Crushing Big Bertha...

[Kirk G]

Well, for my birthday, I was given a Big Bertha kit by another club member....I don't know if it's because it was extra or she knew that I had done the Baby Bertha earlier, or if it was because it was damaged and left over... but the point is it arrived via USPS special delivery bag, and there's some damage.

The places I spot trouble are:
The launch lug (soda straw) is kinked slightly in the middle, but essentially straight. (Boy, it's long.....)
The main body tube is crushed at one end...flattened so that there is a permanent crease. The tube is not round, not even a perfect oval, but ellipse shaped.
Halfway up the body tube, there's an impact crease, a slight dimple or crease about the size of your thumb, but doesn't affect the integrity of the tube structure.

So, I launched into the kit after reading it through, and I chose to position the crushed end of the tube at the bottom, where the motor mount would shore-up, and hold the tube back to a round shape. Had I placed it at the other end, I'm concerned that either the nosecone would be held too tightly by the friction of the crushed tube, or, that once ejected, the tube would somehow be less that a desirable shape for a descent. Anyway, I decided upon shoring the damaged end up with the centering rings and motor mount assembly.

As it turns out, I glued only around the rear ring, both inside and then a filet from the outside. I guess the Big Bertha body tube is too long to consider reaching all the way down into the tube to attempt to spread a ring of glue to hold the front centering ring. At least, I didn't see any instructions to do so, so the forward ring is held by the glue to the motor tube and the friction fit to the body tube.

I feathered the leading edge of the fins before sealing, but this time, I attempted something new: CA to hold the root edge against the sanded body tube, and I positioned the launch lug along the crease line where the tube was flattened. (In other words, none of the balsa wood fins align with the crease. they are spaced, straddling ,and parallel with that crease.) Did I mention that I used carpenter wood glue as the filet on the launch lug as well as the balsa fins? Well, I did. And most were done last night at 3 a.m. They dried 9 hours. And then I hit the launch lug again and hour before painting.


As I get to the end stages of construction, I've tied the shock cord onto the nose cone but now notice that it increases friction for the slip fit. And after gluing the anchor inside at more than 1 1/2 inch down the tube, I know it's not impacting that. As I consider tying on the parachute, I note that it's a pre-pack assembled chute from China, carefully folded and pressed. I'm debating just looping the shrouds around the nosecone to tie it on, but not disturbing the chute, since it's so carefully folded, much better than I could do. (What do you guys think of that idea, or am I shooting myself in the foot by not fluffing the chute out and powdering it with baby powder?) Or course then, I'd have to re-roll it.

Today, as we have 75 F and bright sunshine, I primed the rocket by brush with Gray Valspar primer paint and avoided the fillets, as I think they could continue to cure and dry a little more (to yellow tinted clear state).

This time, I tried a flat brush-on primer, and gave it all (except the fillets) a thin coating, figuring to spray paint the thing flat black like my Hyper-Bat and the Baby Bertha. But somebody showed me a picture of their bright gloss yellow Baby Bertha and now it's gotten me thinking that perhaps recovery and sighting up in the air might be better with something brighter. The parachute is a black, blue, white pre-printed add for Estes Rockets...and not particularly eye catching like red or orange.

Any suggestions would be welcome, as I'm letting the primer dry this afternoon before looking at spraying a finish coat or two tomorrow.

 

[TopRamen]

That's pretty interesting that you were able to forego the Glue on the Inner Centering Ring. 99% of folks would just glue it anyway, regardless of the Instructions. Hopefully it holds up for you, but you may want to inspect the integrity of the Glue Line on that one CR, as it will undoubtably be only half as strong as it would be if the other Ring was solidly emplaced.
You should throw away the Instructions as "Step 1" next time.

