# Stabilizers: carbon fiber versus thicker tubes of cheaper materials?



## nc514 (Jun 27, 2012)

You forgot to include the discombobulation factor in your arithmetic. After dividing the gross weight of a double sized shaft by a discombobulation factor .007, you'll quickly see that you have a discombobulated stabilizer.....but I'm not an engineer.


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## gma (Aug 22, 2012)

Great analysis! Based on your research, I'd say I'm even less of an engineer than you are, but a couple of things jump out.

First off, if you double the diameter of a tube (keeping same wall thickness), you'll increase the weight by roughly 3 (pi), not double. Not a big deal, as all the points you make are still valid.

Second - and this is based on opinion more than engineering or archery knowledge - I think you pretty quickly get to a point of diminishing returns once you're to a certain stiffness of the stabilizer rod, at least as pre-shot stabilization is concerned. The motions that are being asked to dampen are not of large force or size, making the demand for stiffness not extreme. Post-shot stabilization and vibration dampening might be another issue, but those are secondary purposes IMO.

Regarding weight, that can go both ways. A lot of people like more bow mass to aid in stabilization. Where that mass is located is of course important, but given that the majority is in the riser (the least effective location from a stabilization perspective), should give you some indication of how critical weight is. In other words, weight is a consideration, but not hyper critical. Unlike other sports (ie, cycling), I have yet to hear of an archery "weight-weeny." I have a feeling that will change, but for now, that is the case. Personally, I would love a super-lightweight bow with long stabs and all the mass out near the ends, but that's not for everyone.

In other words, yes, you can make a very effective stabilizer with aluminum or other materials. Currently and historically there are successful commercial examples of aluminum stabs.
Carbon is arguably a refinement, but it's also arguably more effective at meeting market demand than meeting market need (in this particular application).


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## arpruss (Aug 31, 2012)

gma said:


> First off, if you double the diameter of a tube (keeping same wall thickness), you'll increase the weight by roughly 3 (pi), not double. Not a big deal, as all the points you make are still valid.


Actually, it's double. The circumference is pi times the diameter.  If you double the diameter, you double the circumference, by doubling pi times the diameter. 



> Second - and this is based on opinion more than engineering or archery knowledge - I think you pretty quickly get to a point of diminishing returns once you're to a certain stiffness of the stabilizer rod, at least as pre-shot stabilization is concerned. The motions that are being asked to dampen are not of large force or size, making the demand for stiffness not extreme. Post-shot stabilization and vibration dampening might be another issue, but those are secondary purposes IMO.


Could be. Though when thinking about what sort of a stabilizer to make for myself (whether to order carbon fiber tube from dragon plate, or just use some steel tubing I had in an old broom, or maybe use some 1" diameter bamboo), I looked at some threads where people say that stiffness of stabilizer makes a significant difference to their accuracy.


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## gma (Aug 22, 2012)

arpruss said:


> Actually, it's double. The circumference is pi times the diameter. If you double the diameter, you double the circumference, by doubling pi times the diameter.


Oops. Quite right. Duh.:embara:

Let us know how it goes.


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## EPLC (May 21, 2002)

I think in theory your idea works, but don't forget that carbon tubes have pretty thin walls themselves. Trying to make steel or aluminum maintain the same weight as carbon by decreasing the wall thickness as you increase diameter would produce a very very thin walled stabilizer. I do not believe the end product would hold up.


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## Don Schultz (Jul 5, 2002)

DIY stuff is, by nature, going to adapt readily available materials. So parts I can find at Home Depot, or Lowes are the most attractive.

I'm more interested in building with 3/4" or maybe 1" PVC pipe filled w' Great Stuff foam and maybe a fiberglass and resin exterior layer on the pipe for additional stiffness.

One of my favorite ideas is to use a bundle of carbon arrow shafts painted with epoxy to form something light and very stiff, if kinda ugly. I've got a bunch of arrow shafts which are the wrong spine to use for this purpose.


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## arpruss (Aug 31, 2012)

EPLC said:


> I think in theory your idea works, but don't forget that carbon tubes have pretty thin walls themselves. Trying to make steel or aluminum maintain the same weight as carbon by decreasing the wall thickness as you increase diameter would produce a very very thin walled stabilizer. I do not believe the end product would hold up.


Would small dings disturb functionality?


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## arpruss (Aug 31, 2012)

Don Schultz said:


> DIY stuff is, by nature, going to adapt readily available materials. So parts I can find at Home Depot, or Lowes are the most attractive.


Well, I also enjoy making telescopes, so I'm used to doing things like ordering aluminum tubing from onlinemetals.com. But the best DIY projects are ones that can be done with stuff around the house, which is why I mentioned bamboo. 



> I'm more interested in building with 3/4" or maybe 1" PVC pipe filled w' Great Stuff foam and maybe a fiberglass and resin exterior layer on the pipe for additional stiffness.


PVC pipe is in my experience either flimsy (thin wall) or very heavy (thick well).

