Gelcoat help needed...

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#1

After sealing (FMS Sealer) and waxing with TR-102 regular mold release wax (10 coats, 1hr between coats) I sprayed the PE tooling gel coat today. Why didn’t the gel coat lay down and flow out to a smooth coat??? What did I do wrong? Here are the steps that I followed (hopefully you guys can tell me what I need to do differently to improve the results).

[FONT=Calibri]1. [/FONT]Ambient temp this AM was 94 degrees (Arizona)
[FONT=Calibri]2. [/FONT]Installed the included FN-6 nozzle in my new G-100 dump gun - spray volume adjusted nearly all the way closed
[FONT=Calibri]3. [/FONT]Adjusted the air pressure (filtered) to 70-75psi continuous at the gun (this is the max I can get when running through my current regulator)
[FONT=Calibri]4. [/FONT]Mixed my orange tooling gel coat with duratec high gloss additive (4:1 approx)
[FONT=Calibri]5. [/FONT]Catalyzed with MEPK at 2%
[FONT=Calibri]6. [/FONT]Sprayed via steady sweeping passes approx 18-24 inches away from the surface of my plug (spray pattern at an approx 70 80 degree angle to the plug - nearly vertical)
[FONT=Calibri]7. [/FONT]Sprayed one med heavy coat (I noticed a few fish eyes in areas that the spray pattern was light – as in where I didn’t fully overlap the last pass) – I hit the fish eye areas again and they filled in
[FONT=Calibri]8. [/FONT]Waited approx 5 min and sprayed another med heavy coat
[FONT=Calibri]9. [/FONT]Total thickness was approx 30 mils (on the low flat areas – the gator looking ridges would have been thicker)
[FONT=Calibri]10. [/FONT]Waited approx 30-45 min and applied two (2) layers of light weight veil (CSM) and VE resin
[FONT=Calibri]11. [/FONT]Waited until that kicked off (waited until the stuff cooled to near ambient following the exotherm – max BTW was approx 135 degrees)
[FONT=Calibri]12. [/FONT]Applied the first two layers of 1.5oz CSM and [COLOR=black]Iso-phthalic PE tooling resin (404 tooling resin from US Composites) – Catalyized at 1% - the laminate reached a peak exotherm of 142-145 degrees[/COLOR]

NOTES:

I noticed the spray pattern with the G100 was only 3” wide or so at 18-24" from the plug.

I called US Composites and the rep that I spoke to said I should have thinned the gel coat at 10-15% with styrene (had some too, just didn’t think of using it). He also said I should have waited 15 min before applying the 2nd coat and then a couple of hours before applying the veil

I’m hoping the molds will be salvageable (I really hope I don’t have to start over but….)

Should I continue bulking up the mold with 1.5oz CSM and hope the gelcoat against the surface of the plug is smooth or do you think the severe wrinkly look in the pics is going to ruin the mold?

(pics below - the 3rd pic is after the two layers of veil had been applied - looks dry but its not)

Any advice will be much appreciated!

James
Phoenix, AZ

http://i1095.photobucket.com/albums/i477/jbocek/Glasair%20project/IMAG1039.jpg

http://i1095.photobucket.com/albums/i477/jbocek/Glasair%20project/IMAG1034.jpg

http://i1095.photobucket.com/albums/i477/jbocek/Glasair%20project/IMAG1042.jpg

#2

I hate to say it but I’m guessing this one is a loss. When I spray here in AZ I usually thin the gel around 15 to 20% with acetone, but I use a HVLP gun and in 100 deg I’m sure most of the acetone evaporates off before the gel starts to build up. You should be able to lay a couple good coats and then finish it off about 15 min later. Also I typically wait overnight before adding any resin onto the gel.

#3

Note that the “aligator’ish” looking ridges are actually thicker areas of gel coat so the min thickness is approx 30 mils whereas the “ridges” are thicker… This being the case, wouldnt the surface (against the plug) still be smooth and usable??

