Rocwerks Reactor Build Thread

View attachment 188883
So TRF user Thobin has been selling off his remaining supplies of his 2 Rocwerks kits; the Reactor (24mm) and the Tomahawk (29mm).
He's selling them at below cost to clear out his inventory, and I couldn't resist. Heck, even if I didn't want to build the kits, I couldn't buy the parts for the price he's selling them at!
Well, the kits came in about a week ago, and I'm pretty excited to build them. The Tomahawk is basically a long version of the Loc Lil' Nuke with TTW fins that can be swept forward or aft. I love my Lil Nuke, but always wished it had TTW fins for a little more structure so I could really push it. Also, I always wanted a longer version so I could shove in a 6-Grain CTI motor without risking instability. Well, the Tomahawk accomplishes both of those with a pretty sweet design; simple but unique.
After a quick couple exchanges with Thobin, I decided to build the Reactor first, and I'm posting this as my first build thread on TRF. It's a great kit, and a lot of what I'll be doing with it are things that someone new to mid-power can learn from. So, if you'll bear with me, I'll be posting as I go. Feel free to post questions, comments, and what-not...
Fair warning, I'll be "Over-Building" this kit. I know it's unnecessary, but it's just how I build, and it ensures that everything lasts for as long as I don't lose it. I flew my Lil' Nuke straight into the ground (literally), and only had to replace the nosecone. Over-building, to me, is just worth it in the end. I might lose some altitude, but I'm more focused on preserving my investment of time and energy. I'll try to point out where I know I'm over-doing it so that anyone trying to learn along the way can understand what's necessary and what's overkill. Of course, There's lots of room for debate on most techniques at the low and mid power range. Hope you enjoy the thread!
-Erik

Some Pre-Build considerations...
Motor retainer vs. hook and thrust ring
-Ditch the thrust ring (make one out of tape for Estes engines)
-Retainer will fit where it needs to go, and ensure safe retention of pricey reload casings. My 24/40 was the first casing I ever bought, and I’ve had it since I was 15. I’d rather not lose it. With the thrust ring, I’m limited to the length of the motor casing I can put into the rocket, and I like to leave my options open. Built properly, I may be able to get a 6-Grain CTI casing in the pipe. It may have disastrous results, but it’ll be fun to watch! In the meantime, eliminating the forward thrust ring allows me to use just about every 24mm motor available to me (including the CTI 3-grain, and my favorite AT 24/40 reloads)
Launch guidance?
-Lugs v Rail buttons debate… I’m not going to get into that here, you can have your own argument elsewhere. For me, the debate it dead. With the advent of mini and micro rails and rail buttons, I’ll never build using lugs again. I tend not to launch tiny rockets, so I’ll probably only ever use the mini buttons and the standard 1010 (until I build some massive stuff on 1515).
-Both lugs and buttons? … I’ve considered using both lugs and buttons, and it really is a nice solution for those who want to be super flexible. I personally want to keep as few parts sticking out of my rocket as possible.
-Of course, the MAJOR contributing factor is the availability of rails where I launch. This rocket is definitely small enough for me to launch at home at nearby schoolyards and such, so now I have incentive to build a pad that will hold a rail. Also, I launch mostly at TWA/Whoosh (Bong, WI) and QCRS (Princeton, IL) where rails are easily available. I’ve also launched with the Fox Valley Rocketeers out at a field near Woodstock, IL, and that was all personal launch pads; therefore, if I just build my own pad, I’ll make it portable enough to bring with.
-Conclusion: Rail buttons… For me, I’ll go with rail buttons only because, well, I need some incentive to build a launch pad with rails anyway. The rail buttons will be the last thing I attach during the build, so between now and then, I can decide if I want to go with mini or 1010 buttons.
Shock cord
-Elastic is included…
-I’ve become fond of the Kevlar harness method, even in my low and mid power rockets. I actually like using elastic in low power rockets (I know, start the arguing now)… But seriously, it’s low power, and with delay charges being so inflexible with low power motors, I need something that will give a little at chute deployment. Using the harness method, I have access to the shock cord such that, should it ever break or become too brittle, I can change it out without having to cut into the body tube and do major surgery. Or, should anyone fully convince me that elastic is the devil, I’ll be able to change it out easily. Also, with a Kevlar harness, the chances of zippering are reduced.
Baffle…
-This kit comes with a baffle, and there are MANY pros and cons to using baffles. I’ve read several threads on TRF about the topic and decided to go ahead and use this baffle assembly.
-Why use a baffle? I won’t have to mess with dog barf, no need to get yet another Nomex protector (although I have a sweet Nomex pant leg that I can cut up), and I’ve never used one before. The kit was designed with a baffle, so why not?
-Another reason is that it will make mounting the Kevlar harness all that much easier since I’ll just mount it inside the baffle tube, giving it tremendous strength without risking any sort of zipper damage to the lower portion of the rocket.
Summary:
-I’m ditching the hook and thrust ring for an Estes motor retainer
-I’m using rail buttons only, ditching the lugs
-I’m using a Kevlar harness method to attached the elastic shock cord
-I’m using the stock baffle just because I want to.

