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rocketcharlie

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Yesterday I tried my first attempt at vacuum bagging fiberglass. I now have some questions. The part didn't come out very good but I'm anxious to try again.

I applied peel ply over the 5 layers of wetted out fiberglass on my body tube mandrel,then peel ply, then breather/bleeder fabric. I have seen "release film" mentioned in a list of materials, was this supposed to go in between the peel ply and breather fabric? I had a hard time stripping the peel ply, the breather fabric was stuck to it. Was this because I didnt use this release film?

How long should I wait before stripping peel ply ?

I used a 2 hour cure hardener, vacuum bagged it and applied about 140 degree heat to cure it. Was this correct?

Thanks in advance, the forum is a huge help!
 

JohnCoker

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You don't say what came out badly, did you get wrinkles? (5 layers of cloth is going to be tough to bag in one shot.)

What was hard about stripping the peel ply? Did it come off in small pieces and just was a pain to get off or did the breather stick to the part and that was hard to remove? You should only need one thing between the part and the breather, whatever you call it.

As far as the heating, that depends on your epoxy system. If it's room-temperature cure, then you don't need to heat it (just keep it at least at room temperature). If it's elevated temperature cure, then you need to follow the schedule.
You may be thinking of an elevated temperature post-cure, in which case the part would be debagged before the post-cure.
 

watheyak

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Sounds like you did it pretty correctly.

I think I've seen a similar materials list you mention. You could put some sort of perforated release film between the peel ply and breather to control the amount of resin that gets bled into the breather. But there are easier ways to control this. In most cases, the peel ply goes right next to the breather and they are suck together, sacrificial layers.

The length of time needed after stripping the peel ply is at least as long as the cure time. It should be fully cured. It won't be easy to remove the fabric type peel ply, it sounds like it's ripping. That's normal.

And I have the same question an John. What do you feel went wrong? Usually I get one line wrinkle along the length of the tube somewhere.
 

tfish

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If you get the Aircraft Spruce teflon porous release film..peel ply really imbedded in epoxy it's hard to get off/out. A layup with many layers and excess epoxy is pretty squishy..

Tony
 

rharshberger

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Pictures will help some, and I should have read your post a bit closer about your stack.
 

rocketcharlie

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The outer most wrap of cloth was protruding in spots so I cut it away with a knife, thinking perhaps I could fill it. I now realize the tube is a throw away.

The first micrometer reading is the part of the tube that came out OK, the 2nd is where one of the bulges I mentioned is located.
 

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Scrapmaster87

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Best to use a coated shrink tape for tubing:

Wind your finished layup with at least a 25% overlap. Gently use a heat gun to evenly shrink the tape, excess epoxy will start to weap out of the seams. I'm using a 1.5" tape with a 50% overlap in the attached picture

You'll be left with a fine spiral seam to sand/fill.
 

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JohnCoker

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Are those dry spots? I'm having a hard time understanding how you could have gotten the bulges.

The way I think about it is that bagging is going to reduce the circumference by squeezing out the epoxy and remaining air. That means the cloth needs to contract. If you stretch out the cloth as you roll you have some compression to work with, and if you get it as tight and remove as much epoxy as possible it has to contract less.

Small tubes are harder to make than larger ones and are more prone to wrinkles. What I think happens is that the ratio of diameter decrease to circumference varies so it's relatively easier for the cloth to contract on a larger tube.

Multiple wraps at one time are also more prone to causing wrinkles because there is that much more contraction.

I have had success with laminating tubes using vacuum bagging (typically 2 wraps over an existing tube) as well as success using a core material, but I have not been able to vacuum bag more than two layers at one time, and only on larger tubes (4" and larger).
 

rocketcharlie

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John, do you apply two layers, let them cure, then add more, or do you feel that two layers is enough? What do you mean by core material?

