Fin alignment techniques for big rockets...

[Bat-mite]

Here are some pics to follow my earlier post. As somebody mentioned earlier, fins are glued one at a time with the others dry-fitted for alignment.

View attachment 476436

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That's what I do. A small piece of foam board and a matte knife. https://www.rocketryforum.com/threa...house-formula-200-booster.144613/post-1766945

 

[cwbullet]

Just uploaded it to Thingiverse.

https://www.thingiverse.com/thing:4927909

That is probably as slick a design as I have seen. That would be a good design for a customizer from OpenCad.

 

[neil_w]

Just uploaded it to Thingiverse.

https://www.thingiverse.com/thing:4927909

Damn that is indeed extremely clever. I wonder if there's a way to extend the concept so that it can work with different body sizes and maybe even 3 vs. 4 fins. For those of us without 3D printers at our disposal, the practice of printing a custom guide for every rocket is just not practical, so multi-purpose designs are appealing.

 

[Hobie1dog]

I've tried making two different ones out of foam core board and can never get the cuts in the board to be accurate. I must be using the wrong knife, It always comes out ragged. After I did the last one I thought it would probably be better to make one out of quarter inch plywood and use the width of the saw blade which is likely 1/8 of an inch to be the same as most fiberglass and wood fins, to make the main cuts with

 

[neil_w]

I've tried making two different ones out of foam core board and can never get the cuts in the board to be accurate. I must be using the wrong knife, It always comes out ragged. After I did the last one I thought it would probably be better to make one out of quarter inch plywood and use the width of the saw blade which is likely 1/8 of an inch to be the same as most fiberglass and wood fins, to make the main cuts with

Cutting foam core board absolutely requires a sharp blade, as I have learned. Once I started being much more careful with that, I started to have much better luck cutting the stuff cleanly.

With a straightedge, good cutting surface, and a fresh sharp blade, it should be straightforward to get clean fin slots.

 

[kenstarr]

I cut out a couple of MDF guides last week for some big fins. In conjunction with a couple of framing squares they worked out quite nicely!

 

[maverickrocketry]

i just have custom fin alignment guide's made. anyone with a cnc machine can make some.

 

[Hobie1dog]

i just have custom fin alignment guide's made. anyone with a cnc machine can make some.

pictures please

 

[majordude]

I used a 3d printed fin guide for my Super DX3, printed in 3 pieces to fit smaller print beds.

View attachment 476263View attachment 476264

Amazing!

 

[Tech 68]

How I did mine.

 

[plugger]

I use Fin Alignment Guides cut from a 3D CNC

 

[astronwolf]

Here is a thread from 13-years ago about a very different fin alignment method for large rockets. Seems simpler to me.
https://www.rocketryforum.com/threads/homemade-fin-alignment-guide-version-2.9859/#post-681802

 

[Banzai88]

Cutting foam core board absolutely requires a sharp blade, as I have learned. Once I started being much more careful with that, I started to have much better luck cutting the stuff cleanly.

With a straightedge, good cutting surface, and a fresh sharp blade, it should be straightforward to get clean fin slots.

This. I almost exclusively use form board fin guides made from printed online template makers (https://www.payloadbay.com/index.php?page=Tools&action=FINGUIDES) rubber cement glued to the foam board. Works well enough that very few of my rockets have any twist to them in flight.

 

[waltr]

This. I almost exclusively use form board fin guides made from printed online template makers (https://www.payloadbay.com/index.php?page=Tools&action=FINGUIDES) rubber cement glued to the foam board. Works well enough that very few of my rockets have any twist to them in flight.

Same here. And with Thru the wall fin slots in alignment in-line with the BT is always correct..
These have almost no spin on launch.

 

[jadebox]

For my most recent builds, I assembled the motor mount and fin assembly outside of the body tube then slid a slotted body tube over the assembly. This allowed me to create notched centering rings to align the fins without the need for any external jigs or tools.

The basic technique is described in the post at:

https://www.rocketryforum.com/threads/deja-youbee-a-rebuild-thread.36421/post-339654
But I am using laser-cut rings now that are more accurate. As long as the rings are accurately aligned on the body tube, which isn't hard to ensure, the fins end up really well aligned.

 

[reddrock]

We used cardboard templates on the 7.5x upscale Trident.

 

[Banzai88]

We used cardboard templates on the 7.5x upscale Trident.
View attachment 574714
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That.Is.Epic!!

 

[KenECoyote]

I made my own after I wasn't quite happy with others I've tried. It's also modular, so I can adapt to different fin widths and motor mounts (to a point as long as I make more of the rear CR piece). Also works for double fins (mid fins in line with rear fins).

Good:

Bad:

The catch is only 1 fin at a time, but if you want accuracy, then you usually give up speed and efficiency for something like this imho.