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Do I need a rotisserie?

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BDB

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I glassed another tube yesterday, and I'm pretty happy with the results. Definitely getting better each time I do it. This time I wrapped with mylar, and 90% of it came out super-smooth. But there are a few divots in the finish. Could a rotisserie fix this, or do I need to upgrade to a vacuum bagging system to get a uniform smooth finish?
ImageUploadedByRocketry Forum1490542278.739377.jpg
 

jd2cylman

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Here I thought this was gonna be another meat thread... :wink:
 

markkoelsch

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What weight glass did you use, how many wraps, and how much epoxy?
 

BDB

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This was a single wrap of 2 oz glass. I'm just trying to reinforce an Estes tube. The glass weighed 24 g and I needed about 150% (by weight) as much epoxy. That may be too much, but that was what it seemed to need to wet it out this time.
 
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ksaves2

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If I understand correctly a rotisserie allows the epoxy to stay in an even layer about the wrap as opposed to gravity pulling the epoxy to the dependent area (facing down). Kurt
 

dhbarr

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That's why you put a mandrel in.
 

boatgeek

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That looks like a bubble between the laminate and whatever you laid over the top. Part of the reason for that is that you have a lot of epoxy pooled on the surface, which makes sense if you used 150% epoxy by weight. A rotisserie might solve that if you didn't put a layer of wax paper or something over the top of the laminate, but it won't solve the problem of too much epoxy. For 2oz cloth, you can probably wet it out with just a little epoxy painted on to the tube surface. Once you work the cloth into the epoxy with a roller or brush, it will go clear. After that, don't add more epoxy, or you'll get the result you have here. Once the epoxy sets, you can add another thin layer to fill in the weave or wait and do it with a lightweight sealer/sander. The epoxy on the surface doesn't add strength, just improves the finish.

Another option I haven't tried is using a peel ply over the cloth. Others can weigh in on that.
 

BDB

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Another option I haven't tried is using a peel ply over the cloth. Others can weigh in on that.
I've tried peel ply in the past and it worked well, but left a little texture on the surface. I was really trying for a perfect finish this time. You are right that the issue is not bubbles under the FG; this looks like it is the result of bubbles forming between the surface and the mylar. I probably went a little overboard with the epoxy.
 

GregGleason

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The rotisserie if for post-cure ramp-up heating, and the only reason for doing that is to increase the Tg of the epoxy. During the initial cure you risk it bubbling (don't ask me how I know!).

What I suggest are these:

https://www.ebay.com/itm/like/121425557489?lpid=82&chn=ps&ul_noapp=true

As you place the FG onto the airframe, roll and roll and roll. You will be wicking up the excess epoxy and pressing the FG against the airframe or underlying layer of FG. Wipe off the excess epoxy on the roller with acetone and keep going.

That's the way I do it that works for me.

Below is how I get a super-shiny gloss coat on fiberglass.

Glossy.Fiberglass.on.2.60.inch.Tubes.jpg

https://www.rocketryforum.com/showthread.php?52038-New-Technique-Glossy-Surface-on-Fiberglass

Greg
 

Dave A

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You can run the rotisserie for 4-6 hours using a simple timer, got the motor at Home Depot and you just need some bulkplates and 3/8" all thread. That will help the epoxy from pooling in spots.

1490570918708.jpg


1490570946813.jpg
 

BDB

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The rotisserie if for post-cure ramp-up heating, and the only reason for doing that is to increase the Tg of the epoxy. During the initial cure you risk it bubbling (don't ask me how I know!).

What I suggest are these:

https://www.ebay.com/itm/like/121425557489?lpid=82&chn=ps&ul_noapp=true

As you place the FG onto the airframe, roll and roll and roll. You will be wicking up the excess epoxy and pressing the FG against the airframe or underlying layer of FG. Wipe off the excess epoxy on the roller with acetone and keep going.

That's the way I do it that works for me.

Below is how I get a super-shiny gloss coat on fiberglass.

