I am using West System 105 Resin, 205 Fast Hardener, and 406 filler. I am building up the rim around the door opening. Most of the mixture stays put where I place it. A few spots it wants to run and no matter how often I push it back into place it runs again. The other areas do not run. Is it because I 'played' with those areas that run more than I 'played with the areas that do not run? Is there something I can do to prevent the runny areas? Those runny areas are wasted and painful to clean up.
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Epoxy question
- Thread starter dspender
- Start date
Dennis, I am by no means the glass expert here, but I happen to be working with West Systems micro right now doing some cowl repairs. You should mix the 406 microballoons to the consistency of peanut butter, according to West. It will get a little sticky, but just apply it like you would frosting on a cake. It might take a couple of applications, one to fill the void and one to smooth out for a final finish. If you do a second application, be sure to sand the first one after it sets up. I use the tongue depressors available at the medical supply place. If you can use a plastic applicator, the micro will not stick to it as bad as with the wooden tongue depressors. It sounds like you're not getting it thick enough if it's running on you. Should not run at all if you have it at the proper consistency. Takes a lot of micro in the mix. Add it in small quantities until you reach the peanut butter stage. Hope this helps.
try adding some of this
http://www.aircraftspruce.com/catalog/cmpages/cabosil.php?clickkey=107520
it makes the mixture NOT flow. I was going to say thixotropic, but that just sounds pretentious.
==dave==
http://www.aircraftspruce.com/catalog/cmpages/cabosil.php?clickkey=107520
it makes the mixture NOT flow. I was going to say thixotropic, but that just sounds pretentious.
==dave==
when adding the filler I make the mixture as thick or thicker than peanut butter.Most of the mixture stays in place and does not run however a few spots run as though it was less thick however it all came from the same batch. That is what is confusing to me. Why is some runny and other parts do not run all out the same mixing bowl.
Peanut butter consistency can still be a bit vague for some people....
The description used multiple places in the construction manual is to add thickener a little at a time until when you tilt the cup 90 deg on its side, the mixture does not move/creep.
This will give you a mixture that is as spreadable/workable as possible, but will not sag/run.
The description used multiple places in the construction manual is to add thickener a little at a time until when you tilt the cup 90 deg on its side, the mixture does not move/creep.
This will give you a mixture that is as spreadable/workable as possible, but will not sag/run.
The mixture I have made does not run even when I invert the mixing container and shake the container the material will not run or fall out of the container. It doesn't move unless I physically move it with a tongue depressor or Puddy knife. Yet after it is applied to a surface most will stay in place and not move at allbut a few areas will run slowly and require a continual nursing care to keep it in place.
It might be a surface prep. or surface contamination issue.
Put clear packing tape over the epoxy and shape it. Even peal-ply taped to hold it in place. If it sticks, it is easily sanded off. You will not get a perfect finish, but sanding and a second or third coat will get you what you want.
West 406 is 100% fumed silica, aka cabosil. It is rather odd to use it as a filler, as its purpose is to merely make epoxy thixotropic. In quantity large enough to have bulk it is heavy, and hard to sand.
West 407 or 410 are typical of surface fillers, the key ingredient being microballoons, which add volume without adding much weight. It is perfectly reasonable to combine mixed epoxy, microballoons, and silica to create a light, easy to sand, high bulk filler that does not run. Most of the West adjuncts are blends anyway. Expensive too, given that plain micro, silica, and flox are available at a small fraction of the price.
Silica tends to clump into a larger grain size which doesn't mix well. Borrow your wife's flour sifter, and run your silica through it from time to time.
To the OP's question, are the runny patches hardening at the same rate as the rest?
West 407 or 410 are typical of surface fillers, the key ingredient being microballoons, which add volume without adding much weight. It is perfectly reasonable to combine mixed epoxy, microballoons, and silica to create a light, easy to sand, high bulk filler that does not run. Most of the West adjuncts are blends anyway. Expensive too, given that plain micro, silica, and flox are available at a small fraction of the price.
Silica tends to clump into a larger grain size which doesn't mix well. Borrow your wife's flour sifter, and run your silica through it from time to time.
To the OP's question, are the runny patches hardening at the same rate as the rest?
I didn't realize 406 was cabo either for the reason Dan mentioned..... I buy micro, cabo, and flow in bulk for just a few dollars each.
I mistakenly assumed the OP was using micro.
