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Javelin 2.5" upscale build thread

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Cabernut

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The Estes Javelin (#2005) was another one of my favorites from the 80's. After tinkering with an upscaled design here, I finally decided to start with a PSII Panavia and modify it a bit. Swap in a 38mm motor mount, glass the body tubes, set aside the Panavia fins and cut some 1/4" ply fins. Recovery harness will be about 14' 1500lb kevlar cord.

My target power range is from a big F to a big I, possibly a J? I'm not sure what the stock PS-II nose cone is OK with. I also want to be able to break mach at some point. Recovery will be motor-eject with Chute Release for the higher flights.

Here's the design:
jav_ork_3.jpg
View attachment Estes Javelin #2005 2.5in upscale_V3.ork

For the "fin strakes", I'll use 1/4" balsa since they're in no danger of flutter or impact, save on some weight. I also have a 29-38mm adapter that I'm building to go along with this so that I can use a small G or big F as well.

I've already peeled the glassine off the tubes. Once you get it started, it comes off pretty easy.




After peeling, the tube surface looks ready to absorb epoxy like a sponge..




Here, I have used the existing 1/8" fin slots as a guide to cut out the size slot I'll need.




Now I'm getting my build table set for applying the fiberglass. I'm planning on using 1 layer of 5oz, however, I'm wondering if I should add a layer of 2oz as well. I don't want to add too much weight, but also want to build in plenty of strength as well. Decisions, decisions...

As always, any input is appreciated. I'm new to the whole fiberglass thing but as i've discovered with my test piece, best way to learn is to just do it.
 

Cabernut

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Late last night I applied one layer of 5oz and one of 2oz to one of the tubes. It went OK, a bit of a hassle at first as the 5oz cloth kept trying to lift up on the end. Once the epoxy warmed up and began to get a bit more sticky, then it finally stayed down. I then quickly went over with the 2oz. Wrapped in parchment paper and let cure overnight. This morning I checked the weight and the 15.5" section weighs 108g, so not bad. Very stiff! A couple tiny bubbles are visible but all in all not too shabby.
 

Cabernut

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The other section is now curing, hopefully turns out good.

Here's the section I completed last night. Not perfect, but it's a start. There are a couple air bubbles here and there and will need a good amount of filling and sanding.

 

Cabernut

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The fin can section went OK. The strength difference is very apparent! I wasn't able to re-cut the fin slots at the "leathery" stage and had to cut them after full cure but even so, that went well with a sharp x-acto.

Now the next step is to join the two sections, trim the length and smooth out the surface before I start on the fins and motor mount.

Questions that I have now: Would the stock PS-II 2.5" coupler be strong enough? Should I add an internal layer of fiberglass to the coupler as well?
 

Cabernut

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Here's the coupler with a layer of 2oz glass inside. Much more firm now.




Checking coupler fit before epoxying in place




Here is the complete airframe after trimming to length and one sand/primer/sand cycle.




I have this extra 38mm to BT-80 centering ring, which happens to have the same OD as the glassed 2.5" tube. Looks like it would be great for making this a flat-bottomed motor mount. Which makes me wonder, would there be enough room (5mm on either side) to fit a couple screws for a Madcow-type motor retainer?

 

Cabernut

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I completed the motor mount last night. After much back and forth internally about exactly which way to go with it, I settled on a flat-bottomed design with a kevlar cord wrapped behind the front CR with loads of JB Weld holding it all together. The kevlar cord will have a nomex sheath covering it.

The motor mount tube length is about as short as I can make it, 5.5". There is a front CR and a rear one that is epoxied together with the thrust plate(a.k.a. spare CR that happened to match the OD of the airframe).

Here is a pic I took this morning after the JB Weld cured overnight - and is still curing. Not sure if you can see, but I embedded two small nuts in there for the positive retention bolts.



A bit messy, I'm no "Leo" that's for sure. Later today I'll clean this up a bit, and grease my elbows as I have a lot of sanding to do on the fins.
 

Cabernut

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I've got a lot done the past couple days.

After lots and lots of sanding, I finally have the fins shaped and smooth.






Rail buttons!




Here is the cleaned-up motor mount with a nomex sheath threaded over the kevlar leader. And yes I know it's a mess, but no one's going to see this part...




Here is the 29-38mm adapter that I made. The end cap of the 29mm retainer acts as a thrust ring in the 38mm mount.




I still need to find a couple washers or metal clips, but more or less you can see how that's going to work.





Next up is to epoxy the fins to the motor mount, then once cured, epoxy the mount into the airframe. After that, I need to cut some 1/4" balsa fin strakes and get those on.
 
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Cabernut

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Working on this thing at 3am? Yep.

I went ahead and papered the fins. Just for looks, just for looks. I wasn't looking forward to filling wood grain so I diluted a bit of Elmer's and went to town. Left them under pressure with wax sheets between. Once dry, I sanded the edges down with 400 grit for a no-seam edge.




Then I went ahead and tacked the fins in place with some foam board fin guides, and here I have some JB Weld internal fillets waiting overnight to cure.

 

K'Tesh

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Cabernut... Please keep posting on this thread. I just spotted it for the first time today...

I'm in. :pop:
 

Cabernut

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Here's a closer view of the internal JBW fillets. These ain't goin' nowhere. (except up! :))




After that had cured overnight, it was time to epoxy the mount into the airframe. Since the fins go all the way back, there wasn't space behind the fin to use a zip-tie to keep the end of the tube in complete contact with the rear CR/thrust plate. To solve this, I cut some short slots into my glassed BT-80 coupler, which happens to fit exactly over the body tube. A strip of wax paper kept it from getting glued on.




