My in floor hatch molds step by step by Kaptain Koz

[CLM65]

Ouch !  Sorry to see that.  I don't know why that happened, but I sure am interested to hear why.  How long did they cure before you popped them out? Is it possible that they were not fully cured yet?

I have just started some hatch molds myself, so I'll be closely following this mystery.  I plan to add the backing reinforcement prior to popping it from the mold...hopefully that will help...

[kaptainkoz]

Craig that's a possibility. It was just About 18 hours for the two layers of 2408. The prior layers were laid days ago. I was thinking the same thing that maybe I popped them out a bit too soon. I have no idea but that could be a logical explanation.
I just checked on them. They are toast. I have them out in the sun now to see if a little heat will help but they have so aggressively warped that I think they are lost. I placed ice cream sticks under them around the perimeter before weighing them down and I'll let them bake for the day. I am super aggravated. Let's see what happens after a day in the sun.

[kaptainkoz]

I think I found the answer:

http://www.audiogroupforum.com/csforum/ ... hp?t=17264

I laid a layer of 2408 biaxial, gave it two hours then laid another. I should have given each layer 24 hours and left it in the mold for a few days after

[CLM65]

Sorry to hear that, Steve.  That's a tough lesson to learn, and the hatches looked really good too.

[RickK]

Well I'm back on terra firma in the US finally and just read this - that stinks.
The only thing I can think of that I do differently (not including not making a fancy mold) is that after I lay the cloth on the mold I cover it in plastic and weigh it down with blocks for a day or so.  Maybe you need to do that?  I wouldn't think so but if that's what it takes to get a flat door.....

[kaptainkoz]

Welcome back Rick. Yes, as I slowly accept that those doors are toast, I'm thinking about what to do differently and I think the strategy is single layers, a full 24 hrs between layers, weights on the first and 2nd biaxial layers, and 48-72 hrs before popping it out. Maybe even the plywood stiffener before popping it out.
Luckily the molds are intact.

[CLM65]

Maybe even the plywood stiffener before popping it out.

I think this is the most important step....

[gran398]

Will ask Seamark Boatworks here for input on layup schedule, procedure, and time in the mold . They make molds and produce fiberglass parts for a myriad of applications.  Contractor to the State of North Carolina for  public aquariums.

They'll offer sound advice. Will report ASAP, hopefully Monday.

[RickK]

You laid the straightedge on the molds too right?  I assume they're flat.  I would guess it is a curing thing - you're using vinylester right? I'm not familiar with how that hardens.  I know heat will warp stuff so maybe as it is curing it needs to be held flat?

[kaptainkoz]

Yes the molds are pin straight and they came out of the molds straight. In fact when you place them back in you can clearly see them bowing out of the mold. Yes I am using vinyl ester. I'm going with the fact that it was two layers of 2408 laid about 2 hours apart pulled from the mold at the 18th hour before fully curing. Going forward every layer will get a full 24 hrs between layers and the finished piece will get 48 hrs before removing from the mold.
None of my other pieces warped at all so this is a strange case. I'm going to get started on them Monday with gel coat.

[RickK]

Figured the molds were good.
Why not go wet on wet and lam all the layers, cover it with plastic and weigh it down for the week?  Then pop them and add your backers and again weigh them down.  I would wait on the backers because you'll need room to get the blocks or whatever you use to weigh them down, into the mold and spread out.  I even used the blocks to help make that cloth bend at the edges  

[aquadaze]

the resin is shrinking from heat (too much resin vs. glass) and causing it to warp over large areas. Vacuum bag it, and it will stay flat.

[kaptainkoz]

Thank you all for the great advice. Not sure which way I'm going to go but I am happy about all the food for thought. Thanks!!!

[Callyb]

I'm late to the party, and you have probably moved on....

However, I'm thinking that the resin wasn't fully cured and it sagged when you pulled it. I would core it in the mold and let them cure for 3 days or so (depending on temperature) before popping them. I also, would try to work wet on wet...This is a personal preference though.

On the other hand, You are rocking those molds! It appears to me that you have the process nailed down.

Great job!

[kaptainkoz]

Thanks Carl. I believe that's what happened too. 18 hours for 48 ounces of wet glass just wasn't enough I think. As for working multi layers, I have to carefully lay the first 3/4 oz chopped strand to make sure it is stippled into every nook and cranny to insure that my gel coat is properly backed. The following 1.5 oz is pretty much the same idea. I wouldn't be able to get the correct quality control slapping down all the layers at once especially in the corners and around the latch. Im in no rush and im going to stick to what has worked well before which is layer on cured layer. the difference here is that its getting 2 full days or more before I pop it out. I have to guess/believe that the failure happened because of uncured glass. It either pulled or sagged as they were left gel coat upwards after they were popped from the mold. I should be starting again in a day or two.
Again I thank everyone for sharing ideas on how to solve this. This sucks, but all things considered these are the easiest piece of the molds I have done so im grateful the failure (lesson) was on these. On the bright side, I wasn't 100% happy with how the latch pocket came out so now I have another chance to make them perfect. If you look at the picture of the underside where it is sitting in the frame you can see that it didn't follow the contour of the frame clearance evenly  which would have required modifying the frame. I have another chance to avoid days of minute glass/gelcoat repair.