Semroc Hornet Build

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HandsomeRob

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Build threads are always fun and with a new kit arriving in the mail yesterday, I figured I'd throw my own on the pile!

I'll be doing a slightly modified Semroc Magnum Hornet I grabbed from Apogee. I've gotta say, maybe ever so slightly more expensive, but blown away by their level of service. The site is great, the info is great, their shipping time is great, they're great and worth the extra coin. Anyway.... I posted a thread a while back with some questions about adding a payload bay with ebay to this rocket and as the build costs went up, my desire to build it went down. I've got a Star Orbiter I want to do bad bad things with but I really wanted to build a stepping-stone rocket first. Something to bridge the gap between building an Estes kit largely as instructed and adding all kinds of stuff like composite reload motors, dual deploy, gps trackers, etc. So, I scaled back a bit and arrived at something that is still going to push my building skills and be fun to fly, while being (somewhat) reasonably priced and not break my heart if I send it up and it never comes back. On with the show:

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Heh, please excuse the dirty carpet, this room is generally used for storage. Here we have everything out of the box. The rocket kit, a Perfectflite Firefly altimeter, Dinochutes pouch for said altimeter since it will not be living in a payload bay Apogee ejection baffle, some 56" streamers since I'm certain this thing will float off into oblivion if I use a 'cute, Estes engine retainers because they were less expensive, and a package of plastic nosecones since I hate balsa cones. My apologies to balsa nose cone purists.

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The contents of the rocket kit. I'm very impressed with the care taken to package each component set individually. It seems a bit wasteful at first but I'll make good use of those resealable small parts baggies over time. The quality of the non-balsa parts seems pretty top notch, while the balsa bits do leave a bit to be desired. The nosecone isn't too bad, just quite rough, but I wouldn't really expect it to be a finished piece.

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Upon inspection of the fins, I came across this. I understand these things happen but with the way the fins are packaged (individually in their own parts bag, not semi-cut on a big sheet of balsa) I kinda feel like someone should have caught this and scrapped it for a different fin. That said, I do believe this fin is easily repairable and, overall, a very small gripe. I was planning on trying a different method of sealing the fins with this build, but it looks like I'll be breaking out the wood filler after all. Funny enough, I hate the wood filler I have because it's designed for really big holes, not light top coats, and it's actually going to work very will for fixing this fin. So it all works out in the end!

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As I said, I'm not a fan of balsa nose cones. Those that are, more power to ya! Additionally, I wanted the biggest cone I could put on this rocket and the conical Estes cone seemed to fit the bill, so into the cart it went. Also, it kinda looks like a stinger, and this is a Hornet, sooooo...... While I was waiting for the rocket to arrive, I cobbled together the thing as best I could on OpenRocket and, somewhat disappointingly, it sims to much higher altitudes on the olgive shaped cone. This led me to the idea that I may just put a barrel swivel (love these things) at the end of the shock cord and give myself the ability to just clip on different shaped nose cones when I want to switch it up. It would also be fun to use the altimeter to compare heights and speeds to what the simulations say. I do wish that this package came with 4 different shaped cones though. It shows 4 different ones on the package, so I know at one point it did. I knew by the product description that I was getting 2 cones of 2 different styles, so I don't feel misled in anyway, I got what I wanted. Just a thought.

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And, finally, the Apogee ejection baffle. I really like the idea of the rocket containing everything needed for flight permanently within itself, so an ejection baffle is very appealing over wadding. This will be my first time using one, so I hope it works. There's not a lot here but, again, just very high quality parts. The wood is nice and thick and durable, the tube coupler fits nice and snug inside the body tube. I'm very happy with this add-on.

That's all I've got for now. Hope to start actually building things in the next day or 2.
 
Oh, and I plan to fly it on Aerotech 24mm reloads once they come back into stock.
 
... some 56" streamers since I'm certain this thing will float off into oblivion if I use a 'cute .... and a package of plastic nosecones...

