Paper Mache accurate Oval round shape

I'm trying to find unique large ways to create oval round shaped items using the least amount of tools available for poorer nations who don't have access to machine tools, through the possibiliity of elimination i've come to the paper mache conclusion but! i'm not comfortable there's no way to gage the roundness of my paper mache shape cause once its finished it gets coatings of gel coats for strength then advanced fiberglass cloth techniques can be applied.

I'm Using dirt, plastic and sand with a shovel to create a cheap large effective weatherproof temp mold we apply the paper-mache, (no woodwork tools allowed for parts) but! once its out we need immediate damage assessment of the roundness, more paper means more weight. We can use some paper but not hog-wild

I wish for the resin and fiberglass to be the only expensive export/import to dramatically cut costs & experience, it doesn't have to be perfect it just has to pass the eye test, human eyes are very good at detecting roundness but i'd feel more comfortable if there was a tool or device i could use, don't want to wing it with fiberlgass cloth, it could be very costly. Imprortant its round like a quarter dome you might see in the m-east rooftops

Having any tips would help me immensely too demonstrate to others, i just can't think of anything. 1st time Balance is real important, i could add more paper mache later but more paper means more weight when resin soaks in from my resin chamber (resin bubble remover) glass still needs to be added to final weight

Any ideas no matter how small on roundess perfection tools/tricks could possibly help alot.

If you cut a template of half your dome from a bit of flattened out oil drum and hold the top of it to a peg in the middle of your mould you can simply rotate the template to shape the surface of the mould. The subsequent layers will then follow that shape. Same way a decorative plasterer makes a ceiling rose with a sled

Need to know size and what a oval round shape is. A drawing is worth a thousand words. Possible to generate an ellipse with a few sticks but 2D not 3D.

Ball with a hole in it so it can slide smoothly on a piece of string, pin the ends of the string to the each end of the mould with sticks, ensure ball moves smoothly across whole surface when slid back and forth on the string?

A point on elipse is defined as having constant sum of distances to the ends, this works in 3d as well as 2d.

Will need some experimentation with size of ball to see what works best.

Middle eastern 1/4 dome roof gives a good clue to shape.

Although arabic architecture has many dome type roofs the platerers method would work for them all, just cut the template to suite profile and rotate that to refine shape of earth mould. Potters do similar with templates too.

Edited By JasonB on 25/11/2020 14:19:13

May as well say it before someone else does.... do you actually want it oval or elliptical?

Rob

Use a balloon ! you can blow it up to any size you want, apply your papier mache, resin etc then let it down, e voila a spheroid shape!

George.