Attaching fins to a minimum diameter rocket

Hi,
I am going to be building a 2 stage, minimum diameter rocket that is exspected to accelerate between 770 and 896 miles per hour. I am currently lv 1 certified but want to have a 54 mm mount for when I get my Lv 2, my question is, what is the best way to attach fins to the rocket if the motor mount takes up the entire diameter of the body tube. This is going to be a scratch build of the Shadow Aero SHOCK VALUE except in 2 stage if any of you have built this kit and know what their instructions say on fin attachment, could you tell me what shadow Aero suggests or what has worked for you in the past.
Thanks for your help
Thomas Sak

snipped-for-privacy@fluidwebz.com (TJ) wrote:
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accelerate to a speed, not accelerate between two high speeds.
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Purchase AIR-10 tech report from me and use "Interlap attach".
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I've done this on two of them and they worked well.
Cut a slot in the airframe for each fin, to 1/2 the depth of the wall thickness. Put JB weld into the slot, not on the fin. This ensures no air bubbles between the fin and the airframe. (JB weld has more heat resistance than most epoxy.) Drill small holes along the root of the fins to act as small rivets. Make generous fillets with a high quality epoxy mixed with short glass fibers.
Some people add a strip of glass or CF cloth at the root of the fins but I've never done this. It definitely wont hurt. :-)

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What, no quantitative numbers, Doc? <g>
- Rick "Any testing donations needed?" Dickinson

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Unfortunately, no. :-(
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Yes!!! Shear pins and short coupler/tube assemblies. (You had to ask!)

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Shear pins I can handle. 100 ea. 2-56 and 4-40 nylon screws are on their way to you from Micro Fasteners. Have fun destroying them!
By the way, I couldn't find your address on the rocketmaterials.org site anymore. I went to the http://www.cmcscr.org/index.htm page, and had the parts shipped to the address listed there, to the attention of 'Drake "Doc" Damerau, Chief Metallurgist'. Hopefully, they will find their way to you....
- Rick "Screwy" Dickinson

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You did good Rick, you did good. :-) Thank you. This enable me to do tons of tests.

See link below for a pictorial on how I vacuum bag the fin cans on my min dia birds with surface mounted fins:
www.blastzone.com/stratosrebuild.asp
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resistance

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You must have an exceptionally understanding spouse!
Good site.
Quilly "shuddering at the thought of SWMBO's reaction to a rocket in the oven" Mammoth

snipped-for-privacy@fluidwebz.com (TJ) writes:
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Get the Shadow Composites videos and do what you're shown on there. It works very well and you'll learn a lot more about making tubes and finishing too.
Chris

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My son is building a 38mm minimum diameter rocket which should also go mach. Similar to a Cirrus dart, only somewhat heavier (and longer). I think he said 7000' on an Pro-38 I.
He's glassed the tubing (he's gotten rather good at it). Using west system epoxy. (which does an awesome job without having to vacuum bag. But a BBQ rotisserie motor-based "lathe" makes it MUCH easier to spread).
Then the fins were attached to the tube (with a bead of 5min epoxy for quick set) and VCP fin guide.
Then he did a fillet job with the regular epoxy.
Now he's tip-to-tip glassing each fin pair.
Since each stage of glassing is at least two layers, this thing will be _strong_.
The fins are foam-core art board with a layer of 6oz glass (the tip-to-tip glassing adds at least another layer). I would expect the result to be stronger than G10, but lighter and probably more shock resistant/shatter proof.