The Maple Seed - Part 1: Motor mount & body tube
The Thrifty Rocketeer blog continues...
After several months of coming down on the wrong side of the fence, I spotted a sale on the novelty rocket "The Maple Seed" made by Semroc and distributed by eRockets.biz
I recognized that someone had put a lot of design time into this rocket which sheds its fins, only to have them spin and tumble down to earth. That's the appeal. Plus, the rocket main body recovery under a parachute.
Now, you may think that this would not be a difficult challenge to design and produce. However, the more you think about it, the more you will realize you have at least four separate "parts" to produce for recovery. Plus, if it was all that easy, why hasn't someone done this before?
This last month, I spotted the sale price, and being a bit bored at home, I figured I could have a friend pick one up for me and when I saw him, I'd pay him the $30 for the kit. As it turned out, I got it both sooner and later than I had expected.
So on a Sunday evening as the social distancing began, I sliced open the bag and started examining the parts. As he mentioned, the kit has a fair number of parts, as the fins are sandwiched together to add a fair amount of weight. Not that this is particularly difficult, but the rocket IS rated as Level 3.
I will divide the rocket assembly into two major components. First, the motor mount and body tube is one construction that is fairly straight forward. The second, more unique build, is the maple seed fin, which is done in triplicate. This also means if you are not careful, you will make the same error times 3 as well. And yes, if you haven't already guessed, I blew it, times 3...(but I recovered).
Now, as I begin to write this, it's been at least two weeks since I assembled the rocket, and we've had a bit of an interruption get in the way... you may have heard of the cornoavirus and self quarantine. Well, this was a good little distraction for a sequestered Thrifty Rocketeer on a beautiful weekend. If you can't fly, build.
I have photos of my assembly and the parts laid out, stacked upon one another. Since three fins are being build or sandwiched, you have 3 of everything and at least one set of six (both sides of the fin, as you will see.)
After doing a number of other builds, the motor mount has become old hat for me. However this one has two unique or new elements. The first is the use of a Kevlar string tied around the motor clip, and threaded up the inside of the body tube when installed. The second is the spacing of the centering rings.
You'll note that other than bowing the metal retaining hook-spring, there's nothing more holding the spring in place, other than the yellow wood glue. On the inside, a thrust ring is glued up against the protruding tab of the motor hook. The front centering ring is pressed up against the motor spring that is plunged through a pre-cut slot. The yellow Kevlar string is knotted in a loop, lassoed over the metal spring, but then fed through a notch on the inside of the centering ring. That's no big deal.
But the unusual factor is the spacing of the SECOND (top as seen below) centering ring, which instructions say is one full inch from the end of the motor mount tube. However the drawing would indicate that it is a greater distance than one inch. I installed and glued it at one inch as was stated several times.
The nosecone is another puzzler, but not for the reason you might think. I like a balsa nosecone, as my first few rockets all featured them. Eventually, I got smart and started sealing them first before painting...to reduce the incidents of "Estes Smile". This would be a good idea for this kit also, I suspect. And so, I did seal it down to the shoulder with a slurry of wood glue and water. The screw-eye goes into the center of the base of the nose cone, and then backed out again. And here's where it gets a little weird.
The instructions list two metal washers (for weight) to be trapped and glued under that screw-eye. So a dab of glue goes into the screw hole that you've just twisted in and out... and some glue was smeared on the base face of the nosecone, and the washer pressed into it, as the screw-eye is turned in and holds it in place.
You'll note that I said only one is held in place. That's cause only one was included in my kit. It was a thick one, much heavier than most. So, I was left wondering if a thicker, single washer is included instead of two thinner, more traditional washers. (I've since heard from others who built the kit, and they also received only one.)
An inquiry to eRockets during the quarantine got me a brief answer that "no changes or substitutions were made ".... only one was included. They asked if I had another laying around that I could use. Probably. Certainly, it's NOT worth shipping a single washer across the country. But I found it odd. So I installed and glued down the only washer I had at the time.
Now, I'm gonna jump forward here for the sake of compartmentalizing the build. You're supposed to draw some fin lines and a launch lug line on the base of the body tube, which is easy enough. Extend the lines up the side with an angle iron. ( I prefer the Great Plains Sander bar for this.)
The launch lug installation comes much later when balancing the rocket with an engine loaded inside as well. But the hook foot is eventually glued along each of the three fin lines.
As you can see, the hooks come together, and must be split apart. I found this basswood was not completely stamped or burned through, and more than a little nudge from an Exacto knife was required to separate two of the three. Once freed, the bottom half of the hook that contained two tabs fits perfectly in the shoe...and a little wood glue cements them into one unit.
The next picture down shows them as they are drying in line on the body tube (resting on my favorite egg carton holder.) [Note the fins and three sets of both top and bottom turbulators in the background. The top turbulators are stacked closer to you than the bottom turbulators which are nestled right behind. Note the difference in their "head" to the right. One is more square, the other more of a "Y". This will be an important distinction next week.]
