PML AMRAAM - 3 build

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Jul 25, 2009
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I got some more work done on this project too.

I have the forward CR epoxied in place and the next step is getting the aft set of fins mounted. Then the aft CR and the Hamr KS system for motor retention.

Either this or my repaired (V-2 Lawn Dart) will be my Level 1 rocket.

Here is my link to my previous question on this build.

Now my next round of questions.

The milled slots in the QT are just a bit 1/32-1/64" for the fins, however the fins have square edges, the fins are G10 fiberglass, stuff I have never worked with.

-1- Can you sand the G10 with out damaging it? If I sand the leading and trailing edge round, they should fit nice in the milled slots.

-2- What should I use to seal or prime the G10 material?

-3- What should I use to prime the QT prior to paint.
treat G10 as you do fiberglass/epoxy. (because thats what it is) you can sand and shape it no problems. Whatever way you prime fiberglass is the same for G10. Qt is plastic based.Sand, Sand, Sand, Sand before you glue to it. same with G10. But 2 coats of primer and some 320 wetsand and you are ready for paint.

If you have not flown a piston before, remember the piston requires less ejection powder. I used too much ejection powder, and received some damage:

Ben is correct, 320 sandpaper everything. Wash the the G10, plastic nose cone, and QT with soapy water as well.

Make sure that wherever a part comes into contact with QT it is very heavily sanded [60-80]grit. Such as centering rings to airframe [interior] ,fillets on fins to airframe, launch lugs etc. [exterior]. Epoxy will only bond to a roughed up area, not like paper or phenolic where it can soak in.

For a neat job....tape on each side of the fin slots 1/2 in. then do your heavy sanding. The tape will protect the rest of tube from heavy scuff marks and be easier to paint.

When doing the epoxy fillets if you have some filler, thicken the mixture and it will hold it's shape. When the epoxy reaches it's leather stage [ beginning to harden, but not yet fully cured] you can remove the tape and excess epoxy on it, making for a nice neat job and much less sanding.

The pics should help. small tube was surface mounted fins, but still taped before sanding to keep from scarring tube.

It is much easier to sand the fillet area before installing the fins also.

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Sand the heck out of the G10 and quantum tube before gluing - the only way to get a really good bond with those materials is to have a nice rough surface to glue to. It won't harm anything.
In answer to your 3 questions.

1 Yes you can round over the edges of g-10. I regularly put sharp bevels on my G-10 fins. It is fairly hard to sand so a heavy grit is best used to shape followed by finer one to remove sanding marks.

2 and 3. Prime QT and G-10 with any high quality primer. I prefer Duplicolor and Rustoleum Painters Touch, but there are many others. The extremely smooth surfaces demand a little bit different technique than paper or phenolic.

The paint or primer will want to run fast so many light fog coats will work better than 1 or heavy which will want to run.

After a few fog coats dry, the following ones will have something to "bite' onto.
Well its been a while, but between the holidays, killing bambi,
work and chasin' kids to soccer (indoor) games. I have finally,
in the past few weeks, got back to the bench and did a little
work on this project.

I got all the fins on straight, the motor retention epoxied on,
sanded every surface prior to applying epoxy. The piston is
assembled and moves smoothly inside the QT. All the motor
adapters are assembled and fit just right.

The only things left are the altimeter mounting and painting
the beast.


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Nice. When do you think it'll fly?

I found with mine that an H123 or 148 makes a good lowish altitude flight (~1200-1500 feet), while the I211 and 284 are a lot of fun for a bit more kick (the I405 screams :D).
Nice. When do you think it'll fly?

Now that's a heck of a question. Better is, when will it be finished...

This rocket got shelved for almost 2 years now with my new hobby
bench set up I dug it out and started painting it today. (I have made
a vow to myself to finish all my started projects/kits before opening
another one. I am including my father/son projects in that too... :rolleyes:)

I am trying a new paint a very good friend of mine suggested, he is a
gearhead and is into painting cars as one of his hobbies. Also the paint
shop recommended it for all plastics and fiberglass.

So my AMRAAM 3 is the guinea pig on this one.

Anybody have any experience with this paint/coating system?

DuPont Vinyl Color

I dug out the old Badger Airbrushes on this one. It seemed to spray
well and did dry very fast. I ordered some fitting so I can make use of
the shop air and not the expensive canned propellants.