Starship Avalon: build thread

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The pixelated or faceted fins of your artwork may inspire a building technique. Use a larger diameter tube like an oatmeal can as a mold, cover with wax paper, and laminate smaller squares of overlapping thin balsa sheet to rough out the shape. Then sand the heck out of it. Then you might strengthen the balsa with cardstock, like papering fins.

Now I'm thinking that building the helixes out of triangular pieces of, say, 1/16" basswood could give the final product a very interesting faceted look. I am mainly concerned about strength; seems like the whole thing would be likely to crumple on the first landing. The extension of the helixes behind the rear pylons also seems like a big problem on landing. Papering the faceted surface seems impossible. (?)

The motor mount is also concerning. I'm thinking 1/8" basswood, but the trick would be anchoring it securely to the back of the rocket, and motor retention is also an open question.

I think if I can solve the structural issues then this thing could happen. The design's not nearly done yet, but it'll get there.
 
It looks to me as if you may, at the least, have enough drag to get away with it. There isn't much traditional fin area but I think the helix "fins" will get the job done.

Looking at the helix, I'm thinking that I would take a balsa strip, soak it in water and form it around a t tube of appropriate diameter until dry. I would then lay a layer of light glass on the outside to strengthen it. I am still.working on a plan to make them with a triangular cross section.
 
Looking at the helix, I'm thinking that I would take a balsa strip, soak it in water and form it around a t tube of appropriate diameter until dry.

I found an old popcorn tin that has almost the exact correct diameter (about 6.5") to act as a form for the helixes. Been reading up on how to bend balsa, seems like a lamination of 2 or 3 layers of 1/32" balsa is the way to go. I have never tried this, sounds like fun(-ish).

My one concern is a write-up I saw where they said that the wood will tend to spring back slightly afterwards; I would need it to hold the form shape exactly. That particular how-to wasn't talking about laminations, though; maybe the lamination would tend to hold the thing to shape better. I guess I should try a few practice pieces and see what happens, only requires a sheet of balsa to get started.

I am still.working on a plan to make them with a triangular cross section.

I'm not sure that's really necessary, although it would certainly look good. One straightforward way would be to glue some triangular pieces onto the helix to act as a frame, and then skin it with cardstock or 1/32" plywood. The hard part would be figuring out the correct shape to cut the skin pieces; that'd require more math or CAD expertise than I am in possession of, but maybe there's a way to cut them to shape after gluing... not sure.
 
Been reading up on how to bend balsa, seems like a lamination of 2 or 3 layers of 1/32" balsa is the way to go. I have never tried this, sounds like fun(-ish).

My one concern is a write-up I saw where they said that the wood will tend to spring back slightly afterwards; I would need it to hold the form shape exactly.

I have done this. And there was no springing back either. 1st, I nearly boiled the balsa where my bend would be. Just almost to a boiling point. After about 45 minutes, I placed the wood on the side of an aluminum cooking pot that had the curve I was looking for. The pot was preheated to a "too hot to handle" temp. I also had two halves of a really thick cardboard tube I cut (from the center of a roll of carpet) and sandwiched the wood on the side of said pot and clamped it slowly in place. One of the halves was atop of the wood, and the other half was inside the pot. Kept it clamped until everything had cooled. Basically for quite a few hours. I'll draw you a diagram if this doesn't create the proper image for you.
 
The key to getting it to hold shape is to let it dry completely in the form. Making a laminated strip of pre-bent pieces may help as well, just hold them in the form while the glue dries.
 
Bits of progress on the design:
avalon4.png

There are still (lots) more decaling details to work on, but it's starting to converge. I don't know yet if I'm satisfied with the front treatment, but it's not bad (?).

Right now my efforts are focused on figuring out whether I could actually build this thing.

