Loc 4" Goblin. Jeeze, a newbie with ANOTHER Goblin build thread!

[Hooked On Rockets]

So, I've been working on rockets almost a year and a half when time allows and now I have some time so here is my build version of the Loc 4" goblin. I got this abot two weeks ago.

I'm new to building and very new to TRF....so please bear with me!!!!

Firstly, this kit is AWESOME! That 54mm MMT is just CRAZY (for me)...I, being limited to 29mm motors, CRAZY!!!

I tried to take as many pics to document the build, but of course I have missed some things that I wish I would have captured....but most of those were during filleting and priming....so not to critical...I hope
I also didn't get any photos of how I epoxied the chute loop to the upper CR.
I epoxied both sides of the lower washer and the lower side of the upper washer and some on the threads of the hook to lock that in place.

I've been primering the main frame this weekend and getting close to ready for paint!
Not sure exactly what paint scheme I'm gonna use yet...
But Now to the pictures!

 

[Hooked On Rockets]

Here's a dry mock-up....

NICE!!!!

 

[Hooked On Rockets]

Had a boo-boo from shipping....not a biggie, I have an idea.... More in a minute...

 

[Hooked On Rockets]

Gluing the 2nd fin on.... Notice the "rocket engineering" with the paper towel "rocket-holding-jig"!!! LOL

 

[Hooked On Rockets]

Here's the fin can with all the fins installed and fixing to epoxy the mid centering ring to the fins/MMT.
Just an FYI...the laser cut rings were s good bit crooked in relation to being plumb longitudinally, so I had to draw lines along the MMT to make sure that the fins were not crooked....(too crooked)....I searched on here for "Loc Goblin" and didn't find anything helpful....
And ironically, while at work I found a thread that had a build thread with this kit and had a great technique for mounting the fin can/CRs...I just found it too late...and I'm still having trouble finding it now. LOL

 

[Hooked On Rockets]

OK, here's my OVERBUILDING....I've installed some reinforcement rings to help secure the MMT to BodyTube.
I bought a coupler tube from Apogee (along with some rail buttons, more later about that) to make the reinforcements.
Couldn't find an uncut ring that fits the OD of the MMT so I made one. Here it is ready for glue and positioning.
I've added those in my OR file, which I'll post soon.....its still preliminary, not accounting for primer and paint.... Fitting the upper reinforcement on the MMT



Heres the reinforcement for the upper fin can CR

 

[Hooked On Rockets]

Got my fin can complete and added the fillets....this pic aint so good....sorry!

 

[Hooked On Rockets]

Now, here's where I added an internal reinforcement below the aft CR, I originally made one cut to the slots in the BT, but fitting it up and playing with installing the fin can assembly kind of wore out the cut section so I thought best to add the ring (cut from the coupler tube that I bought from Apogee).

 

[Hooked On Rockets]

Got my fin can complete and added the fillets....this pic aint so good....sorry!View attachment 375554

I forgot to mention that I used BSI 30 minute epoxy for most of this build along with BSI 5 minute for the non structural components...

 

[Hooked On Rockets]

Now for the fins....
first I ran a small bead of Loc-tite 5 minute epoxy along the fin roots for a "tack-fillet" to keep the body tube from flexing when I install the actual fillets using Rocket-Poxy and let that kick off for a day...

 

[Hooked On Rockets]

My first fillet set...Rocket-poxy-no dye added and I thought, "I should add some dye on the next ones...Dohhhh!
anyway....

 

[Hooked On Rockets]

Added dye for the next fillets not sure if it helped...some came out a little rougher than the first set above.....
with my poor eyesight and my poor lighting I shot a little primer on the front edge of the fin roots....to see how bad they look,
I decided that I could fix it when I prime the whole thing.... not great but not too bad!

 

[Hooked On Rockets]

Here, I shot some primer on the fins/lower BT still checking my fillets, I prefer to start my first coats of primer with Dupli-Colers' green self etching primer but I was out so I used Dupli-Color "Filler Primer".
My fillets are gonna need some work!!! LOL
I also forgot to seal my fin edges with CA before my first coats of primer so I sanded the bevels afterwards and applied the CA.

 

[Hooked On Rockets]

Another thing I forgot to mention is that I used rail buttons and spacers from Apogee rather than the ones that came with the kit.
They weighed in at a little over half of the weight of the Locs and it was easier to install the fin can since they are almost flush with the inside of the body-tube.

