Fiberglassing Airframes and Epoxy Questions.

[Coop]

I've been giving consideration to future builds going a lot faster than anything else I've flown --other side of Mach 1-- and I'm considering reinforcing the airframes with fiberglass. I'll probably do a couple of the smaller builds with FG to get the technique down. I've searched for the video tutorials and browsed supply stores looking at epoxies and cloth... I can figure out how much cloth I need by circumference. I don't know how much laminating epoxy I'd need, though--pint? Quart? Gallon? Schooner? Is there a general rule-of-thumb for this? How much do you generally need for three wraps on a 4" airframe? 5.5? 7.5? Or is it better phrased as "How many (diameter) builds do you get out of (volume)?"

A rocketry vendor might do well to make a "Hey, wanna fiberglass that kit? Kit," with enough cloth and epoxy for standard sizes, a couple of gloves and a widget or two... just sayin'...


Later!

--Coop

 

[blackbrandt]

Look at this thread, there are some good vids in there.

 

[troj]

Three wraps is overkill.

You'll also find that wrapping a bigger tube is easier than a smaller one -- start with something in the 3" - 4" range, rather than something smaller.

The ideal amount of resin is, by weight, the same as the cloth. That said, especially since it's your first time, you'll use more resin than you need to.

If you think you're going to do more in the future, buy a quart of resin, and the appropriate amount of hardener.

-Kevin

 

[Aksrockets]

I don't know how much laminating epoxy I'd need, though--pint? Quart? Gallon? Schooner? Is there a general rule-of-thumb for this?

You'll need about the same weight of laminating resin as you do cloth. I usually buy by the quart, but that's because I'm poor and cant afford anything more.

How much do you generally need for three wraps on a 4" airframe?

I agree with Kevin, 3 wraps is a bit too much (although i guess if you use a really light weight cloth you'll be fine)
I usually use 1-2 wraps of 4-6 oz cloth on my airframes.

Also another tip: buy peel ply. It will make a huge difference in aesthetics and how easy the rocket is to finish. I hardly do layups without it.

Good luck and let us know how this turns out. Ask questions!

Alex

 

[Coop]

Three wraps is overkill.

You'll also find that wrapping a bigger tube is easier than a smaller one -- start with something in the 3" - 4" range, rather than something smaller.

I figured 2 wraps of heavier cloth, one of lighter--which I thought was pretty much standard... no? And the smaller tubes I was going to do --at first-- were 4".

The ideal amount of resin is, by weight, the same as the cloth. That said, especially since it's your first time, you'll use more resin than you need to.

If you think you're going to do more in the future, buy a quart of resin, and the appropriate amount of hardener.

Aaah... okay. Good to know. I didn't want to get too little... or way too much, and have it lying around forever...

Thanks!



Later!

--Coop

 

[troj]

I figured 2 wraps of heavier cloth, one of lighter--which I thought was pretty much standard... no? And the smaller tubes I was going to do --at first-- were 4".

Two wraps with something along the lines of 5 oz is plenty. When you use the peel ply, you won't have much to fill.

I've only used a veil layer once, and that's because I was covering over some pretty coarse carbon fiber.

-Kevin

 

[Coop]

You'll need about the same weight of laminating resin as you do cloth. I usually buy by the quart, but that's because I'm poor and cant afford anything more.


I agree with Kevin, 3 wraps is a bit too much (although i guess if you use a really light weight cloth you'll be fine)
I usually use 1-2 wraps of 4-6 oz cloth on my airframes.

Also another tip: buy peel ply. It will make a huge difference in aesthetics and how easy the rocket is to finish. I hardly do layups without it.

Good luck and let us know how this turns out. Ask questions!

Alex

I was sold on peel ply when I saw tfish's Tough Enough build thread long ago--I'd planned on that! While I don't MIND sanding as others admittedly do, I figure there's little need in omitting a step which could cut down on the amount of it.

I'll let you know how it goes! Thanks!


Later!

--Coop

 

[Coop]

Look at this thread, there are some good vids in there.

There are good videos in there...


Later!

--Coop

 

[Coop]

Two wraps with something along the lines of 5 oz is plenty. When you use the peel ply, you won't have much to fill.

I've only used a veil layer once, and that's because I was covering over some pretty coarse carbon fiber.

Aaah... all right. I'm tracking you now. Thanks!


Later!

--Coop

 

[GregGleason]

One of the most important things with regard to epoxy is:

1) getting the ratios correct, therefore you need a scale that can measure to grams so that you don't compromise the strength.

