You filled a light action graphite blank with the expanding foam that you can buy in spray cans. Will the blank be stiffer? Harder to break?The weight would be more but would it effect it as a fishing rod. Harder to break is the main thing, would the foam help? Jesse

I think you'd need an awful long tube to be sure you got the stuff distributed along the entire length. My guess, and it's only that, would be that it would make the rod a lot stiffer. My limited experience with the expanding foam is that after it cures, it's really pretty hard stuff.

Expanding foam in the pressure can expands a tremdous amount. I used it to insulate a boat Ice Box.
And it sets up fast. I can picture the possibilty of it fracturing the rod.


Dan Hogan
The only way to have a friend, is to be one.

Hi Jesse I think it would do a lot of things that you mentioned but I am afraid It would possibly make it more suspect to breakage. Like Gerry says when it hardens it becomes pretty stiff depending on the density you choose. I think it would only go up part way in the blank and where it stops it could form a sheer point and probably right where you dont want it. At the very least you can count on a marked increase in weight. Go slowly in this area. IMHO

Jesse,
It would not be significantly harder to break because the outer most layer of graphite, farthest away from the foam, is what almost always fractures first when a rod breaks because it is under the most stress and strain. At the very center of the blank, called the neutral axis, their is almost no stress or strain so anything that you do there is not going to make the rod less likely to break under load.
Also, the foam, because it has a very low modulus of elasticity, would also tend to significantly decrease the rods performance.

Jesse,
There is a 2 part liquid urethane available. Pourable. It expands on an 8:1 ratio, depending on a couple of variables. With one end of the rod open it should expand out that way and not crack the rod although I don't think that would happen anyway. Working time is longer than with the spray can.
Find a company that does cold storage insulation work and you could probably "bum" enough to try it.

Why not just buy a medium weight rod?

If you want a rod that is more difficult to break why not just go to a glass rod. A glass rod is about 4 times as tough as a graphite rod. If you add foam to the center of a graphite rod my guess is that it will lower the performance to almost that of glass and it will not be any tougher.

Expanding foam is rigid, as some have already posted so it would break the first time you flexed the rod. It would also be tough to get it into the blank far enough and in enough quantity to expand and fully fill the blank when it expands.

I've got some of the 2 part foam here at the house (I'm in Chesapeake) left-over from a boat building project. You're welcome to try it out if you want to experiment.

/Scott

It's been done, sort of. Hexagraph rods are graphite skins with foam core, but they are first laminated then milled and glued up like a bamboo rod.
john

Wow, short of you trying it on a cheap, disposable blank, it seems hard to say what will happen. Practically everything that has already been mentioned will happen, including and most especially the fact that the rod is not likely to be any more "rugged" than before you filled it. NOT on a strength per weight basis, anyway. In brief, I think the benefits would be very temporary. It may last a few fishing trips, at most.

Structural Foams are usually used to fill space in a laminar or planar compartment. That is where they shine. Not in a tubular compartment, mostly because a tapered tube, by virtue of its own geometry, is already extremely strong. For a tube which has to bend like a fishing rod does to be both a shock absorber and a spring-catapult, the tube’s strength cannot be improved upon very much by adding internal supports. Sometimes FLEXING is a more powerful way to react to a force than an attempt to increase stiffness. Like a palm tree in a hurricane - better to bend with the wind, than to stand upright and be snapped off at the top or at the root.

Foams don't tolerate a lot of compression, and they tolerate sheering forces even less. Once deformed, they have little ability to resume their original shape. Put out some foam of your particular brand, and see how it handles deformation, against a broad load and a point load. Is it elastic or resilient? Does it bounce back after pressing on it with your finger? How about when you dig in your fingernail? Is it quite stiff and not deformable? If it is deformed, is it brittle? ... If it is brittle, and not resilient, then once deformed, it will never again serve to support the original shape. It has been crushed. If it is more resilient, it may last.

