How big is too big for tumble recovery?

I love our Flutter-By and got to wondering about doing an upscale. I would love to build a BT-80 version. Do y'all think it would work, or should I go smaller?

Nothing is "Too Big" for Tumble Recovery, but you would have to be careful where you fly a Large one due to Safety Concerns.
Also, if you want to fly it more than once, as a large Tumble Recovery would likely incur some Damage upon landing.
I'de hate to get bonked on the Head by something say 7-8" in Diameter coming down Tumbling.

Weight increases by the cube of dimensions, but surface area for air drag increases only by the square of dimensions. Thus, the practical benefits of tumble recovery decrease as the size of the model increases. (The ratio of weight-to-air drag force increases with size.) We know that we can go up to at least C-motors, because a burned out C-motor is about the same weight as a burned-out A-motor, disregarding the fact that you might never be able to find a light C-powered model again. I have used D-motors for flutter or tumble recovery on a first stage booster. It works well.

I'm going to try tumble on a 2 stage mega mosquito booster, I'll let you know how it goes. I've dropped about 40 feet and it tumbles ok.

Thanks for the info! I may just have to try a BT-80 Flutter-By some time. I believe that it would be light enough to still tumble thanks to those huge fins.

I have a couple of ideas floating around in my head that may help to reinforce those huge fins with only a small weight penalty. My thoughts are 3 ply, TTW fins similar to a Mega Mossie. The fins would be a basswood core with balsa skin and the fwd fins would be glued to a 'motor mount like' assembly. If I lay up some fiberglass sheet for the CRs here, it would help to minimize extra weight in this area. The actual motor mount tube would extend into this to ensure a satisfactory seal for separation. I'll be making notes as I build the F-B and Mega Mossie that arrived yesterday.

I have some other ideas that would be fun to incorporate, but they would definitely add weight and my skills and experience even further (I think it would look real nice with a boat tail).

I welcome any suggestions. I hope to keep this one from being a concept only and your thoughts will help to keep me on track!

I'm certainly no OR prodigy but here are my musings. It is looking like this is moving towards mid power and clustering. MPR is not a new thing for me but clustering is.

Maybe this thread could be moved to the MPR forum so I can get more of their input.

View attachment Flutter-By Up Scale.ork

I'm not sure this is relevant but I had separation of a Madcow Tembo and the body came down without recovery from about 1000 feet. It landed on a gravel road and only sustained a ding to one of the fins. I am not advocating dropping something this big without a recovery device but large objects can tumble and come down fairly slowly. Build something this large much lighter and I would suspect it would survive a landing.


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It looks like weight could be an issue here though. In the simulations, I had to use an E motor to get it to fly. I'm not sure if my problem is excess weight in the design or an error in component properties. My gut feeling is that this will work but I would like to have something a little more viable before I start gathering materials.

I recently launched “Ascension” a two stage rocket using Estes’ new 29mm BP motors.

The booster built around a BT 60 Tube along with its spent F12-0 casing tumbled to earth with no damage to its big balsa fins.

Do you remember the "myth of sisyphus"?

THAT's too large for a tumble recovery. LOL!