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Form Setup - Swelled Butt Setup

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I used large, internal hex head bolts with a large smooth shaft and threads only at the very end like the ones on Thomas Penrose's page to build my forms (actually I built my first forms from the plans on his awesome page). The reason I mention the bolts is that is the only modification I made and because some of you out there use Garrison style forms (push-pull bolts all on one side) and other inventions, I don't know if this method will help you guys or not.

The first thing I did was take my bolts for the first 4 or so stations on the butt ends and I ground a relief groove in them, the reason for this is that as you spread your forms the bamboo strip will eventually bottom out on the bolts; the groove in the bolt gives you that little extra space you need. This may take several attempts before you get a deep enough groove (determined by how gutsy you are and your taper) in the right spot (center of forms for the given width).

The next thing to do is get some shims to put in by your pull bolts (These will take the high stress of your small push bolts), they must not stick up far enough to hold up the strip.  Set them in up to the last station aft of the swell, now tighten down the bolts ahead of the swell, this includes the station just ahead of your last shim.  You may have to use a LARGE C clamp to help you with this bolt. Now tighten down the last couple bolts behind the swell, you will definitely require the aid of your LARGE C clamp/vise/friend.  Keep in mind that behind the sell will be turned down after to accommodate a reel seat and grip anyway.

Remember to split your strips larger than normal!!! The swell gobbles up allot of bamboo.

PLEASE NOTE: Don't try this if you are worried about your forms, I don't want to be responsible for someone ruining their $800 forms and saying "Shawn told me to do this".  I would feel terrible! All I can say is that MY forms held up fine, but mine are home made and are very strong. I was desperate to try swelled butt rods and this was feasible to me. Your swell is limited only by your courage and design of your forms. I've pushed mine quite far and I was happy with the results. The other option would be to build a short swell form.

The swelled butt rods I have built are light (or FEEL very light) and are fast action rods, although not everyone likes the action. Unfortunately any pictures I had of my swells were lost when my computer dumped. The Thomas And Thomas tapers are very extreme swells and may be a bit too much for your forms. The FE Thomas 7' 3 wt that Reed posted a while ago or any of the swelled FE Thomas rods) work nicely for a first attempt or the milder Grangers, Heddons and I believe some of the Dickersons have tiny swells which may be a better starting point as they are less acute and smaller. I believe Danny Twang modified a Sir D to have a swell??  You could experiment with Hexrod and existing tapers. Good Luck!  (Shawn Pineo)

After talking with Shawn about this he stated the following:  "People need to realize there is a potential to bend your forms if they push them too far!"


The Problem:

I was setting up my final forms for the butt section of a rod when I discovered something very disturbing.  There is a swell in the butt that goes from .131" (1/2 d) to .165" (1/2 d).  It remains at .165" for the remaining  three stations (four total at this dimension).  The problem is that between these stations the dimensions are NOT at .165".  In fact, between the first of these (starting tip side) and the second, it goes up to .169".  Between the second and third it DROPS to about .162".  Between the third and fourth the variation is negligible (less than .001").  I do not have super precision measuring tools, but this variation goes way beyond that.  In fact I only checked because it looked funny in the groove.

The Info:

My forms are cold rolled steel with dowels at every other 5" push/pull station.  When fully closed the slope per inch is .001".  I just closed them up and checked this, so that does not appear to be the problem.  For the record, I did try opening and resetting the forms and closing and resetting the forms and the variance basically remained the same.  I just thought of it now, but I have not calculated and checked the slope between other, tapered stations to see if these are also off.

The Plea:

Has anybody else experienced this problem?  Anybody might know why this is and what I can do about it?  (Carl DiNardo)

    All you can do to correct this is to either sand or file either the top or the meeting sides of the forms. If the other side is fine, then dress the butt side until you get it right, if both sides are off, then take the forms apart, turn them so the groove side is up on both bars and dress them both at the same time. This is a better way to do it if the tops of the forms are flat and move correctly when you set a taper, I would work on the edges even if I had to go back and re-cut part of the tip side afterwards.  (John Channer)

    Is it possible that the process of adjusting one station forced the others to move a little bit?  I usually go over each station a minimum of twice, usually three times, till things stabilize.