From my astronomy experience, 1/8"-1/4" wall cardboard tubing is surprisingly stiff, and very resilient with regard to dings. I expect it's great at damping vibration. I like to impregnate the tubing, inside and out, with two lavish brushings in of 1:1 water-diluted water-resistant wood glue (I use Titebond II, but III would probably be even better). For telescope use, people sometimes cut plywood rings to go over the ends, which greatly increases rigidity. For stabilizer use, you can just glue in wood dowel end plugs.


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## EPLC (May 21, 2002)

arpruss said:


> Would small dings disturb functionality?


Probably not...


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## Stinger3G (Jul 16, 2012)

arpruss said:


> I am both new to archery and a non-engineer. But I've been thinking. Based on searching the forums, the main point of using carbon fiber for stabilizers is stiffness and low beam weight. But can't one get the same with cheap easy to work steel or aluminum simply by increasing the diameter of the stabilizer tube?
> 
> Suppose we measure stiffness by deflection in an end-loaded cantilever. In a thin-wall tube, deflection will be inversely proportional to the Young's modulus, inversely proportional to the wall thickness, and inversely proportional to the cube of the tube diameter (because that's how the moment of inertia behaves).
> 
> ...


Wait till youve been shootig a while. You will accumulate a pile of damaged carbon fiber tubes, some of which will only be damaged at the end.


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## stringunnr (Sep 2, 2012)

nc514 said:


> You forgot to include the discombobulation factor in your arithmetic. After dividing the gross weight of a double sized shaft by a discombobulation factor .007, you'll quickly see that you have a discombobulated stabilizer.....but I'm not an engineer.
> 
> View attachment 1498648


Omfg....lmfao!


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## madarchery (May 28, 2003)

I thought you wanted the stabilizer to be weak? I guess I am behind the times but I thought the stabilizer was suppose to be the weakest "link" in the system and the part that absorbed the energy from the system in the form of movement/vibration. If its stiff doesnt this make the cam/axle area the weak link and source of vibration/noise.

Please correct me as i am always looking to learn.


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## arpruss (Aug 31, 2012)

Does anybody know how much high end recurve stabilizers weigh per inch of length?


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## dw'struth (Mar 14, 2008)

madarchery said:


> I thought you wanted the stabilizer to be weak? I guess I am behind the times but I thought the stabilizer was suppose to be the weakest "link" in the system and the part that absorbed the energy from the system in the form of movement/vibration. If its stiff doesnt this make the cam/axle area the weak link and source of vibration/noise.
> 
> Please correct me as i am always looking to learn.


That may be true if you are wanting dampening, but for true stabilization a stiff bar is the way to go.


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## Dan Zawacki (Apr 17, 2010)

The real point of diminishing returns comes when you begin to examine the wall thickness vs total weight - at what point are you risking a critical failure at the joint between the bow and the rod because the rod is no longer able to support its weight.

Also - how big a diameter rod would you have to make a steel tube stabilizer to equal the stiffness of the higher end carbon rods? I haven't actually done the math out (lazy, I know - you gave us all the relevant bits in the OP) but I don't exactly fancy a 3" diameter ultra thin steel tube running 30" from my bow.


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## arpruss (Aug 31, 2012)

Dan Zawacki said:


> The real point of diminishing returns comes when you begin to examine the wall thickness vs total weight - at what point are you risking a critical failure at the joint between the bow and the rod because the rod is no longer able to support its weight.


Tubes are very stable as long as you support the ends well. You could do this by well-fitted inserts which would spread the end load.



> Also - how big a diameter rod would you have to make a steel tube stabilizer to equal the stiffness of the higher end carbon rods?


At the same weight, the steel tube would need to be a little less than double the diameter of the carbon tube.

But this means that its wall would have to be around ten times thinner than the carbon tube's wall, since steel is five times more dense than carbon fiber. 

Hmm, put that way, it sure sounds like it might be too thin to withstand damage well, doesn't it? Anybody have data on carbon stabilizers and their wall thickness? I could figure out approximate wall thickness from weight and length and diameter data.

I wonder if steel rods arranged in a nice truss-like lattice around a central hole might not be even better than either carbon or tube. But that's hard for a DIY project.

I think I'm going to try 1" diameter bamboo first.


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## EPLC (May 21, 2002)

I just happened to have some high end carbon tubes that are .041 wall thickness. The OD is .707


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## arpruss (Aug 31, 2012)

EPLC said:


> I just happened to have some high end carbon tubes that are .041 wall thickness. The OD is .707


Well, I guess that's that for that idea. To match the stiffness in steel would require around .004 wall, OD 1.4. I don't think .004 wall would be practicable. With aluminum it's about .012 wall. Seems awfully thin to me.


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## EPLC (May 21, 2002)

arpruss said:


> Well, I guess that's that for that idea. To match the stiffness in steel would require around .004 wall, OD 1.4. I don't think .004 wall would be practicable. With aluminum it's about .012 wall. Seems awfully thin to me.


On the other hand I have 1 carbon tube that has a 5/8" OD and .012 wall that has held up quite well as a stabilizer... and that's a 12 ounce weight.


