Moving on to 1963 - Scratch build Streak K-4

[DavidQ]

Having finished the three kits in the 1961 catalog, I continued to the K-4 kit. Streak was included in the 1963 catalog. It had a mylar plastic tube, for a very light rocket which could reach such heights that it surely got lost as much as the Mosquitos do.

It came with suggestions for two designs - a sport version and a competition version. The sport version was easier to build, requiring less work on the fins. The competition version required more shaping of the fins to reduce the drag.

I decided to build both versions. I considered making a BT-5 version of the rocket. But, then I did the math - a BT-5 rocket with a short blunt nose cone, three skinny fins with rounded tips, and the body tube just long enough to hold the engine and nose. I think we already have a name for that rocket - a Mosquito. I've made plenty of those, so instead of a BT-5 version, I made a BT-20 version. I figure that's what people would make if they didn't have the plastic tubes.

Speaking of which, I looked for appropriately sized plastic tube for a scratch build. Yeah, some vendors carry it, but I decided to build it, and needed the tube now! At Walgreens (a drug store), I found a tube with three lip glosses, or lip balm, or something like that. My calipers said that the tube was within a few thousandths of what I was looking for! So, my nieces got a bunch of that lip stuff, and I got a few clear tubes.

I cut 1/16" balsa fins for the sport version, 1/16" basswood for the BT-20 version, and 1/32" balsa fins for the competition version. I had a rough approximation of a BNC-20A nose that I previously made with my 3D printer, so used it for the BT-20. The BNC-10A nose cones were from Balsa Machining. I also rolled my own launch lugs.

[DavidQ]

For the sport version of the Streak, the lower half of the plastic body tube is wrapped with adhesive backed paper. I carefully aligned the paper first, before removing the backing. Mainly, I didn't expect to be able to reposition the paper, so it was a "get it right the first time" effort. The paper is needed because it's pretty hard to glue balsa, or basswood, to mylar without some special kind of glue.

I tacked the fins in place with the old standby, Aleen's Tacky Glue. Later, I applied three thin layers of white glue as fillets.

[DavidQ]

I glued the fins directly to the tube for the BT-20 build.

For the competition build, I trimmed the adhesive paper into narrow strips, one for each fin. This removed about half the paper.

I also hollowed out the balsa nose cone as suggested by the instructions.

[Doug Sams]

I glued the fins directly to the tube for the BT-20 build.

For the competition build, I trimmed the adhesive paper into narrow strips, one for each fin. This removed about half the paper.

I also hollowed out the balsa nose cone as suggested by the instructions.I'm enjoying your builds - more importantly, I'm having fun watching you have fun :)

Anyway, I want to remind you, the Streak used a mylar tube, which can take the heat of ejection charges. But the plastic will likely warp under those conditions.

I used a plastic tube as a payload section on a scratch design, and didn't block it off at the bottom - just had a hollow, open coupler there - and it took a decided curve after the first flight :( That is, at the time, I didn't appreciate the difference between mylar and plastic.

So maybe you will save these in your collection unflown.

FWIW, on my Streak clone, I just used BT-20 and painted the entire tube thereby hiding the fact it wasn't mylar.

Doug

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[DavidQ]

Good point, Doug.

I was looking in the old 1963 catalog, and saw that Estes had 18mm 1/4A's back then. I think I'll build an 18mm to 13mm adapter for the Streaks. I'll block it off, so the ejection charge only ejects the engine, and won't travel up into the rocket.

This way, I could launch the Streak's with 1/4A and 1/2A, but the ejection charge could be contained within the adapter, and hopefully, not come into contact with the mylar.

I'm not sure, but it might even be lighter to use a 13mm 1/2A with an adapter than to use an 18mm 1/2A. I'll check it out.

[DavidQ]

To reduce the weight I'd normally add when finishing a rocket (3 layers of primer sanded down, followed by up to 3 layers of paint), I went back to using aircraft dope.

My light weight rocket came in at about 0.75 oz, which was a bit over the 1/2 oz mentioned in the catalog. I'm guessing it's due to the plastic I used.

The BT-20 just got all painted up, and I didn't care about the weight.

I left both of the plastic rockets with the plastic exposed. I liked the look, and I didn't need to apply any finish to that part of the rocket.

I made the decals using the old Estes decal sheet D-6, which had some hand-drawn decals for the early rockets. I decided to gussy them up by adding color, and scaling them to fit various parts of the rockets.

