Pemberton sculpted tube fins

Boreas · Jan 29, 2019

Sorry if this is a repeat. I am looking for a way to adapt the Pemberton sculpted tube fins found on Kraken/King Kraken to different tube sizes. Is there a particular formula for marking the tubing, or is it just trial and error? Thanks in advance.

gpoehlein · Jan 29, 2019

I don't remember what the issue number is, but there is an issue of Apogee's newsletter that tells how to make slanted tube cuts that might help. Also, if you can wrap a piece of paper around the shaped tube and trace the cut (or find the template), these things scale up and down perfectly. Just scan the template and blow it up to the larger tube size.

Boreas · Jan 29, 2019

gpoehlein said:
I don't remember what the issue number is, but there is an issue of Apogee's newsletter that tells how to make slanted tube cuts that might help. Also, if you can wrap a piece of paper around the shaped tube and trace the cut (or find the template), these things scale up and down perfectly. Just scan the template and blow it up to the larger tube size.

Thanks. I have found plenty online for simple slanted tube fins, which I have used frequently. It is the sculpting of the Pemberton design I like. It uses a flexible straightedge wrapped at measured distances along the tube that creates the sculpted effect.

kuririn · Jan 29, 2019

There is no template per se, It uses a series of measurements along two centerlines 180 deg. apart. So do you have those figures, and are you asking how to up/down scale the measurements? I would think that multiplying by the ratio of the tube sizes to each other would give you the correct measurements, right?
If you don't need an exact duplicate of the Kraken tubes, why not experiment with the measurements, lengthening or shortening them? Make the design your own. Could be pretty cool. Cheers.

dhbarr · Jan 29, 2019

https://www.pembertontechnologies.com/wp-content/uploads/2016/01/Kraken_LPR_Destructions.pdf ?

Boreas · Jan 30, 2019

kuririn said:
There is no template per se, It uses a series of measurements along two centerlines 180 deg. apart. So do you have those figures, and are you asking how to up/down scale the measurements? I would think that multiplying by the ratio of the tube sizes to each other would give you the correct measurements, right?
If you don't need an exact duplicate of the Kraken tubes, why not experiment with the measurements, lengthening or shortening them? Make the design your own. Could be pretty cool. Cheers.

Thanks! Yes, I have the measurements from my original kit. I guess I will use the ratio method of up/downsizing. Probably wouldn't matter if I used circumference or diameter. I would try experimenting, but body tubes aren't cheap - especially big ones!

Boreas · Jan 30, 2019

Thanks all for your help. I got it figured out and was even able to make some modifications!

kuririn · Jan 30, 2019

Good job! Enjoy the build.

Boreas · Feb 6, 2019

We'll see if it works. Undecided on the canard tubes. Thanks!

GlenP · Feb 6, 2019

you can trim the launch lug to match too.

Are those engine mounts in those ring fins?

neil_w · Feb 6, 2019

Very nice use of canted cluster mount!!!

kuririn · Feb 6, 2019

You can do the canard tubes in the same way as the sculpted tubes. Just too cool.

Boreas · Feb 6, 2019

GlenP said:
you can trim the launch lug to match too.

Are those engine mounts in those ring fins?

No. It is a "standard" canted motor mount built on its own, then shoved into the body tube after trimming the cutouts. Then the fins were cut roughly to match the body tube cutouts and slipped over the exposed motor tube and glued.

Boreas · Feb 6, 2019

GlenP said:
you can trim the launch lug to match too.

Are those engine mounts in those ring fins?

Boreas · Feb 6, 2019

I was going to mount the fore launch lug inside one of the tube canards.

Infamous · Mar 2, 2019

lakeroadster · Mar 2, 2019

Unleash........ The KRAKEN!

Neat thread.

Boreas · Mar 10, 2019

Not keen on the final colors, but here is the finished product. Grey should have been darker, Hot Pink was supposed to be fluorescent red. Results may vary...

mbeels · Mar 10, 2019

I like it, nice work! Can't wait to see a launch photo with those canted motors.

Thundercloud · Mar 11, 2019

Awesome! Love it!

Boreas · Mar 12, 2019

mbeels said:
I like it, nice work! Can't wait to see a launch photo with those canted motors.

I am interested to see what effect the tube fins will have on the smoke, if any.

BABAR · Apr 3, 2019

Very nice!

Pemberton sculpted tube fins

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