Baby Bertha Started

Well, Im starting to build my Baby Bertha. Going to be simple straight forward build. Trying to get some of my smaller simpler kits done.Good for flying in the school yard.Maybe Ill post some pics here and there of the build.

Scotty Dog said:

Well, Im starting to build my Baby Bertha. Going to be simple straight forward build. Trying to get some of my smaller simpler kits done.Good for flying in the school yard.Maybe Ill post some pics here and there of the build.

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A simple straight forward build may seem old hat to you. Some of the new people may enjoy seeing and reading about what you now think of as a simpler build.

You could make a 'show and tell' build thread. Show us what ya got. Could be fun to do!

bradycros said:

A simple straight forward build may seem old hat to you. Some of the new people may enjoy seeing and reading about what you now think of as a simpler build.

You could make a 'show and tell' build thread. Show us what ya got. Could be fun to do!

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True, I do forget that there are newbies here and they can learn/pic up something from any build thread. Guess Ill get the camera out.

Two recommended mods: Semroc BT-60 baffle (yes, there IS room, and no more wadding needed) and a spill hole in the 'chute for school yard flying. I lost my first one to a school roof . Second one was treed in the rain for a time but recovered and refurbished. Very reliable flyer. And of course there are the Goonies based on Baby Bertha kits (see https://towrowrow.tripod.com/excelsiorrocketry/id6.html)

Scotty Dog said:

Well, Im starting to build my Baby Bertha. Going to be simple straight forward build. Trying to get some of my smaller simpler kits done.Good for flying in the school yard.Maybe Ill post some pics here and there of the build.

Click to expand...

I bought a BB kit with a Hobby Lobby coupon and lost it in a drawer for a long time. When I found it, I was mourning the fact that the Fat Boy had gone OOP, so I chopped it up and made a Baby Fat Boy. It flies great on A8-3s, and recovers on a streamer (I had a boo-boo with the little red chute that comes with the kit). If I ever find my camera, I'll buy another and document the build too.

sooner.boomer said:

I bought a BB kit with a Hobby Lobby coupon and lost it in a drawer for a long time. When I found it, I was mourning the fact that the Fat Boy had gone OOP, so I chopped it up and made a Baby Fat Boy. It flies great on A8-3s, and recovers on a streamer (I had a boo-boo with the little red chute that comes with the kit). If I ever find my camera, I'll buy another and document the build too.

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Baby Fat Boy..I like that.

BEC said:

Two recommended mods: Semroc BT-60 baffle (yes, there IS room, and no more wadding needed) and a spill hole in the 'chute for school yard flying. I lost my first one to a school roof . Second one was treed in the rain for a time but recovered and refurbished. Very reliable flyer. And of course there are the Goonies based on Baby Bertha kits (see https://towrowrow.tripod.com/excelsiorrocketry/id6.html)

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Good idea.Im going to put baffles in a lot more of my builds,say BT50 and up and go with Kevlar off of the MMT on the smaller ones.All my BT50 rockets and smaller that I built when I first got back (BAR) have the glue tab and elastic shock cords.What a pain triyng to stuff a chute in them. Hey, Im learning......

sooner.boomer said:

I bought a BB kit with a Hobby Lobby coupon and lost it in a drawer for a long time. When I found it, I was mourning the fact that the Fat Boy had gone OOP, so I chopped it up and made a Baby Fat Boy. It flies great on A8-3s, and recovers on a streamer (I had a boo-boo with the little red chute that comes with the kit). If I ever find my camera, I'll buy another and document the build too.

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I did a Baby Fat Boy from BT-60 a dozen or so years ago. Mine had a 13mm mount and a 6inch chute. It was a fun little rocket before it got crushed.

Step by step "Show and Tell" as asked by bradycross .FnF the fins.(Guess I like sanding,havent done the label paper thing on fins)1st pic,Most important when building for me,cup of coffee.2ncd pic,Got the CR cut out,took an empty motor casing with some paper wrapped around it and sanded the nubs off inside of CRs and this loosened them up some.As you can see,motor tube is out of round.3rd pic,marked out the lines for the CR,mylar Retainer Ring and line for engine hook.4th pic,This is to show that I used the retainer to mark a line around the motor tube where the aft CR goes.5th pic, I used empty motor tube and engine block to support motor tube when cutting slot for engine hook.

1st pic, got the engine hook on motor tube (I drew a line on tube to go by to keep it in line with tube) Glued mylar ring on and I like to put some CA on fore end also.Motor block in fore end.Then I used the line I drew around tube (as illustrated in upper post) to line up the aft CR and put a couple drops of CA on it.This is just how I like to do it. I know the CR is square/straight with the tube. Same with fore CR.2cnd pic, CR fillets and youll notice I have the empty motor tube in cuz the tube was not round when I started.This way,when the fillets dry,I know the tube is round and a motor will go in it. 3rd pic,laying out the fin and LL lines.4th pic Lines drawn and I like to put a small mark/line on inside of tube.I like to this and you will see why later.Oh-Ya.I also sanded/roughed up the outside of main tube with some 800 grit paper.This is to help the primer and glued on fins adhere better.