Step 1: Check the package for parts
So I learned just recently how important it is to check your parts before building. I bought a Loc Aura, and the fins that I cut were cut incorrectly. Loc responded by sending th correct fins, and I got them just a couple days later, but just in case, I was glad I had checked before building anything.

The Reactor comes VERY complete with some pretty awesome parts! The decals are StickerShock (excellent! Go to StickerShock23.com to get yours or order a custom set). The kit includes a TopFlight (excellent again! Check them out here) 18" X-Form chute in Black and Green, plywood centering rings, baffle parts, etc. The included directions are some of the best I've seen in rocket kits. Excellent diagrams and clear directions. Definitely a bonus. Some manufacturers out there have great kits but minimalistic directions. Hey, we all adjust builds to our liking anyway, but it's nice to see CLEAR directions when we buy kits. All great stuff, and I couldn't believe what came in the kir for the price!
In the picture, at the bottom, you'll notice that I have my Estes motor retainer which I picked up from my Local Hobby Store (LHS). They don't normally carry these, but after talking with the owner, he said he'll order anything I need. After checking out my usual rocketry vendor (Wildman) prices on motors, he even agreed to lower prices a bit to be more competitive! You'll also notice my 3-piece Nylon rail buttons that I got from Rail-Buttons.com; I bought 30 which is far more than I'll need for a long time, and he tossed in a freebie with the order (I had also ordered some mini rail buttons for some smaller rockets I'll be building over the winter). Finally, there's a length of 1/4" Kevlar I'll be using for the harness. This is FAR stronger than I will ever need with this kit, but I had some extra lying around, and it's too small a length to use on anything that will actually need 1/4" Kevlar, so I figured I might as well use it here.
Okay, so that's all the parts, and all the shout-outs. If you're new to mid-power, check out those sources for sure!
Next up is nosecone prep. I'll be using thin CA, and I'll post after I do it and snap some pictures.

Nosecone Prep
Harden Balsa Nosecone (CA method)
-Safety First! I wore goggles and Nitrile gloves to protect myself during this process. I also stuck a toothpick in the bottom of the nosecone so I had something to hold other than the nosecone itself. Helped to spin the nosecone easily, too.

-I dripped Super Thin CA starting up at the shoulder and let it run down the length of the nosecone. I made sure to let drips fall on the cardboard on the floor and not my feet. Interestingly, as the CA started curing, there were little wisps of smoke curling up right at my face; I was sure to avoid breathing those in… When it nosecone was covered in CA, it was fairly easy to see where I had missed and I just dripped some more on that spot.

-After covering the nosecone in CA, I placed it on a spare piece of 1” PVC I had sitting around, with the toothpick in the middle. Set it aside to cure fully.

-After the CA has fully cured, I colored the whole thing with a sharpie marker. This way, I could keep track of my sanding, if I was going too deep or not.

