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Hand laminating foam core panels - any tips?


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Q for the resin experts.

I want to laminate some foam core panels to replace some locker partitions and settee backs in the saloon bunks that I've had to cut access through in the boat. 
For some of the bits, it will be easier to make them outside of the boat & then glass them in place.

I was planning to use this foam: 
https://www.easycomposites.co.uk/easycell75-closed-cell-pvc-foam

The originals were part of a moulded in liner & were 
Gelcoat
300gm/m2 CSM
450gm/m2 CSM
Foam Core (expanding polyester foam injected after moulding, about 40kg/m3)
300gm/m2 CSM
450gm/m2 CSM
Gelcoat

For making the panels I'd planned to use Vinylester resin and was thinking that 2 layers of 300gm/m2 biax each side of the foam would be close enough given that its got better properties than CSM & is a better resin. 

Questions:
- Does the above look a suitable layup?
- With Vinylester do I still need a layer of CSM next to the foam & between each layer? Or is it like Epoxy and I can just the biax?
- Can I do one side at a time or will the shrinkage cause the panel to warp? 
- Cut the panel to shape first & laminate it, or just laminate big panels & cut the parts out of that?
- Is it worth using peel ply with vinylester as it doesn't blush? 

Cheers!

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Well, no expert but I am curious if you have a vacuum pump available or some other method to press the panels?

As far as I understand it(and from the sandwich panels I diy) there is no need for chopped strand anywhere in your build.

Peel ply, what kind of surface finish are you looking for? In other words, if you still need to paint and require a keyed up surface, then yes.

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No vacuum pump, I was hoping to avoid infusing or bagging as its a load more equipment to purchase and I'm not sure if I'd get much use out of it. 
That said if its the only way to do the job properly then i'll get one. 
I was thinking I could press it by covering a piece of plywood in some sort of release film & piling heavy shit on top. Always nice to hear from someone who's done it though. 

Finish will most likely be a paint, I don't want gelcoat as I'll have to bond & glass these panels into place.

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35 minutes ago, MiddayGun said:

- Does the above look a suitable layup?

For locker partitions that somebody is not leaning against, you can get away with a single layer of 300 gm/m2 each side.

For settee backs that might be bigger or heavily loaded by sails, big drunk sailors falling on them, then I would go with 2 layers x 300 0/90 or +/-45  each side.

35 minutes ago, MiddayGun said:

- With Vinylester do I still need a layer of CSM next to the foam & between each layer? Or is it like Epoxy and I can just the biax?

No CSM needed. 

35 minutes ago, MiddayGun said:

- Can I do one side at a time or will the shrinkage cause the panel to warp? 

Hmm good question. I'd say no problem if you put some weights on the top surface until the resin cures. I generally use epoxy so shrinkage is less of an issue.

35 minutes ago, MiddayGun said:

- Cut the panel to shape first & laminate it, or just laminate big panels & cut the parts out of that?

++ 1 big panel and then cut pieces out of it. Laminating lots of little bits is very fiddly and the unfinished edges will have raw spikey bits of glass.

Use a jigsaw blade with carbide grit on it to cut out the pieces, even if you have to search a bit to find one. So much better than wearing out bi-metal blades.

35 minutes ago, MiddayGun said:

- Is it worth using peel ply with vinylester as it doesn't blush? 

No need for peel ply.

Laminate against a flat table that has been covered with mold release/wax. A sheet of plywood on sawhorses with a covering of cheap pressure laminate in an ugly color nobody wanted to buy ("Formica" brand name in N.America) OR a piece of particle board with melamine finish both make good surfaces. Wax both several times.

So step 1 / stack = 

mold table
wax
glass layer, wetted out
foam core
weights

<let cure>
<remove from table, flip over>

step 2

mold table
wax
opposite glass layer, wetted out
       then add:
foam core with previously cured glass layer on other side
weights

I'd use 12mm / 1/2" core thickness as a bit of a guess, depending on span/fitting into existing thickness of cabinetry etc.