Hi ScottyDog,
I'm enjoying the build thread, thanks for taking the time to do it.

Question - are the Baby Bertha fins the same size as the fins on a full size Big Bertha?

If they are, what would stop someone from buying a Baby Bertha kit for around $12.00 then add a 18" length of BT-60 to convert the Baby Bertha to a standard Big Bertha?

It 'd be a big savings when the standard Big Bertha can run over $24.99 retail!
That's $13.00 more for 10 inches of tubing!

Just a thought. Proceed!

hcmbanjo said:

Hi ScottyDog,
I'm enjoying the build thread, thanks for taking the time to do it.

Question - are the Baby Bertha fins the same size as the fins on a full size Big Bertha?

If they are, what would stop someone from buying a Baby Bertha kit for around $12.00 then add a 18" length of BT-60 to convert the Baby Bertha to a standard Big Bertha?

It 'd be a big savings when the standard Big Bertha can run over $24.99 retail!
That's $13.00 more for 10 inches of tubing!

Just a thought. Proceed!

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Dont know.Looks like they are,looking at Dans build of the BIG Bertha.Also think there is about 6-8 inches more of motor tube in th Big Bertha.

hcmbanjo said:

Hi ScottyDog,
I'm enjoying the build thread, thanks for taking the time to do it.

Question - are the Baby Bertha fins the same size as the fins on a full size Big Bertha?

If they are, what would stop someone from buying a Baby Bertha kit for around $12.00 then add a 18" length of BT-60 to convert the Baby Bertha to a standard Big Bertha?
It 'd be a big savings when the standard Big Bertha can run over $24.99 retail!
That's $13.00 more for 10 inches of tubing!
Just a thought. Proceed!

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www.semroc.com has 18" of BT-60 availaible for $3.10 and 18" of BT-20 (18 mm motor tube) for$1.55

www.balsamachining.com has 34" of BT-60 available for $3.35 and 34" of BT 20 for $1.75


The build is going well so far scottydog.

Scotty Dog said:

Dont know.Looks like they are,looking at Dans build of the BIG Bertha.Also think there is about 6-8 inches more of motor tube in th Big Bertha.

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Whoops, it looks like the newer Bertha's have the longer motor mount tube.
I was looking at the original Bertha plans at:
https://www.oldrocketplans.com/estes/estK-23/estK-23.htm

They show the older standard BT-20J at 2 3/4" long.

hcmbanjo said:

Whoops, it looks like the newer Bertha's have the longer motor mount tube.
I was looking at the original Bertha plans at:
https://www.oldrocketplans.com/estes/estK-23/estK-23.htm

They show the older standard BT-20J at 2 3/4" long.

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You would still be ahead of the game.But, then of course, there is the decal issue.

Scotty Dog said:

Dont know.Looks like they are,looking at Dans build of the BIG Bertha.Also think there is about 6-8 inches more of motor tube in th Big Bertha.

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If anyone is interested and cutting a tube to size doesn't work for you, www.semroc.com/Store/Products/BodyTubes.asp has an 8" BT-20 available for $1.05 or a 6" BT-20 for $0.90

I have both a Baby Bertha and a Big Bertha. Baby Bertha's fins are slightly smaller. Unless you have a spare 18" section of BT-60 lying around, the process of turning a Baby Bertha to a Big Bertha is pretty pointless, even if they did have the same fins. You can clone yourself 2 Big Berthas if you spend around $18.

OK,where do I start. Well, for one, I didnt work on it at all during the day.
Woke up once at 3:30 am ready to go,until I see it was 3:30am. I went back to bed and was woken up at 5:15 am by the dog.Guess he thought I had to work today.
I had things to do today but didnt need to be up that early.So I got on TRF and did some surfing.
Well,around 8:00 am I took the dog and we went for our coffee and treat ride. Stopped and got the mail and came home.
I had an 11:00 am appointment for my massage.And I also needed to get a hair cut.
Well, before I headed out I also needed to shower and trim the beard as I was starting to look like Grizzle Adams.Not that thats a bad thing.
Anywhoo, short of the long, after I did what I had to do I got home and took a loooooong nap.
Wife came home from work,we chilled out together for awhile and then had supper.After that I figured I would do some work on the BB.

1st,2cnd and 3rd pics,Measured out for placement of LL,also finished fillets on MMT.Glued on the LL
The instructions call for doing this step(LL) last.I did it now cuz I would not have room to use the guide to set it straight with the fins on.

