Building Back to the Beginning - Scout K-1

[DavidQ]

I decided to go back to the beginning, and start scratch building from the Estes K-1 until I get done, or give up. So, here's a build of the Astron Scout.

The special feature of the Scout is that it is a tumble recovery, by retaining the engine casing but letting it shift backwards. This is to shift the center of gravity behind the center of pressure, causing it to become unstable. This way, it simply tumbles to the ground. It also has vent holes to let the excess pressure out, instead of popping the engine case out, or the nose cone off.

Also, note that this rocket was made in the very early days of model rocketry. It uses BT30 tubes, which aren't widely available any more (I got mine from Balsa Machining, IIRC, along with the BT-30-sized nose cone). It is a very reinforced rocket, with extra thick fins at 3/16" thick, and gauze reinforcement to keeps them fins attached. The plans are available on JimZ's site.

I started by cutting the tube to length, and cutting six fins from 3/32" stock. I doubled up the fins, so that they became 3/16" thick. The wires in the photo are the piano wires that I used to make the retaining wires.

[DavidQ]

One question was about the vent holes. Some plans have one vent hole, some pictures show one hole, and other plans and pictures show 3 holes. My inspection of the catalog photos indicates that the early design had three vent holes, and later models had one vent hole. So, I went with three.

I suspect that may have ended up weakening the body a bit, so the later designs only had one hole. But, in the early days, doing was the same as experimenting.

I punched the holes with a simple hole punch.

I also fabricated the metal clips using a printout from JimZ's site, and matching my Vise grips to the pattern.

[DavidQ]

To hold the fins, I cut a fin alignment guide for extra thick fins and a BT30 tube.

I think the photos had the fins directly below the vent holes, so that's how I put them together.

I tacked the fins in place with Aleene's Tacky Glue while they were held by the guide.

Oh yeah, I sanded the edges just like recommended in the instructions. Usually, I'm OK with squared fins, but since these are so thick, and that's how it was done back then, I spent the extra time to sand rounded edges on the leading edge of the fins, and beveled edges on the trailing edges.

[BEC]

With modern motors you NEED three vent holes or it will just blow the motor out anyway. The Semroc Golden Scout repro has three and it works consistently as it should. I acquired an old but never-flown Scout in an eBay transaction that had one vent hole and it just blew the motor out and then lawn darted.

But even when they work properly breaking fins just past the gauze is a common result of landing on anything but grass.

Good choice to go with three vents.

Love that laser cut fin guide.

[DavidQ]

I then added the wires to hold the motor in place after the ejection charge went off.

For added strength, this kit uses gauze to hold the fins and clips. I'm sure that I didn't have the right gauge of gauze, but as these are scratch-builds and not purist clones, I'm OK with that.

I first tacked down the gauze with a single layer of white glue - Elmer's Glue-all. The clip wasn't perfectly straight, so I used a small hobby clamp I had to hold everything flush against the body tube.

After the gauze dried, I put on two more coats of glue. It didn't really hide the gauze, or give me a good foundation to make a smooth finish, however.

[DavidQ]

So, after the gauze and glue dried yet again, I decided to make it smooth. But, as with almost everything, to go forward one must go back. So, I put on a layer of filler, so as to sand it smooth later.

I think it smoothed up pretty well. And, as is obvious, made quite a bit of dust.

[dlazarus6660]

Nice!
I did one of these 8 years ago and only used one hole. It was not enough! I did use CA around the top after I glued on the nose.
I have whats left of an original kit(wire, gauze and instructions)
I need to find my clone now.

[DavidQ]

Now, after three coats of auto build-up primer, and three coats of paint, it's all pretty white.

After I printed up some decals, its even got a name!

And, then I got in the mood for more cowbells. I mean more building rockets. I rationalized that most people don't have BT-30 tubes, but they quite likely have BT-20 tubes. I'm even sure that if we were to scour this site, we'd find recommendations to build a Scout out of BT-20 tubes, and a corresponding BT-20 nose cone.

So I did. I used the same fin pattern, but with basswood this time, for strength. I used the same length body tube, but of BT-20. For the nosecone, I used a 20L nosecone. It's 1.375" long instead of 1.5", and its rounded instead of sharp, but it's a scratch build and I had those.

Oh yeah, I also downscaled it to a BT-5 size. I want to see how an itty-bitty rocket that could handle featherweight recovery does with this kind of tumble recovery.

Now to get some time to launch these.

[mojo1986]

Very, very nice!

Joe

[Blastfromthepast]

Nice builds!

So are you moving on to the Mark (K-2), now?

I am seriously considering starting a similar program of doing scratch builds of all the Estes K-series rockets, but in my new-found BAR-dom, I'm sort of like a kid in a candy store when it comes down to deciding what rocket projects I want to tackle. Besides the K-series, I am also looking at several scale builds from the pages of Model Rocketry magazine, a few clone re-builds of some of my favorite birds I flew in the old days, and a couple of custom designs. There are even a handful of modern Estes kits that strike my fancy....

