Used an aluminum pipe, but cannot for the life of me get it off. I figured cardboard is best, but don’t know of a good website to purchase.
Well, to there are a couple of ways.
- Use 3-5 mil mylar sheet as a release. That will make things wayyyy easier. remove mylar from the inside of the tube when done.
- If access to a lathe, you can always sand and polish aluminum mandrel till you have a glossy mirror surface and then add an release agent on top of that. cool down mandrel with something really cold like dry ice to get it off.
- make a slight taper in the mandrel for an easier time getting them off. Although most times that wouldnt be the best option.
hope that helps
Fantastic. I have tons of mylar. I never was too sure on how to use it, but thanks for clearing that up for me!
Aluminum tube with dry ice packed Inside and some ipa gets very cold
Liquid nitrogen does the trick…
Heating up the tube during cure does the trick.
We use aluminum pipe. It’s important to have a very, very smooth surface. We polish ours on a lathe with up to 1200 grit.
We then use Frekote mold sealer and release agent. 3-4 coats of sealer then 3-4 coats of release agent especially on a green aluminum pipe. Once a pipe has been used for several cycles, the tube practically slides off by itself.
I have been making plenty of tube lately. Polishing decent quality extruded aluminium or using dry ice to shrink mandrels might not be necessary. After speaking to Robert Renshaw at Rexco, I went with his advice, two or three coats of Rexco Hi temp release compound (wax) followed by one coat of Rexco PVA release coat. The wax is applied with a rag and then buffed up. The PVA can be brushed or rolled on. When dry, the PVA looks and behaves like a super thin layer of Saran food wrap. Depending on the diameter of the tube, it might be necessary to break the initial friction with mechanical force. I have been using a horizontally mounted arbor press. It takes a little ingenuity to figure out how to use the arbor press to do this, but basically you need to drill holes in the mandrel ends, and use a piece of rod as a couple, that allows you to pull the tube off.
In any event, if the wax and PVA coats are done well, I can remove the tubes with just hand force, but mechanical force is certainly helpful in initiating the removal. By the way, Robert Renshaw is one of the most knowledgeable persons I have ever spoken with. He knows his craft inside and out. I would highly recommend you speak to him.
It reminds me of the time where a friend made small (5 meter or so) masts, using an alu mandrel, and carbon prepreg. He used a large eye on the base of the (tapered) mandrel, hook the mast behind the doorframe, and use the car to tow the mandrel out. Works perfectly.
Except for that one time that the mandrel was stuck a bit, and the doorframe gave way…
Definitely something I could see myself doing.
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Our method has always been to have an aluminum collar that slips over our aluminum mandrel. We lay up onto this collar (we don’t mold release the collar) and then use it to hold the tube as we push it out with a hydraulic press. Collar is then trimmed off, and cleaned up to be reused again.