I'm thinking the bulges were because I wasn't able to get the mylar to lay down tight to the mandrel. It had loose spots in it that I wasnt able to secure with out tape which i have heard is a bad idea. I was hoping the vacuum would press the mylar flat.
 

OKTurbo

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I’ve never tried to vacuum bag a tube. Here are some mandrel made carbon fiber and Kevlar tubes I made using woven sleeves and heat shrink tubing from Soller Composites. Only one layer, but they were pretty easy to make.
AB4B0B77-7A60-4229-AF72-DFEFE48CF2AD.jpeg

9F31AA7E-D3C2-4685-8962-3B723E13A6BD.jpeg

I’ve had pretty good success with vacuum resin infusion for flat sheets. This shows how the peel ply comes off...and it’s not easy..
 

rocketcharlie

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OK, 2 people now have suggested I use heat shrink tape to remove excess epoxy from the lay up. I actually had never heard of this product before. I thought vacuum bagging with it's 14.7 psi evenly spread over the tube would be an ideal way to remove the excess. I guess I have much to learn.
 

rharshberger

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OK, 2 people now have suggested I use heat shrink tape to remove excess epoxy from the lay up. I actually had never heard of this product before. I thought vacuum bagging with it's 14.7 psi evenly spread over the tube would be an ideal way to remove the excess. I guess I have much to learn.
Thats why we ask questions. I personally dont use shrink tape or vac bagging on tubes, I just wrap it as tightly as I can two layers max, and put a layer of peel ply over that (mylar of course underneath as a release). My experiences with vac bagging tubes have been less than stellar, with wrinkles, bubbles etc. After the first two wraps get to green stage, off comes the peel ply and two more wraps with peel ply are added.
 

JohnCoker

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John, do you apply two layers, let them cure, then add more, or do you feel that two layers is enough? What do you mean by core material?
No, you wouldn't let them fully cure, because then the next layers would only make a mechanical bond (not a chemical one). You could apply a layer or two, let it go to the green stage, then apply more, but that seems like a lot of work.

There's no reason to make a solid fiberglass tube. You can instead use a layer or two inside, a core, then a layer or two outside. For example, this is how I made 5" ID tubing for my Nike-Asp: jcrocket.com/nike-asp.shtml#tubes. The advantage there is that you're only bagging two layers of reinforcement at a time and the core provides the bulk of the tube (creating a truss structure).


I'm thinking the bulges were because I wasn't able to get the mylar to lay down tight to the mandrel. It had loose spots in it that I wasnt able to secure with out tape which i have heard is a bad idea. I was hoping the vacuum would press the mylar flat.
You shouldn't be using Mylar AFAIK.
 

JimJarvis50

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No, you wouldn't let them fully cure, because then the next layers would only make a mechanical bond (not a chemical one). You could apply a layer or two, let it go to the green stage, then apply more, but that seems like a lot of work.

There's no reason to make a solid fiberglass tube. You can instead use a layer or two inside, a core, then a layer or two outside. For example, this is how I made 5" ID tubing for my Nike-Asp: jcrocket.com/nike-asp.shtml#tubes. The advantage there is that you're only bagging two layers of reinforcement at a time and the core provides the bulk of the tube (creating a truss structure).



You shouldn't be using Mylar AFAIK.
I would agree about not using Mylar. The purpose of compression is to squeeze out excess epoxy. If you use Mylar, there is no where for the epoxy to go, and if you used Mylar, why would you need peel ply?

The procedure I use is to add a little weight to the end of the cloth to keep it tight as you roll the tube. This eliminates most of the excess epoxy weight. Then add peel ply on top of that, but no breather.

Edit - OK, you're talking about Mylar on the mandrel and not over the layup. Never mind. I would still recommend weighting the cloth as opposed to trying compression on tubes. I have never successfully compressed a layup with more than a layer or two of cloth. FWIW, I have applied breather directly over the peel ply (when bagging fins). I haven't found that it makes it any more difficult to remove the peel ply, but I prefer to use a perforated release.