#4

Anybody else??? (please see questions in my original post) Am I screwed (need to start over)? Also, a few additional questions:

  1. What tip size should I be using when spraying PE Gel Coat? (my G100 came with an FN6)
  2. Since my attempt resulted in thick gatoring in the gel coat would a smaller tip help to reduce the volume of material being sprayed and thus a smoother easier to control spray pattern? (Especially if I thin with 10-15% styrene as per US Composites tech line)
  3. What pressure should I be running at the gun (I’m running approx 70-75psi)
  4. How far should I be holding the gun from the object I’m spraying? (I’m 18 inches or so)
  5. Since I live in the desert with ambient temps ranging from 90-115 degrees this time of year, do I really need to catalyze at 2% or should I drop down to 1%?
  6. Should I be using different wax on my plugs? (I used TR-102 Regular release wax but today I read a post that suggested using TR-108 wax instead to help prevent the few fish eyes that I noted in my original post)

Thanks in advance for your help/advice!

#5

Run a small test that mimics everything that you did on this plug. Peel it off and see what it looks like.

#6

Is there any compelling reason to scrap a part in which the gel coat application looks as crappy as mine does? As per your post (wyowindworks) isnt the main objective/concern the quality of the gelcoat surface next to the plug. In other words will the uneven gelcoat cause print through of this uneven application to transfer to my parts that I will be building in the finished molds?

#7

I have no idea how your surface with be. You can either pull what you have done and find out, finish the mold and find out, or perform a test to determine whether you should scrap it or finish it.

If you don’t want to perform a test then rip off what you’ve done and have a look.

#8

A couple of things that jump my mind:

10 layers of wax??? A bit masochistic to my mind. In general, 2-3 layers is enough, especially when also using a sealer.

Why mix with high gloss additive? It thins out the gelcoat even more (hence the “waves” in the surface) but also makes the surface non-stick. Normally a gelcoat cures sticky, to ensure a good bond with the next layers.

Now that I am writing, another question pops up: Is your gelcoat a spray or a brush gelcoat? Polyester starts it life as a relatively thin liquid, which is thickened to make it into a spray gelcoat, or thickened even more to make it a brush gelcoat. However, the rheology of a spray or brush gelcoat is vastly different. A thinned down brush gelcoat does not have the properties a spray gelcoat has. (thin in spraycup, thick on part).

Adding acetone or styrene can help making a brush gelcoat pass a spray gun, and indeed a spray gelcoat contains acetone (usually) which evaporates from gun to part, but there are other additives (glycerene, aerosil) which are different.
Keep in mind that styrene eveporates less quickly than acetone, so the gelcoat will still be thin when on the mould.

I guess a thing to try is to dig up the technical datasheet of the gelcoat, and see what they suggest.

As for catalyst levels, yes, you can go lower, although 1% is on the very low side. Undercatalisation can lead to alligatoring when the next layer is applied, so keep that in mind.

As for fish-eying: It is an indication to me the gelcoat was too thin when it arrived on the part, which probably is due to the high gloss additive. (which really, you should not need)

Hope this helps…

#9

Here’s my two cents for what its worth, (if anything :slight_smile: ) Its annoying that this happened and to be quite honest, im not sure why. To me, addition of acetone or styrene surely only decreases the viscosity of the gelcoat while spraying to make it easier to spray, leaving a thinner coat, etc. Sounds like you know what you’re doing spraying, so would adding styrene have made a huge difference? (Edit…looks like herman beat me to it!)

Also, the ridges on the gelcoat - are they really a huge problem? This is a chopped strand polyester tool so Im guessing isnt going to be subjected to high thermal loads or used to make the very best structural parts. Fair enough, the ridges wont help conformity with veil and cloth, but sure thickness variations in CSM are preovlent, so does it really matter. Also, if it was me, I would lump on the rest of the backing structure, pull the mould off and see what it looks like. It looks like a small part made with lower cost materials so if it was me, I would lash on and see what it turns out like.
Hope you get it sorted anyway, keep the fingers crossed.

#10

Thanks for the feedback guys! I think I’ll proceed with bulking up the tool and see what I have after de-molding (fingers crossed!!!).

