What is carbon fiber tow and how to use? - RC Groups
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Mar 02, 2009, 09:24 PM
Physics hate's my ideas
GreenAce92's Avatar

What is carbon fiber tow and how to use?


how would i apply/use this? would this be sufficient enough for a CF spar? As in i would cut my cores, lay 1 or 2 layers per wing pannel and im good? i think for wings it would work fine and small dlg' reg style gliders. What do you guys think? How about if i layered a bunch around a pod like mold shape and made a pod out of this stuff?
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Mar 02, 2009, 10:18 PM
Registered User

Use this stuff mostly in linear applications, such as spar caps. It works extremely well in tension. Just glue it down with CA, or use a small amount of epoxy. Just remember: it is awfully easy to think of this stuff as "light", and then put all the weight and more back in as adhesive.

For pods and shaped articles, use cloth: fiber glass or even carbon cloth.

It will be strong, but balsa for pods is perfectly fine, strong enough and light enough, especially in your smaller, lighter airplanes.

Yours, Greg
Mar 02, 2009, 10:26 PM
Physics hate's my ideas
GreenAce92's Avatar
thanks alot!
Mar 03, 2009, 05:20 AM
Registered User

Ensure that the adhesive you use is compatible with your foam--some will eat/burn/melt foams!!

Anyone know if glass fibre rovings would do the same trick
Mar 03, 2009, 12:03 PM
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prodjx's Avatar
Ace please use gloves or a barrier cream cause your bound to get resin on your hand's. And to get all the benefit's of carbon tow use epoxy. Ive wrapped c/f tow 3 time's around wing cores, glassed over it with 2oz. and then waxed mylars put the foam beds over that and compressed the whole thing between shelving and clamp the whole thing together, and I'm getting ready to make another wing for the same friend for next year's flying.
Mar 03, 2009, 03:57 PM
Physics hate's my ideas
GreenAce92's Avatar
cool this stuff sounds great, ill wear the gloves for sure!
Mar 15, 2009, 04:25 PM
steelhead's Avatar
You can make a light weight, strong spar by gluing a piece of flattened tow to a wood spar. The Tow adds strength to the spar by not allowing the spar to bend as easily. The Carbon tow resists being pulled (STRETCHED), and the balsa locks it in place. When the wing has forces against it, it will not allow the spar to be flexed as easily.

Just remember to apply it where forces will be trying to stretch the Tow, not compress it.

Mar 15, 2009, 10:40 PM
Registered User
If you're gonna use it for spars, sand a shallow groove in the core 1st. Next mix up some epoxy in a dish. Then, with gloves, pull the carbon tow through the epoxy, and squeeze out excess between your fingers (yes, it's messy!).

Then lay it in the shallow groove and allow to cure. If any gaps left, fill with lightweight filler.

Top and bottom that will get rid of alot of your flex issues, but cores will still twist if you fly too fast (so don't...)

Splay the carbon out near the tip you throw with, and you'll also have something to glue your peg through. That way the forces are carried down the span better.

Have fun - you'll be cutting cores and bagging wings in no time!
Mar 16, 2009, 02:21 AM
Physics hate's my ideas
GreenAce92's Avatar
Originally Posted by camdyson
Have fun - you'll be cutting cores and bagging wings in no time!
I surely hope so! im tired of injesting foam, and having to sand and have my fingers feel like they have arthritis
Mar 16, 2009, 06:57 PM
jackerbes's Avatar
I just used a strip of 12K between the spar and the PB III FFF on a KFm2 wing. I folded the KFm2 strip back and marked it's location on the wing surface, then put a 1/4" wide bead of five minute epoxy along the line and laid the CF tow on to the epoxy. I spread it and worked it with a popsicle stick as I did that to sort of "wet" the tow.

Then I laid a 1/4" x 3/8" balsa strip on top of the tow and weighted that to get it flat and straight.

This was on a 42" wing with a dihedral brace (1" per tip) so I did one side at a time with a continuous piece of tow.

It set up very nice and stiff. I used that in place of what would have normally been a basswood spar and I think the balsa over CF tow combo is just as stiff or maybe even a little stiffer.

That was for the wing for Tony65x55's KFm winged Tuffy .

I also laminated a 3/8" square tail boom for the Tuffy from two strips of 3/16" x 3/8" balsa. Same method as described above with five minute epoxy. That finished up very nicely too. The tow adds very little thickness between the two balsa strips, maybe a couple of thousandths of an inch at most.

Nice stuff, that CF tow.

Last edited by jackerbes; Mar 16, 2009 at 10:33 PM.
Mar 16, 2009, 09:24 PM
Registered User
ozmo01's Avatar

carbon fiber

Carbon fiber is really strong in tension. Tow is loose fibers not twisted or braided kind of like unwaxed dental floss. CF tape is even thickness comes in many widthes and thickness and is a LOT easier to handle it is nice for gluing on to wood spars. Then there are preinpregnated spar caps that can even be bought pretapered. CF tow can be difficult to get a consistent thickness from but it is more compliant (pliable) for shaping.
Mar 17, 2009, 04:38 PM
Registered User
If you want to beef up your spars, laminated unidirectional carbon fiber is the stuff to use for spar caps. Carbon fiber tow is just loose roughly parallel threads of carbon fiber whereas the laminated strips are unidirectional carbon fiber bonded together with epoxy. CST and ACP carry laminated (and tapered) carbon fiber. These strips are very strong in compression along the fiber axis whereas carbon fiber tow has no such strength unless bonded to something else. Most wings fail by compression of the upper spar cap. That is where carbon fiber spar caps really help.
Mar 17, 2009, 04:59 PM
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Dennis Everett's Avatar
In the old days we would get some aluminum channel the size you wanted your spar cap to be , wax with mold release wax , wet out the tow , put in channel , add same size spruce , cover same size steel bar with wax paper , put on top of spruce , add lots of weights to steel bar , when done , you have a molded-like spar cap.....Dennis...now days much easier to buy sheet cf......
Mar 17, 2009, 10:49 PM
Registered User
The DL50 I'm chucking around at the moment just has carbon ROD (about 2mm from memory?) epoxied into grooves top and bottom, then all glassed in 3/4 oz cloth. Centre is reinforced with tapered carbon uni' tape.

I've given it some VERY keen throws with no sign of problems, so any more than that is probably overkill unless the section is unusually thin.


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