Bubblesw, bubbles, everywhere

[aviator_edb]

Thanks for the tips on my earlier question on the flox fillets. I have another issue. I'm still wrapping up the seatback (actually, my second seatback) and am still having troubles with small bubbles showing up.

 

I did the 2 ply UNI layup on the front and wetted things out. then went about working out bubbles. I "thought" I had them all but this morning I went to look at my handywork and found a lot of tiny bubbles all over the place. I think I'm still within the inspection standards but I'm a little concerned. I really took extra time to "get them all" and thought I had. Either I went blind during the layup or these bubbles came up after I stopped.

 

My shop temp stayed pretty constant at about 75F throughout the night. I did not use 'plastic peel ply'. My plastic is too thin and stretchy. I need to get some thicker stuff from the 'Depot'.

 

I was wondering if the problem is my micro slurry prep on the foam. Would a too thin mix cause something like what I'm seeing?

 

Call me frustrated in Massachusetts.

[TMann]

I was wondering if the problem is my micro slurry prep on the foam.

 

If you want another technique to see if this is an issue, try hardshelling.

 

Apply your micro and let it cure. Sand it and proceed as you would.

I vacuum bag quite a bit but I still use this method even for the parts I don't bag.

[argoldman]

If you want another technique to see if this is an issue, try hardshelling.

 

Apply your micro and let it cure. Sand it and proceed as you would.

I vacuum bag quite a bit but I still use this method even for the parts I don't bag.

 

If you band-aid now, you may do it on a later more important lay-up.

 

!!!!!!!!Find out why you are getting the bubbles!!!!!!!!!!!!

 

How about sending a good picture of the bubbles that you are getting.

 

When mixing micro for glass over foam, the thickness of the mixture is determined by the type of surface that the micro gives you. The more porous the surface, the thicker the micro. The purpose of the micro is to fill the surface voids, with a material lighter than pure epoxy.

 

It might be a good idea to go back to the instructions and try to produce a small piece (ie bookend) using the same material.

 

Bubbles can be caused by several factors, and without looking over your shoulder anything I say might be conjecture. But here goes:

 

If when you mix your epoxy, you incorporate bubbles (usually when mixing cold epoxy) these may stay after you incorporate the micro.

 

When you mix your micro, the mixed epoxy should be clear (color determined by the brand). The micro should then be incorporated in small increments.

 

Are you mixing the epoxy properly and for the right amount of time? Different epoxies require different mixing times.

 

Try making a pure epoxy layup of 2 layers of glass on a flat surface use plastic to keep it from sticking (no foam), using the exact same mixing technique as you used previously If you still get the bubbles, it is in you epoxy, either the mixing or the material.

 

On the other hand, the bubbles you are getting may be caused by your technique in squeegeeing the micro.

 

Try to find a builder near you and get some dual

[Kent Ashton]

Several reasons for air in the layup:

1. Not enough epoxy. This can be a "new guy" problem caused by trying to keep the layup too light (and too dry). Use plenty of epoxy initially and squeegee off the excess.

 

2. Sufficient epoxy is used but air isn't squeegeed out of the layup. There is always some air trapped in the layers and fibers when the epoxy is laid down. Gentle use of the squeegee works it out.

 

3. Over squeegeeing. The glass is sort of springy and if you squeegee too aggressively, it squeezes too much epoxy out of the glass, the glass springs back and sucks up air between the fibers.

[Edge 513]

Are you using the old stippling technique? I do and have no bubbles, unless I missed my wetout time with too fast of a hardener mix and need to work it with a hairdryer. Most resins, I use a 50/50 mix of slow and fast hardener with the 385 MGS. Typical micro on foam should be a milkshake consistency.

 

I dont use a "hot-box" I just use the air temp which should be about 80 degrees MINIMUM, in my book. I really like 85 degrees for lay-up work and the cure timeline. I found the shop should be that temp for a few hours prior to the lay-up work. It does no good to put resin or micro down on relatively cool foam or glass tie-ins...it just cools down to that surface temp very quickly like a heatsink/coolsink. A hair dryer, not a heatgun is also helpful sometimes in getting flow, once the resin is being worked into the fabric. A final creditcard wipe to remove excess resin and then apply peelply, and maybe some added resin on top of the peelply is needed.

 

Some small parts I have not peelplyed. All of this is really from chapter 3, so it is really old school, but it does work well, and produces nice work. At least a few thousand planes have been built this way, so I think I am in good company. Good luck!

Thats my .02 FWIW

[Lynn Erickson]

 

 

 

I did not use 'plastic peel ply'. My plastic is too thin and stretchy. I need to get some thicker stuff from the 'Depot'.

 

 

 

Call me frustrated in Massachusetts.

just to make sure you understand the peel ply is not the clear plastic sheet that you get from home depot. peel ply is a Dacron fabric that is used to cover the surface to hold down the edge fibers and to make a bonding surface for future layups.

[steve]

on my seat back it looked like i had lots of air.

it turned out to be epoxy bubbles.

as my wet layup was squeegeed out, it mix with the micro.

if you have a old dry scrap, try looking under the layup.

on the brite side, your seat will be just fine as is:D

but do find out whats going on !

[longez360]

Lay up 100% per plans. Problem solved.

[Neverquit]

if you have a old dry scrap, try looking under the layup.

 

if you have a layup done on a scrap piece how do you look under it?

on my seat back it looked like i had lots of air.

it turned out to be epoxy bubbles.