Anyway, good job on the Streaks. Keep posting your upcoming projects!

[DavidQ]

It didn't work right. Ballistic entry is not a good thing with model rockets.

I wasn't sure how to prepare it, and wasn't comfortable leaving the engine/motor/propulsion unit/fire-making-thingy hanging down at the bottom of the clip. It seemed to me that if it took off upward and smacked into the nose cone, it wouldn't be a smooth launch and might even knock off the knose kcone.

So, I put a small amount of tape around the engine to hold it snugly upward in the engine tube.

But, that snugness kept the ejection charge from pushing the engine casing backwards so that the rocket would become unstable. Instead, it remained stable and came in hard.

What do you guys do - including you guys as the ones that launch the Scout, and even you guys that just have some kind of response to an open ended question such as that?

BTW, it still has its spot on the shelf. It earned it.

[Scott6060842]

It didn't work right. Ballistic entry is not a good thing with model rockets.

I wasn't sure how to prepare it, and wasn't comfortable leaving the engine/motor/propulsion unit/fire-making-thingy hanging down at the bottom of the clip. It seemed to me that if it took off upward and smacked into the nose cone, it wouldn't be a smooth launch and might even knock off the knose kcone.

So, I put a small amount of tape around the engine to hold it snugly upward in the engine tube.

But, that snugness kept the ejection charge from pushing the engine casing backwards so that the rocket would become unstable. Instead, it remained stable and came in hard.

What do you guys do - including you guys as the ones that launch the Scout, and even you guys that just have some kind of response to an open ended question such as that?

BTW, it still has its spot on the shelf. It earned it.

The engine should be left loose. A very thin piece of copper wire is supposed to be glued to the side of the tube. This is bent over preflight to hold the engine in the up position but is thin enough for the engine to release at ejection (the wire is thin enough that the ejection "straightens it" and will allow the engine to fall to the bottom of the engine hook).

[Doug Sams]

It didn't work right. Ballistic entry is not a good thing with model rockets.

I wasn't sure how to prepare it, and wasn't comfortable leaving the engine/motor/propulsion unit/fire-making-thingy hanging down at the bottom of the clip. It seemed to me that if it took off upward and smacked into the nose cone, it wouldn't be a smooth launch and might even knock off the knose kcone.

So, I put a small amount of tape around the engine to hold it snugly upward in the engine tube.

But, that snugness kept the ejection charge from pushing the engine casing backwards so that the rocket would become unstable. Instead, it remained stable and came in hard.

What do you guys do - including you guys as the ones that launch the Scout, and even you guys that just have some kind of response to an open ended question such as that?

BTW, it still has its spot on the shelf. It earned it.Some thoughts on this rocket:

I agree with Scott, the motor needs to be loose. But not too loose. Two things concern me if it's too loose. One is that the ejection charge will impart too much momentum to the motor thereby causing a hard impact with the end of the motor hook which might cause the hook to deflect and release the motor, or the motor to rip the hook loose from the rocket.

So I like to put just enough tape on the motor to give it a little sliding friction. This will also help keep the motor from bouncing off the hook back up into the airframe (thus making it ballistic).

Speaking of ejection charges, another problem can be the very stout charges found in some of the 13mm motors. To address that, I made the hole a bit larger on the airframe, hoping that would relieve some of the pressure and thus result in less aft momentum being imparted to the sliding motor.

Another thing I did to combat some of the issues with this rocket was to add a wire loop to the motor which wraps around the motor hook. The intent was to prevent the hook from deflecting sideways (when the motor hit the end of it). This ensured the motor stayed with the rocket and thus (theoretically) made the rocket tumble :) (See attached.)

Lastly, when flying the Scout, only fly it over soft ground. Ground that's been unwatered for two+ weeks in the Texas heat (for example), 100°F here lately, will be hard and, even with a perfect tumble, can break a fin.

Doug

.

[mojo1986]

Another method of holding the motor forward before launch is to put a clothespin low on the launch rod. The motor is supported by this and the rocket stays all the way down on the motor by gravity. I agree with using a bit of masking tape on the motor too.

Joe

[Coconuteater64]

I built a bunch of these as a kid and never used the thin copper wire that came with it. I always just let the motor "fly" up the body tube and though it did slam into the nose cone, it was never a problem. The reasons I lost them was because I insisted on only buying C motors as a kid (thinking "Why pay the same money for half the propellant?") and they'd disappear into the woods, or the motor would eject out the back and it would come down ballistic. Never had a motor fly through the nose cone just letting the motor launch itself into the body tube.

[DavidQ]

I think I might go without any tape, along the lines of Coconuteater64's suggestion. I have one in BT-5 size and one in BT-30 size, so I'll just see how it works with the engine slamming into the nose. If anything else, I could try the clothes pin trick.