A PVA Mess!

Tunnels, please. You still havn't confirmed how long it takes you to spray out a 500ml cup of the PVA in the manner you described. It took me 30-40 minutes. it seems to go forever. I could fall asleep. I started inventing robots to work for me while I was spraying the stuff on.

If we want to be serious here, if the mold is on wheels, you could roll it into a plastic greenhouse with 4 guns loaded with the PVA and just mist the booth for 10 minutes. Then you pull her out of the booth and she is all ready for some gelcoat.

I am not going to go spray up the mold 1000 times over the next five years. I will build a booth.

I am not a robot!

"Wooden men can perhaps be manufactured" - Henry Thoreau

 

I dont get what you are talking about ?? how long does it take to spray out 500 ml ?
you didnt just spray the whole lot on one mould did you ?? if you did then you need to re-read the instructions over a few times to get the meaning . Its just one thin coat !! not spray over and over and over !! till its all gone !!
i am not into holding ones hand every step of the way , there is a little thinking has to take place or we should be out swinging in the trees with our play mates !!
Once you sprayed your mould just pour whats left in the spray pot back into the bottle or another bottle ready for next time !! and reuse it !! or if you have two guns just keep one for pva so you can pick up and use any time you need it .
You dont have to keep spraying it till it runs out , what are you thinking ??
if you only need a little then mix a little if you need a lot mix a lot !!

 

No I didn't keep spraying it till it runs out as I read your estimate for a guy with his 18fter than he should end up using 3/4 of a cup for that area.
I have 8m2 of plug.
Secondly, I kept spraying quit alot because I can't afford to lose this plug I am making the mold from.
Thirdly the reason I just kep spraying away is because the stuff is invisible on the surface and I decided I should build it up more than you recommended just to be extra safe.

Surely, for production mold I would spray it up less. But would be good to have an estimation of the quantity per area. As you mentioned, it can't be seen - If I missed a spot then that spot may stick.

There was one spot which did stick, very tiny area. It damaged my plug surface and the mold surface. I think it may have been from a drop and smidge of sweat or sweaty hand print.

 

have a nice day !!

Spraying multiple coats is really not nessasary 2 at the most first spray one way thn 90 drgrees and spray the other way . like i said if you can see it you have to much on !! yse you plug or mould should have a shine and could even be shiner then before but the more coats the more chances of getting dust in the spray any more than2 coat deffinity is a waste of time and product and immediatly its 100% dry gel coat it straight away !.
Spraying your Gel ???
what kind of a gun ? .
What catalyst ration you use ?
How many kilograms to gell your plug ??
And just as i idea what tempraures and humidity doe you get in yor part of the world ??
Remember your gel time should be close to 20 to 30 minutes tops anything over that you better look at speeding in up a little next time .
slow gel is soft gel ! slow gel begins to attach the coats on the mould and surface below .

 

The gelcoat would gel in the gun in 4 minutes with 2% DM50 cat.

Tried 1% and same problem

So i end with .5% gave me about 10min

My resin i ended up with a 40-50min geltime with 0.33% cat DM50

I am spraying the gelcoat with a drop cup gun 4.2mm tip and it looked excellent zero-porosity and glossy and flexible after i blew off my first lamination attempt because of resin seeping over and gelling to untouched gelcoat while i was at lunch, pools of it.

This day was 30c and sweat was coming off me like dripping off my every part of my body with looming clouds who herald to but never did - humid hein?

My plug has 7.5m2

 

when i say it would gel in the gun i mean i almost lost the gun two times and i was moving fast and nervous before it

 

what variables affect gel-time and why is never a table-of-values for it include by the manufacturers?

 

Need Catalyst type help !!!

wow !! something is wrong !! The catalyst you using is the same for the resin and the gel coat ? we have the same issue here in China as well but the resins and gel coats are built to suit the differant times of the year winter we have 5c to 8 c and summer the other end of the scale at 35 c plus
but our products are marked winter and summer so promotor levels are calibrated to suit .

You should be using a differant catalyst for your gel coat . the DM 50 sounds way to strong in both cases . Ideally you should be able to get a 15 minute gel time for the gel coat at just over 1.00% catalyst and a 20 to 35 minute gel time for your resin at about 1% catalyst ratio .
Did the supplyer recomend that catalyst ??
To little catalyst in resin and gel coats and they never really get to there proper hardnesses !.
You mist have a pretty good measure to be able to get those amounts each time !!

Some one here on Boatdesign must have a better choice of catalyst to slow reaction times down to a more acceptable level !!!.

 

i use blood syringes buy from the chemist

thanks for the insights

yes the main supplier of Santa Catarina,Brasil said cat good for both. This is Brasil. The culture here. I hate my life here; from Melbourne...
But Australia does not have 850,000 VW Kombi vans driving on their roads...

i got into fibreglassing because everyone here just tries to rip you off. Is no win-win culture here.

