vacuum bag composites

Thanks for all the info guys, John they had a collspsable mandrel of some kind, I thought about buying the carbonfibre tube but WOW WOW what a price, so am looking into some way to make it as I probably don't need the percision that someone like Dragon Plate manufactures.

Initially I was looking at EMT conduit (cheap) but that failed as soon as I measured the percision of the round at various points NO GO. So next is to measure something like extruded 4130. If I could find something that would loosen in water but not let the epoxy bleed thru and bond to the tubing or saturate what ever I use and literally make it part of the carbon fibre tube, or like my first thought was wax paper but then I find in some informataion on laminates they specifically state not to use wax paper as it will dissolve the wax and it will bleed into the epoxy and contaminate it and ruin the mixture. So now I am thinking maybe just common brown wraping paper and paint it if the paint does not contaminate the epoxy. may have to choose a special paint of some kind.

Ed "at the moment" the HS is going to be in 2 pieces of styrofoam, 1 for the uper half and 1 for the lower half with this carbonfibre frame work routed in side, hard to explain and I don't know how to do a drawing and post it. Once all the router work is done for the frame and the control cables, the two pieces will temporarily be fastened together with those sharp toothpicks and tape and the hot wired to shape. Then seperated and everything will be put into place with micro slurry and and the two pieces bonded back together for the covering, don't know if it will be carbonfibre or glass.

Tony

PS I'm looking at round tubing around 1-1/8 inch and square tubing the same, I'm going for the extra strengh because of the twin rudders at ends.
 
I'm very interested in learning more by watching your build!

Humm, just remembered seeing a show on TV where they used a cardboard tube to make a rather large amateur rocket. They then throw it in a pool and let it soak and kind of twisted it out in wet globs.

Maybe brown paper would work with more than one wrap so the water could soak in like the cardboard tube but with the rod you could twist it off much easier than the rocket guys?
 
Hi John

Well things are moving along a little better, went back and measured a piece of 4130 that had not been used for something esle or cut out of a frame and found that a "new" peice measured within .001 of round and I can live with this for "true round" added 3 layers of brown wraping paper and the increased the diameter between .015 and .020, so that is about .010 per side and this will give enough space for water to seep in when it is soaked in a piece of 2 inch pvc pipe full of water, added the Saran Wrap and this is a bear of a job trying to keep out the wrinkles out of the Saran Wrap, but think this will protect the paper from saturation by the epoxy, may try something other than Saran Wrap later. Also do not know if the epoxy will interact with the Saran Wrap yet. Should end up with a carbonfibre tube of about 1 inch to 1 1/16 inch with .065 to .075 wall.

The big snag now is finding a source of "flat poly-tube" in quantities of less than a 1000 feet. Only need about 25 feet for experimenting. This is the stuff that they make those parts bags out of , it comes in a roll, you put the part in and heat seal one end roll off what you need (in my case about 7 or 8 feet and and wrap the other end around the vacuum hose and you got your vacum bag, leave about a foot at the bottom end for excess resin. The flat tube needs to be about 3 to 5 inches wide. Got any source recommendations. 1000 ft roll runs about $35 to $40 bucks, that's gonna be a lot of carbonfibre tube.

Tony
 
Tony let me ask my Nephew, he builds RC aircraft. IIRC He has some yellow material that they use as a shield/ separator with some absorbent material on the other side of that.
I'll find out where they get their material for you also.

I find this exciting. You are making your own tubing, how cool it that.

One day someone will build a gyroplane kit that looks sort of like a tinker toy. You know the connector on tinker toys.
All you would have to do is make the connectors is to bent them at the correct angle for the mast, etc. and plug in and bond the tubing!

It seems easy to me, expensive and light but then I've only watch them make tubing.
 
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Tony
Apply the 2 inch plastic packaging tape neatly all over the paper and wax it. Epoxy resin does not stick to this plastic at all and the tape will peal out with ease.
 
HEY DAVID !!!!!!!!!!

YOU JUST SOLVE 50% OF MY HEADACHE !!!!!!!!!!!!!!!

Thanks

Tony
 
Yep I use packing tape on small items but test it first some of the cheap stuff is not so good.

