BT-60 and a Bertha NC

Visited a new hobby shop with some cool dudes running it and picked up a baby Bertha because I wanted to make another.

I have some BT-55 / couplers around and used it along with some light balsa ply.


IMAG3323 by beerorkid, on Flickr

Picked up a baby Bertha for the Nosecone and the fins. After looking at the fins, I realized that they were not the same at all, much smaller. Looked up a couple Bertha fin paterns and decided to just scratch build a rocket with the Bertha Nosecone.

Went with Krusty Big Daddy fins on a 3 way config. Love it Krusty and thanks.


IMAG3324 by beerorkid, on Flickr

24mm retainer installed from www.rocketarium.com . Many gray primer and sanded down to a deep purple. Will rock it with tayma paint for a finish. Will be used often.


IMAG3330 by beerorkid, on Flickr

Through body ply fins. 24MM retainer installed. Kevlar on the motor tube. Rail buttons will be installed.

I made basla ply fins and centering rings. Also put a www.rocketarium.com 24MM retainer on it. With the through fins and retainer she should fly good often. I plan on making it a workhorse of the fleet.


IMAG3331 by beerorkid, on Flickr

Tamaya sparkly purple FTW

She will work great on reloads.


IMAG3334 by beerorkid, on Flickr

A darn sturdy flier is her destiny.

EDIT: claimed BT-55 when it was BT-60... thanks Rex

minor quibble hardly worth mentioning...the bertha has a bt60 for an airframe. nice paint job.
rex

Rex R said:

minor quibble hardly worth mentioning...the bertha has a bt60 for an airframe. nice paint job.
rex

Click to expand...

Nice catch. I was pretty much guessing. Adjusted the title.


IMAG3329 by beerorkid, on Flickr


IMAG3338 by beerorkid, on Flickr


IMAG3341 by beerorkid, on Flickr


IMAG3342 by beerorkid, on Flickr

I cannot wait to fly her. Hoping tomorrow after work.

hmm, now we just have to get you to start ordering parts from semroc...like the bnc-60k https://www.semroc.com/Store/Scripts/prodView.asp?idproduct=2735 and really give this bird a ride . be advised that this one will likely weathervane readily so don't try to angle it into the wind over much. good luck and straight smoke.
rex

Very cool & great use of the fins
The fleet is really coming along!!

Krusty

Decided against a fancy paint scheme and did the future polish on it last night. Sometime after the 2nd coat it fell from its cheap masking tape hook and fell about 4 feet right on its nose that was also masking taped. Jammed the NC into the BT pretty good and the future glued it stuck good. Was able to free it and chopped an inch off the BT for a fix. Lawn darted before it even flew >.<

BeerorKid said:

Decided against a fancy paint scheme and did the future polish on it last night. Sometime after the 2nd coat it fell from its cheap masking tape hook and fell about 4 feet right on its nose that was also masking taped. Jammed the NC into the BT pretty good and the future glued it stuck good. Was able to free it and chopped an inch off the BT for a fix. Lawn darted before it even flew >.<

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Dude that sucks but you're not alone! I had a completely finished TLP 'Type 30' sitting on my shelf waiting for a launch day. My cat decided to jump up and push it out the way. One fin completely smashed off, another broken in half along the grain. The tip of the nose cone smashed in (TLP kits often have a paper tip on the nose to change its shape) and the body tube got a kink about 1/2 way along. The only way it could have been more damaged was if I was to put it on the floor and jump on it myself!! argh!!!

Krusty

Ouch man. Darn cats. My livestock has yet to ruin a rocket.
* nocks on balsa *

Looking forward to building up a TLP ALARM. Their kits are pretty nifty.

purptha1 by beerorkid, on Flickr

Here is my best attempt at a sim

https://beerorkid.com/rockets/Purpertha.ork

It seems the CP and CG are darn close.

Rex says it will weathervane bad. What can I do to it to make it more stable?

It weighs 4.25 OZ with the retainer and nothing else.

keep in mind that I didn't know (still don't for sure) where the loaded cg is, all I had to go on were those large fins . what you need to do before anything else is Don't Panic. right, load that bird as though you were doing a flight prep including a motor(that F24 you have in the bag will work nicely) and find out just where the cg really is, then we can address any possible stability issues(your RSO will/should check as well, it is part of the job). IF the cg is where your sim says it is, then 5g of modeling clay in the nose should fix it.
rex

* remains calm *

While laying in bed I thought about the term weathervane a bit and it made sense with the large fins. Looked it up weathercocking this morning and it now makes much more sense. Long body and large swept back fins would make an over stable rocket. Big Bertha, which this one is sorta modeled after, is a good example.

I am on chapter 4 of The Handbook of Model Rocketry by Henry Stien. The bit about the rocket eating trees was darn funny. Made it through Model Rocket Design and Construction - Timothy S. Van Milligan. Slowly grasping it all. Will load it up tonight and see exactly where that CG is.

Thanks again for the tips Rex R.

and rockets that leave the pad slowly like a big daddy on a D12, a bertha on an E20 has very little weathercocking .
rex

Over lunch I threw the F24 and a chute in there and found the CG and overrode the CG to the correct spot. Moved the CG up a decent amount.

New ork file: https://beerorkid.com/rockets/Purpertha2.ork





Rail buttons and a nice long rail should get it going pretty straight. Hoping to launch tomorrow 10 MPH wind and 60 degrees F.

Might need to add a centering ring made from a cereal box up near the top to prevent your chute from sliding back on lift off & screwing with the cg... Even just a strip glued cross way will work, anything to keep the chute in the forward part of the BT

T-Rex said:

Might need to add a centering ring made from a cereal box up near the top to prevent your chute from sliding back on lift off & screwing with the cg... Even just a strip glued cross way will work, anything to keep the chute in the forward part of the BT

Click to expand...