View attachment 315667

https://www.rocketryforum.com/showthread.php?52038-New-Technique-Glossy-Surface-on-Fiberglass

Greg
Thanks, Greg. I should have read your thread before I tried this. When you use the roller, do you roll lengthwise on the tube or laterally? Also, is there a particular size of roller that you suggest?
 

GregGleason

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You roll the roller on the airframe perpendicular to the long axis.

A roller length of 3" to 5", with a diameter of 1/2" to 2" should work.

Greg
 

Eat, sleep, and Fly

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do I need to upgrade to a vacuum bagging system to get a uniform smooth finish?
View attachment 315642
Vacuum bagging tubes successfully is somewhere between really tricky and impossible (unless there is some new technique out there that I've never heard of). Imaging taking a circle and trying to shrink it without changing the circumference, the only option is to wrinkle. That is what you are doing to the peel ply and fiberglass when you vacuum bag a tube. I've tried it, it doesn't work. The excess fabric simply has nowhere to go. Also vacuum bagging using Mylar instead of peel ply would, I suspect, yield less than ideal results. I would suggest using peel ply with no vacuum, and using a high build primer and some sanding to hide the texture.
 

3stoogesrocketry

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I glassed another tube yesterday, and I'm pretty happy with the results. Definitely getting better each time I do it. This time I wrapped with mylar, and 90% of it came out super-smooth. But there are a few divots in the finish. Could a rotisserie fix this, or do I need to upgrade to a vacuum bagging system to get a uniform smooth finish?
View attachment 315642
What type of epoxy did you use ? You also mentioned using more epoxy then fiber by weight . This to me is a clear indication that your epoxy is to thick . Are you using a 15 minute hobby store epoxy ? I would suggest purchasing some thin laminating epoxy . I prefer US Composites 3/1 thin fast system .

Eric
 

BDB

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I used US composites 3:1.
 

rfuss

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Wouldn't it crush a Estes tube??
I just used this, colored fiber woven sleave with treated heat shrink, on a 3" estes (from the Scion kit). It didn't crush, came out very smooth in most areas, but I underwetted sections that I have to consider redoing or leave rough and fly as-is. A portion of the sleave was too tight, wouldn't call it a manufactor defect as I had sized it at the limits; I had to partially crush the tube to get the sleave to fit and then used the centering rings to push back out. I didn't leave those in during cure, probably should have, but it had minimal effect if any. The shrink did have enough pressure to deflect the fin area where the slots had already been cut, will take a little extra external fillets to even up.IMG_20170329_095317.jpgIMG_20170329_095900.jpgIMG_20170329_100234.jpg
 

boatgeek

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Thanks, Greg. I should have read your thread before I tried this. When you use the roller, do you roll lengthwise on the tube or laterally? Also, is there a particular size of roller that you suggest?
A roller like this guy works wonders in getting the glass to lay flat and get bubbles out from under the cloth. It's a bit of a pain to clean, but the more you do with epoxy soft, the better off you are. Roll around the tube for best results.

IMG_0873.jpg
 

mccordmw

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The depressions that show weave are where the mylar did not stick to the fiberglass. When you start laying on the mylar, you need a squeegee to press down the mylar as best as you can. A rotisserie will simply keep the epoxy from pooling on the bottom. Go slow with the mylar, squeegee hard. Even then, I'll still have a couple small depressions on the bigger tubes.

Also, don't use too think of a mylar. The thicker stuff is harder (for me at least) to get to lay flat.
 

mccordmw

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I should add. I fill the depressions, if small, with a quick skim of more laminating epoxy. The bigger ones get light weight Bondo filler.
 

soopirV

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I'm glad I'm not the only one who struggles with this! John Coker makes it look so darn easy on his site. I used qcells or carbosil, (can't remember which one is sandable) in another batch of laminating epoxy to fill my voids, and it came out well (finally!) but was a lot of work!
 

BDB

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