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Formula 200 L3 Build Thread
#21

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(12-14-2015, 09:02 AM)dgreger Wrote: DREAGO, looks like you did the same thing I had to do. In running the threaded rod to the top CR having to drill one of the holes between the holes for the U-bolt. I messed with it for about ten minutes before deciding to do it that way!

Dave-Don,

I don't run the rod through the CR between the holes for the ubolt. I offset the ubolt so the rod end is free allowing me to more easily put on the rod nut. The ubolt plate needs to be considered..you could drill through this plate but I locate the plate away from the rod. I do install the ubolt plate as it's part of the ubolt strength. Most times the rods are left a few inches long so that I can grip the rod end with a plier when tightening the nut. Final step is to slice the rod flush with the nut using a dremel cut off wheel. Always have a nut on the rod  when cutting the rod..screwing the nut off after slicing cleans up the threads. Rod can be a bit spingy if you tighten too strongly so keep this in mind at the aft end since you intend to have your thrust plate removable.
Tom Cohen

MDRA...Maryland
MARS...Geneseo N.Y.
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#22
(12-14-2015, 12:14 PM)Tom C Wrote:  
 

(12-14-2015, 09:02 AM)dgreger Wrote: DREAGO, looks like you did the same thing I had to do. In running the threaded rod to the top CR having to drill one of the holes between the holes for the U-bolt. I messed with it for about ten minutes before deciding to do it that way!

Dave-Don,

I don't run the rod through the CR between the holes for the ubolt. I offset the ubolt so the rod end is free allowing me to more easily put on the rod nut. The ubolt plate needs to be considered..you could drill through this plate but I locate the plate away from the rod. I do install the ubolt plate as it's part of the ubolt strength. Most times the rods are left a few inches long so that I can grip the rod end with a plier when tightening the nut. Final step is to slice the rod flush with the nut using a dremel cut off wheel. Always have a nut on the rod  when cutting the rod..screwing the nut off after slicing cleans up the threads. Rod can be a bit spingy if you tighten too strongly so keep this in mind at the aft end since you intend to have your thrust plate removable.

Tom-Dave,
Interesting idea about cutting the rod from the back after the thrust plate is in place.  It may be hard to see but the threaded rod is clear of the u-bolt but not enough to pass the nut.  Last time I secured the rod a few inches inside the motor mount part of the body tube with vice grips so I could get a nut driver in the front.  That way the threads at the end weren't damaged.

Trying to get the fins on this week before we pack up for ESL 210.
NAR 98479 L3
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#23
Tacking in the fins.  I sanded all the shine off the fins using an orbital sander, plus sanding around the fin slots (easier now than later):

       

Test fitted with fin guides made from 1/4" plywood:

   

Fins are tacked in with 30 minute epoxy, and guides snugged up:

           

The rear centering ring is friction fitted while the epoxy sets:

   
NAR 98479 L3
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#24
Prepping for internal fillets.  I forgot to post these, but before the fins are tacked in a heavy fillet is applied to the front and middle centering rings to lock everything in place:

       

Also, I couldn't remember if I sanded the inside of the body tube (BT) around the fin slots, so time for a little remedial sanding with a sponge pad and aluminum angle:

       

Finally, wiped off with a tack rag (not shown), and an alcohol wipe down:

   

Ready for internal fillets now.
NAR 98479 L3
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#25
Making fillets.  This has been covered a 1000 times before, but here is my way.

Start with 1 pump of West Epoxy and Fast Hardener:

   

Add a heavy pinch of 1/4" chopped carbon fiber.  I guess this is about 4-5X what Wildman uses for injected fillets, maybe 10% by volume:

   

Stir in well.  The result is a seriously gooey hairball.  Perfect:

   

Add about 1 oz of West High Density Filler #404:

   

The result (shown in an earlier post) is like hairy peanut butter.  It sets like concrete. 

