Tuesday, August 31, 2010

Freedom 7 Build Part 3 Capsule

I can assume all four of the capsule wraps on the pattern sheet are the same size and would now fit the nose cone correctly.

I cut out the Freedom 7 wrap but cut the glue tab a little longer than the cut line showed. I just felt it was a little too small for gluing. I knew this could effect the final fit on the balsa nose cone, the Dr. Zooch parts and wrap fits are very accurate.

After gluing the tab area, I used two 1/2" dowels to "roll" the two sides together. The horizontal dowel was rolled (not rubbed) over the glue tab and seam. The vertical dowel simply gave me a hard, round interior surface to roll against. The dowel is much harder that my fingertips. Using a interior dowel helps form the shroud round at the glue tab.

TIP: When making a shroud, it takes very little glue on the tab to hold it together.

Here's the first capsule wrap in place - three more to go!
Notice the wide overhang of the wrap, it's supposed to be that way. The overhang will match the upper tank band wrap to be added later on.

Freedom 7 Build Part 2 Capsule

The wrap sheet has four different capsule wraps to choose from -
The Freedom 7, Liberty Bell, plain Mercury Capsule and the gray and orange boilerplate version. I close the Freedom 7 skin.
I didn't cut out the Freedom 7 wrap at first. I cut out the boilerplate I wasn't going to use - for practice.
This way I could check out the fit and the glue tab length.

I went ahead, glued the tab and let it dry. It was slid over the nose cone capsule. It fit over the top but when it was pulled down the top it split open.

Here you can see the recovery compartment area (above the pencil line) has a slight taper.

I sanded down the taper and tried a dry re-fit using a second wrap I didn't want for the final model.

The seam and printed areas matched up well.

Freedom 7 Build Part 1

The parts from the new Dr. Zooch kit -
The Mercury Redstone Freedom 7

Dr. Zooch had already had the BT-60 based mercury Redstone kit. I'd built one before, it was a lot like the old version of the Estes Redstone. Not the plastic capsule and tower, but a tower you made out of dowels.

When finished, this model will be 13 3/4" tall.
The tower is a combination of vertical dowels and wire for the diagonal cross members. If you've built the Zooch Saturn 1B kits, you'll be familiar with the construction. The lower end is a lot like the Jupiter C kit.

I did my typical prep with the Dr. Zooch kits. I inventoried the parts and scanned the wrap sheet.
One of the first Zooch kits I built was was the Ares 1. I tried the method of applying white glue to the outside edges of the wrap and rolled it around the body tube. I had wrinkles and the wrap didn't quite match up on the other side. I tried to remove it and it ruined the wrap and body tube. Wes (Dr. Zooch) was nice enough to send out another wrap. So now I scan the wraps so if I need another, I can simply print on up.

Solo launch 8/31/10

Back to the schoolyard for some small, but still fun stuff.

First up was the MMX Cloud Hopper. All was great until apogee when the ejection charge blew his head off. I found the body easily and after a little walking I saw two teeth (on the nose cone head) sticking up out of the grass.

The MMX Downscale Break-Away flew great. All four segments separated and fell close by.

Now for the interesting launches - 35 year old MPC Minijets.
I'd flown old Estes and Centuri engines, but never the old MPCs. I tried them last time using the old MPC igniters with no luck. This time both MPC engines had Estes igniters in them.

The Carded A-20 Demon had a great first flight. The 1/2 A3-3m engine (MPC used the "m" designation, Estes uses the "t"). I didn't put in engine blocks so I could use these longer 2 1/4" Minijets.

Everything worked just as it should. Those old engines really put out a nice smoke trail, newer engines seem to puff out a little smoke right before ejection.

The model tail slid a little after apogee and popped the streamer. This would be a perfect rocket for the Estes 1/2 A3-2T, a second less delay than the old MPC.

Last up was the Cherokee T carded downscale with another MPC 1/2 A3-3m. Great altitude and a walk even with streamer recovery.

As I was walking back to the launcher, the automatic sprinklers turned on!
Luckily they were just outside the reach of my open range box and launcher.