    First thing I would do is close the forms and check them every inch.  Obviously with the forms closed the groove should change .001" per inch.  If they are off when closed, then you know you have a problem with the forms.  If they are new, then you might consider calling the maker and see what he says about the problem.  If they are homemade, then you'll need to start thinking about some of the remedies John suggests.   (Harry Boyd)

      I guess I did skip right to the worst case scenario.  (John Channer)

        Thanks for the reply.  First of all these are purchased forms.  They are new and I have not tried using them until now, but I purchased them this past spring.  Here is what I have done.

        I first calibrated my indicator with my dial calipers (neither of these is of the expensive variety).  Then I checked my forms using Chris' Drill rod method (I had to use bits, but I tried 3 different bits at one station, and everything checked out OK there, so I am fairly certain that my groove is 60*).  After that I closed up my forms and marked them every 1" on the butt side starting at the first station on the tip end.  Then I measured and recorded the measurements at every mark.  What I found was that  most of the  measurements were  OK (.001" increase for every 1" of travel).  However, between each station there was usually a jump of about .002" at about the third or fourth inch of travel between stations.  My first measurement (first station) was .084 and my last measurement (3 inches beyond the last station, but over an independent shoulder bolt at the end of the forms) was .151"  The total distance between the first and last measurements was 58."  If I remember my simple trig correctly this means that the average slope per inch is equal to  .001155"   or about .0012".  I have not yet done this on the tip side.


        To me that seems to be off a substantial amount, but as some have pointed out they are adjustable.  Chris Bogart recommended that I insert dowels at every station instead of every other station (by the way the dowels are in between the push/pull bolts) to increase stability.  All of this (with the possible exception of the dowels) doesn't seem to explain the original problem I was having between stations.  Or maybe it does and I just don't see it (my specialty is turf grass science, not engineering).

        I guess what I need to know is whether or not my forms are off enough to worry about, is this aggravating my problems, and what can I do about it.  I would rather not "fudge it", start planing and hope for the best.  I absolutely agree that doweling every station is a good idea, but I may want to speak to the maker before drilling.

        If I am missing something obvious, please don't be afraid to hit me over the head with it.  I need another cup of coffee.  (Carl DiNardo)

          After that I closed up my forms and marked them every 1" on the butt side starting at the first station on the tip end.  Then I measured and recorded the measurements at every mark.  What I found was that most of the measurements were OK (.001" increase for every 1" of travel).  However, between each station there was usually a jump of about .002" at about the third or fourth inch of travel between stations.

          I haven't seen any tapers that I had to close the forms tight to set them for the rod  I was making. The groove on mine was cut while the bars were spread, and that's how they are set for planing. I cut my grooves .025-.085 on the tip side and .080-.140 on the butt side. Try spreading the forms a little bit and see if that changes the amount of slope between measuring stations. Set them .005 or .010 deeper than the closed dimensions are supposed to be. Also check the bars for straightness.

          (by the way the dowels are in between the push/pull bolts)

          Sounds like this puts quite of bit of space between the push/pull bolts. Try less torque on the bolts when you set them (spread apart), and see if that changes anything.  (David Dziadosz)

            I have been getting a lot of great feedback on the forms and I thank everyone that is helping me.  Someone on the list sent this to me off list, and it seems plausible to me.  I was wondering what other people with more background in stresses than myself think of this.

            ....."I've come into this discussion a bit late but if I am reading your first post correctly then your forms are doing exactly what you would expect.  Normally the gap you set between stations is quite small say 5 to 10 thou and the changes of taper are even smaller so the forms adopt a shallow curve between stations and the effect beyond each station is small. When you get to your swell you are forcing over 30 thou change over 5 inches and then at the next station setting the same measurement, its natural therefore that between the two supposedly equal stations the gap will actually be wider and because you have pulled this curve back in the next point between stations will be smaller.".....

            My forms are cold rolled, so this may be more prevalent than in other forms. This seems like exactly what I am seeing.  Again, as Chris has said, I think dowels at every station would improve the stabilization of the forms.

            Also I seemed to have caused some confusion with regard to the dowels:  the pins are between the push bolts and the pull bolts at every other station, not between stations.

