Porthole Tube Fitting - Tip

For the new ROBOT prototype, I needed to fit short tubes, glued horizontally to the (vertical) main airframe tube. 

These are a like the "portholes" on the old Centuri Skylab model, only larger in diameter. 

To see the Centuri Skylab: CLICK HERE

Wrap some 220 grit sandpaper around your main airframe tube.

Sand the tube end against the sandpaper with a back and forth motion, to the left and right. Sand in a straight line.

Try holding the smaller tube still and moving just the larger tube with the wrapped sandpaper.

On the left, the curve sand is about half way through. More sanding is needed until - 

You get the best fit with no gaps.

The outside layer skin will tend to fold under.

Lift out with a fingertip and lightly sand off with some 400 grit. 

 

Here's a good fit of the Robot head on the neck tube.

This technique rarely comes up, but could come in handy one day.

Estes Black Star Voyager Build, Part 5, The Upper Tube Assembly

The top tube/ring assembly has the bottom ring flush with the low end of the tube. 

The upper ring is recessed 1 11/16" below the top end of the tube.

The instructions have you apply a glue ring and slide the centering ring in position. Good luck with that, the ring will spin and probably end up crooked in the tube.

I applied the glue ring using the top edge of a dowel.

Notice the tape ring set at 1 11/16" from the top.

Apply a ring of glue around the top of the dowel. 

Use the tape ring as a depth guide as you roll the ring of glue onto the inside of the tube.

Used the flat end of a ruler to push the ring into position. 

The square end of the ruler helps keep the ring flat as it is slid into the glue.

Check around the perimeter of the ring making sure it is flat and the same distance from the top of the tube.

You can apply a glue fillet using small glue drops applied using a Q-tip.

Estes Black Star Voyager Build, Part 4, Tubes & Centering Rings

There are six centering rings used in the build.

The ring with the notch was already glued onto the low end of the engine mount.

Before freeing out the rings, the center pieces (Parts FF) were removed and stored in a zip lock bag.

TIP: One of my tubes had bends in one end. 

Use one of the flush mount rings to reform the round tube and push the dents back out.

Sorry, these last two pictures are out of order.

1. Apply a thin ring of glue just inside the edge of the tube.

Press the ring even with the end of the tube shown in the  picture below.

2. To get the ring faces flush with the ends of the tubes, press the rings just inside the tube lip using the flat side of your sanding block.

In the above right side picture above: 

3. I'm applying an interior glue fillet using a Q-tip taped to a dowel. 

Apply a drop of glue to the Q-tip, drop down inside and spread the glue drop into a fillet.

Semroc Wac Corporal Build, Part 10, Fitting The Tail Cone

I'm using my old Fin Tool (Sorry, they aren't available) to mark the body tube. I want the shroud joint seam hidden under a fin root edge. In this case the seam and engine hook are on opposite sides.

The shroud is glued onto the lower ring and the first ring of the two center rings.

Lightly form the shroud edge by "molding" it into the wet glue underneath. For now, I'm only molding the low, smaller side.

Dry fit the engine mount into the tube.

TIP: Slide in a turn the mount and shroud until you find the best fit against the tube.

Mark the best position with a pencil mark on the tube.

Now you can apply some glue inside the tube and around the exposed middle centering ring. Slide in and turn the mount until the pencil mark lines up with the shroud joint.

Form the wider shroud edge as before, rolling the burnisher over the tube and shroud joint.

This will make for less filling later on.

The raised shroud overlap can be sanded down a bit. Just lower the thickness a little, not too deep.

Semroc Wac Corporal Build, Part 9, Fitting The Tail Cone

The kit supplies one tail cone shroud printed on cardstock. I rarely get a good fit onto both tube diameters with one shroud.

I scan and copy at least three of them onto 110 lb. cardstock. Assemble all three - one of them should have the best fit.

Do plenty of dry test fittings for a smoother final look.

One shroud on the left is a poor dry fit, both ends are a bit wide.

On the right, one of the other shrouds and a better fit. Both the middle centering rings have been dry pressed into the wide end. The second ring is outside the shroud top and gives you an open edge for gluing and a slip fit of the ST-11 main tube. 

The lower ring is glued in place, even with the end of the motor mount tube.

I use the flat face of my sanding block to press the ring even.

TIP: There was still a very slight gap in the small end of the shroud. I wanted to increase the outside diameter of the low ring.

I applied a thin line of wood glue. Smooth and even it out using a fingertip on both sides of the glue ring.

After it dries, run a finger around the ring and you'll feel high and low areas. Some 400 grit will take down the high spots.

Semroc Wac Corporal Build, Part 7, Forming The Tunnel

 

I had started forming the tunnel when I had worked on the build before.

Sand the underside curvature by wrapping 220 grit around a body tube. Sand straight up and down motions.

TIP: You'll get a tighter fit if you sand the inside contour on a smaller diameter body tube. The kit tube is 1.17" diameter. I sanded the underside of the tunnel on a slightly smaller .976" diameter BT-50 tube.

Here's the side of the tunnel before shaping the end.

Sand the angle diagonal first.

Round off the ends. 

Round off the long sides.

Here's a good fit of the tunnel on the body tube.

Estes Black Brant XII, Kit # 9723 Build, Part 14, Detail Hatch

Use the extended lines on the full size drawing and transfer them onto the balsa detail pieces.

The same as the long tunnels, 

Draw a pencil line down the center.

Using a rounded end dowel,

Press a "starter" trench into the balsa. The slight rut will help keep the piece straight on the body tube. 

Wrap some 220 grit around the tube and sand in a straight line up and down.

On the right side picture, you can see the sanded curve in the underside. There is still some of the flat bottom left. Sand until the curve is complete from side to side.

