Gelcoat/Clear Coat & Styrene

[super_dork]

I'm going to be using poly gelcoat and clearcoat when I finish my build. I failed to ask at the fiberglass shop about thinner. I've seen videos and posts with guys using Styrene as a thinner. I'm going to be using a Preval sprayer. so my questions:

1) Do I need thinner?
2) Is styrene the right stuff to use?
3) Where can I get some other than ordering or going back an hour down to the fiberglass shop? I'm in north Houston, if that helps.

 

[Scott Danforth]

clearcoat is for paint. gelcoat gets cut-n-polished. Woodonglass or ondarvr will be along shortly to answer your styrene question.

BTW, the preval sprayers work sort of for spraying gel. they do ok on spraying PVA over the gel how big of an area are you repairing?

 

[super_dork]

You can check out my build thread here. http://forums.iboats.com/forum/boat...el-peachy-1993-stratos-280-sf-transom-rebuild


I'll be spraying about half of the back end and then the 2 areas where I cut the hull. The last 2 pics in this post are the largest area I'm spraying. http://forums.iboats.com/forum/boat...80-sf-transom-rebuild?p=10077674#post10077674

I don't own an air compressor and I've see that the Preval seems to work ok. I have a friend who has a compressor and some HPLV sprayers that I can likely borrow if needed.

I've got clear gelcoat (maybe not clearcoat) to spray the metal flake back on with...

 

[sphelps]

Not sure but that may be to big an area to use the prevail .. IDK
Your friends hvlp may be a better option ...
I will be using styrene to thin the gell on my project .. Doing the whole boat .. Hopefully gunna spray this weekend ..
Hope your flake repair goes well .. Ondarvr would be your best bet on guidance ... JMHO ...

 

[super_dork]

I'd love to get know how things go with your spraying. Are you planning to update your build thread with it? If not, please post back here to let me know what worked and didn't. I've gotten this far and would hate to screw it all up with a crappy finish job!

 

[Tail_Gunner]

You can check out my build thread here. http://forums.iboats.com/forum/boat-...ransom-rebuild


I'll be spraying about half of the back end and then the 2 areas where I cut the hull. The last 2 pics in this post are the largest area I'm spraying. http://forums.iboats.com/forum/boat-...4#post10077674

I don't own an air compressor and I've see that the Preval seems to work ok. I have a friend who has a compressor and some HPLV sprayers that I can likely borrow if needed.

I've got clear gelcoat (maybe not clearcoat) to spray the metal flake back on with...

Those prevail sprayers are not up to the job you have some area to cover...harbor freight has HPLV sprayers for about $15 get a couple borrow your freinds pump and learn how to clean the guns quickly gel hardens in about 10 minutes and forget the styrene. Shooting gel is very easy getting the system right is a bit confusing ....and cleaning the gun's is the real pain in whole operation....sometime's i just spray till it harden's and toss the little bugger's.

 

[sphelps]

This will be my first attempt at gell ..Keeping my fingers crossed it goes well .. Here is a link ..http://forums.iboats.com/forum/boat...ding-and-hull-repair/9265964-save-the-manatee
I'm just spraying white gell ... Nothing fancy ...

 

[Woodonglass]

You can check out my build thread here. http://forums.iboats.com/forum/boat...el-peachy-1993-stratos-280-sf-transom-rebuild


I'll be spraying about half of the back end and then the 2 areas where I cut the hull. The last 2 pics in this post are the largest area I'm spraying. http://forums.iboats.com/forum/boat...80-sf-transom-rebuild?p=10077674#post10077674

I don't own an air compressor and I've see that the Preval seems to work ok. I have a friend who has a compressor and some HPLV sprayers that I can likely borrow if needed.

I've got clear gelcoat (maybe not clearcoat) to spray the metal flake back on with...

I'm POSITIVE the Pre-Val sprayers will NOT do the job. They are GREAT for touch ups but NOT for large areas of work. You MUST have at a minimum a 10 gallon compressor and a 1.8mm tipped HVLP spray gun. Even then It won't be a piece of cake.

 

[super_dork]

Well that's what I was kind expecting to hear - and why I am trying to ask before I execute. The Preval is just so cool!!

I'll call my buddy and have him drop off his monster compressor and sprayers when the time comes to start spraying.

So the other question still stands. Do I need Styrene or can I get away with Acetone? I've also read about Super High Gloss Additive. I'm honestly just trying to avoid a 3 hour round trip to the fiberglass shop or marked up internet prices if I can avoid it. I have acetone. I don't know where to get Styrene other than the fiberglass place...

 

[sphelps]

I have heard don't use acetone for thinning .. Tail -Gunner said to forget the styrene ... The store I got my gell from said to use the styrene for spraying ..
I,m gunna start at around 5% and see how it goes .. Using an hvlp with a 2.5 tip ..
http://www.ebay.com/itm/2-5-mm-HVLP...hash=item4616178cd1&item=301018352849&vxp=mtr

 

[super_dork]

I mean, worst case, I know how to grind it all back off!!

 

[ondarvr]

None of thinners are great, and all have negatives. Styrene will allow it to turn yellow much quicker, acetone can inhibit the cure, the clear additive can work, but it too can cause color change. The more you add of anything, the more issues you may encounter, most obvious is color change. 3% of acetone or styrene may not create big problems, but it seems 3% turns into 30% rather quickly.

You can buy products formulated to reduce the viscosity of gel coat and they typically work better than other solvents. The only problem is most are formulated to shorten the gel time for a better cure and quicker repair, so for a beginner it can be a little too quick, which can lead to a wasted spray gun when it hardens unexpectedly.