 

Steve, do your build in the proper order. The seat back layup is much easier outside the fuse. : ))

[steve]

if you have a layup done on a scrap piece how do you look under it?))

bend at the knees

 

Steve, do your build in the proper order. The seat back layup is much easier outside the fuse. : ))

my plane is dyslexic ...not !me

[aviator_edb]

Ok. I am still getting these "bubbles" in my practive layups and it's starting to make me insane. If you zoom in on the photo and look about the ruler you'll see what I am talking about. Are these dark spots air bubbles? I've got a very small number (less than 0.5 in^2 TOTAL) of other bubbles that I'm sure ARE air. They are much lighter in color.

 

Sorry for the large size. It's the only way to really see what I'm talking about..

 

[longezdave]

It is hard to tell from a picture, but it looks like you haven't done enough sgueegee work. Although it looks like you have bubbles, you also have a very wet layup there. Your parts are going to be heavy. Have you trimmed the practice layup to the specified size and weighed on a good scale?

[Cozy1200]

I don't recall ever having air in a layup that showed up at black spots. Possible contamination?

[TMann]

I don't recall ever having air in a layup that showed up at black spots. Possible contamination?

Agreed ..... what are you using for brushes?

I wonder if that might be the source but it seems like particles of some sort .... not bubbles.

[steve]

i think its mico pin hole, if the mico is to thick and you blade it on then remove as much as you can, you are left with the fruits of your labor and in your case not all the fome was filled. then you got it wet with epoxi and the epoxi filled the holes giving you the look you see in the pic.YMMV

try a layup with thiner mico (creamy penutbutter) and i think(baring what others has said) it will go away

[aviator_edb]

hrmmm, many good thoughts. thanks.

 

I'm using the regular 2" chip brushes from AS&S. I wondered if some of my problem could be the slurry and maybe I was just seeing pure expoy all the way to the foam. It would explain why stipling didn't do anything. IF this is what they are then structurally they aren't really a problem are they? It's just some added weight in epoxy?

 

 

Dave, yah, I noticed the VERY overwet areas after cure. I've already made note to pay better attention. For this pracitve layup I was concentrating on bubbles more than anything else.

 

Thanks for all the ideas fellas.

[TMann]

Chip brushes should be fine,

 

If you want to rule out the slurry as the culprit try this:

 

Slurry the part with a fairly dry micro mix.

Let it cure. (I usually the fast epoxy for the slurry step.)

Sand it and then apply your glass.

 

It's a step called hardshelling. This could help you rule out an element of your procedure.

 

I have used this method throughout my project.

[Big Steve]

Since when is "Hardshelling" considered an approved building method by any of the Canard Designers? You aught to let nobs know this before telling them to do it. STeve Not hardshelling on

[aviator_edb]

I think TMann's idea is a good one to use on another practice piece. If I DON'T get the dark spots then it's a good bet that they issue IS my slurry setup or somethign I'm doing to upset the slurry during wetout.

 

If I still get the spots then it's something else.

[TMann]

Since when is "Hardshelling" considered an approved building method by any of the Canard Designers? You aught to let nobs know this before telling them to do it. STeve Not hardshelling on

There has already been plenty of discussion here on the subject.

Also, while I use it as part of my vacuum bagging procedure ( which also was never considered an approved method) I did stipulate in the post that one could use this method to eliminate the slurry process as 'the culprit' in the problem that was presented.

 

The post adresses a methodology to troubleshoot the problem.

[Phil Kriley]

It almost looks like cinders from a coal furnace - any chance there is something falling from the ceiling of your workshop? If you peel-ply everything, it will help give you a more uniform appearance and overly wet areas will be very obvious - it will also protect your layup from whatever is contaminating it. I would not reject that part, but you are doing the right thing in trying to find the root cause.

[aviator_edb]

I'm pretty sure it's not contamination but I won't rule it out. It would have to be practically snowing crud in the workshop. I'm pretty good about keeping bugs, spiderwebs, etc cleaned up as well.

 

My shop heater blows over the worktable so I'ts possible that's moving somethig around. I'll redirect the output so it's blowing off the table inseat of over. Wont hurt to eliminate another possiblity.

 

I think I do another practice piece where I slurry and wet out the glass and then peel ply 1/2 of the layup. Then look closely at the difference.

 

thanks

[TMann]

..... another method to keep the part warm during the cure is to use an electric blanket. When I did my canard, I built a box out of 2 inch foam. Once I was done applying my epoxy and had the part in a vacuum bag, (you can cover it with a piece of poly) I draped the blanket over it and then put the foam box over that.

 

The temp inside was over 110 F.

 

Something to consider.

[argoldman]

I'm pretty sure it's not contamination but I won't rule it out. It would have to be practically snowing crud in the workshop. I'm pretty good about keeping bugs, spiderwebs, etc cleaned up as well.

 

My shop heater blows over the worktable so I'ts possible that's moving somethig around. I'll redirect the output so it's blowing off the table inseat of over. Wont hurt to eliminate another possiblity.

 

I think I do another practice piece where I slurry and wet out the glass and then peel ply 1/2 of the layup. Then look closely at the difference.

 

thanks

 

Hold it!!!!

 

Are you applying the slurry to the glass?????

 

A Big NONONONONO.

 

The Peel ply should have no real effect.

[aviator_edb]

Yikes, No. No slurry on the glass. I should've re-read my last post. Sorry about that.