Roll up flue pipe hand curving

This post is about the segmented rolling of curves into long pieces of titanium or stainless steel foil for making backpacking stove flue pipes.

Note: This is just one little part of a 12 part series on improved stove pipe rolling. You may wish to start at Part 1 as hors d’oeuvres and then taste from the banquet.

Introduction

A previous post dealt with rolling curves into short lengths of foil.  It should be read to give context to this post. The post was getting too long, so I decided to make this separate one on curving a long roll-up flue pipe for a backpacking tent heater/stoves.

It is a particular challenge if it is to be done very well. The need for good pre-forming of a flue pipe prior to the development of a new shape-memory by/heating is detailed in my post about heat memory shaping of roll-up flue pipes with an alcohol flame lance.

Briefly, the conventional method for forming a virgin roll up flue pipe is to force the foil into its new pipe shape and heat it ( I suggest inadequately) to have a new memory of this shape. This is done successfully without roller curving. However, this technique leaves the joining edges of the foil flat and poorly fitting together.

Examples of virgin pipe forming videos:

A. Solo forming, causing many sharp crinkles that will diminish the quality of the pipe over its long life. 

B. Two people rolling the pipe, causing fewer crinkles. 

C. A well-organized team of three people rolling the pipe and causing only a few minor crinkles.

While the last team forming of the pipe is good there is a better crinkle-free solo method that will be the subject of another post when available.

Infinite tube ‘roller’

The poor fitting problematic edges of the strip of foil (titanium or stainless steel) and crinkling can be fixed by:

•   pre-curving the edges (segment-wise) with a short roller,
• using a moderately wide anvil (a wooden one in the above photo) and
• using a thick sealed cell foam pad made from a portion of a sleeping mat (shown to the right in the above photos).

Starting on one side, at one end of the strip of foil, a partial curve can be rolled into the edge by using fingertip/hand pressure directly over the short roller. After completing the first sequence of overlapping rollings, further runs of rolling may be required to get the required curvature along the edge depending on the strength of your fingers/hands.

During the curving of the edges, the roller can be used to form some curving across to the middle of the strip. This is relatively easy to do and for me, it just happened more or less by accident. It will make the subsequent pipe formation very much easier.

Next, roll the other edge of the strip the same way, including the curving across to the middle.

“This requires a considerable effort that is delivered through only the fingers/hands. If you are like me it may make you sweat and I don’t sweat easily. So you will be excused if you have a cup of tea between rolling runs. However, I consider the effort is worthwhile as it can make a superior crinkle-free flue pipe that is easier to assemble in the bush on many trips.”

When both sides are strongly curved and the middle is gently curved (like a spoon drain shape), the long floppy strip of foil will change to a shape that is quite stable and much more suited and ‘willing’ to forming into a pipe shape when required. It will reduce the tendency to crinkle as shown in the three pipe forming videos above.

Flue pipe forming

After all this curving, the flue pipe should be formed as in video C. I prefer to use a lot more retaining rings to make the join line more even before the next heat memory treatment.

Using heat to establishing a new memory of the flue pipe shape 

Once the flue pipe is well-formed, its new shape can be thoroughly preserved by heat-treating with an alcohol flame lance. This treatment will make it ‘remember’ this new shape whenever you release it from the storage roll, as in the photo below.

Heat treatment by ‘using the flue pipe on a stove’ will work to some extent. The ‘heat memory’ can be improved by inverting the flue pipe to heat the other end. However, it will still leave the middle section of the flue pipe largely untreated.

An alcohol flame lance is a simple and cheap DIY tool that will allow heat treatment to be quickly and evenly applied to the entire flue pipe length. 

Tim

Addendum

The hand-rolling described above puts a heavy load on the fingers. Consequently, I came up with this simple ‘drag roller’ with a fat and soft handle. It can be comfortably held in one hand and the other hand can hold the work. It means that the full force of arm muscles can be applied to the work. It does not roll, but rather it can skid over the metal easily and still has the desired curving effect. I put a trace of olive oil on the skid surface to make the skidding even easier. “It is much easier to use than the roller.”