Polycore

Yep, i doubt theres a single person reading this that doesnt understand whats going on here...

For the record, i Build in an identical method to the one youve just shown in the PDF you attached.... For the same weight polycore panel with 0.5mm skins, 3.7kgs / m2, i have a 15mm core with 600gsm dbias structural laminate both sides, perfectly fair, and ready to paint (no pinholes). Adding this laminate results in 2.4kg extra weight per m^2 plus the cost of the resin and glass to lay it, and now i have glass overlaps to fair out...

Lets look at the trade off? Cost...

i make my own infused foam core sandwich panels for just on $100 per m^2. Thats 80kg foam, and 600gsm e-glass epoxy skins, peel ply both sides. In a small shed it takes me around 0.6 hours per m^2 in labour time - i could cut this in half with a bigger commercial shed.

Using pre-glassed polycore @ $77 per meter, i have to add 1.2kgs of e-glass, 1.2kgs of epoxy, and 2m of peelply to save sanding later. Thats $12 for the glass, $24 for the epoxy, and $4 for the peel ply. Total = $77 + $12 + $24 = $113 per m^2. Its too difficult to work out how much labour it would take to apply the laminate, and then do the fairing and preperation for paint, but there is no doubt in my mind that it would be an order of magnitude greater than 0.6hours per m^2 considering both sides need to be done allowing a cure for each side between.

So net result, costs me more in money $100 vs $114, costs me more in time, and my finished structure is 2.4kgs per meter^2 heavier based on a 600gsm structural laminate.

 

I'm having just a bit of a problem understanding your posting Should it read a little differently?

Should that read like this?

 

That was an interesting comparison Groper. I looked up a number of other subject threads that were started by yourself, and found lots of interesting discussions and photos of your experiments with building. I need to do some reviews of that info as well.

I would ask if you have experimented with Derek Kellsall' KSS building system? He ends up with 'finished panels' if I remember correctly. I'll have to look at that again as well.

 

Basically yes Brian, i make my own panels using foam core rather than polycore. I cant use polycore because i make the panels via resin infusion, and the cells would thus fill with resin.

My 15mm thickness, 80kg/m3 foam core panels with 600gsm dbias eglass epoxy structural laminate weighs 3.7kg per m^2. The polycore panels with the minimum 0.5mm skin thickness, weighs the same. However there is no structural laminate on them. To add another 600gsm dbias laminate onto the polycore preglassed panels, adds 600grams of fibre to both sides, and 600grams of resin to both sides - an extra 2.4kg heavier per square meter of panel area or approx 60% increase.

The other point i was trying to make, is that after adding this laminate, ive also spent more money compared to if i just make my own panels from scratch.

The icing on the cake, is that after wetlaminating over the preglassed panels, you then have glass overlaps to fair out, which is a horrible thought considering one started with already fair panels!

I dont understand the mentality of offering such a product for sale, unless strictly used in non structural applications where no additional laminate needs to be applied....???

 

This is how she answered this earlier:

Hopefully, if there is sufficient demand, they could provide the options that you have described.

 

I basically emulate kelsalls KSS system. The key difference that sets his method apart from all the other flat panel building methods, is the way he lofts the hull profile, makes appropriate dart cuts, and folds the panel in order to get a slight compound curvature in the bilge area - which needs wet laminating over and fairing out. Not such a problem as this area is all below waterline and covered in antifoul so the fairing job doesnt have to be perfect / meticulous.

Its a good way to go IMHO, but i think one would need experience with the materials and their flexibility, and the designer has to be able to loft the profile and dart cuts.

If you wish to pull finished gelcoated topsides from the table, then the table also needs to be perfect, you cant just slap a few sheets of MDF together and expect a satifactory result. Your also subscribing to vinylester or PE resins do this aswell. Ive managed to use epoxy highbuild paints as a gelcoat of sorts and infuse epoxy over it, works well if you understand whats happening in a bit more detail...

 

Doesn't the initial layer of glass that Polycore is offering to apply to those panels (I think thru vacuum methods in a controlled manner) block the cells from being filled with subsequent resin application? Isn't this thin 'initial coat' completely cured, and relatively non-porous?

 

Well best to direct that question to Maggie... but going by this;

Id say NO, it doesnt look like the core completely sealed off as it appears they have outgassing issues when they apply the skins to these panels. I can understand this as the core is full of air in between the cells. When cured in an oven, the air expands and makes little vent holes in the laminate.


ATL`s duflex panels have the same problem, there is some pinholing present in the laminate and so they recommend a squeegee coat by the user to seal the panels.

Id hazard a guess that these panels are not made in a vacuum as per the comment by a 3rd party in that PDF you showed us earlier. Id say its more likely that the panels are made with a prepreg applied to the core and cured in a heated platen press / oven or something along those lines - im only guessing tho. I was referring to vacuum infusion using just the polycore as a core itself - not the preglassed panels. Due to the open nature of the polycore, its not compatible with resin infusion or the whole thing will fill with resin and turn into a solid block.

