Bumble Bertha

[bobbyg23]

I found this in the garage and it was missing 2 fins. I made new fins from lite ply. Had the idea of painting it like a bee. My daughter said to make the 2 new fins silver like a bees wings. Once it dries I will do a launch and see how it looks in the air.

 

[kuririn]

Why are you starting a second thread on the same rocket?
https://www.rocketryforum.com/threads/big-bertha-rebirth.159111/#post-1993185

 

[bobbyg23]

Why are you starting a second thread on the same rocket?
https://www.rocketryforum.com/threads/big-bertha-rebirth.159111/#post-1993185

Couldn't figure out how to change the title of my other thread and wanted it to be named Bumble Bertha.

 

[kuririn]

Got it. For the future if you started the thread you can go to the top of the thread and click on "more options "(the three dots with the down arrow). Then you can modify the thread title.
Nice repair job. Please show us launch pics.

 

[bobbyg23]

Got it. For the future if you started the thread you can go to the top of the thread and click on "more options "(the three dots with the down arrow). Then you can modify the thread title.
Nice repair job. Please show us launch pics.

Thanks for that. I didn't even see that row of options.

 

[BABAR]

Thanks for that. I didn't even see that row of options.

I didn’t know either!

 

[Rocket86]

Looks great. Keep those old Big Berthas flying.

 

[gldknght]

I found this in the garage and it was missing 2 fins. I made new fins from lite ply. Had the idea of painting it like a bee. My daughter said to make the 2 new fins silver like a bees wings. Once it dries I will do a launch and see how it looks in the air.

Hi, nice looking rocket. But, there could be a major problem with your repaired/new fins. You say you cut them out of lite ply? They look like ordinary balsa? The problem that I see is the direction of the grain in the wood, plus the glue joint toward the back of the fins. If that is ordinary balsa, those fins will definitely shear off along the wood grain, most likely on the first landing. If they are made of lite ply, the two new fins will most likely break along that glue joint toward the back of the fin, because the joint is not supported by, or glued to the body tube.

It would be better to cut those fins out of a single piece of wood, rather than butt-join two pieces, and cut it with the grain perpendicular to the body tube.

If you must butt-join two pieces of wood, position the joint farther forward, so the joint is glued to the body.

 

[bobbyg23]

Well if flies great. My calculations were a bit off so it got wet. It will fly again though. I think I used to small of an engine.

 

[nosecone]

Well, at least it was a landing you'll never forget ! Thanks for sharing the video, I love a good Big Bertha launch anytime

 

[bobbyg23]

Well, at least it was a landing you'll never forget ! Thanks for sharing the video, I love a good Big Bertha launch anytime

Definitely needs a bigger engine next time.

 

[SCooke123]

Nothing like a good bath!!! Glad it flew well.

 

[bobbyg23]

I got the motor mount replaced and had my brother and his family out tonight. The kids loved launching rockets.

 

[mikewrt]

I got the motor mount replaced and had my brother and his family out tonight. The kids loved launching rockets.

Nice launch
Do you remember what motor you used on the may 7th flight? What about yesterday?

 

[bobbyg23]

Nice launch
Do you remember what motor you used on the may 7th flight? What about yesterday?

I believe may 7th was a b4-4. Might have been a b6-4. Last night was a b6-4. The 7th was windy and I am still learning about which way to angle everything. On the 7th I pointed it into the wind. That was not good as it just flattened out and didn't get much elevation.

 

[bobbyg23]

I will get some c6 engines sometime to try out.

 

[BABAR]

Well if flies great. My calculations were a bit off so it got wet.

Well, at least one more similarity to the Apollo missions!

 

[DaHabes]

I believe may 7th was a b4-4. Might have been a b6-4. Last night was a b6-4. The 7th was windy and I am still learning about which way to angle everything. On the 7th I pointed it into the wind. That was not good as it just flattened out and didn't get much elevation.

With big fins and a slow launch you have to be wary of weather-cocking. When you used a low impulse engine (slow liftoff) and angled it that much into the wind, the wind will push on those fins and the nose will drop. That's why it went ballistic. You rarely need to angle the rod more than a 5 degrees. If the wind is too strong it's better to abort.

 

[Back_at_it]

I believe may 7th was a b4-4. Might have been a b6-4. Last night was a b6-4. The 7th was windy and I am still learning about which way to angle everything. On the 7th I pointed it into the wind. That was not good as it just flattened out and didn't get much elevation.

When flying large rockets on low motors, I prefer to launch straight up. A stock Bertha flies really well on a C6-5. Yours with the plywood fins would be a perfect candidate for a C6 or even the recently re-release C5-3.

 

[bobbyg23]

When flying large rockets on low motors, I prefer to launch straight up. A stock Bertha flies really well on a C6-5. Yours with the plywood fins would be a perfect candidate for a C6 or even the recently re-release C5-3.

I was going to try and get some c5-3 engines to try. I learned a lot that day.

 

[bobbyg23]

With big fins and a slow launch you have to be wary of weather-cocking. When you used a low impulse engine (slow liftoff) and angled it that much into the wind, the wind will push on those fins and the nose will drop. That's why it went ballistic. You rarely need to angle the rod more than a 5 degrees. If the wind is too strong it's better to abort.

I didn't know that at the time, but I know now. I learned a lot that day.