 

[Joe Rocket 97]

Etching primer is usally for bare metal

 

[Hooked On Rockets]

Now to the beginning of the finishing work....
I picked up a couple of cans of the Dupli-Color "Self Etching" primer and applied a couple of coats over the main body, then a couple of coats of the DC (Dupli-Color) red oxide filler primer (seen here).
I will follow up with a couple of coats of DC grey filler primer....and then a whole bunch of sanding!!!
To fill my tube seams, I Like to build up my primer coats with contrasting colors so I'll know when I get close to the actual body tube, which I really don't like to sand (it seems to cause a furred up mess LOL). I can sand down to the lowest color and not fur up the paper body tube!
Anyway, here it is in red oxide on the rotisserie I just built!!!

 

[Hooked On Rockets]

Etching primer is usally for bare metal

True that is, but my thought is, since I don't like to sand the paper body tubes, and as far as the plastic nose cones go, seems that it would help with adhesion of that first layer applied.

 

[Joe Rocket 97]

You would need plastic adhesion promoter for the nose cone

 

[Hooked On Rockets]

Oh, back to the shipping boo-boo here..

I ran a small CA saturation around the top of the tube EXCEPT where the boo-boo was...
Then I wet the boo-boo area with water and made a few passes with an iron.
Then, after letting it dry for a day I finished up soaking the top edge with CA and ran some over the boo-boo.
Worked very well, flattened it out enough that primer will make it disappear!

Here it is now....

 

[Hooked On Rockets]

You would need plastic adhesion promoter for the nose cone

I kinda saw something about that somewhere...any product suggestions?
I am kinda leery about the softer plasic nose cones.

SS

 

[grouch]

I've used the plastic adhesion stuff in the past, now I just rough it up then prime it. Don't see a difference at all. Mileage may vary of course.

 

[jd2cylman]

The other thing you can do is flame treat the nosecone. Use a propane torch and run the flame over the surface of the cone. Move fast enough that you don't melt the cone, but slow enough to warm the surface. Not my idea, but that's how I prepped my Goblin cone. The paint is still on...

 

[Nytrunner]

I love impromptu rocket jigs. You're getting a lot of mileage out of that toilet paper pack

 

[Joe Rocket 97]

Bull dog adhesion promoter

 

[Hooked On Rockets]

I love impromptu rocket jigs. You're getting a lot of mileage out of that toilet paper pack

LOL
That's ROCKET ENGINEERING!!!!
But just for accuracy on the "build sheet".....it's actually PAPER TOWELS!! LOL

Though I don't get much mileage of those lately...they disappear like they come on a roll or something!

 

[Hooked On Rockets]

Ok anyway...
I put some more filler primer on the NC, and a little more sanding and then a final coat of non-filling primer and some scuffing and it will be ready for paint....




I started sanding the first coats of fill-primer on the main body...though I thank I started sanding early, I would have liked to get a couple of layers of primer on it first....but I'm a little ready to get this one done!

It has the "leprosy" of the actual body tube paper exposed....
That will "fir-up" with the next coat of primer...gonna make more work...
and I KNOW better than to sand to early....but I did it anyways.... DOHH

I still need to detail sand the fore and aft fin fillet roots and block sand the fins.....but getting there as time allows...



SS

 

[Hooked On Rockets]

The other thing you can do is flame treat the nosecone. Use a propane torch and run the flame over the surface of the cone. Move fast enough that you don't melt the cone, but slow enough to warm the surface. Not my idea, but that's how I prepped my Goblin cone. The paint is still on...

Interesting....that is after sanding off the sprue and scuffing obviously.....do you apply the primer while still hot? I wouldn't think so....
But I would think that the heat would "melt away" all the work you did scuffing, which would eliminate the "bite" that the primer needs for adhesion....
just my thought...
Thanks...

 

[jd2cylman]

Interesting....that is after sanding off the sprue and scuffing obviously.....do you apply the primer while still hot? I wouldn't think so....
But I would think that the heat would "melt away" all the work you did scuffing, which would eliminate the "bite" that the primer needs for adhesion....
just my thought...
Thanks...

I'd have to find the thread, but I believe the heat treatment is before you scuff it...

 

[cwbullet]

Another Goblin thread? That is awesome..

 

[Hooked On Rockets]

Got my JLChute Release today.....
Some of the quickest shipping I've ever seen! Thanks J.B.!
Been playing with it...
This thing is AWESOME!!!!!
Wow, don't make sense to fly without it!!!!