Build thread: 5.3:1 sport scale Super Deluxe #2 Skywriter XL Premium Pro Max - Limited Edition

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neil_w

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First Fin

I scuffed up the tab and the root edge of the first fin with 110 grit paper, to hopefully give the epoxy something to grab.
First fin-1.jpg

Then I applied my BSI 15 minute epoxy (carefully!) into the slot, both on the motor mount and the sides. Then added another bead onto the fin root edge, and in it goes. Went cleanly, but then I decided that I could possibly get a wee bit of epoxy into the gaps around the edge of the fin, which caused a tiny bit to get a bit higher on the fin, and *then* I thought I could just clean it off with some alcohol... that did not work, and I ended up smearing the bottom of the fin. We'll see, maybe some additional Future will clear it up later. No biggie. On the other fins I will *not* attempt to fill the gaps with epoxy; rather, I will apply a bead of medium CA, which is what I had intended to do in the first place.

No jig used here, the fin only goes into the very tight slot one way, and that is *straight*.

This pic gives an idea what it'll look like (and if you zoom in you can see the mess near the base of the fin.)
First fin-2.jpg

Given my inability apply a proper fillet either inside or out, I do wonder how strong the fins will be. Fortunately, being so far from the rear, they shouldn't absorb too much landing impact.

One down, two to go.
 

neil_w

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Strips of tape to keep the epoxy off the fins and body tube?
Yeah, that would seem to be smart. I was a little nervous about applying the tap on top of the Future, but I guess there shouldn't be any reason for concern since it's been many days and the basement where I'm working is cool.

Question: should I try to apply some tiny epoxy fillets there, or just use the tape to keep the epoxy away, and follow up with CA afterwards?
 

mbeels

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Went cleanly, but then I decided that I could possibly get a wee bit of epoxy into the gaps around the edge of the fin, which caused a tiny bit to get a bit higher on the fin, and *then* I thought I could just clean it off with some alcohol... that did not work, and I ended up smearing the bottom of the fin.
I've done that before. "Oh a little bug landed on my wet paint, I'll just flick it off with my fingers. Oops, now I've put a finger smear in my paint, let me just dab that, oh no, dropped the rocket with wet paint in the grass." I just leave bugs be, now.
 

mbeels

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Question: should I try to apply some tiny epoxy fillets there, or just use the tape to keep the epoxy away, and follow up with CA afterwards?
I don't know, how well does CA adhere to that plastic? I have seen CA really fog up some clear plastics, but maybe the tape would protect against that.
 

neil_w

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I don't know, how well does CA adhere to that plastic? I have seen CA really fog up some clear plastics, but maybe the tape would protect against that.
The SuperGold won’t fog as for adhering... well it doesn’t necessarily have to, if it fills the gaps a bit by adhering to the wood and paper forming the slot.

as I think more, I’m *not* going to try epoxy fillets. This the wrong occasion to be my first attempt. I will tape it off and fill with CA later on.
 

kuririn

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Strips on the fins and tube spaced apart the width of your desired fillets.
Lay the epoxy down. If you have a micro syringe that would be nice.
Since it's a small fillet, smooth it with a gloved pinky finger or Q tip and alcohol.
Before it starts setting up take off the tape and don't touch it till it cures.
Also, I just built a Falcon 9 with TTW lexan fins. Attached with thick CA.
I have found that some brands of thick CA can craze clear plastic.
I think it's the fumes off gassing when it's curing.
I'm considering extending the paint line up onto the fin about 1 or 2 mm.
I'm thinking it might conceal the slot when viewed from an angle, as well as the "craziness".
Is that a word? 😄
0711201132[1].jpg
 

neil_w

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Strips on the fins and tube spaced apart the width of your desired fillets.
Lay the epoxy down. If you have a micro syringe that would be nice.
Since it's a small fillet, smooth it with a gloved pinky finger or Q tip and alcohol.
I understand the process, but since this is basically a finished rocket it is not the best subject for learning and/or experimentation.
I have found that some brands of thick CA can craze clear plastic.
I think it's the fumes off gassing when it's curing.
SuperGold will not, which is I believe it's primary reason for existence. I've been using it because it is blessedly fume free, in this case I kill two birds with one stone.

Attachment is epoxy, CA just to fill the gaps around the fin because I wasn't able to get the slots 100% perfectly smooth and clean.

I'm thinking it might conceal the slot when viewed from an angle, as well as the "craziness".
Is that a word? 😄
I would go with "crazedness", but either way. ;)
 

neil_w

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Second fin came out (or, went in) clean. I masked the fin with skinny Tamiya tape, but not the body (a small bit of excess clear epoxy is pretty much invisible on the body.) The second slot was a bit looser, still didn't need a jig.
Fin 2.jpg
 

neil_w

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Last fin is on clean. That one had a lot of slop in the slot, I hope it'll be pretty solid when cured. Filling the gaps with *something* is a definite requirement; tomorrow I will try it with the SuperGold.

