Vaccum bag connectors

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The problem you are having is that you are using a pressure quick disconnect not a vacuum quick disconnect. Those fittings are not made to seal in vacuum. They will pull air and kill you pump quick.

The airtech one above is vacuum rated we use them on our autoclaves and pretty much every where else you need a bag passthrough.

While it may be the case that the connectors I used are not designed for vacuum, I have a ball valve after the connector and if I shut it off there is no loss of vacuum. So in this case the quick connect is not part of the problem, however I do appreciate the insight on the topic.
 
I thought I would share a couple of pics of the layup that I am in the process of completing. This is a three part carbon fiber T2T layup using a single layer of 3K 2x2 twill with Aeropoxy PR2032 and the PH3660 hardener, because I like the extra layup time. I am two fins in out of the three. These will be painted, and once complete you will never know there is a T2T reinforcement.



 
wwwooohhhhhh,,,
Is that a sexy curve man...
Geezzz you do some beautiful work Michael...
I have to buy some carbon and didn't know what weight to buy...
The offerings I saw were 6 oz. I think..
I'd guess when guy's do 3 layers they use very light carbon
and when their doing 1 layer it's a much heavier carbon.....

Teddy

Hey Michael,,,
How r u planning on loosing that forward edge ???
 
wwwooohhhhhh,,,
Is that a sexy curve man...
Geezzz you do some beautiful work Michael...
I have to buy some carbon and didn't know what weight to buy...
The offerings I saw were 6 oz. I think..
I'd guess when guy's do 3 layers they use very light carbon
and when their doing 1 layer it's a much heavier carbon.....

Teddy

Hey Michael,,,
How r u planning on loosing that forward edge ???

Hey Teddy, I am no expert on CF cloth, however I am pretty good at doing a Google :wink: From my previous conversations with TRFers and through Google, the most common cloth used is the 2x2 twill, however which cloth you use is very much based on what you are trying to achieve. Up to this point all of the cloth I have used is the 2x2 twill exclusively but my needs up to now have been to add some marginal strength and give it a finished look.

The fabric I use is 5.7 oz/sq yd, 50" wide, 0.012" thick, 3K, 2x2 twill, and a single layer is very thin when compressed under vacuum. With the layup I am doing right now, the cloth weighs about 7 grams before being trimmed and I have yet to do my final weight but after trimming it will likely add about 4-5 grams per layup. That is just the cloth and the epoxy would be added to that. To mix the epoxy I usually start with about a 1:1 ratio rounded up. So if the cloth is 7 grams I mix up about 8 grams of resin.

I also use a nylon peel ply and when under vacuum a lot of the resin is transferred to the peel ply and breather, leaving a very thin layup behind. It is really quite amazing with just one layer if you tap the fins, pre-layup, and hear how they resonate and vibrate, then post-layup you do the same tap and the fins feel so much more significant. When I have completed this layup I will do a final weigh in and let you know the net weight gain, but I am guessing 25-30 grams

As for the forward edge, this is just a 38mm MD and not likely to get too far into the higher velocities where heat would be an issue. My plan is simply to block sand them by hand to get a nice edge then paint it with regular automotive paint and my HVLP. No ablative no high temp epoxy just paint.

They guys who do three layers are likely going for strength because they are planning something in the higher velocities or longer sustained velocities, and from what I have seen they have used combinations of fabrics like unidirectional layered in opposing patterns or the twill or a combination of both, with the twill on the top as the finishing cloth. Again it comes down to what you are trying to achieve. In my case this has mostly been practice and to add some marginal strength as I have two high Mach builds on the table which will require more thought and actual calculations to determine what cloth I use, the pattern the number of layers, the resin, room temp cured or in a heat box, etc.
 
I love the way you do your homework,,,
You think things through so thoroughly...
You know I do as well,,
and yet I still find that I'd do things differently the second time around,,, lol...

I guess that's what they call experience...

