Fiberglass resin not setting up on cowl

Mixed the Aeropoxy up and cut it with acetone, brushed it on, and it still feels tacky and looks greasy. Won't come off on the hand but it's sure feels sticky. Kinda like paint that is almost dry.

Time 48 hours - shop temp ~ 65 - 70F. And I know the proportions were correct because I mix by scaled weight to the gram.

One thought - because layer is so thin, it hasn't catalyzed yet because it couldn't develop the heat that a thicker layer could. Should I put a space heater in the room and run the temp up to about 90 overnight?

Got my lower lip stuck out because of the huge time invested in fitting the cowl.

What's up????

I think you are on the right track to apply more heat. Use the space heater idea, or even a shop light positioned close to the surface in question. No need to crank the whole room up to 90. Just get a heat source close to the surface.

My money is on it setting over night.

Regards,

The greasy feeling is probably normal.

I see this sometimes also.

From the West Systems website:

PROBLEM: Waxy film appears on surface of cured epoxy.

POSSIBLE CAUSES & SOLUTIONS:

Amine blush forms as a result of the curing process.

Blush formation is typical. Remove with water. See Special Preparation--Cured Epoxy in the User Manual.

Mark

A thin layer definitely cures slower. The easy way to get some heat on it is to simply set it in the sun for a few hours. It gets a lot hotter this way than in a heated garage.

Make sure you have both parts. I know this sounds silly but Spruce sent me a large and small container of part A. It wasn't until I mixed them and applied it to my cowling that I realized what had happened.

Aeropoxy was (is?) notorious for amine blush. My cozy is built primarily with Aero but when the blush would not stop, I switched to MGS ($$$) You can wash the blush it off with soap and water. The blush is usually not very thick but I have never cut epoxy with acetone either. You should be able to feel the epoxy hardened beneath the blush with the tip of your fingernail. High humidity makes it worse. Most of my work was done in Colorado and I still had blush issues with multiple batches of aero.

Ryan

As they say on the PGA Tour - "These guys are good". I went to the West Systems website and read about amine blush. It is the waxy like substance that forms on top of cured expoy. It is water soluable and according to one PDF file, the author felt it best removed by wet sanding because of eliminating the dust. He also stated that cured epoxy is just under the hardness of formica and can be felt under the amine blush. It is cured enough to cut with sandpaper after 24 hours and fully hardened after 48 hours.

Is it legit to say between the cowl and fitting the baffles that the front end of building an RV is such a pain in the fanny that is why it is saved for one of the very last things. If we had to do it first, there would be a lot less RV's flying and laying in parts in garages.

Webb
RV7A
N32WW

Blush

Webb said:

As they say on the PGA Tour - "These guys are good". I went to the West Systems website and read about amine blush. It is the waxy like substance that forms on top of cured expoy. It is water soluable and according to one PDF file, the author felt it best removed by wet sanding because of eliminating the dust. He also stated that cured epoxy is just under the hardness of formica and can be felt under the amine blush. It is cured enough to cut with sandpaper after 24 hours and fully hardened after 48 hours.

Is it legit to say between the cowl and fitting the baffles that the front end of building an RV is such a pain in the fanny that is why it is saved for one of the very last things. If we had to do it first, there would be a lot less RV's flying and laying in parts in garages.

Webb
RV7A
N32WW

Click to expand...

Say it ain't so Miss Scarlet, but you may be on to something there. If not familiar with fiberglass it can be a real pain in the potankas. Wet sand the blush after allowing to fully cure for 24hrs. Use some 320 or 400 W/D and plenty of water. Try washing it down afterwards with some mild soapy warm water(dish soap without amonia in it) and then just rinse it off with clean warm water. Should be warm enough in MS to take it outside and hose it off. A really good fiberglass site is http://www.fibreglast.com/, great products and excellent FAQ section. Are you trying to eleminate pinholes? Look as some of their products designed for this, also high build high solid primers will take care of the little stuff if fiberglass preped properly. Carefull with sitting fiberglass in sunlight. UV can damage most raw fiberglass and products. Read the warning labels.
Good luck,
Mike H 9A/8A

I've had good luck with Aeropoxy

I just used Aeropoxy (PR2032) laminating resin to make some reinforcements as I replace the hinges on my -4 cowl. I switched from West as I am too tired of dealing with amine blush. To date, I have seen no signs of blush with Aeropoxy. I agree with previous posters that heat and time cures most everything. Although I have not checked with Aeropoxy, most resin manufacturers recommend against thinning their resins. Aeropoxy has good tech help and may be able to help you with this issue.

Hummmmmmm

For what its worth.........aircraft spruce sold a vinal ester resin back in august of 07....since then they changed and the stuff they are sending now is mixed differently. Do you think they said something...NOT.