 

[super_dork]

So, does that mean, don't thin if I can avoid it or is it necessary to thin some in most cases?

I'm not trying to color match - just using off white, so if it yellows, maybe that's not the worst thing... Our lake seems to turn everything brown pretty quickly anyways, so discoloration may not bother me much. I'm not looking for a garage queen, just something sea worthy, but I don't want chalky gelcoat either...

 

[ondarvr]

If you're not that concerned about it being perfect I would use a small amount of acetone, It's cheap and you have some. Add just enough so you can spray it, don't try to make it into automotive paint, don't expect it level and flow with no orange peel.

 

[Woodonglass]

Never shot gelcoat, but...As ondarvr states, from what I've learned from him and others, it seems the less you thin it the better. That's why I said to use a Minimum of a 1.8mm tipped gun. a 2.0 to 2.5 tip would be better like sphelps posted. You'll get more orange peel and have to do more sanding but you won't have to thin it much if any. Remember it's just like poly resin and it WILL kick in about 20 minutes soooo you MUST be prepared to stop spraying and get the gun cleaned from any and all mixture before that happens OR you'll be buying a NEW Gun!!! Having a helper really is a good idea to help keep you aware of the timing of everything. Also remember that gelcoat needs to go down thick. A minimum of 20 mils is what you're looking to achieve for a final thickness. that's about the thickness of a Penny. That way when you sand off the Orange peel you're Final Final thickness will be about 10mils or maybe a little less.:thumb:

 

[super_dork]

So another follow-up. Can I brush it on or is the area too big for that? Since I'm going to have to do sanding anyway, is that an option or should I just plan to spray but do some practice before I get into it?

I also have read that too thick and you will end up with cracks in the gel. I know that my final coat needs to have wax in order to make it all cure fully. So, how many coats do I need? I'm assuming I will lay down the first coat then sand it smooth then do a second at least with the wax. Do I need another on top of that? It sure seemed very thick as I was grinding it all off.


You guys are awesome. The amount of knowledge on this board is great!

 

[DeepBlue2010]

You need to spray about 30 mills to end up with about 20 after sanding. 20 to end up with 10 will be too thin.

The max you can spray in one shoting is about 10 mills. You can verify this with a mil gauge. Get your gel ready, thinned and all but dont add catalyst, spray a piece of scrap and adjust the gun as needed, air, material, etc. When you are happy with how it sprays, measure with a mil gauge. Take a not of your setup, you will not have time to play with these dials in an actual shooting session with catalyzed gel. Clean every thing for the actual session.

Based on the mil gauge reading you got, plan on shooting 30 or so mills. If you get 10 mills per shooting, you will do this 3 times with enough time for flushing in between. You dont need much, just enough time for the gel to tack so that there is no solvent will be trapped when you lay the following coat.

Don't use your friends gun. It is very likely that you will ruin it. Use the $15 Harbor Fright one and buy yourself at least two, clean both and get them ready.

Be very percise and acurate when adding catalyst. Dont use the number of drops methd, it is next to useless and very error prone. Go to any pharmacy and buy yourself few insulin syringes 100 units. Those are divided so that the 100 units equal 1 cc = 1ml. So 30 units = 0.3 ml and so on. This is the best method i found to mix the catalyst accurately.

I catalyze an ounce or so and leave it in the same environment i will spray in, same temperature, humidity and watch it carefully and time it until it start gelling. Subtract few minutes from that and use a stopwatch around my nick. Set it when i add the catalyst to the gel not when i start shooting. Once it goes off, i stop immediately, pour whatever gel left out of the gun, add acetone and spray the acetone with the material dial on max. Repeat couple of times to fully clean the gun, mix gel and spray again. Be very organized. It will help great deal

What is the high temp in your area now? In the Northwest of US, it is too late for outdoor gel spraying now unless you work in a heated shop or garage.

 

[super_dork]

Thanks for the detailed info. This will really help. I found the harbor freight sprayers with a coupon for $9.99 so I'm gonna stop and pick a few up. Good advice about getting my own. Man, I was really looking forward to the Preval stuff, but I understand the limitations better now.

Not sure what the deal is, but my poly resin hasn't been setting up very fast for me mixed at 1% with temps inside the garage between 65 & 75 since I started working with it. Currently the outside temps during the times I'm working are in the high 50's low 60's but I'm in the garage and tend to be 10 degrees warmer than outside temps. Last time I was in it was 68 in the garage. (Houston, TX area).

 

[Woodonglass]

Yup, DeepBlue is Spot on 30 mils and sand to 20 is correctamundo. As for the poly I'd HIGHLY recommend a MEKP ratio of 1.5% when temps are in the 60's and 70's you can even go to 2% especially if you're mixing small amounts and able to put it down quickly. A word of Caution about the HF Sprayers. Their tips are only 1.4mm That's really kinda small for shooting Gelcoat. However you can buy a 2.0mm tip on Ebay that will fit the HF gun for $18.99 http://www.ebay.com/itm/2-0-FLUID-T...:g:ZnkAAOSwyQtVuuUa&item=381451682730&vxp=mtr

Or you can buy the gun that sphelps posted for $32.95 I really think you'd be better off with the larger tip. The 1.4mm is not gunna shoot gelcoat unless you thin it quite a bit and that is NOT advisable for large sprays.

 

[DeepBlue2010]

I believe 1% will be sufficient if you are shooting inside the garage unless ondarvr tells you any different then follow his recommendation. He is our subject matter expert.

If you have a gas house heater or water heater with pilot flame in the garage, turn them off if you will close the garage door