CF Sleeves

[admin]

as seen on solarcomposites.com

http://www.solarcomposites.com/

so, having never worked with these, what's the deal? How much expansion can one expect over a mandrel's OD? Example: with a 1.5 inch mandrel, would I then buy a 1.5" sleeve? In a layup, would I then fit another 1.5 inch sleeve over the previous one? What about a third layer in the layup?

can I use these sleeves on an oblong form? an irregularly shaped form or one that goes into a complex curve with a gradual increase in OD?

I guess I am asking how much stretch do these things have? CF cloth is pretty pliable, so I reckon the sleeves are the same. So I guess it's the same resin techinque as cloth, wet out the mandrel, slide on the sleeve and wet out the exterior of the sleeve? Has anyone used the shrink-wrap technique that the website mentions?

do these sleeves have a seam? or are they a continuous cylindrical weave? how do they do that?

these are questions I have about sleeves. thank you.

[TexLex]

I could be wrong, and i would ask them, but i would buy bigger than you need. I tried it actual size and its a pain geting it expanded on the mandril and then the fibers were not straight. Then again, i might have done it wrong.

[Chad]

Most answers are on the Soller website- different sleeves have different "stretchability"- he lists diameter ranges for each sleeve. At the small end of a sleeve's range, he fibers are closer to aligned with the length axis (say +/-30 degrees), and at full expansion the fibers get close to perpendicular (say +/- 70 degrees). Unless you're engineering things to the nth degree, this probably won't matter.

A rule of thumb for most tubular structures is to divide the reinforcement 80/20 between uni and off-axis fibers, and try to keep the laminate balanced or symmetrical from inside to outside. If you can't do figures to design the laminate schedule, then copy the thickness of a known, successfully used aluminum section. The part will usually be a little stronger, and you'll save weight by the difference in density from the aluminum example to the carbon part. An example is a gnav strut- other similar boats use a 1.25" x 1/16" wall aluminum tube, so find a mandrel that's close and work out the laminate as 1/16" / .0018" of thickness per oz of cloth or fiber = 35 oz of fiber needed. I'd use a 6oz sleeve (can't get any thinner I don't think), 24 oz of uni (just tapes cut so their width roughly matches the circumference), followed by an outer layer of 6oz sleeve.

Small sleeves you can wet out on a table and then ooch over the mandrel, or wet it out in place with a brush. Tapes should definitely be done on a table, then after your last sleeve you need to aggressively "milk" the cover in each direction. It really helps if you've left a little extra sleeve at each end, so you can clamp it to something overhead and hang something heavy below. This will get you good consolidation, and you can probably use your gloved hands to also sort of squeegie a little excess resin out as well.

To get a nice finish takes either more coats later to fill the weave (and sleeves have deep weave), or a surface wrap of some sort to compress things a little. I haven't use the shrink tubular film, but I've used spiral wraps of shrink tape (pita, but for simple shapes -straight tubes- it works), or spiral wraps of strips of peel ply (less compression, but no shrinky wrinkles). For my tiller, I did only one coat of clear resin only, so it's not rough but still has a weave texture- it seemed appropriate for the task.

The sleeves will go on any convex surface, but work best the closer the section is to round or oval- you'll get no compression on flat sides, and they will bridge across any concavities.

They're braided like your socks. It's some kind of machine that does it. The fibers are continuous helixes, but they do go over and under each other like PW cloth.

Try some on a project- they're fun to play with!

[ryderp]

I've found these sleeves to be way easier to work with for any kind of shaft-like object than trying to wrap regular cloth around the object (no edges or loose fibers sticking to your gloves). As Chad mentions, round straight things are a natural for this format of material, but I've maid foil shaped objects as well including the spreaders and rudder that I mentioned on the other topic/thread. I've used different methods of forming objects from the sleeves from vacuum bagging, to compression with weights, and just wrapping the object in release cloth and letting it set. I think that for round shafts, as long as you're not trying to squeeze out every last ounce of epoxy for weight savings, that there is no need to vacuum bag the object. The sleeves themselves provide compression on the mandrel when you stretch them (like the toy finger traps).

Here is a picture of the first layer of carbon fiber sleeve on my rudder project. The rudder has a foam core from Flying Foam I then cut the foam core down its length and inserted a wood (marine plywood) spine. I molded the sleeve using compression from the foam cutouts from the foil. The next layers including unidirectional CF and more sleeves will be vacuum bagged.

First layer of CF on rudder.jpg

[admin]

Great stuff, thanks a million guys.

[Kevin]

I'd recommend against the "shrink tube". I used it one time and it did work sort of. Think about it for a sec. You use heat to shrink the tube. And the epoxy will set when it's heated. So it squeezes the tube until the exopy kicks off. For my tiller I used a besalt sleeve and then a carbon sleeve over it. The part is curved and slightly oval, light and plenty strong for the job. This is the part I used the tube on. In real life usage I've had not problem with the tillers strength.

I made a second tiller that I've decided against using. It's an oval foam core with 2 sleeves on it. I used the hand a weight on it technique with limited success. The biggest issue is the exposed weave that needs to be filled. I decided to scrap that part for a future use to be determined.

My gnav strut was made as Chad described. Inner cf sleeve, wraps of uni and then a outer sleeve. I hung this part and then wrapped it with strips of peel ply and this worked out well. I wouldn't call it a perfect cylinder but it will do the job nicely. This had a few extra bits added to the ends before it was laminated which made it much more challenging then a straight tube. I was happy that I wrapped it though. The smoother finished part was worth the effort and easier to finish.

Cheers, Kevin.

[Chad]

The heat hasn't been a problem for me in using heat-shrink tape. I find the heat liquifies the epoxy long before it begins to set. It can be used to "push" the liquified epoxy around, and with spiral wound tape a lot of it escapes through the overlaps.

[M&S]

Soller also has a carbon uni tube knitted with lycra so it can stretch around different size mandrels.
Has anyone considered using a windsurfer mast top section with some padding and reinforcement as a sprit pole?

[Kevin]

I did, I think I came to the conclusion with what I knew at the time that I would need a bob-stay and that it would be ok with the compression loads. I was going for simple retracting sprit without any other stays so decided to go with the c-tech tube which is way stronger than a windsurfer mast as best as I can tell.
Articulating setup with a bob-stay would probably work well with such a pole.

[Chad]

Soller also has a carbon uni tube knitted with lycra so it can stretch around different size mandrels.

It's easy to get uni to lie straight along a mandrel, at a quarter the cost. The uni sleeves solve a problem that doesn't really exist, IMO.

[Chad]

Articulating setup with a bob-stay would probably work well with such a pole.

that's my setup, so I used a 1.75" diameter pole from forte, which is a bit smaller than the ctech offering.