For the helixes, I bought a sheet of overly-hard 1/16" balsa, and am going to try to create two-layer laminated pieces with it. That may be overkill, but they really seem like they'd be a likely candidate to break in any number of ways, so maybe a bit of overkill is not a bad idea. I went trolling around Home Depot today looking for a good 5.3" form to bend the helixes around, and found that 4" PVC couplers are awfully close at 5" in diameter. In the above pic I adjusted the diameter down to 5" and it looks fine, hardly able to tell the difference. I'll need to connect two of them together to achieve the desired lengh; a short piece of 4" pipe would be perfect, but I'm not gonna buy a 10 foot piece just to get 6". Will see if I can bum a piece of someone, else will improvise). My balsa bending experiments will commence soon. I have still not *totally* thrown away the idea of building them up from a bunch of small pieces and making them look pixelated like the sim image. But if I can get my stuff to bend properly I'll probably just do that.

I've also been staring at the open-air motor mount. It needs to be strong and also needs some decent motor retention strategy that will allow me to remove the motor without flexing the mount too much. I had a crazy thought of putting a retainer at the very back, and then making the whole darn assembly removable. But then, how would I attach it for flight? No idea yet. Must think hard about this. It looks cool (at least, without the motor in it), but if I can't make it solid and reliable then it's not worth it.

Finally, those rings are going to be a PITA. I'd probably need to cut them into three pieces and glue each piece in separately. That will not be enjoyable. I'm going to play around in OR and see if I can come up with a satisfactory design without them, but I suspect they'll stay because now I'm so used to them.
 
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I love the way you incorporate rings in your designs. My concepts aren't nearly as attractive hence, I rarely have any with rings. I think what you did to "swell" the nose section is a step in the right direction too. Some kind of enlargement there, was screaming to be incorporated. My take on the use of the word "overkill" doesn't really grab me in the same place it does you. If it were me designing this, I'd prolly 86 the pixel approach on the fin concept, and go with a bent triangle look. (if you will). Simply, starting at the top of the fin with a sort of point and gets wider at the bottom. Not that your idea doesn't have aesthetic appeal, but the drag factor is going to be seriously intense. You may fight to keep from snapping them no matter how you reinforce them. Damn thing gets a 10 for being out of the box, for sure.
 
I love the way you incorporate rings in your designs.

Thanks, I do seem to gravitate towards them although in this case I was following (or trying to, at least) the original images. I wish they weren't so darned difficult to work with when it comes time to paint.

I think what you did to "swell" the nose section is a step in the right direction too. Some kind of enlargement there, was screaming to be incorporated.

Yeah, that seems to be right out of the standard playbook when it comes to long starshippy designs. I'm trying to make it a bit different with the strakes instead of the trailing transition. More to be done there, but I'm happy with where it's going.

My take on the use of the word "overkill" doesn't really grab me in the same place it does you. If it were me designing this, I'd prolly 86 the pixel approach on the fin concept, and go with a bent triangle look. (if you will). Simply, starting at the top of the fin with a sort of point and gets wider at the bottom.

I don't think I quite get that, can you take another crack? You're right that the pixel approach is probably better to think about than actually try doing. But I'm getting used to looking at it in the pictures. :)

Not that your idea doesn't have aesthetic appeal, but the drag factor is going to be seriously intense. You may fight to keep from snapping them no matter how you reinforce them. Damn thing gets a 10 for being out of the box, for sure.

I'm kind of surprised any sort of workable-ish design emerged from those original images. OTOH I don't know if I'd actually have the guts to fly it, might need to self-medicate a bit beforehand. I think I would take a *lot* of pictures of this one before the first flight, if you know what I mean... :eyepop:
 
I'm not much help on the design end, but for implementation I would use Blue Tube for the helix fin things. Even in thin strips, it holds it shape and is surprisingly strong.
 
Here's a haphazard rendition of what I'm suggesting. Much like the shape of the bend you are playing with, this is the same, except you're taking a long skinny triangle and bending it into shape.

Avalon Fin.jpg
 
I still think cutting the Twisties out of an existing tube may be a less headachy approach.

It occurred to me looking at the bent triangle that the Kraken approach should work: two appropriately separated circumferential lines marked, said lines divided into segments, the segments then being connected in a spirally angly way.

+1 on the trailing strakes, also. Some seriously neat stuff going on here.
 
I still think cutting the Twisties out of an existing tube may be a less headachy approach.