-Then, I sanded using 150 grit sandpaper until most of the black was gone. Much of the CA was also gone, but I now had a smooth nosecone.
-I repeated the CA application and set it to cure overnight. In the morning, the nosecone required only a little sanding to smooth out the bumps and ridges leftover by CA application. This time, I sanded using 220 grit sandpaper to give a smoother finish yet still leave enough “teeth” for the Primer to adhere well later.
Fit nosecone shoulder to body tube
-Prior to handling the nosecone, I couldn’t get it into the body tube. After handling and sanding the nosecone, it now fit, but very snugly. Using 150 grit sandpaper, I carefully sanded the shoulder until it fit just right.
DO NOT add hardwood plug yet… I will hold off on adding the hardwood plug (with eyebolt) until the very end of the build, once I balance the rocket.

Prep Fins for Assembly
Filler to smooth
-Painting starts now! Surface prep is everything to getting the finish you want, so before I do anything with the fins, I create a smooth surface to work with. I just use Elmer’s Carpenter’s Wood Filler for this step. Some people use sanding sealer, some people paper the fins. I just use Elmer’s CWF…

-I use a spare container from electrical tape for all my putty needs. A little dollop of CWF and a small drizzle of water to thin it just a little is perfect. Just the consistency of a thick milkshake is perfect for this application.

-I glop it on as a big hunk then spread it using a small putty knife. Once it’s spread roughly everywhere, I use a larger putty knife to scrape it all even. I’m not going to scrape it all off here, just even it out to make sanding easier. I leave it on pretty thick because sanding CWF is a breeze, and it does shrink slightly as it dries. Leaving it thick ensures that it should only take one application to get the finish I need. Very importantly, I do not apply CWF to the root edge or any of the fin that will go through the wall. I want that wood bare for internal fillets.

-Once all the surfaces on the fins are covered (don’t worry about the edges, those are going bye-bye later anyway), I lay the fins down on a drying rack I made out of ½” staples and a piece of cardboard (an old trick my dad uses for varnishing his carvings).

-After letting the CWF dry overnight I started sanding. I have learned to let the CWF dry far longer than I want to. The drier, the better. If it’s not fully dry, I’ll end up having to do a second application to fill in gaps created during sanding. When it’s fully dry, this happens much less because it doesn’t come off in clumps.
-I first sanded down the CWF to make the fin surfaces smooth using 220 grit sand paper. This makes for more sanding than a rougher sandpaper, but it ensures that I don’t oversand anything and leaves me with a great surface for the first coat of primer.

Bevel Fin edges
-Once all the fin surfaces are smooth, I shape the edges of the fins.
-For the reactor, I’ll be shaping all 3 edges of the fins since they are all leading or trailing edges.
-I use a piece of 2x4 wrapped in 150 grit sandpaper. 220 works, but 150 gets the job done much quicker.
-I place the edge I will shape along the edge of a table and just hold it in place with my hand. Then, I hold the sanding block at an angle just above my fingertips and sand until I get halfway through the edge of the fin. Next, I flip the fin over and repeat the process for the other side. This procedure gives me a nice sharp edge that’s close enough to perfect for my purposes.
-I repeat this procedure for all edges on all fins.

*Quick tip… I do not have a good power sander, so this process works best for me. However, if I had a belt, disc, or drum sander, I’m sure a jig of some sort could be used.
*Quick tip #2… Shaping the edges of the fins in this manner isn’t necessary. You can also just round off the edges a little using sandpaper
-Finally, when all fin edges have been shaped, I use Super Thin CA to seal and strengthen the edges to protect them.
Seal? Sanding sealer/Minwax
In the past, I’ve sealed balsa fins with polyurethane. Here, with plywood fins, I don’t feel it’s necessary to seal the fins at all. The primer before I paint will seal them up just fine. Some people use sanding sealer, but again, I think the primer will do the job.

