Baby Bertha D Build.

[Back_at_it]

It's that time a year again that I start looking at the rockets that I'm going to ship to AZ. Every Christmas we go out and spend the holidays with the GF's parents and flying gives us good reason to get away for a day or two while we are out there. The last couple of years I've built rockets specifically to launch out there as we have a huge open area.

This year I have a list of rockets I want to build and the first is this Baby Bertha D. I've been kicking this one around for a while now and considering that we launched an Alpha on an E30-7 and sent up a normal Bertha on an F44 last year, why not come back with Baby Bertha this year and see if we can go higher or rip the fins off I picked up a bunch of the Baby Bertha's a coupe years back when HL had the for $3.99 so why not.

Going to try to keep this build quick and simple. From left to right. Stock body tube and nose cone. 10" of 500# Kevlar, BT50H motor tube, Motor Block, Plywood centering rings, 6' of 1/4" Elastic and the stock fins.



Started assembly with the motor mount. Sanded the outside of the motor tube where the rings will attach then sanded the inside of the centering rings. Since I'm using the heavier wall BT50H the inside of the centering rings needed to be opened up slightly.

The rings were glued in place and fillets added. The motor block was sanded then inserted into the motor tube. The Kevlar leader was then tied around the motor tube just below the upper ring and a hole was drilled in the upper ring for the Kevlar to pass through. A piece of shrink tubing was added for a bit of fire protection.




After letting the motor mount dry for a couple of hours it was inserted into the body tube until the ends of the tubes were flush. In the next couple of pics we can see the Kevlar leader stopping just below the top of the body tube to prevent zippers and the internal fillet added around the upper centering ring.



That is as far as I made it last night on this project. I'll be papering the fins for a little extra strength and doing some additional assembly tonight.

Thanks for following along.

 

[Back_at_it]

Made some additional progress on the project last night. Nothing too ground breaking. Decided to paper the fins for a bit of extra strength.

Not generally a fan of doing this but I figured I'd give it another shot and I finally found a use for those instructions which otherwise go in the trash.

Papered the fins, removed the outer layer of the body tube where the fins attach and marked the tube. Also removed the lower portion of the nosecone as I will need to add nose weight and prefer to add a bulkhead.

 

[Lee]

What's your method of attaching a bulkhead to the plastic nose cone?

 

[Back_at_it]

What's your method of attaching a bulkhead to the plastic nose cone?

Since this is a thin Estes nose cone. I'll sand the inside of the nosecone just above the shoulder with a rough sand paper. Something in the 60 to 80 grit range. Clean with Rubbing alcohol then attach the Plywood bulkhead using BSI 30 min. epoxy.

If this was a heavier cone I'd use a Dremel tool with a 36 grit roll to rough it up but the 36 grit would eat through this instantly.

 

[Lee]

Not to turn this into a glue thread, but do you find BSI 30 adheres well to plastic?

 

[Back_at_it]

Not to turn this into a glue thread, but do you find BSI 30 adheres well to plastic?

Yes. I've had good luck with it. Seems to work very well with most plastics I've used it on including Estes, Quest and even the infamous LOC nose cones. Don't use it on those Cheap MPC kits though. Stuff peels right off.

I added a bulkhead to my Estes Phoenix when I built it 15ish yrs. ago using one of the BSI epoxies. Last year when I rebuilt it I needed to add some additional nose weight to get the CG back in line and I had a hell of a time getting that bulkhead out of the nose cone. I ripped the screw eye out of it before it would come loose.

 

[Back_at_it]

Found a little spare time yesterday to get the fins attached. The fins are intentionally installed to the right side of the line to ensure proper alignment. This was done consistently all the way around.

Using TBII I coated the root edge of each fin and let it sit. A bead of TBII was also laid down on the tube and rubbed into the surface to ensure good penetration. After about 5 mins. I added additional glue to the root edge and attached the fins.

