Firstly, if I could get cardboard tubes easily and cheaply, I'd probably use that. But I can't. I like Aluminum tubes because I can if necessary (potentially) use dry-ice, is readily available local product and It is fairly forgiving(strong).
Kirkside have recommended using TR 108 mold release , possibly in combination with PVA Mold release agent. Going to go for both...I want to give myself the BEST chance of it coming off. I suspect it will work without having to resort to dry ice which will be a great thing, because it takes up more time and isn't cheap. Yes, it will mean more Mandrel preparation, but, that is just what is required.
In my investigations, I think one of my BIG mistakes was letting the heat-gun keep the winding warm for about 4 hours post wind. This really sped up the curing and resulted in even tighter fit, sooner. Next tube I will ONLY heat for about 10 mins max, to extract excess Epoxy. After all, most of the excess epoxy removal occurs in the first 10 minutes when it still has the consistency of honey.
Hope to do a small 500mm test in 1 or 2 weeks time.
Will let you know how I go!!
Hopefully then I'll be closer to my next rocket Build!
I've got some TR-108 "wax" to apply to the Mandrel and I'm likely to try and use some Graphite as a lubricant. So - Aluminum Tube - sanded to 2000 grit - then Brasso - then cleaned with Metho and paper towels. - Then 8 layers of TR-108 - ~1hr between each application. - Then dusted with Graphite - Then Cash Register Tape - Then Packaging tape
.... and then I can do the actual winding!
Yes, a lot of things to do. Hopefully it pays off.
Hopefully in the next few days I'll have a 500mm long tube ...removed WITHOUT dry-ice...
Hi I finally got a chance to do another winding. Only a 500mm winding.... but just wanted to test removal from mandrel.
I :- - reduced tension in the filament, - used tr-108 wax on mandrel - Didn’t wrap docket paper around as tight (I could slide it before doing winding) - only ran heatgun for 10 mins - removed from mandrel 8hrs... rather than 12 hrs later
It was so easy to remove. Almost single handed and no dry ice. WOW! Such a massive contrast from before.
The surface finish has waves in it.... in some places...I didn’t apply tape as well as I should have. But I have an idea on how to fix that.
How long do you think the winding will take for a 2m tube? Also what is the pot life of the epoxy you are using? Do you mix it as you go and add more, or can you make the whole tube with the one batch of epoxy you mix up at the start? (Sorry if you already answered some of the questions earlier in the thread. )
Crop Circles: ... just a bunch of guys looking for their rockets ....
Previous tube of about 1.8m (that I couldn't remove) took 2 hours. So probably about 2hrs 15mins to roll a 2 meter Carbon Fiber tube - 4 layers.
The K3600 doc (from memory) says a pot time of 90min +/- 10min at 25 degrees, that number means nothing up here in Cairns where it is 30+ in the workshop. I measure out resin prior to the wind...then as required, I add hardener, stir for a minute and then add to the Resin bath. It is a fiddle, but it works. Another thing to remember is that a 2 meter tube requires about 700 grams of CF, so theoretically need 700 grams of Epoxy...way more than my bath can hold.
I have the whole procedure documented...and continue to refine it. It has some calcs that I perform to work out batch size and # of batches and I have everything measured out before I begin. All like clock work. Clean-up takes a while, but so far the Resin bath has been used for about 5 tubes so far of varying sizes.
As aside, I just realised the new Aluminum mandrel is 80mm diameter! not the 76.2 mm I ordered. Glad I picked that up early on!