 

[mikemech]

Motor mount hint for non-minimum diameter LPR:
1. Stack the centering rings so the motor hook notches line up. Drill a 1/8 hole through both tubes close to the outside edge. The kevlar shock cord will go through these holes.
2. Notch the thrust block so the motor hook end will just fit. A little wide is O.K.
3. Mark the motor tube for the centering rings and the motor hook positions.
4. Cut the motor tube for the motor hook and install the hook. Install the motor hook retaining band if the kit has one.
5. Install the forward centering ring and fillet to the motor tube. Let dry.
6. Install the thrust block taking care that the notch lines up with the end of the motor hook.
7. Now for the important part. Calculate the position of the forward centering ring in the airframe body tube. E.g. if the aft end of the motor tube is supposed to be even with the aft end of the airframe tube, and the forward centering ring is 2 inches from the aft end of the motor tube, then the forward centering ring is 2 inches from the aft end of the airframe tube. Grab a cotton swab and mark the shaft 1/4 inch less than the distance from the aft end of the airframe tube. In this example the mark would be at 1 3/4 inches.
8. Slip the aft centering ring onto the motor tube. DO NOT GLUE.
9. Put some glue on the end of the cotton swab, insert the swab inside the airframe tube to the mark and smear the glue around. You may need to do this two or three times to get glue all the way around the tube. Work fast or the glue will grab the mount in an incorrect position.
10. Install the mount. Let dry.
11. Remove the aft centering ring. With a piece of scrap balsa, make a fillet at the forward centering ring / airframe tube joint. Let dry.
12. With your trusty cotton swab, smear glue around the inside of the airframe tube and the outside of the motor tube 1/4 inch short of the aft centering ring position.
13. Install aft centering ring. Let dry.
14. Get the scrap balsa and make fillets on the bottom of the aft centering ring. Let dry.

Things to remember:
1. A little thin CA around the shock cord holes can't hurt. Thread 100# kevlar ~3feet long through the holes. (I found a long needle at HL.) Tie a slip knot or lariat loop at the bottom and slip it around the motor tube. Tie the other end to the Estes elastic shock cord. Easy to check and replace.
2. You want the motor to thrust against the thrust block, not the motor hook.
7. The swab works better after it has a glob of dried glue built up.
10. You want the centering ring, or any part, to push a fillet ahead of it when installing.
11. The aft centering ring was there to keep everything straight while the first glue dried. The fillets do not need to be large or heavy. I have a tendency to overbuild.
Hope this helps.

 

[ThirstyBarbarian]

As it turns out, the glue is only spread around the rear ring, both inside and then a filet from the outside. I guess the Big Bertha body tube is too long to consider reaching all the way down into the tube to attempt to spread a ring of glue to hold the front centering ring. At least, I didn't see any instructions to do so, so it is held by the glue to the motor tube and the friction fit to the body tube.

I checked my BB instructions for the kit I built last year, and they do show a step for glueing the forward centering rings. You are supposed to spread some glue in a ring inside the body tube about 2" or so from the bottom of the rocket. Put a good amount in so it is wet and a bit runny, not a thin layer. Then you immediately shove the motor mount in --- as the forward centering ring slides past the wet glue ring, wet glue gets on the centering ring and smears inside the tube. That's enough glue to glue the forward centering ring in place. After that, you go back and fillet the aft centering ring. This is a very standard way of gluing in motor mounts in LPR rockets.

The crappy international instructions do not describe the process in words, but they do show it in pictures. Take another look at your instruction sheet and see if there is not a step for that.

Once you build enough rockets, you'll get a feel for the steps and an instinct for things that do not seem right. If I had got to the step of gluing in the motor mount, and it seemed like a centering ring was being left unglued, that would have been a red flag for me. You can't always just wing it or assume instructions are wrong or missing, but if I saw that, I would have read ahead to see if this was an unusual procedure and the CR would get glued later. And if i did not see anything like that, I would have backtracked to see if i missed a step. If not, I would have made a judgement call to glue it as I described, based on experience. Next time you'll know.

For now, I'm not sure what to recommend. You should find a way to get some glue on the forward CR --- maybe you can smear it on with a long, thin stick. A headlamp will help you look down inside the tube. Be sure to secure the shock cord out of your way until you have the glue in place and it has dried.

 

[Kirk G]

Oh crap.
I'll check out those instructions again tonight.
I thought it a little odd that there wasn't a gluing of the first ring... that squeegy is what's happened in other rockets. Why not this one?

