- This topic has 31 replies, 6 voices, and was last updated 19 years, 2 months ago by
Conway Stevens.
Conway Stevens.-
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denverdoc
I’ll be the first to admit that getting a perfectly seamless composite weave finish has so far eluded me. At LDRS I looked at some CF rockets that betrayed not a thread of overlap. Sort of like looking at the Mona Lisa and asking well now how did you do that? So how does one? My wraps always have a bleb or wrinkle and the seam so obvious you can park a car there…
John SWarren B. Musselman
Aerosleeve for the top layer… I’m doing it on my next 4″ project – an N4000 altitude attempt. Should be a year away.
Warren
denverdoc
Warren,
Did you say MD 4″ on N4000? Now that’s smoking. Jim Jarvis just flew one to where a kid on the 767 looks out the window, says, dad are we under attack?
JSConway Stevens
Actually John Getting the finish isnt all that hard. I work tons with Composites> Ive done Glass and CF and kevalr stuff of all sorts. There are some main keys as well as steps to take. First and foremost use a good epoxy. Like West or equivilent. Then be sure to get some sheet mylar. They sell it here in Ft collins on a roll. 48 inches wide x the foot long. Also I use a couple other relase agents as well one a spray the other a wax based paste. But What I do is lay my Mylar or the dpray release onto the mandrel and then I start winding the cloth. (lets say CF.) I wrap it a couple times and then start the wet down process. I use a plastic squeege and a Foam small roller brush as well as a rubber squeege. I roll the epoxy on and that helps penatrate it and then I use the plastic stiff sueege to move the epoxy around and then i finsh up with the rubber as it smooths and does not move the cloth creating wrikles and such. I then take the ends that overlap and pullthem gently outwards to straiten the fabric for any wrinkles on the ends. After im done with my wraps I take the flat mylar and wrap the tube in it and then using heat shrink wrap or even duct tape I make a compression bandage that spirals from top to bottom Or wrapped correctly to squeeze the tube. (be sure to have something on the floor. expoxy gets all over) I made an oven from a refrigerator box that I can hang the curing tubes in out in the sun. I leave them all day and bring them in later. They sit overnight and then next day I remove the mylar and the mandrel. Comes out silky smoth no seam and very little work left to do. I have many other things I do as well. Ive had the fortunate chance to play with lots of composites and paints and such. I to have plans for a MD powered brute on big power…
denverdoc
Con,
Interesting, I do most of what you suggest–except 2 wraps w/o wetting to get a good base. Gonna try that tomorrow on this little 29mm rocket. 🙂
The other issue I seem to struggle with is losing threads from the cut end, part of that is excessive handling..been meaning to set up some rollers. But even so, I seem to pull threads loose and I end up with this cheesy feathered seam, which for glass etc is fine, even desireable. But if you dont want to fill and paint, as in naked CF AF, unacceptable.
Now I like vacuum bagging as well–any tips there so when you start to pull a vacuum, the absorbent felt like material doesnt bunch up and impress wrinkles thru the peel ply?
John S
Conway Stevens
one suggestion on your loose threads would be to purposely go a little long on the fabric and tape with masking tape along the cut end and dont wet out the very end part of it. use shears or skissors and trim/cut a long strait line down the still dry fabric and take of the rest that is frayed and loose or taped edge. Then lay it down and use a foam paint roller to wet it out then wrap with the mylar nice and tight. Also I like to find a way to tie them up so they can hand by one end. allows all the excess to drip out. As far as bagging its just a experince thing that comes with time. You will develop a technic. but I like to lay it all down and pull on the outer parts of the tube where stuff sticks out and that will help with keeping wrinkles away. Just pull and roll pull and roll. (pull 1 section turn the tube. I have also devised a roticery that either by hand or via a small electric motor can rotate to help with some of the duty. Also I have found that setting up and curing will work but using some form of low heat oven (like my frig box I use) seems to make a better finish product. Just some suggestions anyhow.
Warren B. Musselman
I’ve been told it’s bad JuJu to heat West Systems up over 125 degrees to accelerate the cure. It gives off bubbles of hydrogen that cause pocking in the finish. Other epoxies are intended to be heat cured. I believe Aeropoxy is one.
Warren
Conway Stevens
Correct Thats why I use low temp oven for such need when using the west systems (this also makes a difference as to which hardener you use as I only use slow). Only need to be about 100 to 110 degrees. Comparing that to the Ac cooled temp of my house at 65 to 70 degrees is a fair amount. Now when making tubes for Minimum Diameter I use the Areopoxy I got at Shadow composites. The stuff is a high temp like 500+ degree epoxy and that we cure at a freinds place in his Custom oven good to 200-250 degree area.
Chris LaPanse
Aeropoxy is not a 500 degree epoxy, unless you have some stuff I am unfamiliar with. As far as I know, aeropoxy is only good to 200 degrees or so, which is still far better than west at around 120.
Warren B. Musselman
From my understanding, Aeropoxy makes 2 standard epoxies, one for bonding and one for composite layup… AND they make a high temp epoxy that does have a Tg of 500 degrees. It is only available in small premeasured containers and not in bulk cans.
Warren
denverdoc
Warren B. Musselman
Conway Stevens
Chris LaPanse
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