Which takes us back to post # 7. I used a 4" HPR tube for my bent / curved fins that were cut straight from the tube for the Gyro Dragon. I suppose Blue Tube would suffice as well. I've never used Blue Tube, so I know little about it. At least they wouldn't have to be bent because the curve is already there. I may have to try my hand at a gnat scale version of this fin can just to see what it looks like. Prolly stiffen up some scrap BT 70 and go at it.
 
Which takes us back to post # 7. I used a 4" HPR tube for my bent / curved fins that were cut straight from the tube for the Gyro Dragon. I suppose Blue Tube would suffice as well. I've never used Blue Tube, so I know little about it. At least they wouldn't have to be bent because the curve is already there. I may have to try my hand at a gnat scale version of this fin can just to see what it looks like. Prolly stiffen up some scrap BT 70 and go at it.

Looking forward to someone w/ a lot more skill than me giving it a go, my curiosity doesn't seem to want to give it a rest.
 
Cut tubing would be great if I had the appropriate stuff. 5.5" bluetube is crazy expensive and sold in 4 foot lengths (I only need about 8"). I found that large oatmeal tubes are about 5" which would be fine, but that stuff is so flimsy I really don't trust that it would hold up (even with application of CA). So, at least at this size, I think it's worth at least trying to bend the balsa. It might be a pain but in theory it should work, and a 2-ply laminate should be pretty strong (and I'll paper the outside as well. :))

Gary's remark about making a gnat-scale version really has me pondering if I should downscale this whole thing to 18mm or even 13mm, which would make the appropriate tube size either 4" or 2.6", and those would be much easier to obtain. This could be a cute mini-engine model, although I really do prefer to build larger. Maybe I'll try putting together a downscale OR model, and see how it looks.

Gary Byrum said:
Here's a haphazard rendition of what I'm suggesting. Much like the shape of the bend you are playing with, this is the same, except you're taking a long skinny triangle and bending it into shape.

That could look really cool, would give it a bit more of a starfightery look I think.
 
What about 5.5" blue tube coupler? That's $19 at BMS for a foot of it.
 
Neil,

I pittled around in the tube storage this evening and found some old mailing tubes. 3" and fairly thick. I did a little CA inside and cut some pieces out for the said fin can. I have 3 of the 6 braces gluing to a BT 55 as we speak, and tomorrow I'll see if I can get some more done on it. Glue is taking forever to dry this weekend what with all the moisture that friggin hurleycane blew everywhere. It's a trial and error assembly, but I do have a boiler plate in the making. Pretty sure the mailing tube is going to work quite well. And they're cheep! You can change the degree of the fin template on the tube to get the kind of bend you want. I'm using about 60* angle and it gave me a fairly nice curve.
 
Here's an 18mm version, with 4" diameter helix and BT70 rings (BT20 and BT50s for the body):
avalon-18.png

Proportions seem to hold up well. Length is just under 23", weight is 1 oz before a few miscellaneous things, so probably 1.5 oz ready to fly. That could do OK on C engines; it'll be draggy but at least it'd be light. I dunno, maybe that's big enough to be worth it for me. I wouldn't relish stuffing the parachute into a BT-20, though...

Gary, I look forward to seeing your mockup!
 
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What about 5.5" blue tube coupler? That's $19 at BMS for a foot of it.

That's still more than I'd want to pay for a single part like that. For the downscale, though, i could use 98mm coupler stock which is $11, getting closer to reasonable. For roughly 4" stock, though, I think I could probably find something else (like mailing tube or whatnot). Or, possibly, a single layer of my rock-hard 1/16" balsa, papered over. There are some possibilities here.
 
I seem to be leaning towards going with the 18mm version of this. Here's an updated version, with some important changes in proportion:
avalon18_45.png
I won't say what the changes are, but if anyone notices anything that looks out of balance, please let me know. I'm going bleary from looking at it, hard to trust my own instincts at this point.
 
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I wouldn't relish stuffing the parachute into a BT-20, though...

Gary, I look forward to seeing your mockup!

