Question below -- can I include a base-drag cone on simulation for a Super Baby Bertha?
I posted in the "What I did today" thread that I finally assembled my Super Baby Bertha earlier this week. This is a really simple build -- I CNC'ed the fins and centering rings + 3D printed a simple motor retainer, engine block, and top centering ring / stuffer tube block (I bought BT-80 body tubes and picked up a couple of stock Super Bertha Nose cones to make it extra simple). I decided to make the fins with 2mm plywood instead of the much thicker balsa that the Super Big Bertha comes with. I am guessing I will get some fin flutter but not planning on putting anything bigger than an E12 in this (more likely a D12). I also cut my centering rings from the same material. I am guessing that 1/8" plywood is much stronger but once everything is glued together this seems quite rigid (and 2mm plywood is super light). I also decided to use a stuffer tube to help keep my parachute forward and to make it easier to pack wadding in (hence the 3D printed forward centering ring). Finally, I left the BT-80 tube stock length even though that is like 2cm longer than is should be for the Baby Bertha. Came out to 155g w/ CG at 29.5cm with a parachute but no motor.
This morning was weighing and finding CG etc... to check stability when fully loaded. Is it appropriate to put a base-drag cone on simulation for this model? It is not really as short and stubby as some rockets but my configuration was suggesting I might need some nose weight. I am pretty sure that the Bertha's are pretty darn stable so was guessing that OR was being conservative.
Here is the sim without the base-drag cone...
I posted in the "What I did today" thread that I finally assembled my Super Baby Bertha earlier this week. This is a really simple build -- I CNC'ed the fins and centering rings + 3D printed a simple motor retainer, engine block, and top centering ring / stuffer tube block (I bought BT-80 body tubes and picked up a couple of stock Super Bertha Nose cones to make it extra simple). I decided to make the fins with 2mm plywood instead of the much thicker balsa that the Super Big Bertha comes with. I am guessing I will get some fin flutter but not planning on putting anything bigger than an E12 in this (more likely a D12). I also cut my centering rings from the same material. I am guessing that 1/8" plywood is much stronger but once everything is glued together this seems quite rigid (and 2mm plywood is super light). I also decided to use a stuffer tube to help keep my parachute forward and to make it easier to pack wadding in (hence the 3D printed forward centering ring). Finally, I left the BT-80 tube stock length even though that is like 2cm longer than is should be for the Baby Bertha. Came out to 155g w/ CG at 29.5cm with a parachute but no motor.
This morning was weighing and finding CG etc... to check stability when fully loaded. Is it appropriate to put a base-drag cone on simulation for this model? It is not really as short and stubby as some rockets but my configuration was suggesting I might need some nose weight. I am pretty sure that the Bertha's are pretty darn stable so was guessing that OR was being conservative.
Here is the sim without the base-drag cone...
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