Monday, August 30, 2010

The Next Build

Tomorrow (after a quick schoolyard launch) I'll start a new build thread on the Dr. Zooch Freedom 7 Mercury Redstone.

This model has just been released, built around a BT-50 mainframe.
Be ready for a comprehensive build, I'll be concentrating on the capsule and tower.

If you haven't tried a Zooch kit before, you are missing out on a great experience. It's almost like building a scale kit from the "Golden Years" of model rocketry.

Downscale A-20 Demon Build Part 6 Trim Plates

Wayne Kellner, designer of the Demon, did some great work.
The fin plate trim pieces were a clever design element.

Before cutting them out, score the fold down the center dashed lines as before. These are printed on thinner paper so go easy.

Again, use the dull tip of a butter knife and straightedge. Don't cut through the paper, just make a pre-fold crease.

Don't hit these with the spray adhesive, on pieces this small it's easier to use white glue.
With a straightedge and sharp knife, cut out the plates. There are extras on the print.
Fold them down the crease you made.

Simply apply a thin coat of white glue on the back and center them into the root edge of the fin/body tube joint. Tweezers will make this easier to hold onto.
These plates will also strengthen the fin joint.

Nothing left on this one except to glue the yellow square around a launch lug then glue that into the root area of a fin.

The original big Demon had two lugs, one in the front and one in the rear. On a model this size, a forward lug really detracts for the look of the model. A single rear lug should be fine.

The fin alignment lines on your PDF print were moved slightly rearward from the picture here. Your model will be that much closer to an actual downscale than this first prototype.

It's Finished!
This next launch it should fly with a 35 year old MPC Minijet engine.

Downscale A-20 Demon Build Part 5 Body Wraps

Some builders have luck with just white glue around the backside of a wrap.
I'm not that lucky.

I prefer to use spray adhesive, it gives you a second or third chance at repositioning the wrap. I never seem to get it right the first time.

This Duro Spray Adhesive can is old, maybe over 10 years old. It never seems to run out.

The picture shows all three wrap pieces ready to be sprayed. The cardboard backing was lightly sprayed and allowed to set up for a few minutes. The wrap pieces were placed lightly on the sticky cardboard, just enough to hold them down for spraying the backs.

A pencil line was drawn down the body tube and the first upper wrap was applied, lining it up down the line and with the top of the tube.
The second, longest wrap was started immediately below that using the bottom of the first wrap as a guideline.

Finish up with the third wrap.

The BT-20 tube was long to begin with, I cut off the end and sanded it square with the end of the third bottom wrap.

Be ready - The end seams will lift!
This is a compromise with using the spray adhesive. By using the spray adhesive you have the chance to re-position the wrap. If you apply white glue to stick on the wrap, you get one-shot to get it correct. Once it's down, you won't be able to move it.

Place a few drops of white glue on the corner of your work area. Dip just one side of you hobby knife into the glue. Push some glue under the lifted wrap the run the blade under the wrap edge to smooth out the glue.
Notice that I wrote: Dip just on side of the blade into the glue. This will keep the glue only under the one side of the wrap. Try to keep the glue off the printed outside surface.

Sunday, August 29, 2010

Downscale A-20 Demon Build Part 4 Fins

White Glue has been applied and smoothed out on the underside of the printed area.

Here the fin is placed over the straight edge of the cereal box cardboard.
You should set down the leading edge fold first, making sure the entire length of the fold is on the edge of the cardboard. Follow by smoothing the sides of the printed overlay.

Once again I'm using the Sharpie pen to smooth out the surface.
TIP: Lay a piece of clean paper over any printed area before burnishing. This way there is no chance of rubbing off of the print or transferring any dirt from the burnishing tool on your work.

Watch for any glue that may be pushed out the sides and wipe clean.

Lay the glued fins in a fold of wax paper and set in a heavy book for drying. Let them dry overnight.
TIP: If you are pushed for time, you can use an iron set on "Cotton" - "Dry" (no steam) and iron over the fins to dry-set them quicker. Use a clean piece of paper over the fins when ironing.