Jim
 
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rharshberger

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No, you wouldn't let them fully cure, because then the next layers would only make a mechanical bond (not a chemical one). You could apply a layer or two, let it go to the green stage, then apply more, but that seems like a lot of work.

There's no reason to make a solid fiberglass tube. You can instead use a layer or two inside, a core, then a layer or two outside. For example, this is how I made 5" ID tubing for my Nike-Asp: jcrocket.com/nike-asp.shtml#tubes. The advantage there is that you're only bagging two layers of reinforcement at a time and the core provides the bulk of the tube (creating a truss structure).



You shouldn't be using Mylar AFAIK.
I believe he is using the mylar as a release layer over the mandrel, iirc TFish uses that method, but getting it to lay perfectly flat is a pain until experience is gained.
 

tfish

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Charlie reached out to me after his layup. I did not know he was vacuum bagging. Yes I use mylar as a release and to build up the (motor tube) mandrels.

Tony
 

kalsow

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I agree with 99.44% of what's already been said. I've had very little success compressing tubes. Usually I don't try. The best results I've achieved were using the biaxial woven tubes and heat shrink like OKTurbo showed. The next best thing is to cut your fabric on the bias so that the fibers run 45 degrees relative to the tube's major axis. Then when you squeeze, from the middle of the tube out to the ends, the excess fibers have somewhere to go. Any fibers that are at 90 degrees are pretty much forced to bunch up. I've never tried it, but some people claim to be able to compress wraps that are mostly 0 degree unidirectional fibers. FWIW.
 

rocketcharlie

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Jim, I was about to point out that the mandrel I used was a PML cardboard coupler tube which I believe is your suggestion, but then I noticed your edit, laugh. I cant imagine getting the motor tube off of this type of mandrel with out something in between cardboard and epoxy.

Tony, yes I used Mylar per your excellent video on laying up a body tube.
 

rocketcharlie

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John, that is an interesting "truss" composite you are using for your Nike-Asp. I have learned of several new material and techniques through this thread.
 

TonyL

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As you are finding out, tubes can be very difficult to get wrinkle free. The braided sleeve is the only material I have been able to vacuum bag with moderate success. The pleat always leaves a mark and I moved on before getting around trying everything to eliminate it. Many swear by the spiral wrap heat tape but as noted, that also leaves a mark.

I use Dacron cloth from aircraft spruce [best prices I find], the heavier weight is easier to peel, the lighter weight is easier to conform but easier to wrinkle. Any peel-ply will peel easier when the resin is still green [not sticky but not rigid], the more cured it gets, the harder to peel. For regular peel ply I always use perforated against the laminate to give resin and air somewhere to go.

My composites instructor told us that virtually every room temperature curing epoxy sold over the counter benefits from curing at >100 F. Many of these systems call out 140 F as the maximum cure temperature. The good news is that anything between 100 F and 140 F for about 8 hrs should the job of getting the best possible cured properties.

Realistically it does not matter in practice, room-temperature-cure epoxy cured at the max temperature is about the same behavior as that epoxy just cured at room temperature. If one's design is so marginal that epoxy cure schedule matters, one is probably doing something wrong.

A single layer convolute-wound around a paper or phenolic tube does a lot of good and is easy enough to do, 5 layers is getting close to the thickness of a commercially made tube. Generally I find commercially made tubes have been wrapped on a mandrel [both filament-wound and convolute-wound] and then ground down to size [so they don't even try to make a smooth tube]. For a small tube like that, anything but the sleeving is going to be challenging.

For larger tubes [>4inches], convolute wound with a tensioned peel ply [Dacron cloth with weights hanging on it] does an excellent job of compacting the lay up and minimizing seams. I can describe that in detail if it is of interest.

Also wet layup without vacuum can be pretty efficient with effective peel ply usage, only a few percent difference in resin content from good vacuum bagging.

