Tubes

General Composites Discussions Composites Talk
#32

Hi,

this is how I make my tubes. maybe it will help.

I place the outer layer down first on a glass plate and wet it out. The I add the next, wet it out, and so on. When I have it all layed down I slightly lift the leading edge and place an “L” shaped aluminum straight edge underneath with the long arm pointing to the edge of the carbon. Leave about 0.5 cm looking past the al piece. Place the mandrel on that and start rolling. As soon as the edge starts to go under pull the al part off and continue rolling without it. If I need a little more tension, I use the al part to clamp the carbon to the mandrel for each 1/4 turn. That way I can pull back on the mandrel while I roll. I’ll try and post some pictures when I make the next ones but that might be awhile.

Cheers
DB

#33

Great!
Lets see the pics when you have a chance
Terry

#34

Hey, how do you do your fins? VARTM, wet and bag, wet and press, etc?

#35

If you mean me and this picture, those are pairs of tubes woven around a mandrel. The idea is to increase torsional strength without going oversized or adding material. It’s wet layup in a vacuum. The single pair is for chainstays and seatstays. The double pair is a toptube. These particular ones had the vacuum fail but were still good enough for destructive testing.
The frame was not intended to look good. I wanted to test the principal. I ride it regularly and it is still holding up fine.

Cheers
DB

#36

Um. Fins, not tubes. I meant Tbone’s rocket fins.

ps: I like the aramid braid on the top tube. Looks nice!

#37

doesn’t anyone buy tubes? I’ve never made a tube. There is a winding factory nearby, and I don’t think I can make tubes as stiff, light, and cheap as they can in their mass production :slight_smile:
ok, they dont have the twill fabric look, wich is nice on homemade tubes :smiley:

#38

i had some from an old project awhile back. But no, you can’t make it as good as the professional tube makers do…but you can’t also PAY for them :slight_smile:

#39

I lay them up wet on either glass or aluminum . Then put a top piece on. Then put it under vacuum.

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#40

Have you played with foam cores at all? You would get a lighter fin. Of course, much of the design would involve knowing how much pressure they take, especially the leading edge.

#41

I rigged up a makeshift system to put tension on my tubes as I roll them,On the mandrel I Brush on some clear surface coat and let it get sticky.This allowed me to stick the material on without slipping. Then as I layed up the tube I just kept cranking up the tension. It worked real good and no problems.
Heres a couple pics. One of the tension device(look at the 2x4 on the left), and one of the tube I rolled using it.
This thread really help me, so thanks everyone for your input.

#42

Ive done a few fins using core material. The last fin was a fin that I built a frame out of solid carbon and the core was 1/16th in. styro sheet. The thickness of the fin ended up 1/8". This kind of work is the fun stuff.
I could start a whole new thread showing the experiments, messes, Ive made with fin material just like this tube thread LOL

#43

Not sure if you saw this site yet, but it has some nice ideas for composite rocket construction!!

http://www.jcrocket.com/nike-asp.shtml

#44

I missed the last few posts on this tread! I like the setup Tbone! Would you start using honeycomb at some point for your tubes? Not sure what size you are going up too, but I can see it might be useful for larger tubes.

#45

Ok, a short synopsis please? The easiest or best way to make 1" tubes? I would prefer to not have to bake them.

I also want to make some aero profile tubes using aluminum tubing available at an aircraft supply store. I’d like to get them about 2ft to 3ft in length. How would you release them from the mandrel?

#46

Sorry I havent been able to post in a while but Im back experimenting.
Im now trying to get the system down using heat shrink tape. I want the compression.So Im trying to adjust the tightness of my tape wrap and playing with different temps for shrinking the tape. so to not bite into the material too much.
Im thinking that after I do my layup , I could put downs a carbon or glass viel to do two things. Number one I would hope this would help the tape from putting to deep of ridges in the material itself. and number two this would act as a sanding viel. My hopes would be to sand the viel off and get rid of the ridges from the tape before I sand into the actual layup.
Could this work?
Thanks , Terry

#47

Yes, in a way the veil will help when sanding and not eat into the carbon fabric, as long as you are careful. However, the tape edge biting down on your material doesn’t seem right, unless you are not putting it on evenly. I don’t think the material is really being effected by the tape, so a veil to protect it from the tape would not be worth it. The ridges should only be resin flash lines. No way you can get rid of that without sanding, or coating in a surface coat.

#48

Aero profile, meaning like, oval/airfoil shaped? Anything not round is hard…you would need to get a hydraulic system to pull the composite off the mandrel. Unless you can cool the mandrel (freezer) and it should shrink enough to come out. Use tons of mold release!!! Make the surface almost mirror like, with NO dings/scrapes, etc…yes it’s the inside surface, but you would be pulling something along the scrape, and make it hard to do.

#49

The tape is biting in too much. Heres some pics.
By the time these lines are sanded out I am into the 1st layer carbon

#50

just my penny’s worth are the lines groves or ridges

if yor overlapping your tape and putting a lot of pressure into it it will press down on the edges giving you the grooves

if you butt the edges together the resin will seep through giving you a ridge

you could the go over the wrap with a second layer of tape over the butted joint

this wont get rid of the ridges but then as you have it set up on a manderal you could spin it in a lathe or something similar
and sand it with emery tape;)

#51

This sounds like its worth trying. Ill give it a shot.
Thanks