Al Baldauski’s PMQ Conversion Chart (Excel File)
As I am currently off work recovering from a minor operation I have been bumming about (there's a clue to the operation!) making a few two 2 strip quads from the oddments in the garage. I have just glued one up, hot melted on a set of ferrules, taped on some snakes and guess what? The rod delaminated after lets say a few dozen casts. Now here's the question, I have built two strips before with no problems whatsoever and I have one that has been hard fished by a few kids this season with no trouble at all. The glue I have used on this last quad was within date and not old stock BUT what I did differently from my previous experiments was to place the guides on the sides that didn't contain the nodes and as such the glue line was not on the neutral axis of the rod. Hence when flexed the two strips WANTED to separate. What do you lot think is this the reason for the failure? The glue line being highly stressed because it wasn't on the neutral axis? (Paul Blakley)
Please excuse my ignorance but I am assuming that a two strip quad is made of two nominally rectangular strips of cane glued to leave enamel surfaces top and bottom with one glue line nominally at the mid depth of the section? I don't follow the bit about nodes/guide spacing. I assume the nodes are staggered top and bottom along the length?
Any way, to try and help with an answer rather than ask more questions! If the glue line is at mid depth and hence nominally on the neutral axis then this is actually the worst place as the complimentary shear stress (that the glue has to sustain) is at its maximum at the neutral axis. This is the opposite from the bending stress that reaches a maximum in the outermost fibers and zero at the neutral axis. The shear stress distribution is parabolic so in practical terms in remains fairly high within the middle third of the section so small variations in the depth to neutral axis should not make a lot of odds.
A normal four strip quad does not of course have this problem as no glue lines are parallel to top and bottom faces. (Gary Marshall)
I should however point out that despite the engineering accuracy of these comments it does not mean that 2 strip quads won't work, just that you need to use good glue! (Gary Marshall)
To continue, and for those of you who have built and fished with them, which side do you chaps put the rings/guides on:
a) On a side with a glue line in ?
b) On a side without the glue line and containing the power fibers and nodes? (Paul Blakley)
The guides should go on one of the sides without a glue line. I agree with Gary Marshall that the having the glue line in the neutral axis puts the greatest shear stress on the glue, but I've had no problems so far with a PMQ that's been fished pretty hard. What kind of glue did you use? (Robert Kope)
I usually use resorcinol on my rods but in this instance I am using PVA. I have built my last two strip units with PVA, guides on the enameled sides and have had no failures despite the rods being 'hammered' this year by a couple of kids that have been demoing them. I'll replane the failed strips, rebond and place the guides back on the enameled sides before handing over to the 'testers'. (Paul Blakley)
I believe PVA (Titebond II Extend) is a better rodbuilding glue than most makers think. It's also non Toxic. (Marty DeSapio)
What exactly is a Poor Man’s Quad? And how is it made? (Shane Pinkston)
A Poor man’s quad (PMQ) is a four sided rod that is made with only two strips of bamboo per section, not the usual four. This means that two opposing flats are enamel and the remaining two are the sides of these strips. That is what it is in a nutshell, but someone else who has more knowledge than I can expand if necessary. A four strip quad requires two sets of forms owing to the different angles on each apex of the strips. A PMQ only requires one set. Now that I think about it, probably much easier to run through a router set up, too. Anyone? (Carl DiNardo)
This is what I plan on trying. I have done this to make straight tapers.
Run a length of hardwood on edge through the planer attached to a same length of a 1X6. Shim the strip on edge to correspond with the straight taper you want. I have used several thickness of double sided tape for this. Run the strip through the planer high end first and start removing wood. Keep running it through till you have planed the full length. Remove the tape and tapered strip from the 1X6. The end that that was planed first will be the thick end of the bamboo strip. Attach the bamboo strip to the tapered strip with double sided tape and run it through the planer. I was trying this with rough beveling and it worked. It should work to make the PMQ with a straight taper. I may be all wet but I will find out soon as I plan on trying it next week.
Will let you know if it is a winner or a tomato stake for next years tomatoes. (Tony Spezio)
I was engaging in some off-line correspondence with one of the list members and mentioned that once my leg gets healed enough I'm allowed to put some weight on it, maybe I'll start trying to make a PMQ. This seems attractive to me for a first rod, since no forms are necessary. Anyway, he mentioned that he had cast some PMQs and felt they were weak (no power).
I was quite surprised about this, as the math theory says they'll have far more power fibers than a hex rod, and should be close to equal with a 4 strip quad. I've never cast a PMQ, but I have cast a nice little 4 Strip Quad that Bob Maulucci made, and it certainly seems to me to be capable of a nice amount of power.
It probably doesn't matter much for me in the long run if it's a slow soft rod or not, as I'd be using it as a small stream rod where I'd be unlikely to ever need to cast with more than 20-25 feet of line out the tiptop, I'm curious about the properties of the rod, however.
So, my question for those of you who have made/cast PMQs, how do you feel they compare to hex rods and 4 strip quads, assuming same lengths, line weights, etc.? (Claude Freaner)
My experience has been just the opposite, however it may be because I have built 7 foot or less rod lengths. I find the PMQ's are at least as powerful as a standard quad. The only real issue I find with them is that they are more difficult to straighten, and some, but not all, seem to not want to stay straight. If you build a heavy or longer rod, the % of pith in the butt will start going up. That may create a power issue, but I don't know that for sure.
The only big one I have ever cast was a para 15 conversion. It didn't have as much punch as I thought it should, but then again, I'm not so sure an extreme parabolic taper is a good candidate for conversion. Everything changes when you change geometry. You have to build a few conversion sets to understand it.
