Steel-Cored Casting Rods. 
Editor Forest and Stream: 
It is not an easy matter to treat a technical 
subject of this character so that it can be easily 
understood by the average non-technical amateur, 
but it may be worth an effort, especially as there 
seems to be more or less uncertainty as to the 
merits or demerits of steel-cored rods. Be¬ 
fore the action or behavior taking place in a 
compound structure of this nature can be fairly 
comprehended, it is essential that the character¬ 
istics of the materials employed should be well 
understood, as on this depends the proportioning 
of parts, which will result in securing or defeat¬ 
ing the object aimed at. 
It is easy to understand that if you place two 
thin strips of wood of equal size across an open 
box and sit on them that each will bend and take 
an equal share of the load, and that if you re¬ 
place one of the strips with a piece of steel of 
equal size that the latter will sustain practically 
the entire load, as the wood strip will support 
very little until it is bent far below the steel. 
From this it will be readily understood that in 
order to apportion the loading or carrying 
capacity of the two materials, their sections must 
be proportioned to accord with their individual 
characteristics. 
When we inclose a core of steel as in our 
compound rod, the matter of finding out what 
we have and knowing definitely what load we 
are imposing on the steel and what on the wood 
is an interesting and entertaining subject for a 
high grade mathematician if the solution is at¬ 
tempted mathematically. But for the benefit of 
the amateur who would like to try his hand at 
a rod of this kind I will make an effort to pre¬ 
sent the problem in a light which will enable 
him to understand the ruling factors, and sim¬ 
plify the matter of their determination. 
As the rod bends at any point to a certain 
radius of curvature when in action, it follows 
that the steel must bend with the wood and as¬ 
sume the same radius. This may sound like a 
“bright” remark to some, but it must not be lost 
sight of, as on this fact, coupled with the fact 
that the two materials have very different de 
grees of rigidity, the problem of rational pro¬ 
portioning depends; for, it is important to know, 
when the two materials are combined, what the 
maximum fibre stress will be in the wood and 
in the steel, so that we may take full advantage 
of both according to their characteristics. 
If the maximum arm or wrist effort applied 
to the grip in making the cast is such that the 
outer fibres of the wood receive a stress of say 
.10,000 pounds per square inch, a not unusual 
figure, and we desire that the outer fibres of the 
steel rod shall receive a stress of the same in¬ 
tensity, then it follows that the diameter of the 
steel core must depend on the outside diameter 
of the wood or bamboo, and on its modulus of 
elasticity (E). As this for good bamboo is, say 
3.500,000 pounds per square inch, and for steel 
*ay 28.000,000 pounds per square inch, a ratio of 
1 to 8, or it follows that when both mater¬ 
ials are stressed alike, the steel core diameter 
must be one-eighth of the wood diameter. 
If, however, we wish to stress the steel twice 
as high as the wood, then it will be necessary 
to double this ratio and make the core one- 
quarter the diameter of the wood. Hence, if we 
divide the modulus of elasticity of the wood by 
the modulus of elasticity for steel, and multiply 
the quotient by the number of times the stress 
in the steel is to exceed the stress in the wood, 
we will get the proper diameter of the core in 
terms of the wood diameter. 
It would be useless to put in a size of core so 
small that the wood will be compelled to do 
nearly all the work because of lack of stiffness 
in the core, and it would be equal folly to put 
in a core so large that its stiffness would not 
permit the wood to do its share of the work. 
You can readily see from this that we are deal¬ 
ing with a type of rod in which proportions must 
be right if we expect to make each material— 
steel or wood—do its proper share of work. It 
is also absolutely essential that the taper of the 
solid wood. (Do not say that this must be a 
bull in figuring; it is not.) From this it will 
be seen that the wood core displaced represents 
one-half of 1 per cent of the strength of the 
solid rod, when the core diameter is one-quarter 
of the outside diameter; and inasmuch as our 
steel core is stressed twice as high as the wood 
is, it follows that its strength will represent one 
per cent., but as we have pulled out one-half of 
one per cent, of wood to make room for the 
steel core, we are left with a net gain of one- 
half of one per cent, in favor of the steel-cored 
rod. And now for the beauty of this act of 
stupidity. 
As the specific weight of steel is at least eight 
times that of first class bamboo, we have for 
weieht a rod made up as follows: 
Area of steel core, 6.25 per cent @ 8. 50.00 
Area of net wood, 93.75 per cent. @ 1. 93.75 
Total relative weight. 143.75 
Area all wood rod, 100 per cent. @ 1.100.00 
Relative difference by weight. 43.75% 
That is to say to secure a net gain in work- 
RELATIVE strength of hoi.low and solid rods. 
steel core shall be such that at all points its 
diameter is a fixed percentage of the wood 
diameter, say one-quarter. 
As the value of E (modulus of elasticity) for 
steel cannot be increased by hardening and tem¬ 
pering, the only use of such treatment is to raise 
the elastic limit so that it may not take a per¬ 
manent set or bend when in action. It is clear 
that unless we stress the steel at least twice as 
high as we do the wood we might as well leave 
the rod solid or with a wood core. 
By way of digression let me say that the 
origin of the steel center rod is, I believe, due 
to utter ignorance of what bamboo is capable 
of carrying in the way of stresses, and what 
treatment it actually submits to and sustains in 
tournament work, especially in long distance 
casting. I have spent my active life time in the 
designing of machinery and structures, but I 
know of no class of work in which the working 
stresses in any members of machines or bridges 
run as high or stand the abuse that does the bam¬ 
boo in the great majority of first class fly- or 
bait-rods. 
And now, to get down to business. Let us 
take a rod with a steel core whose diameter is 
one-quarter that of the wood and do a little 
figuring. If we take this rod and pull the steel 
core out of it—assuming, for illustration, that 
we can—we will have a hollow rod whose actual 
strength is 99.5 per cent, of the same rod of 
ing strength by use of the steel core we have 
increased the weight of our rod nearly 44 per 
cent. Had we increased the weight of our solid 
wood rod less than one-half of one per cent., or 
say a butt of three-eighths inch diameter by 
less than .002 of an inch in diameter we could 
have gained in strength more than the one-half 
of one per cent, due to the steel core. I do not 
know of any combination of steel and wood, 
which, weight for weight and action for action 
in use, can hold a candle to clear bamboo when 
selected with special reference to service; and 
I wish to counter any claim that can be made 
relative to the ultimate strength of the steel- 
cored rod, for before a rod is strained up to 
the breaking point it will be seriously crippled. 
In no practicable manner can a steel core help 
matters, for so long as it cannot increase the 
elastic character of the material surrounding it, 
over that of the same material when made solid, 
it cannot secure an advantage. 
A rod breaks but once. It is used for making 
thousands of casts, and every advantageous and 
pleasing quality in use will score a thousand to 
one against the one possible chance of breaking. 
That judgment which comes from keen ex¬ 
perience in matters of this kind has led many 
to doubt and question the value of the steel- 
cored rod, but even if it could be properly 
made—in the matter of reliable workmanship 
which I am inclined to doubt—the expense would 