4th and 5th pics, I dont have a small sanding block.So I cut pieces of sand paper about a 1/2 wider than my metal rule and wrap them on that.

You also will see I have the fins on some instruction.The reason for this is 2 things.
One reason is my table edge sticks up just a little above my cutting board.Other reason is,Back in the day,everytime I would sand fins it seemed not mater how carefull I was,I was getting dings/dents in them.
Well, I figured it out and found that it was caused by glue dots on my cutting board.So, now I use the paper under them when sanding

These pics are to show the importance of keeping things(fins) square when sanding them in a bunch and holding them perpendicular to the surface you are sanding them on

1st pic,Shows my fins with bottom edge against my metal rule which is running along line on my board.
You also see the fins are running sqaure off of the rule by the lines on the board. And you can see the corners are running square across the 4 stacked fins.

Now,in 2cnd pic, it looks like these fins look ok.Edges smooth and same size.

In 3rd pic, (this is a little extreme for show) you can see that the edges are on an angle and the corners are not running square across fins.

4th pic shows that the fins where not lined up square with each other and not held perpendicular to the sanding surface.Again this is a little extreme and I did it this way to show the affect.When your stacking and sanding 4 fins at once it can make a big differents on how they come out

ScottyDogs home made fin alignment guide.

1st pic,Bt60 coupler slid in main tube to transfer center lines of fins onto coupler. Went to other side (180 degrees) and did the same.

2cnd pic, I cut to pieces of balsa straight edges. Then took a couple scrap pieces of fin material and put those between staright edges.Lined up the center lines on coupler with the scrap pieces and then CAed the coupler to the straight edges.

3rd pics shows coupler and straiaght edges in main BT.

4th pic shows 2 fins glued on with guide in place.

5th pic, shows 2cnd pair of fins glued on with guide in place.

And for tonight.......

Awesome build Scotty Dog, great techniques!

Your work surface is way too neat!

Good job on the bird.

Not meaning to hijack your thread, but I found my camera. Beautiful day this morning, so we launched the Baby Fat Boy. Pic of it on the pad. We launch in a big parking lot - this is why fin tips are scuffed. I'll try to get a "fresh" kit this week and document build.

Was up early again.Lucky we got only couple inches of snow.
So,I did some glue fillets on the fins.No pics.
Then I went for my coffee run with the dog.
I got home and had a message on machine.They needed me at work cuz they where getting complaints of the water quality of the swimming pools.Im a Certified Pool Operator. I usual dont take care of the pools.They got another guy doing it.So, I went down and tested the water and it was fine.They have been having trouble for awhile with the air exchange system and I told them thats what was causing the eye burn and heavy smell of chlorine.Took about 4 hours out of my day between ride down,being there and ride home.
Anywhoo-I got the rest of glue fillets done. Let them dry and then put some FnF over the glue fillets. Set the rocket in front of heater on porch to push the dry time.
Sanded them down and put the primer to it.Came out OK. Ill let it be for tonight and do the fine sanding and check it over tomrrow night.

Is that a copper pipe coupled into the BB or another BT-60 painted copper coupled into the BB?

Your making very good progress.

bradycros said:

Is that a copper pipe coupled into the BB or another BT-60 painted copper coupled into the BB?

Your making very good progress.

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Its the end of a BT painted copper with a 3/4 gold stripe (cant see it cuz of primer)on top with about a 3/16 black stripe between them. This was a test to see how it would look on my Little Bucky .....that still isnt finished.

Something that just occured to me from rereading post #9 - have you tried slathering on the fill'n'finish BEFORE cutting the fins out of the sheet? Doing it while all the fins are still in the sheet would make sanding so much easier. I usually do this after they're glued on the body tube, just before primer/paint. And of course, this is the most difficult way to do it...

sooner.boomer said:

Something that just occured to me from rereading post #9 - have you tried slathering on the fill'n'finish BEFORE cutting the fins out of the sheet? Doing it while all the fins are still in the sheet would make sanding so much easier. I usually do this after they're glued on the body tube, just before primer/paint. And of course, this is the most difficult way to do it...

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Depends,Ive done it both ways.The last one I built "Snipe Hunter" I FnF them before breaking them out. https://www.rocketryforum.com/showthread.php?t=27672. By the way,your Baby Fat Boy looks like its scun its knees a few times.Maybe you should let the Baby play in the grass. Still,it looks cool

I'v found that plastic nose cones always have mold lines on them.

How do you get rid of the mold lines so ya can get a nice smooth paint job on the cone?

bradycros said:

I'v found that plastic nose cones always have mold lines on them.

How do you get rid of the mold lines so ya can get a nice smooth paint job on the cone?

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I use fine "sanding sponges" and "wet sand" under the kitchen tap.