If you want a good taper to start with, go to the rodmakers site and bring up the PHY midge taper. Multiply the numbers by .95, and you will have a zippy little 4 weight quad. (Tom Smithwick)
I was casting Robert Kope's 2 strip quad last week, and it seems every bit as powerful as any quadrate rod I have ever made. Maybe that says more about me than about the 2 strips, but I like them. (Bob Maulucci)
I cast Tom Smithwick's PMQ at the SRG and I have to say it is one of the nicest casting bamboo rods I have cast. It was effortless to make a good cast and real smooth. I did not think it was soft at all. I came home with plans to make one but knee replacement has kept me out of the shop for a good while. It is time for me to start thinking about it again. Go for it, you will not be sorry. (Tony Spezio)
I have made several rods to the same taper in conventional 4-strip quads and in 2-strip quads. As far as I and my friends can tell, the actions are identical. (Bill Fink)
I've built only one, and have another under construction. I made mine rectangular in the tip, so I can't directly compare it to any other taper, but I don't think it is weak at all. The one I built is a 7' that I intended for a 4 wt, but it seems to like a 5 wt better. The only thing I'd be concerned about is if you build a larger rod, the pith in the butt could be a problem as Tom pointed out.
The pith could cause a problems with both the stiffness and the durability of the rod. Because the entire center of the rod has lower density of fibers, it will be more prone to compression when the rod is flexed, which could result in a rod that feels limper. I'm actually more concerned about the durability since the center of the rod is where you have the greatest shear forces and that is where your only glue line is. I'm not an engineer, but it seems to me that when you get down to the butt of a larger rod, this glue line will be bonding pith to pith right where the shear forces are at their greatest.
Other than that, make your strips very wide, and get them absolutely straight before you start planing. (Robert Kope)
I am not an engineer either, but it occurs to me that, as the center line in a poor man's quad (the glue line) lies dead center in the casting plane, there would be no sheer forces whatsoever. All the forces of compression/tension occur on either side of a center line, increasing only as the outer walls are reached. I think the term "dead center" is apt, in that there are few if any forces at work there. (Bill Harms)
Taper discussions are my favorite, I can't resist casting my line in on this one...
The center line truly does experience no stresses whatsoever so long as the tensile and compressive strengths of the material in question are equal... this however, is not usually the case. For most woods the compressive strength is much less than its tensile strength, this causes the neutral axis to move away from the center line during bending and move toward the tensile side. Bamboo behaves in a similar fashion, its much stronger in tension than compression... test this for your self by taking a castoff section (I know none of you have those laying around, I'll send you a stick from my lifetime supply upon request) from the junk pile and bending it until it breaks, the outer surface of bending will break with the usual fibers sticking out but not before the inside of the bend gives way first and buckles (shows as a crease). Try it some time.
I'm not an engineer either I just like to make fun of them. :) (Kyle Druey)
I'm afraid I have to disagree a bit with you on this one. I do agree that the compression side will act more on the pith than the power fibers, moving the compressed power fibers a bit closer to the center line, but I also think that the pith on the tension side is going to be compressed toward the center line by the tension on the power fibers. A quick visual example of what I'm talking about would be to take your garden hose and slowly bend it - you can see the compression side move in, and you can also see the tension side collapsing toward the center as well. Without spending a whole lot of money on some really esoteric testing equipment, I suspect we'll never know for sure. Since I haven't won the lottery yet, guess it'll have to wait. <G> (Claude Freaner)
What is the best way to convert a taper into a PMQ? Can I just create a quad version of a hex taper in Hexrod and do the dimensions from that---
Or do I also need to use a multiplier of some sort since there's just two strips? (Joe West)
You can just convert a hex taper to a quad and use that for a PMQ. There may be minor differences due to the 2-strip construction, but they're not enough to worry about. (Robert Kope)
I have a Florida vacation to the Gulf coast coming up in a few weeks and was thinking of tossing together a meat-stick PMQ to catch some redfish with.
Can anybody recommend a powerful 8 wt or greater quad taper that I can PMQ? Or should I just take a Nunley bonefish and Quad-ify it in Hexrod? (Joe West)
Start with about an .080 or .090 tip and make a straight taper increasing about .009 or .010 every 6". Should be fast and able to pick up a sink tip or throw a long line. (Bob Maulucci)
I think you mean .009 or .010 every 3". The .009/3" is the same as a Powell "B9" and the .010/3" would be faster than that.
At .010/6", station 95 on a 96" (8 ft.) rod would be .090 + .010/6x95 = .248 - a real noodle! (Tom Bowden)
That is .009 or .010 for the strip, not the rod. Sorry for the confusion, I am getting so used to working in strip sizes not blank sizes. It is exactly the Powell B9 formula. Think about it, .009 every 3" would be a broom. (Bob Maulucci)
Does anyone have any straight tapers that I may be able to use for making a PMQ?? Either fly or spinning rods would be appreciated. I'm hatching an idea and I think straight tapers would work best. (Todd Talsma)
This is from Wise Fisherman's Encyclopedia. I think it is a good basis for taper design. The full text is available on Reed's site.
Fly and Spinning Rods
Fast Action .034-.038 in. per ft.
Medium Action .028-033 in. per ft.
Slow Action .023-.028 in. per ft.
Plug Casting Rods
Fast Action .041-.045 in. per ft.
Medium Action .036-.040 in. per ft.
The taper figures given above infer the rate at which the diameter changes per linear foot. Individual strips, of course, will measure but half this amount. A sense of proportion must be exercised in the design of any rod. For example, it would be utterly ridiculous to design a 7-foot fly rod with a tip much larger than 1/16" (.062) Suggested tip diameters for various fly rod lengths are:
7 foot - .060"
71/2 foot - .067"
8 foot - .075"
81/2 foot - .082"
9 foot - .090"
These are given as beginning points, a tolerance of several thousandths of an inch either way being perfectly proper." (Bob Maulucci)
Having just finished my second PMQ (and my last PMQ!), I have some thoughts that might help other beginners tackling PMQs:
1. While PMQs require no planing form, they are actually much harder to make well as compared to hex rods. Your abilities as a woodworker and your manual dexterity are tested to a higher degree.
