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

Discussion in 'Scratch Built' started by neil_w, Oct 31, 2019.

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  1. Oct 31, 2019 #1

    neil_w

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    Note: I'm going to break my own self-imposed rule and get this build thread started. The rule being, "don't start a build thread until are sure you can make steady progress and keep the thread moving". This will be a leisurely build thread with some significant gaps in the action, and the build is likely to stretch out for a while. Consider yourselves warned. I also still have some issues to resolve, look forward to discussin those here.

    So: this is my pencil rocket build. No fancy render because OR cannot capture what I'm building exactly, and I'm too lazy to build a CAD model of the whole thing. Those following my half-baked design thread will know all about it. The simple objective is to create as precise a scale replica of a pencil as reasonably possible. Originally inspired by the Estes #2 Skywriter.

    Should this be in the Scale forum? Ha ha, I kid.

    The rocket is built around a BT55 core tube, 24mm mount, and will be *roughly* 33" long. There are still some details to nail down, and body tube construction is still some weeks away.

    Actual build with pictures will commence in my next post.

    PS: Actual name I'm going with is Skywriter Deluxe.
     
  2. Oct 31, 2019 #2

    mbeels

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    So if a 1:4 scale is 25%, and your rocket is an upscale pencil, should we call it a 5.3:1 upscale?

    Looking forward to the details in this one.
     
  3. Oct 31, 2019 #3

    neil_w

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    Right you are! Fixed. :)
     
  4. Oct 31, 2019 #4

    BABAR

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    Is NewWay going to come out with a Carpenter version of this?
     
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  5. Oct 31, 2019 #5

    mbeels

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    I had a thought while sitting here at my desk, holding a #2 pencil. The writing is stamped into the wood. I wonder if it would work to simulate an embossed effect by stamping into the balsa sheet, and inlaying the decals. It would add another level of surface texture detail.
     
  6. Oct 31, 2019 #6

    neil_w

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    I do not believe that is always (or even normally) the case. All the pencils I've looked at (recently, anyway) have painted-on lettering, no embossing. In any case my plan is to do plain ol' decals on the surface.
     
  7. Oct 31, 2019 #7

    cwbullet

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    If you design it, I can print a nose cone and fin can.
     
  8. Oct 31, 2019 #8

    neil_w

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    Appreciate the offer, but I’ve got it all planned. :)
     
  9. Nov 1, 2019 #9

    neil_w

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    This build will be divided into three parts, proceeding from right to left:
    upload_2019-10-31_21-43-14.png

    Note the mix of pencil and rocket terminology. Oh well!

    So we will be starting with the ferrule assembly, which consists of the ferrule, the eraser, and the motor mount.
     
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  10. Nov 1, 2019 #10

    BABAR

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    I take it teeth marks are optional?
     
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  11. Nov 1, 2019 #11

    neil_w

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    I did consider teeth marks. Could just rub some bacon grease on it and hand it to a dog when I'm finished. :)

    Also thought about modeling a "used" eraser, and making the whole thing shorter and stubbier to reflect a half-used pencil. All would be great but I decided to go for the pristine, just-sharpened-for-the-first-time look.
     
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  12. Nov 1, 2019 #12

    neil_w

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    FERRULE ASSEMBLY, PART 1

    The ferrule assembly starts as a 4" piece of BT55. In a previous "practice run", I determined that I needed a slightly larger diameter, but a layer of 1/32" balsa was too thick. So I wrapped two layers of 110lb cardstock around it, which was roughly the correct amount:
    Rear tube construction-1.jpg

    That is now a very thick-walled tube, quite sturdy.

    Next comes the first layer of 1/32" balsa, which covers the entire tube. I found during my IRIS-T build that 1/32" balsa will wrap around a BT55 with very little fuss. Unfortunately, the sheets aren't wide enough to go all the way around, so I need to piece it together. Here's after the first piece was applied:
    Rear tube construction-2.jpg

    Next step is to cut the next piece to fit. Here's a dry fit, which looks about right:
    Rear tube construction-3.jpg

    Not that I have a piece of coupler inside the tube; I kept it there throughout construction. With all the squeezing and wrapping and shrinking glue, I really needed to ensure that the tube stays round.

    After one layer of balsa, the tube size is correct for the eraser. The ferrule needs another layer, so on go two more pieces to cover the top 2 3/4" of the tube. Here are a few pics showing the actual process of attaching the final piece.

    First, I apply some Windex to one side of the balsa sheet to soften it up. This is the side that will be the *outside*, since the expansion caused by the liquid tends to make the wood bend away from it.
    Rear tube construction-4.jpg

    Next I coat the receiving area on the tube with a very thin layer of TBII.
    Rear tube construction-5.jpg

    Then, apply and squeeze:
    Rear tube construction-6.jpg

    I hold this position until the glue is set enough that it will *almost* hold. Then I wrap the whole tube as tightly as possible with a piece of cardstock to dry completely.
    Rear tube construction-7.jpg

    This piece is now ready for sculpting.
     