The original Centuri kit came with a plastic nose cone and a streamer. Also, it had a 18-to-24mm engine adapter, so you could use either 18 or 24 mm standard B, C or D engines. That was one of my favorite rockets back in the day, and I lost it, the nose detached from the streamer & body. The baffle should help reduce the force of the ejection charge to avoid that problem. You might want to use a little wadding, just don't need as much as you would without a baffle.

https://plans.rocketshoppe.com/centuri/cen5341/cen5341.htm
you might consider using the original decal, if you can print in on ink-jet waterslide decal paper, I always thought the little Hornet logo was really cool.

Nice to have these kits still available from SEMROC.
 
"Upon inspection of the fins, I came across this. I understand these things happen but with the way the fins are packaged (individually in their own parts bag, not semi-cut on a big sheet of balsa) I kinda feel like someone should have caught this and scrapped it for a different fin. That said, I do believe this fin is easily repairable and, overall, a very small gripe. I was planning on trying a different method of sealing the fins with this build, but it looks like I'll be breaking out the wood filler after all."

You are right, HandsomeRob, someone should have caught this but I can truly say that if you don't turn over each piece that is cut while bagging, things like this can easily be missed. Hopefully Randy will see this and compensate you for the fins that should have been scrapped or put in as extras if not too damaged for builders that don't mind fixing a few problems. Did this a few times.

Sheryl /Semroc still in my heart
 
The original Centuri kit came with a plastic nose cone and a streamer. Also, it had a 18-to-24mm engine adapter, so you could use either 18 or 24 mm standard B, C or D engines. That was one of my favorite rockets back in the day, and I lost it, the nose detached from the streamer & body. The baffle should help reduce the force of the ejection charge to avoid that problem. You might want to use a little wadding, just don't need as much as you would without a baffle.

https://plans.rocketshoppe.com/centuri/cen5341/cen5341.htm
you might consider using the original decal, if you can print in on ink-jet waterslide decal paper, I always thought the little Hornet logo was really cool.

Nice to have these kits still available from SEMROC.

Yeah! I thought I had read that somewhere, about the original coming with a streamer and plastic cone, but I could never find it again, so I thought maybe it was just my imagination.

I do have access to an ink-jet printer, if I can find some waterslide paper, I may just give that a shot. This project sort of grew out of my love for the long-discontinued Estes Yellow Jacket, which used the same hornet/wasp logo, and I'd love to get that on my rocket.

I have a slight issue with the baffle that I'll get around to posting but, yeah I may be dropping some wadding into the rocket after all....

"Upon inspection of the fins, I came across this. I understand these things happen but with the way the fins are packaged (individually in their own parts bag, not semi-cut on a big sheet of balsa) I kinda feel like someone should have caught this and scrapped it for a different fin. That said, I do believe this fin is easily repairable and, overall, a very small gripe. I was planning on trying a different method of sealing the fins with this build, but it looks like I'll be breaking out the wood filler after all."

You are right, HandsomeRob, someone should have caught this but I can truly say that if you don't turn over each piece that is cut while bagging, things like this can easily be missed. Hopefully Randy will see this and compensate you for the fins that should have been scrapped or put in as extras if not too damaged for builders that don't mind fixing a few problems. Did this a few times.

Sheryl /Semroc still in my heart

Hey, thanks for the reply, Sheryl! As I said, hopefully it's not the biggest deal in the world and some wood filler will fix it right up. Honestly, after sanding the fins smooth and hitting it with the wood filler, I'm pretty confident it's just a minor detail that adds to the story of the build.
 
Got the ejection baffle put together on Sunday. I also started on the motor mount and filling/sanding the fins and body tube spirals Monday, but those pics will have to wait.