2. There are not 5 other strips to provide straightness and support. Therefore, your strips must be dead-@ss straight. Trying to straighten after glue-up is MUCH more difficult than with hex rods. Since straightening is really the most difficult, laborious, and time-consuming part of the process and the one that that requires the most experienced touch, this very fact may want to make you want to think twice before tackling this construction method if you are a beginner.
3. Truly using no planing form will almost certainly make a rod that has canted angles toward the tip. Build some kind of a form or jig as the weight of the plane seems to change the angle of the cut on the very flexible tip section.
4. Ferruling these things is a pain because they are usually rectangular. I don't own a 4-jaw independent chuck. You really need to have one, or you must cover the rod with tubing of some sort. That second option is only stopgap as it is really not that accurate. You also must broach/peen the ferrule on a piece of key stock or the rod itself.
So, my conclusion is that while it is an interesting process that provides a fine rod, it is actually quite a bit more difficult to make a rod approaching perfection than 6-strip construction. Don't forget that most published info and tools are for hex only or MAYBE square quads, but rectangular quads leave you in a wasteland.
If I had it to do over again, I'd have spent my time and energy making 2 hex rods.
While my first two rods (which I shan't show the likes of you master craftsmen for fear of rebuke!) cast well, they do not approach perfection. Not that they should, though.
Just my 2 cents, take it for what it is. (Joe West)
Why is the PMQ rectangular and not square? I've never built a PMQ, but I have built many four-strip quads in both square and rectangular versions. I have always turned the ferrule stations by hand by rotating the blank and filing off the corners. It seems like that should work with a PMQ as well. I too have found the rectangular rods hard to straighten, although I am not sure why they are harder than a square quad. (Bill Lamberson)
The particular taper I have is rectangular. No magic.
I think the straightening might have to do something with the unequal stiffness in different planes.
I did my first one by hand and it turned out better than the one I did on my lathe with 3-jaw chuck! Agree on that one! (Joe West)
1. Yup. Work slowly, check your strips early and often, both for taper dimension AND squareness as you plane them down. Eyeballing squareness does NOT cut it here.
2. Straighter is better, certainly. If you're binding the tip section for glue-up, hanging it with a good weight (5# or so) seems to result in a much straighter section. Tom Smithwick also has a no-binding method involving a piece of metal angle stock and a bunch of bulldog clips that also tends to leave the sections straighter after glue-up than they otherwise might be. His method is in the archives...
3. Tips are a bear. Again, checking your squareness early and often helps, but those thin sections do tend to squirm around under planing pressure. I have a feeling that a tip planing board with a shallow (~0.020" deep) groove in it, say 0.100 - 0.125" wide would serve to stabilize the thinnest section and keep things from getting too far out of hand. I've not tried this yet, but will let you know
4. I cut my ferrule stations by hand with nothing more than sandpaper. Seemed to work a treat. IMO, the "float" you have doing the ferrule station by hand compensates for a multitude of sins. I used 4-tab ferrules on my PMQ, and crowned and thinned, they laid right down w/o resorting to peening. Your mileage may vary, depending on what ferrule you use and how you want to prep it.
So, my conclusion is that..
While I agree that it's tougher to approach "perfect" with a PMQ, you learn a lot in making one. It'll teach you to be careful in your work, that's for sure!
If I had it to do over again, I'd have spent my time and energy making 2 hex rods.
On the other hand, I feel the time I've spent making my first PMQ was well spent. No, the rod won't be a "looker," but that was never the goal. The goal was to learn technique and process in dealing with cane, while producing a serviceable rod. Practice with a purpose, as it were. I also submit that if one worked out their technique and process to the point where they were making a decent PMQ, they would be well down the learning curve toward producing a near perfect hex rod right out of the gate. My PMQ isn't quite there, but it's only s/n #1 (and still under construction). Next one will be much improved! (Todd Enders)
Was that my rectangular taper? I must admit that the one PMQ I have finished is the sorriest looking rod I've done. Still, I feel it's nothing to be ashamed of. I took it to Grayrock 2 years ago and the FFF conclave in Idaho Falls last August. Joan Wulff even cast it. In my view, the casting characteristics of that rod more than make up for its cosmetic flaws.
I do agree with most of your observations about the care and skill that PMQs require. I have not yet had to discard a single hex rod section I've made. I have completed only one PMQ and have 2 more that I just glued up (for the second time), and so far have about a 40% reject rate on PMQ rod sections. The plus side is the minimal tools required, and the time saving resulting from only having to deal with 2 strips for each rod section (if you can get past the QC problem). I planed out two 2/2 rods and glued up one of them last Sunday. Of course, they still need to be planed to width.
My first PMQ I underestimated how wide the strips needed to be and had to discard the tips after they were glued up because they were not wide enough. On the first attempt at the two rods I'm working on I overcompensated and made the strips too wide. I have bound mine with a homemade Bellinger-style binder and the tip sections were something of a challenge because they would flop and jump going through the binder. Binding with string also puts nearly all the pressure laterally, parallel to the glue line and only presses the strips together at the edges. This resulted in tip sections that looked fine initially, but had bad glue lines when I planed off the sides. I think this was exacerbated by the PU glue I used which tended to foam and force the strips even farther apart in the center.
My solution for this problem was to get some small diameter Delrin rod (3/8" and 1/4") and split it lengthwise with the bandsaw, then plane off the saw-marks on the inside. I placed half of the Delrin rod on either side of the rod section when I ran it through the binder. This makes the sections round or oval in cross-section as they go through the binder and puts all the pressure perpendicular to the glue line. The ones I did last Sunday have no visible glue lines. They're also quite a bit straighter than ones I've bound without the Delrin rods, though they're still a far cry from the straightness of a hex rod right out of the binder. (Robert Kope)
This is a no-brainer, but it just occurred to me while planing the replacement tips for a couple of PMQs. I hate to think what that says about the condition of my brain ;-)
When I plane strips for a PMQ, I mark the stations on the rind side of the strips, and write the half-dimension of the rod next to the mark. This makes it quicker to check progress toward the final thickness than to be constantly referring to my notebook. This also makes it simple to correct for planing errors on the first strip.
