Devilish Project (Go Devil 38 kit bash)

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OverTheTop
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Re: Devilish Project (Go Devil 38 kit bash)

Postby OverTheTop » Mon Dec 18, 2017 3:44 pm

I don't have the luxury of a 7:1 VK, but it really matters how much I bash the kit as to what I end up with :D

It is already significantly different. Only some of the parts are a starting point.

The intent is to think about a few things along the way and then do the same thing, but better, to the 54mm version :shock:
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Re: Devilish Project (Go Devil 38 kit bash)

Postby drew » Mon Dec 18, 2017 4:45 pm

OverTheTop wrote:I don't have the luxury of a 7:1 VK, but it really matters how much I bash the kit as to what I end up with :D

It is already significantly different. Only some of the parts are a starting point.

The intent is to think about a few things along the way and then do the same thing, but better, to the 54mm version :shock:


I only make the kit bash comparison because hand rolled CF airframes are significantly lighter (and therefore faster) than thin wall FWFG that I assume the Go Devil 38 kit uses.

Here's the OP for Simon and Andrew's 38. Look at the size of the thing!

https://forum.ausrocketry.com/viewtopic.php?f=56&t=1196&p=36640&hilit=EqNSwOw1myw#p36640
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Re: Devilish Project (Go Devil 38 kit bash)

Postby OverTheTop » Mon Dec 18, 2017 5:25 pm

Thanks for the post with the info. Nice. What was the launch mass, sans motor for the rocket?

I will be using thin-wall f/g tubing, but I will be shaving off mass wherever possible. Might not make it as far along as "Mach Madness", as I am starting from some heavier components (NC and airframe).

Currently looking at a pair of Ravens (four batteries) and a Telemega. If I can live without one altimeter I can save about 20 grams or so. Not sure if it is worth saving yet.
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Re: Devilish Project (Go Devil 38 kit bash)

Postby drew » Wed Dec 20, 2017 11:23 am

OverTheTop wrote:Thanks for the post with the info. Nice. What was the launch mass, sans motor for the rocket?


Great question! Sumo? Maybe you can finally lift the kimono on this project and share some vehicle details? :wink:
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Re: Devilish Project (Go Devil 38 kit bash)

Postby joeman » Fri Dec 22, 2017 2:56 pm

Hi OTT.

Thanks for sharing your project build on here. Looking forward to seeing it progress. Plenty to learn. Lots of fun!

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Re: Devilish Project (Go Devil 38 kit bash)

Postby Sumo310 » Wed Dec 27, 2017 9:49 pm

Thanks for the encouragement Drew... updated details on the 38mm rocket Dave and I built are here:

viewtopic.php?f=56&t=1196&start=90#p69369

Sorry for the hijack OTT.
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Re: Devilish Project (Go Devil 38 kit bash)

Postby kopius » Fri Dec 29, 2017 1:23 pm

OverTheTop wrote:That is the motor I am leaning towards currently.

OTT, have you considered the J510? https://ausrocketry.com.au/j510w-l.html
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Re: Devilish Project (Go Devil 38 kit bash)

Postby SpaceManMat » Sat Dec 30, 2017 8:14 am

kopius wrote:
OverTheTop wrote:That is the motor I am leaning towards currently.

OTT, have you considered the J510? https://ausrocketry.com.au/j510w-l.html


Looks like Aerotech is the way to go if you want speed in a 38mm J. CTI don’t build anything bigger that a 4 grain imax. I suspect there’s an upper limit on that rear closure somewhere round the 932N mark.
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Re: Devilish Project (Go Devil 38 kit bash)

Postby drew » Wed Jan 03, 2018 12:55 pm

SpaceManMat wrote:Looks like Aerotech is the way to go if you want speed in a 38mm J. CTI don’t build anything bigger that a 4 grain imax. I suspect there’s an upper limit on that rear closure somewhere round the 932N mark.


I'm not too sure about that. The J530 from CTI is a good candidate and is a 6GXL Imax motor. It sits between the J570W and the J510W in terms of both total impulse and length.
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Re: Devilish Project (Go Devil 38 kit bash)

Postby SpaceManMat » Fri Jan 05, 2018 9:52 am

drew wrote:
SpaceManMat wrote:Looks like Aerotech is the way to go if you want speed in a 38mm J. CTI don’t build anything bigger that a 4 grain imax. I suspect there’s an upper limit on that rear closure somewhere round the 932N mark.


I'm not too sure about that. The J530 from CTI is a good candidate and is a 6GXL Imax motor. It sits between the J570W and the J510W in terms of both total impulse and length.


Opps sorry meant vmax, I’m looking at peak thrust.
QRS: 124
AMRS: 32 L2 RSO
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Fastest Flight: Mach 1.55
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

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The Fincan Begins

Postby OverTheTop » Sat Sep 07, 2019 2:32 pm

Time to tickle this build along a little...

THE FINCAN BEGINS
A plug was machined to fit the inside of the airframe so the tube would not collapse when clamped. It was then chucked in the dividing head.
An adjustable support was made for the back end, using simple wood shapes and some ball bearings I had on hand. This can be used for other diameter airframes as well since I have made for some crude, but suitably effective, adjustments.

The job was adjusted in the mill so there was less than 0.001” of runout over about 300mm of length. Not too shabby. A mechanical center-finder was used to locate the center of the job and the DRO zeroed so machining could begin.
MillSetup.JPG


Since I only had one 1mm endmill I was a bit worried about breaking it. I did have about ten diamond burrs for my dental drill on hand. I could have made an adapter to put the dental drill on the quill of the mill, but I thought I would try the diamond burr directly in the collet. The belts were cranked up to full speed (which is still only about 1/200th of the dental drill speed :) ) and the slots milled out to the required gap for the fin thickness, minus a little bit. X-feed was set quite slow and the slots were machined. Came out quite nice.
MillingSlot.JPG
MillingSlot.JPG (230.54 KiB) Viewed 73 times



Fins were covered by masking tape to make sure I didn’t scratch the nice CF finish. The slots in the airframe were then lengthened (for the beveled ends) and gently opened out to the nice snug fit that I was after.
FinSlot.JPG


Here it is with dry-fit only.
DryFit.JPG


Now we use the time machine to travel nearly two years into the future, to get to my contemporary work. Yes, up till now it was December 2017 :shock: .

A CTI 38mm 6GXL case as taped, in line with where the fins will reside, with four layers of Kapton tape. This was to increase the size of the motor and effectively butt it up against the inside of the tube. That would let me butter up the fins and slots with epoxy and glue the fins in place.

The originally provided fin alignment jigs were not slotted for the larger fin thickness, so I was just using them to eyeball the alignment to be radial from the tube. You can see a steel rule with a hammer on top that I use to hold it in place as the glue cures. Accuracy should be a very small fraction of a degree on each fin.
GluingFinsResize.jpg


Step and repeat twice more. Fins are now glued on.

My current master plan has me adding fillets made of CF rod and then machining them to a concave shape. Materials currently on-order.

I hope I can actually get some more time to allocate to rocketry. Been a bit low on bandwidth lately :( .
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