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  #21  
Old 02-16-2011, 01:55 PM
BPRescue BPRescue is offline
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Quote:
Originally Posted by jharding58
The decorative nature of the wrap renders the risk of damage quite low. The airframe would usually need to be delaminated before the wrap is at risk.


I couldn’t disagree more… Just this last weekend, I had a number of rockets on a stand on a bench in my shop. I also had my son’s RC plane in there. He wanted to fly his plane, so I charged the battery, then let him put it in (I’m about getting tools in their hands early). With my back turned, he installed the battery, then powered all on and proceeded to give full thrust. The prop hit my rocket hard and at full thrust. Where I believe it would have broken the balsa fin, it took a couple nicks out of the wrapped fin. This was good in the regard that I wanted to see if the label would delaminate or be difficult to repair… My point, you never know where it’s coming from; at least in my household…

Of course, to your point; it did hit the fin first, so I lose at just about every scenario here…

As far as PVA in form of white and yellow glue I did have two failures that had to be from heat in this regard. A good thing about PVA glues (including white/yellow)is you can introduce heat as to provide a little extra working time; and it can really increase the bond strength for all PVA’s. The bad thing is that heat can also cause failure of cured glue, and or too much working of heat and glue can weaken the joint as well. To your point, it seems you had no experience in this occurring in “normal” flight operation; so the only time it may happen is similar to my instance where my chute failed to deploy in two different rockets. Completely my fault, I was playing around with putting two paratroopers inside, which ultimately bound in the tube causing the issue. The gasses could not escape, so my engine tube received much more heat than normal. It did impact my engine tube to center ring, and respectively the center ring to main body. Both failures occurred at the glue joint and the failure was quite clean. In that regard it is nice to know wrapping is a viable possibility.

Quote:
Originally Posted by jharding58
There are some wraps that are created from pre-printed label stock, or simply plain label stock. Both of the Pershing models which I produce are coated with a single layer of self-adhesive label to eliminate the spiral and better represent a moulded skin.


Have you provided a full body wrap? Along those lines, does anyone have pics of wraps that they have done. I have thought about attempting to print the designs on the paper, then laminating the fins to finally spray a clear coat over it. With what you guys are saying, this just may be plausible, so I may have to try it; especially since I have a parted out Big Bertha and Blue Ninja…

Great detail in your post…
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  #22  
Old 02-16-2011, 02:34 PM
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jharding58 jharding58 is offline
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Dr. Zooch kits use pre-printed wraps aplenty. They are also used as tructural elements. In the case of the 1-B the fuel tanks are rollled paper tubes. Mine are more intended to provide uniformity in the finish. I have no doubt that in some form a paper wrap will deliaminate from the substrate, sitting in a car in direct sunlight for six hours will no doubt have some impact on the adhesion. Just never had the direct experience. If anything the delamination issue would seemingly be reduce by using a perimeter attachment - there is less gluing surface to have issue with. Of course, if the vertical seam goes...

You know, in looking at the photos again I always hated how the LES tower looked. I am having a 1/100th PE set made up and was wondering what scale Zooch comes out to (Ant Scale is difficult to describe to an etcher).
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  #23  
Old 02-16-2011, 05:07 PM
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luke strawwalker luke strawwalker is offline
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Quote:
Originally Posted by BPRescue
I’m confused; which is not too odd… Are you guys talking about wrapping around the tube/substrate of a rocket you will be launching? That could make a huge difference in application I would suspect. In that regard, I am familiar with PVA and it is one of the best methods in attaching veneers. Do you heat it for the applications you speak of? If this were applied to the edge while using paper, would you not be able to see the transition between glued and unglued surface? Additionally, in finishing, I would think the paper could wrinkle or at a minimum show some lack of uniformity? And, if the model flies, if there is damage to the unglued area, you have a more difficult repair; potentially really bad since there is nothing to support the paper? In that regard, more damage than what would have occurred to an area that was secured, and more difficult to repair cosmetically since the stress of the accident could have deformed the paper?


That's the purpose of ONLY putting the glue around the edges, in a VERY THIN layer about a half-inch wide or so.

Dr. Zooch uses printed cardstock on many of his kits for the detailing-- fine details like lettering, roll patterns, some surface details that would be too small to do at that scale with other techniques, etc... The pre-printed cardstock detail skin is cut from the printed cardstock sheet with a hobby knife, and plain white glue is applied around the edges all the way around in a very thin layer. One corner is carefully aligned with the top of the tube and a reference line drawn the length of the tube square to the tube ends, and the edge carefully aligned and pressed down, securing the edge in place. Then the remainder of the wrap is carefully rolled onto the tube (or the tube rolled onto the wrap, is probably a more correct way to describe it) making sure the wrap stays even with the end of the tube and square to the tube until it's wrapped all the way round, and the edge aligns correctly with the starting edge which was glued against the reference line on the tube. If the wrap was cut correctly and neatly, and rolled on properly, it will align perfectly and leave a single hair-width seperation line (if that) where the two edges of the wrap abut each other...

