Build - Quest Big Dog

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lcorinth

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I've been working on the Quest Big Dog for some time now. It's taken me a while, mostly because I wanted to make some decisions - what adhesives I wanted to use, what to do with the fins, whether to use buttons or launch lug, what size buttons, etc.

But it's coming along, and I've never posted a build thread here on TRF (I think), and I have plenty of pictures, so I thought I'd start one.

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Rocket: Big Dog
Manufacturer: Quest Aerospace
Length: 32.5 inches
Diameter: 1.97 inches (not 1.92 inches, as is stated on the kit. This will come back later)
Motor diameter: 29mm with 24mm diameter adapter.
Decals: Self-stick

Part I: Parts

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Yep, all there. I won't be using the thrust ring, and in the picture is included an Estes 29mm screw on retainer.

Part II: Motor Mount

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The shock cord is in two parts: Kevlar thread, tied to an elastic band. The Kevlar end is tied into a slip knot around the motor tube and passes through the forward centering ring. I got the centering rings as straight as I could, and embedded the shock cord mount into a fillet of glue. Once the aft fillets were dry, I did forward fillets.

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You can see I marked a line where the motor retainer would end, just to make sure I had room. Kit instructions had the aft ring about an inch in, so there was no problem there. I scuffed up the inside of the motor retainer, as well as the end of the motor tube, and attached the retainer to the end of the tube with JB Weld.

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I don't know what kind of knot I used to tie the Kevlar to the elastic. It seemed pretty strong, but if it ever came undone, I'd have no way of re-attaching it. I massaged a bit of JB Weld into the knot with gloved fingers.

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The motor mount is done. I forgot to mention in the OP that I was leaving out the thrust ring.

Next, I cut out the fin alignment guide and wrapped it around the rocket. I held it in place with a bit of blue tape.

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I noticed a slight gap between the first fin line and the edge of the paper, but didn't think much of it, so i marked the fin lines with little dots.

The Quest fin guides don't come with a launch lug line. To make sure I had it precisely between two of the fin lines, I folded the guide over and lined up two of the fin lines, and marked the crease.

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I laid the guide back on the rocket. I happened to place the guide on the marks for the first and last fin, and that's when I noticed a problem - they didn't match up! When I checked the lines against the other marks, they were perfect. I got suspicious, and got out my digital caliper.

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It gave me a diameter of 1.97 inches. The kit says the diameter is 1.92 inches. I knew this thing would come in handy! That discrepancy threw off my fin alignment by just a little bit.

I opened up the free RockSim file from Apogee Components, and it, too, said the diameter was 1.97 inches. So, I printed that off, and it was indeed slightly longer than the kit guide. I cut out the RockSim guide, taped it onto the rocket, and remarked the fin lines, with the added benefit of a launch lug line already marked on the guide.

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Marked the lines down the tube...

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After that, I filled in the tube spirals, with the technique I wrote about here.
 

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Lookin good! Looks like a nice kit.
Checking twice on the fins is always a good Idea on any kit.
I've found that the Fin Guides included with every kit are always off enough to make me not use them. They get thrown away ASAP.
I'm completely OCD about fin alignment.
 
I decided to go with 30 minute epoxy to mount the motor mount into the rocket. I didn't want wood glue to seize up, and I wanted to be able to reposition the mount if I didn't like where it landed. Plus, I thought the epoxy might be stronger.

To avoid getting the shock cord stuck in the epoxy inside the rocket, I pulled the whole thing through and out the back of the motor tube.

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I used Bob Smith Industries. It's what I had available without having to shop online. I wrapped blue tape around the motor retainer to keep epoxy off the threads.

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I spread a ring of epoxy around the inside of the airframe and inserted the motor mount. I was surprised at how loose the centering rings were (the 1.92/1.97 inch discrepancy again?). It was so loose, I couldn't tell by feel if I'd even hit the epoxy ring.

So, I gently taped the end of the rocket to support the motor mount where I wanted it, and taped the rocket in an upright position on a launch rod.