Cut out pieces, coat edges with thickened epoxy if they are going to be exposed. If all glassed in no need to treat edges.

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Cheers @Zonker I think that basically covers everything.

Final Q, if I want to make a panel that's longer than the largest core size I can get, do I need to scarf two pieces of core together, or can I get away with butting them up to each other with maybe some thickened resin inbetween them?

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Everything he said, except, rather than carbide grit blades, spring for the carbide toothed wood blades, I believe festool and maybe Diablo or Lennox make them now.  Much less burning, generally an equally nice easily sanded cut and long wearing. Just used one in some 1.5" solid glass actually.  

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I experimented with making non-structural panels like that using 1/8" ply and cheap pink insulation foam.

Epoxied the panels and weighted them with some old weight machine weights.

It worked great - quick, cheap, simple and stiff as 3/4" ply but less than one Lb per Sq Ft.

Way easier, cleaner, cheaper etc. than laminating glass over expensive structural foam.

This one was to fit between bulkheads so I didn't bother putting anything solid along the edges when I laid them up, just coated the foam with epoxy to seal it.

 

Shelf 1.JPG

Shelf 2.JPG

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Cheers John, I'll may try and get something like that for the bits that don't need any strength. Although that pink stuff you guys get isn't all that common over here, insulation foam is normally a minimum of 25mm thick. 

For the bunk areas I'll stick with the stuff above, I don't know how much structure what was there had been providing, but I may as well make sure whatever goes in is stronger.

I'll try the carbide blades suggested above as well. 

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1 hour ago, Zonker said:

The pink stuff is OK if you don't consider them very structural. The shear strength of that type of foam is quite low. (about 1/4-1/5 of a PVC boat building type foam).

 

"Structural" wasn't even considered - strictly for panels like shelves, dividers, maybe locker doors and so forth.

I might consider an application like the door to a head compartment - with some suitable solid edging around the perimeter.

I was pleasantly surprised by the strength and stiffness it achieves - it was better than I even hoped for.

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14 minutes ago, MiddayGun said:

Cheers John, I'll may try and get something like that for the bits that don't need any strength. Although that pink stuff you guys get isn't all that common over here, insulation foam is normally a minimum of 25mm thick.

The thinnest I could find was 12 MM (1/2") so a 3/4" finished panel is the best you can get - too thick for many possible applications.

I did use it for a new galley counter top - laminate epoxied on the top and 1/2" coated ply on the bottom with 1/2" square cedar framing the foam in. It worked like a charm - totally solid and lighter than the 1/2" ply/laminate it replaced. The pic is not the best but it give you an idea of what can be done with this method.

I will eventually have to make new flats for my 1/4 berths - they are currently 1/4" ply with a coating of mat. I suspect my foam core idea will be an improvement on that.

companion 5.JPG

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3 hours ago, Zonker said:

Butt with thickened resin is totally fine. The joint will  be stronger than the foam.

If building a box would you want to make individual panels with a solid wood edge (foam thickness X ~1")? 

And if this was a box to cover the forward end of an inboard would it be louder, quieter, or no different? 

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If the foam was that thick I'd just tape over the edge with 3 or 4" wide glass tape.

But nothing wrong with wood. If you want to get fancy you rout out the core ~1/2 the depth of the wood so the wood sticks out of the glass a bit. Or take the foam core, glue wood strips around the edges, then cover the panel with glass. Lots of ways to do it. 

For the outboard cover - the gap is what matters. Think of noise like water leaking out. Put a gasket on the edge so it makes a good seal with whatever and it will be quiet. Have a 1/4" gap and it will be much noisier.

Also - make the box slightly bigger and line the box with sound absorbing foam. To let the outboard breathe make sure any openings are baffled so there is no direct line of sight to the noise source.

image.thumb.png.df41d7eb769f3f79b05951dffa56c6a7.png

 

 

 

 

 

 

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Recently hand laminatated panels for an efficient low HP runabout. 400 DB each side of 10mm Divinicell with epoxy and peel ply. 
 

Hand laminated and peel plied one side at a time using a  flat 200 mm drywall spatula.  Warping not a problem with the epoxy. Make sure the peel ply is in smaller sections as the peel ply can relax over a 1200 x 2400 sheet and leave a wrinkled finish.

Foam scraps joined with fairing compound and held in place with short staples shot through plastic film to keep the edges aligned while setting. Staples easily removed by pulling off the plastic complete with staple.

flip panel when set and lay up other side. Very quick and easy.

Pictures show surface finish PP still on , and a panel with joins in foam.

C04A5AA5-BDEB-41D0-904C-9EFCE09086D6.jpeg

DA1FA459-7B22-4803-AF7C-E97F6BE596F3.jpeg

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Very nice work so far. What are the darker shadows in the 2nd photo?

Being a cheap bastard I would go to the fabric store and look in their remnants section for ripstop nylon in gaudy colours. Usually picked it up for $1-2/m. I used that in place of peel ply. Now this does have the possibility of contamination but any future bonding or painting surfaces always got a solvent wipe and sanding where required. If a fabric felt like it had a silicone or DWR (durable water resistant) coating I would not use it.

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1 hour ago, Zonker said:

What are the darker shadows in the 2nd photo?

 

Shadows through corrugated polycarbonate skylight.

Not meaning to hijack the thread.

Panels stuck together PP mostly still on.

CC275AD4-C8BC-4DD1-83D3-5B78B55D105A.thumb.jpeg.e64d7a2bbd8333f8df6adeb18b14ac75.jpeg
 

6meters x 1 meter x 80 kg. 12.5 knots with 4 HP and 2 adults.

93C54C61-BD83-4A1B-94FB-2DD351ED8B7C.thumb.jpeg.7bab08e4679e7b685088e80302d0134a.jpeg

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17 minutes ago, Zonker said:

Long and skinny for the win. Very nice efficiency to get that speed with such a small motor and payload.

Original goal was 10 knots with 2.5 2 stroke tender motor I had in the shed. Managed 9.7 knots.

4 HP 4 stroke is so much more fuel efficient, plus it has reverse. :)

Inspiration from Bermuda Seagull challenge boats, but as you know they are a lot longer ,narrower and faster, but this one has to carry our fortnightly shopping safely.

 

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  • 2 weeks later...

I used 2” pink Corning foam for seats for my outrigger canoe; they span a 20” gap between gunnel and alum pipes which support shrouds and iakos.

Rounded the edges. Covered the foam with doorskin on top, one layer 6oz wrapped on top and two below. Experimented with peel ply substitute from Arts&Crafts store, pillow stuffing, vacuum sealer bags usually for storing sweaters and stuff.

Supported the edges and jumped on them to test. Perfect! Painted with house paint. They live outside.

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On 11/29/2021 at 10:35 AM, Zonker said:

Very nice work so far. What are the darker shadows in the 2nd photo?

Being a cheap bastard I would go to the fabric store and look in their remnants section for ripstop nylon in gaudy colours. Usually picked it up for $1-2/m. I used that in place of peel ply. Now this does have the possibility of contamination but any future bonding or painting surfaces always got a solvent wipe and sanding where required. If a fabric felt like it had a silicone or DWR (durable water resistant) coating I would not use it.

being a cheap bastard, I would order econo ply as it is the right stuff to use and wont fuck you down the road.

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  • 2 months later...

Just touching on this again, not far off this project now.

Some of these panels will have a painted finish, probably glassed into place. 

The peel ply / biax, leaves an uneven surface, would it be better to fair these off the boat when I can lay them flat & just leave an area around the edge for the tabbing? 

And along that thought, are there any tricks for fairing when laying it up? 
Like making the layer against the table very resin rich to fill in the weave? 

 

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1 hour ago, MiddayGun said:

And along that thought, are there any tricks for fairing when laying it up? 
Like making the layer against the table very resin rich to fill in the weave? 

What do you mean here, ensuring that the surface Close to perfect once separated from the waxed surface?

i don‘t think I had an issue up to now since hand layup is usually a bit resin rich and weight then compresses...

You can always start with a layer of brushed on epoxy, wait until it sets enough to only be tacky anymore, and then start properly laminating with a new batch. 

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43 minutes ago, allweather said:

What do you mean here, ensuring that the surface Close to perfect once separated from the waxed surface?

 

Yes, pretty much that, presumably to get a good finish normally, you'd need to skim the surface with filler, and then flat it back. Then do the other side, somewhat labour intensive.
I was hoping that maybe the same could be achieved with a resin rich surface

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Ok I assume you didn't lay these up on a flat smooth mold table surface? 

Did you have peel ply on both sides?

Anyway the peel ply surface is just tiny little nubs of textured resin. You can easily sand it flat. I wouldn't even add filler.

If you use a flat mold surface you can use

- use a single layer of CSM (very common)
- use a "surface veil" looks sort of like sturdy tissue paper (not common) but much lighter than regular 3/4 oz / 200 gm CSM. Typically you can get it as light as 50 gm

Just biaxial against a smooth mold surface will leave little pits in the surface which you can fill with filler.

I have not tried just brushing on a thick layer of resin and letting it tack up. Probably would work OK. Basically doing the same thing as gelcoat in a mold but typically gelcoat is backed up with CSM.

 

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@ZonkerNot made them yet, hoping to on my next leave.

I had a bit of a brain fart last night and had in my head that your laminate stack started off with peel ply. But of course if I do it against a melamine surface table then it should be nice & fair already.
 

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38 minutes ago, MiddayGun said:

@ZonkerNot made them yet, hoping to on my next leave.

I had a bit of a brain fart last night and had in my head that your laminate stack started off with peel ply. But of course if I do it against a melamine surface table then it should be nice & fair already.
 

Not sure what your building but remember  the value of postcuring ….reduced print thru and increased mechanical properties 

 

the poor man’s post cure oven is the sun, and a black plastic sheet 

typically the component is constructed , faired, primed …then post cured…then board sanded again and  painted 

 

if you have any sun it’s worthwhile 

 

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1 hour ago, MiddayGun said:

@ZonkerNot made them yet, hoping to on my next leave.

I had a bit of a brain fart last night and had in my head that your laminate stack started off with peel ply. But of course if I do it against a melamine surface table then it should be nice & fair already.
 

Having a laminate faced panel for the top as well should give you what you want - wax the table, wax the top panel, lay up the laminate, put the top panel on, add weights to "clamp" it all and voila.

Essentially you make a flat panel mould.

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1 hour ago, SloopJonB said:

Having a laminate faced panel for the top as well should give you what you want - wax the table, wax the top panel, lay up the laminate, put the top panel on, add weights to "clamp" it all and voila.

Essentially you make a flat panel mould.

I had planned to do one side at a time, but I suppose that's one way of doing it more quickly. 

@slug zitski no chance of a post cure here, middle of the UK winter right now, I can't even remember what the sun looks like anymore. 
 

My main bulkhead needs doing while I've got the boat in bits and I had thought about a foam core one, but I read somewhere that 19mm H80 foam with 1200gsm on each side was only equivalent to 9mm plywood strength wise (obviously a lot stiffer), and as my bulkhead is 12mm ply, it seemed like probably too much effort to go to for a small weight saving, so I'll replace  with plywood again. 

These panels are for lockers / cabinetry, fairly non stressed stuff. 

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No need for post curing these basically non-structural parts.

Post curing only works if the epoxy is designed for it. Lots of room temp epoxies won't have better mechanical properties.

AND some of the PVC cores (I'm looking at you Dinvycell) offgas when heated. That blows the laminate off the core. 

Unless you really know what you are doing (ramp profiles/dwell), well controlled temperatures you are liable to do more harm than good.

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Well I'm all for being lazy and saving work. 

And lets be honest, this boat was built in the eighties with chopped stand matt and some woven roving's in polyester resin. 
All this stuff would be overkill. 

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