Cutting fin slots
Measure fin slots using included fin guide
-First, I aligned the forward and aft body tubes so that the spirals all align. No particular reason, I’m just obsessive like that. I drew a line straight down the tubes so that they can be aligned easily later and to give me a straight line to start with for the fin slots. To draw the straight line, I just use my handy Carpenter’s Scale. Because it is angled, it finds true straight on a curved body tube. Works great for just about any size tube until you get into monster size…

-Then I used the included fin alignment guide to mark the start of each fin slot 1” up from the bottom of the tube. To get the width right, it’s handy to know that the arrows on this particular fin guide were 1/8” wide, so I marked the center, left and right of each fin slot location. Then, I measured 1 ¾” up from there and repeated the process after sliding the guide up to that line.
-I then used my scale to mark a line for each side of each fin slot, creating a straight and true line for each cut I would have to make. I checked, double-checked, and triple-checked the fin slots by making sure that as I twisted the guide, each slot lined up with the fin lines no matter how I lined it up.

Cut one fin slot using razor
-I dry fit the centering rings on the motor mount tube and placed it in the body tube during this step to give the tube shape and strength as I cut the fin slots.
-Then, I used the scale as a straight edge to cut the first line with a fresh blade in my razor knife. I cut gently at first, just one layer of paper. I then did the other side of the slot with a gentle first cut, again using the straight edge. I then repeatedly cut a little deeper with each pass, taking about 6-8 passes to get all the way through the tube. This way, I wasn’t putting too much pressure on the tube, and ensuring a clean cut. Once both sides were cut, I just cut the 1/8” front and back with several passes being careful not to cut beyond the lines. Finally, I popped out the slot, and viola! My first ever hand-cut fin slot. Not nearly as difficult as I thought it would be.

Test fit a fin
-I picked a fin and placed it in the slot. It took just a little bit of force to get it in, but once in, it was snug and fit great! Only slight gaps where my cut weren’t exactly straight, but fin fillets will take care of that later.
Measure again (because what if my cut was off slightly?)
-Before cutting the next slot, I double checked my measurements just to be sure… If my cut was too wide or off in one direction, I wanted to be sure the cuts were still aligned at the center of each fin.
Cut second and third fin slot
-I repeated the above process for the second and third fin slots.
-Once all fin slots were cut, I used the fin alignment guide to mark a launch lug line.
-Overall, far easier than I thought it was going to be!

Motor Mount
-I decided to replace the stock 24mm tube with a slightly longer one I had sitting around from another build. I measured exactly where I wanted the motor mount tube to go with the Estes motor retainer. It’s important to consider this before placing rings because if the retainer is too far up into the body tube, it’ll be difficult to screw it on and off once it’s in place. In this case, with the motor mount flush with the end of the body tube, it will stick out just enough to still get a good grip.
-I waited to do fin slots first because the slots will determine the placement of my centering rings. I held the motor mount tube flush with the end of the body tube and even with one of the fin slots and marked where the fin will attach to the motor mount. Easy way to see exactly where I want the centering rings. As long as I place the forward centering ring ahead of the fin mark, I know that the centering ring won’t interfere with the fin but still be placed close enough to dam the internal fillets.

-With the marking, I scuffed up the area of the mount where the forward ring would attach. I slid on the first centering ring (no need for notches since I’m not using the engine hook) then smeared some 15 minute epoxy where the ring would attach. I slid the ring up the tube, twisting as I went. I slid the ring just past where it would go, grabbing the epoxy, then slid it back down to its final position. I set it upright to cure.

Baffle Assembly
Attach baffle tubes together
-I marked each baffle tube at 2 ½” as the directions state. I then scuffed one side of each tube and glued them together with good old Titebond wood glue. Certainly no epoxy needed here as these are not structural elements. I used blue painter’s tape to hold them together while they dried.
Measure Kevlar harness
-*My ¼” Tubular Kevlar harness is definitely overkill for this size rocket. All in, this will weigh only 8 to 10 ounces. Assuming you use the including eyebolt, now would be the time to drill a 1/8” hole, place the eyebolt and epoxy it in place on the forward baffle bulkhead. This would actually be much simpler to do. The only drawback is that, to gain access to the shockcord mount later, you’ll need to reach through 8 inches of body tube or cut it…
-Since I’m using a Kevlar harness, I first need to measure the length I will need. No need for rulers here. I slide the coupler tube into the forward section of body tube and lay down the Kevlar next to the pieces. I don’t want the Kevlar going all the way to the bottom of the baffle, so I laid it down with about 1 inch below the body tube. Then I made a loop next to the tube and marked the Kevlar where I needed to cut. A harness should come up to the top of the body tube but not extend beyond it. So, within about a half inch either way is fine and will function the same. Too short and you won’t be able to reach it easily. Too long, and you defeat the purpose of the harness since it will act just like a single length shock cord.
-I made my cut and bam, Kevlar harness ready to go.