Here's a good fit of the hatch piece against the body tube.

Estes Black Brant XII, Kit # 9723 Build, Part 13, Tunnel Fit To Tube

You should sand a curve into the bottom face of the tunnel for a tighter fit against the body upper tube. 

Start by drawing a pencil line down the center from end to end.

TIP: Press a "starter" curve down the center pencil line using a rounded dowel end. This slight indentation will help you keep the sanded underside curve straight.

TIP: One trick to getting a good fit on a tunnel is to wrap sandpaper around a smaller tube than the one it will end up on. Example - If the tunnel will be glued to a BT-60 tube, sand the bottom curve with sandpaper wrapped around a BT-55 tube. 

Here's the before and after fit of the bottom of the tunnel.

The outside of the tunnel was rounded off using 220 grit on a  sanding block for the rough shaping. 

400 grit rolled under my fingers finished off the rounding.

Wolverine Phoenix AIM-54A, Fix!, Part 4, Peeling & Squaring Up

This is the 4" extension glued 2" over the coupler.

If I cut through just the tube I can still use the original coupler.

On the left, the outside layer of the tube is carefully peeled off.

On the right, the coupler is starting to show. I was surprised how most of the coupler didn't have much glue. On the original build - after sliding the tube segments together, the glue was pushed towards the bottom.

The coupler was 4" long, 2" extend out the bottom.

Little bits of glue still remain towards the low end. This was sanded clean with 220 grit on a block.

The lower cut above the fins was sanded flat using a block.

This low end can be squared up - the upper part can't with the coupler in place. I tried to get as straight a cut as I could.

Estes Maxi-Brute Honest John (Kit #1269), Part 10, Spin Nozzles Units, Part 2

Mentioned in the last post - 

The curved top and bottom will be sanded through first.

On the right, the curved edges are trimmed off leaving the straight sides. 

The straight sides are trimmed off with a sharp knife and straight edge. 

Sand and clean up the straight sides with a sanding block.

Do some test fitting on the low nose cone section.

In the top picture, there is still a gap on the straight sides. This tells me I've got more sanding to do on the 220 grit wrapped around the lower nose cone piece.

Here's a better fit, all the way around the piece.

The spin nozzles will be glued on (later) with liquid cement against the molded lines around the nose cone base.

Estes Maxi-Brute Honest John (Kit #1269), Part 9, Spin Nozzles Units, Part 1

Score around the raised spin nozzles leaving about a 1/16" edge. Bend and crack off the sides.

Hang onto the larger scrap pieces. You might need them for patches on the fin edges. Anytime I've worked with vacu-form parts before, I've needed patch plastic.

Looking ahead - 

The instruction illustration shows a spin nozzles being glued in place. The drawing shows a flat edge border around all sides of the spin nozzle piece.

That's not how they end up after sanding in the bottom curve.

I taped some 220 grit sandpaper around the low nose cone piece. 

Go back and forth in a straight line (here going left to right, right to left) over the sandpaper.

The two side curves will be reduced first, the straight top and bottom edges are reached last.

Estes Maxi-Brute Honest John (Kit #1269), Part 3, New DIY Centering Rings

I made four centering rings to double them up.

All four were stacked for sanding and fitting.

On the left is a good slip fit of the rings in the main BT-80 body tube.

Two sets of two rings will be laminated and glued to the main tube at the dimensions in the instructions. Not yet - For right now I'm prepping parts that will be needed for the build. 

This may have been the 1/8" thick balsa piece supplied in the original kit to make the scale launch shoes. It is water stained and will be replaced.

The instructions have you assemble them out of 1/16" and 1/8" thick balsa.

Looking ahead at the complexity of the assemblies - It'll be much easier to cut and assemble them out of smooth basswood. Balsa grain would be difficult to fill.

Odd'l Rockets F-18 Hornet Development & Build, Part 8, Canopy Fitting

Take it slow when working with vacuform pieces. 

This applies to the vacuform parts in the Estes Saturn V, Saturn 1B and the Odd'l Fighter Jet canopies. An extra 10 minutes of careful cutting and sanding will lead to a great fit and strong body tube bond.

   

The border of the canopy has to be cut off before fitting to the tube.

To better see the recessed edge, draw around the base with a ultra fine point Sharpie or ball point pen.

With a new sharp blade - 

SCORE around the line. Don't try to cut through with a single pass.

With your score cut halfway through the plastic, flex the plastic down the cut line until the border plastic breaks off.

At the lower right, it says "Score and break lines." Note the lines at all four corners. 

It helps to cut these outside lines to as you are flexing to break the pen line edges.

This illustration is from the kit instructions.

Set some fine sandpaper around the BT-50H body tube. Note the pen lines are still visible. These will end up being sanding off.

Go back and forth in a straight line down the tube over the sandpaper.

 
Here you can see the pen marked edges getting very thin and starting to come off. About the time all the pen ink is gone you should be getting a good fit on the body tube.

Don't glue the canopy on yet. 

It will be glued on after spray painting and decals are applied.

Quest Falcon #Q1009 Build, Part 10, Name Sticker

Under the Falcon beak is another sharp inside cut.

I would do the same as on the rear of the sticker - don't cut into that inside corner. Round out that sharp corner and scrape off the ink line.

Some of the fins get star stickers.

Cut inside the dashed lines. Note the inside corners are slightly rounded off.

The stars are pretty well centered sitting right on the molding line. You'll have to visually center them from the sides.

The upper wrap sticker lines up with the top edge of the body tube.

Like all the others, wet the tube and dip the sticker into a dish of water to allow lifting and repositioning. 

The nose cone shoulder needed two wraps of masking tape to better fit the body tube.