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UV Smooth Prime

RandyAB

Well Known Member
I'm doing my fibreglass work now and have read a bunch of different threads on how to prepare for priming. A lot of different options. With respect to the UV Smooth Prime, do I have to do a bunch of pinhole filling before applying it or is this primer meant to fill the pinholes with one or two applications and some sanding?
 
It is designed to fill pinholes. Stir it well, drip a little on the surface and use a credit card to squeegee in the first coat or two. After that, roll on a coat, and sand when dry. Be sure to follow the drying requirements in the instructions before top coating.
 
I used it on the RV-10 after a high end Lancair builder recommended it. I will never use it again. It added a lot of work for limited value. There are better ways to fill pin holes.

If you use it, never wet sand like you would do with a high build primer or a skim coat of micro. Smooth Prime absorbers the moisture - and it takes weeks for it to dry out before you put the real primer on it.

Carl
 
Fill the pinholes first

I have to agree with Carl,, I tried to get the UV primer to fill the pinholes I Couldn?t see before I primed, it failed miserably, from here on I?m going to use a squeegee with slow curing epoxy diluted with acetone to make it thin enough to go down in the pinholes before I get any primer anywhere near the cowls , be sure and sand off any mound release wax before hand with some 120 grit sandpaper , wish I had asked here before I forged ahead on my first build !!
 
There are a lot of different ways of filling pin holes, that work. Each does require specific technique to be successful.

The most important which is applicable regardless what method is used, is that the material be squeegeed on in multiple directions on the surface being treated. Up, down, left, and right, if possible.

I have used both the squeegeed on smooth prime, and straight epoxy resin (not thinned) with great success
 
It is designed to fill pinholes. Stir it well, drip a little on the surface and use a credit card to squeegee in the first coat or two. After that, roll on a coat, and sand when dry. Be sure to follow the drying requirements in the instructions before top coating.

Have you used this method with success Kyle?
 
There are a lot of different ways of filling pin holes, that work. Each does require specific technique to be successful.

The most important which is applicable regardless what method is used, is that the material be squeegeed on in multiple directions on the surface being treated. Up, down, left, and right, if possible.

I have used both the squeegeed on smooth prime, and straight epoxy resin (not thinned) with great success

Thank you Scott for the application tip. I think that I will try with straight epoxy as you suggest. When you say squeegee, are you referring to a rubber squeegee or plastic like a credit card?
 
I have to agree with Carl,, I tried to get the UV primer to fill the pinholes I Couldn?t see before I primed, it failed miserably, from here on I?m going to use a squeegee with slow curing epoxy diluted with acetone to make it thin enough to go down in the pinholes before I get any primer anywhere near the cowls , be sure and sand off any mound release wax before hand with some 120 grit sandpaper , wish I had asked here before I forged ahead on my first build !!

Thanks for the tip on the release wax.
 
There are a lot of different ways of filling pin holes, that work........

I have used drywall spackle to fill pinholes. Just rubbed it in with my fingers, let dry, sand, wipe (don't blow), and primer. Works great! 200 plus hours now and no issues with the technique.
 
Have you used this method with success Kyle?

Yep. There is an RV-6 around here somewhere as evidence.

The thing I like about UVSP is there is little wait between squeegee coats. It does its job well, and sands easily. The wait before applying an epoxy primer or finish coat is the downside.
 
Thank you Scott for the application tip. I think that I will try with straight epoxy as you suggest. When you say squeegee, are you referring to a rubber squeegee or plastic like a credit card?

By squeegee I meant the process/action used, not the actual tool.
I have used plastic scrapers, body filler spreaders, etc. Anything that will spread and the material being used and leave little excess on the surface will work.

As Kyle mentioned, the benefits of Smooth Prime are it sands easily and dries relatively fast (depending on conditions).
 
Yep. There is an RV-6 around here somewhere as evidence.

The thing I like about UVSP is there is little wait between squeegee coats. It does its job well, and sands easily. The wait before applying an epoxy primer or finish coat is the downside.

Thanks Kyle. I've done one wing tip with straight epoxy (messy) and will do the other as you describe with several coats of UVSP squeeged on and then top coated. We will see how they compare.
 
I have a dumb question

I'm doing my fibreglass work now and have read a bunch of different threads on how to prepare for priming. A lot of different options. With respect to the UV Smooth Prime, do I have to do a bunch of pinhole filling before applying it or is this primer meant to fill the pinholes with one or two applications and some sanding?

I've never painted fiberglass. What are the consequences of not filling pinholes?

Jerre
 
I have been using a product from Southern Polyurethanes Inc that has worked great. I still have more to do. I called their tech line which happens to be the company owner's cell phone. He was very helpful. What I did was to first go over it with resin by the smear roll and sand method. There were still a few pinholes after this. I used SPI's 2K regular build epoxy primer. I squeegeed it on then tipped it with a small chip brush and sanded it after hardening. It seemed to work great. The only thing I had to do special was to add some of their retarder to slow down the set up time. This also thinned it quite a bit which helped it get into the holes. I was glad this worked because I did not want to have to spray the epoxy stuff.
 