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## deepsprayj (Nov 4, 2011)

I dont see why a broomstick wouldnt work. I dont know how much weight it could handle on the end of it but i bet it is more than one would add to the end of a stab anyways. It would be ugly but it would work. I didnt see a whole lot of dampening effect with long rods on a recurve. The mass weight placed further out from the riser was the primary benefit through greater stability. I have seen som dampening on compounds using rubbery materials but it really isnt that much.

Shoot, work, shoot!


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## HOYTINIT (Aug 28, 2012)

It's all about what you want to spend...lots of old aluminum ones on ebay


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## opa (Jul 19, 2003)

Check out kite building materials: I've built stabs from pultruded carbon tubing, .750 OD, 0.540" ID, 32.5" long. Ideal for a target stab.
Very stiff and they also have fittings that may come in handy.

See: http://www.goodwinds.com/merch/list.shtml?cat=carbon.pultrudedcarbon

Opa


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## arpruss (Aug 31, 2012)

opa said:


> Check out kite building materials: I've built stabs from pultruded carbon tubing, .750 OD, 0.540" ID, 32.5" long. Ideal for a target stab.
> Very stiff and they also have fittings that may come in handy.


The fittings might be nice. But apart from that, I think .75 OD, .54 ID carbon fiber at $36 is a little less cost effective than aluminum: one can get a touch more stiffness at the same weight in aluminum using 1.5 OD, 0.058 wall aluminum, for $22 for three feet, and the aluminum will be very easy to work with.


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## OrangeBlood (Jan 12, 2009)

I am way to dumb for this thread....


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## Rick! (Aug 10, 2008)

If you never shoot outside, then the large diameter stuff has some merit. If you ever shoot in a crosswind, then the benefits of the smallest diameter stab with the highest stiffness are obvious. Plus, I think CF looks way cooler than Al or steel stabs. There are more places than dragonfire to buy small quantities of CF tubing. The pull-truded stuff is all one needs since bending is the only mode one needs to be concerned about.


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## arpruss (Aug 31, 2012)

In case anybody's curious about the weight of "nature's carbon fiber", i.e., bamboo, I just cut a nice 32" length of 1 1/8" thick bamboo, and it's 5.5 oz. That's about the weight of 32" carbon fiber stabilizers, but it'll go up a lot when the bolts and internal end supports are added. I plan to anchor the bow-end 5/16-24 bolt in a length of dowel which will be glued inside the bamboo with JB Weld. 

The weight end 1/4-20 bolt I am a bit less sure what to do with. One possibility is do the same thing. But another option, for some vibration suppression, would be to fill the outer end of the bamboo with E-6000 or Shoe Goo, and then have that hold the bolt in place. 

Question: How far should the 1/4-20 bolt for the weights stick out?

I am not sure what I want to do for weights. One possibility is to bolt on a fender washer, and then just stick hard drive magnets to it.


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## Fury90flier (Jun 27, 2012)

Thread length? I'd say 1/2" should be fine...need to have plenty inside the bamboo though, maybe 1.25"

Two of my stabilizers have the female threads on the end. One is about .5" of thread the other is drilled and threaded all the way through. May want to consider a long female 1/4-20 adapter...thinking like a turnbuckle nut...epoxy that in and you'll have plenty of thread.


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## arpruss (Aug 31, 2012)

OK, I made the attachment adapter on the bow side.

I am now wondering what weight I should put on the end. It's about 30 inches long, and I'm shooting a 66" 26# recurve. Any hints of what to make weights out of and how many ounces I should start with?


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## Fury90flier (Jun 27, 2012)

Maybe 2-4oz...

What I did on one of my bows was to get 2" flat steel washers from the hardware store...got a dozen of them (on a 10" rod). I added about 10 at first and shot for a week or two, then cut that in half and shot for another week...too light, so added a couple and shot another week or so.

What works for me won't necessarily work for you. Just get some weights and play with them. The washer idea is good because they're cheap. When you find the proper weight, weigh it and buy the proper weight.


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## arpruss (Aug 31, 2012)

I found a couple of inches 1.25" ID 1/8" wall aluminum tubing that I was saving for making a telescope focuser that nicely fit over the end of the bamboo after I wrapped the end with drawer liner. That was 4 oz. A bit too heavy--I found the load on the bow arm bothersome. But stability was good, and vibration suppression (thanks the drawer liner?) was great. I also tried without the weight and then without the stabilizer. It was striking how much louder the bow was without the stabilizer, though it also had a pleasant light feeling. 

Anyway, I'll experiment some more with the weight (maybe I'll buy a piece of steel pipe), but the lesson so far is that 1.1" bamboo seems quite a decent material for stabilizers.

I don't really want to measure rigidity, as I don't want to break the bamboo. I did tap the stabilizer to see how the system vibrated. When I held the bow in hand and tapped the stabilizer, there was some very visible low frequency (maybe 2-8 Hz?) vibration. When I held the riser tight to a solid piece of furniture, almost all of that vibration disappeared, so the vibration was of the system as a whole rather than of the stabilizer itself.


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## arpruss (Aug 31, 2012)

I posted all of my build details here.


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