Estes Curvilinear #3231, Finished

I like squatty, stout rockets. This one is perfect for the schoolyard field.
I was expecting trouble with the fit of the tail ring but it slid in easily.








Here's the twins!
It also works well in the orange. The orange will probably become part of my active fleet. It could easily replace my old stretched Quest Cobalt (Orange) with Estes A8-3s and Quest A6-4 engines. The now retired Cobalt has had 16 flights since 2012.

Estes Curvilinear #3231, Build, Parts 12, Ring and Engine Mount Gluing

The rear ring is pretty tight, held in place by friction alone.
I did apply a drop of medium CA at the rear of each joint to lock it in place. The nose of the model was held down so the CA glue ran into the fin/ring joint.
Be sure the fins are lined up on both sides of the slot before applying glue.

Here I'm marking a glue applying dowel to place a ring of glue inside the body tube.
The rear of the engine mount tube and main air frame tube are both even when glued in place. The dowel is set beside the mount and a pencil line marked with the top of the dowel just below the upper ring.
On the right is the ring of glue around the top of the dowel.

Set the dowel in the tube up to the pencil mark. Roll the glue bead in the tube. Re-apply until you have a glue line all the way around inside the tube.

Slide the mount in place and twist until the engine hook is in line with the launch lug. Fillet the bottom ring and inside body tube joint.

Estes Curvilinear #3231, Build, Parts 11, Kit Name Decal

If you've followed the blog, you know I don't normally include the Estes name decals. Everybody at a club launch knows who sold the kit. The only time I use a company logo is on a OOP clone model, like a Centuri kit.

Notice the difference in the width of the kit decal against the decal on the face card. The face card decal (maybe prototype build picture?) isn't as long.

When I worked at the print shop I spent a lot of time on a phototypesetting machine. I learned proper letter spacing and how to set type on a curve.  

 

On the left, look at how the C and U but up against each other. The C isn't following the curve of the set letters.

The C was cut off and placed so it better followed the flow of the line. This decal lettering probably wouldn't bother anybody else, just me!

Estes Curvilinear #3231, Build, Parts 10, Nose Cone Decals

I didn't check the clearance of the black border on the nose cone decals. After soaking the decal I could see I cut right into the top circle of the white row!

Quick fix - just cut off the top white dot.

GOTCHA - Hold any decals (that have a dashed black border) up to a bright light. It's the only way you'll see the white ink before cutting it out and soaking the decal.

TIP: If you look down the rocket body sometimes you can use the fin reflection for an alignment line.










Here's the nose cone with the chopped decal in place.
Who'll notice and who cares.

Estes Curvilinear #3231, Build, Parts 9, Tape Reveal and C/G

The tape was pulled and the color separation was pretty good.

The ring was slid into place. The color separation is sharp between the ring and fin slots.

Here's why the engine mounts weren't glued in earlier. I have to find the center of gravity (C/G) of the model with 13mm engine mount in place.
With the 5/60 mount slipped in with an A10-3t engine, the balance point was 3 1/2" from the rear edge of the main tube.

The 18mm engine mount was inserted with a B6-4 engine in place. I doubt I would ever use a C6 engine in this rocket. Bits of cay weight were added and stuck on the outside of the nose cone until it balanced at 3 1/2" from the rear.
The total clay weight added to compensate for the 18mm engine mount was .16 oz.

Estes Curvilinear #3231, Build, Parts 8, Paint and Masking

White undercoats were sprayed.
On the right shows the fillet blobs after they are sanded. You don't have to take this sanding down to the surface, just knock down a little more than half.

I wanted to use the Rusto Metallic Silver on the body tube. Normally you would paint the body, mask to expose the fins and shoot the second color on the fins.
The Rusto Metallic colors can lift when the tape masks are pulled up. For that reason (and past bad experiences) you don't want to apply masking tape over the Metallic paint. I'll do this paint mask in reverse by painting for the fins first, then masking them off and spraying the body tube metallic silver.

I'm building two models in two different fin and nose cone colors. One will be in orange, silver and black, the other in purple, silver and black. The face card show the model with purple fins and nose cone.

The lower end of the model was sprayed with orange on one and purple on the other. Concentrate on getting a good coverage of the fins. The nose cone was sprayed off the model.

Thin strips of clear Scotch tape were set down the root edges of the fins.
TIP: To mask around the rounded leading edge, sett one side down first then roll the tape around the rounded leading edge. Lightly apply pressure on the tape edge with your thumb trying to get the best half circle you can.
Continue the tape line down the other side of the root edge.
This type of turn masking takes practice, you might have to lay down the tape a few times to get a smooth rounded seal around the leading edge turn.




Here's the other build, painted in purple. The camera tends to photograph purple as a dark blue.

Masking tape was set over the remainder of the fin.




Whatever orange or purple was over sprayed was hit with another white coat. The first coat of orange and purple didn't quite cover the color underneath. This white coat was lightly sanded after it dried.


The metallic silver was then shot.

Estes Curvilinear #3231, Build, Parts 7, White undercoat and Tail Ring Paint

The engine mount was slipped in with a painting wand in place.
A paper towel was rolled and stuffed into the back end to keep any paint out.
White undercoats followed.





The black Rusto Metallic paint is perfect for the tail ring.
After the rings got primer/filler and sanding a white undercoat was applied, then some light sanding with 400 grit.

Masking tape was wrapped sticky side out on the engine casing atop a painting wand. The rings were stuck on the tape and spray painted.





The interior edge of the rings were swiped with a permanent marker. About 3/16" of the inside edge got the ink.

Estes Curvilinear #3231, Build, Parts 6, Fin Gluing and Ring Fit

The CWF on the fins was sanded with 220 then 400 grit.