Amine Blush Removal

Here are the results of getting this @^@%$@%@#%$ off.

Scrub down with Dawn - Didn't phase it. Although it is supposed to be water soluable, got news - it doesn't wash off.

Wipe with acetone after a scrub down, 50% reduction in sticky.

Water sand - 90% reduction in sticky. Much better but can't tell how smooth due to water ripples.

Dry sand after wet sand. Perfect with no sticky.

Bottom line. If you have an amine blush, get out the hose and wet sand. Allow to dry and then finish up with some dry sanding to catch any irregularities in the epoxy.

Glad I only tested this on the top cowl outside. Due to the time constraints, I've ordered Loehle's aerocoating which fills in the pin holes. Sand it, rub in on, wipe if off after dried, and shoot paint. Will use on the top instead of a second round and once on the bottom.

We all learn from others issues. Take note builders - bypass the thinned epoxy and spend 50 bucks on the Leohle product and be ready to paint in 1 hour. My time is worth more than the cost of a quart of space age filler.

Webb
RV7A - N32WW

All of the race shops here in Indy that I've been to that do composite work exclusively use Shell 862 epoxy resin. Its not uncommon to see a 55 gallon drum of this stuff in the corner. Its half the cost of West Systems, longer pot life, and wets out better. A friend of mine gave me a gallon of this stuff out of his drum and some hardener and I won't go back to West Systems. Not as convenient to mix up as the West Systems but I do like it better.

www.avtcomposites.com is the local supplier...

Webb,
Based on your description of the removal process, you had uncured epoxy, not amine blush. Two possibilities:

Did you ask anyone at PTM&W about thinning Aeropoxy?

Which hardener did you use? There are three choices, and two of them do not fully cure without additional heat in the case of low mass applications:

http://www.ptm-w.com/dynamicdata/data/docs/aeropoxy pr2032 bulletin.pdf

It is an designed property, probably to lower the chance of exotherm in thick structural layups. All epoxy is not the same, just like all aluminum is not the same. It is important to read the technical material.

Acetone

Have been around a fair number of composite builders and never heard of anyone "thinning" epoxy with acetone. Never had a need to. What do the manufacturer's say about this?

DanH said:

Webb,
Based on your description of the removal process, you had uncured epoxy, not amine blush. Two possibilities:

Did you ask anyone at PTM&W about thinning Aeropoxy?

Which hardener did you use? There are three choices, and two of them do not fully cure without additional heat in the case of low mass applications:

http://www.ptm-w.com/dynamicdata/data/docs/aeropoxy pr2032 bulletin.pdf

It is an designed property, probably to lower the chance of exotherm in thick structural layups. All epoxy is not the same, just like all aluminum is not the same. It is important to read the technical material.

Click to expand...

Dan.
I did have a hardened epoxy layer below the layer but I agree with you. It didn't fully cure. I will do a complete watersand scrub tonight and pretend it was a bad dream and start over. I'll just chalk it up to a bad day. Luckily, this is recoverable and will take a only a bit of time to fix - Not hours.

I'll check out the hardener when I go back out to the shop.

I tried the acetone mix with West; it took 48 hours in a heated garage to have a semblance of curing. That was my only attempt at using the acetone. It never really seemed to fully cure even after 3 full days.

I switched to using full strength coats with heat applied to assist the flow. My 1st coat was stippled in with a short bristle brush and then squeegied in to ensure I filled the pin holes. The second coat was applied with a brush (painted on, not stippled) while green.

After 24 hours, the epoxy was good-n-hard. Took the cowling to the tub and scrubbed it with dawn and a green scrub pad (it takes a lot of elbow grease) and it was ready to sand.

No pin holes.

As for amine blush being water soluble...maybe it is but in my experience, that's akin to saying an ice berg will melt in 32.1 degree water. While accurate, I wouldn't get my hopes up on it being quick and easy.

Jekyll

<<I'll check out the hardener when I go back out to the shop>>

If you order a quart kit from Spruce, they send 3660 hardener. You would need about 100F to cure it in a thin surfacing layer. Adding acetone would lower surface temperature initially because of the rapid evaporation rate, which would also condense water vapor on the surface if humidity was moderate to high. That would worsen an amine problem. I have no idea what acetone does to the chemistry, but figure if acetone was good they would have put in there to start with <g>.

I'd suggest System Three ClearCoat if you want a brush-on water-viscosity epoxy for pinholes and surfacing. Good method for small parts like scratch- built gear leg fairings and tail tips.

West with fast hardener works very well using a 3-coat squeegee method at about 1 hour intervals. Slop it on and spread it around. Squeegee off all you can get while holding the squeegee kinda flat. Good method for large panels.

I'll be shooting a primer check-coat on a bunch of parts in the near future and will report on some method and material combinations.

