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Formula 200 L3 Build Thread
#31
Making AV Bay Lids.  1/8" Pilot holes are drilled using drill guide, and then drilled for the various bolt sizes (5/16", 1/4", 3/16", 1/8"):

       

Components added (top and bottom):

       

Four 1/4-20 threaded rods complete the connections:

   
NAR 98479 L3
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#32
This is how I finish fillets so they are glass smooth before painting.  I use Bondo spot putty (the red stuff), a dowel, sand paper and sanding sponges (3M Pro-pac).  The spot putty sands and feathers easily.  It smells bad, I use a respirator.

Tools for preliminary sanding:

   


The dowel is slight smaller in diameter than the fillet tool.  Sand with 180-220 grit just to knock down the high spots:

       

Then use a coarse Pro-pac sponge to feather the edges and smooth things out:

   

The result, a fair smooth fillet with some pitting (due to the 404 filler I believe), and a occasional low spot:

       

I use the spot putty to fill the little pits, fill in low spots, and fair out the curves at the fin tips:

   

First spot fill any big low spots with full strength putty:

       

Then thin the putty to a latex paint consistency using acetone:

       

Spread liberally on each fillet and allow to dry:

       

Sand down using the coarse and fine Pro-Pac sponges.  Virtually all the spot putty is sanded off:

       

Any remaining low spots get a second full strength smear and touch sanding:

   

Here an example of a finished fillet from another rocket.  Looks good and doesn't take that much time to do:

   
NAR 98479 L3
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#33
First pass fillets were a little rough, so made a second coat:

       
NAR 98479 L3
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#34
Ejection testing day.  We waited out the two day spitting rain to get this done.  Here are the links to low res videos (sorry i couldn't figure out how to post videos):

Main - https://youtu.be/7dD4bIVX2HU
Drogue - https://youtu.be/ExAcJK3DYaw

I'm satisfied with the first pass.  The parts separated easily carrying a fair amount of momentum, and just about stretched out the 35 ft shock cord.  Laundry came out cleanly.  I'll upsize the backup charges to 150%.

A few pictures too:

               

Ready for sanding and the paint shop
NAR 98479 L3
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#35
Looking good!
John S.
NAR #96911
TRA #15253
MDRA
Level 1, 2014-Mar-15 -- Aerotech Sumo, H133BS
Level 2, 2014-Jun-21 -- Giant Leap Vertical Assault, J240RL
Level 3, 2016-03-12 -- MAC Performance Radial Flyer, M1101WH, 13,028 feet
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#36
(01-11-2016, 12:33 PM)Bat-mite Wrote: Looking good!

Thanks Bat-mite!  Will you be at MDRA this weekend?


Sanding.   Sanding is boring.    Here are a few pictures to prove I really did it.  Since the tube was so large I broke out the orbital sander and finished up with a medium pad:

           


I've had issues with Primer adhesion to fiberglass, especially if the top coat has a tape job, so for this rocket I'm being extra careful to get all the fiberglass shine off using 220 grit.  Plus, being careful with cleaning the surface before priming.  Hopefully, this will do the trick.
NAR 98479 L3
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#37
Since the last post I've been applying primer.   It takes about 32 oz of primer for 3 spray coats.  The weather has been bad here so progress has been slow.

Here are some stands I build to hold both halves of the rockets.  For the body tube the smaller discs slide into the 4" motor mount and for the AV/Payload/Nose Cone section, the discs slide up into the AV coupler.  They hold the rocket very steady.  The bases are 2" MDF.

               

First coat applied.  I'm using Duplicolor Specialty Primer/Surfacer (lacquer based) and an inexpensive HVLP gun from HD with a 1.4mm tip.   Got a couple small runs around the nose cone which will sand out easily.

       

The little divot near the fin fillet in the detail photo gets filled with spot putty and sanded out.  What can't be seen in the photos is unfortunately I wound up with a light stripe where the primer was put on too thin, so I'll have to put a second coat on.  After letting it dry for about a day I dry sanded everything with a 320 grit pad. (Unfortunately no photos for this step).

After cleaning with Prep-all spray and a tack cloth, second coat finally applied:


       

Next good weather window I'll apply black base coat and the first pearl coat (black pearl).
NAR 98479 L3
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#38
The paint stands....nice design...
Looking forward to seeing it launch in Maryland soon.
Tom Cohen

MDRA...Maryland
MARS...Geneseo N.Y.
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#39
(01-31-2016, 03:09 PM)Tom C Wrote: The paint stands....nice design...
Looking forward to seeing it launch in Maryland soon.

Thanks Tom, still hoping for first flight in March.
NAR 98479 L3
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#40
Electronics.

There are two independent sleds.  I'm using Perfectflite CF Altimeters and an Eggfinder GPS transmitter.  Here's the wiring diamgram for each altimeter.  To meet the requirements for NAR Level 3, I bypassed the switch input on the CF and put the screw switch in series with the battery:

   

And the finished sleds, which we've been using on our 6" Der Red Max:


   

Hoping to get the base coat on this weekend.
NAR 98479 L3
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