Feels good to have the fins on, despite all the imperfections. The look clear enough, and I think on the pad and in the air it will pretty much just look like a pencil.

Full pics when finished.
 

afadeev

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Question: should I try to apply some tiny epoxy fillets there, or just use the tape to keep the epoxy away, and follow up with CA afterwards?
Whatever you choose to do, it will be for decorative purposes only.
Epoxy on top of epoxy will go on nicely, and epoxy can be smoothed and shaped with a gloved finger that has been dipped in alcohol.
CA tends to spread whichever way it wants, and can't be shaped.

There is no point in structurally reinforcing Lexan fins.
The fin itself will break long before the epoxy lets go inside the airframe.
For reference, here is what happened to one of my Lexan fins after I decided to get too cute and build a "proper" Shuttle model out of the Estes kit. That included side boosters that separate mid-flight, and the cute invisible fins. One awkward landing later (usual oscillation under chute), I am down to 1.5 fins:
shuttle.jpg

To add insult to injury, the stub is held in place by a quality epoxy fillet, making it that much harder to replace the fin!
 
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neil_w

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How thick are those fins? Mine are 3/32” and there is no way they are breaking unless I try to fly this thing at Mach 3. I should have gone with 1/16”, but it wasn’t available in stores and I didn’t feel like ordering at the time.

In any case, my main goals are 1) fill the gaps, for appearance sake, and 2) fill the gaps to support the fins from being able to wiggle and stress the root joint. I think I can achieve that with my medium CA... will find out soon enough.

I’m not particularly worried about these fins but they don’t feel finished while those gaps are staring back at me.
 

afadeev

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How thick are those fins? Mine are 3/32” and there is no way they are breaking unless I try to fly this thing at Mach 3. I should have gone with 1/16”, but it wasn’t available in stores and I didn’t feel like ordering at the time.
Just measured mine - 1/16”.
The damage came not from mach speeds, but from an awkward landing.
Likely from transverse bending pressure across the surface of the semi-flexible fin (airframe was rotating under chute upon landing).

In any case, my main goals are 1) fill the gaps, for appearance sake, and 2) fill the gaps to support the fins from being able to wiggle and stress the root joint. I think I can achieve that with my medium CA... will find out soon enough.
Give it a shot, and let us know (pics) how it turns out.
I've never had luck getting quality fin fillets out of medium CA. It just clumps up on me.

I did use multiple layers of thin CA a on LP kits few times in the past. Mostly to seal the fin-to-airframe (or fin-to-wrap) joints, while allowing thin CA to self-level.
 

neil_w

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FINISHED

I'll get this out of the way in advance: following account will, once again, describe and show mistakes I have made. I am not bothered by them in the least. I'm happy to be finished, and satisfied with the end result. Also, it is possible that you will feel stress as you recognize the mistakes as I describe them. Fear not, the end result is fine.

Let's get to it.

For the CA fillets, I was concerned about the nozzle making a mess on the fins as it rubbed across the base of the fin. So I had the clever idea of holding a piece of cardstock against the fin and removing it quickly after the glue is applied. In my experience, medium CA does not wick into it that quickly, so I thought I'd be safe. Well, as you can guess by now that was not the case. It *did* rather quickly start absorbing into the cardstock, and as I pulled it away I could feel it sticking a bit to the fin. And so a bit of mess was left on the fin near the root.
CA fillet 1.jpg

OK, so the medium CA *does* soak into the cardstock quickly. So my next great innovation was to wrap some metal foil tape around the cardstock, and try the next fin. This time the CA did *not* get absorbed, because hey metal foil. What happened instead was that it wicked up between the guard and the fin. I confess I was (and still am) really surprised by this. I guess on the first fin, the absorption by the cardstock stopped the wicking, but with the metal-covered paper there was nothing stopping it. So here's the second fin:
CA fillet 2.jpg

The good news is that the CA is totally clear, and so this particular defect is not very noticeable even though it extends reasonably far up the fin.

For the last fin: no more cleverness. I just applied the CA like a normal glue fillet, and learned (naturally) that I needn't have wasted my time with the previous stupidity. The CA stayed pretty well confined to the joint.

I've been calling these "fillets" but that's really not the right word. They're just filling the gaps around the base of the fin for appearance and to reduce fin wiggle. Here's the best picture I could manage of one of them:
CA gap fill.jpg

It served its purpose. I can now feel the fins flex outside the body, but there is no longer any movement within the fin slot. Looking at this picture reminds me that I had intended to put a bead of CA in the seam between the ferrule and the body, just to seal it up. Might still do that.

Here's a close-up of the finished fin can:
fin can.jpg

The most visible aspect is the edges, due to the overly thick fin stock. Can't do anything about that. Other than that, not too bad.

And here's the final beauty shot of the finished rocket:
final beauty shot.jpg

No removed background time because it would mess with the fin appearance. I think the fins will be pretty inconspicuous on the pad and in the air.