  13. Nov 1, 2019 #13

    mbeels

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    Is it the ammonia here that helps the most? I've heard of diluted white vinegar being used for bending wood, and I've also used just plain H2O steam. But windex is a new idea to me. I'll have to try it next time, it even come in a convenient spray bottle.
     
  14. Nov 1, 2019 #14

    neil_w

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    Yeah, the (small amount of) ammonia is the thing, in theory. I read this suggestion somewhere or other on the web. Although to be fair, these very flexible 1/32" balsa sheets, being bent with the grain, probably didn't need any help beyond just being wet.

    I have not tried to quantify how much better Windex works than plain water. I think when I was bending the balsa for Starship Avalon that I found that the Windex does help at least a little. More serious bending (thicker wood or tighter radii) would no doubt call for higher concentrations of ammonia.

    I will say this: bending balsa is a lot of fun, and it allows for creation of some unique shapes.
     
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  15. Nov 1, 2019 #15

    jqavins

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    Aw, gee. Why not keep the whole name? After all, it's short compared to this actual song title: "Regretting what I said to you when you called me at 11:00 on Friday morning to tell me that 1:00 Friday afternoon you were gonna leave your office, go downstairs, hail a cab, to go out to the airport, to catch a plane, to go skiing in the Alps for two weeks. Not that I wanted to go with you; I wasn't able to leave town, I'm not a very good skier, I couldn't expect you to pay my way, but after going out with you for three years, I don't like surprises. (A Musical Apology)"

    Or bending across the grain. Highly concentrated ammonia will let you turn a dowel into a pretzel. But then steam alone is what old time ship builders used to bend giant beams (6" by 8" or more?) into the curved ribs needed to make the hulls. And violin makers shape thin strips of I don't know what wood into the tight scrolls of the sides using just heat.
     
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  16. Nov 1, 2019 #16

    Scott_650

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    This is an absolute and utter off the cuff guess but I’d say the ammonia acts to decrease the surface tension of the water, allowing the wood fibers to slide across one another more freely. In other words, the ammonia acts as a wetting agent - making the water “wetter” so it can be a better “lubricant” for the fibers. You are most likely correct that 1/32” balsa sheets don’t need anything other than plain water to increase flexibility but I’d say the added ammonia surely can’t hurt the process.
     
  17. Nov 3, 2019 #17

    Mugs914

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    Molded balsa shells are a pretty common practice in the world of control line stunt models. It is surprising just how much you can get a sheet of balsa to do using the proper techniques.

    I usually go with straight water for stuff that is single curvature like a cylinder or sheet glider wing. Don't be afraid to really soak it, just be sure to let it set for a while. I try to give it 24 hours, but usually succumb to curiosity before that.

    Windex works great for thicker wood (1/8" or more) or if you are looking for more bend along the grain. Again, really drench it.

    If you use straight ammonia two things will happen:

    First, the smell will clear your family out of the house completely, the neighbors will call the fire brigade, cops, EMT and the space-suit guys to come clean up whatever nefarious chemical goings-on you have been up to.

    Second, that sheet of balsa you just soaked will turn into a big, rubbery plank that is more than willing to form around a three dimensional shape. It would be fairly easy to make a 2" or bigger nosecone out of 1/8" balsa using two molded halves. Smaller stuff with thinner wood is even easier.

    Of course a mold is needed that takes into account the wood thickness. The (quite stinky) balsa is gently formed around the mold and wrapped tightly with ace bandage or similar stretchy stuff that will allow it to breathe a bit. I actually do give this kind of thing a good 24 hours or more to dry.

    Entire airplane fuselage halves have been done with this method for everything from small free-flight types using 1/32" wood to 60" span stunt models using 1/8" or more. Long, swoopy F-104 looking intakes would be a natural for this process.

    Sorry to go on so long. I don't know if this is all common knowledge here or not. I know it is fun to do and opens up a bunch of possibilities!
     
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  18. Nov 3, 2019 #18

    neil_w

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    FERRULE ASSEMBLY, PART 2

    Next up is to shape the ferrule. There is some variety in the shape of these in real live; I chose a shape that seemed representative.

    Disclaimer: I realize it might have been a good idea to use some sort of lathe setup for this. However, having done a "practice ferrule", I was pretty confident about what I needed to do, and how.

    First, I marked the locations for 6 grooves:
    Ferrule-01.jpg

    I narrowed down the center portion a bit (I will not however be doing the ring of fine grooves that you see in *some* pencils; was not confident I could execute that successfully). That was just a bunch of slow, patient sanding. In general, accuracy was the objective here, and that meant taking things slowly and deliberately.

