Extreme Hollow Building of Triangle Split Cane Rod

"Is This Possible" -7' #3-4 rod weighting 2 oz (57 gram).
© Tapani Salmi 1/2015

I have tried to make triangular (TRI) bamboo fly rods for some years for several reasons:
- TRI rods give clear advantages for long rods
- TRI construction results in lighter rods
- TRI construction is especially advantageous for two-hand rods

To make any fly rod lighter it is common to use hollow building:
For hollow construction there are several methods like scalloping, fluting etc. In most of techniques there are some "bridge" material left inside the rod to increase the strength of the structure.

I have build single hand TRI rods simply by planning the strips thinner. This causes problems e.g. to scarf joint, which are not very strong using this construction. Therefore I have used "bayonette" -joint for the heavy two hand triangle rods.

In autumn 2014 Rolf Baginski (German professional rod maker) demonstrated a very practical method to make hollow built rods using "artificial" very light bridges inside the hollow tube. He took some cotton stabs, moistened them with water and added then some drops of common PU glue (like Gorilla, Bison, Cascol etc). This results foaming "balls" which are then inserted inside the rod. The foam and cotton then swells strongly and thus form a very hard composite -type structure inside the rod resulting in "bridges" to support the hollow structure.

The foam & cotton structure is very light. It also is very easy to manufacture, no extra tools are needed.

These were the reasons to adapt Rolf's method into triangle rod building.

How to do it?

I have planned the strips quite thin. The thickness of the strips for the tip part of rod have been 1,3 - 1,4 mm and for the butt 1,4 - 1,8 mm. I make this planning simply using my hand plane.

Simple modification of my plane to make 1,4 mm thick strips

Three strips for a triangle rod

Thickness of the strip is here 1,37 mm (=0,054")

Baginski beveller for 120 degree corners for the triangle rod

Triangle hollow-built rod cross section

How to make wadding fibre - PUfoam - composite?

For the composite you need fibres and PU -glue. Fibres are cotton -type and soft. I have used polyester wadding used in pillows and blankets.

To insert the foam balls inside the rod easily and fast I have tied the wadding balls with a thread 10-11 cm apart from each other.
I have the thread and cotton hanging from the roof.

Then add some water to each of them using small syringe and then some drops of e PU glue to the balls.
Here you absolutely need protecting gloves because PU glue makes your hands black!

To glue the cane strips I have used PU glue, Titebond and epoxy as usual.
After applying the glue to the strips I simply set the thread with PU balls on the strips and bind the rod as usually to have the wadding balls inside the rod.

The fiber - glue composite is quite strong and much stronger than PU foam alone but it is very light!

The foam makes firm bridges inside the hollow rod to support the structure and increase the stiffness.

Here you see the foam inside the hollow scarf joint ferrule

"Is This Possible" -7' #3-4 rod weighting 2 oz (57 gram).

On Clark's Classic Cane Rod -site there were a theme "Is This Possible" asking if it would be possible to make a 7' #3-4 rod weighting less than 2 Oz (57 grams). Clark's site

This certainly is a hard challenge to an amateur rodmaker using hand tools and I decided to try using this very simple technique.

I started by selecting a straight taper from my Italian friend Saverio Pandolfi, changed the taper into triangle and got a taper with WIDTH of the strips as following (in mm's):
2,06 -2,54 -2,98 -3,49 -3,97 -4.45 -4,95 -5,46 -5,97 -6,45 -6,95 -7,46 -7,94 -8,45 -8,92 -9,46 -10,0

I planed the strips and the planed them into 1,3-1,4 mm thickness. This decreased about 50% of the weight of the strips. To change them into 120 degree corner I used my Baginski beveller to sand 60 degree corners into 120 degree.

For the bridges I took polyester wadding balls, moistened them using water and added Gorilla glue. I used UHU300 epoxy for the strips. The wadding and glue added about 3 gram to the total weight.

Then single thin layer of PU varnish and I had 7' rod blank on 45 gram.

To keep the weight low I decided to use scarf joint ferrule. As the hollow scarf joint is not very strong I put a longer part of wadding composite into scarf area.

The blank seemed good but to my surprise cork and reel seats and even line guides are quite heavy.
The obvious method was to make a small hand grip, reel seat with aluminum rings and thin wire line guides.

Here you see the small hand grip and very light hardware.

The result was a 56,8 gram rod casting #4 line.

In addition to the small rod I have made single hand 10' #7 salmon rod and two hand salmon rod using the same technigue.

I hope you may see and try the rod on European bamboo rodmakers meeting in Sansepolcro, Italy May 22-24 2015!

Papyrus reeds are triangular in cross section!

If you have any questions, please contact me - tapanisalmi AT hotmail.com