Final weight, without shock cord or parachute, measured at 5.25 oz. CG at 20". These numbers are somewhat worse than expected. My sim had weight at 4.7 oz and CG at 15". Weight is within normal error but CG is really disappointing far off. With motors added it still looks stable, but I'm going to check it with motor loaded in full flight-ready configuration to make sure, at least when/if I stick an E15 in it (it'll be totally fine on a D12). Possibly a touch of nose weight will be worthwhile here.

FIN
 

mbeels

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Awesome! It totally looks like you found some really tiny 1/8" PVC to display your totally normal pencil.

For the last fin: no more cleverness. I just applied the CA like a normal glue fillet, and learned (naturally) that I needn't have wasted my time with the previous stupidity. The CA stayed pretty well confined to the joint.
Well, some of the best progress is necessarily made by finding out all the ways that don't work. But yeah, that final result looks great.
 

jqavins

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Many times I've had to remind myself "No, those fins are not super tiny, because that's not a real pencil." The pencil even makes the PVC pipe stand look small, because it tricks the eye into using it as the scale reference.
 

neil_w

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Many times I've had to remind myself "No, those fins are not super tiny, because that's not a real pencil." The pencil even makes the PVC pipe stand look small, because it tricks the eye into using it as the scale reference.
Honestly, even up close and in person the whole silly thing really does look like a pencil. It's kind of funny.

Considering how long ago I had this idea, it's nice to see it come to fruition as originally envisioned!
 

BABAR

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Weight is within normal error but CG is really disappointing far off. With motors added it still looks stable, but I'm going to check it with motor loaded in full flight-ready configuration to make sure, at least when/if I stick an E15 in it (it'll be totally fine on a D12). Possibly a touch of nose weight will be worthwhile here.
Just put a little lead in the nose. Oh wait..........

That looks great. Somebody oughta make a kit like this. Oh wait.......



Sorry Neil, you teed those up for me too well to resist.

Looks great. Actually I am convinced that if you magnified a REAL pencil up to the size of your rocket it would have far more prominent imperfections than the minimal things you describe.

Nice concept, well documented build, great execution.

Hope you get a great flight WITHOUT any SkyWriting!
 

jhartman009

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Hobby Stop West in Toledo, OH was my place as a kid. Don't remember the kits we got there, but my dad helped his train collection there too.
Is Hobby Stop still open. I spent a lot of time their in the 70’s. They were in Point Place at that time.
 

SeanW78

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Is Hobby Stop still open. I spent a lot of time their in the 70’s. They were in Point Place at that time.
No. They closed years ago. Last I knew there was one on Monroe st. near Secor.
 

neil_w

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Final weight, without shock cord or parachute, measured at 5.25 oz. CG at 20". These numbers are somewhat worse than expected. My sim had weight at 4.7 oz and CG at 15". Weight is within normal error but CG is really disappointing far off. With motors added it still looks stable, but I'm going to check it with motor loaded in full flight-ready configuration to make sure, at least when/if I stick an E15 in it (it'll be totally fine on a D12). Possibly a touch of nose weight will be worthwhile here.
I just rechecked my sims and got totally different numbers. I don't know where CG at 15" came from. :dontknow:

After rechecking, things don't look too bad. I'm at about 1.7 calibers with an E15, about 2 calibers with a D12. That's probably OK. Could perhaps use a *touch* of nose weight, but not as bad as thought.

In the meantime I *did* apply some more medium CA to the ferrule/body joint to fill in the caps. Worked fine and pretty much invisible. Medium CA is ideal for that application.
 

jqavins

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Medium CA is ideal for that application.
That and what other applications? I'm just curious, because I keep the stuff around but never seem to use it. I use thick when I need a little working time (emphasize "little") and thin for wicking into places, but I never end up using the medium.
 

neil_w

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Well, it's good for gluing stuff (seriously). Also, when you need it to flow but also need it to fill gaps. You can also control where it goes, whereas thin has a dangerous mind of its own. I also use it to seal up and protect cuts.

Basically, medium is more likely to stay on the surface and build up a layer; thin will absorb into anything even slightly porous.

These days I do use the thin more than I used to. I don't own and never use thick (have owned in the past, didn't like it too much). SuperGold doesn't come in thick anyway, and that's what I use nowadays as much as possible.
 

jqavins

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I use thick for the first step of fin attachment if I can't use a jig for some reason. I place dots of it slightly in from each end of the root edge. It sits there. Then I place one root corner where it needs to be, and carefully bring the whole edge down. I get a couple of seconds to make sure it's aligned and normal (or off normal by the right amount) before it kicks. Once it's kicked, I wick some thin into the rest of the joint, then fillet. The same works for launch lugs that are not nestled against fins, and other stuff like that.
 

Blast it Tom!

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That is one fantastic looking rocket, as others have said it tricks the eye because pencils are supposed to be small! Beautiful job on the decals too, they really make it. Many happy flights to you!
 

BABAR

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You know, now that I think about it this is one of the few rockets that you really hope doesn’t live up to it’s name.
Although the Estes Doorknob comes close........
 
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