Teddy
 
I love the way you do your homework,,,
You think things through so thoroughly...
You know I do as well,,
and yet I still find that I'd do things differently the second time around,,, lol...

I guess that's what they call experience...

Teddy

Ah that is precisely why I do these "overkill" layups, which is what some like to jump on me for. Bottom line, when I really need to do it right I will have a couple of dozen T2T layups under my belt and hopefully that translates into better results. I have refined my approach with each layup, Jim Jarvis has also been a tremendous resource on this topic and I appreciate his attention to detail.

I plan on building a heat box and trying my hand at pre-preg this summer.
 
I'm planning on doing something as well...
When I get around to this build and get to the point where I'm going to do the lay up,,
I'm going to drive all the way to Canada and kidnap you.... lol..

Teddy
 
Ah that is precisely why I do these "overkill" layups, which is what some like to jump on me for. Bottom line, when I really need to do it right I will have a couple of dozen T2T layups under my belt and hopefully that translates into better results. I have refined my approach with each layup, Jim Jarvis has also been a tremendous resource on this topic and I appreciate his attention to detail.

I plan on building a heat box and trying my hand at pre-preg this summer.

It looks like a lot of work but man o' man that can will be able to take whatever you launch it with!!:wink: Kurt
 
Ah that is precisely why I do these "overkill" layups, which is what some like to jump on me for. Bottom line, when I really need to do it right I will have a couple of dozen T2T layups under my belt and hopefully that translates into better results.

One of the reasons I need to do one or two of these some day.
 
Ah that is precisely why I do these "overkill" layups, which is what some like to jump on me for. Bottom line, when I really need to do it right I will have a couple of dozen T2T layups under my belt and hopefully that translates into better results. I have refined my approach with each layup, Jim Jarvis has also been a tremendous resource on this topic and I appreciate his attention to detail.

I plan on building a heat box and trying my hand at pre-preg this summer.

this is high power rocketry, isn't that "overkill" by definition? Very nice work as always!
 
Maybe I missed it somewhere, but was a good vacuum bag connector mentioned? I am going to order one soon, and am still not 100% sure what the good buy is...
 
Thank you. I read the thread through, but missed a clear winner. Thinking on trying this connector, but am also considering this one: https://www.easycomposites.co.uk/#!...ps-and-equipment/through-bag-connector_2.html

I considered that as well as many other, what appear to be higher quality connectors in the UK but I ended up purchasing the Airtech high temp connector https://www.acpsales.com/High-Temp-Vacuum-Connector.html simply because I wanted something a bit more local. I just came home this evening to find the delivery notification for the new connector so hopefully tomorrow evening I will pick it up and get a chance to use it in the next couple of days. If so I will post back my experience, albeit it will be limited...but first impressions.
 
I received my Airtech high temp connector today. Although I have not used it, I thought I would post first impressions and do a side by side with my old connector. I will be doing my final 3rd layup on the same rocket I posted above, tomorrow, and will post my results.











Visually there is an obvious difference in the quality of manufacturing right from the design, workmanship, to the materials used. From a design perspective the original one is a two piece with the sealing gasket attached to the top piece and when you connect the top and bottom piece you turn the two pieces until tight. The new connector is a three piece connector and the gasket is connected to the bottom, then a washer and the collar screws down. My take on this is that although new connector is three pieces, which is arguably one more piece to leak, I believe it is a better design. I see an advantage with the new design when connecting it to the bag as it is less likely to wrinkle the bag, which is something that has happened.

The connector on the new one is designed for vacuum, with a built in check valve and the old was is designed for pressure. Although I have never had a leak with the old connector, having a choice I would rather have the one that is designed for the job. Whether this translates into any advantage remains to be seen.
 
I have been using the ACP EZ-Vac connector for decades with no issues. I like it because it is small and light. Make a hole punch from brass tubing to get a good clean hole and make sure the bag doesn't wrinkle.