 

[Rex R]

a bamboo skewer (or a couple taped together) does a nice job of reaching centering rings to apply/spread glue.
Rex

 

[ThirstyBarbarian]

As I get to the end stages of construction, I've tied the shock cord onto the nose cone but now notice that it increases friction for the slip fit. And after gluing the anchor inside at more than 1 1/2 inch down the tube, I know it's not impacting that. As I consider tying on the parachute, I note that it's a pre-pack assembled chute from China, carefully folded and pressed. I'm debating just looping the shrouds around the nosecone to tie it on, but not disturbing the chute, since it's so carefully folded, much better than I could do. (What do you guys think of that idea, or am I shooting myself in the foot by not fluffing the chute out and powdering it with baby powder?) Or course then, I'd have to re-roll it.

On the nose cone friction --- tying on the shock cord should not affect how the nose cone fits into the body tube. What might be happening is that the little "tail" end of the shock cord is getting caught between the NC and BT as you slide the NC in. Anything wedged between the NC and BT can cause a problem. You could check to see if that is happening and then snip off any excess tail. Or you could double the tail back along the longer piece and wrap a piece of masking tape around them, taping them both together so there is no tail hanging loose. Keep the knot --- the tape would be just to neaten up the tail, not to attach the shock cord.

If the problem is not the tail or anything else getting wedged between the BT and NC, then maybe you got some glue inside the upper part of the BT when glueing in the shock cord mount. You can sand that out.

About the parachute --- as long as the chute is folded so that the lines are the same length and not twisted, then you don't really NEED to unfold the chute to tie it. But you must unfold it and refold it before flying it --- never fly a rocket with a plastic chute that has been folded up and stored --- always unfold a stored plastic chute and refold it before flight. The plastic chutes can fail to open if they have been stored folded for too long. My feeling is that as long as you will need to unfold the chute anyway, you might as well do it now and make sure the lines are all the same length and not twisted. For my LPR rockets, I like to tie the chute to a fishing swivel instead of directly to the NC --- helps to reduce tangles and twisting, and makes the chute easier to remove if necessary.

 

[Kirk G]

Yes, you are correct...it's the small "tail" of the rubber shock cord that is binding the NoseCone slightly. I can still remove it, and plan to do so both to insert some wood glue down to the front centering ring (Thanks for the bamboo skewer idea!) and also to apply a finish coat or two to the nose cone as well as the body tube. But rather than rush it, ---I note the club launch tomorrow has been postponed due to weather. That's the right call, in my opinion...too wet, too stormy.--- I will take my time and glue Saturday and paint on Sunday as it will be drier, etc. I'll have plenty of time to do final assembly before the next weekend raindate.

 

[Rex R]

:grin: a while back I found some 'skewers' that are 3' long...for toasting marshmellons.
Rex

 

[Kirk G]

I came up with a somewhat simple solution to finding a cue tip or a skewr that was long enough.

While visiting Lowes on another mission, I was standing at the paint department waiting for a can to be mixed... and they offered me a clean, new stir stick with each gallon. While standing there, it suddenly occurred to me that this stick, while maybe not balsa, was thin and light, and long, and sturdy enough to stir with. And a lightbulb went off in my head.
I took two.

When I got home, I laid my aluminum ruler along the side of the stir stick, and with a carpet knife, I ran a pass down the length of it about 1/4" from the edge. Once this was scored, I prepared to flip the stick over and do the other side, but for fun, I just tried stressing the score, and with hardly any problem, the stir stick flexed, and began separating exactly along the score. A little more flexing, and the thin narrow piece came right off in my hand.

So, I had an applicator that was thin and narrow, and about 14 inches long.

Next, I removed the nose cone, and held the shock cord to one side, trapping it so that it couldn't flop or get in the way.
I stood the Bertha on her fins under the bright dining room table light, and carefully angled it so the shaft of light fell down the inside if the tube, holding the open bottle of Elmer's carpenter glue in one hand next to the throat of the rocket, I dipped my applicator about a half inch into the glue.

It's a messy process, but with three attempts, I got the glue down the 10 inches or so to the centering ring, but lost some small bit of glue on the side of the inner wall of the body tube. As the applicator impacted the centering ring, I moved it around the joint of wall and ring, and spread the glue, allowing it to drain a little, but also rotating the nearly square applicator, wiping the glue onto the wall where the centering ring meets it.