These are all laser cut plywood pieces and I appreciated the smokey wood scent they gave off at no extra charge!
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Here the baffle itself is assembled. Just waiting for the glue to dry.... I glued it up with wood glue and, once hardened, dipped some water-thin CA glue around the joints. Not sure how much that helps, if any, but it gave me piece of mind. I ran the shock cord eyelet into the wood piece to tap the threads, removed it, ran CA glue along the threads, and reinserted. Then, after that was dry, I covered the exposed threads in wood glue. That thing is NEVER coming out!
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Fully assembled with the lower portion of the shock cord installed. You'll notice the eyelet is not perfectly parallel with the rest of the assembly. This will haunt me for the rest of my days. You'll notice the shock cord is a bit short. That's because this rocket uses a kevlar lower portion and an elastic band upper portion. Neither section are particularly long, but together, the length seems adequate. I had meant to buy a length of Kevlar cord with this rocket and just use that but, alas, I forgot, and here we are. I will say, the elastic cord has a LOT of stretch to it, so I am not too worried about it being short.
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One last bit, and this was pretty difficult to get a picture of: After assembly, I noticed there was the tiniest sliver of space not blocked by the baffle. It's damn near impossible to assure absolute alignment of all the pieces when you're assembling and I thought I had it. If I do another one of these, I may try and stick it inside the tube while the glue is still wet and get that middle piece angled just-so to eliminate any pass-through gaps. I am going to put a little dab of wood filler on the edges of the pieces at the top and bottom to close the gap. My concern is that after a few launches, that wood filler will just break off. So, ultimately, I may stuff a piece of wadding or 2 down in there anyway to protect the upper bits.
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Alright! Getting more work done!

Filled the body tube spirals and fins with woodfiller. The reason I post these pics is to show just how chunky this wood filler is and why I generally don't like it for small rocket builds. This is the Elmers Probond wood filler. The reason I don't like it is because it has large chunks of wood in it to fill large gaps. I did not know this when I bought it, I just thought "3x stronger? Must be 3x better for what I'm using it for!" Yeah, not quite.... That said, it filled the spot in the damaged fin just fine.

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They were all allowed to dry and then sanded. After sanding the fins, I noticed a big dent in one of them. I am certain this was NOT there before they were hit with the woodfiller, it's just to big to miss. I have retraced my steps and just cannot figure out where the dent came from. I was as careful as I could be but such is life.

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In order to fill the dent, I packed it with the dust left over from sanding the fins and dripped a couple drops of CA glue in and it worked like a charm!

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After the fins were sanded, they were still incredibly flimsy and pieces at the edges liked to flake off. Overall, I think the quality of balsa used is just not the best. Perfect for the price but I'm looking to push this rocket as hard as it'll go and I wish they were a bit better. In hind sight, I maybe should have just upgraded the fins but the next step restored my faith in them. I applied a light (or as light as I could) layer of thin CA to all surfaces of the fin except the root edge. I was initially just going to do the edges but after I had to fill that dent, I figured I'd just go do the whole thing on all fins.

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They're pretty rough after this step! I let the glue dry overnight (mainly because it was late and I had other things to do.) I then sanded them smooooooooooooth with 200 then 400 grit sandpaper. It too maybe 30 minutes but it felt like an eternity. However, the results are the smoothest fins I've made yet. I'm really very happy with the results. Also, it helps 'fix' a few areas where I sanded a touch too deep and took off all the wood filler. I wanted to go to finer and finer grit paper to see just how smooth I could get them but I wanted to make sure the paint still had something to stick to...

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I'm really very impressed with just how much stiffer these fins became after this process. I quite like this method and will probably continue to use it until graduating to better materials than balsa. And, yes I know I could have papered them, but, well, I didn't want to.
 
After that, I got to work finishing the motor mount. I have already epoxied the inner part of the retailer to the motor mount tube. Since this will be flying on 24/40 RMS motors (assuming they're ever back in stock....) I did not use the engine hook or engine block.

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I 'tacked' the centering rings into place with CA glue

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After that was dry, I ran a fillet of glue along the top of both centering rings and the bottom of the fore centering ring.

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Completed and with the retaining ring for the engine mount installed.

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While waiting for that to fully dry, I installed the ejection charge baffle. Let me tell you, those are some tense moments, making sure you get the glue in the right spot and get that thing all the way in before getting stuck. Woof. Here is a shot of approximate spacing within the tube. I wanted a little more than 1 body tube diameter between the baffle and the mount because I simply do not know how much the motor case will protrude when inserted since I do not yet have it. The rocket is also a little back-end heavy with all this stuff going on, so I thought if I do move it a bit farther forward that'll help the center of gravity a bit. But I had to be careful to not push it too far forward if I still wanted the streamer to fit....

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Nice looking build thread Rob!

