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Diminutive Bertha Instructions

Updated: Aug 16, 2023

Model Rocketry is a fun and safe family activity.

model rocketry is a science your results may vary depending on how you build the rocket. please read the National Association of Rocketry model rocketry safety code and the model rocket handbook.

My Instructions are meant as a guide and are not a guarantee of stability or function of the product.

This rocket has been tested and proven but your results may be different.

depending on your skills.

Launching rockets can be dangerous and requires adult supervision. you use our products at your own risk. OLLIE-OOP Model Rocketry is not responsible for any damages or injuries incurred from use or misuse of our products. you are responsible for the Contruction and stability of your rocket. please follow all safety codes and launch procedures as stated by the NAR handbook.

our kits are not intended to be modified. Please use the recommended engines.

Always follow the NAR safety code at

Read all steps before beginning. Always dry fit the parts on every step that requires glue. And always add a reinforcing bead of glue to all joints the required glue and wipe off excess glue with your finger. Unless stated otherwise.

Always wear safety glasses and mask when cutting with a knife, saw, drill, rotary tool or when sanding or using powder.

The Diminutive Bertha and HDS Story

The Diminutive Bertha is a Franken rocket. It was acquired by a friend of mine Harold Sasloe from the unknown original builder. To be sold or scrapped... It is part Bertha and part Ranger and an unusual size.

HDS is an inside joke between my friends, Danny Almond, Harold Sasloe, Richard Mattera and Jim Bassham HDS stands for. Harold’s Disposal Service He takes in lots of mostly built rockets and resells or scraps them. We have fun with the name and naming the rocket.

I liked the Bertha rocket very much as did Harold and we were left wanting one of our own. Thankfully he took measurements before he sold it. Upon building it, I thought that others would like it too. So, I decided to kit it at the great dismay of Harold doing his very best to convince me to simply give it a Viking funeral at sea, with fire LOL I overcame his futile attempts to derail the kit with very little effort. LOL ;)

It never had decals; they are my addition. It didn't have a name, Harold ultimately named it the Diminutive Bertha. And sold it on Ebay. It not only spawned my Bitty Bertha kit but is the reason I created the group Estes Bertha Model Rocket group on Facebook.

You created a great thing Harold, people like it and the Bitty Bertha very much and the Facebook group is spawning new Bertha creations all the time. Thanks for not actually trying to make me stop.

Toby C.

You can see a picture of the original at the very end of this page.

Step 1

Locate motor mount parts.

Motor tube, rings, braided cord and motor hook.

Make a mark 1/4" from the end of the motor tube and a mark from the other end at 1/2."

Using a hobby knife make a 1/8" slit at the 1/4" mark.

Test fit the rings on the tube with motor hook in the 1/8" slit, if the parts don't fit together easily, lightly sand the inside of the ring until everything fits. Test fit it in the body tube also.

Run the braided cord through the hook gap on the FWD ring and tie the end around the center of the motor tube. Tie it around the motor tube. Put a drop of glue on the knot.

Slide the rings away from the marks and place a ring of glue around the tube just before the marks, so that when you slide the ring up to the marks the rings go through the glue.

Put a bead of glue inside the FWD end of the tube, the end with the slit and insert the small motor block ring until it stops on the motor hook. If your kit has more than 1 of these rings, then glue them all in stacked together.

Set the motor assembly aside and let dry fully.

When finished it should look like the one in the picture.

If you want to reinforce the hook. You can wrap a small pc of tape around the center or glue a strip of paper around it.

Add reinforcing glue to both sides of ring and wipe with finger. Put a drop of that glue from your finger on the knot on the braided cord.

Run cord down mount before install.

Sand the fins. You can choose to round the edges or not to its your choice of looks. DO NOT round the root edge.

Place tube on guide and mark 4 fin locations, BE CARFUL NOT TO MOVE THE TUBE DURING THIS PROCESS, extend all 4 lines 4" with door frame or straight edge.

Pick a location between 2 fins and mark a 5th line 6" long with a door frame. Mark it with a LL for launch lug. The lug will be glued on at this 6" mark. Make sure to keep it as straight as the line or the rocket will not fly straight. Add a reinforcing bead of glue to both lug joints, don't get glue inside the lug. Also, when painting the rocket be sure not to get paint inside the lug. seal it with some cotton. Attach the lug after the fins and let it dry overnight.

If the motor mount is dry.

Feed cord down mount and out the AFT end.

Place a line of glue around the inside of the AFT end of the body tube, about 2" in.

Insert mount, stop about 1" in and very quickly add another line of glue around the inside of the body tube, just at the end.

Push mount without stopping until both tubes are even, note the hook placement durning this process. Add a line of glue to the AFT ring and tube joint, wipe off extra with finger. Let fully dry 24Hrs

Place glue on the root of a fin and glue it on a fin line, keeping it straight and at a 90-degree angle from the tube. Check alignment from both ends of the tube.

Make sure the fins are positioned correctly, with the rocket standing up the fins should sit flat.

(See picture)

Let each fin dry in place before moving to another. Once dry, add reinforcing bead of glue to each joint and wipe off excess with finger.

It should look like the diagram below.

Fins sit flat on a surface

The fins should look like this when viewed from the AFT end.

View from the FWD end

Locate the red or brown coupler, disks, short yellow cord, balsa nose cone and clear payload section.

Make a mark on the coupler directly in the middle.

Put a bead of glue around the very inside edge of one end of the coupler and insert the disk with 2 small holes. Position it flush with the end of the coupler.

When it's very dry and will not move, feed both ends of the short yellow cord through both holes in the disk. Feed both ends through the other disk with single hole. Tie both ends in a loop knot, put a drop of white glue on the knot.

Install the other disk the same as the last, flush with the other end of coupler. Add a little reinforcing glue to each joint.

When complete it should look like the one in the picture below.

Make sure the cord is just as long as the coupler on the inside, you don't want slack in it.

Example of configuration before install in coupler. You can also opt to use 1 hole and tie a knot on one end of the cord on the outside of the ring and a loop knot on the other end. Either way the cord should be fairly easy to replace.

Dry fit the nose cone in the clear payload section. It needs to fit very tight, use tape to friction fit it or clear scotch tape around the outside for flights. You do not want the cone to come off during flight, but you do want it to be removable if you plan to use the payload section.

If you do not plan to use it, then attach nose cone to payload section with plastic cement.

Scotch clear tape or your preference of removable painters tape should only be applied to a well dried and smooth painted surface of the balsa nose cone.

Use plastic cement and install the coupler in the payload section up to the halfway mark, turn it a half turn, wipe off excess cement, let dry.

You can use CA but it might fog up the clear tube.

Feed yellow cord out the FWD end of the rocket and tie the swivel to it, put glue on knot. Snap swivel to loop. Attach your chute lines on the same swivel or you can use a second swivel if you have one. The whole payload section is the nose cone. The coupler must fit the tube like a nose cone, you will need to use fine sandpaper to sand the coupler and maybe even a little inside the body tube until you get the right fit. Hold rocket by the nose and shake it, it should fall off with 1 or 2 shakes. Use a little baby powder or graphite to help.

You can put a small led light in the payload section, mine light weighs 4 grams. and had almost no effect on the rocket. I do not recommend that you put any more weight than that in it.

Builder/flier agrees to use OLLIE-OOP products at your own risk.

I flew her on a 13mm Estes A-10 with my custom made 18mm to 13mm motor removable adapter. It was a low and slow flight.

Recommended engines

Estes BP 18mm

A-8, B4, B6, C6

The original Dim Bertha

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