That said, I’d really like to figure out why my gel coat didn’t lay down smooth so here are a couple of points of clarification and questions (please let me know if you agree):

a. The “aligator’ish” looking ridges that you see in the pics appeared the moment the gel was sprayed on (as if the thick gelcoat “bunched up” from the high air pressure). Imagine laying down a nice smooth “heavy” coat of paint, then while still wet hitting it with high pressure air from close range… the paint would “ripple”… that’s the affect I think I’m seeing here. Do you think reducing the pressure on the G100 would help? If so, what pressure should I run?

b. Late last night I found an old post by TET (from 2007) in which he says he uses a #4 or #5 tip in his G100 for thinned down gelcoat. Again, logic tells me that using a smaller tip with thinned down gelcoat (or the right “spray” gelcoat as Herman mentioned) would certainly help the gelcoat “flow” after being applied. Note that mine didn’t flow at all… when the pressure (I think) caused the thicker gelcoat to bunch up and form the ridges you see in the pics, that was it… it didn’t move.

c. The high gloss additive was recommended by one of the techs at US Composites (also where I purchased the orange tooling gelcoat) – So then you guys just spray the gelcoat as it comes (no high gloss additive)?

d. Re the fish eyeing: I also found an old post from Brad1 (Jan 2012) in which he recommends using TR-108 wax to solve the fish eye prob (instead of the TR-102 Regular that I used). I’m going to buy a can and try it out for myself.

Again, I’m fairly new to all of this so any other thoughts, ideas or recommendations are GREATLY appreciated.

#11

I would guess that if the ridges and solid gel coat, you should be good. Gatoring would usually happen when resin is applied over gel that is either too soft or too thin.
I often use the same gel from US Comp and spray with no problems but do not add the high gloss. Without the high gloss the outer surface of the gel will always remain tacky so that’s why I wait a day. With the high gloss the surface will harden so you would need to begin the layup sooner.

#12

UPDATE: I had planned (per my last post) to proceed with the layup schedule and then demold in the hopes that the mold would be salvageable. Unfortunately, while inspecting the mold this AM I noticed some flex in the center of the mold laminates (when applying moderate pressure to the center of the mold with my finger I could see the mold flexing inward approx 1/8” or so – this of course meant the mold pre-released on its own in the center and the laminate/gel coat warped slightly leaving a gap between the gel coat/laminates and the plug). Result: I decided to scrap the mold and start over. The good news is the mold released like a dream… it just popped off with hardly any effort at all.

Back to the drawing board…. Ugh! So, I ordered more tooling gel coat, veil and 1.5oz CSM which should be here in a week or so. Now the question is how to best avoid making the same mistakes in the future. Here are my thoughts (I’m hoping some of the more experience members will chime in here and let me know if I’m on the right track or if I should follow a different procedure):

a. I ordered some dolphin wax (Feb 2007 post by wyowindworks) to hopefully avoid the fish eye prob) – The shop that I purchased from (H&M Racing) said I shouldn’t need to remove the existing TR-102 wax before applying several coats of dolphin wax (do you all concur?)
b. I ordered a #4 and #5 nozzle for my G100 dump gun. My gun came with a #6 nozzle. I plan on thinning the orange tooling gel coat by adding 10-15% (by volume) styrene so it will flow better when sprayed onto the plug (per recommendation by Steve at US Composites)
c. I’m going to try spraying the thinned gel coat with both the #4 and #5 tip to see which provides better control. I’m still at a loss on what pressure I should run at the gun (please chime in with any recommendations guys!).
d. First I will spray on a medium/heavy coat of the tooling gel/high gloss additive and let it kick off… 20 min? (unless you guys recommend a longer or shorter time between coats – note also that I’d like to add the high gloss additive as this is supposed to provide a much higher gloss mold surface AND reduce the porosity of the surface at the same time)
e. Second I will spray on a 2nd med/heavy coat of the tooling gel/high gloss additive to at least 25-30 mils total and let it cure for at least 4hrs (unless you guys recommend a longer or shorter time before applying the first veil layer of CSM)
f. Third, after waiting the appropriate amount of time (12-24 hrs???) I will apply a layer of veil CSM with VE Resin
g. Fourth, after waiting the appropriate amount of time (12-24 hrs???) I will apply the first two layers of 1.5oz CSM w/PE tooling resin
h. Fifth, I will continue to add 2 layers of 1.5oz CSM w/PE tooling resin at a time (no more than four layers per day???) until I’ve bulked up to ¼” thick or so (8 layers of 1.5oz CSM total)
i. Sixth, I will add my frame around the flange perimeter and let the mold cure for a week or so in my HOT hangar before demolding (is this enough time? Too much time?) – Its normal this time of year to have 100-115 degree ambient days and its usually 10-15 degrees hotter in my metal hangar so the molds will be “cooking” all day in 120-130 degree temps for a week.

