Vacuum bagging cardboard tubes; mandrel or no?

[RocketGeekInFL]

I am interested in glassing a couple of kits I got from Madcow. They are 4 inch rockets. I want to get the Easy Glass sock from Giant Leap to do the wrap and then wet it out with most likely West Systems. I am interested in adding strength as well as for aesthetic purposes.

I was once a professional chef and have many many laboratory grade kitchen appliances including a vacuum sealer. I have tried some poor mans glassing of tubes with a technique that uses panty hose, polycrylic and laminating resin that got the desired results without bagging but now I want something a bit more durable.

My question is this, would I need to use a mandrel in the tube if I am bagging it? If so, would a long FG coupler work? I don't have access to a 98mm motor, or I would just use that.

Thanks for any ideas.

 

[mpitfield]

I am just in the process of gearing up for this myself, sadly it is a couple years in the making. Same scenario 4" kits, one Madcow the other a Binder, one GLR glass sock the other the GLR Kevlar. Both will be under vacuum.

I decided to build a mandrel out of parts that I could reuse, so I purchased about 10 Madcow 4" cardboard couplers and have some AV bay ends to cap them off. As for necessary, I would say yes the tube is likely to at the very least deform if not held in shape with a mandrel of sorts, as for collapsing maybe maybe not, really don't know. This of course is mostly a guess on my part as I have only one experience to go on and it was a cardboard coupler cut in half and wrapped in one layer of CF then put under the same vacuum conditions that I will be using here. While it was under vacuum I felt that it could of easily deformed had it been much thinner and not supported.

I also believe the amount of vacuum you are planning on pulling is part of the decision. In my case I can adjust it and maintain it within 3Hg, and I normally pull up to 21Hg but sustain 18Hg.

Good luck and post some pics, at my rate you are likely going to get it done before me and I may pick up something from your experience.

 

[UhClem]

I use a variation of the kitchen vacuum bagging of John Coker. I make the bagging material more than twice as long as the tube and then push the extra inside the tube. Then when I pull a vacuum, the tube is pressed from the inside and out and is in no danger of collapsing.

I have bagged tail cones made from 1/64" ply using this method.

 

[mpitfield]

I use a variation of the kitchen vacuum bagging of John Coker. I make the bagging material more than twice as long as the tube and then push the extra inside the tube. Then when I pull a vacuum, the tube is pressed from the inside and out and is in no danger of collapsing.

I have bagged tail cones made from 1/64" ply using this method.

I thought of this method and tested it on a 54mm tube, but I found that the tube was too long and it was too finicky to deal with. How do you deal with the excess bag wrinkling as well as long tubes, what is the longest tube you have used this method on. Pics are always appreciated.

Thanks

 

[UhClem]

Sorry, no pictures other than of the finished product. (I am still mourning the demise of Kodachrome and really need to get one of these new fangled digital cameras.) It has been a few years since I did this but I have bagged 3' long 4" tubes and a 4' long 6" tube. Those are pretty close fits in the bagging material after you add the release layer and breather. So not much trouble with excess bag.

I think I did a 3' long 54mm tube once but that memory has faded away.

 

[dixontj93060]

I use a variation of the kitchen vacuum bagging of John Coker. I make the bagging material more than twice as long as the tube and then push the extra inside the tube. Then when I pull a vacuum, the tube is pressed from the inside and out and is in no danger of collapsing.

+1.

 

[raptor22]

This is slightly off topic, but my experience with vacuum bagging tubes has always resulted in a significant seam. You can avoid this by using heat shrink tubing instead of vacuum to compress the layup. Just an idea to keep in mind.

 

[Barkley]

This is slightly off topic, but my experience with vacuum bagging tubes has always resulted in a significant seam. You can avoid this by using heat shrink tubing instead of vacuum to compress the layup. Just an idea to keep in mind.

+1. That's the method I use.

Rather than glass over a cardboard tube, I'd just get a 4" mandrel and make the glass from scratch. The learning curve really isn't that steep.

 

[JohnCoker]

Larger tubes are easier to work with than smaller ones; a 6" tube is a lot easier than a 54mm one. Think of the flex in the materials (reinforcement, release breather, bag) compared to the circumference of the tube. That's why I suggest starting with a larger tube rather than a small one, which I know is counter-intuitive.

I've got to try heat shrink tape one of these days...

 

[REK]

+1. That's the method I use.

Rather than glass over a cardboard tube, I'd just get a 4" mandrel and make the glass from scratch. The learning curve really isn't that steep.

+100