Thursday, March 31, 2011
I used a Quest MicroMaxx (#9528) nose cone.
I've drawn a pencil line around the nose cone where I want it to split.
Rather than just pushing a knife through from the shoulder forward, I usually pre-score the line with a knife around the perimeter of the nose cone.
Sometimes balsa won't split right down the grain line. Cutting a shallow line down the pencil line will guarantee a clean split down where I want it.
Notice I split the nose cone wider than needed, to one side of the center line. This insures a better fit against the body tube.
Wrap 400 grit sandpaper around the body tube and sand the nose cone back to match the tube contour. After sanding, here's the fit in the half body tube.
The front of the nose cone is rounded to the correct shape shown on the Centuri Magnum Jayhawk plans. It's shown next to the original Quest MMX nose cone.
Wednesday, March 30, 2011
California had strict laws about rocket engines coming into the the state.
That first three pack of MRI engines were 18mm, A3-2's.
Some engine casings had the dates printed on them before or after production.
He said he could look it up in some older records. I said that wouldn't be necessary.
This might be when FSI added 18mm engine production.
The largest sale of MPC rocketry merchandise was to KMart for $670,000!
GM (General Mills the parent company of MPC) thought the MPC model rocketry sales should be in to $40 million dollar range per year. Sales were 1/10th of that, at $4 million. Still, pretty respectable.
During the space race, rocketry sales went up 10% every year.
In 1970, MPC exceeded Estes in sales!
Yeah, I know, all I need is another launcher.
This gives a rough visualization for the flare tunnel size and diameter.
After going through my scrap body tubes and nose cones, I picked the Quest MicroMaxx MMX2 body tube (#9528) and nose cone. (#19990)
The body tube was cut in half lengthwise down the entire length of the tube using a sharp knife and an aluminum angle.
After cutting, sand the back square and straight on a block.
Then sad the cut tube edges again against the body tube with 400 grit sandpaper. This matches the cut tube sides to the curvature of the body tube.
Tuesday, March 29, 2011
Check it out HERE
I hadn't seen this many old plastic kits in a long time. Sure, some are outrageously expensive, but if you've got to have it, in some cases it's cheaper than Ebay.
Under model rockets I found:
Holverson Silver Hawk $26.00
Estes Pathfinder $26.00
Estes Swat $28.00
Estes Skydart $450.00 !!!
Estes Nike Apache $46.00
Take a look at the listings under "Spacecraft Missiles". Lots of expensive plastic model conversions there!
I actually had the best time looking over all the old plastic kits. Before I got into rocketry I'd probably built 100 plastic models. but they just sat there on the shelf.
Model rockets, on the other hand - MOVED!
Here's both tapered canards.
The root edge profile is on the left, the outside edge taper is on the right.
The outside of the fin is narrower than the root edge thickness. I'm planning on gluing the canards to the nose cone, not below on the body tube. These will have to be painted and attached after everything is painted.
Monday, March 28, 2011
The rudders had a different taper front and rear. The outside leading edge was only tapered facing the outside (one side) to just over 0.10". The trailing edge had a narrower taper of about 0.08"on both sides.
The pictured rudder on the left has just pencil lines. The right rudder has been sanded.
This side view explains it better. The fin on top shows the trailing edge taper on both sides. The front leading edge (to the right) is tapered on just one side.
I tapered the main fin leading edge 0.20" from the front on both sides. This wasn't an actual scale measurement, this is a semi scale kit. On this version I used the T.L.A.R. method. (That Looks About Right)
The before fin is on the left, the tapered fin on the right.
The rudders had a different taper front and rear. That's covered on the next post.
Sunday, March 27, 2011
This was not my best day for stability!
First up was the Downscale MMX CLOUD HOPPER. For the first time out of a dozen or so launches, it veered to the south and landed 100 feet away. I've got no explanation for this, it's always been stable before!
Here's a new downscale of the BIG BERTHA sporting the 1969 catalog paint scheme. Flight was good with a 1/2A3-4t engine. There was a slight coning or spiral during boost. Be sure to add the recommended nose weight if you download a print and build this one.
My Eric Truax PATRIOT wasn't stable with an old MPC 1/2A3-5t engine. It went straight up for 100 feet, then tail slid before ejection! I'm not blaming the design, it flew great before. Maybe I had a bad engine. Heck, this MPC Minijet was only 35 years old.
My downscaled A-20 DEMON was the best flight of the day. I must have got 425 feet on a A3-4t engine. On landing I had a popped fin and a "smiley" dent in the nose cone. The dent I can't explain, the shock cord is plenty long.
The FlisKits HONEST JOHN never fails, except when you forget to add flameproof wadding! The streamer was a melted blob, but recovered without any damage.
The Odd'l Rockets BIRDIE with an A10-3t. I hadn't flown my Birdie in quite a while. Stable, true and indestructible.
Saturday, March 26, 2011
The fin is set against the body tube and a reference line is drawn to fit the shroud. Start sanding with a block, constantly checking the fit of the added balsa piece.
Now I'm getting close. You should only be sanding down the added piece from the tail cone down.