Anyway, here's the tip: if you overshoot the target thickness at a station on the first strip, you can just add the error to the thickness of the second strip, no harm, no foul. For example, if the final thickness of the rod at a station is 0.130, you are shooting for strips that are 0.065 at that station. If you plane too much off the first strip so it's 3 thousandths undersized (0.062), all you have to do is add the error to the other strip (make it 0.068), and there's no problem. It isn't going to make a bit of difference if the glue line goes exactly down the center of the rod or not. (Robert Kope)
This is what I did on two PMQs, too. They both cast great (but are a little ugly, not anything having to do with the dimensions being off, but rather my general lack of skills).
Can you (or any gurus) think that there might be any empirical difference in action in this situation vs. normal? Off axis bending??? Maybe not? (Joe West)
A recent discussion on PMQ's caused me to think about the properties of a 4 strip quad vs. a two strip PMQ. With a given taper, is there a noticeable difference in the characteristics of the two rods.
Consider the cross section of the rods. In a PMQ there are less power fibers found at the center of the 2 strips. In the 4 strip cross section, the apex of the 4 strips meet at the center and it would seem that the 4 strip quad would therefore have a higher concentration of power fibers. To take that an additional step, it would stand to reason that there would be differences in the characteristics of the rods.
I don't have any experience with quads, so perhaps those that have build and cast both might have an opinion. Is my hypothesis correct? (Tim Wilhelm)
Do you notice a bit of a spine in your PMQ's or do you try to make them a little on the flat side to compensate? What I'm getting at is that the occasionally ballyhooed Montagne rods are reported to feature a non-square cross-section. Couldn't the PMQ's duplicate this effect? (Jim Utzerath)
I expected the things to be directional due to the asymmetrical distribution of power fiber. I never did any actual deflection tests, but it does not appear to be a big issue. I don't see why you could not play around with asymmetrical sections if you wanted to, but I would not start out that way.
Basically, I agree with what Mike wrote on the topic, and agree that a hollow built real quad offers the serious advantage. I think of the PMQs as a quick and dirty rod and build them that way. On one of them I noticed that the sides were slightly concave. I figured out that I had glued with a water base glue, planed the sides while moisture was still present, and the sides shrank inward after the rod was built. That got me to thinking it was like hollowing the rod on the outside. I never pursued the idea, thinking that strength of the narrower pith material would be a problem, but the rod would be sort of like an I beam. (Tom Smithwick)
Not to change the subject, but what do you gentlemen think of Per Brandin's assertion that the hollow hex is lightest of all. Look here.
On those crazy PMQs why not just drill out holes from the pith to pith side. They could be Wiffle Rods. (Bob Maulucci)
NO rod is the lightest of all, but that rod doesn't deliver in the casting department.
As in the parabolic versus fast tapers controversy, we are interested in the work the rod design will perform. Even a 'light' hex section is relatively inefficient insofar as its ratio of work-performing flat area to neutral axis material, along for the ride, because the 'sides' of the hex go around the horn to get to the other side (and must do so, because the work-performing flats are of less width than the section depth, so this width and inefficiency are necessary, merely to keep the section from deflecting from the plane of bending).
Moreover, 'light' is a blindness, and even an obstruction to natural objects, unless it is a discipline respecting the other, obligatory objects of design. The purported virtues of 'lightness' can never be taken alone to depict overall virtue. Neither the builder nor the user of a rod are truly interested merely in weight. We need so much stiffness to generate the acceleration we are after. You can't get that without mass; you can't exceed maximum permissible section depth per bending, because if you do, you exceed either (or both) maximum permissible tensile or compressive stress; and therefore you can only increase stiffness beyond maximum section depth per bending by increasing flat width in the work-performing flats.
A quad is the first logical/practical step in solving the need for more performance. Rectangular provides the singular avenue for further performance, without limitation -- and is (by far) the highest-performing section design.
Regular design objects therefore predicate AND REQUIRE a rectangular section; and of course, the ratio of work-performing flat area per neutral material is the greatest in the rectangular section -- so here as well you have the greatest efficiency (weight per work performed, or, if you prefer, 'lightness' [per desirable work]).
In any tubular structure, a design which deploys *any* material to optimum advantage (weight per necessary service) deploys the material at optimum diameter and minimal permissible wall thickness. The maximum deployable diameter is limited to where, in the bending structure, maximum compressive or tensile stress are incurred.
Thus, where we are deploying any material to maximum advantage, we are deploying it at maximum permissible section depth; and wherever, to achieve performance objects, it is necessary to increase flat width beyond the miniscule flats of the hex, to square and beyond, this makes the superhollow rectangular section the lightest -- as well as the singular solution for the further respects of the discipline.
The superhollow rectangular section therefore will remain the most powerful and fastest recovering section in history, for all history to come, because it is physically impossible for the hex or generic quad to deliver its performance -- or to do so more efficiently (with purportedly less weight, per what?). (Mike Montagne)
My rather extensive rodmaking work, in all geometries, hex, penta, quad and trirods leads me to be certain that on an equal-weight basis the penta is clearly superior. The trirod is not to be ruled out. Quads are always slower and need to be beefed up in the butt area to compare in quickness to pentas. But great rods can be made in all geometries. (Bill Fink)
You are correct that the real quad has more power fibers, but the missing fibers in a PMQ are at the center of the rod as it flexes where they don't do much good. I am not sure about large scale PMQs, never having built one. The small PMQs that I and others have built seem to perform at least as well as their more distinguished cousins, in fact, I harbor an uneasy notion that they might actually be better casters. If so, it must be that the rods are lighter because of the less dense material at the center, and the power fibers being concentrated at the outer edges where they do the most good. These rods are what they are, they will never have the class of a real quad, but it's not because they don't cast. (Tom Smithwick)
I don't remember the fellow's name who invented the PMQ, but back in the 80s he asked me what I thought about the concept before he built one -- no opinions, just engineering ramifications. Of course, I compared it to the rectangular section for him. Basically, the meanings of the differences are these.