Only one side of the fin has a "hairline" cut guideline and the words "Root Edge". Cut the fins from this side. The other side of the fin is printed oversize to insure color coverage.
Cut out the fins using a sharp razor blade and straightedge, cutting through all three layers of the ply.
Apply white glue (not yellow glue, white glue dries clear) along all the outside edges of the cut out fin. After it dries, lightly sand over the glued edges with 400 grit sandpaper. Be careful and don't sand off any of the printed sides. Re-glue, let dry and sand again.

Here the Sharpie pen is used to (slightly) round over the outside and trailing (cut) sides of the fins. Don't do this on the root edge, you'll want that edge square and sharp.

This style of carded fin will have a rounded leading edge, square root edge and slightly rounded outside and trailing edges.

Downscale A-20 Demon Build Part 3 Fins

This is the cereal box cardboard used for the interior of the 3-ply fins.
The printed side should be roughed up for best adhesion. You only have to hit the printed side with some 220 grit sandpaper. I don't sand deep, just scratch it up a bit to remove some of the printing.

Be sure you dust off the surface before gluing on the fin overlays.

Before cutting out the fins score the fold lines. In the picture, I'm using just the tip of a butter knife, just making a line indent. (Use a straitedge for a true line, the straitedge is not in the picture so you can see the indent line itself.) The tip of a butter knife is not sharp or serrated. All you want to do is "push" a straight indent line into the cardstock.

Many kit instructions will have you cut halfway through the cardstock with a sharp knife. This is unnecessary.

For most models, this step will give you a very sharp fold line without the worry of cutting too deep or through the cardstock.

After making all fin center lines, cut out the fins oversize. Use scissors and cut a little larger than the outside the printed area.

Now the center lines can be folded over using the indent line you made and burnished flat with the back end of a Sharpie pen.

Saturday, August 28, 2010

Downscale A-20 Demon Build Part 2

The fins on the Demon don't overhang the rear of the main body by much.

I made a 13mm engine mount with the engine hook overhanging the rear of the mount by 1/4".

When dry fitting the mount, the model wouldn't stand upright on the fin tips with the engine hook in the way.
So a second mount was built without the engine hook, I'll just have to friction fit the engine. Those 5/20 centering rings were cut from a empty casing left over from a Semroc kit.

After the centering rings were glued in place, I realized I didn't include the Kevlar shock cord!
I'm old school and tend to fall back on the old thinking sometimes.
I decided to drill a hole in the centering ring to allow the Kevlar to be tied on.
An awl was used to get the hole started. The hole diameter was widened with a small twist drill.

I went to my stash of scrap Kevlar and didn't have anything under 150 lb. strength.

The 150 lb. Kevlar is 4 strand so I undid the wrap and used two of the strands. Simple twisting opened it up to separate the cords, re-twisting got me the two strand piece I wanted.

No knot was tied where it looped around the mount, it's simply wound under itself three times and tightened down. With a white glue fillet over the top, this Kevlar isn't going anywhere.

TRIVIA: Kevlar (insert Dupont Trademark here) was first developed as a tough replacement for the steel belts in car tires.

Downscale Carded A-20 Demon Part 1

I just finished up a downscale version of the Estes A-20 Demon.

The kit #K-58 was sold from 1971 through 1979.

The original was BT-55 based and stood 24.5" tall and was flown with a D12-7. 18mm engines could be used with a 20/50 adapter.

This Carded BT-20 version stands 14.5" tall. It can be flown with 13mm or 18mm engines - your choice.

One of the great design elements of the Demon was the printed metallic body wraps. This set the rocket off and gave it a military or sounding rocket vibe. The fin reinforcement plates were also die-cut from the chrome sheet.

In drawing this one up, I tried to duplicate the feel of the metallic wraps in shades of gray.

The build thread will follow this first post.
This downscale is built in the Greg Poehlein carded rocket style. You print out the PDF on your printer.
Cut out the "skins and wrap around the body tube - this time around a BT-20.
No painting except for the nose cone!
The balsa nose cone is available from Semroc.com. It's catalog number is BNC-20AM

The PDF is available now at Wayne Hill's Rocketry Blog at:
Click HERE
Scroll down, almost to the bottom.

Or, email me at oddlrockets@bellsouth.net and I'll send you the PDF - it's free!

