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hot air

by Frank Neunemann

A number of years ago, back in 1988, I started to tackle up for my first split bamboo rod project. Like everyone of us, I was faced with the question: "What type of oven shall I use?". At first I wanted to build myself a copy of Garrison's oven, but after some consideration I decided to try out my own, entirely different design, allowing for good temperature control, without using open propane flame to heat it.

Instead of the open flame I wanted to use one or, if necessary, two hot air guns. I was reasoning that hot, streaming air should be much better than resting hot air enclosed in the conventional oven. Resting air is one of the best insulators against heat. Furthermore, hot streaming air immediately transports the evaporating water off the bamboo, so the drying effect should be much better than with a conventional type of oven.

If you look at the drawing you might ask yourself why it is vertical. There are several reasons. Before I started my first bamboo rod I had the opportunity to look at an old Orvis Battenkill rod that had been glued using Resourcinol. That convinced me not to use that type of glue because of the dark glue lines, that I don't like very much.

Instead I wanted to use a colorless, or slightly tan colored epoxy glue (a German product called UHU Plus) that I have been using for many other wood and metalworking projects for a very long time. It had proven to be very reliable, resistant against heat and solvents, inexpensive, available in small quatities, and easy to get.

Best of all, the strength of the glue can be increased by more than 2 1/2 times when cured under heat. Therefore the oven also should be suitable for that task as well. Freshly glued sections should not touch anything during the curing process.

The verical oven is somehow similar to a chimney. Hot air rises up by itself because it's lighter weight. In addition to that, the fan of the hot air gun adds to that. It forces the hot air down to the bottom of the oven, warming up the inner tube that holds the bamboo rod sections. From the bottom the air streams up the inner tube, warming up and heat treating the bamboo, and constantly transporting the evaporating water off the rod sections.

Material etc: From the nearby hardware store I bought several pieces of galvanized stovepipe. In the "dark corners" of the workshop I found some scrap sheet metal, a handful of blind rivets, and a hand riveter. The top plate was made of a piece of 150 x 150 x 2 mm sized sheet metal. For the bottom I used an old stainless steel cover for a hot-plate of ؘ 230 mm. All is held together with self made sheet metal corner braces and blind rivets.

The outer pipe (Ø 120 mm) is made of two pieces of equal length, which is very important, if something drops down into the oven which should not. The heigth of my oven is suitable for 2-piece rods up to 8 1/2 feet. For longer rods the heighth should be adjusted accordingly. To hold the rod sections, there are two vis-a-vis notches cut into the upper edge of the inner tube. These two notches hold a piece of wire to hang the sections. The inner tube of Ø 70 mm can hold up to three normal sized trout rod sections at a time. The inner pipe is attached only to the upper section of the outer Ø 120 mm pipe. This allows dismantling the oven. The two outer pipe sections are just inserted into each other, the lowest rivet also serves as a stop bolt.

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printed on  17.06.2024

Copyright by ©Frank Neunemann, 1996 - 2024