The root edges were sanded so any primer was removed. The area around the root edge were sanded a bit more than the fin faces for a good fillet bond.

The filler primer was scraped off and the fin lines re-drawn.

The trailing edges of the fins are even with the end of the tube.

After all four fins were glued on, the tail ring was test fitted. Don't glue on until after painting the ring.

I did have to use a folded over piece of 400 grit to clear the slots on two of the fins. Don't sand too much out of the slots, you want the balsa to fit close on the ring.

Estes Curvilinear #3231, Build, Parts 5, Tube Marking and Ring Fill

Finally, a kit tube marking guide that matched up when rolled around the tube!

This is the back end with the crimp. It'll never be seen under the tail ring. The back end of the inside got a wipe of medium CA.
The launch lug is glued in place directly in line with the engine hook.

Filling the tail ring inside seam? I did because I didn't know how much would be visible when it is glued in place.
(So you know, you really couldn't see the inside seam on the finished model.)

The engine mount was slipped on a finishing dowel wand for a coat of primer/filler.
Don't glue the engine mount in so you can compare engine mounts and the different C/G later on.

Estes Curvilinear #3231, Build, Parts 4, Fin Prep

Sorry about the lack of daily posts -
I'm visiting my Mom in California and have to do my Internet at the local McDonald's!
Mom doesn't have WiFi (and at 88 years old she doesn't want it either!)

The laser cutting was so clean, the thin tail ring slot was left on the sheet when the fin was removed.

The slot fit is very good on the tail ring, almost too good!
With the ring painted black off the model, the close fit slot will make a close, straight color separation.

The fin grain was filled off the model with one coat of CWF.
I folded up a strip of copy paper and slid it into the slot to keep the filler out when it was brushed on.
Before the CWF sets up, wiggle the paper so it doesn't get glued in place.

It had to happen . . .
There's not much holding the center strip on. Glue it on and sand some more. Luckily this break only happened on one fin.

Estes Curvilinear #3231, Build, Parts 3, Fixing a Body Tube Crimp

Here's the only picture I could find of the finished 18mm engine mount.
I was curious to see if the difference in weights would be close to the clay nose weight needed later on. It wasn't!

The 18mm mount weighed .85 oz. with a B6-4 engine installed.
The 13mm mount weighed .42 oz with the A10-3t engine.

I'm building two kits.
One of the body tube ends had a small crimp. It shouldn't hurt the strength of the model especially if I put it on the bottom, hidden by the tail ring.

The nose cone was slid into the crimped end for strength in the next step.
A small pool of medium CA glue was set onto some scrap cardboard. A Q-tip was dipped in the CA and rubbed on the crimped area but clear of the nose cone shoulder joint. (I didn't want to glue the nose cone in.)

Before the glue sets, quickly rube over the glued, crimped area with a hard, smooth burnisher. You should be able to smooth out a slight crimp by molding the wet tube. The nose cone shoulder underneath lets you press fairly hard with the burnisher.
Remove the nose cone so it doesn't get glued in the tube.

Estes Curvilinear #3231, Build, Parts 2, 18mm Engine Mount

Here's the parts for the 18mm mount. I'll be doing my replaceable Kevlar mount on this one.
Hang onto the kit's 13mm mount. You'll need it to figure out the Center of Gravity from the original 13mm design.

The 20/60 centering rings are from BMS and cut from black Letramax board.
After punching out the engine hook relief holes, the tips were cut off to square off the sides.
Directly on the other side is the Kevlar tube holes, leave these as is.

On the left is the lower ring with the larger engine hook slot.

On the right is the upper ring. There is a very small partial punch to go over the top of the engine hook.

The inside of the centering rings were a little large for the BT-20 engine mount tube.
To bring down the inside diameter a ring of glue was applied and allowed to dry. This little bit of glue gave a good friction fit over the BT-20 tube.

Estes Curvilinear #3231, Build, Parts 1, Parts

Here's another kit from the recent Estes clearance sales. Why build a kit from a sale? I would think many blog readers would have also picked this one up and it's waiting in their build pile.
Parts are of good quality. There turned out to be a few turns along the way.
I really like the design, except for one thing. The only recommended engine is the A10-3t. With any luck (and a bit of nose weight) I'll be able to fly it with 18mm A8 and B6 engines.

Parts of interest:
The decal sheet has white on it which is hard to see on the white backing paper.
The laser cut balsa is very clean, especially the slots for the ring tube.



That ring tube is very heavy walled. I thought it might be a BT-70 like the old Estes Sprite.

It's actually a 2" diameter tube like you would see in the Pro Series II models. (So far, this is the closest I've gotten to real Pro Series II parts!) A standard tube wall is shown on the left. The Curvilinear tube is on the right.

Estes Curvilinear Background

When I first saw the Estes Curvilinear it reminded me of the old Sprite design.
Only 75 cents in 1969! 

It used the old Series III short engines, 18mm X 1.75" long.
The rocket was only 5.3" tall.
The tail ring was an RT-70 at .7" long.
Balsa sheet was BFS-40, 1/8" thick.

Semroc makes a BT-30 based Sprite kit using 13mm T engines.
The Tumbleweed from Fliskits also uses T engines but is BT-5 based.

This one used tumble recovery. Here's some recovery suggestions from the instructions.


In the original Estes Sprite kit, fins were cut out of 1/8" balsa, no laser cut parts here!
I remember that fin cap piece being hard to get right. The fin pattern layout didn't give much balsa if you screwed one up.






"Curvilinear". . . Where did that name come from?
I looked it up:
Curvilinear definition: "Consisting of or bounded by curved lines."
Well, it's bounded by the tail ring I guess.

I don't know if the Curvilinear design was based on the old Sprite or not. But, it sure reminded me of that little rocket.