My in floor hatch molds step by step by Kaptain Koz

[kaptainkoz]

Today I built the other mold and prepped them both for gel coat. I filled a gallon sized Ziplock bag with ordinary sheetrock spackle and cut the tip off the bag to make a dispenser similar to what a cake decorator would use. I needed a small thin bead as I don't want a lot of excess to clean up. This made it very easy to dispense a controlled amount similar to a caulk gun.






I then used the rounded end of a popsicle stick to give the spackle the small radius I was looking for.


Once it dried I again took the popsicle stick to clean up and shape the spackle further. The nice thing about the white board is that dried spackle rubs right off, so any small smears or excess easily rubs right off with your finger or can be shaped a bit with the popsicle stick.

 im not super worried about the radius as I wll apply the gel coat thick enough where I can correct and shape any imperfections out with sandpaper on the final product. The spackle is primarily there to prevent the gel coat from creeping between the seams and really ruining your day when you go to pop the piece out of the mold.

 Once I was happy with the shape and profile I coated the mold with release wax. I may give it another coat before gel coating but im not worried about anything sticking to the gel coat and ruining my day. The white board is almost stick-proof, the spackle will sand off if it sticks, the clay wont stick and the stainless hatch most likely wouldn't either as most of it is smeared with clay at this point anyway. I waxed it just in case.




tomorrow we shoot gel coat with a dump gun

[RickK]

Looks good Steve    Are you going to try anything different this time?  Like thinning the gelcoat, maybe with Duratec?
I need to start on my console soon adding a door to the helm side and then I will be ready to shoot that baby, so I'm like a sponge right now watching what you're doing.

[kaptainkoz]

Being these are wide open with no crevices I don't think I will have any issue shooting regular gel coat with the dump gun. On the hatch molds, the narrow vertical passages of the gutters were near impossible to shoot. The gel coat shoots fairly straight and doesn't mist well so nooks and crannies can be tough. Plus it shoots ALOT of gel coat so you can't really hang out in one area too long without drowning the area. Thinning would increase the flow and probably worsen the dump.

I'm a novice at best so I'm sure I need more time on the gun to get used to it and figure it out better, however the beauty of this type of mold manufacturing is the gel coat just has to be there and it doesn't have to be smooth and pretty. You can always tip it with a brush if you need to hit a particular spot. Keep In mind it sets up fast so you have work fast. DO NOT disturb it with a brush after it sets as you will pull it from the waxed mold and create dimples that you will have to fill after. Any additional coats or fixes should be sprayed only to not disturb the gel coat that's barely clinging to the waxed mold.

If you need a more precise coating then you may have to thin and go with an hvlp gun with a 2.4 tip. Most come off the shelf with a 1.4 or 1.8 tip so you have to hunt one down that you can get accessories for. Clean up on an hvlp is a pain. As of right now with my level of comfort and experience, on an external piece like a helm, floor or transom, I would think a HVLP with thinned gel coat might be more novice friendly as the gun is firing less gel coat per pass and easier to regulate. In any instance remember it's just gel coat. You can knock down, sand and fill away any imperfections and make it look perfect. That's the benefit of using it. You don't have that luxury with paint.

Again I'm no pro so if someone has a suggestion please chime in.

[RickK]

I'll be spraying it on a finished product, so a little different approach than what you're doing, The sanding, sanding, sanding and buffing is the same though      

[kaptainkoz]

Shot the gel coat today with a dump gun. I spoke a bit too soon about the lack of "nooks and crannies" on this mold as I forgot about the latches.  It actually works to illustrate what I was trying to explain to RickK just prior. Here is the first coat. As you can see I panicked a bit and drowned the latch with the dump gun. It shows how it bunches up from the air pressure and refuses to settle, as well as how smooth it can go down with the dump gun when you look at other parts of it.









I waited about an hour and shot the 2nd coat. It looks much better. I also took my time a bit more, reduced the flow on the gun, and sprayed from more of a distance with more motion to the gun








I waited about another hour with the doors baking in the sun and shot the 3rd coat




After about 2 more hours, I brought them in to be glassed. you can see a huge difference from the first coat on how it smoothed out with each coat. The best part is that if this were an external coat on a finished piece, I could sand it perfectly smooth. With it being a mold, I do not have to do anything. Each door got about 8 oz of unwaxed gelcoat per coat for a total of about 24 oz per door.




In the background you can see I cut the fiberglass. As for all my molds, Im using 3/4 oz chopped strand as my first coat. It is tissue paper thin and basically melts into almost any shape when wet with resin. I am using unwaxed vinlyester resin. Polyester resin will also work, epoxy resin will not work on this chopped strand as it does not contain styrene which is what dissolves the glue holding the strands together. The purpose of this super thin first layer is to make sure the gel coat is 100% backed by fiberglass. For example if I were to use 1708 biaxial as the first coat, it is too stiff and would probably lift in the corners and forget about it making any real contact around that intricate  latch







Here I mixed a batch of resin with West Systems 404 to make a "mayonnaise" that I will pad the corners and seams with to make sure there are no voids between the gel coat and the fiberglass. I put it in a ziplock bag, cut the corner off and dispensed it like a cake decorator






I then poured some resin in the mold, spread it with a brush, but not in the corners to disturb the 404 mix. I then set the fiberglass in and gently stippled it into place adding resin as needed to make sure this layer was as flat as could be and fully wetted out. Hard part done! This first 3/4 oz layer is so critical to making a strong final piece. It is the foundation which the gel coat sits upon. You can see that the edges and seams are a darker green which is the 404 mayonnaise sitting right where it belongs.