What a great tip. Will do for sure. Well after the flight tomorrow. She is fully loaded and doing an E18-4W.

[video=youtube;RdSrmBC7VUo]https://www.youtube.com/watch?v=RdSrmBC7VUo[/video]

And I lost her on her first flight. Was a great flight though.

I saw the chute open and it was way too big of a chute. The wind died down at launch, but picked up insane right after. I scoured acres of corn field for it, but no luck. Sun in my eyes blinded me.

NOW TO MAKE ANOTHER

:eyepop: I never thought of that! Thanks!

T-Rex said:

Might need to add a centering ring made from a cereal box up near the top to prevent your chute from sliding back on lift off & screwing with the cg... Even just a strip glued cross way will work, anything to keep the chute in the forward part of the BT

Click to expand...

WOW what a great launch! Sounded like it exploded off the pad!! And it didn't seem to weathercock at all!

But major bummer about losing it

Krusty

$25 24MM case and a $14 motor retainer lost, but I totally broke 1000 feet I think for the first time. Good thing I forgot to put the altimeter in there.

Bummed.. yeah, but the build was fun and I wrote my info on it and "reward if found" so maybe one day I will get the parts back.

ffffft dink FWOOOOSH

BeerorKid said:

Bummed.. yeah, but the build was fun and I wrote my info on it and "reward if found" so maybe one day I will get the parts back.

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Local news reported an Ellis County Sheriff's vehicle was hit by a re-entering rocket...:wink: Rumor has it that it was retaliation over the recent NB-KS lawsuits over water.

SteveA said:

Local news reported an Ellis County Sheriff's vehicle was hit by a re-entering rocket...:wink: Rumor has it that it was retaliation over the recent NB-KS lawsuits over water.

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I happen to work in the legislature and they are currently on a bill about the republican river water usage.

I am so going to pee in that dumb river

BeerorKid said:

I am so going to pee in that dumb river

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HA! That's fine, I live upstream and south of the Republican. Go ahead and pee, it'll flow into Topeka and Lawrence.:grin::lol:

I will not pee in the river. It is frustrating working at a state legislature and that darn river is a fight every gosh darn year.

So I lost that one, but want to fly it again. I ordered more tubes, noses, balsa ply, RMS case, etc... Any suggestions on the rebuild? Thinking a better fin and a diff length. Will still be BT-60 with a 24mm motor mount.

I can go much longer and jam a stuffer tube in there. When tubes are that cheap I stock up. Got 6 sheets of light ply on the way. If anyone has a fin I should copy let me know.

Just looking for a light, strong, high flier on 24MM reloads. Will build it fast and easy paint once again. Not looking for a beautiful build, but a beast I can fly over and over.

well one could play with this design... this design calls for Depron fins and centering rings(papered) but should work fine with balsa and 1/16" cardboard. if memory serves you'll have to get the nose from semroc if you want to build per design.
rex
edit
design calls for a Bnc-60v but a Bnc-60k would well too .

View attachment depon rocket.ork

Rex R said:

well one could play with this design... this design calls for Depron fins and centering rings(papered) but should work fine with balsa and 1/16" cardboard. if memory serves you'll have to get the nose from semroc if you want to build per design.
rex
edit
design calls for a Bnc-60v but a Bnc-60k would well too .

Click to expand...

Ahhh cool. I see there is a bulkhead and coupler in there to eliminate the stuffer tube.... er wait. Two chutes? But it gives me ideas. I picked up some BT-60 baffles as well and will work them into it somehow.

It just seems so odd to work on the design before the build

BeerorKid said:

If anyone has a fin I should copy let me know.

Click to expand...

How about using 1/2 a CD? Don't use the CD itself, just as a template to cut your ply

Krusty

krusty said:

How about using 1/2 a CD? Don't use the CD itself, just as a template to cut your ply

Krusty

Click to expand...

Oh man that would be fun. I might accept that challenge actually.

The Lunar Eclipse from 3D rocketry just draws me to it. I have wondered how someone could put some sort of free spinning ring in the cutouts with slightly angled fins so it rotated. Sure it would drag some, but would be awesome sauce.

BeerorKid said:

Oh man that would be fun. I might accept that challenge actually.

The Lunar Eclipse from 3D rocketry just draws me to it. I have wondered how someone could put some sort of free spinning ring in the cutouts with slightly angled fins so it rotated. Sure it would drag some, but would be awesome sauce.

Click to expand...

That would look cool! I have an idea on how to do it and it won't be too hard!!! I'll do a diagram and explain later, I'm at work right now and have no access to drawing software... damn work!

Krusty

If just the fins I would try and recreate the 3D rocket style with swooping through fins. Thinking that is where I will go if I go down that road. Wife thought it sounded cool as well.

With some sort of rotating device I have graphite powder for lube. Bearings would be too much, but some sort of bushing would work. Some nylon rings on the outside tube maybe.

I really am not concerned with drag or height. I just want to launch 24mm reloads and still be able to see it at apogee. I am going a bit thinner than the Big Daddy kick I have been on and love the Berthas so much I think BT-60 is a fun size to play with now.

The depron one looks to be made to go really high. I know I said go high a bit ago, but I am a bit reluctant after losing that last one. It was mostly because I was more concerned about the vid instead of watching the rocket though >.<

If you have any ideas I would love to hear them. The baffle will be neat to add this time. Need to work those into my build I am guessing.

well one of the nice things about design software is that one can play 'what if' games with it . if you use a bertha nose, add a 31g payload, and leave the fin edges square the max altitude drops to 1500'(F39). note the payload section is borrowed from my cheese lofter...that was designed to go as high as possible w/ a 1 oz. payload and carry a 20-30' streamer, the simulations put it at 2000' on an E20 .