While I understand you're not a fan of balsa, sometimes you don't have an option for something else. I actually once feared balsa nosecones, but discovered that it's not too hard to get them to look like plastic. <<<< link to tutorial

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"discovered that it's not too hard to get them to look like plastic."

K'Tesh, only if you know what you are doing and you definitely do!!!
 
"discovered that it's not too hard to get them to look like plastic."

K'Tesh, only if you know what you are doing and you definitely do!!!

Sheryl, that's why I linked to the tutorial I made. So more could do what I can. :grin:
 
My guess about the pock mark in the fin is that it was pressed onto something while sanding. I've done this a number of times.

That's all I can think of. Just bugs me that it wasn't there before I started and it was there after with no particular event I can recall that would have led to it.
 
Nice looking build thread Rob!

While I understand you're not a fan of balsa, sometimes you don't have an option for something else. I actually once feared balsa nosecones, but discovered that it's not too hard to get them to look like plastic. <<<< link to tutorial

11511492126_6e0c940689.jpg

K'Tesh, yes!! I've read through some of your threads, they are a wealth of information and tips.

Since I still like the idea of setting this rocket up to have interchangeable nosecones, and I have literally 5 cones kicking about for this 1 rocket, what I'm thinking I'll do is make the plastic olgive and conical cones, AND the balsa, all able to fly with this rocket. Assuming they don't pop off under ejection, it'll be fun to see which cone the rocket really does fly highest on.
 
And I REALLY like the sharpie trick. Wish I had seen that before doing my fins!
 
K'Tesh, yes!! I've read through some of your threads, they are a wealth of information and tips.

Since I still like the idea of setting this rocket up to have interchangeable nosecones, and I have literally 5 cones kicking about for this 1 rocket, what I'm thinking I'll do is make the plastic olgive and conical cones, AND the balsa, all able to fly with this rocket. Assuming they don't pop off under ejection, it'll be fun to see which cone the rocket really does fly highest on.

Thanks!

I'm going to guess that it'll go highest on a parabolic nosecone (presuming that all other things would be equal).

And I REALLY like the sharpie trick. Wish I had seen that before doing my fins!

Another trick is to paper the fins...
 
This set of pics came out terribly and I do apologize for that but I wanted to make sure I posted SOMETHING this week. Fins are attached and filleted. The rocket body is ready for primer and paint but it's raining and will probably be super humid for the next few days. I hope to take this down time to prep all 3 nose cones for paint as well.

One of the fins is ever-so crooked and I'm so frustrated about that. I guess that's what I get for talking bad about them online. They showed me....
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A dry fit of the 2 plastic nose cones just to see what the finished rocket will look like. I did not include the balsa cone, as that has yet to get any kind of prep, but it will be finished as well. I must have taken these pics 10 times each and these were the ones that came out in focus the most. Again, sorry.
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Alright, so, it's been a little while. Between work and social obligations, my posting has had to take a back seat. As well as progress on the rocket, unfortunately. But! that doesn't mean I've been entirely inactive!

First coat of primer blasted and sanded:
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Second coat of primer blasted and sanded:
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I sanded a little too much on some spots of the fins but assumed it'd be fine and did not want to re-hit some parts to touch up the primer. We all know what happens when you assume. However, I'm really trying to get this thing ready by the club launch in November. Painting requires patience...

First coat of color laid down:
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Although this paint is called "Glowing Lemon Yellow" and the cap reflects that title, it's spraying a lot more green than yellow. Something that certainly could have helped would be a white base coat. I searched the house but we're fresh out of white spray paint. As I laid more and more light coats over the gray primer, it started to brighten up a bit. I'm hoping with subsequent coats, it'll continue to get more yellow and less green.

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I managed to get small runs on BOTH cones even though I was building layers. The black sprayed a lot heavier than the yellow, which caught me off guard at first, and I think trying to change techniques came too little too late.

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The joys of spraying in the great outdoors! There's a few flecks of junk in the body I'll have to pick out/sand out but that was expected. You can also just barely see on the top fin, where I sanded down below the primer. Honestly, I thought the paint would be thick enough to cover and didn't feel like waiting for yet another coat of primer to dry and be resanded before hitting the rocket with color. I REALLY hope that covers with later coats. All in all, a little more patience, and I would have had a better first coat. But I intended all along to lightly sand and add 2nd and probably 3rd coats, so, not too big a deal. I'll let the colors set for 24-48 hours and then sand and spray some more.