If we assume the preglassed polycore panels are not porous, it still does not make any sense to use it with resin infusion, because again it would end up heavier and much more expensive than simply using a raw foam core...

Thus it seems to me, that one has little choice but revert back to old school, large scale wet laminating techniques if using this preglassed panel. You basically build the boat shape using the panels, bending them, torturing them etc, then once you have a hull or a deck layed out, drape over your reinforcement and go like crazy wetting it out. Once your done, youll have to fair out the glass overlaps and any other lumps and bumps you made along the way. Basically identical to a glass over ply build...

 

Infusion Grade PP Core & Kelsall Method

As previously stated I wanted to look more closely at the possibilities of utilizing PP cores vs balsa, foams, and other honeycomb materials. I am also looking closely at 'panel construction methods' where these 'panels' are prefabricated to some degree much like the kit-boat builders in NZ and Australia are using. As I look more closely at these prefabricated 'cored panels' I find that they are basically only supplied with a 'basic skin' to which each different builder will have to apply his own additional skin layup to obtain the strength he is seeking. That additional layup is done in free-stream without a mold surface. Therefore it will require additional fairing work to obtan a smooth finish coat. That additional fairing work can be very time consuming.

Contrast that with Derek Kelsall's method of producing his panels ona smooth table, and arriving at a fine finish on the outer surface of his panel. Derek is also almost making exclusive use of resin infusion to build his panels, which makes for a nice uniform panel without resin starvation, and with likely very good bonding between the core and skins.
http://www.kelsall.com/UniqueKSS/WhatIsKSS.pdf

One problem might be that Derek, and several others, insist on using only foam as a core material, particularly sense it stands up under the resin infusion process.

So I'm reading a little more closely and I discover Plascore is now making a "Infusion Grade PP Core"
Infusion Grade PP Honeycomb - PP Honeycomb

 

I read the brochure Brian, seems a step in the right direction with PP cores.

2 things,

First is it has a lower shear strength than the same density structural foam cores. But it has a higher compressive strength, which is why it does better in impact testing.

Second is the finished weight, they peirce a cell every 4 inch to allow resin through the core to the feed the tool side laminate of the sandwich in the infusion process. The brochure says the cells are 8mm dia, so those cells end up filled with resin. Foam cores can be perforated the same spacing, but the holes are only 2mm dia, this means about 16 times less resin trapped in the core- which becomes a significant amount in terms of cost and weight. I'd also worry about exotherm if using a styrene resin and gel coat, it may create spots in the finish where the open cells are. A 4 inch spacing can likely cause infusion problems as well, most go down to a 2 or 1 inch spacing to prevent fibre lockouts between perforations.

The added volume equates to an extra 370grams of resin per square meter in a 20mm thick core compared to foam- a 25% increase in core weight.

 

I saw one of the only 3 solitary island 40 kits being built today. Quite an impressive boat and the kit has a modern build method and comprehensive set of plans and building instructions, im surprised they didnt sell more of these before going belly up?

Anyway brian, these kits came with preglassed structural panels - they had a dbl bias stitched laminate on all the panels from which the boat developed plates were CNC routered. So the only additional laminates required, are where the extra reinforcing is needed such as main beams, structural bulkhead cutouts etc. The rest of the panels are good to just go ahead and assemble and had only a very slight bump down the center of the panel where the glass overlap was. Otherwise, the panels were very fair and looked good, almost zero fairing provided you dont introduce any unfair curves when you bend or twist them into shape around the bulkheads - there is always some error tho unless you have some sophisticated alignment jig for setting them all up.

The hull shoes were supplied as a premade component of the kit, in infused PVC foam sandwich from a female mold, as its all compound curved / round bilge deemed too much work for an easy assemble, otherwise flat panel kit.

All in all, a pretty good kit IMHO, the guy building it is doing a great job by himself. These structural polycore panels with dbl bias on them, looked like good boat building material.

 

I thought is was a very professional put together project as well. I even drew up a slight modification for it to have a mast-aft option desired by a potential client of mine....that fell thru though.

...slight stern mod and aft-mast




I think they just had to face the reality that the boat market wasn't going to be much after that market crash we had here in the USA (and worldwide). It was probably going to be a big cash drain to try and slip thru the next few years until things got better.

I suspect they closed things up in such a manner that it could be restarted again, either by themselves, or sold off to someone. Even now it might be to early to restart,...in my opinion.

 

I just started thru this older subject thread in review, so excuse me if I an behind the times.

Has anyone seen this subject thread (abbreviated) about the power catamaran in Thailand with water incursion to the core problems?

I'll have to find that link and post it. Ah, here it is:
http://www.boatdesign.net/forums/materials/repair-water-core-material-fibreglass-boat-56743.html

 

I have always wondered about the total integrity of this welding (fusion process)?
And secondly, I have wondered about the 'permeability' of this scrim to water ingress.??