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I took a flash light and saw that there was definitely a fillet inside. I'm so glad I didn't use wood glue for this! I let the epoxy cure overnight, and the next day, everything felt nice and secure.

I attached a clothes pin to the shock cord and dropped it back through the motor tube.

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Then I taped the rocket to the launch rod again, aft side up. I made a fillet of 30 minute epoxy which I injected into the gap between the wall of the airframe and the motor retainer with a medicine dosage syringe.

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I used a coffee stir stick to make sure I had epoxy in contact with the wall of the airframe and the centering ring all the way around. I got a decent fillet. I cleaned up any stray epoxy, removed the tape from the motor retainer, and let the epoxy cure overnight.

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Lookin good! Looks like a nice kit.
Checking twice on the fins is always a good Idea on any kit.
I've found that the Fin Guides included with every kit are always off enough to make me not use them. They get thrown away ASAP.
I'm completely OCD about fin alignment.

Oh, I agree! On rockets with standard Estes BT-sized tubes, I prefer to use my Estes Tube Marking Guide fin alignment guides. Those are the only part of that piece of equipment I find useful, but I really like them. And they can act as a stand to keep a tube upright.

I just wish they came in more sizes.
 
Quick update before a much-needed nap.

So, I cut six extra fins from some 1/8 inch balsa. I did this for two reasons: I was about to try a new technique for sanding airfoils by hand (by "by hand," I mean just my two hands and a sanding block; my earlier attempts, some of which worked well, involved me rigging up a system using a metal ruler as a slide, and trying to get a consistent angle with... well, it's complicated. Sometimes worked, sometimes didn't.), and I wanted to see if I could successfully paper the fins.

I also figured if I messed up one of the kit fins, I'd have a backup. And if I didn't, I'd use the extra fins on a scratch build, an E-motor quad cluster I'm calling the Quad Dog - until I can come up with a better name for it.

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Before you post any replies with links to the various excellent papering tutorials here on TRF, I have seen them, and I've been practicing them, but I have been a little too clumsy with the glue. I'm still working on it. Thus, the six extra fins.

The airfoiling went great:

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The papering, trying different adhesives (white glue, wood glue, spray adhesive) and different approaches (two skins, one skin wrapped around the leading edge), was less consistent.

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Out of the six, I got three papered fins which, while not all perfect, are good enough for the Quad Dog.

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I find that I have less trouble with smaller fins; these are pretty big, and I dropped one or two, getting globs of glue where I didn't want them.

I'll keep working on it!

For now, though, I decided to stick with CWF for the Big Dog. It's a mess, takes more time, takes a bunch of sanding, and creates a lot more dust, but I know I can do it and get the results I want.

More later. Nap time...
 

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Airfoiled the kit fins. These were tough! The kit says they're balsa, but the wood grain is tighter and they're much harder than any balsa I've worked with. While the practice fins took maybe 10 minutes a piece to airfoil, these took much longer.

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Painted the fins with a mixture of CWF:Water 2.5:1. Laid them on a cooling rack to dry, flipping them occasionally to assure good airflow. When I nonetheless saw a bit of warp developing on the trailing edges, I pressed them between sheets of parchment paper. I prefer parchment to wax paper if I have to press fins, because it wicks a little of the moisture away and takes a little less time to dry.

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The fins on the left are for an Estes Cosmic Explorer with E motor mount I'm building. Those fins did not need pressing.

Sanding out all the pits and imperfections in the CWF, I ended up going all the way down to wood grain in a few spots. A second coat of CWF, thinned a little more, and sanding gave me nice, smooth fins.

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Looking good.
I dig this BIG DOG rocket.
Don't have one YET!
EDIT . I like your drying rake. I have an "Uprite" one. Like one would use for sorting/storing mail.
 
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Looking good.
I dig this BIG DOG rocket.
Don't have one YET!

