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  #1  
Old 06-17-2007, 12:32 PM
coolamber coolamber is offline
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Default Seatback top done (sort of)

Well yesterday was plane day number 1 and I got done sometime after midnight. I decided to try the lovac technique and I swear it took me 3 times as long as a standard layup would have But I learned a lot so its all good. I did have an issue with a small part of fiberglass that decided to delaminate with the peel ply. Here are some pictures The question I have is, what is the easiest way to repair this?

Second question I have is. I applied micro to the surface and squegeed all the excess off, but when I was squegeeing the epoxy on the uni layers, I noticed some micro was seeping up through the layers and ending up in the upper layers.
So the question is, is this bad, and if so how do I avoid it?
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Old 06-17-2007, 12:49 PM
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Default Re: Seatback top done (sort of)

I do my micro-slurry first with the fast epoxy. Let it cure and then hit it with a orgital sander to rough it up and take of the high spots. Then do your layup.
It's called "hard shelling" and there has been a lot of discussion on this in earlier threads this year.

I had the edge delam on one of my first layups. I just stood the piece on end, dribbled in some fast epoxy, put poly over it and clamped it between a couple boards.

I don't know if you can adapt this to the low-vac method, but I use a plastic tube for my layups. Currently, I've been laying out a pice of poly to work on. Glass my part and fold the extra poly over the top of the part. At that point I can remove the gloves and setup my bag, slip it in and turn it on.

In my (humble) opinion, VB technique does not take any more time to do (in fact it may save time.) I don't worry much about getting everything trimmed up nice if it's something I can clean up with a Fein Multimaster (and if you don't have one yet, get one!)

The real timesaver comes in having a excellect part the first time. If your delam problem persists, double check your ratio to make sure it is giving you enough hardener.
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Old 06-17-2007, 01:18 PM
coolamber coolamber is offline
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Default Re: Seatback top done (sort of)

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Originally Posted by TMann View Post

The real timesaver comes in having a excellent part the first time. If your delam problem persists, double check your ratio to make sure it is giving you enough hardener.
Yeah I set up my pump the other day and right away was impressed with the quality of mgs 285. Before that I was working with ez-poxy, can't stand that stuff. I hated the odor. The only odor I get from mgs with slow is a sight ammonia odor.

Anyway to the point. The other day my ratio was a perfect 100:40 (by weight) Yesterday it was more like 100:38, the only difference being the stuff was warmer because it was in a box with a goldenrod. So I tweaked the ratio to to 100:40.1. I think I am going to do a volume check later to see if something screwy is happening with one of the items expanding under heat
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Old 06-17-2007, 01:29 PM
chasingmars chasingmars is offline
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Default Re: Seatback top done (sort of)

For small little delamination on removal of the peel ply, I just use a little all-fast MGS dripped in, as T-mann suggests... it doesn't happen often. IF it's in a non-structural location, I might use some five minute, as it's tricky to accurately weigh very small batches of MGS so there's wastage unless I'm dressing a foam edge or something at the same time.

Anyhow, more to the point, the micro migrating in the laminate under vacuum can't be a good thing, as it weakens the resin, but by how much and if it's problematic is a bit in question. It takes very little micro to cloud epoxy, so a very small amount of migration can be visible I've found.

Still, generally, I had thought that it was more an issue for those of use drawing deeper vacuum and doing full up vac bagging than those using lo-vac. I'm a vac-bagger rather than a lo-vacer though, but I'd suggest making sure you've got the micro very well removed so that only the thinnest of layers is left (when I remove, I end up with slightly blue micro from scraping the H45 hard enough to bring off tiny bits of the foam). I'd also make sure you're not drawing too much vacuum.

Raises a question to me... if we're seeing micro migration in vac bagging, due to the pattern being visible through the P3 perforated ply, is there reason to worry that migration is also happening in low-vac, but because of the lack of a perf layer it's generalized, and therefore not visibly apparent?

Others have also suggested one cure is to mix the micro thicker. I'm not sure I agree with this advice, the micro isn't being sucked up wholesale, it's being dispersed as the raw epoxy moves though the glass at the micro-glass interface, and then pulled up, I'm not really sure of the mechanics in lovac though where theres no P3 perf layer, this might be why it doesn't usually happen, without the P3 layer, there's much less lateral flow within the laminate. Mixing the micro stiffer makes it harder for it to wet the foam, leading to a weaker interface, and loads the mix with more micro to be picked up. I stick with the standard mix and hardshell, I may end up raw epoxy coating what I don't want to hardshell if there's a need. Raw epoxy coating is one way to solve the issue, but, it's heavier, and may bring it's own issues.