2) thoroughly mixing he resin and hardener, so that you have a homogenized resin for the layup.

One thing that I have found is that while the process isn't that hard or tedious, it always takes longer than I plan.

Greg

 

[Coop]

One of the most important things with regard to epoxy is:

1) getting the ratios correct, therefore you need a scale that can measure to grams so that you don't compromise the strength strength.

2) thoroughly mixing he resin and hardener, so that you have a homogenized resin for the layup.

One thing that I have found is that while the process isn't that hard or tedious, it always takes longer than I plan.

Greg

Noted. I usually work on rockets after I get off shift, to decompress--so taking longer than planned isn't TOO much of an issue--I'm something of an insomniac anyways--heheh. I'm good on scales and such--have unlimited access to nitrile gloves and have worked with structural epoxy plenty... just not for laminations. I can eyeball how much I'm going to need to mix up for a CR/MMT joints, fin attachment, fillets, and other build-related applications--just wouldn't have a clue as to how much for laying glass down on an airframe or tip-to-tip fin layups. Seems like "oodles," is close... if not "lots."

Later!

--Coop

 

[GregGleason]

This is the direct link from blackbrandt's post from tfish, which is pretty helpful walk through on putting FG on an airframe:

[YOUTUBE]q3wtcNTd9wg[/YOUTUBE]

Greg

 

[tfish]

As for weight of FG and how many wraps..all depends on what you're trying to accomplish. Two wraps of 5-6 oz would be good for some mild sport flyring. 4-5 wraps min dia stuff. To figure out the circumfrence of you're body tube..use a piece of string wraped around tube. Say your planning on 3 layers..wrap the string around three times and then add a couple inches to the final string length. To figure out how much epoxy...Cut out your FG and weight it. For your first time I'd mix up 1.2 times what the FG weighs. Make sure you get laminating resin. "Other" resisns are to thick and are hard to use in the application.

Where are you a Ghettomedic?

Tony

 

[jpummil]

I'm guessing CF would be the same process...

 

[GregGleason]

I'm guessing CF would be the same process...

Yep. The chief differences being that carbon cloth is a little stiffer than fiberglass so you have to work it a bit more. And it is much harder to tell when carbon has been wet out, whereas fiberglass is easy as it turns nearly transparent.

Greg

 

[Coop]

As for weight of FG and how many wraps..all depends on what you're trying to accomplish. Two wraps of 5-6 oz would be good for some mild sport flyring. 4-5 wraps min dia stuff. To figure out the circumfrence of you're body tube..use a piece of string wraped around tube. Say your planning on 3 layers..wrap the string around three times and then add a couple inches to the final string length. To figure out how much epoxy...Cut out your FG and weight it. For your first time I'd mix up 1.2 times what the FG weighs. Make sure you get laminating resin. "Other" resisns are to thick and are hard to use in the application.

Where are you a Ghettomedic?

Tony

Thanks, Tony! I'll go with the 1.2x cloth weight as a starter, and see how I develop from that!

I'm a ghettomedic in Harrisburg city. Never a dull moment!


Later!

--Coop

 

[AandP]

standard for aviation is generally 60/40 resin weight/material. Although it is always recommended to mix a little extra resin to account for waste/test sample.
https://www.ptm-w.com/dynamicdata/data/docs/laminating resin usage chart.pdf

60/40 aeropoxy mix with peel ply and some heavy squeegeeing should finish out glass like. It's not recommended to sand directly on your dried lay up to get out the pinholes you didnt quite fill. Just lay down high build primer and sand it off rinse repeat til you get a surface suitable for color. Sanding the layup directly negates the purpose of fiberglassing and makes week spots, especially if you hit the glass. Even the loss of the resin is bad if properly mixed. The resin (matrix)'s prime job is to transmit forces between the fibers.

Most of this may be overkill for the average build but if your going to build it build it like a pro. Bad habits are easier to avoid than to unlearn. good luck, wear a respirator and have fun with it.

good read that is way over the top for most hobbiests
https://www.faa.gov/library/manuals/aircraft/media/FAA-H-8083-31-AMT-Airframe-Vol-1.pdf

chapter 7 all the aerospace secrets you could ever want.

edit.. tfish's video's are probably the best videos on at home fiberglassing i've seen. well done.

 

[neond7]

If you think you will be doing more airframes in the future, I recommend you get a gallon of West 105 resin and a quart of West 206 (slow) hardener. Pick up a set of the metered pumps and you will save a lot of time/mess/effort weighing it. Search on Amazon, you can pick up these the epoxy set for about $110 plus shipping.