To cut down on pump cycling, in our fab shop we made a vacuum chamber out of a piece of PVC 6" tubing. It takes a little longer to draw down the chamber and parts, but the pump might cycle once every couple hours.
 
To cut down on pump cycling, in our fab shop we made a vacuum chamber out of a piece of PVC 6" tubing. It takes a little longer to draw down the chamber and parts, but the pump might cycle once every couple hours.

Could you post pictures and/or more detail on your vacuum chamber setup?
 
I have been using the ACP EZ-Vac connector for decades with no issues. I like it because it is small and light. Make a hole punch from brass tubing to get a good clean hole and make sure the bag doesn't wrinkle.

To cut down on pump cycling, in our fab shop we made a vacuum chamber out of a piece of PVC 6" tubing. It takes a little longer to draw down the chamber and parts, but the pump might cycle once every couple hours.

Nice, I was thinking of using 6" PVC to make a catch pot literally today. Is it schedule 40 or 80 you used? And just the normal PVC endcaps on that?

Thanks for the review of the connector mpitfield... will be looking to see how actually using it goes for you!
 
To cut down on pump cycling, in our fab shop we made a vacuum chamber out of a piece of PVC 6" tubing. It takes a little longer to draw down the chamber and parts, but the pump might cycle once every couple hours.

Nice, I was thinking of using 6" PVC to make a catch pot literally today. Is it schedule 40 or 80 you used? And just the normal PVC endcaps on that?

Thanks for the review of the connector mpitfield... will be looking to see how actually using it goes for you!

I actually have a vacuum chamber, well it is a bit more involved than just a chamber but it is well thought out and more importantly works extremely well. I followed the "project EVS" plans on Joe Woodworker's website. Below are pictures of my rig which is pretty much stock with the only thing I need to add is hose management on the back and a handle up top, which I will do in the fall. As you will see on the Joe Woodworker website a lot of people have built this and have done all types of modifications to suit their needs.

https://www.joewoodworker.com/veneering/EVS/concept.htm

Here is a YouTube of a guy who built one and he shows you how he built his, which may inspire you, or at the very least provide you a better understanding of the logic behind the design.

[video=youtube;QQABdpQu8rg]https://www.youtube.com/watch?v=QQABdpQu8rg[/video]

Here are pics of my setup, now it's time to do my last layup.







 
Thanks for the review of the connector mpitfield... will be looking to see how actually using it goes for you!

So I didn't do my third and final T2T layup until today but I used the new connector...here are my thoughts.

- First thing I noticed is cutting the hole in the vacbag for the connector is a bit harder than my original connector. This is because the hole required is much bigger so it has to be a bit more accurate vs. just cutting a small hole in the bag. I think I have a round cutter somewhere about the right size, if so it will be a breeze to cut, if not I will come up with something to make it easier.
- Connecting the connector to the bag was much easier as the top ring and connector are much easier to grip and overall it feels like a much more secure connection.
- Connecting the airline is different as the original connector had an automotive style connector which was designed for pressure, not vacuum and just pushes on. The new connector is designed for vacuum so connecting it is different, you have to hold the release ring on the quick connector of the air supply as you push it on, then release.
- Because this new connector was designed for vacuum it has a check valve built in, so I can easily disconnect and move, which is important for me. On my original connector I had to install a ball valve after the quick connector, to maintain vacuum while I disconnected and moved, this was much more bulky.
- As far as it's ability to hold vacuum or not leak, well I did have leaks. However when I tracked them down it was not the connector but a new patch I applied to this vacbag, which I had used on the two previous layups. A bit of sealant help to reduce the leak but it was a stubborn one and I let it ride because the cycling frequency was reasonable.

Bottom line, I like the new connector and feel it is an improvement over my original connector on many levels. Having said that I feel that it will take more than one layup to come to a conclusion, however first usage makes me feel that it was a good choice.

I will be doing 2 more CF T2T layups in the next couple of weeks, both 3F, one 38mm MD the other 75mm MD, so I will have a better idea after that.
 
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