Just my thoughts, more from a vac bagging perspective than lo-vac, so ymmv.
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Old 06-17-2007, 01:37 PM
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Default Re: Seatback top done (sort of)

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Originally Posted by coolamber View Post
Anyway to the point. The other day my ratio was a perfect 100:40 (by weight) Yesterday it was more like 100:38, the only difference being the stuff was warmer because it was in a box with a goldenrod. So I tweaked the ratio to to 100:40.1. I think I am going to do a volume check later to see if something screwy is happening with one of the items expanding under heat
I don't want to start a religious war here, but...

You might want to try the weighing technique vice your pump, if you're seeing that much drift. 38:100 is at the limit of the spec'd acceptable range according to the mfgr ( http://www.mgs-online.com/en/techinfo/pdf/01mgs037.pdf - see the ratio table where it says 100:40 +/- 2).

It's easier than it sounds, zero scale with cup, pour resin to weight, add 40% of that weight in hardener and mix. I always pour resin in five gram increments to make it easier (i.e. if I miss, I go up to the next nearest five grams). A little squirt bottle makes it easy to be exact, it takes a touch of practice and is slower than a pump, but I never have to worry about calibration. With a scale reading in 1g increments a good minimum batch size is 70 grams (50+20), which works fairly well.

Just out of curiousity, I hear people talking about measuring epoxy in "pumps", how much epoxy (weight) is in a single "pump"?
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Old 06-17-2007, 01:37 PM
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Default Re: Seatback top done (sort of)

a little slurry is fine.
we all peel glass one time..
start slow and watch the edges, its the week link
hard shelling is not in my planes. so i don't do it imo its not as good .
one down 160 to go !
good job, part looks good !

ps just fill with epoxi and wight. or cut it out and do a plans repair
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Old 06-17-2007, 01:47 PM
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Default Re: Seatback top done (sort of)

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Originally Posted by chasingmars View Post
I don't want to start a religious war here, but...

You might want to try the weighing technique vice your pump, if you're seeing that much drift. 38:100 is at the limit of the spec'd acceptable range according to the mfgr ( http://www.mgs-online.com/en/techinfo/pdf/01mgs037.pdf - see the ratio table where it says 100:40 +/- 2).

It's easier than it sounds, zero scale with cup, pour resin to weight, add 40% of that weight in hardener and mix. I always pour resin in five gram increments to make it easier. A little squirt bottle makes it easy to be exact, it takes a touch of practice and is slower than a pump, but I never have to worry about calibration.
don't scare the fish
the + or - 2 is for 100% we like 100 % but need to stay near the top of that graft, but....the epoxy is stable at less then 30%.
some epoxy will hold to 100/100 before it becomes unstable
the epoxy is only 20% of the overall , so a little off will be fine.
plus, at the start, you cant hurt anything (in my planes)
much later, you'll do harder layers that WILL count IMHO
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Old 06-17-2007, 01:48 PM
coolamber coolamber is offline
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Default Re: Seatback top done (sort of)

To clarify, the micro was not migrating under vacuum, it was migrating when I squeeged the glass.

I have 2 micro scales that are really fast to check. They are .1 gram accurate. I put 2 small cups tared on each scale. I put one cup under each outlet and then weigh. Its really fast. I keep a calculator next to the scales to quickly caclulate ratios. Ill just keep a wary eye on the pump until I know its good.

What kind of fast to slow mix of mgs hardener do most people usually run with? I have been using 100% slow right now until I know what I am doing.
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Old 06-17-2007, 02:17 PM
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Default Re: Seatback top done (sort of)

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What kind of fast to slow mix of mgs hardener do most people usually run with? I have been using 100% slow right now until I know what I am doing.
Okay..... I'm guessing you won't want to get this excessive but hey.... I'm a little anal.
I have 2 pumps set up. One is MGS/335 Fast and the other is MGS/335 Slow.
I had to redo my rear seat back. When I did, I used a layer of micr-slurry fast, waited an hour ........ did my layup......waited 2 hours, peeled, and then prepped the other side. I went real fast.

Most of my VB layups are 100% slow and put under vacuum overnight. Now.....with the 2 pumps setup, if I want something in between, it's 3 pumps fast and 2 slow (or whatever.) Once you gain confidence in your pumps accuracy, bang away!

One tip..... I've read where some suggest wetting out glass on poly and then trasfer to the plane part..... hasn't worked real well for me. I have better luck keeping my fibers straight if I align them on the part and then wet them out.... but that just might be me.