Edit: those weight numbers are wrong. See my later post below.

[Blastfromthepast]

This is a really cool thread...enjoying the heck out of it!

At the rate you're going, you should be wrapping up that SPEV by the end of 2016!

[DavidQ]

D'oh! I just double-checked my numbers about the weight of the Streak, and my remembered numbers were not remembered correctly. The catalog says it should be about 1/8 ounce. Mine came out at 0.17 ounces. A bit over, as I remembered, but only by a tad.

I also built a 13mm mount for the streak, so it could be launched with 1/4A engines, and the smaller 1/2A and possibly the A engines. To compare, an 18mm A8-3 weighs 0.58 oz. A 13mm A10-3T plus the 13mm mount weighs 0.35 oz - a reduction of .23 oz. That's more than the rocket weighs! I can shave enough weight off of an A engine that the rocket is carried for better than free!

If I woose out (I'm not sure of the spelling - consider it the same as If I am a scaredy cat) and fear losing the rocket with an A engine, I could use a 1/2A. An 18mm 1/2A6-2 weighs 0.51 oz, but the 13mm 1/2A3-2T with adapter only weighs 0.29 oz - another 0.22 savings. That'll likely add as much height as stepping up to an A engine. Heck, the 1/4A3-3T plus adapter is only 0.25 oz, as compared to the 18mm 1/4A8-2 which weighed 0.50 oz, as per the 1964 catalog. That would put the launch weight from 0.67 oz all the way down to 0.42 oz, roughly 2/3 the weight just by using an adapter. And, it keeps the plastic from being exposed to the ejection charge. That was a good idea, Mr. Doug Sams!

[eljefe]

What cute little rockets. But tiny AND transparent? Seem like they'd be impossible to ever find!

If I woose out (I'm not sure of the spelling - consider it the same as If I am a scaredy cat)

I think the word you're looking for is "wuss." Though I admit "woose" make a more rockety kind of sound!

[DavidQ]

What cute little rockets. But tiny AND transparent? Seem like they'd be impossible to ever find!
I think I have a new trick that I'm going to test out. See, I teach a rocket class to 4th and 5th graders for nine weeks each year. This year, on a rainy day, we built mosquito-like rockets. So, we had over a dozen of those little rockets to lose. I told them they likely would lose them, and they could opt out of launching them if they wanted. A dozen still went ahead and launched.

But, before launching them, we launched other bigger rockets, and I had tilted the launch pad to land on the far side of the field. I left it that way when we launched the mosquito-like rockets. Well, this time, they followed a nice arc up, continued the arc when coasting, and when the ejection charge expelled the engine, they continued in the same general direction. The kids that were at the far end of the field could see right where the mosquito landed, since it was coming "toward" them. We recovered 10 of the 12 rockets - way more than I expected.

I think that launching mosquitos straight up allows them to tip in nearly whatever direction they feel like at apogee. Then, the ejection charge sends them rapidly scurrying through the air to escape all of our sight. But, by tricking them into taking a more ballistic flight, I could trick those rockets to go where I wanted them to be.

I'll try the same parabolic flight path technique with the small rockets I just built, like these Streaks and the Marks.

[dlazarus6660]

I think I have a new trick that I'm going to test out. See, I teach a rocket class to 4th and 5th graders for nine weeks each year. This year, on a rainy day, we built mosquito-like rockets. So, we had over a dozen of those little rockets to lose. I told them they likely would lose them, and they could opt out of launching them if they wanted. A dozen still went ahead and launched.

But, before launching them, we launched other bigger rockets, and I had tilted the launch pad to land on the far side of the field. I left it that way when we launched the mosquito-like rockets. Well, this time, they followed a nice arc up, continued the arc when coasting, and when the ejection charge expelled the engine, they continued in the same general direction. The kids that were at the far end of the field could see right where the mosquito landed, since it was coming "toward" them. We recovered 10 of the 12 rockets - way more than I expected.

I think that launching mosquitos straight up allows them to tip in nearly whatever direction they feel like at apogee. Then, the ejection charge sends them rapidly scurrying through the air to escape all of our sight. But, by tricking them into taking a more ballistic flight, I could trick those rockets to go where I wanted them to be.

I'll try the same parabolic flight path technique with the small rockets I just built, like these Streaks and the Marks.



Brilliant!