Indeed, a PMQ may be ever so slightly lighter than a solid quad, because it loses the density of the power fibers in the side strips of the conventional quad. This difference will be most substantial in the lower butt sections, where it means less. In upper tips, where the effect would be greater, there is virtually no difference, because your dense fibers are extended so much toward the neutral axis.
A dramatically hollow-built quad however (which is an assumable goal of a quad builder) will inherit a far more substantial weight (loss) advantage, because, for instance, it would be physically impossible to render supported hollow structures in the PMQ as light as my superhollow construction. In my hollow built construction, the entire central core of the rod is removed -- even through the ferrules and reelseat.
* By far the greatest potential weight advantage therefore goes to the superhollow quad; and therefore a PMQ may show a negligible, relatively meaningless weight advantage only over an equivalently tapered solid quad. Whether this miniscule potential advantage even exists however, will depend much on the success of the builder; and laying out any proof to a claimed advantage, because the purported advantage is so dubious and contingent, will be a suspect affair -- silly as the story of the King's Robe, while entirely ignoring the far greater advantages of hollow construction.
The structural integrity of the PMQ and conventional quad will be approximately equal. The neutral axis, which moves across the plane where the PMQ is glued together, incurs very little stress. The neutral axis, being defined as a region where tension and compression are not incurred (although there must be shear to either side then), naturally moves across from forward to backward sides in any material which does not have equal tensile and compressive strength and reaction to stress. So there is some stress on the PMQ glue lines and pithier material of the central cross-section, but this should be of little consequence.
The greatest shear stress is where the greatest differentials between tensile and compressive stress in adjacent regions are engendered. Depending on material and construction, this may be anywhere in a section. The greatest tensile and compressive stress however are always incurred at the forward and backward extremes of the casting plane.
The greatest potential stress therefore is in the outer corners. Here, providing best gluing techniques are deployed, the conventional quad may enjoy a small advantage in both the reinforcement of the outer corners by the glue, and in further strength added by the power fibers of the adjacent side strips. Here, we must recognize this advantage may never be a meaningful factor, if PMQs do not exhibit a tendency to come apart in the corners, particularly after a great many repeated cycles of reversing stress. My experience with quads and the gluing methods I used demonstrated perfect reliability over severe use, including extended use on British Columbia steelhead, with fast sinking lines and huge wet flies cast at long distance.
* Particularly because the heavier fibers of the cane may serve somewhat to reinforce the corners of the PMQ, perhaps there is no issue here. But we know how seasoned cane can tend to split, particularly after some damage; and some of us may elect therefore to prefer to reinforce the corners with the glue lines of the conventional quad. Of course, alternative methods may be deployed to reinforce the corners of the PMQ, but, if this entails impregnation, there will be considerable cost to the assumed weight advantage over only the solid quad, with a possible result being that the remainder of the pithier areas, picking up the impregnation possibly to an even greater degree, consume more weight than the assumed advantage over the conventional quad.
Other than the virtually negligible weight advantage a PMQ may have over a solid quad, there is no reason whatever to assume a PMQ casts better. After all, this is the only real difference in the rod, and, after gluing, depending on glue consumption, the difference may not even exist over a conventional, solid quad. Particularly as, in the PMQ, we are cementing the rod together across the less dense material of the inner pith, who knows, we might even more than pick up the weight difference we have assumed we have lost there, in additional glue penetrating the porous central material of the section. Additionally, the PMQ suffers some minor disadvantage in concentration of power fibers in the corners, where the greatest contribution to stiffness is made. Obviously, this is a detriment to performance.
MEETING DESIGN OBJECTS
If weight loss were a bona fide object of PMQ construction, the builder has eliminated the much greater advantages of superhollow construction from their horizon. Usually, a whole separate set of tools and skills will be necessary to restore that prospect when the builder finally recognizes that superhollow construction vastly multiplies the efficiency of the quad, further separating it from conventional hex construction. So the builder who embarks in the PMQ direction will obstruct their achievement of far more meaningful weight advantages to be achieved by hollow building techniques, at the cost of retooling for truly superior (and demonstrable) weight advantages.
If weight loss is an intended advantage then, why limit the potential advantage to the negligible potentials of PMQ applications? (Mike Montagne)
I really wanted to try a one-piece taper, but didn't want to invest tons of time in planing six strips so I decided to try a PMQ.
I soaked the strips for a few days, straightened them out tonight, rough tapered them into some slightly oversize rectangles, and bound them together. Then I went to throw them in my oven to dry them out and heat treat them.
Small problem. My mica oven is only 5 feet long (the rod is 6 feet). I swore I built the oven 6 feet long for this very purpose - NOT the Case.
What's the best way for me to heat treat these strips? I don't want to go to any expense making a new type of oven. I guess I could poke a hole in the insulation of my oven and cook half of length at a time. Maybe someone has a better suggestion though. (Aaron Gaffney)
The old fashioned way---
A piece of iron pipe, threaded on the ends, capped with pipe caps with a hole in each, hang with wire loops, put the strips inside, cap and heat with a propane torch while turning the pipe in the wire loops. You are done when no more steam comes out of the little holes. (Steve Weiss)
I recently got some black steel pipe from Home Depot for some woodworking pipe clamps. They were covered inside and out with some smelly oil-solvent mix, I suppose to prevent rust. Make sure to scrub them with a detergent or degreaser first. Also, just a thought, the bottom 10 inches or so will be covered with reel seat and grip. Maybe do your regular heat treatment but with the butt end sticking out and then hit the butt end with a heat gun for a few minutes. (Joe Handwerker)
I've been told, by people who seem to know, that if you flame, you don't need to heat treat. I tried it once as an experiment. Made 2 rods as nearly identical as possible from the same culm and only heat treated one beyond the flaming. No difference I can tell, both cast the same, no sets etc. For what it's worth. (Neil Savage)
If you take the tip diameter and add 0.012>0.015"/5" of travel along the rod length you will have by in large replicated Garrison's tapers. 0.012 = a slow rod whereas 0.015" = a fast rod.