I know you are set on a round spar but wouldn't it be easier to make an "I" beam type of spar from composites? It would probably be easier to attach the skins too.
The flat surfaces will be easier to check for fit too, checking the bond surface and quality is going to be difficult on a round spar.
The round spar does have advantages too and would work great if you make a couple of composite ribs and attach them like they did in the AA5 wings.
 
:spy:A round steel or aluminum tube with a thick coat of wax and when done heat the piece and pull out the tube. The wax can be smoothed out easy and removed with hot water.:bored:
 
... my first thought was wax paper but then I find in some informataion on laminates they specifically state not to use wax paper as it will dissolve the wax and it will bleed into the epoxy and contaminate it and ruin the mixture. ...

I thought the epoxy you are using WAX contaminates it and was a NO, No?
 
John; The wax on wax paper is not the same as the car wax that should be used. Also hair spray is a good water soluble release agent.
Some epoxy has some wax in it to give a tack free finish. But it must be sanded off to lay up another layer.
 
Well it's drop back and re-group time. First I have found out that the "packing paper " is a really strong paper even when it is soaked but compressed by the plastic tape on the outside, you can get it off but not easily enough. So now I am going to try some type of paper that is more inclined to "come apart when wet, like "cheap" paper towels or news paper, more later. Thanks to everyone for all the info, as the say on the old radio shows , "keep those cards and letters coming in"

Tony
 
Hi Alan

probably a couple of light struts underneath, mainly for anti torque on the fuselage.

Tony
 
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Question On the wax,:wacko: Used to work at Gulfstream and Molds were reworked with:violin: puttys,Tooling:argue: waxes,:blabla:Mold release compounds :painkiller:even spraied pledge furniture polish.:rip:
 
At about 5 pm I had a problem with removing the 4130 steel tubing from my test set up. The idea of using the wraping paper as a barrier to provide a couple of thousandst clearance when soaked with water and let the steel manderal slide out of the carbonfibre tube when it was cured wasn't working. The packing paper was two tight, when it got soaked with water because the out side plastic tape that covered the paper to prevent the epoxy from bonding to the paper forced the paper to tighten against the steel tube. So I tried paper towels and it was a little better as the towel paper was a little more "mushy" when it got soaked , then I tried news paper , about the same, could not twist the steel tube loose or slide it out.

So i said to my self , self there is a problem some where. That is when I decided to pull my head out of the warm dark comfortable place where the sun does not bother your eyes and take a whole new look at the situation. After a couple of hours of thinking I decided maybe althought the steel tubing "felt" smooth and miced' round, maybe the tubing was not as smooth as it felt. The steel tubing has a "coating of some kind on it from the mill for rust protection. It looks like some kind of "oxide" finish and "FEELS " smooth, but I decided to take a chance and use some car wax on it. Must have put on at least 6 or 8 coats before it began to shine and I began to get some hope that this was the answer. The paper towels had given the best results so I decide to try these again with about 3 layers and then covered with 1 layer of the plastic packing tape. The paper towel material was wound snug and the tape put over the paper and snug then the test piece was place in the water and because of the paper towel being designed to soak up water, procedded to soak completely in just about 5 minutes.

THE STEEL TUBE SLID OUT WITH NO EFFORT!!!!!!!!!!!!!!!!!!!

Amazing what a little sunshine can do .

Tony
 
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hillberg, you nailed it

Tony
 
The test piece of 4130 was only about 8 inches long. After my discovery about the finish on the tubing I will polish the 6 foot piece to a mirror finish. If I were going to make very many of these I would even have it chromed. Sure is a lot to learn here about this stuff.

Tony
 
Tony,

I'm curious. While all this is very interesting stuff has any structural analysis been done on your tail design? Have you done any comparative analysis between the carbon fiber tube verses a more standard aluminum or steel tube?

.
 
Hi Alan

No no analysis has been done on the tail ,it really is a basic foam core sandwich type construction, with these tubular "spars" running from one side to the other to help with the twin tail load and also provide a place to install the short aluminum fittings inside the tubes which will be the attach points for the rudder mounting bolts. Interconnecting tubes (front to back) will have the fuselage attach points mounted to them . Then everything is imbedded in the foam core and the core will already have been hotwire shaped to a air foil and finally a cover of either fiberglass or carbone fibre.

Tony

PS. the HS is in two pieces , upper and lower
 
Carbon parts don't like metal fittings,:rant: it will corrode fast,need a stainless bushing or barrier between carbon and metal parts:noidea:.
 
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