I cut out 6 fin strakes from 1/8 balsa, glued them in pairs for 3x 1/4" fins. Each one weighs just 5g.




As I write this, all three are on. Tomorrow I'll start sanding them down a little narrower in front, rounding the edges. Try and reduce drag a bit on these.

With the nose cone on and the chute stuffed in the tube, plus the 29-38mm adapter, it weighs in at 663g(23.4oz). The CG(dry) is at approx 28" and CP is at 32", so cutting close on stability. I'll probably use ~25g of weight in the nose unless it's being loaded with fat 38mm motors(big Is), in which case I'll bump it up to ~50g at the nose, which may actually help with the altitude anyway.

I've also been thinking it would be fun to upscale the engine hook retainer ring as well as a fake upscaled engine hook.:lol:
 
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Cabernut

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After much epoxy, filler and sandpaper, ready for first coat of primer.

 

K'Tesh

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Can't wait to see the finished product!
 

Cabernut

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Base coat of white is on. Now for the color scheme, should I go stock or as I painted it as a kid? Good thing I found an old home video so now I know exactly how I painted it back then...

I'm goin' full 80s. Fluorescent yellow and pink! Going to be different.




Each "vertical 3rd" will be a different color. White/Pink/Yellow. Hard to describe, but I've started masking for the first color. Masking exactly half way along an airfoiled fin isn't easy.

 

Nytrunner

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I've also been thinking it would be fun to upscale the engine hook retainer ring as well as a fake upscaled engine hook.:lol:
Dangit, Its probably too late to upvote this^^

1/2"wide aluminum strip would've been a cinch to bend into the shape.

This is coming out nice! (and is that a Leviathan sitting there in primer??)
 

K'Tesh

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I've also been thinking it would be fun to upscale the engine hook retainer ring as well as a fake upscaled engine hook.:lol:
I debated that with my Comet Chaser upscale. I decided against it. However, for the rebuild (first was impaled when something fell on it) I might. To fake it, I'd just cut a length of body tube, then cut it into thirds and glue it in place. Of course, I guess I could cut notches in the fins, then split the body tube and hide the joint under one of them. What would be funny is to add a scaled up "motor" for the "engine hook" to be clamped over. and hide the real motor inside it.
 

Cabernut

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Thanks guys. I built in the upscaled external engine hook retainer ring that's like in the original. Once it's painted, I'll fabricate an upscaled engine hook. I've thought about adding an upscaled C6-5 engine nozzle to complete the look. Makes me wonder, how many other BT-20 rockets had en external engine hook and retainer ring?

Yes, that's a Leviathan(Scion conversion) in primer. Off camera to the left is another 6 LPR rockets in primer or white base coat waiting for their turn at paint(which they've earned). I'm holding off starting any new builds until I clear my paint backlog.
 

Cabernut

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Paint is done.

Here is the white/fluorescent yellow/fluorescent pink paintjob.








I may try some better painter's tape next time as this dollar store stuff wouldn't stay down well enough on curved edges resulting in a bit of paint bleed. But that's OK, I'm just going to take it as-is and move on.




Next I'm going to find a metal strip of some sort for an upscaled engine hook :)
 

K'Tesh

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Next I'm going to find a metal strip of some sort for an upscaled engine hook :)
I'd check out my LHS, or Ace Hardware, or Michaels. They often have strips of metal for hobby uses that might fit the bill.
 

Cabernut

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I found the perfect material for an upscaled engine hook... And old special edition DVD aluminum case. Thin, brushed aluminum that can easily be cut by the score-and-bend method.

I used a piece of this once before on a trash rocket and I'll keep it handy as it's a nice workable material. Since it's not long enough for a whole 340% scaled engine hook, and since the fake hook retainer band is already on, I'll have to cut two strips from this.




Since brushed aluminum doesn't handle creases well, you can't use a tin snips to cut it. I ran a dull x-acto blade several times with a guide to score it, then gently bent it back and forth until it broke free.




Then I used 400 grit to shine it up a bit more and to de-burr the edges. I also carefully bent a tab on the end.




Here is the full-length 340% upscaled engine hook next to an original non-finger-tab kind.




And this is what it will look like next to a 340% upscaled C6-5 nozzle :)




It took me hours to make that little fake engine part. Still not done though. To get the realistic look, I peeled a spent C6-5 and scanned the peeled wrapping. From that scan, I loaded it in GIMP and spent hours cleaning up the scan, trying to make it scale up and print out as good as I could. I then printed off a paper decal to wrap on a cardstock ring I made.
 

neil_w

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That is a hoot, don't think I've ever seen anyone do that before. The engine nozzle is a great touch. :D
 

Cabernut

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But that Terminator 2 case......
was TERMINATED.

It was heavily dented anyway and didn't look good on the shelf.

It maybe April/May before I get to launch this on a G for it's maiden flight. Later this summer I plan on stuffing a big I in there which might come close to supersonic.

And while I'm thinking of it, here's the updated .ork file that reflects how it is now(aside from funky paint scheme).
View attachment Estes Javelin #2005 2.5in upscale_V4.ork
 

Cabernut

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So, now that my lower back is on the mend, I was able to spend some more time in the rocket room and finished a couple last details.

I cut my own motor retention plate out of aluminum that can hold 29 or 38mm motors. Not pretty but it will work.




Also finished up the faux engine hook and C6-5 nozzle. Practically these can only be for aesthetics. Would make a very cool screw-on motor retainer though. :cool: I'll have to keep that in mind to try some time.





And here it is, 340% upscale how I painted it in 1989 next to my regular sized clone in the stock paint scheme.




I'm itching to try this on something like an H182R or I140W this summer. Most likely it will eat a few G74s the rest of the year.
 
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