The router and template didn't go very well either. I found it worked better to make the holes on the bulkhead at the corners of each opening with a hole-saw and then connect them up using thefein multimaster or a saber-saw with a fine blade.
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Old 06-17-2007, 02:17 PM
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Default Re: Seatback top done (sort of)

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Originally Posted by coolamber View Post
To clarify, the micro was not migrating under vacuum, it was migrating when I squeeged the glass.

I have 2 micro scales that are really fast to check. They are .1 gram accurate. I put 2 small cups tared on each scale. I put one cup under each outlet and then weigh. Its really fast. I keep a calculator next to the scales to quickly caclulate ratios. Ill just keep a wary eye on the pump until I know its good.

What kind of fast to slow mix of mgs hardener do most people usually run with? I have been using 100% slow right now until I know what I am doing.
most use a 50 fast with 50 slow
i used 100 slow, but that was then this is now.
now i use unapproved stuff at 1/2 the price, no smell, thinner, just as strong
a small air-o-plane building place up here in WA. used it on the front of there new plane. it starts at the door and runs to the tip (composite) see photo.........hope it works, you never know about unapproved epoxy
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Old 06-17-2007, 02:24 PM
Jason Heath Jason Heath is offline
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Default Re: Seatback top done (sort of)

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To clarify, the micro was not migrating under vacuum, it was migrating when I squeeged the glass.

What kind of fast to slow mix of mgs hardener do most people usually run with? I have been using 100% slow right now until I know what I am doing.
When I first started this I had the same problem, I would pour on the epoxy and let it soak then start to squeege which would let the slurry start to mix with the first coat of epoxy and draw it into the layup. Since then, I have learned to start speading the epoxy thin and keep working it around until the glass was wetted out "not wet, not white" which keeps the slurry from working up into the layer of glass. If you watch the video (if you got it) or watch someone thats good at it, you'll see the same technic, which is the answer to your question, "Technic" and it will get easier as you progress.

FYI, I read somewhere that you should use 1 oz. of epoxy to one square foot of glass so I tried it, turns outs, that I end up with little waste and a proper layup.

I use a 50/50 mix with 285 but the above technic works with the EZ poxy and aeropoxy that I've used, the later need a little help from a heat gun to achive the same results.

Delaminating the glass when you pull the peel ply, I can only atribute to not being careful around the edges and not the mix ratio, no epoxy we use is completely cured the next day, dry to the touch, yes, but not cured. You could probably go pull all the glass off your seatback right now and not damage the foam.
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Old 06-17-2007, 02:29 PM
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Default Re: Seatback top done (sort of)

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starts at the door and runs to the tip (composite) see photo.........hope it works, you never know about unapproved epoxy
Wow! I love those blended vert stabs.
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Old 06-17-2007, 02:41 PM
Jason Heath Jason Heath is offline
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Default Re: Seatback top done (sort of)

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I had to redo my rear seat back. When I did, I used a layer of micr-slurry fast, waited an hour ........ did my layup......waited 2 hours, peeled, and then prepped the other side. I went real fast.
I hope that was suppose to be funny, it took less than a hour to do mine the conventional way.

Quote:
Originally Posted by TMann View Post
One tip..... I've read where some suggest wetting out glass on poly and then trasfer to the plane part..... hasn't worked real well for me. I have better luck keeping my fibers straight if I align them on the part and then wet them out.... but that just might be me.
I would agree for larger layups, but for the small muti-layer reinforcements and such this technic is invaluable and per plans (cozy) in most cases.
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Old 06-17-2007, 03:37 PM
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Default Re: Seatback top done (sort of)

[quote=Jason Heath;49881]I hope that was suppose to be funny, it took less than a hour to do mine the conventional way.QUOTE]

Hmmm..... were you sanding in one hour?
The point here is that there are a lot of 1-2 hour opportunities to work on your plane during the week that will help you stay on track on your project as a whole so use the full spectum of opportunities that MGS offers with the compatability that the hardener (both slow and fast) has to offer.

And keep posting your progress Coolamber! It's always good to know who is at about the same stage in their project. You can PM me anytime. I would be glad to offer any assitance I can.

Now ...... back to the shop! I want to have chapter 6 wrapped up before the next EAA Chapter meeting!
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Old 06-17-2007, 03:44 PM
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Default Re: Seatback top done (sort of)

I thought this might be a good place to ask a question about micro. How much should I be applying to the surface of the lay-up? Should it be scraped completely off the part then apply the glass or left thicker? Is it supposed to completely fill the pores of the low density foam?

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