Please chime in with any changes (timeframes or process) that you would recommend to the above as I really don’t want to have to start all over again…

Thanks in advance for helping me out!

Oh… BTW: Why do you think my first attempt pre-released? Do you think it was because I didn’t wait long enough before applying my veil and first two layers of CSM???

Pics of plug surface below:
http://i1095.photobucket.com/albums/i477/jbocek/Glasair%20project/IMAG1029.jpg

http://i1095.photobucket.com/albums/i477/jbocek/Glasair%20project/IMAG1024.jpg

#13

i use the G100 cup gun with spray gelcoat which is designed for spraying and is a lot thinner than normal gel, my gun came with a 6 nozzle so i bought a 5 nozzle which is 3.9mm bore and found this to be a little small so bored it out to 4.5mm and found it works well and is ideal for spraying smaller moulds. i spray at 45psi

#14

Again some remarks:

I hope you ordered spray gelcoat this time.

High gloss additive will make the exterior side of the gelcoat high gloss, it has nothing to do with the toolside. I think there is some sort of misunderstanding. Spraying with high gloss additive is only of advantage if you are spraying the final layer on a plug.
When doing the gelcoat for the mould, leave it out. Your gelcoat will stay sticky (cure inhibition) and this will help adhesion with the subsequent layers.
With high gloss additive (which is basicly a wax and a thinning agent) you risk debonding of the gelcoat when using the mould.

Time windows:
-read the datasheets, but in general you are good to go if you can press your finger on the gelcoat, it leave a print, but no gelcoat on your finger.

Also check gelcoat thickness. For optimal results it is relatively critical. Your prerelease very likely is due to too much gelcoat. (and shrinkage). Ask for a wet film thickness gauge. They should give them for free.

#15

When you released the mould, was the surface of the gelcoat triped?

#16

Okay so I have my new supplies on order… (BTW: Thanks for catching the gelcoat issue Herman… I had originally re-ordered more of the same orange tooling gelcoat from US Composites - the brush on variety and was going to thin with stryene. I just cancelled the brush gelcoat from US Composites and ordered spray Gelcoat from Fiberglass Supply in WA). I also cancelled the high gloss additive part of the order and will be spraying the gel as it comes (no high gloss additive as per Herman).

The tech at Fiberglass Supply had experience with the G100 cup gun and recommended using a #4 or #5 nozzle (I ordered those too) at 60psi. Stoddy (above post) recommended 45psi so I will test 45-60 psi and see where in that range works best. Fiberglass Supply’s website had a nice data sheet on the gelcoat which I’ve read and will apply as per said data sheet (two coats at 16-20 mils each… no more than 40 mils total for both coats and no thinner than 12 mils per coat). The gelcoat that I ordered from US Composited didnt come with a data sheet so I’m sure I applied it WAY too thick AND didnt wait anywhere near as long enough before applying the 2nd coat, 2 layers of veil w/VE & the first layers of 1.5oz CSM w/PE tooling resin.

Also:

  1. Am I overkill applying 2 x layers of veil with VE resin or is one layer enough? The last round I applied two layers of veil w/VE thinking I needed to do so to get an adequate exotherm.

  2. How long should I wait (after applying the veil/VE resin) before applying the first layer or layers of 1.5oz CSM w/PE tooling resin.

  3. Am I okay to applyng 2 layers of CSM at a time after the viel has cured? Should I be appying 3x at a time to get a higher exotherm? Logic tells me that I need at least 2x layers at a time to get an adequate exotherm (peak exotherm of the PE tooling resin was approx 145-150 degrees F with 2x layers of 1.5oz CSM)

  4. What is the optimal layup schedule for the bulking 1.5oz CSM (how many layers at a time? how long before applying the next layers?)

Remember my ambient temps are 100-115 F this time of year…

Thanks again for all the help/advice!