When you get to this point, switch over to a finer grit of sandpaper and check the fit more often.
This is about as close as I'm going to get.
You could keep sanding, but run the risk of taking off too much of the root edge making the fin smaller. Just get it as close as you can.
Friday, March 25, 2011
Over the years, the Big Bertha paint pattern has changed. This one is from the 1969 Estes Catalog.
I remember this catalog page well. It was one of the few full color pages in that year's catalog. Most of the other rockets shown were airbrushed and printed as a duotone. (two color print)
On the other hand, the Big Bertha was an actual photograph of a finished rocket. It really stood out against the other products.
Bob Harrington has already made a carded "Mini-Brute" version of the Big Bertha. This version is BT-5 based and stands 7 1/2" tall.
Many of my downscales have a "skin" you print and wrap around a BT-5 or BT-20. This makes the model stronger than a cardstock rolled tube. It's also easier to fit a standard nose cone in an actual body tube. Sometimes a hand rolled tube can have slight variations in diameter.
Instead of spray adhesive, this time I used a Glue Stick to adhere the wrap around the body tube. I might be on to something here, the finished results were good.
I have built Bob Harrison's version a few years back and have flown it many times with MicroMaxx engines. I wanted to downscale this one to fly with the 1/2A3-4t engines I recently bought from the ScoutStuff.com sale.
These pictures are of my first draft. The available PDF has had some subtle changes made to better match the catalog picture. The changes were made after setting the finished rocket beside the catalog page.
If you've never built a carded rocket, you are missing out! I'm always surprised by how strong the laminated cardstock fins are. And, no painting - except for the nose cone.
Open Rocket says it'll get to 190 feet on a 1/2A3-2t engine.
With a A3-4t engine it could reach 485 feet.
You can download and print the body tube skins and fins at Wayne Hill's Rocketry Blog HERE Scroll down all the way to the bottom.
Print two copies of the PDF - The first print on 24 lb. paper for the body tube wrap.
Make a second print for the fins on 110 lb. card stock
Or, contact me at firstname.lastname@example.org and I'll send you the PDF!
This will get you close to the slightly upscaled Centuri version.
The engine mount / shroud assembly is glued into the main body tube.
After test fitting the three shrouds, I got a great fit to the BT-50 body tube.
Mr. Bob did a great job of upscaling the main fins to this slightly larger BT-50 sized model.
But, the laser cut fins supplied with the kit won't match the added boat tail.
We'll tackle this in the next post.
The engine block is glued flush with the top of the engine mount tube.
The older Centuri instructions have you apply glued to the tube and slide the centering rings over and onto the glue.
I wouldn't do it this way. You might not have the time to get the centering rings in the right position before the glue starts to set up.
Dry slide (no glue!) the stacked centering rings into position, just until they support and keep the card stock shroud in a round shape. Too far down and the rings will bulge out the card stock.
Once the rings are in the right place, then simply run a fillet around the joint of the top ring.
This will be plenty of glue to keep the rings in the right place.
Thursday, March 24, 2011
Like in the Centuri instructions, the engine mount tube is glued in flush with the bottom of the shroud.
Wednesday, March 23, 2011
It's 10 1/8" tall and the body diameter is .736" or a BT-20 size.
This is an Eric Truax design available HERE
Scroll down and click on Eric Truax's Patriots - DPILEGGI
Sorry, this is the best way I found to get the link.
I picked the version with the yellow top. This paint scheme was never on the real Patriot, it's just something the Estes folks came up with.
You can make a nose cone out of card stock, but I went with a balsa cone.
The fins are called "Fast Flight" air foiled fins.
It's an interesting way to glue the outside skins over a internal card stock support.
I didn't install the rear shroud, I had some problems making it. The mount was glued in with the motor mount tube flush with the end of the main body tube.
I've flown it with 1/2A3-4t engines. Open Rocket says it got to 207 feet. With a A3-4t engine it'll get around 532 feet.
Tuesday, March 22, 2011
Monday, March 21, 2011
In my case - it's a lot of luck.
I don't take launch pictures at the monthly section launches. I can't get close enough and my camera only has a 4X zoom.
I leave those lift-off pictures to the guys with the good cameras with faster shutter speeds.
When launching at the nearby soccer field, I'm usually alone or "Lone Wolf Launching". But, I am closer to the launcher and might get a shot right after ignition.
I had to develop a coordination of the left hand launch controller and right hand camera.
The picture shows how I would position my left hand. This is a newer Estes Controller.
- Set your shutter speed for a fast setting and turn your camera 90 degrees for a "portrait" frame. This'll give you a taller picture and a better chance of capturing the rocket going up the long rod.
- My left hand index finger is pressing down the Safety Key to get a Continuity Light.
- My right hand holds the camera. My digital camera requires you to press the shutter button down halfway so the camera can lock on the desired object.
- Keep holding the camera shutter button halfway down.
- Countdown and press the launch button on the controller with your left hand thumb.
- When you hear that first "hiss" of the motor ignition, press the shutter button down all the way and you'll hear the click of the exposure.
It's not easy to coordinate this the first few times.
I guess all those years of accordion lessons are finally paying off.