"Scaredy Cat" - A 54mm Minimum Diameter Project

[UPscaler]

I took a few components from a Madcow Tomach 2.2 I bought and turned it into what I hope will be my first project to hit 20,000 feet.

A nice, simple minimum diameter 54 with no tip to tip reinforcement, just surface bonded with big fillets.

This rocket will fly at Airfest in a few weeks, likely on an Aerotech K455NW. That is, unless someone has a K250 they want to sell at Airfest, since it's out of stock everywhere.

I'll have a video up shortly, but here's some pictures to get the party started.


Braden

 

[UPscaler]

Here's the video of day one construction!




Edit: Link fixed!


Braden

 

[Fattbank64]

Here's the video of day one construction!


Braden

Link?

 

[UPscaler]

Link?

Whoops, I mistakenly uploaded to the wrong channel and thought I had removed this reply. I'll have it open again shortly.


Braden

 

[boomtube-mk2]

"A black cat crossing your path signifies that the animal is going somewhere".

-Groucho Marx-

In the case of "Scaredy Cat", the animal will be crossing your path very, vey fast.

 

[UPscaler]

"A black cat crossing your path signifies that the animal is going somewhere".

-Groucho Marx-

In the case of "Scaredy Cat", the animal will be crossing your path very, vey fast.

That's the idea! Initial plan was an L1000, but it's looking like that would take a decent amount of luck in terms of ideal launch conditions to hit 20,000. It was simming to Mach 2.5 in RASAero. However, the K455 and K250 both sim under Mach 2.

Still plenty quick!

Braden

 

[UPscaler]

Last set of fillets is on and found a new friend. Lucky for me it was while the fillets were still wet and hadn't settled and smoothed out entirely yet.


Braden

 

[UPscaler]

Well this is a total disaster!

The last two sets of fillets aren't curing properly and instead turned into rubber. Interestingly enough, another rocket I did two sets of fillets on at the exact same time as these cured perfectly fine and have been sanded successfully.

Gotta think about how I'll be fixing this one.

Braden

 

[Cameron Anderson]

Well this is a total disaster!

The last two sets of fillets aren't curing properly and instead turned into rubber. Interestingly enough, another rocket I did two sets of fillets on at the exact same time as these cured perfectly fine and have been sanded successfully.

Gotta think about how I'll be fixing this one.

Braden

Old/contaminated epoxy?

 

[UPscaler]

Old/contaminated epoxy?

To some extent, somehow. As I said, I immediately followed both sets of these fillets with some one another rocket using the same epoxy and filler (and even the same mixing cup on the last batch). The first set of fillets is fine and the only variable changed among all these good ones and the two bad ones is using a single pump of epoxy. All the good sets had two pumps. No clue.

So enjoy some scraping as I painstakingly pulled all the West System jelly off the airframe and fins and meticulously re-prepped for take two.

Final image is a set of fillets from the other rocket that I made at the same time with the same epoxy.


Weird.


Braden

 

[JimJarvis50]

I use pumps to dispense epoxy, but I don't relay on them delivering the correct amount of epoxy. I go by weight.

Jim

 

[UPscaler]

I use pumps to dispense epoxy, but I don't relay on them delivering the correct amount of epoxy. I go by weight.

Jim

I do have a .01 scale I should probably be using.

Braden

 

[OverTheTop]

I do have a .01 scale I should probably be using.

Measure the hardener first since it is easier to get a more exact weight later when adding the resin (larger quantity).

Here is a Tomach I built a few years back. I think I got about 21500' on an L640DT:
https://forum.ausrocketry.com/viewtopic.php?f=6&t=4758&p=58844

 

[DMehalko]

I use pumps to dispense epoxy, but I don't relay on them delivering the correct amount of epoxy. I go by weight.

Jim

THIS x 1000%

ive had pumps cavitate, and once that happens the batch is trash imo

I do have a .01 scale I should probably be using.

Braden

This…. Haha

Measure the hardener first since it is easier to get a more exact weight later when adding the resin (larger quantity).

Here is a Tomach I built a few years back. I think I got about 21500' on an L640DT:
https://forum.ausrocketry.com/viewtopic.php?f=6&t=4758&p=58844

I disagree, easier (in my opinion) to pick the amount of resin you want for the project, visually or by weight, then in the case of the west system, just divide your resin weight by 5 then add that to the original resin weight. There is your perfect target weight to hit as you add your hardener.

 

[OverTheTop]

I disagree, easier (in my opinion) to pick the amount of resin you want for the project, visually or by weight, then in the case of the west system, just divide your resin weight by 5 then add that to the original resin weight. There is your perfect target weight to hit as you add your hardener.