Neil, the helix is drying to the lower braces as we speak. That, btw, is no easy application. The 1st set of braces had to be tweaked by sanding the ends to the angle I wanted them. They were off badly. I used some sewing pins to hold the helix on until partially set and adjusted accordingly. I'll let those dry for 45 min or so. The next set of braces go in next and they too will have to be taken in and tweaked also. This is one that I can't get right in Autocad, so I'm having to adjust, adjust & adjust. Once I get the forward braces in place, I'll snap a pic for you. And FWIW, I'm using a BT55 for the fin can and a BT 50 for the forward airframe. I don't do chutes in 20's either. The taper has been ready for a couple of days. Found a spare scrap block of 2 x 2 that I'll turn the nose cone with. I've never made a 55 nose cone to fit a BT 50 before. This ought to be interesting.
 
Okie Dokie! For starters, I'm not sure I like building this rocket. Maybe the parts are too small for me to handle properly, or I'm not in the right building mood, or maybe it's the meds. A little oral surgery invites the need for a percocet now and then. Maybe that's it.

Anyhoo, the side view is obvious, but the 2nd pic is an aft view (such as it is) and you can see how the braces have to be offset a bit. This is a PIA to do unless you know how to math something like this out. And I don't. That's why I had to cut, tweak and sand, cut,tweak & sand. Then it had to be glued. It made me break out the CA for crying out loud! :rant:

100_1603.jpg 100_1607.jpg
 
Haha. May not be what you envisioned, but I still think it looks cool.
 
Well, it is a boiler plate so it's not supposed to be sharp looking. I'm sure with all the right stuff in the right places....... it does have potential though. I suppose, if it were my project, I could go the distance with it and make something happen with it, but it's not. I'm just interested in seeing if it'll go together and give it a test flight. This will be Neil's PIA. Can't wait to see if he has the nads for it....LMAO!
 
Anyhoo, the side view is obvious, but the 2nd pic is an aft view (such as it is) and you can see how the braces have to be offset a bit. This is a PIA to do unless you know how to math something like this out. And I don't. That's why I had to cut, tweak and sand, cut,tweak & sand. Then it had to be glued. It made me break out the CA for crying out loud! :rant:

Sorry I never posted a rear view. Based on my interpretation of the original images, the front and rear fins are actually offset by 60 degrees:
avalon_rear_or.png

Whether or not that's how the original image is, I like it like that so that's what I'll be doing. I have a pretty good plan in mind on how to measure and cut these pieces (whether from a tube or bent balsa); it doesn't require much (any?) math but it will require care.


For what it's worth, even in rough form I think that looks really good and it motivates me to keep going. I think there are a lot of different cool designs that could be made with variations of those helical fins.

Well, it is a boiler plate so it's not supposed to be sharp looking. I'm sure with all the right stuff in the right places....... it does have potential though. I suppose, if it were my project, I could go the distance with it and make something happen with it, but it's not. I'm just interested in seeing if it'll go together and give it a test flight. This will be Neil's PIA. Can't wait to see if he has the nads for it....LMAO!

oh-no-you-didnt-27.jpg


I *will* be proceeding with this design, but probably at a leisurely pace because many aspects will require a good bit of thinking to get it all correct, and I'm still struggling with a few design decisions. So I'll probably work on this in the background while I so other, more straightforward stuff in the foreground. There will of course be a build thread. 😉
 
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I didn't catch that fin alignment until after I assembled the can. I saw in the movie trailer where the aft view was like the drawing you posted. Wish I had known that earlier. My assembly is haphazard at best. I'll prolly finish it up like it is and see how it goes. I don't plan to make a serious model of it, but you'll get my report on a test flight as soon as I get it in the air.
 
Balsa bending experiment #1. Very hard 1/16 balsa, soaked in hot water for an hour, bound to a 4" pvc coupler. This is purely experimental, the piece in question is not intended for rocket use (I didn't measure or anything)
ImageUploadedByRocketry Forum1476464720.473149.jpg

After soaking, the wood seemed to conform reasonably well. I'll let it dry over the weekend, and we'll see if it holds form.
 
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