 

Sounds like a good place to be !!
Need to find a catalyst that not as stong !! that will ease the pressure off you and give you a little more breathing space

 

i got into fibreglassing because everyone here just tries to rip you off. Is no win-win culture here I hate my life here850,000 VW Kombi vans

So spoke to them today about the catalyst and asked them if they sell any other catalyst and also if documents come with the resins or gelcoat they sell and got the exact crap I expected from them like f[ing retards they are here in Brasil. Just DM50. I asked him if he knows why it is called DM50, does he know there is probably DM40, DM30 etc...doesn't know ****. Santa Catarina is the biggest chemical industry in Brasil and this is the ***** that comes out of the main small-business supplier of fibreglass materials and chemicals in the state. ***** nothing.
And you know how industry is done in Brasil? It is mulitnational and totally locked down. These people from this culture are a joke. This country deserves what it has coming to it is an NWO total takeover.

 

Hi folks. I've searched the internet for weeks now, and it looks like the only people that can help me maybe you guys.

I'm actually NOT a boat builder, but I make props and costumes, often utilizing fiberglass gelcoat molds.

My issue with PVA spraying is I get the "flying spiderwebs" and "strings". I believe Tunnels is correct, the PVA is "drying" almost instantly as I'm spraying. Upon further research, it looks like PVA does not like temperatures higher than 75 degrees or dry climates. This is really bad for me as I live in Las Vegas, which is ALWAYS dry. Not to mention I spray outside which can sometimes be between 90 and 100 degrees.

I use this spray gun: 4 oz. Adjustable Detail Spray Gun. It's operating range is 20-50psi and Nozzle Size of 0.6 mm. Now keep in mind the pieces I'm covering in PVA are usual about one square foot (I'm not spraying large boat parts). However the molds are fairly detailed, and I would hate risking my fiberglass getting stuck to the master.

With that nozzle size (and not needing to cover a large area) should I dial the PSI down to like 30? Or higher? Also should I close up the valve from the cup so less PVA is moving through, or should I open it up? It seems like no matter what I try I always get the cobwebs.

In the end am I going to have to add water? I use PVA from Tap Plastics and when I spoke to their technical support, they neither recommend for or against watering the PVA down. They just simply say "we have not tested watering down our PVA".

I appreciate any feed back you guys have. I understand that it doesn't help that I am not a boat builder, but my hopes is the PVA/fiberglassing word is close enough that you suggestions might help.

Thanks in advance.

 

You can water down to any percentage you want starting at say 25% just as a figure and see what happens !! or 10 % what ever its easyest to blow with air to make it dry rather than wait a long time !!

I also worked in Television workshops making sets ,props and numerous other things and just softly brushed straight pva on most everything i made !! never used any wax and washed the pva off with warm soapy water so it could be painted !!

 

Thanks Tunnels! I think 10% worked when I did a test, however I was only testing the reduction of cobwebs. I didn't want to waste a lot of PVA just to see if I could get a film, but when I get more PVA, I'll do a full on test.

I also heard a rumor that if you chill your PVA and HVLP gun in the fridge, it will help. Of course this only works for a little while until every thing comes up to temp. Since I do such small pieces I was thinking I could keep a small ice chest in the garage with my few ounces of PVA already dispensed into little cups. Every coat will come fresh out of the cooler. But I think the water method is easier, and in my temps (90+ degrees) it might just be the best option. It just would require more coats.

I used pure carnuba wax then sprayed PVA over it. If I get brave enough, I may try it "wax less". This is my latest mold, even with cobwebbing I was able to easily remove my casting:



The reason I'm so paranoid is this clay sculpt took me close to two months to complete. The only thing I have left of it is the fiberglass mold, so if that gets destroyed, I'd have to re-sculpt the entire thing. But you know that since you worked in TV making props

 

Todzilla,
So far I've tried spraying PVA through each of my stock guns and through the modified versions of those same guns with tip sizes ranging from 2.0 all the way down to 1.0. Webbing usually occurs when when I have the fluid flow too low and the air pressure or air flow too high. My best results so far have come (quite unexpectedly) while using my smallest gun with a nozzle size of 1.0 and air pressure of 20-25 psi.

Since I haven't tried a 0.6 tip yet I can't state with absolute certainty what settings might work with such a gun, but I think (my intuition tells me) that your tip size is too small. Thats why no matter what settings you use the end result is webbing....the tip is restricting your fluid flow to the point that almost any reasonable amount of air flowing past causes webbing.

If I might offer some suggestions:
Purchase a gun with at least a 1.0mm tip
Try thinning our PVA in stages to see if the gun will shoot these fluid successfully.
Open you fluid flow to it's highest setting
Lower your PSI to say 10psi and work your way up to 20 or 25psi...no more.

Spraying PVA is as much art as science so experimentation is the order of the day. Just remember that with extremely thin PVA layers you may want to apply it in several layers letting it dry in between. Your first shot is always a light mist..this helps to eliminate fisheye in subsequent applications.

Good Luck
MM