Haven't posted pics yet, but I have the fins on and fillets, and it looks really cool. Very wide fin span. I really like the rocket.

I did skip ahead and build an Estes Partizon, just to see what construction would be like on a larger rocket, but with that exception, this is my largest rocket to date. At any rate, I'm sure I'll launch this one before I get to that one.

[Edit] Oh, and I love these Quest nose cones!
 
I've opted to go with micro buttons from rail-buttons.com for this rocket. I placed the forward button hole about 10 inches from the aft, where the kit instructions said the launch lug should go. I drilled the aft hole about 2 1/4 inch from the aft. The centering rings are fiber rings, not something you'd drill into, and they're kind of far in, so I put the aft button hole where I knew the screw wouldn't interfere with anything. After drilling, I wicked thin CA into the holes and wiped off the excess.

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Next it was time to add fins. With the Guillotine Fin Jig, you place a fin (or stock of the same thickness) in a notch at the front and the back in order to line things up. I always stick a third fin in the middle to make sure I've got everything straight and I'm not squeezing anywhere, messing up my alignment.

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I decided to use wood glue to attach the fins. It would be nice if this kit had TTW fin construction, which would be more secure. But I'm going to use epoxy for the fillets, so to get the fins on, I feel comfortable with wood glue.

Making a double glue joint:

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And onto the rocket...

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After getting a few fins misaligned to one another on previous builds, I now do opposite fins, so I can check alignment.

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By the way, I'm aware that the top photo looks like the alignment is slightly off. This is an optical illusion, due to the shadows and the fact that my camera distorts close-up images. Those fins are straight.

Here are all four fins on (again, looks distorted, like I've got floppy fins):

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Next up: Fin fillets
 
I like to use the Guillotine to hold the my rockets while I work on them. I take the arms off so I don't catch them on something - a fin, a sleeve, whatever.

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Since the Big Dog doesn't have TTW fins, and I'd like a little more strength, I'm going to use epoxy for the fillets. I also want the fillets to be visible - I've realized that every time I use wood glue, the fillets shrink to a point where they almost aren't there at all. I'll use the dowel in the above photo to shape them to the desired radius. I think the dowel is 3/8 inch, but I'd have to check.

I'm also going to try out microballoon filler for the first time. First, because I want the fillets to hold their shape rather than flattening out, and second, because I want to be able to sand them if they don't come out just right.

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I'm guessing at this point in the build that microballoons will make the epoxy fillets a little weaker, but that they'll be stronger than mere wood glue fillets. I'm going to try it and see. In any case, I'm guessing that they won't be weaker than the wood glue fillets recommended by the kit instructions, and if they are, I guess that's part of the learning experience.

I start by marking the edges of the fillets, so I know where to tape. I just don't trust that I won't get epoxy where I don't want it - and I'm pretty new at using epoxy. But experience with wood glue tells me that I know I tend to get extra up on the fins.

I mark the end of the dowel with a soft-lead pencil.

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And use it to mark lines on the fins and airframe.

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Then I tape everything off.

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I know I'm less likely to make a huge mess and have a disaster if I follow a principle of good cooking - mise en place.

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I have everything I need in reach in case of a major drip or something - a cup of alcohol, plus the bottle itself, paper towels, an extra stir stick, etc. I'm nervous before doing this the first time...

The first set of fillets goes well, and with repeated passes of the dowel dipped in alcohol, I get a really smooth, nice shape.

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This turns out to be a really good thing, because I realize later I didn't use enough microballoons. They prevented sagging, but there wasn't really enough to make the filets easily sandable.

Nonetheless, these are so far the nicest fillets I've ever done, and I up the amount of microballoons with the next set of fillets until I find the consistency I want.
 
Very nice! I was wondering what the current zeitgeist is re: should the motor mount thread plastic unit hang down below the body tube, or should it be flush with the body tube?

It looks like your’s is hanging down, like a Big Dawg! I am so far behind in my Big Dog build…I’ll take a picture of my fin alignment OCD cure/enabler when I get to that point...
 