The next layers should go on as smooth and flat as possible, but with each additional layer it becomes less critical to do so. Ill let it set up overnight and tomorrow ill add the next layer which is 1.5 oz chopped strand.

 

[CLM65]

Most excellent, Steve!  When I did my doors and my transom enclosure, I tried to do it all wet-on-wet.  I ended up rushing it, trying to do too much at one time.  The rest of my form products will follow your approach.  Your results speak to the quality job you are doing.  Keep it up!

[kaptainkoz]

Craig, thanks for the kind words. Once the gel coat is stabilized with the 3/4 oz chopped strand, you pretty much could dump layer after wet layer in as much as you want. It depends on how intricate the piece is but for simple flat pieces you could layer up. Keep in mind the gel coat and the resin have to be unwaxed for the next layer to properly adhere to existing layer. Only the very last coat gets a wax additive to encapsulate the resin and fully cure it.
I have to take this one layer by layer as after the next 1.5 oz chopped strand layer, I will be adding plywood stiffeners, then as many final layers of 2408 biaxial as needed to bring me to my desired thickness. I have to be mindful of overall thickness as it has to mate correctly to the frame.

[RickK]

You mentioned you turned down the pressure - to what? I have read somewhere that you really don't need a whole lot of pressure with the dump gun.  
How far away did you get your best results?  I remember this pic from Scott's rebuild - I realize it's not a dump gun but look how far he is away from the subject


Do you keep your finger on the trigger all the time or release it as you spray past the subject like a automotive painter does to prevent buildup on the overlaps?
Good stuff Steve  

[kaptainkoz]

The directions for the dump gun says 60-100 lbs! It specifies 5.8 cfm's at 80 lbs which is a lot of air. Forget the Home Depot pancake compressors here. The dump gun needs a lot of pressure. I don't know where I was at as I don't have a gauge on the dump gun, and I don't think it would matter as I could feel the pressure dropping as the gun was outpacing  my compressor. It's tough to trigger the dump gun on and off because you have to raise the tip up when not firing or gel coat will just ooze out the tip. It's not like an hvlp gun which you can totally trigger on and off.

As the name implies- hvlp - high volume low pressure, it requires lower pressure to work. The gun in the photo is not a dump gun as the painter is holding a canister. I think it's an hvlp.

What I adjusted was a knob on the back of the dump gun which lowered the air flow through the gun. Like anything, I'm sure after 10 or 20 more shoots that I would have a completely different review of how to make it work great. I'm still too green with the gun. However, the end result and the good news is that at the end of the day I am able to get an acceptable finished product one way or another. I would LOVE to master the dump gun as cleanup is ridiculously easy. An hvlp is sooo precise but you have to go from start to fully disassembled and drowning in acetone before the gel coat sets up in the gun leaving you with a pretty paperweight.

Distance wise I would say I was at about 2 feet or so except when I panicked and went too close around the latch as indicative of the air pressure splatter of the gel coat around the latch. It's a learning curve definitely.

[RickK]

I'll have some problems with my compressor too, it's a 30 gal and probably gets 4.5 cfm.  I'll do the best I can I guess.  Don't want to buy nor do I have room for a big boy in my shop.

[kaptainkoz]

You may have to go hvlp. They are cheap enough. Just a matter of finding a 2.4mm tip kit.

[kaptainkoz]

Here's a nice setup for $50.
http://www.amazon.com/gp/aw/d/B001NOU92 ... t_redir=1#

[RickK]

I have a dump gun, so I can do the build up with it and then I have a couple HVLP, one very nice and I'm not getting gel anywhere near it  
I use it for spraying finish on wood.  
For the finish coats I will go with a lower priced gun with a 2.4-2.5 tip and some additive.  Not sure if you can just run/spray acetone through it to clean it before it kicks or what - defintely have to be quick. Like you said, don't need a pretty paperweight.  The one you linked to is not a terrible price.

[kaptainkoz]

Nope on the acetone run. It will take most of it out and buy you time for a few more pots but it will still require a dis assemble, brush and a soak to fully clean. At least that's been my experience.

The distributor for the above link, TCP Global rings a bell, im pretty sure they are who I got my guns from a few years ago. I bought the 3 pack and a 2.4 mm tip kit. Fairly decent quality and a great bang for the buck. Here is their direct site: http://www.tcpglobal.com/spraygundepot/tcpgate.aspx

[kaptainkoz]

applied the 2nd layer today. 1.5 oz chopped strand.