Ferrule strength Options

[DHayashida]

I have been experimenting with bamboo ferrules, and I’ve been finding that as weak as a bamboo ferrule would appear to be compared to a nickel silver ferrule, it doesn’t break. At this point I’m wondering how thin I can make the wall of a bamboo ferrule before it does break or split.

I am in the process of making a bamboo ferrule with 1/32 (.031 in.) wall thickness. It could be that the longitudinal fibers from the bamboo combined with the cross fibers from thread wrapped around in a matrix of epoxy will be all the strength needed for a ferrule. If the 1/32nd ferrule doesn’t break the next step is to make and test a bamboo ferrule with a 1/64th (.016 in.) wall thickness to see if that breaks. I think what is happening is the ferrule has a greater diameter than the rod at that point, and just like in car and bicycle frames, tubing with a greater diameter can be made with a thinner wall and still have the same strength. The key is to keep the tube (ferrule) from collapsing when it is bent. That should not happen since the male side is inside the female side, filling it up and keeping it from collapsing.

This brings me to wonder how much strength is really necessary for a ferrule. Ferrules are usually made with very strong materials, nickel silver, duronze, even titanium. I’ve been making aluminum ferrules for about four years with no failures yet even though the tensile and yield strengths are less than nickel silver, and bamboo can’t be even close to the same tensile and yield strengths of metal, yet it looks like bamboo will make a very good ferrule too.

Darryl

[adgaffney]

Darryl,

That's interesting. I'm in the process of making my first rod with a bamboo ferrule. I'm trying it out on a spinning rod for my father-in-law for Christmas. I was worried that my walls were too thin (.045), but maybe it will be okay. I just scraped the glue off the blanks and am waiting on some white silk before I wrap the female since I made the integrated kind of ferrule as described in PowerFibers.

How are you thicknessing your ferrules? I sanded mine down to .045, but am not really happy with my accuracy. It may not make a difference (I'll find out when I try to fit them) but I'd like to improve my tolerance the next time I try it.


Thanks,


Aaron

[darrellmyskiw]

I think (although I could be wrong) you might find (if you're inclined to look) that nickle-silver and titanium was chosen as they are more resistant to corrosion (chemical and mechanical). Aluminum corrodes fairly easily, and under moist conditions with a touch of alkaline - intergranular corrosion begins long before it's seen.
The normal signs of aluminum wear (black aluminum oxide) are fairly common for surface corrosion / wear. However, the intergranular attacks mostly show only when the blisters and powdery residue appear on the surface.
Even with a good anodic coating (about 0.0015" thick if you're lucky), the coating gets violated and corrosion eventually begins.
Titanium, nickle-silver alloys, duronze - although they do corrode, are more resistant to corrosion than aluminum. Also .... for some perverse reason - they are 'more exotic' metals that plain ole aluminum ..........

all my blithering aside ......

Your findings with the bamboo ferrules is quite interesting ......... makes me want to get my test pieces up and runnig into the lab faster.


darrell,

[Larry Swearingen]

Let's see, how thin can a ferrule be ?
How about a few layers of electrical tape on a spliced joint ?


Larry S

[DHayashida]

I am making separate sleeve type bamboo ferrules, not the swelled end ferrule.

I start with 6 bamboo strips longer than the approx. 3 inches I need for the ferrule to be able to handle them easier, i.e. clamp one end down and work on the last 3 inches to form the ferrule. I use a cabinet scraper (one of those flat rectangular metal scrapers) and scrape each 60 degree bamboo strip to the proper thickness.

When I glue the strips together I have to use a cotton swab to clean out the glue inside. When the glue is dried I use a razor saw (x-acto) to trim it to length. At this point I usually still have to clean out the inside with a flat needle file.

To harden the ferrule, I am soaking it in Minwax Wood Hardener.

Testing them is made easier since I am using hot melt glue to glue them onto a blank. I don't have to make a blank for each ferrule I test.

Darryl

[DHayashida]

[Mark Shamburg]

Darryl,

Very interesting. How are you testing the strength of the ferrules? Are you testing them to complete failure? If so what is the failure mode, ie are the ferrule delaminating, or cracking or breaking straight accross where the male section ends?

Mark

[darrellmyskiw]

Darryl - 4 yrs with the 6061, bare I assume (no coatings) .... not bad ......

I was thinking about this last nite some more - hmmmmssss ........... ohhh the directions and depths one could dive into ................. but I won't (for now)

[DHayashida]

[DHayashida]

[phg]

Any update on this? I'm getting interested in bamboo ferrules as an alternative. I was thinking .050" of power fibers, but you are way below that. Also have you looked into scarfing the ends of the blanks so the sheer force is not straight across? I noticed on some pictures of rods from the 1800's that, even with brass ferrules, they had angled cuts where rod fit together. Actually, a sliding brass band on a scarf joint would probably hold....

[Mark Shamburg]

Very cool idea about the brass rings over scarf joints. I will have to remember that one and give it a try this summer.

Mark

[LeeO]

Will glue up be an issue? You get them too thin and there isn't much surface to deal with. Are you using reinforcing wraps?

[phg]

Lee, I would assume that there would be reinforcing wraps. I really have found very little information on bamboo ferrules. There are a few rodmakers that use them, but they don't give much by way of details.

I am seeing several issues:
1) Moisture. 'Boo expands and contracts as it absorbs moisture from the air. This is not a desirable feature in a ferrule, though. That's probably why most sites advertise impregnated bamboo ferrules.
2) Wall thickness. It is understood that you would only want to use power fibers, but how thick is thick enough? I'm sure it would relate to the section thickness at the point where the ferrule is installed.
3) Glue. The ferrule has to be glued together as well as glued onto the rod.
4) Reinforcing wraps. I think a minimum of 3 wraps would be called for, one at the lip, one at the base and one over the point of greatest stress. I'm thinking this could be minimized by angling the the point of intersection to at least 60 degrees.
5) Length. How much overlap is needed in both directions?

Do we need to start up a bamboo ferrule project, similar to the PMQ project, to further the technology?

[phg]

...aah, I see there's another discussion down in the rod showcase section:
http://www.rodbuildingforum.com/index.php?...amp;#entry97526

It looks like Harry Boyd and LeeO are building bamboo ferrules.....