Scott Hersha
Well Known Member
I've used flox or chopped cotton when I had to lay in something thick when gravity became a problem. Didn't have any sagging problems, but it isn't easy to sand. Sometimes you can use something to mechanically hold the material to shape while it cures - like peel ply and tape like others have said. If you do this and use a relatively dry light micro for the filet, consider applying a couple layers of wetted cloth over it after it has cured and been sanded, for strength and to prevent cracking.
rleffler
Well Known Member
Dennis,
I used strips of fiberglass to build up the door frame for use with the McMaster Carr door seals. Since the rain gutter was cut off, I wanted to add back more structural support.
On the flat spot that's traditionally located between the rear window and the door frame, I added fiberglass strips in a process very similiar to what the plans describe for the front window. Using different lengths strips, it was pretty simple to build the contour back up to where it supposed to be.
It was pretty quick and easy to build the frame up to the proper thickness with the glass strips, then just use a bit of micro to make it cosmetically smooth. It will then be much stronger than just using micro.
Bob
I used strips of fiberglass to build up the door frame for use with the McMaster Carr door seals. Since the rain gutter was cut off, I wanted to add back more structural support.
On the flat spot that's traditionally located between the rear window and the door frame, I added fiberglass strips in a process very similiar to what the plans describe for the front window. Using different lengths strips, it was pretty simple to build the contour back up to where it supposed to be.
It was pretty quick and easy to build the frame up to the proper thickness with the glass strips, then just use a bit of micro to make it cosmetically smooth. It will then be much stronger than just using micro.
Bob
az_gila
Well Known Member
West 407
Is West 407 Low Density Filler the same as this from Spruce, albeit a different color?
http://www.aircraftspruce.com/catalog/cmpages/bubbles.php?clickkey=10403
Is West 407 Low Density Filler the same as this from Spruce, albeit a different color?
http://www.aircraftspruce.com/catalog/cmpages/bubbles.php?clickkey=10403
If it sags the filler is too runny or you're probably putting too much filler in at one time. Try adding the filler in smaller amounts and building up the required thickness in 2 or 3 passes. Agree that micro is a better filler! If its a really large hole add some glass to support the filler otherwise it will crack off in time. If it keeps sagging, tape some foam over the filler to hold it in place, make sure the foam is covered in brown tape otherwise it will all stick together...
P
P
Nope.
The MSDS is probably easiest way to know what is in a West product. This is 407:
The "phenol formaldehyde resin" listing tells us the mix contains phenolic microballoons, which are not the same as glass microballoons. Phenolic micro has slightly lower density compared to glass micro, and some say epoxy/phenolic micro fill is easier to sand. On the other hand, phenolic is not water-resistant, and it costs 2~3 times as much as glass micro.
Perlite is a glassy volcanic rock that acts like popcorn when heated in processing. The result looks like coarse foam under a microscope. I think it's included in 407 merely as a cheap bulk filler with properties roughly similar to glass micro, except for a much lower crush strength. There is a form of glass micro made from expanded perlite; it is multicelluar rather than being a single sphere.
You already know about silica.
The Spruce link lists 3M glass micro at $9.85/lb. West 407 is something like $32 for 12 oz.
Cabosil
Take it from a plastic airplane builder (Glasair), the suggestion to add cabosil is the answer. It is, indeed, a thixotropic agent. That causes the mixture to form temporary bonds while wet. The mix will stay where you put it but you can move it around while wet. When you stop moving it the mixture stays. The cabosil particles are S shaped and hook loosely to each other when wet. Q cell (micorballoons) are glass spheres designed to be very light, easy to sand filler. Milled fiber (flox) is just that, ground fiberglass strands. Mixing MF with resin gives the equivilent of liquid fiberglass. It will bond strurctually but is very difficult to sand.
Buy the smallest amount you can. A little goes a long way. You will never use it all. It is cheap and will really help in your situation.
Take it from a plastic airplane builder (Glasair), the suggestion to add cabosil is the answer. It is, indeed, a thixotropic agent. That causes the mixture to form temporary bonds while wet. The mix will stay where you put it but you can move it around while wet. When you stop moving it the mixture stays. The cabosil particles are S shaped and hook loosely to each other when wet. Q cell (micorballoons) are glass spheres designed to be very light, easy to sand filler. Milled fiber (flox) is just that, ground fiberglass strands. Mixing MF with resin gives the equivilent of liquid fiberglass. It will bond strurctually but is very difficult to sand.
