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Rootsy
03-27-2006, 12:06 PM
I need to spray gelcoat onto the mold for my ski locker... i have an elcheapo gun with an .079 (2mm) fluid tip in it... the gel i have is lamenating gel so i need to add a bit of wax to it...

How much should i cut straight gel out of the can with Acetone to feed it through the gun and still get good film thickness and what not... how many coats should i apply and what amount of time between them. assume that the temp shall be between 60 and 70F... so also how much MEK should i add...

this is the first experience i have with gelcoat... and spraying it... not like i am doing a whole boat but i still don't want to have to spend 60 hours sanding...

is there a way to get it to flow out smooth so i don't have to do a lot of sanding work???? or is it inevitable...

thank ya kids

Jamie

gcarter
03-27-2006, 01:33 PM
Jamie, having just done this, according to Lenny you cut w/ styrene as it's a component of the resin. Acetone is not. I got good spray results at about 20%.
I had really good success spraying. You really can't screw it up. The worst I encountered was if you sprayed too "slow" you got more orange peel than if you spray faster. It doesn't seem like it will run no matter how many coats you put on at once. You just keep going till you reach the depth you want.
For MEK, I used a chart provided by the supplier. I mad up a little more than a pint at a time, thinned with the styrene, added MEK w/ a syringe (it seemed I used about 5CC's) and poured it into the bag I had already installed into the gun. By the 3rd or 4th can, things were going real well. The previous ones, I just had to do a lot more sanding.

gcarter
03-27-2006, 07:24 PM
Just so no one mis understands, you use a quart measuring/mixing cup from your local friendly automotive paint store. As you will see, there are a lot of different scales printed on the side, including volume in ounces and ml.
Add the amount of gel to the cup that you can safely spray (do this with the cup on a level surface) while filling to a particular number on the 5/1 scale that corresponds to the volume of gel you are planning on spraying. Then add the styrene to thin the gel (if you filled to the "5" on the 5/1 scale, then add styrene to the corresponding "5" on the second part of the scale). Mix well with the trusty old paint stirring stick, and finally add the MEK catalist. This you also do according to a scale that corresponds to a percentage ratio usually supplied w/ the gel. The MEK is added with a syringe calibrated in cc's. If I remember, I used between 4-5 CC's for about 18-20 OZ. Mix again thouroughly and pour into your gun.
The stuff is pretty "stiff" but you can get good results that requires minimal sanding. I wouldn't mind hearing from Lenny to critique this post, but I used a D-A sander to color sand starting w/ 220 then working to 360 or 400, 800, 1200, then I buffed. If you asked others, they would go to 2000. I was only doing the bottom and no one inspects it that closely anyway.

mphatc
03-27-2006, 08:30 PM
Everythng said is correct . . .

That said, if you don't have styrene and wax . . . Acetone works
BTDT many many times . . . my entire transom was done this way with a two color seam at the water line.

If you use acetone don't use wax .. apply thin coats from a bit greater distance, this allows for some acetone evaporation during spraying, and allows you to build up a surface thick enough to wetsand to perfection.

Apply a coating of water based mold release agent after the application of gelcaotto seal the gelcoat from the air. http://www.freemansupply.com/PartallPVAMoldRele.htm

I wet sanded my entire transom by hand in 1/2 an hour starting with 600 grit.

Mario L.

mrfixxall
03-27-2006, 08:53 PM
rootsy, you may want to do a test mix first to make sure you have mixed the mek and the gel correct....if you put too much mek in it will kick off too fast and make the gel brittle,kinda like hard candy (it shatters)also if you use acitone it will cause minor pinholes and solvent pops..i would stick with styrene and wax...you can also use just gel and styrene but you have to cover the serface with pva but if you have to wait for it to tac up defore you spray it with pva...if you spray the pva too soon or too thick wou will have the worse case of orange peel you have ever seen....you can also use a black foam roller that i found to work out vary well....also i would get a elcheepo gravety fed spray primer gun. the suction type dont seem to put out the materal like a gravety type gun.....keep feeling the guns cup for heet,if it gets warm dump it and flush it with acitone rite away....

p.s. you can also mix release wax into the gel so it can cure..like i said do a test piece first..
good luck....
mcd

farmer tx
03-27-2006, 10:34 PM
Just a dumb question. What is MEK? Methyl Ethyl Keytone?

Lenny
03-27-2006, 11:57 PM
Yes Mark, actually "Methyl Ethyl Ketone Peroxide" (MEKP)

Jamie, why you are spraying gel into your mold, (if it is indeed your plug) for a mold is beyond me. Into a MOLD, yes, and all that cutting stuff with a 40 tip will solve your problems (somewhat) with normally aspirated spray equipment, BUT, if this is a plug, that will become the mold for your next piece (the one you want) you are working far too hard.

3-4 coats of lacquer works fine, then about 3 coats of wax and leave the last coat on and DO NOT remove it by buffing. Then the "Part" you have that will be the mold for what you REALLY want as an end piece, can be buffed easily with Finese or whatever, THEN spray the gel into it and go the laminate/re-inforcement way on the piece you keep. Give me a call on Tuesday. 250-474-4005. Leave a contact number if I miss you and after I hear the missed call beep I will get back to you.

This is easy $hit, no need to make it a large ordeal until you get to the part you WANT TO KEEP for your boat.

Be VERY careful of thinning and such on the final piece. Wax, when mixed and sprayed into a MOLD mixed with gel is a no no. Gel is formulated that way already. You need a kicked surface (Gel) that is READY to accept the lay-up, not repel it.

Call me.... :)

Rootsy
03-28-2006, 06:16 AM
Thanks guys for the knowledge... i've picked up a few good things from this one....

lenny, the plug is my mold... i am going to slide it into the footwell / ski locker (or what is left of it) screw it down tight so the surfaces are flush, and layup the new locker.. then just break the plug away when done... i'll coat the plug with mold release and then lay up (non waxed) gelcoat... the gelcoat i have is laminating (non waxed) as it is so i had to add the wax to get a hard surface on the plug.

was only about 65 in the shop last night when i did this so the gel kicked a bit on the slow side, therefore i didn't get any solvent pop due to the acetone trying to come out after the gel had skinned over... learned my lesson in the early days of painting on a HOT day...

not trying to make this rocket science but i didn't want to end up with a terrible surface... i figure now i'll make this gel on the plug smooth... which will cause the finished product laid on top to be smooth... a 2 step process rather than the 3 that you are speaking of lenny.. which, if i was making something like a boat, for sure id go that route... but this is just to recreate what someone took away with a sawzall at one time... and no one will ever see unless they crawl up there under the dashboard...

thanks eh.. appreciate all of the help and then some..

Jamie