Finally !!

Herman suggested i take some pictures up close of foam so with a hour to kill this morning this is what i came up with !
The foam i used is H80 DIVINICELL (its all i could find here )
I Broke the edge of the foam and also cut a edge !! Its interesting the differance !.
Seeing this in close up has deffinitly changed my whole concept of foam and has made me lean even more towards Balsa as a core material . I can now see why foam peels off the glass as there is almost no penetration deepth at all !! its almost like a surface contact the interface between the resin and the foam .
The thin slices i was able to see the light throught and gave a better veiw of the bubble thing

I think i would trust Balsa more than Foam in a life threatening situation thats for sure !!
Still thats only my veiws and what do i know !!!
You make up you own minds !

 

Cool pics.

 

Glad you like them !
I tried to get some of Balsa as well but couldnt get the grain to show up .

The foam is scary and ive changed my mind even more after sitting looking at these pictures for a while , i have a greater understanding of how the foam peels off the glass and how weak it really is in peel mode !!

 

I wonder how much change in peel strength a little surface treatment on the foam would make, something that would add a little roughness to give more "tooth" for the resin to grab unto. Like a light scarfing of the surface with a heavy grit sandpaper and then vacuumed to remove all dust.

 

Peel !! something quite differant to think on !!

I had laid a lot foam over a long time and was alway in favor of using foams till i began to look much more closely at the surface and as the density went up so the grain or pores of the foam became smaller so i paid much more attention to the surface wet out and priming and rolled it twice about 5 minutes between each coat of resin , We were making large panels and some were doubled in size and got cut in half because they were the same laminate , One of these panels was carried out and as it was going across the yard one corner got dropped and as someone grabbed at it the only got the top skin and behold it simply peeled off !!! all happened in less than a second and was total and complete ,The bond was 100% but had sheared a layer of foam just a couple of mm's below the resin bond line . Immediatly we took it back into the factory and resin coated both surfaces and bagged it and sucked it down gently and it was restuck a 100% ok the next morning . I followed the panel till it was all used up and collected all the off cuts and scraps I was absolutly amazed at how easy the glass peeled and how clean almost like a hot wire cut .so from then on i kept off cuts of every panel we made and the ease of peel was always the same the thickness of glass each side didn make much differance !!
Please take note i am talking about peel not delamination "ITS PEEL" !!! This is something quite differant !! you can stick things and the hold is really good but peel can be quite easy !!
Stick ability and peel !!!!

I must make time and do some balsa samples to test out peelablility . I have seem glass layers part off balsa but never actually peel off the balsa its self !!

 

Balsa = rot.

You should see the old Tornado cat in my back yard. Soon I am going to cut into it to see if it should go to the dump.

Perhaps you should groove the surface of the foam like a notched trowel, in order to get more glue contact area. This just gives more surface area, the actual peeling surface strength would be the same.

 

Since i did those big panels theres lot differant cits of foam come on the market ! theres a one that really makes a lot of sense !,the foam is cut 60% one way and 60% at 90 degrees so the cuts cross each other inside ! i have used that and its me !! the resin penetrates from bottom to top and fills the grooves and its tied together only thing would be nice to see the company run glass strands inside the grooves and then you would really be smoking !!.

While i worked in Korea we used Polyuretane sheets the had long strand csm mixed with the foam ! ,wow it was good to use and to glass over ,held dead straight even in the weather outside !!.off cuts and scraps that had been in the rain and sun for months didnt matter just changed colour thats all !!
I have never seen it anywhere else . The foam came from a manufacture that made cladding panels for outside of buildings ,that were coloured aluminium sheathed inside and out !!.
We bought and used just the foam to make formers to glass over for stringers etc etc

 

Your description on your panel corner is very common. Hand laminate or infusion panel, i can peel off the fabric by hands if it gives me a corner. Not only those cores present like this, the fabric does too. I can peel off those fabric layers one by one in my hands,if you would like to do a test to confirm.
In my mind, the only merit of core is it can be infused, balsa can't.

 

http://www.nrca.net/rp/technical/manual/06pdfs/99_100.pdf

http://www.mid-atlanticfoam.com/roofing/polyisocyanurate.asp

This might be what it was. It's the most common commercial roofing insulation here in the US, used under tin or on flat roofs that are hot or cold mopped asphalt tar. I believe it's used in structurally insulated panels (SIPs) also. Walk in cooler walls. Various kinds of facings, or none, various densities, various sizes. All at industrial/commercial, huge supply, commonly available, highly competitive, basic construction material, wholesale, non-marine prices. The foam itself is usually laced with fiberglass strands, if you break it you can see them, if you cut it, after awhile you can feel it. Polyester resin doesn't bother it. It's the same stuff Carolina Skiffs used in their original flat bottom boats.

 

A couple of random remarks:

PU foam with random strand of glass: Airex PXc foam. (former Penske Boards)



PU foam with regular glass rovings stitched through: Structiso



Balsa not infusable? Why not? We infused loads of balsa structures, including 23 meter boats, windmill blades, etc etc, without any problem.

On balsa and rot: The equation is not correct:

balsa + bad workmanship = rot

 

Sorry for my ignorance, i did't infuse balsa stuff because the balsa here does not have slots and holes.

 

You do not need slots and holes. If you take the scrimmed balsa you have enough resin paths for the resin to even out top and bottom, and your bottom laminate can be taylored to have enough flow not to cause any problems or dry spots. Also overall infusion speed is important here.

 

It sounds right, if the infusion speed goes to fast, the bottom of balsa would be dry.Low speed is not my infusion style, that is why i thought balsa is not infusable.

 

Low speed is not bad. Infusion of larger objects is about quality, not speed. I usually aim to have a complete fill in about 2-3 hours for epoxy, or 1-2 hours for vinylester or polyester.

Just make sure you have enough working time with your resins.

 

Large project should be infused asap, the longer, the dangerer (Believe me, i have met one situation that one guy shut down my pump during the infusion).That is my style. I have infused 75ft hull in 70mins with vinylester, 60ft hull in 80 mins with epoxy, they both look great(We didn't put on gelcoat so we can see it clearly). Because it is big, when there is dry spot at the beginning during the infusion, it will finally wet out.
But if there is no core area or thicker layer(maybe 20), i will slow the resin down, even remove the flow media.