Semroc New Goblin Kit Pics

Lawrence (doswonk on TRF) posted pictures of his Semroc Goblin he just received got from ERockets. To see the post - CLICK HERE





















Hats off to Randy Boadway for bringing back Semroc kits!
But . . . in the picture on the right -
That's a Alpha style "K" nose cone, not the original BNC-55AO nose cone.
I'm not trying to nit-pick. Inventory and supplies do run out.
The original Goblin nose cone is longer and very distinctive.

Semroc Goblin Finished

 

This was a standard build, sometimes I enjoy putting together a classic.

In the lower left picture, notice the 20/50 engine mount adapter. It trails below the body tube and end of the fins.

With this adapter removed, the end of the engine hook extends longer than the trailing edge of the fins.

The old Estes kit didn't stand on the four fin tips, but wobbled on the end of the engine hook.

Semroc Goblin Build Part 11 Decal Tips

After the tape was removed, you can see the rounded leading edge mask.

The decals in the kit are very close together on the sheet.

You can save a little work by leaving the bats right over the Goblin name.
Leave one bat to the left and one to the right.
These two decals will back each other up on either side of one yellow fin.


The way the fin angles are cut, it's hard to visually line up the "Goblin" baselines.
With the model standing on a shelf, the type baseline should be parallel with the flat base of the shelf.

I used a CD case set down the body tube and fillet "valley" to get a square reference line.

When setting this decal, try to do it visually first. Then check it with a square corner like the CD case. You might be surprised by how crooked the decal is.

Semroc Goblin Build Part 10 Masking for the Black Fin

This picture is a little hard to see, it was shot at night.
I wanted to show one way how to get a rounded leading edge mask.
This description is for the tape piece on the right.
The Scotch tape was place on my sliding patio door.
Freehand with a sharp knife, a small quarter circle was cut to the right, clockwise from position 12 to 3.
From where you stop cutting at the 3 o'clock position, a straight line is cut down the tape.
I used a felt pen to mark the tape so you could see it better.
The tape strip on the left shows the cut strip of tape being removed.



This is the Scotch tape piece in place going down the fillet.
When you mark the tape with a black marker it's easier to see the tape placement.
At the front of the fin you can see how the two rounded ends fit together.







Masking tape goes to the outside of the Scotch tape and a grocery bag covers the rest of the model.

Semroc Goblin Build Part 9 Paint and Decal Plan

If you are a real stickler to build like the designer intended, take a look at the Goblin Assembly drawing.
In the drawing the model is drawn on a horizontal.

Very few people notice the "3" decal is really laying on it's side!

The rounded "right" side of the 3 is turned 90 degrees clockwise so it lays parallel to the trailing edge of the fin. In the drawing it reads normally, but imagine the rocket standing upright, the "3" would be on it's side.
The decal sheet in the parts picture shows the "3" the way Wayne Kellner designed it to sit on the fin.

There is really no wrong way to place the decal. When the Goblin first appeared in the 1972 Estes catalog, the "3" decal read normally, not on it's side.
In every catalog after that, you can't see the "3" decal!

I know, it's a moot point and trivial. Still, interesting and a little bit of Estes history.

Semroc Goblin Build Part 8 Glue and Fillets

The fins were tacked in place with white glue.

Before the fillets were added, the pencil lines were erased with a white eraser. I didn't want to apply glue over the pencil lines and have them show up under the paint.



The Semroc Goblin re-issue kit has a 3/16" diameter x 3" long launch lug.

The original Estes kit had a LL-2A launch lug. The LL-2A lug was 1/8" diameter x 1 1/4" long.

To build it like my original Goblin, the single LL2A lug was cut in two.




The lower lug is centered between two fins and flush with the low end of the body. The upper lug is glued 1 3/4" from the top of the body tube.

I'd thought about using epoxy for the fin fillets

I ended up using white glue.

These pictured fillets were built up in five coats.

You can actually get a little fillet buildup with white glue, it just takes a lot of extra coats.

Every succeeding coat dries faster than the one before it.

Semroc Goblin Build Part 7 Nose Cone Grain Filling

Enlarge the picture at the right and you can see the brush strokes.

On a nose cone, brush from the tip down forcing the filler into the grain.
When you get about half way down the nose cone, the grain becomes longer and more apparent.

Just like on the fins:
On the lower half of the nose cone, brush first with the grain.

While the filler is still wet, brush against the grain. In the picture you can see the brush strokes on the lower half going at an angle, against the balsa grain.

 

Before filling, the nose cone shoulder got a wrap of masking tape. The tape edge went right up against the shoulder lip.

After the CWF has dried, remove the tape but pull it away from the lip as shown.

If the tape were removed going around and not down, you might pull some of the filler out of the grain at the shoulder.

Semroc Goblin Build Part 6 Fin Grain Filling

Many use Sanding Sealer to fill the balsa grain, I prefer thinned Elmer's Carpenter's Wood Filler.

The picture has been flipped to show the proper orientation of how the fin will glue to the body tube.

The leading edge is at the top, the root edge is at the left.