For spinning rods use 0.022"/5" of travel along the length. (Don Anderson)
I split out my strips for a 2 strip quad which I am making for a friend, I have, mostly straightened them. Now I am ready to start planing, ...on the sides, the part that is not tapered, the width of the strips are not equal, I assume that I will clean these up with a plane after the glue is dry, is there any dimension that I should be should be shooting for, for aesthetics sake is there any reason I should not shoot for a equilateral square shape as opposed to a more rectangular shape. (Joseph Freeman)
You should be shooting to make them square. Once they are near or close you can plane both strips at once. Helps keep them equal. (Pete Van Schaack)
There actually is a reason to shoot for a rectangular shape rather than a square one, and it has nothing to do with aesthetics. The configuration of a 2-strip has more power fibers on the top and bottom than it does on the sides. This means that if the rod is square, it will be stiffer flexing in casting plane than side to side. If you only make straight casts and keep the rod perfectly aligned with your casts, this is not a problem. However, if you make casts other than straight casts, or don't hold the rod in perfect alignment, the rod will have a tendency to flex more to the side than vertically. To offset this tendency, the width should be greater than the depth.
Unfortunately, there is no simple ratio that you can use. The increase in width will depend on the average modulus of elasticity of the fibers on the surfaces of the rod. At the tip of the rod, it is nearly solid fibers and there is probably very little difference. The difference will be greatest at the butt of the rod. To make a rod with no spine, the width-to-depth ratio would have to be greater the butt than at the tip.
Interestingly, Mike Montagne made rectangular quads that varied in cross-section back in the 70s. However, his were not 2-strip quads, and his reasons for the variable aspect ratio had nothing to do with eliminating the spine. Mike built 4-strip, hollow rods with internal ribbing. His rods were square at the butt with a maximum width-to-depth ratio at the tip. He wanted his rods to have a spine, and to favor bending in the casting plane to make them more "accurate". He also argued that this cross section reduced the stress on the bamboo where it was greatest. (Robert Kope)
Several months ago this issue was discuss and I did some calculations and an experiment to prove them. The power fibers and hence the MOE of the rod is relatively constant to a depth of about 0.090 inches, or a diameter of 0.180. Any part of the rod smaller than this needs no corrections. Any diameter greater than 0.180 needs correction in a varying amount.
To eliminate calculations I made up a look-up chart to find your rod dimension and the corrected value for that dimension to the nearest 0.005 inches. You can interpolate between these numbers.
To prove the theory and accuracy of the idea I built a Two strip section 60 inches long and tapered from 0.300 to 0.150. First with a square cross section. I put the section on a deflection board and tied a weight on the tip to approximate the bend when casting. This showed that the rod was significantly stiffer in the front-to-back plane than in the side-to-side plane. So much so that the rod tended to twist with the weight on it.
Then I planed a rod using the correction chart to increase the side-to-side dimensions so that the rod was wider side-to-side than front-to-back from the butt out to the 0.180 dimension. When I put this rod on the deflection board, it bent the same amount in both directions with no tendency to twist toward the weaker plane.
To get this chart, go to here. (Al Baldauski)
Al, thanks for the link. This backs up my own observations. If I get a good culm with a thick band of power fibers, the tip sections of my PMQ's are almost pure power fibers. Beyond that, there are other factors involved. and I could not argue with someone who wanted to make the butt section a bit rectangular. Personally, though, I have not found there to be any need for that as there is no particular tendency for PMQ rods to flex to the side. Consequently, I keep the butt section as square as possible. (Paul Gruver)
I have not built a full PMQ so I can’t comment on its performance except from what others have said and the “laboratory testing”.
If you build the rod square, not only will the rod be less stiff side-to-side, it will also be less stiff front-to-back that a four strip quad. This has been borne out by others who have built PMQs who commented in the last discussion on this topic back in September. (Al Baldauski)
For 2-strip quads (PMQ's), before I glue them up, I like to plane the sides of the strips square, and rough taper them, but I don't worry too much about it. You do want to taper them somewhat, so they don't roll when you try to do the final sizing, but having them 2x, 3x or even 4x over size is not a problem. It's just more material than needs to be removed after the glue has dried.
A tip that is only .060" thick, but .325" wide will be hard to control while you try to work it down, and will require extra care in achieving the proper taper along the sides. If you knock a little off the sides as you go, being careful to keep it well above the final dimensions, you will have a lot easier time getting down to the final dimensions. (Paul Gruver)
A PMQ with the guides on the side with the glue line will indeed be stiffer than with them on the enamel side. It'll also cast a fly anywhere except the spot which you are aiming at! This anecdote comes from from one data point (I never cared to try it again!) and from absolutely no theoretical background at all. (Lee Koch)
It may be an option for larger two piece rods and use the enamel on the sides for the butt section for added strength and use the traditional enamel top and bottom for the tip section. (Ken Paterson)
Or you can increase the thickness (front to back dimension) by 8.8% to compensate. (Al Baldauski)
If I felt I needed more strength in the butt section of a PMQ, I would be much more inclined to just add more layers. All you want are the power fibers anyway, so what's wrong with using four .050" strips, that are mostly power fibers, instead of two .100" strips, that are 50% pith, to get a .200" thickness? (Paul Gruver)
This just does not make sense. Why would a section with power fibers on the sides be stiffer than one with the power fibers on the top and bottom, which are under the greatest tension and compression? (Robert Kope)
Exactly so. My experience has been the opposite of what has been said. The rods, particularly the butt sections are stiffer when the power fibers take the tensile and compression forces. The other way, some of the power fibers are in the neutral zone of bending, where they are useless. (Tom Smithwick)
So I take it that Roark's(sp) Formulas for Stress and Strain is all wrong. Please show me the mathematical proof.