As I said, it took about three applications to coat around the entire rim of the ring...and at first I was concerned about the "puddling" of the glue on the ring itself. But then I knew I couldn't build a filet any better, and the extra glue being on the ring wasn't going to hurt... and that there was enough puddling or flowing down the last inch or so of the body tube, that i was going to get a good seal.

The two questions I had were about how long this filet puddle was going to take to cure and dry....and how much more weight I might have added to the rocket at the forward ring... but I figured what's done is done. And I left the Bertha setting on the table on the fins overnight, throat open, drying. By morning, a quick glance down the throat showed that the glue had hardened and I could proceed.

Had I to do this again, I might that tried a slightly smaller slice of the stir stick, and gone slower and more deliberately with the glue application. I might have had to make six attempts before getting all the way around the ring, but I was in a hurry as I was working on another project as well, and wanted to get this one into the waiting/drying phase.

It also occurs to me that I could have made the applicator slightly wider, and possibly wedged part of a cotton ball on the tip, to make my own giant cue-tip, but there would have been downsides on that also... losing the ball down the throat of the rocket... loose threads in the glue... it could have become a real mess. As it was, I had sliced, flexed and applied, all within about five minutes and then was waiting.

This morning, I've noted Mother's Day morning is temporarily dry outside, and I have taken the rocket outside to do a second shot of gloss yellow top coat. And I'm waiting for it to dry.

Still waiting for comments on possible paint schemes, or thoughts about a Big Bertha that's currently gloss yellow...

 

[Rex R]

if your recovery area is grassy, use a 12" chute. next trip to the grocery store pick up some bamboo skewers .
Rex

 

[Kirk G]

I'm not terribly pleased with my paint job, as I realized I have forgotten to sand between coats of the primer! And there might have been some brush strokes in the lowest gray primer left on the tube....or a reaction between the three different types/brands of paint that I've used.... brush on gray primer...spray all purpose primer...gloss yellow top coat. I've done one coat grey by hand, two spray white coats to lightnen it up, and then two gloss yellow coats...and I think I'm going to need a final third one, but am resolving to sand first...either with 400 grit sand paper and/or steel wool. So, we'll see what tonight brings.

 

[ThirstyBarbarian]

Mine came with the decals for the 1986, 1992 livery shown in the post quoted below, so that is the paint scheme is used. Yellow BT, two black fins, and a black NC. It turned out nice.

If you are concerned about the finish, you could always consider your yellow color coats a waste and sand with something more aggressive than 400 grit (maybe 180 or 220). Sand till smooth, even though that would remove a lot of the yellow. Then a coat of light-colored spray primer, sand with the 400 grit, and start over with the gloss yellow.

Estes Big Bertha (#1948) Basic Information.

Estes Industries

MODEL NAME: Big Bertha Also known as:

NUMBER: #1948

Introduced: 1986
Final Year:
Designer: Vern Estes

Type: Sport
Motor Mount: 1x18mm
Recovery: Parachute
Stages: 1
Length: 24 in. (61 cm)
Diameter: 1.64 in. (42 mm)
Span:
Weight: 2.5 oz. (71 g)

Mfg. Description: Big Bertha is an Estes original! Big, burly, black and beautiful perfectly describes this classic. She's an all around Estes favorite that has truly withstood the test of time. Over the decades, Big Bertha has been most modelers' first big build. While standing on its massive fins, this big black rocket checks in at an impressive 2 feet tall. If you've never flown a Bertha, get one and launch it. Once you've flown it, you'll take it to every launch!

The Big Bertha gives you a slow, realistic liftoff. What a thrill it is to watch! Propelled by powerful standard Estes engines, this beauty travels to 500 feet and comes back to earth with a decorated 18 inch parachute. Quality Estes body tubes, laser cut wood fins, molded plastic nose cone and easy to apply self-stick decals make for an afternoon of building enjoyment. In one afternoon your Bertha is ready for an exciting time at the launch field! (Estes 2011 Web Ad)

Advertising Liveries​

Estes 1986 Catalog

Estes 1992 Catalog

Estes 1993 Catalog

Estes 1995 Catalog

Estes 1998 Catalog

Estes 2002 Catalog

Estes 2003 Catalog

Estes 2004 Catalog

Estes 2005 Catalog

Estes 2006 Catalog

Estes 2007 Catalog

Estes 2008 Catalog

Estes 2010 Catalog

Face Card(s)​

First post in this thread featuring this rocket.