Buy the smallest amount you can. A little goes a long way. You will never use it all. It is cheap and will really help in your situation.
RV7Guy
Well Known Member
410
Dan got all the main points. I have the big tub of 410 that I use with West Systems and 5 minute epoxy. The only epoxy filler I use.
Regarding your particular situation, many of these fill situations will take several iterations to get it where you want. Mix the stuff thicker than you think, apply and use a finger dipped in denatured alcohol to shape.
You'll get it all figured out 'bout the time you are done
Dan got all the main points. I have the big tub of 410 that I use with West Systems and 5 minute epoxy. The only epoxy filler I use.
Regarding your particular situation, many of these fill situations will take several iterations to get it where you want. Mix the stuff thicker than you think, apply and use a finger dipped in denatured alcohol to shape.
You'll get it all figured out 'bout the time you are done
az_gila
Well Known Member
Dan got all the main points. I have the big tub of 410 that I use with West Systems and 5 minute epoxy. The only epoxy filler I use.
Regarding your particular situation, many of these fill situations will take several iterations to get it where you want. Mix the stuff thicker than you think, apply and use a finger dipped in denatured alcohol to shape.
You'll get it all figured out 'bout the time you are done
I'm working on a cowling with the West epoxies and these two descriptions on the West web site led to my 407/410 question -
410 Microlight? is the ideal low-density filler for creating a light, easily-worked fairing compound especially suited for fairing large areas. Microlight mixes with greater ease than 407 Low-Density filler or microballoons and is approximately 30% easier to sand. It feathers to a fine edge and is also more economical for large fairing jobs. Not recommended under dark paint or other surfaces subject to high temperatures. Cures to a tan color.
407 Low-Density filler is a blended microballoon-based filler used to make fairing putties that are easy to sand or carve. Reasonably strong on a strength-to-weight basis. Cures to a dark red/brown color.
When the boat guys warn on high temps. I started wondering about the suitability of 410 on our cowlings.
So, are the Spruce glass spheres mixed with West epoxy a good filler for use in fairly thick layers for our cowls? Better than either 407 or 410 fillers?
samray
Active Member
I've found micro or flox will creep on a sloped surface, even when mixed to a stiff consistency- especially if it's a thick layer- so I make a "dam" out of 3M heavy duty shipping tape to limit the movement. Some "pure" (epoxy) will get under the tape but it's relatively thin and easy to remove, especially if it's the next day. If you anticipate multiple layers to the build up, then using peel ply between layers makes the process much easier, especially if you dislike sanding like I do.
"Flox" is cotton. "Milled fiber" is fiberglass.
Avoid multiple build ups, as you'll rarely repeat the same ratio of epoxy to fill material. The result is different sanding densities, and often a wavy finished surface. Same goes for multiple materials. I've seen unpainted airplanes on which I could count 5 different fillers. The builder kept changing because somebody told him "X" was easier than "Y", then somebody came along and told him about "Z". As much as possible, stick with one filler, put it on thick one time, and sand/shape one time.
The temperature warning is probably because (if memory serves), 410 has a bunch of styrene in it. Check the MSDS to see.
3M glass micro is inert, cheap, and reliable. Thick layers are not a problem. Really thick (like more than 1/2") may cause the epoxy to exotherm, as hollow spheres are a good insulator. I've used it for castings at least that thick, and no, it doesn't crack either. Service temperature is limited only by the epoxy, as glass spheres don't care. Being inert, they also work fine in vinylester or polyester resin.
Raw layup:
Filled, shaped, sanded, sealed:
Final sanding, then epoxy primer, last check for flaws:
Avoid multiple build ups, as you'll rarely repeat the same ratio of epoxy to fill material. The result is different sanding densities, and often a wavy finished surface. Same goes for multiple materials. I've seen unpainted airplanes on which I could count 5 different fillers. The builder kept changing because somebody told him "X" was easier than "Y", then somebody came along and told him about "Z". As much as possible, stick with one filler, put it on thick one time, and sand/shape one time.
The temperature warning is probably because (if memory serves), 410 has a bunch of styrene in it. Check the MSDS to see.