This bamboo is really some strange material to work with. (Jerry Drake)
Please show me the mathematical proof.
All I have is some rods. I'll bring one to Roscoe, and show it to Al. I've only built a few, but they have all been the same in terms of directionality. (Tom Smithwick)
Here's a follow up query:
Does anyone have first hand experience casting a rectangular quad ALA Montagne, and if so what comments can be made regarding strength v weight, a d accuracy/tracking (Robert, are you using the rectangular quad you built very much)? (Chris Obuchowski)
I've built both rectangular quads and widened hex configurations. I think there is little weight savings. The directional tracking is excellent as long as your casting is lined up well with rod's plane of bending. If you are a caster who cants the rod off line, the reel is commonly turned out a bit, the rods still bend in the soft plane and twist in the casters hand. A good friend of mine and a list member, now deceased, was an excellent caster, but usually cast with the reel turned out about 30 degrees. He despised those configurations because they continually wanted to twist in his hand while casting. (Bill Lamberson)
I don't use them much at all. I actually have 4 of them: 2 rectangular PMQs and then, when I got the handmill, I made a couple of 4-strip quads (one solid and one hollow, with identical tapers). It's really simple to do with the MHM if you have a flat cutter head and the 92 degree head.
First you mill the top and bottom strips to width. Then set the taper for the strips on the sides, mill the side strips. Then switch to the flat cutter and mill the top and bottom strips to the same height as the side strips.
They do tend to cast in the plane of the guides, but that's probably not what you want when you're fishing. Most people don't hold the rod perfectly square with the direction they cast, and when you're fishing, you don't necessarily want to make straight casts. (Robert Kope)
Well, I'm not the guy to argue engineering theory, that's for sure and Tom, I have no explanation for my observation that the PMQ I made (8’ 5 wt based on an Edwards 43, glued with URAC 185 FWIW) was stiffer with the guides on the glue line rather than on the enamel, but that's what I observed, particularly in the butt. The butt is pretty thick, .330 at the base. (Lee Koch)
It may depend on how thick your butt sections are, that is, how much pith is in them.
Somewhere there is a tradeoff between the stiffness of two "2X4"s on edge versus two "2X4"s flat with a lot of squishy stuff in between. The problem in a PMQ is further complicated by that squishy stuff compressing, thinning the section and making less stiff.
And none of this happens in the tip section anywhere the total section is greater than about 0.180 inches since each strip (0.090 thick) is essentially all power fiber. (Al Baldauski)
And none of this happens in the tip section anywhere the total section is greater than about 0.180 inches since each strip (0.090 thick) is essentially all power fiber.
I think this is correct. In the interests of furthering the discussion, I took a closer look at the two PMQ's I still have around. One is a PHY midge variation, with a butt diameter of about .250, and a diameter of .230 at the hook keeper. I measured thickness and width, thickness being power fiber to power fiber, and width being the glue line sides. This rod is slightly wider than it is thick, by about .001/.002. It is not highly directional, but does want to kick toward the glue line sides, despite the size variation.
The other rod is the 8 foot 6 weight With the .003/inch taper I built for the Catskill challenge a couple years ago. That's the one I "hollow built" by drilling a series of holes clean through, the point of the drill being set on the glue line. It is highly directional, wanting to really kick toward the glue line, and I remember the butt being like that before I drilled the holes, too. I remember thinking about whether the rod would twist when casting, but took the risk of putting the guides on a power fiber side, because the other plane was so significantly weaker. I have to confess, however, that this rod is thicker than it is wide, and near the hand grasp it's about .004/.005, which has to be contributing to the kick. I don't think that variation could explain all of it, however. The thickness at the hand grasp is about .330. Just for further amusement, I did an oscillation test, and the tip does travel straight up and down. The thing got pushed really hard by some very good casters during the competition, and no one seemed to have any problem, except that the thin hammer grip was too small for a couple of them.
Anyway, I am confused by Lee's results, and would like to hear from other who might have a PMQ around to test. I do think that my results support Al's statement the other day that a thickness over about .200 is where you will start seeing some effects from the 2 strip construction. (Tom Smithwick)
This is pure speculation on my part but it may be that the difference in stiffness front to back vs side to side causes a twist in the rod because your may not be casting perfectly on plane. The twist may occur without regard to which plane is stiffest.
The 0.005" difference in thickness at the butt end is not enough to make a really noticeable difference in casting.
To prove which plane is stiffest, anchor your rod at the grip as you would on a deflection board or clamp it on a bench. Orient the power fibers up and down and hang a weight on the tip. Measure the deflection. Rotate the rod 90 degrees and measure again. (Al Baldauski)
to prove which plane is stiffest, anchor your rod at the grip as you would on a deflection board or clamp it on a bench. Orient the power fibers up and down and hang a weight on the tip. Measure the deflection. Rotate the rod 90 degrees and measure again.
OK - I did that. I used a #2 lead sinker for a weight. The 6'3" 4 weight deflected 20" in either direction, and so can be said to be not measurably directional. The 8 foot 6 weight was significantly directional, deflecting 17.5" in the power fiber direction, and 21 inches in the glue line direction. Again, the rod shaft has holes drilled through it in the glue line direction for the first 1/3 of the shaft, so the numbers might be exaggerated, but as I said the other day, the butt section was directional before the holes. Anybody else got rods they can test? (Tom Smithwick)
You said, " The 6'3" 4 weight deflected 20" in either direction, and so can be said to be not measurably directional."