    Then I cut very small grooves around the marks with the sharp corner of a needle file. These will be "guide grooves" while I enlarge the grooves with rounded files that otherwise would be very hard to control precisely.
    Ferrule-02.jpg

    Then, using progressively larger rounded needle files, I expanded each groove until they were precisely... well, until they looked good. The final step was to roll around the grooves with the shaft of a screwdriver. I think my 1/32" balsa sheet was on the hard and dense side; the screwdriver treatment didn't seem to have as much effect as on the practice run. In any case, the finished grooves looked pretty smooth and straight (there is some distortion from the close-up camera shot):
    Ferrule-03.jpg

    After completing the first three, I did the others, and my ferrule sculpting was complete:
    Ferrule-04.jpg

    Pretty good so far. Working on this assembly makes me nervous because it is a lot of work and one bonehead mistake could kill it. No screwups so far!
     

    Attached Files:

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  19. Nov 3, 2019 #19

    mbeels

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    Interesting! I always like learning new techniques. Did/do you fly C/L? Your post gives me some ideas....

    That must have been a lot of sanding, especially if you're working with dense balsa. But the results look worth it, I keep referencing your profile logo for scale reference, and you've got it nailed.
     
  20. Nov 4, 2019 #20

    Bruiser

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    Looking good!

    One mistake and it's a goner? Come on Mr. Drama, did you run out of CWF :)

    -Bob
     
  21. Nov 4, 2019 #21

    neil_w

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    True, this part is recoverable. It's the metal skinning that is really the riskiest; that comes later.

    The nose cone is likely to be the worst in this regard. I am quite nervous about it, but it's still a long way away.
     
  22. Nov 4, 2019 #22

    BEC

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  23. Nov 4, 2019 #23

    Mugs914

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    Awesome, ideas are good! just be sure to share...

    Do you think anyone would be interested in a tutorial type thread over in the techniques section? Might take me a little while but I could probably put something together.

    Yeah, I fly C/L, though it has been almost two years. We moved a while ago and I have yet to get down to meet the local C/L crowd (about an hour away). I mostly fly stunt and used to compete, but mostly just for fun now.

    This is one of my original designs. It is called a Galaxie (I used to name my originals after old Ford cars, Fairlane, Starliner, etc.). The wing tips are done with the molded balsa technique I described above. The bits that aren't open tissue are 1/8" balsa formed over a carved mold.

    IMG_20151231_143932.jpg
    IMG_20151231_143825.jpg

    Sorry Neil, I didn't mean to hijack your thread with airplane pics! I'll move further discussion over to techniques!:oops:
     
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  24. Nov 4, 2019 #24

    neil_w

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    No problem, that's cool stuff. I'd sure be interested in the tutorial, and I'll bet others would be too.
     
  25. Nov 4, 2019 #25

    mbeels

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    Oh man, that is gorgeous! I'd love to see your tutorial.
     
  26. Nov 4, 2019 #26

    jqavins

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    I was wondering if there'd be anyone else.

    Hmm, let me see. Multiple choice:
    1) Yes
    B) Hell yes
    III) F Yeah!​
     
  27. Nov 5, 2019 #27

    neil_w

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    FERRULE ASSEMBLY, PART 3

    The ferrule assembly will eventually need to be connected to the body. After some headscratching, I decided to use a combination of a stuffer tube and a piece of coupler to ensure perfect alignment. Assembly sequence also took more than a bit of thought.

    The problem with the coupler is that there will be TTW fins right on top of it, so I cut some over-wide slots in it, wide enough so that even with imperfect positioning, the fins should fit through.
    Ferrule-05.jpg
    This piece was then glued into the ferrule assembly:
    Ferrule-06.jpg
    Next, the motor mount/stuffer tube was assembled. Pretty straightforward, except the frontmost centering ring was not installed yet, or it wouldn't get past the coupler. Also, I sanded down the glassine on the part of the tube where the fins would be attached (much) later.
    Ferrule-07.jpg
    This was then glued in, with the aft centering ring just *slightly* recessed to allow for a fillet, and even more important, a layer of CWF to the whole thing could be smoothly joined to the "eraser", which was also CWFed:
    Ferrule-08.jpg
    Here is the almost finished assembly:
    Ferrule-09.jpg
    The last step, not shown, is attachment of the frontmost centering ring at the left edge of the above picture. The Kevlar will wrap around there, but I won't add the Kevlar until the last minute.
     

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  28. Nov 5, 2019 #28

    Nytrunner

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    Is that a 24mm mount?

    Recalling your quandary on nose weight, I thought of a technique one of my club members uses. He drills a half inch hole in the base of the cone and inserts an oak dowel or other heavier wood as a dual purpose eyescrew anchor and weight towards the nose
     
  29. Nov 5, 2019 #29

    neil_w

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    Yes, 24mm mount. It'll be heavy enough to need it for sure.

    I'm not yet sure if this thing is gonna need nose weight. I have what I think is a reasonably accurate OR simulation, and stability seems to be coming out OK. Shouldn't need to much in any case.

    The nose construction is going to be a little weird... will likely call for its own solution w/regard to adding weight.
     
  30. Nov 5, 2019 #30

    Nytrunner

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    Oop! I thought we were going with the giant pencil sharpener route
     

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