Ultimately I believe that a wrinkle free vacuum bagged tube could best be made through resin infusion with a heat shrunk bag that did not require pleats. I never did invent that bag...

hope this helps,

Tony
 

rocketcharlie

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That does help Tony! Thanks for writing all that. I would be interested if you would talk about weighted peel ply. In my mind I'm seeing the peel ply being slowly pulled off the lay up.

You had a composites instructor? I think I need such a person in my life.
 

TonyL

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Sure, I will describe my method that I have used with good success even wrapping 12k carbon twill around tubes 6 inches to 12 inches in diameter, while 3k carbon twill has been a little too stiff on 3 inch tubes to get a good result. Fiberglass being much softer should be happy down to smaller diameters.

The basic principle is to anchor the laminate to the tube and then use the peel ply to put tension on the laminate and provide some uniform, wrinkle free compression.

1. Draw a straight line down the tube, parallel to the tube axis. Use 5 minute epoxy to glue the edge of the fabric to the tube. I use a continuous length of blue tape to hold the fabric in place until the epoxy cures, rubbing it out to keep the seam reasonably smooth. As soon as the epoxy is cured, remove the tape, being careful not to pull yarns out of the fabric.

2. Support the tube on a horizontal pole, I use a length of 3 inch PVC pipe across two saw horses. I uses a reverse wrap of duct tape to act as a break to keep the tube from turning on the PVC and duct tape the pipe to the saw horses. An assistant also works [but eats more].

3. Wrap the fabric one turn and wet it out with a brush. If there is more than one turn, wet them out one at a time so you don't have to push resin through more than one layer. An idea I have not tried specifically with the technique would be to wet the whole cloth on a table after the edge is anchored and wrap it wet. Could be better, could be disastro...

4. Once the fabric is on and wetted out, wrap the heavier weight Dacron peel fabric in the same direction as the laminate fabric once around. The Dacron should be long enough for 2 to 2.5 time around the wrapped tube, more for smaller tubes. As you are wrapping it you should be also wetting out out, pushing resin through it with a brush wherever you see bubbles under the Dacron. Eventually you should have a uniformly saturated wrap with few to no bubble visible. Overlap the Dacron on itself about half a turn, all wetted out, letting the slack hang tangent to the edge of the wetted area.

5. I hang pinch clamps about every six inches depending on the viscosity of the resin. Too much weight will drag the fabric off the wrap so watching it closely early on is important. As the resin heats up its viscosity drops so it may start happy and then start to slip. As long as the peel fabric does not expose the laminate cloth, it is fine. I try to get one too many pinch clamps hanging from the fabric and then remove one or two depending on what makes a good looking distribution that stays put. The stack up will drip excess resin so be prepared.

6. Once the resin cures [preferably same day while it is green], I first trim the ends of the tube to remove the loose wetted yarns that stick out. These can pierce flesh much deeper than one might imagine, driving uncured epoxy into one's body. Seems like a problem. Then I peel the Dacron as soon as the resin is rigid enough to peel nicely. I does not get better than this, so same day is better than next day if one has enough time [but not that big a deal if one has to leave until fully cured, one just has to pull harder]. The Dacron leaves an easy to sand surface, alternately it can be burnished instead for a pretty good finish, but not as smooth. It also provides an ideal ready-to-bond surface if one peels it right before bonding, so sometimes it may be desirable to leave some Dacron fabric on.

I have always done it in one go, but one could wrap the tube more than once. I also have washed out the cardboard sometimes for an all composite tube. A hot tub works well for the big tubes.

hope this helps,

Tony
 

TonyL

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Also, Abaris provides hands on instruction on many aspects of composite layup. I thought they did a good job.
 

rocketcharlie

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Thanks Tony, I was trying to imagine how a person might apply weight to the edge. Pinch clamps makes good sense and gives you some easy control of the amount and distribution of the weight.

I hadn't heard of Abris before. I will look into what they offer, but probably will wait to seriously consider a class until the pandemic is under control.
 