That sounds reasonable. I think you said this was a quad version of a PHY Midge so the butt section would have been around 0.218 inches, hardly any pith in that cross section.
It would be nice to see the results of some others out there to confirm this directionality. (Al Baldauski)
I never got in to making PMQs; at least not yet. However, I always thought if I were to make a larger PMQ, I would make the butt section a sandwich. Top and bottom no-taper power-fiber bread, and middle "meat" section with all the taper; if it were really fat, two pieces to make the taper(more power fibers). Then, if you wanted to get really fancy, you could split or cut the middle of the "meat", move it to the edges and create a hollow-built PMQ...
A little over the top, but maybe I'll have run out of experiments at some point and give it a try. Just not sure how to glue it up as hollow built. (John Wagner)
Awhile back I said, ”Show me a mathematical proof.” So far nobody has so I found some time this afternoon to test run some numbers of my own.
Consider the following:
An I-Beam with flanges of 2” x 6”,
The web being 2” thick and 2” high giving a apace between the flanges of 2”. This will give an overall profile of a square. The Y-axis passes through the flanges and the web and the X-axis passes perpendicular to the web.
You will get the following results.( at least this is what I got)
Ix = 105.333
Iy = 73.333
Letting the thickness of the web go to 0 yields: (Tom’s holes centered on the glue-line)
Ix = 104
Iy = 72
If you make the web 6” thick hence a square beam:
Ix = 108
Iy = 108
I stand corrected. The PMQ should indeed be stiffer with the guides on the power fiber side of the rod shaft. Just goes to show that one is never too old to put their foot in their mouth.
An simple Excel file is on the web if you would like to check my work. Here is the link.
Change values in the yellow section. (Jerry Drake)
I built an experimental rectangular PMQ (wider than deep) hollow fluting the glue line sides - effectively turning it into an I-beam. It twisted terribly when cast, presumably because it was not rectangular enough. I never pursued the experiment.
From what Jerry is saying if you want a PMQ (effectively an I-Beam) to be equally stiff horizontally and vertically (as in a square 4 strip quad) it needs to be slightly rectangular (wider than deep).
Anyone care to calculate the degree of rectangularity required at each point along the rod taking into account the varying MOE? Al?
…also what would the resulting rectangularity do to the stiffness in other planes e.g. across the corners? (Steve Dugmore)
In and earlier post this week, I calculated something like 8.8% wider at a butt cross section of about .320 inches. The amount of increase, unfortunately, is not uniform throughout the length. It has to vary form 8.8% increase at .320 to 0% increase where the rod becomes all power fibers, about 0.200, and square from there to the tip. If you pick a point half way between 0.320 and 0.200 (assuming a linear taper) that would be 0.260. The correction factor here is 5% not 4.4% so it’s not linear, but if you did use a linear reduction in correction percentage it would come out a lot closer that no correction at all. If I get the inclination, I’ll calculate the correction factor for any dimension and post it. (Al Baldauski)
Here’s a link to an Excel file that charts the side to side corrections necessary to get equal stiffness as back to back.
You can open it and/or save it.
In checking this Excel sheet for accuracy I found that the calculations are correct but that in a previous email I miscalculated the PERCENTAGE INCREASE incorrectly.
For a rod section of 0.300 front to back dimension, the side to side dimensions needs to be 0.348. That’s 16% (Al Baldauski)
Last week we were talking about directionality in PMQ rods. Some thought YES, some thought NO, and some didn’t care. I’d never built one so I was undecided.
Being the kinda guy who thinks a lot of things should have mathematical explanations, I calculated a correction factor chart to increase the width (side to side) of the butt sections to compensate for the calculated difference in stiffness due to the varying percentage of pith in any cross section smaller than 0.180.
So, I built a 60 inch section of PMQ as a straight taper 0.140 to 0.302 using my compensation chart to alter the side to side widths. This called for a side to side taper of 0.140 (no pith) to 0.350 (max pith). This, by the way, is not a straight line taper because of the way the pith depth varies and modifies the Moment of Inertia of the cross section.
I measured the deflection of the “corrected rod” in the front to back plane and the side to side plane. Within experimental error they were identical (28 ¼ inches) using a 16 oz to cause a large deflection to get better resolution of the difference, if any. So I asked, “Is this coincidence?”
I then planed the side to side thickness to the same dimensions as the front to back, just like “normal” for a PMQ, figuring there then would be stiffness difference if science is correct.
In trying to make deflection measurements with the 16 ounce weight the rod actually twisted so it would bend in the weakest plane! I then reduced the weight to 4 ounces which eliminated the twist at the same time reducing total deflection. However there was more than adequate deflection to resolve a difference in stiffness. The rod deflected 12 inches in the front to back plane while in the side to side plane it deflected 15 inches.
All of this proves several things:
1. There is a directionality in stiffness in a PMQ, front to back stiffer than side to side.
2. A PMQ can be compensated to eliminate the directionality.
3. The asymmetry in stiffness causes the rod to twist, likely throwing a line off plane.
The correction chart is available here. (Al Baldauski)
Thanks for going to the trouble of building and testing the theory and then sharing with us all. I love it when the empirical test confirms the math.
Your observation of the twisting of the section to follow the weakest plane also confirms why we spine a rod and put the guides on the weakest flat. (Rick Hodges)
I made my first two PMQ rods recently. Both rods had severe bows in both tip and butt sections. I was not successful in taking the bows out. Is this typical of two strip configurations? How do you guys remove the bow if you experience them. I use Titebond III and am afraid to use much more heat on them. (Dave Wallace)
As I recall, you have a vertical oven, so one thought off the top of my head is to hang a weight off the bottom of the rod parts. Second off the top is to make a sandwich with hardware cloth as the bread and your rod as the meat. Take a piece of the cloth and fold it with a straightedge, put the rod in the crease and close it up. (Dave Burley)