Other than assembling the 12" plastic parachute and attaching it and the shock cord to the screw eye, everything is done EXCEPT for the three fins. And I have intentionally skipped over them until next installment. I'll explain why next time. Oh, and painting the body tube & nosecone, as you wish.
Until then, keep your glue capped and save your spare scrap balsa, cause I needed it to recover from next episode's goof!
After several months of coming down on the wrong side of the fence, I spotted a sale on the novelty rocket "The Maple Seed" made by Semroc and distributed by eRockets.biz
I recognized that someone had put a lot of design time into this rocket which sheds its fins, only to have them spin and tumble down to earth. That's the appeal. Plus, the rocket main body recovery under a parachute.
Now, you may think that this would not be a difficult challenge to design and produce. However, the more you think about it, the more you will realize you have at least four separate "parts" to produce for recovery. Plus, if it was all that easy, why hasn't someone done this before?
This last month, I spotted the sale price, and being a bit bored at home, I figured I could have a friend pick one up for me and when I saw him, I'd pay him the $30 for the kit. As it turned out, I got it both sooner and later than I had expected.
So on a Sunday evening as the social distancing began, I sliced open the bag and started examining the parts. As he mentioned, the kit has a fair number of parts, as the fins are sandwiched together to add a fair amount of weight. Not that this is particularly difficult, but the rocket IS rated as Level 3.
I will divide the rocket assembly into two major components. First, the motor mount and body tube is one construction that is fairly straight forward. The second, more unique build, is the maple seed fin, which is done in triplicate. This also means if you are not careful, you will make the same error times 3 as well. And yes, if you haven't already guessed, I blew it, times 3...(but I recovered).
Now, as I begin to write this, it's been at least two weeks since I assembled the rocket, and we've had a bit of an interruption get in the way... you may have heard of the cornoavirus and self quarantine. Well, this was a good little distraction for a sequestered Thrifty Rocketeer on a beautiful weekend. If you can't fly, build.
I have photos of my assembly and the parts laid out, stacked upon one another. Since three fins are being build or sandwiched, you have 3 of everything and at least one set of six (both sides of the fin, as you will see.)
After doing a number of other builds, the motor mount has become old hat for me. However this one has two unique or new elements. The first is the use of a Kevlar string tied around the motor clip, and threaded up the inside of the body tube when installed. The second is the spacing of the centering rings.
You'll note that other than bowing the metal retaining hook-spring, there's nothing more holding the spring in place, other than the yellow wood glue. On the inside, a thrust ring is glued up against the protruding tab of the motor hook. The front centering ring is pressed up against the motor spring that is plunged through a pre-cut slot. The yellow Kevlar string is knotted in a loop, lassoed over the metal spring, but then fed through a notch on the inside of the centering ring. That's no big deal.
But the unusual factor is the spacing of the SECOND (top as seen below) centering ring, which instructions say is one full inch from the end of the motor mount tube. However the drawing would indicate that it is a greater distance than one inch. I installed and glued it at one inch as was stated several times.
The nosecone is another puzzler, but not for the reason you might think. I like a balsa nosecone, as my first few rockets all featured them. Eventually, I got smart and started sealing them first before painting...to reduce the incidents of "Estes Smile". This would be a good idea for this kit also, I suspect. And so, I did seal it down to the shoulder with a slurry of wood glue and water. The screw-eye goes into the center of the base of the nose cone, and then backed out again. And here's where it gets a little weird.
The instructions list two metal washers (for weight) to be trapped and glued under that screw-eye. So a dab of glue goes into the screw hole that you've just twisted in and out... and some glue was smeared on the base face of the nosecone, and the washer pressed into it, as the screw-eye is turned in and holds it in place.
You'll note that I said only one is held in place. That's cause only one was included in my kit. It was a thick one, much heavier than most. So, I was left wondering if a thicker, single washer is included instead of two thinner, more traditional washers. (I've since heard from others who built the kit, and they also received only one.)
An inquiry to eRockets during the quarantine got me a brief answer that "no changes or substitutions were made ".... only one was included. They asked if I had another laying around that I could use. Probably. Certainly, it's NOT worth shipping a single washer across the country. But I found it odd. So I installed and glued down the only washer I had at the time.
Now, I'm gonna jump forward here for the sake of compartmentalizing the build. You're supposed to draw some fin lines and a launch lug line on the base of the body tube, which is easy enough. Extend the lines up the side with an angle iron. ( I prefer the Great Plains Sander bar for this.)
The launch lug installation comes much later when balancing the rocket with an engine loaded inside as well. But the hook foot is eventually glued along each of the three fin lines.
Other than assembling the 12" plastic parachute and attaching it and the shock cord to the screw eye, everything is done EXCEPT for the three fins. And I have intentionally skipped over them until next installment. I'll explain why next time. Oh, and painting the body tube & nosecone, as you wish.
Until then, keep your glue capped and save your spare scrap balsa, cause I needed it to recover from next episode's goof!
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