Very nice! I was wondering what the current zeitgeist is re: should the motor mount thread plastic unit hang down below the body tube, or should it be flush with the body tube?

It looks like your’s is hanging down, like a Big Dawg! I am so far behind in my Big Dog build…I’ll take a picture of my fin alignment OCD cure/enabler when I get to that point...

Thanks!

The instructions have the motor tube (sans retainer, which doesn't come with this kit) overhanging by 1/4 inch, so that's what I tried for (plus a little extra, because of the retainer). But the airframe is narrow enough I'd be worried about not being able to screw the retainer all the way on - or not being able to unscrew it, once it is on - simply because I couldn't get to it once it's in there, if I'd had it flush with the aft end.

With the retainer, the overhang looks like kind of a lot, but I think it'll be fine. I'll need to check the CG before launch anyway, and might need to add nose weight.
 
Thanks!
The instructions have the motor tube (sans retainer, which doesn't come with this kit) overhanging by 1/4 inch,

Ohhhhh yeahhhhh…instructions…them things…I have those. Somewhere. (Rummages around a bit). Yep, there it is, bottom of page 2, “PUSH INTO THE BODY TUBE WITH ONE FAST & SMOOTH MOTION until it sticks out 1/4” from the rear of the body tube…”

Gee, I guess I should follow those things!
 
Ohhhhh yeahhhhh…instructions…them things…I have those. Somewhere. (Rummages around a bit). Yep, there it is, bottom of page 2, “PUSH INTO THE BODY TUBE WITH ONE FAST & SMOOTH MOTION until it sticks out 1/4” from the rear of the body tube…”

Gee, I guess I should follow those things!

Then again, I find it easier to build rockets where the motor tube is flush with the body, because I can just push the whole thing down on a table and know everything's flush. When there's an overhang, I usually use my thumb as a stop, but it's never perfectly where it's supposed to be. I suppose it doesn't matter, but I prefer to get things where I want them on purpose, rather than having them end up where they end up.
 
I had a scrap of tube to which I'd glued on a couple of scrap fins. These were early attempts at papering fins, and they turned out OK, so I had wanted to see what they'd look like when primed - I wanted to get an idea what a finished product might look like.

I grabbed this scrap and took some of the leftover epoxy from the Big Dog fillets and made a kind of rough fillet on the scrap. I wanted to see how sandable these fillets would be, and I wanted to check for strength.

On the left, you can see that I hadn't used enough microballoons. The fillet is sandable, but it's a lot more work. And I figure more sanding means more chance to scuff up the airframe or fins. I upped the amount on both sets on the right side.

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Not only were the subsequent fillet sets more sandable, but even with the microballoons, these fillets were strong! I bent the fin back and forth, distorting the tube, but the fin stayed put. That was reassuring - the Big Dog fins would not be likely to pop off on landing.

Once I got the fillets done and they were curing, I turned my attention to the nose cone.

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I sanded off the flash with some 220 grit (I think - it might have been 320) sandpaper.

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Then I filled the divot with Tamiya plastic putty.

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Once it was cured, I wet sanded off the excess.

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Sometimes I find I have to repeat this process, as there's a little divot or indentation the putty doesn't cover up, but in this case, I was satisfied after one application.
 
After gently sanding off any ridge from the edges of the epoxy fillets, it was time to prime and paint the Big Dog.

I put a fat line of masking tape around the shoulder of the nose cone and put halfway in the top of the rocket. I do this so I can prime and paint the whole thing together, but don't have to worry about the thing getting painted shut.

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This is the first 29mm rocket I've painted. For all my rockets with A-E sized motor mounts, I have a painting rig consisting of an upright dowel with a used motor casing on it. But I don't have a used 29mm motor casing.

I went to the hardware store with my digital caliper looking for a solution that might come close. I ended up making this painting wand from some plumbing parts.

