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3D Printing Black Brandt II fin request.

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vcp

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From the BBII fin, it took only a few minutes to make a BBIIA fin, since it was mostly deleting elements of the BBII fin and changing some dimensions.
2020-09-11 15_56_46-Window.jpg
 

jazzviper1

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What scale were these modled in? Prusa slicer auto reduces to fit the print bed so I don't know where to start the scaling process.
 

vcp

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Give me a day or so, I want to rework some bits of these, and I'll repost them.

About the scale. I model these in full scale, measured in mm. I'm not familiar with the Prusa slicer, but I'd be surprised if it doesn't tell you somewhere the percent by which it has been scaled to fit - I'd think it would give you the option to adjust from there (?).

When I bring it into Simplify3D, it brings up a message that it's too large, and gives the option to scale down or not. When I say no, it comes in (too large) and then I select it and scale to what I want. I'd be surprised if Prusa doesn't give some similar options.

You've mentioned 1/13 scale, so I'd guess that's a BT55ish model, 34mm tube. The BBII motor is 17.2 inches, 436.9mm**. So the true scale (not counting any paint thickness) is 34/436.9 = 1/12.85 scale. That's what I'd use for scaling the fins, especially here where the printed fillet needs to be a good fit on the body tube. So 1/12.85 = 0.0778, or 7.78% of full scale.

**The Russian drawing gives the body diameter as 437.1mm.
 

Ez2cDave

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Jack Hydrazine

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bobby_hamill

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VCP
The diamond shaped airfoil fins were on the 3 fin Black Brant 2 The Black Brant 4 fin version had the
wedge shaped fins. The small "tabs" on the back of the diamond shaped fins were used to create spin.

I Already have 3d parts made for a 6" Black Brant 2 that has 4 fins . They are 2 types of telemetry antennas,
radar beacon antenna, Forward launch lug And I had a mold made to pour a fin made from Alumilite casting resin

I even have 3d parts of the forward rail that the forward launch lug slides onto

Bobby
 

Funkworks

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A black brant is a species of migratory goose.

https://en.wikipedia.org/wiki/Black_brant
Yes but they have a cool history!
 

bobby_hamill

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here is the link to the fin mold for the 6" Black Brant with 4 fins

 

bobby_hamill

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I am also working on a 3d drawing of the boom launcher that was used to launch the Black Brant at Wallops Island
 

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bobby_hamill

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jazzviper1
Here is a close up of the fin attachment from the photo you posted but it is from a 5 meg high res file
This might help some
fin close up.jpg
 

bobby_hamill

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It is supposed to be on all 3 fins and introduces a spin to the Black Brant to aid in stability
 

Ez2cDave

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Bobby,

Since it is intended to induce spin, I assume that is only on one side of the fin ?

Are they present on all BLACK BRANT rockets or just the 3-finned version of the BBII ?

Do you have any dimensioned data for it ?

Dave F.
 
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manixFan

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Ok, here are the fins with a center split for flat printing. There are two sets of port and starboard halves, one with the flare mount, one without. These .stl files are full size. I didn't try to scale them because 1/13 and 1/6 scale are almost certainly approximations. The actual scales are probably more something like 1/13.1415962 and without those kits in-hand I can't tell you what that approximation might be. Most likely it will be the exact ratios of the body diameters. Once you have the scale you want to use, express it as a percentage and scale the .stl to that percentage in the slicer.
I see you are doing these in OpenSCAD, I hope you will eventually post the original files. I've learned a lot about OpenSCAD by pouring over your files.

Thanks for sharing your hard work,


Tony
 

manixFan

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What scale were these modled in? Prusa slicer auto reduces to fit the print bed so I don't know where to start the scaling process.
Scaling is simple in Prusa slicer. I've circled where the model is scaled. You can see it is scaled to 15.87% to fit the bed. It was stated the fins were modeled at 100% of original size, so just figure out how large you need them for your use.


Tony
Prusa-Scale.png
 

bobby_hamill

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Bobby,

Since it is intended to induce spin, I assume that is only on one side of the fin ?

Are they present on all BLACK BRANT rockets or just the 3-finned version of the BBII ?

Do you have any dimensioned data for it ?

Dave F.
Dave
I just have the photos that show it from a distance
A far as I can tell it was just on the 3 fin BBII
 

Ez2cDave

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Dave
I just have the photos that show it from a distance
A far as I can tell it was just on the 3 fin BBII
Bobby,

I suspect that the reason why I never noticed it before is that it would be very difficult to see on a solid Black fin, common to most BLACK BRANT II pics, since Black & White imagery is the norm.

Is there any dimensioned data for that component ?

Dave f.
 

vcp

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Sorry, I've been away from this for a while. Just as well, over on this thread, Bobby posted new pics that trash everything that's been known about this fin (for the 3-fin early BBII). I'm fixing up my OpenSCAD files now.
 

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