Pleased to report that with helpful advice from your tech team and some forum members I have now successfully made up 6 flat c/f panels in 195 gsm varying from rectangular 400 x 400 mm to triangular 2200 x 450mm by resin infusion. All have eventually come out without voids (yipee), there was some scrap. They only worked well once I heated the layup table to 22c, and heated the resin as it flowed with a hot air gun. I did use a lot more resin than in your tables, but the surplus came off in the peel ply. My panels are 0.35mm thick.

Now can you you help me with sticking these on my grp boat?  I have coarse sanded all the grp, 80 grit. I cannot control the temperature which is ambient in a big steel shed, currently 3c and 65% humididty. I therefore cannot use epoxy the glue them down, because any minor  uneven heating / cooling causes ripples, I have tried. The surface is compound curve, just, but I have formed the panels dry, by heating them till flexible and taping them down to cool. (It works!) I favour using pu 18 adhesive as it is flexible and waterproof, but how on earth do I get an even thicknes of such a thick sticky adhesive over such a big area??? and how do I keep the panels even on top of the adhesive?? Any advice and or clues would be greatly appreciated.

I don't know what your shapes around  the area   you are working on so ignore me if this is totally useless for your situation 

Thanks Bruce, yes i can mask around the part and put bagging film over, i can see that would also result in very even pressure all over. Good idea.. I am still concerned about applying the PU 18 though, anyone know how thick it is to apply? can i for example spread it out with an adhesive comb after applying lines of it from the gun? anyone used it? what do tech support think?

Good idea bruce!!

PU18 can be spread using a tool like an adhesive comb.  I have spread it for when doing my bonnet for bonding two parts together.  I just used a credit card sized piece of plastic.

You can thin PU18 down with acetone to a thinner consistancy. I have done this before to paint the black borders around a car window.

however try this on a test piece first as im not sure on the effect of its bonding ability the acetone will have. 

Hi ezsailor,

Sorry for the late replay, I've been away for a few days and the rest of the guys in the office have been flat-out. I'm glad you got the sheets spot-on in the end so it's on to the next tricky thing!

Bonding such thin sheets without any rippling is always going to be a bit of a challenge because as you now a slight variation in the thickness of the adhesive will show through. For this reason it strikes me that you need a thin resin rather than a thick adhesive. The problem, as you've already mentioned, is your ambient temperature. Because the panels are large and I suspect that, as Bruce has pointed out, vacuum bonding would be the preferable way of holding them in place you're going to need a decent working time which rules out using a very reactive resin to overcome the cold working environment. Is there no way you can use some localised heating (like halogen lamps) shone on the surface after bonding to get some heat into the panels (and the adhesive underneath). In my experience, even though these halogen lamps might have little impact on the ambient temperature in such a large cold room they can be very effective at heating the surface of the part/mould and so might be a solution to an otherwise difficult problem.

You say you've opted for PU18 because it's flexible and waterproof (which indeed it is) but water would be no problem for any of our epoxy resins or adhesives, or a methacrylate or polyurethane. As for the flexibility, how much 'flex' do you need or anticipate?

--Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

Iv'e been away for a couple of days as well. Thanks for the reply. Flexing is fairly small in terms of twist, probably less than 2mm in 500. But downwards deflection could be as much as 10mm in the 300 mm between the deck ribs, if you accidentally stand on it (easily done)  I see what you are saying about uneven resin thickness though. I tried epoxy resin with and without filler powder, seemed not to make a difference. Got two on perfect, and four were awful next morning. I was lucky to go very early and managed to rip them off before they were properly cured.

I thought of PU18 because I am familiar with sicoflex, and know you can spread that with an adhesive comb to a fairly even coat, while leaving some thickness to take up very small imperfections in the substrate. Supreme being says it can be combed, and if I smooth it down with a 500mm  long board with layers of soft cloth on the edge (which must help to even it out) and then vac it down do you think I would get better control over it? I could try the smallest piece first. I have to get this right now, the other guys in my club already think I am some sort of magician.

PS Actually Matt I think what's causing the ripples/big air bubbles is the lack of initial grab that epoxy suffers from. Where they appeared could be clearly seen on the underside  when the sheet was removed, lots of tiny pointed peaks where the bubbles were, and clear combed flat lines where it gripped. Does PU18 have better initial grab?  Using vac to hold down will help to overcome this premature release? Thanks.

Can you get a photo of the deck ribbing and the gap between them?

The 2mm deflection in 500mm is no problem whatsoever.

Of more concern is the gap between the deck ribs. The way you describe it, it seems like you are laying the carbon sheet over the deckribs meaning it would naturally sag into the gap between sheet and deck material.

Can you take a photo or describe what you mean and  I will endeavour to give some more advice.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Hi Warren. Sorry not to be fully clear.  The boat is 30 years old, GRP moulded decks laid in female mould and ribs bonded  in place, then bnoded on to the hull. As it is a racing dinghy/sailboat the decks are very light and we are not supposed to stand on them.  They have softened a bit since new, and the idea of using c/f was twofold. Principally to make awesome decoration, secondly to put back a little of the lost stiffness. I have taken out the very slight sag between the ribs, about 2mm, with epoxy and glass bubble filler, and sanded fair. There is a curve from centre to side, 35mm over 450, and a very slight curve for and aft, not measured but about 10mm in 1800. That causes a slight springiness in my panel which is .35mm thick.  When I try and stick it down it goes on ok, especially when heated with hot air gun. I am working in a large steel workshop, unheated except for my fan heater which I direct under the deck. Surface temp about 15 deg max. I am not allowed to leave the heater on when I go home, fire regs. At that stage everything looks great.  It's only over night that the bubbles/wrinkles appear. That is what leads me to think the epoxy is not grabbing and setting fast enough. Also I was able next morning to lift the edge of my wrinkled panel with a blade and then literally rip it off, so definitely not cured. I have rescued and cleaned all the residue off thank goodness. I can't photograph the boat as is till Monday and my only pics are 14mb which won't upload .Writing to you guys does really  help the thinking by the way, it clarifies the issues a bit.  I guess the real question is in the conditions I am forced to work under will PU 18 combed evenly and then either squegee the panel in place and or then vacced down give me a better chance of success? My squegee is long enough to span two ribs, 10mm thick covered in 5mm hard foam and towelling to prevent scratches. Similar boat pic above, will give you an idea of the curves involved. Welcome by the way, and thanks. Mike.

Thanks for the photo, it has cleared up a potentially confusing situation!

Based on the information you have given, the temperature is your main issue, so you need an adhesive that will mostly cure in the time you are present (and hence can keep it heated).  Our PU18 Black Flexible Polyurethane Adhesive would work nicely in that sense. It can be spread using a spreader and will "skin" in approximately 70 minutes (once a skin has formed, in essence the outside of the blob of glue has cured, you'd need to remove that skin if you had left a piece too long).

That would give you a decent working time to align a panel and put it into place.  I would recommend weighing it down to help it stay in place.  If you still have issues then try vacuuming the panel in place.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant