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  #1  
Old 03-19-2017, 02:30 PM
leaky leaky is offline
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How to bond Corecell to new fiberglass or itself?

Hi,

In the process of finishing a new boat I'm going to be using 5 lb 5/8 inch Corecell for the light semi or non-structural parts, walls for the enclosed head, v berth, winterback, engine box.

The core I have happens to be the contour single-side-scrim/scored style, more for doing a hull, but basically I ran across a bunch cheap still in the box that someone had leftover so that's what I'm planning on using. Hopefully that doesn't throw a wrench in the works.

I've made patterns for the bulkheads, the largest of the patterns will fit into a 7 X 6 ft square, the rest gets smaller.

My plan is basically, make myself a flat surface/table coated with mold release, lay down what I want for glass (ie a layer or two of 1708, haven't thought the thickness through yet)..

Then what I'm not sure about is when I lay the core panels down atop my laminating resin (not sure on VE or PE yet but one of those) what should I do to assure I get good adhesion? I've read lots of things, simply using lots of resin to thickened resin, to special bonding pastes. It seems like if X resin would bond to the foam OK for layup then thickened resin of X type would be fine as the bond but no idea. This is a first for me. What should I use?

Then second question, when I lay the foam down - should I lay the scored side down first (I could probably unroll it in place) or should I lay the scrim side down first? They say in the technical docs that the scrim is adhered with a resin that dissolves with styrene, so basically the idea is upon layup the resin dissolves the glue is what I gather.

Last question - if I want to double up the thickness of the panels, like I might do for the V-berth to alleviate the need for more structure, can I glue the panels together similarly, and then which side to glue them together on? The scrim or the scored side?

Thanks in advance!

Jon
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  #2  
Old 03-19-2017, 04:21 PM
wet feet wet feet is offline
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It may not be appropriate for a complete beginner,but I would use a vacuum bag to bond the Corecell to the glass.Scored side down and then layup the second side.

I don't entirely understand your question about gluing panels together and so can't really answer it.
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  #3  
Old 03-19-2017, 04:42 PM
leaky leaky is offline
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Thanks!

I get the vacuum bag idea and it'd be great if more builders were doing it that way, for what I need to do and where I'm doing it, I think it just adds $$ time and process without much benefit. If I already had the stuff and the experience with it, I could see it working out, I mean it's great that you can setup the whole thing and get it done perfectly in one layup step..

On the flip side though I don't know how to do it, there's lots of setup involved, and I may just literally be adding one layer of glass to each side of the parts we are talking about, and it's basically a bunk, bathroom walls, stuff like that, not critical hull parts. I do want to do a quality job but in a practical manner too. Do you really gotta do it that way?

The gluing part - I have 5/8 inch and for the v berth it would be nice to have 1+ inch. Since I have plenty of this material, I'm thinking of gluing 2 layers of the panels together to make 1.25 inch. Can that be done and how would you do it?

Jon
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  #4  
Old 03-19-2017, 04:50 PM
leaky leaky is offline
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Like to glue them together was thinking maybe I could use PE or VE, coat the scrim side of one that's laying scored side down, lay the other atop it scrim side down, put something atop to assure it stays flat and under some pressure while the resin cures, the styrene melts the binder and they are bonded with the scrim in suspension, then I have scored side out on both of the new 1.25 inch panel.
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  #5  
Old 03-19-2017, 06:04 PM
ondarvr ondarvr is offline
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Bagging is the best way, and not hard, but it can be done with other methods.

You can lay down and wet out the glass on the flat stock mold surface, pre-wet out the foam, then lay it down on the glass, you need to lay a flat panel on top of the foam with a bit of weight on it to hold the foam flat. When you pull the panel off the mold surface the panel may want to warp because there is only glass on one side. Now you do the same thing again, wet out the glass on your mold surface, put the foam and glass part you made down on it, then weight it down so it makes full contact.

You will normally bed the foam in an overly resin rich CSM layer to ensure full contact and a good bond.


Polyester doesn't make a good glue, so bonding two sheets together with it isn't a good idea, a layer of CSM used in between the panels in the same way will work though. It's hard to get one sided panels made separately to stay flat after you remove them from the mold surface, they will warp (shrink) on the side with the laminate, you may be able to weight them down and get them flat for bonding together though.
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  #6  
Old 03-19-2017, 06:07 PM
Sparky568 Sparky568 is offline
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If I get what you're saying, laying up flat panels for doors, bulkheads etc outside of the hull for installation later. You can use whatever you like for resin, poly VE just put a layer of resin rich mat in between the panels. I have done this before.

Put the parts down on a flat surface (I have 2- 4X8 and 2- 4X4 sheets of Melamine panels for this use). Put some PVA or wax paper in a pinch on the bottom piece of Mel where the edges of the piece will sit in case some resin leaks out. After you lay em' up place on top of the bottom sheet then lay the second piece of Mel down on top and add a little weight, paint cans, concrete blocks (I have several 8X8X8 CMU blocks available at HD for about a buck a piece), etc. It's kinda the opposite of vacuum bagging without the fuss. It will end up stiffer than 1" by itself and you'll destroy the core before you can get them apart.

I guess you got there before me Ond

Last edited by Sparky568 : 03-19-2017 at 06:08 PM. Reason: too late
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Old 03-19-2017, 06:51 PM
leaky leaky is offline
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Thanks guys!

Yes that's right - most of this is all flat panels that I'll build outside the boat then fillet/tab or bolt in after.

So on the standard process where I want just to use a single 5/8 layer of core...

1. I'll make the flat mold, with a release of some sort, lay my glass down, whatever thickness it's going to be...

2. Lay a resin rich layer of CSM down, the "glue", pre wet out the foam, lay the foam down, place something atop the foam to hold it flat while curing...

3. Here's where I wonder (more a question for ondarvr as he mentioned it) - why flip it over and not just lay onto it as it sits on the "mold"? Is it actually going to try and pop off the flat "mold" surface on it's own? Or does it need the pressure on it as it cures?

For at least one of the panels I'm actually going fully encapsulate the core such that the edges are solid glass for through-bolting top & bottom. Will build it up to 3/16 or so on a solid glass strip around the edge. Either way this is do-able, just I may need to complete it in a step #4 if I can't simply glass over the foam from the top in step 3.

Then last question I can think of at the moment (but I'm sure I'll come up with another before this is done!).. Is using VE for this going to be a much better idea? Most of these parts are basically interior and low stress, but I am open to doing it if it makes sense.

In my mind I figured the foam being kinda a weak material as far as getting torn apart, polyester's adhesive properties probably are as strong as the foams will to stay in one piece, or another way to put it no matter what resin you use the peel test will yield the same result because it's not the resin which will fail. Is that true?

Thanks again!

Jon
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Old 03-19-2017, 07:11 PM
ondarvr ondarvr is offline
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VE won't help much on these panels, but could be used.

Flipping it over gives you two finished mold surfaces, which will look much better, you don't need to do it that way though. Keep the laminate on each side of the foam the same thickness, this will help keep it flat.
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  #9  
Old 03-19-2017, 07:23 PM
leaky leaky is offline
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Quote:
Originally Posted by ondarvr View Post
VE won't help much on these panels, but could be used.

Flipping it over gives you two finished mold surfaces, which will look much better, you don't need to do it that way though. Keep the laminate on each side of the foam the same thickness, this will help keep it flat.
Ahh - that's something I did not consider!

For the part I had in mind the non-molded side is hidden, so the finish wouldn't matter..

However for other parts they are viewable on 2 sides, so that makes a lot of sense!

Thanks again!

Jon
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  #10  
Old 03-19-2017, 07:24 PM
Sparky568 Sparky568 is offline
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Yes the VE has better properties than poly. For your use I'm sure poly would work fine. So it becomes a matter of personal preference. Do you need to build a wood frame wall or a brick one? Brick is better and more expensive. If you have to go out and buy VE for this when you have keg or drum of poly I'd use the poly. Remember your already using 50% more resin for the sandwich application. Also, for the bigger panel your going to want to offset the panel seams.
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Old 03-19-2017, 07:57 PM
leaky leaky is offline
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Quote:
Originally Posted by Sparky568 View Post
Yes the VE has better properties than poly. For your use I'm sure poly would work fine. So it becomes a matter of personal preference. Do you need to build a wood frame wall or a brick one? Brick is better and more expensive. If you have to go out and buy VE for this when you have keg or drum of poly I'd use the poly. Remember your already using 50% more resin for the sandwich application. Also, for the bigger panel your going to want to offset the panel seams.
Thanks!

By 50% more you mean due to resin uptake of the foam or by glassing both sides?

What do you mean by offset the panel seams? Like on the panel that ends up being 2X the thickness to stagger the seams?

I haven't ordered resin in bulk but am about to, should have a quote on both Monday, drums and 5 gallon pails PE & VE. I do end up needing some VE for a couple things, and there are a couple things I could go either way on but prefer VE (structural bonds I sleep better at night when I do it with something better than PE). Then there things where it doesn't matter.

Biggest downside of VE ends up being shelf life, otherwise I'd just buy a drum without much thought - I can get through the whole project on a drum, but my understanding is 90 days on the VE and it's shelf life is about up and I don't think I can get through what I gotta do in 90 days.

Anyway - will cost analyze a little, may end up making sense just to accept I'm not going to get the 50 gallon discount and buy 5 gallons at a time based on what I need without any worries on storage, very little waste that way so may cost the same or less in the end. Or might make sense to buy a drum of one or the other and plan to waste it.

Jon
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  #12  
Old 03-19-2017, 08:27 PM
Sparky568 Sparky568 is offline
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Maybe I misunderstood. You mentioned a 7 X 6 panel I assumed you were making 1-1/4" thick out of 2- 5/8". I was referring to laying the second layer of core so no seams between the two layers "match up". That's also referring to the doubling the panels using mat in between the two 5/8" using resin to glue them together. Instead of using 1-1/4" and skinning.

I have also used the mold method ondavr mentioned to save alot of time on the fairing. Just remember a good prep for tabbing into the hull. As far as bulk buying goes. Five gallon pails work for me. I'm part time, back yard Yankee redneck with full time job. I simply can't use enough it in a timely manner to justify a drum. Pails are much easier to handle and store. I typically buy my resin from LBI. Just within driving distance and very helpful. They give a 10 pail discount which is almost good as drum pricing (no shipping charges) which they can also do. Then there's the issue of stirring up the drum. I do notice if I don't stir the pail before using it clumps up at the bottom. There is a technical term for it which I can't remember.

If I can't use a whole pail I'll transfer it to gallon juice jugs to keep exposure to air to a minimum. Then there is also disposal of the drum itself. Any remaining resin you can't get out has to be catylised. This is what I was told from LBI. You can scrape every last ounce out of a pail, a little rinse with acetone and you got a good pail for whatever.
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  #13  
Old 03-19-2017, 09:03 PM
leaky leaky is offline
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Thanks for the tip on LBI ! I'd never heard of them and looking through their site I found a couple hard-to-locate items that are never stocked locally.

CT is a bit of a ride but they could come in very handy when I have a weekend to work on things but need X/Y/Z and it's Friday.

Jon
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