So I've tried applying the UVSP to one of the wingtips. I've tried dripping it on as well as brushing it on followed by squeegeeing it with a flat piece of 30 thou scrap aluminium. I find that it dries really fast and quickly becomes the consistency of drywall mud. in the end most of it gets scraped off which I suppose is ok I suppose because this layer is really intended only for the pinholes. When it dries I am going to sand it fair and roll or spray a layer over top and then re-sand. I wonder if Kyle or Scott would comment on whether this mimics their experience.
 
Randy, your experience is normal. The squeegee coats should only leave enough behind to fill the pinholes. Personally, I prefer to use a bondo spreader or a defunct gift card as a squeegee. I think those would be more flexible than a piece of aluminum.
 
Randy, your experience is normal. The squeegee coats should only leave enough behind to fill the pinholes. Personally, I prefer to use a bondo spreader or a defunct gift card as a squeegee. I think those would be more flexible than a piece of aluminum.

Thanks Kyle. I'm going to use my wife's credit card. That will save lots of money! :)

Did you try spraying?
 
I have been using a product from Southern Polyurethanes Inc that has worked great. I still have more to do. I called their tech line which happens to be the company owner's cell phone. He was very helpful. What I did was to first go over it with resin by the smear roll and sand method. There were still a few pinholes after this. I used SPI's 2K regular build epoxy primer. I squeegeed it on then tipped it with a small chip brush and sanded it after hardening. It seemed to work great. The only thing I had to do special was to add some of their retarder to slow down the set up time. This also thinned it quite a bit which helped it get into the holes. I was glad this worked because I did not want to have to spray the epoxy stuff.

I tried that with a similar Kirker 2K epoxy primer.

It did work but I found that un-thinned West epoxy was easier to do and seemed to have better results. The temperatures were in the 80's so the West stuff was pretty thin and runny anyway. It just seemed to squeegee better.
 
So I've tried applying the UVSP to one of the wingtips. I've tried dripping it on as well as brushing it on followed by squeegeeing it with a flat piece of 30 thou scrap aluminium. I find that it dries really fast and quickly becomes the consistency of drywall mud. in the end most of it gets scraped off which I suppose is ok I suppose because this layer is really intended only for the pinholes. When it dries I am going to sand it fair and roll or spray a layer over top and then re-sand. I wonder if Kyle or Scott would comment on whether this mimics their experience.

RV wing tips have gelcoat so they don't generally need any pinhole filling except for the area right along the mold seam on the edge.
Are you coating the entire wing tip with smooth prime?
If so, you are probably doing a bunch of unnecessary work.
That process is usually only required on non-gel coated parts (cowl, wheel pants, etc.) On the more rent part production, a switch has been made to gelcoating all parts so this work will be simplified on more recent finish kit deliveries.

Yes it does dry fast. That is one of it's primary benefits.
The goal is to squeegee it on and be removing all except for teh portion that fills in low spots and pin holes.
 
Ok. Just tried spraying UVSP on a test piece. It's not recommended.

After several tries, I was successful spraying UVSP by thinning it with 1 part water to 4 parts primer and using an HVLP gun with a 2.5 mm nozzle (https://www.amazon.com/dp/B001NOU92G/ref=psdc_15707181_t1_B001N1E9Y8 ). I used it on the interior of my RV-10 fiberglass cabin top, including carbon fiber overhead console. Tried using a roller but that didn?t work with all the tight curves and size of the cabin top. Also used it on the door interiors.

I did then sand most of it off before top coating. But it worked well for me on the inside surfaces. As for the outside, I intend to let the professional paint shop fill the pin holes, apply the primer, and then the paint. That way they can use materials and methods that they know work together, and they can be held fully responsible for the results.

Good luck
 
RV wing tips have gelcoat so they don't generally need any pinhole filling except for the area right along the mold seam on the edge.
Are you coating the entire wing tip with smooth prime?
If so, you are probably doing a bunch of unnecessary work.
That process is usually only required on non-gel coated parts (cowl, wheel pants, etc.) On the more rent part production, a switch has been made to gelcoating all parts so this work will be simplified on more recent finish kit deliveries.

Yes it does dry fast. That is one of it's primary benefits.
The goal is to squeegee it on and be removing all except for teh portion that fills in low spots and pin holes.

Ughhhh!!! Now you tell me! Actually, I installed the AeroLED cutouts to accommodate the lights so there was more filling to do. I did did do extra though. My cabin top is grey outside and pink inside. Is this gel coated?
 
Gel coat

Ughhhh!!! Now you tell me! Actually, I installed the AeroLED cutouts to accommodate the lights so there was more filling to do. I did did do extra though. My cabin top is grey outside and pink inside. Is this gel coated?

Yes the grey is gel coat. Minimizes alot of pinhole filling.
 
