2 Stage Baby Bertha

[nomopbo]

It's still nekkid, but here it is. I was inspired by the SemRoc FireFly.

 

[nomopbo]

Here is the business end, 18 mm

 

[OKTurbo]

Kinda funky....

I like it!!

John

 

[eugenefl]

What's cool about this design is that the 1st stage will make the liftoff "draggy." I bet once that second stage ignites that BB will kick into turbo mode! Cool design.

 

[vsergeev]

Originally posted by nomopbo
It's still nekkid, but here it is. I was inspired by the SemRoc FireFly.

I think it looks awesome!

I just recently bought a baby bertha kit, but now I'm thinking I should have got two. Next time I go to the local rocket shop I'll grab another. I've already seen way too many cool baby bertha mods.

 

[AlexM]

Nicely done!

 

[phaar]

Very nice.

 

[karatekicker271]

SWEET!

 

[gerbs4me]

Awesome
you done a great job, lets see that thing in action

 

[powderburner]

you should probably add a balsa or spruce laminate with the added grain running spanwise at the main leading edge of the booster, or else laminate the booster fins with card-stock

the existing wood grain is running in a 'weak' direction and will probably snap at touchdown

nice design, looks like it will be a fun flier!

 

[cummins]

This is very cool looking. I wish I could come up with cool designs like this.

 

[astronboy]

Oh yes, I LOVE that versatile Baby Bertha kit. Although I am building 6 prototype Goonys right now, I have not staged it yet, but I guess that should be next.....

Nice job. My only question is... will the booster tumble,
or
lawndart?

Fred

 

[nomopbo]

Originally posted by powderburner
you should probably add a balsa or spruce laminate with the added grain running spanwise at the main leading edge of the booster, or else laminate the booster fins with card-stock

the existing wood grain is running in a 'weak' direction and will probably snap at touchdown

nice design, looks like it will be a fun flier!

Great Idea! I tried to think about the grain direction and make sure it didnt run parallel with the ground, but I see what you are saying.

 

[nomopbo]

Originally posted by astronboy
My only question is... will the booster tumble,
or
lawndart?

Fred

Good question, I was wondering this myself. I figured the only way to know for sure was GO FOR IT! (and build it strong enough to survive)
How to you figure this out before you build anyway

Thanks for all the good feedback! It was a fun build. I will let you know how it flies.

 

[astronboy]

Rocsim is pretty good for designing tumbling boosters. The two I have designed worked well.

Issue 96, and 97 of the Apogee newsletters covers this in great detail.

Here are the links to the PDF files:

https://www.apogeerockets.com/education/downloads/newsletter96.pdf

https://www.apogeerockets.com/education/downloads/newsletter97.pdf

and below is the Rocsim file of the booster I designed forthe Alpha.

Fred

 

[rocketdad0934]

looks great I like it my question is what does it weight at lift-off? the reason for the question is that I built a neat thing with the fat boy kit only to discover later that the c6-0 is only good for 4 oz and in the transfer the rocket layed over and land sharked into the next hill. may I suggest a 24mm d12-0 might save your wonderful creation. happy flying and many safe recoveries!!!!!

 

[nomopbo]

Another good point. This did cross my mind as I was building the booster to withstand a lawndart incase it didnt tumble! (thicker balsa and a bit of epoxy) (Also nose weight) I dont have a mail scale, so again my attitude was GO FOR IT! We will see come Wednesday.

All good questions, but I am impressed with how much I have learned since I had asked myself all of them. I wish I had a better answer other than "let's see what happens."

I will let you know Wednesday! Wish me luck!

 

[slim_t]

I would think that the Baby Bertha is light enough to be boosted by a C6. It is a good bit lighter than a Fat Boy, as long as the nose weight isn't too much. This is just my opinion though.
You could just get a cheap kitchen scale to weigh it with. They aren't as accurate as a postal scale, but close enough to predict what the rocket will do.

Oh, and there's nothing wrong with the "Go for it" attitude. I do that sometimes to. Some people refer to it as "Experimental", so I usually like to test these designs when I'm alone.

Great design by the way.

Tim

 

[astronboy]

I agree. I usually test fly new designs alone, even if I designed the rocket using Rocsim. The tough part is getting liftoff photos while launching alone!!

My only criticism, (in a firendly way) is that I believe that a booster should be as light as possible (esp if it might lawn dart in!!). I do not use epoxy on mine, as it adds so much weight. As long as you are not flying on a parking lot, the booster should be OK.

I am curious as to how this little guy flies. Please let us know..... and take some pictures!!!

Boy, that Baby Bertha is great kit-bashing fodder, huh?

Fred