G/5 Epoxy

[Warren B. MusselmanModerator]

I should be out at the September launch – Oktoberfest most definitely. I’ll show you some of my v-bagged layups. I typically vacuum bag everything I do. My specialty is v-bagged tip-to-tip reinforced fin cans integral with the airframe. My L3 project, The uprOar project of a couple years back, John Wilke’s 30K plus North Site record flight, the bird John and Adrian flew at the July launch – all unitary, v-bagged layups. My L2 project 5 years ago was the first successful one and it landed without a chute (flat spin) from over 8000′ and bounced. No damage to the fins whatsoever and so far no problems up over Mach 3+.

Making plate is easy, even without a vacuum bagging system. Just add weight – a LOT of weight – evenly distributed across the layup. Tubing is a bit different and depends on your mandrel material. Steel, aluminum or solid wood are all easy to v-bag. However, v-bagging around a paper or phenolic mandrel requires some fancy setup work to prevent collapsing the tube.

My plate layup system also works with v-bagging, but I generally don’t bother. I have 2 laminated pieces of 3/4″ furniture plywood that consist of a layer of 3/4″ ply topped with another piece of 3/4″ 90 degrees offset and then further topped with a layer of oak hardwood flooring. These were run through a furniture planer and a industrial belt sander to provide a completely flat surface. I have 2 of these blocks. I do the layup on top of a piece of 1/4″ tempered glass with Mylar film between the glass and the layup, then top it with another piece of Mylar and another piece of 1/4″ tempered glass. The glass-Mylar-layup-Mylar-glass sandwich goes between the wooden blocks and the whole thing gets screwed together at the corners to preserve alignment and then I just park my pickup truck on top of it. I figured the compression weight on the layup is about 50psi. V-bagging gives you at most about 14psi unless it is done in a pressurized autoclave.

I haven’t done nose cones myself yet, but the technique is fully applicable to the standard parting-board method that Mick Kelly describes in the Composite Rockets Group on yahoo.

I have been known to teach classes in this technique. The key is pre-layup prep work, building the bag right and having enough hands to hold everything in it’s proper place while the vacuum is pulled.

Warren

[Steve JensenParticipant]

I wonder what the interest is in another class? I surely would like to participate, if one were available.

My main interest is in tip to tip reinforcing. I am also curious as to building carbon-fiber fin sets; though, machining/cutting them is a bitch.

Steve

[Chris LaPanse]

I’ve had decent luck cutting G10 and CF with a jigsaw and a tungsten carbide blade. A dremel with a diamond cutoff wheel works too, but it’s a lot harder to hold a straight edge with a dremel than it is with a jigsaw.

[greywolves]

Hey everyone,

The principle behind vacuum bagging is that of using atmospheric pressure as a tool. At sea level, one atmosphere weighs 14.7 psi (pounds per square inch) or 29.92 inches of mercury. In the absence of a vacuum, a surface has atmospheric pressure exerted on all sides and is equal. When a vacuum is generated on one side only, the result is an increase of pressure on the other side equal to the amount of vacuum being generated. A one square foot area is receiving 2,116.8 pounds of pressure with a 29.92″ Hg vacuum beneath it…

Since were in Colorado we can only achieve 25 Hg which equals 1768.71 pounds per square foot, I’d say its just a little heavier than the truck, its small truck, right? hehe 1768 x 4 wheels =7072lbs

I smashed a small metal can no problem when i was experimenting with a reservoir. I use glass now, Ball Aerospace canning jar which is really pointless, but makes me feel better, hate to ruin a free pump.

So yeah, gotta be careful how i word this, I’d love to see your rockets Warren. Yeah a class or watch you sometime working on your own stuff.

[Chris LaPanse]

Yep, although you don’t need anywhere near that level of vacuum to get decent compression. Even if you’re left with a couple of PSI on the vacuum side, you’ll still get quite a nice result.

(Oh, and it’s definitely impressive how much force vacuum can generate. I’m working in the physics labs at CU this summer, and one of the things I’m working with has to do with high vacuum. The chambers we use are thick stainless steel, and they weigh an enormous amount)

[Bruce R. Schaefer]

Well, that sucks, Chris…

[James Russell]

This is a little late but I have been using G5 for years and it is great. I will add filler at times to add strength and I have built complete rockets with it.

It does smell but not as bad as Bob Smith but I think works much better.

It is a little pricey but lasts a long time.

[Bruce R. Schaefer]

James, just ask Bob Smith to step outide. 😉

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