Cosmic Interceptor Downscale

[johnnycarlos]

This is my very first scratch build, and frankly, I don't know what I'm doing. Suggestions appreciated.

The things that make me wonder are: I haven't read a book on rocketry yet(I certainly intend to and will get around to it). I understand that CP and CG are things to work out. But I'm not really fond of spending hours learning software. I'm on a computer all day and that's the last thing I want to do when I get home.

Gotta start somewhere though, so start small. Bought a handful of the Fletchers on clearance and that gave me the idea of using those parts to build a Cosmic Interceptor small scale. This is where I'm headed...

 

[Cabernut]

I like this idea. Daunting task if you are going to downscale every single part. With a ruler and careful measuring, I'm sure it wouldn't be too difficult to get a scaled-down template made of the fins. The faux intake and engine mount vanes would be a whole other story.

 

[Charles_McG]

I love downscales!

My general observation is that downscales tend to be tail heavy compared to the original. I believe it has to do with tubing/fin/glue/motor mass not scaling in proportion with the silhouette. So Cg moves, but not Cp. Or at least it moves more.

You've got the original. So just make the downscale balance (sideways on a finger/pencil/etc) at the same point along the body as the original. Motors in both, for the right comparison.

 

[johnnycarlos]

I like this idea. Daunting task if you are going to downscale every single part. With a ruler and careful measuring, I'm sure it wouldn't be too difficult to get a scaled-down template made of the fins. The faux intake and engine mount vanes would be a whole other story.

Oh my, yea that would be daunting. I don't intend to replicate every little part, nor be terribly precise about it. This is my very first attempt at doing something outside of a kit. I just want to scratch build something other than the "simple rocket" and that flies reasonably ok. Perhaps I've written a misleading title then.

I will add an air scoop(probably without the inner vanes). I'll pass on the engine mount vanes too since the real model engine is an inner tube and the body tube I'm using is the same diameter as the mini engine itself. I might add some decorative balsa slivers to the outside.

EDIT: Correction, the Fletcher has an inner tube engine mount as well, but still, I will skip replicating the Interceptor's engine mount as it is very intricate.

 

[johnnycarlos]

You've got the original. So just make the downscale balance (sideways on a finger/pencil/etc) at the same point along the body as the original. Motors in both, for the right comparison.

Ah! Great idea. I hadn't thought of that(slaps forehead)

 

[Cabernut]

Please post your progress. I don't think many have tried this yet.

 

[johnnycarlos]

- Added a faux intake scoop. I test fit a random sliver of balsa, it might work as vanes. Won't be exact but perhaps better than an empty inlet.
- Some wood filler at the seam.
- Wing support rail

 

[johnnycarlos]

Fins added. At this point I'm ready for a test launch(tomorrow). If it doesn't fly right, no sense going further.

 

[Charles_McG]

It will fly great. Just epoxy a sinker or two into the nose cone.

 

[GlenP]

you could add a canopy from cardstock to the nose ...

https://www.rocketryforum.com/showt...king-a-cardstock-canopy&p=1287086#post1287086

 

[johnnycarlos]

you could add a canopy from cardstock to the nose ...

https://www.rocketryforum.com/showt...king-a-cardstock-canopy&p=1287086#post1287086

Thanks GlenP! I'll check it out.

 

[johnnycarlos]

Great test flight! The chute did not unfurl, but I'm satisfied with how it flew. My first scratch build. Achievement unlocked.

[video=youtube;flK6u1ZBSc0]https://www.youtube.com/watch?v=flK6u1ZBSc0&feature=youtu.be[/video]

 

[Charles_McG]

What size chute?

 

[johnnycarlos]

What size chute?

6 inch plastic. Looks like the wadding entangled with the chute strings.

 

[Charles_McG]

I've never gotten those black and white checkered chutes to open. I use a streamer instead.

 

[Cabernut]

Nice flight. Up and out!

 

[neil_w]

I use a steamer instead.

Do tell.

 

[Charles_McG]

Do tell.

Did I miss something to get a wink emoticon? Have I posted a bunch of photos with streamers hanging out?

I tried a 6" chute again last week for my mini Mercury Atlas. I couldn't get it to open up, waving it around the living room. Maybe a tiny chute needs a thinner material? I have a space blanket I could try.

 

[johnnycarlos]

Did I miss something to get a wink emoticon? Have I posted a bunch of photos with streamers hanging out?

Gonna guess it was the typo misspelling as "steamer".

 

[Charles_McG]

Ah, I see it now. That would do it.