            Thanks a ton.  Keep it coming if ya still got it, as an explanation is wonderful, but a solution would be even better!!!  (Carl DiNardo)

    I know that we have had quite a discussion regarding the depth of the groove, and I have followed the thread, but over the last few years, I have experienced a strange problem with my strips and finished tips that has go me thinking. 

    A while ago, I noticed a curve in the tip section of my rod.  This curve was fist noticed in the tips strips after final planing.  It is not there in the rough strips, nor in the beveled strips.  I know this as I use my tips to set up my butt taper.  It only appears in the tips.  It appears in the strips and then in the rod, once the rod is glued.

    After struggling with this issue on a number of rods, and the last discussion about the forms, it dawned on my that it might be my forms.  The curve always appears in the final 25" of each strip and is also present after gluing.  I can remove the curve with heat.  After much inspection, I have noticed that the 60* groove is off about 7.5 inches from the end of the tip side of the form.  I can see an imperfection in the groove. It almost looks like one side of the forms at this location has a different depth than the other side.  So that when planing, I am pushing one side of the strip into this area with a greater depth, creating a triangular strip that appears rotated.

    It would appear that this imperfection in the form, strip and tip sections appears for an inch or so.  I have concluded (hopefully correctly) that this would result in a rotation of the equilateral 60 degree strip and would then result in the curve.  Its almost like there is a twist in the strip as a result of this imperfection.  In order to correct it, I have to undo the twist, by putting another twist into it at this location.

    This is the bigger issue, but there is still some curve in the finished tip section and strip below this point. 

    As I followed the previous discussion regarding the issue of an imperfect form, I closed the form and began to slide the depth gauge along the closed forms and discovered all kinds of inconsistent numbers.  There is no consistency in the groove as I get to about 25" from the tip.  If my understanding of the math for the groove is correct, the groove should have a consistent slope along the length of the forms, dropping by a certain amount from station to station.  If for instance, I have a slope of .005" in my forms, with a depth of .040" at the 5" station than the 0 station should have a depth of .035".  Is my reasoning correct?  The numbers appear to be okay for about 2/3rds of the form, but as I get towards the tip, the numbers begin to vary.

    I am in the process of measuring the forms at 1' intervals to see exactly how much my groove might be off by.

    Is there anybody else who has experience similar problems and if so how did you correct them?  (Mark Babiy)

      First of all, I would suggest you correct your form where the bottom of the groove is of unequal depth. Close the form and mark any locations where groove is not of equal depth. With a 3-corner 60° file work these areas back into line. When done, measure & record the depth at each station with the forms closed.

      I enter these dimensions in a Excel Program (get it here) and it tells me how to set the forms, shows a graph and tells you if any milling will be necessary. If you, or anyone else for that matter, want a copy, let me know.

      To me,  the slope of the groove must be consistent especially between stations and ideally the whole length of the form. When building forms my target is .001"/inch slope from end to end, why  settle for anything less?  (Don Schneider)

        Thanks for the idea.  I am going to measure the depth at 1 inch increments an that would be a start.  I might as well figure out how much I am off.  This way, maybe I can take care of the slight scallop where my 60 degree groove appears to be off.  (Mark Babiy)

    I have played with my forms some more and determined that my problem is indeed the stresses caused by such a severe swell in the butt section.  I am planning on adding extra dowels in the future, and if this helps I can pass on that information.  For now I am just spreading the swell over 10 inches instead of the 5 called for in order to relieve some stress.  If anyone has questions about what I discovered based on Gary Marshall's interpretation of what was actually happening, I will be more than happy to share, but I have used enough bandwidth for now.  (Carl DiNardo)

      Though I'm not the accomplished rodmaker that many here are, here is how I understand forms from an engineering standpoint.  The primary purpose of the dowels is to maintain alignment of the forms.  So adding dowels won't likely help your particular problem.  Instead, have you considered drilling  and tapping  to add  an intermediate pull-bolt between the stations that are bowing outward.  My guess is adding one, maybe two of these will solve your problem.  Plus, drilling the thru-hole and tapping the opposite won't require nearly as precise a tolerance as trying to get the dowel holes straight.  (Tim Preusch)

        You're not off base.  The forms from Colorado Bootstrap are done this way.  In the area where a swelled butt would be planed has push/pull  stations 2 1/2 inches apart.  (Roger Fairfield)


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