Drill holes for Kevlar Harness
-To attach the harness inside the baffle, I’ll need two holes as close to the edge of the bulkhead as I’m willing to go.
-I used a 3/16” bit to drill the two holes near the edge of the bulkhead. In retrospect, I could’ve gone much closer, but it’s not of much importance.
-I then pulled the Kevlar through the holes.
Epoxy harness onto coupler
-To make sure I epoxy the Kevlar in the right place after cutting, I put the baffle coupler, bulkhead, and Kevlar into the forward body tube to the same length I will use when finished. I pulled the Kevlar into a loop to where I wanted it then used masking tape to hold the first line in place. Then, again making sure the Kevlar loop is just the right height, I taped the second end inside the baffle.

-Then, I pulled the bulkhead up to the top of the loop just to get it out of the way. Then, I used tape to hold the forward end of the Kevlar so I could remove the lower piece of tape.
-I then mixed up a batch of 15 minute epoxy and covered the first Kevlar strap inside the baffle and set it aside to cure. Once that had set up, I repeated the procedure for the second. After both were set up, I pulled all the tape off.

Epoxy forward bulkhead
-After letting the Kevlar harness set up for about 30 minutes (not a full cure, but enough that as I jostle the straps around, they will stay in place), I mixed some 15 minute epoxy for attaching the forward bulkhead.
-I started by spreading just a little epoxy around one end of one of the baffle tubes. Then I slid it into the offset hole; I twisted and pulled it back and forth just a little to be sure the entire hole had a bead of epoxy. I left about 1/8” of baffle tube sticking out the forward end of the bulkhead.
-I then spread some epoxy on the inside of the forward end of the baffle tube, just at the very front. I wanted the epoxy to run down onto the bulkhead when I stood it upright.
-Then, I slid the forward bulkhead into place and held it upright for about 15 minutes. I would’ve set it somewhere, but since the bulkhead doesn’t slide into the coupler, the tube kept sliding off the bulkhead. I used the other offset bulkhead to hold the baffle tubes in the right position while I waited for everything to set up.
-After 15 minutes, I removed the aft bulkhead and check to be sure everything had set up nicely. In the picture, you can see that the bulkhead has a nice bead of epoxy on the forward end. It doesn’t have to be much at all, just enough to kind of hold things in place. When the baffle is epoxied into the body tube, those joints will hold everything together.

Epoxy aft bulkhead
-After ensuring everything went well with the forward bulkhead, I used the same procedure to attach the aft bulkhead.
-Since the holes I drill for the Kevlar harness were rather large, I used some of my leftover epoxy on this step to seal up the holes at the top of the forward bulkhead.
-Set aside to cure, and the baffle assembly is done.

Join the two body tubes
Prep Baffle – Dry fit/sand if necessary
-Dry fit the baffle into both halves of the body tube. Mine required a little sanding from excess epoxy that leaked during the gluing of the baffle assembly.
-Make sure you have marked 2” (halfway) on the baffle to ensure there is enough coupler in each end of the body tube.
Tuck Kevlar harness into baffle tube
-I tucked the harness very loosely into the forward baffle tube to keep it out of the way of the epoxy as I slid the baffle in. Random epoxy on the Kevlar would weaken it.
Epoxy the baffle in the body tubes.
-This can be done in one step or two. I did it all at once. Mix up a batch of epoxy and spread it about ¼” to ½” inch up each of the body tubes. I spread about a ½” worth on epoxy on each, but not much. What looks like only a little is plenty for this operation. Too much epoxy will make a mess, be unnecessary, and drip all over the inside of the body tube.
-I started with the baffle going into the after body tube. The trick here is to twist and slide the baffle in at the same time. When it reaches the halfway mark, it’s where you want it to be.
-When sliding the forward body tube onto the baffle, be sure to hold the baffle assembly so it doesn’t slide further into the aft body tube. No matter how you do it, the goal here is to have half the coupler in the forward body tube and half in the aft.
-Finally, I aligned the body tubes using the mark I made earlier.