3M glass micro is inert, cheap, and reliable. Thick layers are not a problem. Really thick (like more than 1/2") may cause the epoxy to exotherm, as hollow spheres are a good insulator. I've used it for castings at least that thick, and no, it doesn't crack either. Service temperature is limited only by the epoxy, as glass spheres don't care. Being inert, they also work fine in vinylester or polyester resin.
Raw layup:
Filled, shaped, sanded, sealed:
Final sanding, then epoxy primer, last check for flaws:
Last edited:
pa38112
Well Known Member
I have observed the phenomenon described in the original post. I have always believed this to be from the filler separating when "played" with. It appears similar to concrete where you can get the water to float to the top by patting on it. Properly filled and mixed epoxy will still develop a wet puddle when you try to touch-up an area while it is still uncured.
az_gila
Well Known Member
I talked with the West Systems people. They aren't sure why I experienced some sag in some areas, even from the same batch of mixture. They suspect that I didn't add enough filler; was lucky not all sagged, but only some did. They recommended I could use duct tape to 'dam' up the sagging areas until cure. All things many of you suggested.
I built up the lower cabin edge to match the door better. In some areas I had cut it back so far I needed to build it up almost 3/8". I placed two layers of cloth under this area in the event someone bumps or steps on it. They said probably not necessary, but not a bad idea.
They thought 406 was a good filler to build up areas and they recommended 407 to 'fair' those areas. The 407 sands easier. Again, all things many of you suggested.
I asked them 'What is fairing'? They said after a lay up, some areas show valleys between high areas and those valleys 'are not fair'. Those valleys should be filled in and they recommended 407. I don't know if that is the official meaning of fairing, but it served as a word picture and helped me understand the concept.
Thanks to all for walking me through this process. Will post again when I encounter another issue. Happy New Year.
I built up the lower cabin edge to match the door better. In some areas I had cut it back so far I needed to build it up almost 3/8". I placed two layers of cloth under this area in the event someone bumps or steps on it. They said probably not necessary, but not a bad idea.
They thought 406 was a good filler to build up areas and they recommended 407 to 'fair' those areas. The 407 sands easier. Again, all things many of you suggested.
I asked them 'What is fairing'? They said after a lay up, some areas show valleys between high areas and those valleys 'are not fair'. Those valleys should be filled in and they recommended 407. I don't know if that is the official meaning of fairing, but it served as a word picture and helped me understand the concept.
Thanks to all for walking me through this process. Will post again when I encounter another issue. Happy New Year.
flyingriki
Well Known Member
From West
Final Fairing
Fairing is the process of creating or shaping a smooth line, edge or surface, free of hollows
or bumps. In traditional boatbuilding, fairing is first employed during the layout
of the many individual lines of the boat on the lofting floor, or on the less traditional
computer aided design (CAD) program. Each line is described by a series of plotted
points. If one or more points is out of place, the line will not be true or accurate. If the
line connecting these points does not flow smoothly or continuously, the line will not
be ?fair?. Lines must be both true and fair. Plotting the points accurately requires careful
measurement with a ruler, but the smoothness of a line flowing through those
points is often best measured by eye. This is the conjunction of science and art in
boatbuilding.
Final Fairing
Fairing is the process of creating or shaping a smooth line, edge or surface, free of hollows
or bumps. In traditional boatbuilding, fairing is first employed during the layout
of the many individual lines of the boat on the lofting floor, or on the less traditional
computer aided design (CAD) program. Each line is described by a series of plotted
points. If one or more points is out of place, the line will not be true or accurate. If the
line connecting these points does not flow smoothly or continuously, the line will not
be ?fair?. Lines must be both true and fair. Plotting the points accurately requires careful
measurement with a ruler, but the smoothness of a line flowing through those
points is often best measured by eye. This is the conjunction of science and art in
boatbuilding.
az_gila
Well Known Member
<snip>
Filled, shaped, sanded, sealed:
Final sanding, then epoxy primer, last check for flaws:
Dan,
Is that just a coat of raw epoxy as a sealing layer?
flyingriki
Well Known Member
Quote:
What have others used?
I use plain mixed epoxy. The local GKN facility uses epoxy/cabosil, as does a prototype guy I interviewed recently. Some folks like polyester fillers, others try to fill with urethane high-build, and apparently a few use drywall mud.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
What have others used?
I use plain mixed epoxy. The local GKN facility uses epoxy/cabosil, as does a prototype guy I interviewed recently. Some folks like polyester fillers, others try to fill with urethane high-build, and apparently a few use drywall mud.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