What I really like about this system you can also do all your bonding with this epoxy and the different West System fillers that are available. When I apply fillets, I mix up a squirt each of epoxy/hardener in a disposable cup, mix well, and then add a 50/50 mixutre of 404 High-Density Filler and 406 Colloidal Silica until its nice and thick. It makes a creamy, peanut butter texture and won't run, drip, or sag.

I'm already on my second gallon of resin, the first gallon lasted me about 6 months of heavy building. I rarely use the 30 or 15 minute epoxies anymore unless I'm just bonding something small. The shelf life is good, and can sit on the shelf for a few years. I've done alot of experimenting with the fillers, it takes a bit of trial and error until you find what works good for you.

Good luck!

 

[Coop]

I'm undecided on which brand I'll try first. Both Aeropoxy and West Systems seem to come up frequently--so I can assume that both work. Local availability isn't much of a factor for me, as I plan on ordering online. I do plan on doing more of this in the future. I can see the advantages of having the reinforced airframe and pre-made composite airframes are out of my price range. That said, I'm trying to get the reinforcement while keeping costs that could reasonably fit my wallet --which is why I'm asking the questions! Heheh.


Later!

--Coop

 

[CarVac]

If you work in a hot environment, Aeropoxy is less likely to have thermal runaway than West.

Personally, I think using a laminating epoxy as an adhesive with fillers is silly, but that is possible with either.

Also, you can use the West System pumps on either; both are 3:1 ratio.

 

[Coop]

I'm in PA, so heat isn't a factor (it's more the LACK of it. I loathe winter!). By "thermal runaway," do you mean the rate of cure when it's warmer, or something else? Which one has fillers?


Later!

--Coop

 

[troj]

I'm in PA, so heat isn't a factor (it's more the LACK of it. I loathe winter!). By "thermal runaway," do you mean the rate of cure when it's warmer, or something else? Which one has fillers?

Yes.

Epoxy is exothermic (it generates heat as it cures), and heat also accelerates the cure. So, a batch in a small container and a warm environment can literally cook itself to almost an instant cure.....and in the process, can melt the container that it's in.

Since you're in PA, you do need the other -- many epoxies have instructions that say that the minimum cure temp is 70F.

-Kevin

 

[Nessalco]

+1 to coaxial sleeves for glassing body tubes. Soller Composites sells a great variety, and are wonderful to work with. Stay away from the kevlar sleeves for most stuff - it's been impossible for me to cut them cleanly - though they make wicked strong tubes.

Also with sleeves, it's very easy to make very light airframe tubes. Lay a single wrap of vinyl window material over a section of coupler tube, 2 or 3 layers of sleeving, wet it out, and you're good to go.

Remember that if you glass a body tube, you are increasing its' diameter, and it won't mate exactly with a standard nose cone. Of course, if you make the tube from the fiberglass/CF only, it will be a smaller diameter than the nose cone, inducing turbulence.

Also, you can use the West System pumps on either; both are 3:1 ratio.

Sorry, West system is a 5:1 mix ratio by volume.

Kevin

 

[CarVac]

When you buy pumps, it comes with the 1, the 1/3, and the 1/5. I think one of the West hardeners is 3:1... I don't know why else they would have that pump in that set otherwise.

 

[G_T]

When working from gallon containers I like to use the pumps. They certainly are convenient. I put the container to receive the epoxy and the hardener on a scale, and pump into that, to get the exact weights I want of each. I do not trust the pumps to always yield the best ratio. I've had pumps spit air, I've had them not pump at the beginning of a stroke, and the ratios are not exact anyway. I recommend a procedure such as mine rather than trusting the pumps. With weighing, you'll know the ratio is correct.

For that matter, it doesn't matter what ratio the pumps are set for, if one is just using them to extract epoxy from the cans.

West kicks itself off rather quickly. It is best to pour the mixed epoxy out onto a plastic picnic plate(s) so it forms a thin layer. This will increase the working time.

A paint roller is a good fast tool for transferring the epoxy from the plate to the tube. It makes putting down a uniform layer of epoxy easier. One can use the roller to pick up epoxy from wet areas and transfer it to dry areas.

Gerald

 

[Coop]

Good tips, GT! Will keep those in mind--thanks!


Later!

--Coop

 

[Nerull]

When you buy pumps, it comes with the 1, the 1/3, and the 1/5. I think one of the West hardeners is 3:1... I don't know why else they would have that pump in that set otherwise.

205 and 206 hardeners are 5:1, 207 and 209 are 3:1.