I finished making the kite board, and I have a serious problem, the resin has become very fragile, in other tests on plates, the resin is kept very flexible and very deficil reach the breaking point, the opposite of the remains of the plate that I cut the kite board, I have fear that can break a strong shock in the water. What is the problem? The board is made with carbon fiber cloth 200g/m2, 290g/m2 Diolen, soric 2mm, 450g/m2 carbon fiber, pvc foam 5mm soric 2mm, 290g/m2 Diolen lastly fiberglass 160g/m2 the resin used was the slow hardening epoxy el2, 24h curing, a post cure of 4 hours at 55 °. In tests in which the resin maintains the properties that I wish were made with fast hardener and became a postcure of 3 hours at 75/80 º. Another cause of error could be an excess of resin? the kiteboard has an excess of resin, can this make it more fragile? I fix this excess manufacturing it by infusion rather than lamination? 

www.ktuning.es  

Hi Manu,

It's difficult to pin-point exactly what the problem might be, certainly the EL2 laminating resin will cure to be very hard indeed and will have the properties that you desire (as indicated, if I understand you correctly, by the fact that a sample you've made with the EL2 and a fast hardener have cured well and given you the performance you expected). The obvioius explaination is under-curing and I'm pretty sure that's what's happened. The SLOW hardener is very slow indeed and can take 48hrs to reach a full cure (compared to around 8hrs for the FAST hardener). If the resin on your board remains flexible and weak then I'm pretty sure it simply hasn't fully cured.

You state your cure cycle as 24hrs at ambient (you don't state what your working temperature is, perhaps it's lower than the recommended 20'C) and then a post cure of 4hrs at 55'C. Although at first glance I would have expected the resin to reach full cure over this cycle I'm not entirely suprised that it hasn't. Your working temperature could be quite low meaning that after 24hrs the resin was not very well cured and then 5hrs at 55'C (which, depending on your measuring equipment might well have actually been more like 45'C mould temperature) then you could easilly be under cured.

Some time has passed since your post, has the part reached its full cure now?

--Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

False alarm! the test has been ok, yesterday proved to the board in the water and there was no problem, it worked perfectly and all those who tried it said it was an amazing board, however the next I'll do it for the infusion, but comes one last question, if the laminate is a sandwich with pVC foam, the resin may impregnate the bottom? I thought that if I have a layer below the core soric pvc there will be no problem, but I want to be sure not to spoil the material of a board! ... Thanks!

www.ktuning.es  

Hi Manu,

That's great news, I'm glad the part has cured fully now and that the results are so good.

Regarding infusing a board with an impervious core (PVC foam) if you want to co-infuse the whole thing (so the top skin and the bottom skin at the same time) then you would need to ensure that you heavily perforate the PVC foam so that the resin can get down from the top to the bottom. To do this, drill hoels through the PVC foam at about 10mm centres, making the holes about 1.5mm in size. The resin will drop down through these holes and infuse the bottom skin at the same time as the top. Never attempt to do this without the holes, the bottom will stay completely dry.

All the best, Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales