to fail. I've never had twist and tape fail, ever. Just put a long wire on switch terminal and fish it through one of the vent holes BEFORE assembling av-bay. Easy-peasy. Just cut off the twisted portion after each flight.Never try to re-use.

Ca works just as well for coating. I just don't care for the stink, eye burn. I wait till I'm glueing something, then take the left over and thin it a bit. I'm cheap & hate wasting glue.

I hear ya on the 'eye' burn thing. I approach CA like I approach strong onions that need to be chopped... "apprehensively!" I also don't much care for my fingers to be coated, thickly, and glass smooth after the fact, albeit. I've gotten used to that. I let my fingers cure for a while then 'sand' them with sandpaper. after that, it's not long before the oils in my skin take effect and I'm then able to start peeling what's left, from the CA skin off of my fingers. Yes, it's a pain in the butt...
 
I let my fingers cure for a while then 'sand' them with sandpaper. after that, it's not long before the oils in my skin take effect and I'm then able to start peeling what's left, from the CA skin off of my fingers. .

Hmmmm..... crack any safes lately????:lol:







Sorry couldn't resist....
 
Rotary Switches installed (dry fit). Plenty of room, looks good to go...

Rotary Switches Outside.jpgRotary Switches Inside.jpg
 
I filled the Frenzy up with everything that will be flying with it, except for a can of paint and a motor. I also added a bit extra weight to account for the "X-factor". Weight check. 6lbs.-1/4 ounce, stuffed.
Prior to 'stuffing' this bird, the empty airframe weighs 4.5lbs. even.

weight Check.jpg
 
Last edited:
The nosecone is really, really loose on my Frenzy. Should I use shear pins to hold it on after drogue deployment and things go nose down? I have shear pins for 25lb shearing, and also 35lb shearing.
 
The nosecone is really, really loose on my Frenzy. Should I use shear pins to hold it on after drogue deployment and things go nose down? I have shear pins for 25lb shearing, and also 35lb shearing.

If its loose enough that you cannot pick up the rocket by the nosecone without it coming loose, then either shear pins or friction fitting is a good idea. Unless you like long hikes of course.
 
Yes, it's pretty loose. I'd bet that I could blow it out, with my breath if I tried. I'll snug it up a bit with tape 'and' do the #2 shear pins, just to be safe. Not being familiar with the use of multiple shear pins, in rockets, please inform me. I know that one pin will shear @25lbs. Will three pins 'also' shear at the same 25lbs, or would it take 75lbs of pressure to do the job? I'm having a 'duh' moment here. :facepalm:
 
This should help........... from strength of materials web site. Actual testing done, what I use for reference.

Screen Shot 2016-07-24 at 5.41.26 PM.png


Save it for future use.


Could you post a pic of NC shoulder? I'm looking for ridges in it. Have a hint on how to snug up properly.
 
You're going to like this part :)

In cardboard it's best to back the tubing with some metal flashing to help shear the pin without tearing the cardboard.

Looks like a pretty long payload bay. Now it'll be full of stuff, but I tossed in 24" here just for giggles. I'd start ground testing around 1.5g and see where that takes you. I'd personally do 3 pins, but 2 will be sufficient.

28492159526_325db831ee.jpg
 
This should help........... from strength of materials web site. Actual testing done, what I use for reference.

View attachment 297671


Save it for future use.


Could you post a pic of NC shoulder? I'm looking for ridges in it. Have a hint on how to snug up properly.

Image saved, very helpful. Looks like 75psi is the target number, indeed!
Here's the nose cone shoulder. Yes "Thar be ridges!"

Nose Cone Ridges.jpg
 
You're going to like this part :)

In cardboard it's best to back the tubing with some metal flashing to help shear the pin without tearing the cardboard.

Looks like a pretty long payload bay. Now it'll be full of stuff, but I tossed in 24" here just for giggles. I'd start ground testing around 1.5g and see where that takes you. I'd personally do 3 pins, but 2 will be sufficient.

28492159526_325db831ee.jpg

The payload bay is 31" long, minus the 3" shoulder of the NC, minus another three inches for the av-bay shoulder. You was pretty darned close in your estimation.
I read somewhere about using copper to form shear edges. Copper? To heck with 'that'. A bit too soft for 'me'. "I'm using 'steel'!" LOL... This is banding material. I brought a couple of pieces home to kick around. They're about .010" thicker than the ridges on my NC, but that's okay. I intended to 'embed' them, anyway, to keep them from getting ripped away during deployment. Let's also see what BlackJack comes up with. Might be able to come up with something good, here!

Banding Material.jpg
 
Image saved, very helpful. Looks like 75psi is the target number, indeed!
Here's the nose cone shoulder. Yes "Thar be ridges!"

View attachment 297672

Just as I thought, same as one I have.
I have 2 options for you:

1. For Shear-Pins....Using 1/2 or 3/4 in. wide tape, wrap several layers in front of rear ridge, butting the tape up to ridge. Same for front ridge, depending on tape width, either in front or back of ridge. You will be a bit higher than ridge, as you are making a "seal". Not to tight a fit, just snug.

As mentioned using thin metal flashing imbedded, makes for clean cutting of pins, rather than tearing out your holes. Being cheap and lazy instead of going to Lowes...Hd..etc & looking for thin shim stock,[you may have some?] I just cut small strips from aluminum soda can & after my first wrap of tape, placed one/2/3, on tape & continue wrapping, so metal is in the tape layers. When finished you install into payload and drill pin holes through everything. Simple, neat, clean, easy.

2. I don't do that anymore. I use shear tape on cardboard rockets. After a number of flight, eventually your holes in airframe will get loose & must be fixed or rotate the NC and drill new ones. A 1/2 in. wide strip of masking tape has same holding power as a 2-256 pin. [as used my me anyhow]

On this 4in I used 2....not on the cone, LOL but to hold shoulder into airframe. I had a motor sooo long, it prevented the cone from seating. It raised eyebrows at the RSO table, but easily passed the "shake" test.

DSCN2969.jpg

Do your wraps around shoulder of nc to seal & snug fit & just 2 strips to hold cone on. Your cone is very light weight, so I doubt 3 pins or tape is needed. Not very pretty but works great & keeps the integrity of airframe intact.


So those are my 2 tips. There are many, many more ways to incorporate shear pins into cardboard, I'm sure some will pop in soon, on your thread.

Edit: the absolute best way, in my opinion, to prevent damage to airframe is to laminate a 1-2in wide strip of fiberglass around the top of airframe. More work...better results.
 
Last edited:
Just as I thought, same as one I have.
I have 2 options for you:

1. For Shear-Pins....Using 1/2 or 3/4 in. wide tape, wrap several layers in front of rear ridge, butting the tape up to ridge. Same for front ridge, depending on tape width, either in front or back of ridge. You will be a bit higher than ridge, as you are making a "seal". Not to tight a fit, just snug.

As mentioned using thin metal flashing imbedded, makes for clean cutting of pins, rather than tearing out your holes. Being cheap and lazy instead of going to Lowes...Hd..etc & looking for thin shim stock,[you may have some?] I just cut small strips from aluminum soda can & after my first wrap of tape, placed one/2/3, on tape & continue wrapping, so metal is in the tape layers. When finished you install into payload and drill pin holes through everything. Simple, neat, clean, easy.

2. I don't do that anymore. I use shear tape on cardboard rockets. After a number of flight, eventually your holes in airframe will get loose & must be fixed or rotate the NC and drill new ones. A 1/2 in. wide strip of masking tape has same holding power as a 2-256 pin. [as used my me anyhow]

On this 4in I used 2....not on the cone, LOL but to hold shoulder into airframe. I had a motor sooo long, it prevented the cone from seating. It raised eyebrows at the RSO table, but easily passed the "shake" test.

View attachment 297674

Do your wraps around shoulder of nc to seal & snug fit & just 2 strips to hold cone on. Your cone is very light weight, so I doubt 3 pins or tape is needed. Not very pretty but works great & keeps the integrity of airframe intact.


So those are my 2 tips. There are many, many more ways to incorporate shear pins into cardboard, I'm sure some will pop in soon, on your thread.

Edit: the absolute best way, in my opinion, to prevent damage to airframe is to laminate a 1-2in wide strip of fiberglass around the top of airframe. More work...better results.

Thanks AGAIN, Jim! Great advice, as 'always'!!!
 
This is a screw switch.... I like them, but finding them through a vent hole can be infuriating some days. Someone invented a funnel guide for them, but I can't seem to find the link at the moment.
21641468005_b085fe7fe6.jpg

I mount them to the inside of the coupler with screws, so the screw head is in the coupler wall and turnable from the outside....no fishing for them.
 
Just as I thought, same as one I have.
I have 2 options for you:

1. For Shear-Pins....Using 1/2 or 3/4 in. wide tape, wrap several layers in front of rear ridge, butting the tape up to ridge. Same for front ridge, depending on tape width, either in front or back of ridge. You will be a bit higher than ridge, as you are making a "seal". Not to tight a fit, just snug.

As mentioned using thin metal flashing imbedded, makes for clean cutting of pins, rather than tearing out your holes. Being cheap and lazy instead of going to Lowes...Hd..etc & looking for thin shim stock,[you may have some?] I just cut small strips from aluminum soda can & after my first wrap of tape, placed one/2/3, on tape & continue wrapping, so metal is in the tape layers. When finished you install into payload and drill pin holes through everything. Simple, neat, clean, easy.

2. I don't do that anymore. I use shear tape on cardboard rockets. After a number of flight, eventually your holes in airframe will get loose & must be fixed or rotate the NC and drill new ones. A 1/2 in. wide strip of masking tape has same holding power as a 2-256 pin. [as used my me anyhow]

On this 4in I used 2....not on the cone, LOL but to hold shoulder into airframe. I had a motor sooo long, it prevented the cone from seating. It raised eyebrows at the RSO table, but easily passed the "shake" test.

View attachment 297674

Do your wraps around shoulder of nc to seal & snug fit & just 2 strips to hold cone on. Your cone is very light weight, so I doubt 3 pins or tape is needed. Not very pretty but works great & keeps the integrity of airframe intact.


So those are my 2 tips. There are many, many more ways to incorporate shear pins into cardboard, I'm sure some will pop in soon, on your thread.

Edit: the absolute best way, in my opinion, to prevent damage to airframe is to laminate a 1-2in wide strip of fiberglass around the top of airframe. More work...better results.
My Frenzy has the same ridges on the nose cone and I too use the patented Crazy Jim Solution No.1. Tape is relatively cheap, can be purchased anywhere, and is easily adjusted as needed due to temperaure and humidity conditions.
 
My Frenzy has the same ridges on the nose cone and I too use the patented Crazy Jim Solution No.1. Tape is relatively cheap, can be purchased anywhere, and is easily adjusted as needed due to temperaure and humidity conditions.

I agree, completely. Will 'definitely' be incorporating tape! Was 'your' Frenzy NC silly loose, like mine?
 
To shear the pins, you need a hard surface opposing the hard surface of the nose cone. Position the pin holes in one of the ridges on the cone shoulder. The plastic won't deform, but the cardboard sure will tear, especially with repeated flights. Ask me how I know!

.005 brass shim stock or soda can aluminum 5 min epoxied into the inside of the cardboard body tube is more than sufficient. Banding material is nuclear overkill and hard to work with. Cut quarter sized patches, and use your dremel to sand out round 'pockets' or depressions on the inside of the body tube. 5 min epoxy in place, and sand smooth after a day or so of curing, then drill your holes. Perfect shear every time.

Use tape around the bottom of the cone shoulder to friction fit somewhat and form a good 'gas seal' for the ejection charge, and be prepared to adjust the number of wraps to suit temp/humidity conditions for the day.

YMMV
 
Last edited:
To shear the pins, you need a hard surface opposing the hard surface of the nose cone. Position the pin holes in one of the ridges on the cone shoulder. The plastic won't deform, but the cardboard sure will tear, especially with repeated flights. Ask me how I know!

.005 brass shim stock or soda can aluminum 5 min epoxied into the inside of the cardboard body tube is more than sufficient. Banding material is nuclear overkill and hard to work with. Cut quarter sized patches, and use your dremel to sand out round 'pockets' or depressions on the inside of the body tube. 5 min epoxy in place, and sand smooth after a day or so of curing, then drill your holes. Perfect shear every time.

Use tape around the bottom of the cone shoulder to friction fit somewhat and form a good 'gas seal' for the ejection charge, and be prepared to adjust the number of wraps to suit temp/humidity conditions for the day.

YMMV

Thanks Banzai88. Advice well taken!
 
While ground testing my ejection charges, I'll need igniters for the BP. Who should I buy them from and what will they actually be called? IE... proper terminology for igniter shopping? Motor ignitor sources would be good to know also...
 
E-Bay end caps taking on a light coating of epoxy. They already have a case of the 'fuzzies', as you can see, however. They won't get any 'fuzzier' than this! :)
Black Powder cannons and electrical terminal connections will be added next...

Sealing Av-bay End Caps.jpg
 
Last edited:
Last edited by a moderator:
Last edited by a moderator:
"Dang it all!"... I 'KNEW' better than to let my young 'Frenzy' share a private room with that cute little DX3... "LOOK WHAT HAPPENED!"... "Oh Nooo... "What will the neighbors say!" :facepalm:

Frenzy~DX3~V2.jpg
 
Back
Top