Maintain Roundness of Cylinders

[SCEtoAUX]

People use formers inside of aircraft fuselages to help maintain the shape. Formers can also be used to help maintain the shape of cylinders when making towers for buildings. They also help in the glueing of other parts to the towers by supporting the glue tabs. Measure the diameter of each end of the cylinder and cut formers to fit inside. Holes in the formers help positioning and securing the other former.

Pictures showing the slight tear drop shape without formers:

It does not look too bad now but continuous handling during the build of the model will distort the shape.

Formers:

They are different sizes here because the tower is part of a lighthouse and is tapered. This technique will also work on cylinders that maintain the same diameter throughout the entire length. You could leave one of them without a hole, but if you do make sure the one with the hole is the first one you insert into the cylinder. You can use the open end of the clylinder to seat that former then use the hole to position and seat the second former.

One of the formers inserted:


Other former started:

Note the position. The hole in the first former is used to seat this one.

Turn the cylinder over and use something to reach through the hole to seat the other former.


Second former in position and seated:


Tower with both formers in position:


I have found that this also works with tires on vehicles that have a disk for the outer and inner side and the tread that is a strip with the sawtooth glue tabs. I always had trouble putting the outer and inner disks on the tread until I tried a variation of the technique described in this post.

[umtutsut]

One trick I use before inserting the formers is to re-roll the cylinder from the inside using a wooden dowel. I concentrate on the joint area, which sometimes ends up slightly flattened.

Just my .02 zlotys.

Les (The Voice of Authority)

[whulsey]

Doug, good demo.

To add for vehicles, you can cut a very small slice off the formers to help create the flat spot on the bottom of tires. Good way to help hide any joints in the tread also by putting them on the bottom. Of course this won't work if you want the tires to roll ...while you go 'vroom, vroom'.

[SCEtoAUX]

Yes, I try to flatten the seam also by using various implements. That helps to keep the roundness of the object, but handling does sometimes distort, hence the formers.
No 'vroom 'vroom but sometimes an chunka-chunka-sssssss.

[whulsey]

Had a few of those.

[MichaelS]

I punch 2 holes in the former then use pointed tweezers to position.

[peter taft]

Very good idea {s} Helps with rigidity and overall shape.

[brosen1953]

how are the formers measured? especially if the shape is not round? trial and error?
thanks

[Papierschnitzel]

Thank you for this great tip!

[SCEtoAUX]

Originally Posted by brosen1953

how are the formers measured? especially if the shape is not round? trial and error?
thanks

Cylinders are round. The ends of a frustum of a cone are round. There are also ways of drawing ovals of specific sizes. Geometry is your friend.

If the shape is not round or oval try glueing the not round part into shape and use trial and error to get the shape of the formers. Carefully put the piece on some scrap and carefully trace around the perimeter of the ends to get a rough shape. Cut out the shape and see if it will fit. If it will not fit, try again.

With the lighthouse I glued the part to form the long frustum of the tower and tried measuring the diameter of the ends until a satisfactory diameter was found. It only took two tries mainly because of some squeezeness when holding and measuring.

There is probably some mathematical formula to figure the diameter of a resulting circle given the length a curved line. I have a bunch of scrap paper and thin cardboard garnered from various packages so it was not a big deal to try the trial and error thingy.

If the part forms a regular cylinder the ends can be used to figure the diameter of the disk needed. Measure the length of an end to get the circumference so you can figure the diameter of the disk needed.
Diameter = circumference/pi.

If there are disks provided on the parts sheet that will be used to cap the ends you can cut the disks out then place the resulting empty circles on some scrap and trace around the inside of the circle and cut out those disks to use as internal formers for the ends. I find that it helps to do something like that to maintain the shape and to provide backing for the sawtooth glue tabs when the end caps are glued in place.