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Side-by-side comparison





As mentioned some time ago, I have been experimenting with Lô ô bamboo for making rods. Lô ô (Bambusa procera) is a giant bamboo from Vietnam and has many of the same characteristics that make Tonkin bamboo (Pseudosasa amabilis) such an excellent rod building material. In addition to that, its average diameter is significantly larger than Tonkin’s, and its internode length is such that 3 piece rods up to 8 ft in length can be made nodeless-spliceless, each section made of strips from a single internode. Its only drawback is that it has a slightly lower Modulus of Elasticity, requiring a slight change in taper dimensions to match a Lô ô rod to a Tonkin rod made from the same taper - multiplying the overall diameter of the taper by a factor of 1.035 usually does the trick.

Last summer, I made two Lô ô rods based on my existing tapers, adjusted accordingly, a 3 piece 7.5 ft rod for a #4 line and a 3 piece 8 ft rod for a #5 line, and tested them extensively in Norway. The rods performed fully as expected.

Now to enable a true side-by-side comparison, for myself, for other people interested in acquiring a rod, and to demonstrate at shows, I’ve made an identical rod (3 piece 8 ft #5) in Tonkin bamboo, using the original dimensions. Both have a calculated test curve of 0.222 lbs and show identical calculated deflection curves. The actual measured deflection curves can be seen in the attached photos, both rods being stressed by a weight of 100 g.

Theoretical deflection curve, applicable to both tapers.

Actual deflection of both rods, under a tip load of 100 g (98 g of lead weights plus 2 g of inline weight (plus the string…).

98 g of lead weights.

Close-up of the tip deflection.

This clearly shows that the overall deflection under identical load is identical - tip deflected 1/3 of the total rod length. As such the interconversion of tapers from Tonkin to Lô ô clearly works as intended. Rods feel comparable when casting as well.

What this also shows however is that the actual shape of the deflection curve is not completely identical - something shown by other similar comparisons (check the Classic Fly Rod forum for examples). Apparently it’s not only the Modulus of Elasticity that is different between Tonkin and Lô ô, but also the change in MoE with increasing thickness - see Frank Stetzer’s essay on flexural rigidity for a background on varying MoE with bamboo strip thickness (https://www.hexrod.net/Documentation/flexural_rigidity.pdf). I use his equation to account for that in my deflection routine - and maybe I should try and come up with a specific parameterization for Lô ô bamboo as well. Note that the Tonkin rod - with the somewhat stiffer tip section, actually more closely resembles the theoretical deflection curve... 

However, the fact that the overall deflection and line weight estimation with my current algorithm results in acceptable comparability between Tonkin and adjusted Lô ô tapers suggests that that might be overkill…

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