Attach fins
-Scuff motor mount
-Tape lower Centering Ring with Scotch tape so that you can pull it off later for internal fillets

-Slide mount into tube to correct depth…
-Mount 3 fins, 1 at a time, using epoxy and your favorite fin jig

Looks great very thorough build. I like it and not because it's one of mine. I love to watch the build processes of others.


TA

Sent from my SPH-L720 using Rocketry Forum mobile app

Hey Erik,

Great build thread so far. Are you already done and launching or do you still have to finish. I just bough a couple of these nice kids from TA and would like to start building with my kids, and soon to do a large build with Scouts after ironing out my beginner wrinkles!

Brian

caveman said:

Hey Erik,

Great build thread so far. Are you already done and launching or do you still have to finish. I just bough a couple of these nice kids from TA and would like to start building with my kids, and soon to do a large build with Scouts after ironing out my beginner wrinkles!

Brian

Click to expand...

Never realized that I didn't finish the thread! Yeah, it's done and has several fantastic flights. Let me know if you have any questions along the way. I'll finish up this thread on the next day or two.

Where did you get/make that fin jig? Looks like you would put washers between the jig boards that are the same thickness as your fins to keep the fins centered to the BT when clamped to the board? And of course the 45 degree chamfer would center the BT. Might have to build one of those. Is there a limit to tube diameter that you've found? Sorry for all of the questions, new to this tube building thing. I'm used to very flat surfaces for RC sailplanes.

Thank You
Brian

caveman said:

Where did you get/make that fin jig? Looks like you would put washers between the jig boards that are the same thickness as your fins to keep the fins centered to the BT when clamped to the board? And of course the 45 degree chamfer would center the BT. Might have to build one of those. Is there a limit to tube diameter that you've found? Sorry for all of the questions, new to this tube building thing. I'm used to very flat surfaces for RC sailplanes.

Thank You
Brian

Click to expand...

I made that one out of 3/4" MDF. Yes, you definitely need to separate the boards the same thickness as the fin material. I tend to use scrap wood or stack popsicle sticks. The whole build took me like half an hour. I've done up to and including 4" tubes on that. However, when I built the jig, I made two, and made them such that when I need, I can put them together and make a larger one. It'll come in handy when I build the 8" Gizmo XL-DD I have waiting. I found it by googling "fin alignment jig"... There was all this controversy about some knockoff jig... But this one is simple, flexible, and it serves as a stand for fillets...
...
I've been working on a couple builds... One will be posted on Wednesday in its entirety...

Back to the build...
After fins are attached...

Internal Fillets
-Remove aft centering ring using the tape tabs
-mix epoxy and pour along two internal fillets,
-set aside to cure
-rotate and repeat x2
-then, put some epoxy inside the body tube and slide the rear centering ring into place. Be sure to leave enough room for the motor retainer.
-mix a bit of JB Weld and smear it evenly on the motor tube.
-slide the motor retainer into place, twisting as you go to ensure even coverage.
-set aside to cure.

Body tube finishing
-fill spiral grooves as you choose. I use the same CWF as described above for the fins
-sand the CWF smooth
-external fillets... Tape off, mix and pour epoxy, wait for it to set about 20-30 minutes, pull shape, pull tape
-primer using a high build primer, sand smooth and repeat until satisfied.
-base color coat should be yellow on all parts, nice and easy.
-when yellow dries, mask everything except the fins. Shoot gloss black on the fins and the nosecone
-apply decals per instructions.
-Done!

Almost forgot...
Tie the elastic shock cord to both the y harness and the nosecone. I tied the chute to a swivel and tied that to the shock cord.

I've flown this bird several, several times now and love it. Last flight, it got hung in a tree about 40ft up. DJs and I got it down using a tree hook pulling on a fin. Pulling hard... Got it back with very little damage, basically just chipped paint. Still perfectly flyable. It's a fun little flyer on everything from E9s to F240s...