JimJarvis50

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Thanks Tony, I was trying to imagine how a person might apply weight to the edge. Pinch clamps makes good sense and gives you some easy control of the amount and distribution of the weight.

I hadn't heard of Abris before. I will look into what they offer, but probably will wait to seriously consider a class until the pandemic is under control.
I typically hang a motor tube or something like that to apply weight to the cloth itself. It makes a big difference in the quality of the layup. If the cloth is rolled under tension, it is not necessary to do that with the peel ply. I have a jig that I made (third pic) that lets me keep tension when applying a long piece of cloth. It's possible to over-do the weight though. It doesn't take that much weight to get improved results.

Jim

DSCF1017.JPGDSCF1018.JPGIMG_0486.JPG
 

TonyL

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Hi Jim,
Yet another clever technique, nice to see. How to you deal with the free edge of the fabric? I am assuming you have to release the tension to finish the wrap?
 

JimJarvis50

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Hi Jim,
Yet another clever technique, nice to see. How to you deal with the free edge of the fabric? I am assuming you have to release the tension to finish the wrap?
Tony, you have obviously not (recently?) read my articles on tube making! The links are below for reference (I repost them when I have an excuse every year or two). Much of this is not relevant for fiberglass, and much of it I would now do differently, but there are still a few useful tidbits.

http://www.raketenmodellbau.org/repository/archive/167792?view=true (Part 1)

http://www.raketenmodellbau.org/repository/archive/167793?view=true (Part 2)

To answer your question, the carbon is cut at the end of the process (under vacuum to avoid fibers). This releases the tension. However, the purpose of the weight is to remove excess epoxy from the multiple wraps as the tube is being rolled, but not to actually stretch the cloth. You get a layup that isn't squishy and has a better cloth to epoxy ratio.

Jim
 

TonyL

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Hi Jim,
Only 217 easy to memorize pages :)

I do like what you do with the masking tape slits to relieve that part of the wrap. I think the main difference is that you compact your fabric as you go and leave it at that, which should work out fine. Fiber stiffness tends to want to unwrap the cloth, not a strong force by any stretch, and the surface tension/viscosity of the resin with a peel ply is easily enough to hold it down as you have shown. I like the tensioned-after method because it squeezes the excess out through the peel ply, offering the opportunity to purge remaining bubbles.

I would mention that your hot box is probably unnecessary during initial cure. You could easily post bake it at whatever temperature was desirable after initial cure with no adverse effects expected on the Dacron or the tube. Epoxy laminating resin does not normally distort during post baking, unlike the styrene based resin commonly used for commercial fiberglass work. You could also change to a bagging film instead of mylar to get higher temperature tolerance, and there is some nice and smooth material available.

You are getting great results, so no criticism intended.

br/

Tony
 

rocketcharlie

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Jim, Tony and others, your reply has brought up a question for me. I started this thread asking about fiberglassing a 38 mm tube. How many wraps of 6 oz. fiberglass would you use? Also do you have any trouble with slippage of the cloth as you begin because it is weighted?

ps to Jim- those pictures help a bunch
 

TonyL

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If I had to wrap cloth, I would use one layer of 6 oz on a phenolic tube, for a tube on a mandrel I would go for between .040 and .060 for the finished tube [3-4 wraps maybe?]. I would try wet layup with a peel fabric [without tension] first to see if it comes out reasonably. Vacuum bagging is not critical to a good quality laminate.

Really I would use a braided sleeve and peel fabric for a phenolic tube as it can come out so much nicer. The more important question is: what do you need for tubing? If you just want to make your own tubes, you can try some stuff suggested or try other ideas that you have. If this is a conventional HPR rocket, then one wrap of 6 oz on a phenolic tube should be plenty for most rockets. If it really needs to be stronger than that, consider buying filament wound vs. your tube wrapping development and see which way you want to go.

hope this helps,

Tony
 
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