To each their own. I pour the required approximate amount of hardener into a container. For small batches it might only be 0.2g or so. Then multiply the weight by 10 and halve it (easier to do the mental arithmetic that way). The the scale is tared and the required amount of resin added. That's my method. For small quantities you need to be very careful about mixing. I usually mix, wait ten minutes and mix again before application in that case.

 

[UPscaler]

THIS x 1000%

ive had pumps cavitate, and once that happens the batch is trash imo



This…. Haha




I disagree, easier (in my opinion) to pick the amount of resin you want for the project, visually or by weight, then in the case of the west system, just divide your resin weight by 5 then add that to the original resin weight. There is your perfect target weight to hit as you add your hardener.

Using the allegedly correctly dispensing pumps would make it easy enough to keep my general rule of thumb (IE, this many pumps for these fillets etc) while using a scale to double-check the ratios.

I'll definitely be paying more attention for these next sets of fillets.

Braden

 

[boomtube-mk2]

Is there any possibility that there was some kind of contaminate on the fins and or airframe-tube?

 

[Tim51]

Is there any possibility that there was some kind of contaminate on the fins and or airframe-tube?

See video in post #2. The OP was pretty meticulous - parts washed in soapy water, denatured alcohol rub down, sanded. He's also wearing nitriles for most of it. Seems more likely it's either a bad batch of hardener (I had that happen to me once where Devcon hardener had turned sort of sugary, leaving fillets that wouldn't cure) or a mixing ratio error as discussed. A pig when it happens, but as this thread shows, it can happen to the best of us

 

[tfish]

Is that the "west systems " epoxy shown in the video? It's been 25 years since I've used any west systems. Is it always white like that or did you add some tint?
Looking at the fly photo.. leads me to believe..your epoxy is setting up with millions of tiny bubbles..which might limit your mach 2 hopes.

Tony

 

[UPscaler]

Is that the "west systems " epoxy shown in the video? It's been 25 years since I've used any west systems. Is it always white like that or did you add some tint?
Looking at the fly photo.. leads me to believe..your epoxy is setting up with millions of tiny bubbles..which might limit your mach 2 hopes.

Tony

It's with added Colloidal Silica filler.

In my experience with West Systems and this filler, the epoxy gassed out and the bubbles come to the surface. After sanding they're pretty solid under that top layer. I do have some proline 4500 around, too, but it's pretty old.

Here is a set of West Systems fillets after sanding them.


Braden

 

[tfish]

Just looks weird.
Tony

 

[UPscaler]

Just looks weird.View attachment 477103
Tony

It's possible the perceived bubbles are bits of the filler itself settling in toward the center of the filler.

I can't say for sure, but I do trust you know a good bit more about this than I do and I am a little gunshy of trying to use West again, so I'm considering switching to Proline.


Braden

 

[Donnager]

Just looks weird.View attachment 477103
Tony

For me as well. But for a different reason. My experiences with bugs in paint is that they tend to die in the paint, slowly.

I can usually find a 3" track before the finally deceased insect. Fortunately, they sand.

 

[UPscaler]

Recovery effort went fairly smoothly!

No pun intended. We're back on track now.

Motor has officially been decided to be a CTI K300. Relatively tame in terms of speed with solid RASaero predicted altitudes. So long as it survives this flight, we can turn the heat up a bit at a later date.

Braden

 

[UPscaler]

Here's a look at the recovery effort for getting all the rogue epoxy off and starting over.



Braden

 

[UPscaler]

And we're off! In primer it weighs a hair over 1.6 pounds. Going to wet sand and paint, then it's down to silly semantics like recovery

Any guesses on the paint scheme?

Braden

 

[Tobor]

And we're off! In primer it weighs a hair over 1.6 pounds. Going to wet sand and paint, then it's down to silly semantics like recovery

Any guesses on the paint scheme?

Braden

Hmmmm....

Well, all "Scaredy Cats" are yellow by nature...

 

[rfjustin]

Make sure to glue the forward bulkhead in and slather the outside of the top 6" of the liner and bulkhead with a LOT of grease on that K-300...

 

[T34zac]

Looking forward to see how this goes. I’m also working on a k300 min diameter rocket. Good luck with your flight!

 

[UPscaler]

Looking forward to see how this goes. I’m also working on a k300 min diameter rocket. Good luck with your flight!

Thank you!

Make sure to glue the forward bulkhead in and slather the outside of the top 6" of the liner and bulkhead with a LOT of grease on that K-300...

I appreciate the heads up on this one!

Braden