Webb said:

snip

Time 48 hours - shop temp ~ 65 - 70F. And I know the proportions were correct because I mix by scaled weight to the gram.

snip

What's up????

Click to expand...

Maybe someone mentioned it, but I didn't see it. Most epoxies are mixed by volume, not weight. Perhaps your system says to mix by weight?

Amine blush will wash off with soap and water quite easily, so I agree with a couple others who have said you have some under curing going on.

Alex, the epoxy I have has mixtures for weight and volume.

Cleaning up my mess

Got to tell you guys that I think that everyone is a bit right here.

I have a bit of amine blush. It does come off easily with wet sanding. It doesn't wash off worth a darn.

I have some uncured expoxy but did put a space heater blowing directly on the cowl. After wet sanding, I can see some irregular areas of hardened epoxy.

I used the hardener that was the 3660 not the 3630 and slow to harden. Verified what was printed on the can. You can bet the farm that I will order the other hardener for some of the other jobs. I would like to paint the inside of the cowl with a coat since oil does get there and it would make for easier cleaning.

I can tell you what I'm going to do. I am going to wet sand and get that junk off. I will then dry sand to make sure that it is smooth. I will then use the Wonderfil product by Loehle which I tested out on a piece of lower cowl. Rubs on like paste wax. Allow to dry, buff off, and then shoot with primer.

I will also cuss like a sailor during the whole process, have a huge belly laugh, scream just a bit, drink at least a beer or two, and then smile from ear to ear because when I'm done, I'll be almost finished and thinking about how close I am to not renting those tin cans that you always wonder if they'll make it for one more flight.

What a PITA but what the hey. Ending the day on a good note, the airport manager called today and they have a T hanger for me on May 1st. I've been on a waiting list for over a year and the timing is perfect.

One last thing - I have to tell you folks that I really appreciate the help and the fact that it was handed out without kicking a guy when down. One very good thing that this will have helped someone not go down that road.

Thinning

Webb,
Found the info on an Epoxy site by the G. Bros.:

Does thinning epoxy make sense? In some situations, thinning is appropriate. In others, it is not. We feel that in most circumstances using heat to thin epoxy is preferred to using solvents. As long as the epoxy does not overheat during cure, the full physical characteristics of the cured epoxy remain. Adding solvent is a quick, simple method of thinning epoxy, but the strength and moisture resistance of the cured epoxy are significantly reduced.

It's my understanding that you should not cut epoxy resin with acetone. There was an article or discussion on this some time ago on pinhole filling with epoxy resin.

I'd recommend a different technique in future: Heat up the cowling using an electric heater and a 'tent' over the cowling (don't start a fire). When the cowling is warm, mix up some resin and brush it on. The warm cowling will cause the resin to flow out nicely, then accelerate the cure later on.

As the cowl cools, the (warm) air in the pinholes will contract, drawing resin in.

That's the theory. The alternate theory is that pinholes pop in and out of existance spontaneously due to the zero point energy of the universe.

Vern

Aeropoxy

Never liked aeropoxy. I used it to build a canard once. Always had the amine blush problem. Now I use Jeffco and never have a problem. Not even when its cold or humid. Don't over think it. Its just fiberglass. Sand it off, redo it if it bothers you.

I have heard Jeffco has been purchased by someone and the phone is disconnected. Is the factory still in business? Can you get the same product from the new company?

Anyone know who took them over.

Coupla things!!!

Dan hit most of the stuff but at a coupla things!!

If you are in a cool climate, keep the epoxy in warmer area during this time. House room temperature works.

Be sure of the epoxy and hardener you have. Many don't look at this and end up with hardener they didn't expect and then use incorrectly. (See Dan's post again)

In my opinion, thinning any brand 50% is waaaaaay over kill. Personally, I use West Systems for virtually all aspects of RV work. When necessary to thin, I use denatured alcohol and only a little and never more than 25%. Never had an issue so far.

Solutions to your problem. One, heat the part. This should work in a day or two. I agree with Dan that you don't have blush, you've got uncured epoxy.

Another possibility is to put a "hot mix," over the existing layer. Mix some epoxy with a few extra drops of hardener and minimal thinning. Make sure this epoxy is in the design use range. Apply and heat the part.

Bottom line, know the epoxy and hardener you have. Avoid thinning if you can. Mix in proper temp range, use heat as necessary.

Good luck and keep us posted.

Jeffco

Yeah I heard they changed names. Check with Lancair. They sell the stuff I used and still use. They have a medium and fast hardener. Another epoxy I tried and like that has the same qualities as jeffco is Epiglass ht9000. You get it from Interlux or Westmarine. The wet out properties are awesome and you can mix the hardeners to get the cure rate you prefer. Good stuff but expensive.