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Best Method of Dome shaping
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Author:  airportkid [ Tue Jun 05, 2007 2:13 am ]
Post subject:  Best Method of Dome shaping

I haven't experimented extensively in this area yet, but doing some doodling it occurred to me there are two ways to design a dome: the flower method, or the icicle method. The icicle method is what I see most often used in published models - the dome segments are joined at the base (so the flat pattern resembles a clutch of icicles), and when glued up the dome will always come to a point. This is OK for prop spinners, but for fuselage noses such a pointed dome is usually too sharp (to say nothing of turrets and observation blisters).

The flower method joins the segments at the apex, with the segments radiating out from the center of the flat pattern like the petals of a flower. Domes glued up from such a pattern have flattened apexs and look much more like domes.

Anyone out there studied and experimented enough to make recommendations about which approach is best suited to particular dome shapes beyond my preliminary ruminations here? I always have trouble gluing up icicle patterns neatly - the convergence of many tiny narrow points is difficult to control without misalignment or getting glue all over the place - the flower seems like it'd be easier to glue up neatly.

Mark Baird

Author:  Rob [ Tue Jun 05, 2007 6:20 am ]
Post subject: 

Joining all the segments at the apex ususally results in a bit of a flat spot at the end---not ususally a desirable thing. Whether the segments are joined at base or apex--results in the same shapes being attached together to form the desired profile. the difference between a pointy end or a rounded one are determined by the shape of the 'petals' not by their orientation. I have used the same basic set of segments, altering only thier aspect ratios to do everything from some really pointy drop tanks, to a bluntly rounded nose. The most important thing when designing these pieces is to draw enough segments to keep a nicely rounded cross section, while keeping te number low enough to allow those 'petals' to retain some rigidity when gluing them together.

When I build such things, I usually first take bit of paper toweling or tissue, add some white glue and mold the desired end as closely as I can. When this bit sets up, Iinsert it into the glued up petals t;o help give it it's best shape.

segments are an imperfect solution to compound cuves in models, but multiple tiny rings can get awfully fiddly and tend to look downright messy in the hand of the ordinary builder. The more segmented parts you glue up the better your skill becomes, and thebettter they look.

Author:  airforce [ Thu Jun 07, 2007 7:41 am ]
Post subject: 

I've found that, with the "icicle method," the way to get a more rounded as opposed to pointed dome is to just overlap the tips a bit. On the C-47, this results in a nicely rounded dome. Conversely, on the F-4, I pull the "icicles" to a point that very closely resembles the Phantom's phamous schnoz.

Author:  nikischutt [ Fri Jun 08, 2007 9:40 am ]
Post subject: 

Superglue works nicely for gluing the very tips together, just enough to get the basic shape right, after that normal white glue to do the rest. I personally hate the petals, they are just so d**n finicky to get right.

Niki

Author:  Rob [ Fri Jun 08, 2007 12:56 pm ]
Post subject: 

I don't think anyone really likes the petal method of forming compound curved cone....but I don't see any other method, that works as well, until someone invents an english wheel or planishing hammer for paper, along with a cardstock that can handle the stretching needed to form such objects. I try to design using the smalest ones I can--but they just seem unavoidable.

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