I don't think these foams tolerate much deformation. Inside the rod blank, they would be subject mostly to a radial flexing, not so much a pressure force, like when you squeeze your empty beer can. Think of a roll of coins. You can bend it in an arc, but not compress it. Once you flex the foam-filled rod blank deeply a few times, there will be a lot of sheer force on that plug of foam. I think that there will be either a cracking of the crystal structure or a sliding of disks, like the coins in a roll being bent. I honestly think that the rod blank when flexed has a greater capacity to destroy the foam, than the foam has capacity to support the walls of the tube.

Frankly, I would be very surprised if the rod blank after a few dozen deep flexes did not reduce the foam to a useless collapsed meringue, with few cells walls left intact to hold the air inside the bubbles, this reducing the solid part to a salt-like grit. Like the sawdust that comes off when you cut that cheap styro-foam junk that hobby crafters use for holiday projects. Then the collapsed foam would just be like so much sand shifting around inside the tube, eventually settling in the rod butt.

If that urethane foam is brittle, it will collapse in no time flat. If it is resilient, it will survive. Remember, a foam expands by the evolution and trapping of gas in cells as it cures. Forming tiny and compacted clusters, like grape clusters or bubble-pack wrap. Once you pop those grapes or bubbles, because the flexing exceeds the elastic properties of the foam's solid structure, (rubber-like or glass-like?), the weight bearing ability of the foam has been permanently lost.

So much of this question of suitability depends on the formulation of the particular foam that you try. All I can say is, give it a try if you want to. I'm not trying to squash a bright idea. BUT I am hoping my comments help you decide what is going on if things are less than satisfactory on the first go-round. … Good luck, Cliff Hall, Gainesville, FL-USA+++

If you are breaking rods, what blanks are you using and for what fish ??
Are the guides set up correctly ??
Rod to light for the fish ?

You want your rods as light as possible, that would make them heavy, and I see no reason for it.

Most of you know that I have a high volume rod shop and 99.9% of the breakage is the graphite baitcasting and spinning rods. Once the rod goes out the door there is no telling how it is going to be treated or what the customer is going to use it for. Fiberglass is outdated for these small rods and does not sell, it is well received for boat and trolling rods. I just had the thought about the foam and threw it out to see if anyone has tried it, apparently not.. Jesse

If you are using quality blanks it is probably the users.
Where are they breaking ? The tip or butt.

The things that break rods, impact, overstressing the tip, etc., aren't likely to be corrected by filling the center of the blank with anything.

Most likely, filling the center with foam will result in the blank breaking when put under a good load. A tubular structure has all sorts of things going on, and that must go on, when it's flexed. Some fibers stretch, some are forced to compact (they really don't like to do this) some are caught "in the middle" so to speak and have to go through several motions during the flex. The structure itself must take on somewhat of an oval shape as it flexes. Anything you add to the blank that upsets these normal and required movements may likely cause trouble.

Buy a cheap graphite blank and shoot it full of foam and see for yourself. Most blanks will withstand at least some of this sort of thing, but in the end I think you're going to make it less durable, not moreso. Try it and see.

............

The foam might be put to better use if you installed a zert fitting on the back of your customers head and filled his skull with the white stuff!

Gon

Saying that the material does not tolerate deformation very well, as Cliff stated, is just another way of saying that it has a low modulus of elasticity.

Graphite is a great material to make blanks from mainly because it has a high modulus of elasticity and low weight. But it is a relatively soft material so it does not tolerate impact well. It also does not have a high strain energy or toughness, about 25% of glass, and its tensile strength is not as high as one might like so it is subject to being over-stressed. As Tom points out, the vast majority of graphite rods break from either impact or being over-stressed. The over-stressing very often being the result of high sticking.

Adding foam to the inside of a blank will not make the outer layers of graphite harder, it will not increase the strain energy or the tensile strength but it sure as heck will decrease the modulus of elasticity and add weight. So in my judgement it will not do anything that you want it to do to reduce the breakage and will do a great deal to lower the performance.

Tom also has a very good point about a blank becoming slightly elliptical when bent. If internal foam prevented this the stresses would go through the roof, dramatically increasing the chances of breakage.