Ughhhh!!! Now you tell me! Actually, I installed the AeroLED cutouts to accommodate the lights so there was more filling to do. I did did do extra though. My cabin top is grey outside and pink inside. Is this gel coated?

The grey is gelcoat.

On pre-preg composite parts (like your cabin top and cowl) there may still be some surface texture caused by the cloth weave that needs to be filled.

The best process for things like this is to visually analyze the result of whatever process you are doing. I.E., the gelcoat is gray and the Smooth Prime is white. When you squeegee on smooth prime, is it leaving white spots in the grey surface (indicating that it is filling in voids or low spots)? If not, then you probably don't need to apply S. P. to the entire surface. But you probably still need to inspect the surface carefully to determine if there is any localized areas that need attention.

My experience with the gelcoated pre-preg parts is that the gelcoat is usually thick enough to sand with 220 and remove the surface texture, without sanding through to the fiberglass. In this case, it should be smooth with no pinholes in most all areas, and be ready for paint prep.
 
Thanks. One last easy question. What primer works well on the fibreglass? I used Akzo/Nobel for the interior but I'm sure that isn't appropriate to use in this application.
 
Thanks everyone..

..I'm enjoying reading/following this thread. I'm rough cutting my cabin top to fit right now, so the timing is perfect. Thanks Randy for starting it, and thanks to the people who've been answering the questions.

Here's a few more:
1)Where are you guys buying the UVSP?
2)Does it come in rattle cans, or buckets, like normal paint?
3)Do you have to mix it or just shake it?
4)Is it cheaper to use West Systems epoxy or the UVSP to fill pinholes?
 
..I'm enjoying reading/following this thread. I'm rough cutting my cabin top to fit right now, so the timing is perfect. Thanks Randy for starting it, and thanks to the people who've been answering the questions.

Here's a few more:
1)Where are you guys buying the UVSP?
2)Does it come in rattle cans, or buckets, like normal paint?
3)Do you have to mix it or just shake it?
4)Is it cheaper to use West Systems epoxy or the UVSP to fill pinholes?

You are most welcome Mike!

I bought it from ACS. It is non-hazardous so there were no Hazmat fees. It comes in a regular paint can either in quart size or gallon. Mixing was a hoot. All of the filler that they used settled and concreted in the bottom of the can. It wasn't going to mix easily by hand for sure. I transferred the contents of the can to a well cleaned plastic peanut butter jar, drilled a hole in the lid just large enough to allow a drill paint stirrer in and then put it on the drill press. It worked very well. I then transferred back to the original can. As far as cost is concerned. I would say that the epoxy would be cheaper. A little goes a long way with that.
 
RV wing tips have gelcoat so they don't generally need any pinhole filling except for the area right along the mold seam on the edge.
Are you coating the entire wing tip with smooth prime?
If so, you are probably doing a bunch of unnecessary work.
That process is usually only required on non-gel coated parts (cowl, wheel pants, etc.) On the more rent part production, a switch has been made to gelcoating all parts so this work will be simplified on more recent finish kit deliveries.

Yes it does dry fast. That is one of it's primary benefits.
The goal is to squeegee it on and be removing all except for teh portion that fills in low spots and pin holes.

Scott,

Do you know if the intersection fairings are now gelcoated or just the pants themselves? I planned on the RVbits intersection fairings, but may try the vans parts if they are now gelcoated. The previous ones were pretty rough.

Larry
 
Thanks. One last easy question. What primer works well on the fibreglass? I used Akzo/Nobel for the interior but I'm sure that isn't appropriate to use in this application.

an epoxy primer will have the best grip for F/G. Verify that it is specified for F/G use. I use SPI epoxy primer and it is very strong and durable. It is specified for F/G, in addition to steel and aluminum. Results are obviously contingent upon the cleanliness of the prep. Be sure to leave enough time for solvents to evaporate before spraying. F/G will hold the solvents longer than metal.

Larry
 
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Scott,

Do you know if the intersection fairings are now gelcoated or just the pants themselves? I planned on the RVbits intersection fairings, but may try the vans parts if they are now gelcoated. The previous ones were pretty rough.

Larry

That is one exception that I forgot about.
The intersection fairings that are available for all models except RV-14 do not have gelcoat because they are designed to have additional glass layers added during installation.
 
an epoxy primer will have the best grip for F/G. Verify that it is specified for F/G use. I use SPI epoxy primer and it is very strong and durable. It is specified for F/G, in addition to steel and aluminum. Results are obviously contingent upon the cleanliness of the prep. Be sure to leave enough time for solvents to evaporate before spraying. F/G will hold the solvents longer than metal.

Larry

Thank you Larry. I will look into SPI.
 
I use epoxy resin but I hit it with a heat gun to get it to be thin and runny, then paint it on and squeegee it off. It fills pin holes and any exposed weave and any dry micro porosity. Shine a light at a very low angle to the surface to expose voids, pin holes and other irregularities. Lighting is critical to good surface prep and painting.

You can also use a high build primer and rub it in with your fingers, but I like the epoxy method. It is a one stop sealing procedure for everything.
 
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