Spreading and smoothing tools:

   

To spread it I wind it on the dowel like cotton candy, and apply it with a twisting and pulling motion:

           

Dip the PVC smoother in alcohol and pull out the fillets:

       

Clean up with a paper towel dipped in alcohol:

   

Finally put the thrust plate on the back to ensure it will fit after the epoxy sets:

   

These aren't pretty fillets, but they are extremely strong.  Good for the inside.  Each one pump batch weighs 1.2 oz and it took 7 batches for the inside fillets.
NAR 98479 L3
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#26
External Fillets.  Not too many photos here, needed two hands to work.  West Epoxy + 404 High Density Filler.  About 1.25 oz of filler per pump of epoxy.  Using the same PVC pipe for the external fillets as I did for the internal.  The diameter is about 1".

Taped out:

   

Applied and smoothed out:

           

After curing, I'll apply thinned spot filler and sand smooth.
NAR 98479 L3
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#27
Applying the backing nuts for the nose cone coupler and AV bay 10-24 machine screws.  I'm using weld nuts.  Start by sanding both sides of the weld nuts down to the bare metal, and also sanding the body tube.  Also the machine screws are given a coating of grease to make sure I don't accidentally epoxy them into the weld nut:

           

I tack the nuts in place with JB weld:

       

When cured, I put a little more grease on the exposed bolt tips and apply a fillet of Rocketpoxy with some 404 thickener:

   
NAR 98479 L3
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#28
Making and installing Rail Button supports.  The unistrut buttons are backed up with T-nuts attached to 3/4" plywood blocks that conform to the inner radius of the body tube:

           

After tacking in the t-nuts, I cover them with epoxy with the machine screw installed and covered in grease:

       

Then epoxied into the body tube:

       

Finally, and probably not necessary, I applied a fillet of thickened epoxy:

   

Since I had some epoxy left over, I put some smooth blobs over the nose cone weld nuts so the shock cord can't catch:

   

Done with the body mechanical.  Next up will be prepping the AV bay.
NAR 98479 L3
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#29
Dreago
Since I had some epoxy left over, I put some smooth blobs over the nose cone weld nuts so the shock cord can't catch:
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I'm enjoying following the build ..... it makes it much more interesting to watch the flight at Red Glare in the Spring after I've seen you build here. No two people put a rocket together the same way...good job..
Tom Cohen

MDRA...Maryland
MARS...Geneseo N.Y.
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#30
(12-29-2015, 01:47 AM)Tom C Wrote: Dreago
Since I had some epoxy left over, I put some smooth blobs over the nose cone weld nuts so the shock cord can't catch:
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

I'm enjoying following the build ..... it makes it much more interesting to watch the flight at Red Glare in the Spring after I've seen you build here. No two people put a rocket together the same way...good job..

Thanks Tom, nothing special in this build I realize, just a lot of ideas I picked up from perusing all the build threads and talking to people like yourself at the launches.

Making the charge cups.  After blowing up a few PVC caps I was buying Blastcaps.  Since they don't seem to be on the market currently, I'm making mine out of copper pipe and end caps.  The drogue chute compartment will need 4-6 grams and the main chute compartment 6-9 grams.  I'm using 1" copper for the main chute compartment and 3/4" for the drogue chute compartment.  Each tube is about 1.5" long for reference.

Laying out the materials for the 3/4" cups (tube, caps, sandpaper, fitting brush, solder and MAPP gas torch):

   

Making sure the open end is fully deburred.  Wouldn't want to slice through an ematch wire:

   

Sand and wire brush off the oxide, apply a little flux on each part, heat with torch and apply a little solder.  Don't want to goop solder everywhere, though I always seem to do it anyway:

               

After cleaning off, center drill the end cap:

   

Then drill with 3/16" bit for #10 machine screw:

   

All four done, and the 1" caps laid out on the AV plate drill guide:

       

The large caps should hold about 18 grams of BP and the small ones about 10 grams.  Plenty enough for this design.
NAR 98479 L3
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