Friday, August 27, 2010

Upcoming Projects

I got 4 new rocket kits today!
Along with a new rocket design for the Odd'l Rockets line, I'll be busy for the next few weeks.

One of the kits is the new Dr. Zooch BT-50 based Mercury Redstone Freedom 7.
The blog build will highlight the capsule and tower construction.

I also have an old MPC Martian Patrol kit which would be a kick to build and fly.

I'll continue to build and fly what is now available and occasionally reach back in the old kits box.

Rocket Manual For Amateurs Book

This book has quite a history.
The Rocket Manual For Amateurs by Capt. Bertrand R. Brinley.

Originally published in 1960, this was the second edition from 1968.

As the pictures show, the book contains full instructions on how to make steel pipe rockets filled with zinc and sulphur propellants. Other propellants are discussed.

This is not a guide for "basement bombers", but I'm sure it inspired a few accidents as most kids wouldn't follow the guidelines in the book.

"Safety" is fully covered including how to make a bunker, illustrations show hard hat wearing figures tamping down the propellant.

You can make a wind tunnel using two vacuum cleaners and a bicycle tire rim is turned into a make-shift centrifuge. Other instructions show how to make a spring scale accelerometer.

I bought this book in 1970 from the Johnson Smith Company, the same place that sold the "Ventrillo" and X-Ray Specs inside the front cover of comic books.
Johnson Smith was also the first place I bought rocket engines through the mail. It doesn't sound like much today, but in 1970 you couldn't get model rocket engines sent into California.
They made a mistake, I got MRI A3-2s!

You can see in the first picture, in the upper left hand corner, the price was cut off. This wasn't done by me. The folks at Johnson Smith decided to raise the catalog price and probably had older copies with the lower cover price.

This book is for sale if anyone is interested. (Sorry, sold on Ebay 2013)

Big Girtha Finished!

Here's the Big Girtha finished and ready for the next N.E.F.A.R. launch in Bunnell, Florida on September 11.

I didn't get into the fin masks this time, my methods have been explained before. I wanted to concentrate on the tape trim stripes.

I was happy with the way this one turned out.

Lessons learned -
  • I haven't made a scratch baffle in a while, I forgot how easy they were to make.
  • I don't paper the fins very often, next time I'd do another primer coat and sand on the fins.
  • While I can see why some prefer papering fins, I didn't feel I saved any time. They did require covering, trimming, filling the edges, priming, sanding and spray painting. But considering the core is balsa, they feel much stronger!

Thursday, August 26, 2010

Big Girtha Decal Part 21

It' still raining outside so I jumped ahead and applied the decal.

I wanted it centered between the lower red and upper barber pole sections. Another black tape strip was temporarily applied where the red paint section would end.

The middle white area was measured and a pencil center line marked.
The decal was measured and the center was found at the left side of the letter "I" in Girtha.

You don't have a lot of time when applying decals, I'd rather find the center marks now than try to slide around a decal (this long) on the model. Remember, home printed decals are more likely to crack when pushed and stretched.

Here's the decal in place.
I was happy with the match of the decals red shade and the red tape stripes. To be honest - I took the decal with me to Home Depot when I bought the electrical tape and spray paint to be sure the red shades matched.

Big Girtha Trim Tape Part 20

As shown in an earlier post, I stuck tape strips on my glass patio door and cut them to the right width. Looking at the catalog picture, I'm guessing it's about 3/8" wide on all the strips.

The top stripe is standard black electrical tape simply wrapped around the top of the tube.

The second white stripe isn't tape, it's just the painted white body tube. I left 3/8" blank space between the top black and the next red stripe.
Enlarge the picture and you can see the pencil line below the horizontal red stripe.

This is my center mark for the diagonal red barber pole lines. All tape stripes are cut long. This gives you more to hold on to when placing it. It'll take a few tries to get the line straight and smooth.
TIP: When using vinyl or electrical trim tape, don't stretch it when laying it down. It'll shrink back and could leave gaps after you trim it off. You're better off leaving a bit of overlap where pieces meet. When done correctly, the overlapping tape won't be noticed.

Here's the other red barber pole lines in place from pencil mark to mark.