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Turns out a coupler for a 1/2 inch PVC pipe is just over 27mm. So is the shoulder for an 1/2-3/4 adapter, and the ridge of the adapter is over 29mm. The coupler goes a few inches into the motor mount to provide support for the rocket, and the rocket sits on the ridge (I guess this is meant to act as a sort of hexagonal nut when used for plumbing - I just don't know what it's called, so I'm calling it "the ridge"). A bit of tape over the coupler and shoulder assure a tight fit.

I had meant to bolt this down to a wood base, but the metal base plate is so heavy, I didn't need to. It was plenty stable, so I simply used it as a wand, and laid it on a lazy Susan when I needed to.
 
Daniel, a 1 1/8" wood dowel (Home Depot, Lowe's, etc.) is essentially equal to 29 mm and will fit nicely into a 29 mm mount. With a plywood base they make a nice display stand and without can be used as a painting wand.
 
Daniel, a 1 1/8" wood dowel (Home Depot, Lowe's, etc.) is essentially equal to 29 mm and will fit nicely into a 29 mm mount. With a plywood base they make a nice display stand and without can be used as a painting wand.

I'll have to check those out. I'll need a good stand for the Partizon.
 
I stopped into a Pep Boys auto parts store, and looked at their paints. I had originally intended to use the Rustoleum 2X I usually use, including the "Apple Red" I had used on the Quest Quadrunner.

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But I'd heard good things about Duplicolor, and wanted to try it. I thought maybe I'd get a better texture with it, and maybe they'd have many more subtle variations of color. I needed to match the color of the nose cone to the wraparound decal.

I got some Duplicolor filler primer, and got a white can called "Super White" and a "Cardinal Red." The cap on the red looked like it might be a good match for the decal.

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I liked the primer a lot, though it took more coats to get full coverage than the Rusto filler primer I'd used before. But it didn't load up the sandpaper as badly.

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The paint threw me. It was my first time using lacquer instead of enamel, and it took a lot more coats to cover the gray of the primer. [Edit: As a matter of fact, I completely emptied the white can and finally decided that I couldn't see through the undercoat any more.] And the texture was good - but no better than I'd gotten with the Rusto.

It was really pretty after painting, though. Even without the decals, this was turning into a very attractive rocket.

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It was time to apply the self-stick decals, including the big wraparound decal for the airframe. Getting that on right made me nervous, so I put it off a couple days.

Knowing I'd had some issues with the stated diameter of the rocket versus the actual diameter, I decided to check. I suspected the decal wouldn't be wide enough, and I'd have a gap at the back - no big deal. I'm glad I checked.

I used a piece of paper to measure the width of the decal, then wrapped the paper around the rocket.

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The mark on the left is where the paper meets - the actual circumference of the rocket. The mark on the right represents the width of the decal. The decal was too wide.

I could have dealt with a gap, but I definitely didn't want any overlap - that could lead to peeling.

I taped the decal down so it wouldn't move, then marked the actual width it should be with a couple pencil dots.

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I lined up my metal ruler, metal side down, then taped that in place so it wouldn't slide around.

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Then, with a hobby knife, I trimmed off the excess from one side of the decal.

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To get the decal on straight, I marked where one edge would go on the back, using aluminum angle, with the holes for the rail buttons as a guide.

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I added some dish soap to a bowl of water to dip the decals into. This would help me remove and reposition the decals if I needed to.

I had my girlfriend hold the rocket as I lined up one edge of the decal with the guide line, and slowly squeegeed the decal around the airframe with my fingers. I had to peel and reapply a few times - this took several tries to get right.

Finally, I got all the decals on, and the rocket looked great.

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I didn't get a good color match with the nose cone paint. The Rusto Apple Red would have been closer. I wonder if the lacquer paint darkened as it dried, because it sure looked closer to the true color when it was fresh.

Other than that, the rocket looked really solid and well built, and I like the way it came out.

The final detail was to add the microbuttons.

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I'll wait to tie on the nose cone until I've got some Nomex.

This was my best build so far.
 
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