See Also:
TRF Build Threads

TRF Applicable Threads
Why Big Bertha?

LINKS
EMRR
RocketReviews
Mfg. Page


If you have any additional information on this rocket and/or catalog photos please let us know.

 

[Rex R]

hmm, methinks that the big bertha came out before 1986...as a kit 1966 was the earliest catalog listing that I could find .
Rex

 

[ThirstyBarbarian]

hmm, methinks that the big bertha came out before 1986...as a kit 1966 was the earliest catalog listing that I could find .
Rex

That's just one page out of the gallery. The rocket has been around forever, so I think that one page is for a model #1948, and there were other earlier model #'s with their own pages in the gallery.

 

[TopRamen]

I had the 86' Model in that Livery back in the Day. In my Opinion, one of the grooviest sets of Decals ever devised.
I don't like the Black Version.

 

[Kirk G]

So, still very disappointed in my poor brush strokes showing through the paint job on the YELLOW Big Bertha, I decided that maybe I should attach a photo to show it's current status. It's been raining and wet here for the last three days or so, and so it stalled any further attempts at painting. Since the launch is tomorrow, I doubt that there will be any further painting before the initial launch, and I don't think I'll be putting decals on this one. Enjoy.

 

[ThirstyBarbarian]

Have you considered repainting it something obscene?

 

[Mushtang]

The two questions I had were about how long this filet puddle was going to take to cure and dry....and how much more weight I might have added to the rocket at the forward ring... but I figured what's done is done.

I wouldn't worry about having added too much weight to the rocket by putting glue on the centering ring. Here's what I did to my launch lug using Carpenter's Wood Fill, and it still flies great!

 

[Kirk G]

Have you considered repainting it something obscene?

Yeah, I have thought of that, but right now, my rockets are stored in the living room, and might have to be moved to the rec room, and even then, they might still be a bit visible. (How would you like your teens have to explain a, ahem, rocket 'shaped-that-way' to their friends or guests in the house?))

No, I think I'm just about done with Bertha. I'm not thrilled with the paint job that I've got on her, but I've also learned something by doing it this way. I don't prefer the filler/primer and then sanding, and again, and again, but using spray paint to build that deal, glossy luster and smooth finish does appeal to me. So, I'll light this one up, and then I'll move onto something else soon... maybe my Neon XL or the Long Tom or something waiting in the pile.

In the meantime, my tenant has asked for screens to be put in the windows at the rental house, and that is going to take priority this weekend....the Rocket Launch is off.

 

[Kirk G]

if your recovery area is grassy, use a 12" chute. next trip to the grocery store pick up some bamboo skewers .
Rex

Yes, Rex, the field is former silage, and stubble from farm grassland, fairly soft. I'll use the supplied parachute, but might consider cutting one down to 12 inches if I have to replace it.
(Haven't found bamboo skewers yet, and I'm a little nervous about walking up to a young lady clerk and asking if she's seen any. How would YOU like to explain, "Uh, I don't want them for the traditional use...." Then she gives you are really knowing look.... Ewwww....)

 

[Rex R]

tell her you want to roast marshmellons over the stove(for smores ), or you want to make ka-bobs...been a while (they usually 100 per pack) but as I recall they can be found by the kitchen tools(peelers etc.). small mixing cups are in the cake/baking aisle (candy/nut cups). I don't suggest mini muffin cups though, the pleats would make mixing messy .
Rex

 

[JStarStar]

This was the catalog paint style in the late 60s.

I tried painting one in that pattern, by brush, and it came out looking like shhhh...... well, not very good. :y::y:

 

[Kirk G]

Wow, I kinda like that, JStar.... Looks pretty intensive....and would require the use of pinstriping or sliced thin masking tape. If you had it on hand or did a lot of it, it could come off pretty well.
I, on the other hand, have a hard time just getting a clean edge with a roll of "edgelock blue painter's tape".... LOL!