Here we see all four fins attached and the first of the fillets applied. Will add a second round of fillets then begin the filling sanding of the fins.

If all goes well I should have this one in paint in a couple of days.

 

[Sooner Boomer]

I've built one of these (24mm motor BB). I flew it last Sunday on an E20-4. I think it could have used more delay. I recover mine on crepe paper streamers.

 

[Back_at_it]

I've built one of these (24mm motor BB). I flew it last Sunday on an E20-4. I think it could have used more delay. I recover mine on crepe paper streamers.

Because of the altitude I'm thinking this one is getting a 9" chute with spill hole. Will probably add in a very thin Mylar streamer just for tracking. With the E30 on board i'm looking at just short of 2000'. This is a small rocket to be tracking at 2000'/

 

[DigBaddy]

Because of the altitude I'm thinking this one is getting a 9" chute with spill hole. Will probably add in a very thin Mylar streamer just for tracking. With the E30 on board i'm looking at just short of 2000'. This is a small rocket to be tracking at 2000'/

Dang. I run a 9" chute with a spill hole on a stock BB and am about to convert it to a streamer. Still comes down too slow...but I usually am on a small field. It's fallen with a wadded up chute more times than I'd like to admit and still survives. Can't imagine an E30 in one...don't give me ideas

 

[Back_at_it]

Dang. I run a 9" chute with a spill hole on a stock BB and am about to convert it to a streamer. Still comes down too slow...but I usually am on a small field. It's fallen with a wadded up chute more times than I'd like to admit and still survives. Can't imagine an E30 in one...don't give me ideas

I have a place out in AZ that it would be impossible to loose something unless you lost sight of it coming down. Figure a 9" chute and some mylar will slow it down long enough to let me find it in the sky. I don't mind if I have to drive to get it.

 

[Sooner Boomer]

The streamers I use are as much for visibility as for slowed recovery. I use 10 - 20 feet (sometimes doubled)

 

[Back_at_it]

Finished up the fillets, added a 3/16 launch lug, installed the bulkhead and decided to throw on an Estes 24mm motor retainer. Then I shot on two coats of SEM high build primer. After sanding with 400 grit it was time for paint. I have some older cans of Duplicolor on the shelf that are almost empty so I went with a Ford medium Blue Metallic for the base color.

Got two coats applied. Will be doing the fins and vinyl later today. Hopefully flying tomorrow as I have a couple of days off.

 

[Huxter]

That IS a beautiful finish! I need to try some of that Duplicolor - keep hearing and seeing great things about it! I need to try papering fins too...

 

[Back_at_it]

Got this one done. Been a nice warm day and Duplicolor only needs about 30 mins to dry between colors so here we go. Painted one fin a dark red metallic. Can't tell the color as it's rubbed off the can. Painted another fin gloss black.

Added cut and applied vinyl graphics. This one is done and ready to fly tomorrow.

 

[Sooner Boomer]

That is a really beautiful color blue. It turned out magnificently. "Too pretty for flight".

 

[Back_at_it]

That is a really beautiful color blue. It turned out magnificently. "Too pretty for flight".

it really did turn out pretty nice. I’m really happy with that shade of blue.

Weather permitting we’re still flying tomorrow so it’ll be going up

 

[Back_at_it]

Made it out to fly today. Only took 10 rockets with me so I managed to get the Baby Bertha up in the air twice.

First flight was on a C11-5. Nice stable flight to about 450ft. Second flight was on a D12-7. The rocket jumped off the pad and flew dead straight and stable. Well out of sight until ejection. Recovered on 9" chute with a 4" spill hole. Also attached a 1/2" wide silver foil streamer for tracking. Made it visible the whole way down.

Here are some pics. I'll consider this one done.

 

[Huxter]

The rocket jumped off the pad and flew dead straight and stable

Isn't that a GREAT feeling! Taking a bunch of parts and making them do this! WAHOOO!! Great job!