#17

Hi without knowing the details of your resin system and as its your first mould I would suggest an approach such as

Day one

1 first gel coat let it tack dry off 2-4 hrs approx
2 second gel let it tack dry off 2-4 hrs approx
3 laminate first layer veil with ordinary resin 1x 300 gram csm consolidate, let cure, leave over night.

Day two AM

Lightly sand surface to de nib any spiky bits in the morning then

4-5 layers of 450 grm csm with tooling resin (try not to over consolidate between layers as you want to build thickness) let exotherm
once cured sand de nib. You normally see a good change in colour of the resin as the exothermic reaction takes place.

I use an infer-red temperature gauge to monitor exotherm. Wait till the temp has fallen close to your ambient prior to starting the next batch of layers.

PM

4 layers again let cure.

Day 3

Add mould supporting structure. This would give a solid mould. If you wanted it lighter one you could think about leaving out the second batch of 4 layers and replacing thm with a 5mm core matt and 450 csm with VE resin.

I would just brush on the gel, spraying gel mixing in additives etc is all well and good but just adds to manyvariables when all you really need is a bucket and a three inch brush.

#18

Thank you for the response! Re the layup schedule, are you suggesting I apply (a.) 4-5 layers in one shot or (b.) 4-5 layers in a day, 1-2 layers at a time, wait until exotherm has coold to near ambient, then apply next batch of layers?

My plug is actually the lower surface of the wing on my aircraft so it cannot under any circumstances exceed the HDT for the VE resin used to construct the wing which is around 220 F as I cannot afford to damage the wing. The max exotherm (tested) of two layers of 1.5oz CSM w/PE tooling resin is around 150 F. The max exotherm would be even hotter with 3 layers and I’m sure 4-5 would be well over 200 F as I also tested a small amount of resin in a 3” diameter mix cup with 3/16” – ¼” deep resin remaining and it hit well over 225 F (my infrared thermometer just read “HI” after the last number I saw which was 225F)

Re the gelcoat: I already ordered the spray version not to mention the fact that I’ve already invested in a G100 cup gun so I REALLY want to learn how to spray the stuff with good results… I’m really hoping the right spray tooling gel coat, smaller nozzle size (#4 or #5) and reduced air pressure (45-60psi) will yeild good results this time… fingers crossed!

BTW: The data sheet on the gel coat says the HDT is only 122F with room temp cure and 203-212F with a post cure of 150F for three hours. The ambient in my hangar during the day can easily reach 125-130F, this isnt 150F but its close… Question: Should I be worried about post curing the gelcoat or is the 125-130F ambient going to elevate the HTD enough to work for my needs?

The molds will be used to create one set of gear doors for my airplane (maybe more if other builders are interested in buying a set of gear doors) - the actual gear door stack will be: White gelcoat (sprayed in the mold), CF, CF, CF, 1/4" roacell core, CF, CF, CF. I’m thinking I’ll infuse the first three layers of CF in the mold after spraying the gelcoat… let cure… then wet vac bag the core, let cure… then infuse or or wet layup/vac bag the last three layers of CF, let cure… then demold. Resin will be infusion epoxy.

#19

Do some tests with infusing the whole lot at once. Saves a lot of time.

As for the tooling resin: again: datasheet, datasheet, datasheet. Without knowing what it is, it is really hard to say.

For the stuff we sell here we have a day-to-day schedule on what to use, when, and how much.

Did you get a wet film thickness gauge? Skill is good, exact measurements are better.

#20

As herman says datasheet, datasheet, datasheet this is where it helps to have a suplier with good knowledge of their products.

I was suggesting 4-5 layers in one shot, 2 shots = 8-10 layers in a day. Obviously so many layers in one hit is a NO GO given the requirment of not exceeding the HDT of wings which might be challenging with such a tooling system.
So if method b is within your temperature requirments go that way (4-5 layers in a day, 2 layers at a time, wait until exotherm has coold to near ambient, then apply next batch of layers).
Tooling resins tend to aim for rapid build up of thickness and controlled exotherm to maximize strength properties. Moulds do not always require tooling resin I expect VE or epoxy with a matched hardener would give good results wthout the risk of exceeding the HDT of the wing.

Be very careful how you proceed.

TEST TEST TEST