Now, like you, first time I read that, I thought to myself, "what's gonna hold the paper to the tube in the middle of the wrap?? Seems a weak way to do it, because the wrap isn't bonded to the tube except at the edges." Yet Dr. Zooch warns in his instructions, if you apply the glue, even very thinly, using a credit card as a 'squeegee' to try to eliminate as much glue as possible and get it as even as possible, it's going to come out too thick, and the ends of the wrap will have a gap between them... additionally, air gets trapped between the glue-coated wrap and tube, and forms "blisters" under the wrap, and no matter how thin you try to get a sheet-wide layer of glue, when you work the paper down tight to the tube, you WILL work the glue into thicker "puddles" under the paper which will form wrinkles or distort the paper. How do I know?? Because I tried using the 'coat the whole sheet' method on a paper-towel tube Big Bertha knockoff night-flight rocket that I built a few years ago... even though I carefully squeegeed the glue to as thin a layer as I could get it, and carefully rolled the paper onto the tube, it still wrinkled and bubbled and looked like crap.

I've got Zooch models I built at the same time using his methods that look terrific... it's amazing how strong paper can be! They still look nice and stand up to anything the regular body tube can stand up to! Odds are, if you have an impact or ding severe enough to damage the wrap, it's going to severely ding your underlying tube as well, and will have to be repaired, and it wouldn't matter whether the wrap had been 100% surface bonded to the underlying tube or just perimeter glued as Dr. Zooch instructs...

As for heat, well, I've read about guys making their own tubes, brushing very thin layers of white glue on paper strips, letting them dry, and then rolling the strips onto mandrels in an alternating spiral pattern to create home-made spiral-wound body tubes, then heating them with an old clothes iron to 're-melt' the dried white glue and form a permanent bond. I suppose the same method would work as well for gluing on a wrap, but it would DEFINITELY be overkill and what the effects of the heat on the printed detail would be, I'd hate to think...

Here's a pic of a Dr. Zooch wrap, on the Agena of the Atlas-Agena I built last fall... And the full-body wrap of the Freedom 7 Mercury Redstone I built last summer... The SRB's of the Zooch Lifting Body stack also are paper wraps, and the Saturn V uses a series of paper wraps for the corrugations over the main body tubes, as seen in the pic, with wooden detail parts glued over/onto them...

Later! OL JR
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Last edited by luke strawwalker : 02-16-2011 at 05:27 PM.
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  #24  
Old 02-16-2011, 05:25 PM
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Quote:
Originally Posted by jharding58
Dr. Zooch kits use pre-printed wraps aplenty. They are also used as tructural elements. In the case of the 1-B the fuel tanks are rollled paper tubes. Mine are more intended to provide uniformity in the finish. I have no doubt that in some form a paper wrap will deliaminate from the substrate, sitting in a car in direct sunlight for six hours will no doubt have some impact on the adhesion. Just never had the direct experience. If anything the delamination issue would seemingly be reduce by using a perimeter attachment - there is less gluing surface to have issue with. Of course, if the vertical seam goes...

You know, in looking at the photos again I always hated how the LES tower looked. I am having a 1/100th PE set made up and was wondering what scale Zooch comes out to (Ant Scale is difficult to describe to an etcher).


Dr. Zooch doesn't give the precise scale... his rockets are "Ant Scale" which means semi-scale. He's gotten flack from some folks who are 'scale nuts' because his stuff isn't PRECISELY to scale... but then, a lot of things aren't... he's not selling Internats-competition quality scale birds at $25 a pop, ya know... but some folks get riled up about things if they're not a "PERFECT" scale... (anal retentive types mostly... )

At any rate, you can easily figure the scale of the Saturn IB... The S-IVB stage was 260 inches in diameter on the real vehicle. IIRC Dr. Zooch uses a BT-60 for the S-IVB stage on the Saturn IB, which is 1.637 outside diameter. Dividing 260 inches by 1.637 gives us an approximate scale of 158.83, or roughly 1/159 scale.

That's why I want to build a BT-80 based Saturn V, to go alongside my Zooch Saturn IB's... the S-IC first stage of Saturn V was 396 inches in diameter, and a BT-80 is 2.6 inches in diameter. I already know that a BT-60 used for the S-IVB third stage on a Saturn V will be perfectly in scale with a BT-60 S-IVB on a Saturn IB (obviously) so all I need is a tube the same scale at the larger diameter. If we divide 396 by 2.6, we get a scale of 152.31, or roughly 1/152 scale... If we reverse the numbers, using the scale of the BT-60 S-IVB, we find that the first stage SHOULD be 2.49 inches in diameter, which means a BT-80 is about 0.110 too big. That's not much for a semi-scaler, so while using a BT-80 first stage on a Saturn V with a BT-60 S-IVB probably wouldn't win any contests, for a sport-flying semi-scale bird it would be virtually unnoticeable. It's only about 1/10 of an inch off the correct size, and there are ways of fixing that...

Anyway, hope this helps! OL JR
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