Brush on the Wood Filler first WITH the grain, concentrating on getting the filler into the grain pores. You are almost pushing the filler into the grain with the brush. It's easier to get the thick filler into the grain if you brush with the grain direction first.

While that filler is still wet (don't add any more filler to the brush) then brush AGAINST the grain. This will again push the filler into the grain.

In the picture you can see how half the fin was brushed against the grain going from the middle up. the other half was brushed from the middle down. Don't forget to brush filler onto the edges.

If you've mixed water and filler to the right consistency, it should look like the picture above. There will be shallow brush strokes after it dries.

I usually will brush filler on one side and the edges and let dry while I do the one side of the other three fins.
When all four fins has been coated with filler, I go back to the first fin and fill the other side.

NOTE: If you are filling thin 1/16" thick fins, the CWF can warp the fins.
When you coat the other side and after it dries, the warp should go away.

Semroc Goblin Build Part 5 Balsa Sanding & Filling

Everyone should know how to round the edges of a fin.
For those who might not, this is just one way to do it.
If you don't have a sanding block, pick one up at a hobby store. Preferably one that allows you can change sandpaper easily.


If you were to follow the original Estes instructions:
On the Goblin, only the leading edge and trailing edge of the fins are rounded.
The root edge and outside edges remain square.

For a consistent round edge use a sanding block with medium grit 220 grit sandpaper.





Using the block gives a more uniform pressure on the balsa and the square corners won't get rounded.
Look down the leading and trailing edges to make sure you have them sanded to a half circle.






Rough form the rounded edges with the 220 grit then switch over to a small piece of 400 grit, set into the soft pad (inside of the first joint) of your thumb or index finger.
Use the 400 grit to knock down any squareness or edges on the rounded edges.

Semroc Goblin Build Part 4 Engine Mount Install

This is both finished engine mounts.
The D engine mount at the top has the thinner RAH-5055S rings.

The 5055 rings in the original Estes kit were thicker like the 18mm adapter shown below.



The D engine mount is installed in the rear of the 55 tube in Step 15.

Again I used the flat side of my sanding block to be sure the BT-50 engine mount tube and the BT-55 main airframe tube ends were even.

Note I haven't glued the fins on yet.
I've found it easier to mark the fins alignment lines after the mount is in place.

You don't have much time to center the engine hook between two fins and get the tubes flush before the glue sets up.
With this method you use a wrap around fins marking guide.
Rotate the guide until the engine hook is centered between two fins, then mark the four fin alignment lines.

Semroc Goblin Build Part 3 Gluing Rings & Blocks

Instead of running a line of glue around the engine mount tube and sliding the rings in place on the glue -
The Semroc instructions have you place the centering rings, then add the glue. Semroc gets it right again!

This insures the rings are at the correct placement instead of laying down the glue and trying to get the ring on the mark before the glue sets up.

I like to take it one step further.

The rings are set next to the measured pencil lines.

Small drops of thin CA glue are applied at the joint to lock the ring.

Don't use much glue, you are simply tacking the rings in place before adding the white glue fillets.

Instead of just pressing the engine block into the top of the engine mount tube, use something flat like a square block of wood or as in the picture, the flat side of a sanding block.

This insures the engine block is flush with the top of the engine mount tube.






After the engine block glue is dry, sand the top square, over both the top of the engine mount tube and engine block.

Semroc Goblin Build Part 2 Engine Mount Rings

Even though the instructions have you make the two engine mounts separately, I built them at the same time.

Step 9 doesn't mention cutting a notch in the RAH-5055S for clearance over the engine hook.
The picture shows the gap above the hook without the notch in the ring.






I went ahead and cut a notch in the ring.
The fit of the forward ring was perfect.






The fit of the pre-notched rear ring was a little loose.

To build up the inside diameter, a ring of white glue was ran around the inside edge.
After drying, this was all it took to get a good friction fit.

Semroc Goblin Build Part 1 Parts

This build is a classic, a Semroc reissue of the Estes Goblin kit #702-K-55.
I remember getting one as a free kit about 1971. It was later added to the catalog line up in 1972. The price was $2.50.

It featured a long nose cone, square block fins and a goofy black decal sheet. I remember thinking how much thicker and stronger the BT-55 body was compared to my other BT-20 and BT-50 models.
Back then I never flew mine with the new D engines. I used the EM-2050 engine adapter with 18mm engines.
This Semroc kit comes with an 18mm adapter.

Semroc calls this one part of the Magnum Series. The word "Magnum" was used by Centuri to describe their D engines. I don't remember Estes ever calling the D engine birds with the Magnum moniker.

Parts are all first quality.
The split 2050 centering ring is the cleanest straight cut I've ever seen in a model rocket kit.
The launch lug is 3/16" diameter X 3" long.
The original Estes kit used a 1/8" X 1 1/4" long or the LL-2A. Semroc has you glue the lug on in one piece. The Estes kit had the lug cut in two and was glued at the top and bottom of the BT-55.

The AR-5055 engine mount centering rings are a thick card stock in the Semroc kit. The older Estes rings were more like the 2050 wound rings in the enclosed 18mm engine adapter.



The decals look great!
They are printed close together on the small sheet. This'll require some careful cutting.