I`d say cut out some small pieces of foam and glue them between the pieces. Get them as close as possible and then fill in any cracks with your glue and poly fil. If you sand it down and fill in everything enough you shouldn`t even be able to tell they didnt fit together
Hey there, I have a few questions on this if you don't mind answering them. I am planning on doing Tira's ring blade, however I am debating between whether to make it out of foam or pepakura it and then use fiberglass on it. I have a problem with pepakura as I have no idea what to put inside it to balance and give it weight so that's why I've been looking at your tutorial. I have never used insulation foam and so was wondering exactly how easy it is to work with? The tutorial makes it look simple but I was wondering if you could give me a little more information on your building process. Did you make the creases and dips in the foam around the spikes by sanding it and also did you have to put any resin on it to strengthen it and can it be painted with spray paint? Sorry if this seems like a lot of questions but I really have no idea on how to go about this. I would really appreciate it if you could help, thanks!
To be honest I am very behind on all the new products that are out there for prop making so I have no idea what pepakeura is. Sorry about that. My response is always use what materials you are comfortable with. I have little space and not many power tools so I will always prefer foamboard. It's the easiest thing to use, I used it the first time when I was 17. But back to the blade itself, I did just sand down the sides to create the bladed edges. Resin can be applied on top but it is so incredibly important to SEAL IT! A lot of materials like spray paint can eat away at the foam so it's huge to seal it. I use gesso and a couple layers of glue just to be sure. I didn't strengthen mine much and it did take a bit of a beating but nothing that couldn't be fixed with a bit of 'no more nails' which is a glue best used for foamboard. As long as you are treating it like a prop and not flinging it around and dropping it, a couple layers of glue and paint can hold it together quite well.
Also a little tip: If you get a bit rough with sanding on foamboard, chuncks can fall out. Polyfil is your best friend. It can make everything smooth and beautiful if you take the time. If you are more curios about foamboard, this FAQ an help you out a bunch. [link]
Pepakura is paper modelling that you coat in fiberglass to strengthen it and then sand and paint. It's very fiddly. Anyway, thanks for this, it has shed some more light on the problem and I'll take your advice on how to treat the material. Thanks for replying and helping me with this