Finally, thanks to one of the great members of this board, I was able to acquire a 24mm RMS casing! Now to get a reload for it. Not really sure what I want to launch this thing on first.....

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how is the weight turning out? if you think the pad weight will be under 8oz. a D12 or D15 should work nicely, next step up would be either an E18 or E28.
Rex
 
I was thinking a D would be a wise place to start. Even with the addition of an ejection baffle and altimeter, I can't imagine it'll get heavy enough to "need" an E to push it off the pad. I had intended to weigh everything before paint but it just slipped my mind. Now it's all in pieces again and I'll probably just wait until it's finished for a total weight.

I was also eyeballing the E18W-7 aerotech reload. It comes in a 3 pack and as long as the rocket survives the first flight, I kinda think I'd get bored of the Ds really quickly.
 
I haven't fallen off the face of the Earth, just haven't had time to sit and make a post. So, this one will actually wrap everything up, as i was able to send the bird up this weekend!

Continuing on with my paint woes, it's been many weeks of sanding and polishing as I get free time. Something that frustrated me was, as I sanded and polished, what was coming off the rocket WAS the neon yellow I wanted so badly. Again, totally my inexperience showing by using a gray primer instead of a white, or white base coat. That said, it does POP in the sunlight and look much less pea-soup green. It's actually grown on me quite a bit.

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I wish this shot had been a bit more in focus but, unfortunately, it is not.
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Put together my first reload for this as well. An Aerotech E18-7W
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Ignitor installed, capped, and ready for flight!
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Took it to the club launch on Saturday and, although I wanted one more coat of clear, the rocket was basically ready to fly. It got a coat of Duplicolor Clear FX and looked fantastic in person! The whole rocket got a coat of it but it was difficult to capture it on the yellow (green) but you can see it here on the fin and nose cone.
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Fully loaded and ready for flight! (I apparently did not take any pictures of the streamer used for recovery.)
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Success!!
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Well......sort of.

First, this thing went like stink on that RMS motor. It shot off the pad like, well, a rocket, and disappeared from sight shortly after. I did not fly it with the altimeter because I wanted to make sure everything worked first. After a few seconds, it slowly came back into view and I could tell everything had gone perfectly. As it was descending, I saw a piece flutter away from it that quickly vanished from sight. I assumed it was the nosecone, because everything else seemed to still be coming down together. When I reached the rocket after landing, I could see it was all there.....except for about half the streamer. Apparently, that's what broke apart during descent. Of about 54 inches of reflective mylar streamer, only about 20 inches remain. Not a huge loss and I was happy to see my installation method of using packing tape to attach a nylon string worked flawlessly.

Upon close inspection after getting back home, I do notice some more dings that need tending to. The recovery was much more violent than I initially thought.

Although I don't think it's actually damaged, the 2 fins that stuck the landing looked like they took a bigger blow than they could handle and there's some cracking around them. You can see it even chipped the paint out a bit. They feel like they're on solid but I will probably run a little clear epoxy over these areas to make sure they don't break off. You can see it still has some dirt left on it from the field. The fin on the left is the other one that shows some cracking down towards the bottom. You can also kind of make out the sparkle in the paint haha.
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Another spot that needs repair is the elastic shock cord. This separation did NOT happen while in the air. I was inspecting the cord post-flight and noticed a very slight char spot on it, as soon as I pulled it taught to take a better look, it snapped like you see here. I was actually really impressed that the ejection baffle and 1 piece of wadding did their job as only this tiny spot on the shock cord showed any signs of burns. everything above it looks brand new and clean.
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All-in-all, I walk away from the first flight needing to do some minor repairs and upgrade the recovery system to a nylon streamer and, most likely a long length of kevlar for the extended shock cord. I successfully took an already excellent kit from Semroc, modified it with an ejection baffle, screw type motor mount, and the ability to swap nosecones and recovery systems. I also successfully put together and flew my first RMS motor. Although not as close to perfect as I would like, I gained a ton of experience on this build and will definitely be taking the next step to mid-power with my next build.
 
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