Indoor News and Views

A quick note on using polyimide tubing

By: Mike Kirda

I can’t make tissue tubes consistently to save my life. I can make a dozen just to get one that fits. Then I go to replace a component and discover it won’t fit due to different size tissue tubes. Frustrating to say the least.

I believe I first heard about Polyimide tubing from Jake Palmer. He sent me some and I immediately fell in love with the stuff. You can get in all kinds of sizes. Amazon Supply is probably the easiest source. Various medical supply houses can supply others – A quick search on Google will find you several suppliers.

So what is it and why is it better?

Single and double wall – Double is much darker

The tubing is straight, strong, light and consistently sized. For the non-chemists, it is kind of like plastic/nylon tubing, but thinner. It will come in three wall sizes, they call it single, double and triple wall – Essentially 0.00125, 0.0025, or 0.00375″ thick walls. For our purposes, single or double wall is ideal. Single wall is typically sufficient for lighter classes, double wall for heavier.

The tubing is ideal for connecting parts. Wings to wing posts. Stabs to stab posts. Prop shafts to prop hubs. You get the idea – anywhere tissue tubes are typically used.

The one down side – nothing we typically use for glue likes to stick to it. There is one pre-step to gluing. Wherever you need to glue it down, you need to coat the tube with the lightest amount of thin cyanoacrylic (CA) you can get away with. Ambroid/Duco stick well to CA.

For wing posts attached to a fuse, a light bit on one side is all you need.

For attaching a wing to a wing post, a bit of glue on the contact surface and on the sides. A bit of balsa triangle will help to anchor the post to the wing.

For a prop spar, you need a bit of CA on just on the inside of the tube, then use the normal celluloid glues. A touch of acetone will loosen it up without fear that the tissue tube itself will turn to mush.

Use a bit aluminum foil as a pot for thin CA and a pin to dip into the CA and apply it to the tubing.

Matching wing posts to the tubing can be done in few ways:

1. Careful sanding
2. Use of a draw plate to as a dowel maker for balsa
3. Use of the tubing itself – Just jam it into the tube and it will remove the excess. (This is my current favorite.)

Cutting the tubing may be a bit tricky at first.

• For parts that do not require a lot of insertion – i.e. prop spar tubes, I just use sharp scissors.
• For other parts, it is best to shove a bit of light scrap balsa into the tube, then use a razor blade to cut it. I just use whatever double edge blade I have on hand typically to cut it this way. A sharp single edge blade should also work well.
• Art Holtzman has offered another way – Insert a numbered drill bit that fits inside and cut with blade around the bit.

A public thanks to Jake Palmer for turning me on to this tubing and also LeoP and Kang Lee for the initial help in learning how to use it.

I also have some for sale – 0.080″ ID single wall tubing that is ideal for F1D VP hubs. See: http://propblocks.com/miscellaneous-stuff/