Notice the piece of paper rolled and taped aound the tube. This is a simple guideline used when laying down the horizontal stripes. It helps keep the taped lines straight and matching up when you get around the other side.

The barber pole stripes were trimmed back a bit and the ends were covered by two more black stripes, one on top and one on the bottom.

Big Girtha Build Trim Tape Part 19

I'm trying to capture the Big Bertha paint scheme from the 1969 Estes Catalog. Not an exact copy - just the general feel.
That barber pole at the top will be interesting to replicate.
From the picture, it looks like there is four or five red stripes spiraling up the tube. I'm going with four stripes.

The lowest end of a single strip starts directly above the top of the fin's leading edge and finishes to the right, directly above the top of the next fin.

After the entire model was painted white, I drew faint pencil lines down the length of the body using my aluminum angle. The bottom of the angle was lined up with the fin leading edge tip. Four lines were penciled on the upper 5" of the body tube.

First up, I'd probably mask the fins and paint the lower third of the body red as in the picture. Then I'd follow with all the trim stripes. But Central Florida has rain - all day. I can do the barber pole trim now and spray when the weather is better.

Vinyl Trim Tape Tip

When I visited both Estes and Centuri in the mid 1970s, I was surprised when I saw the actual models used in the catalog pages.
Some didn't look as good close up and in person.
The Estes and Centuri catalog models show a lot of airbrushing.

I did ask about how they got some of the finish effects.
Difficult masks were sometimes just colored (or sprayed) paper cut with scissors and glued to the model.
Electrical tape was also used for trim lines.

Any thin lines are easier to make with these tapes - without masking.
Here's some I just picked up at Home Depot for about $3.50.

Big Girtha Build Masking the Engine Mount Part 18

This was a strange mask.
First, small squares of masking tape were set sticky side out against the inside walls of the main tube with tweezers.

Pieces of paper towel were pushed into all the recesses of the mount.

A 1/2" dowel with an expended engine was locked into the mount for a painting wand.

More tape was applied over the top to insure no white spray could get into the black mount.
I know - a lot of work for the mount to be black.

Wednesday, August 25, 2010

Big Girtha Build Nose Cone OOPS! Part 17

The 1969 Estes catalog showed their Big Bertha paint scheme. It was one of the few full color pages in the catalog.
The nose cone was simply painted red.
I masked off the shoulder and sprayed it with Rustoleum Painter's Touch Gloss Apple Red. No problems.
I decided to add a coat of RPT Gloss clear.

When I checked it after drying, the clear coat had wrinkled and dulled the surface. I don't know what caused this, it should be compatible, both paint cans were the same brand, from the same factory.
It could be a combination of Florida humidity and my laying the clear coat on too thick.
I'll sand it back and shoot it again.

Launch Lug Fillet Bubbles

Every modeler has trouble with bubbles in the glue fillet surrounding the launch lug.
The angle of the lug fillet area is much deeper than a fin root/body tube joint. Bubbles seem to show up after the lug fillet is dry.
The simple solution is multiple glue fillet layers.

The picture shows the Big Girtha launch lug after five fillet applications.
When that first fillet is applied, smooth it out with your finger and watch for the bubbles to form.

TIP: When the glue is still very wet, pop the bubbles with a toothpick. You'll just have to try it, a toothpick tip will easily pop the bubble. Using the tip of your knife to pop a glue bubble will take too many tries. It's much harder to pop a bubble with you knife tip.
If the glue is still very wet, the hole where the bubble was will close up on it's own.
I know five fillet passes sounds like a lot, but each pass dries faster than the previous one did. Each new glue layer is much thinner than that first deep fillet.

Big Girtha Build Gluing the Engine Mount Part 16

The engine mount was glued into the main body with 1/4" of the engine tubes extending past the end of the main tube.

TIP: Note on the back of the main tube, the fin alignment line is extended back over the rear lip of the tube. The fin's root edge will totally cover the alignment line. This is another alignment point allowing you to center the fin right above this mark.

Make note of the two engine tube positions in relation to the fin alignment lines. With the mount in this rotation, it's easier to insert and remove the engines.

With the fins glued in place, you can see the position of the engine hooks between the fins. A little pre-planning makes your flight prep much easier.