Stingray Build

[RCnut]

Yeah, had to make a parting mold-board as I was dealing with a full-up hull casting. Great minds think alike. You're already deep into the rubber end of things. Wow. I better get hot on that PJ valve I bragged about above ...

David

Yep, lol. Well if all goes to plan and my fibreglass resing gets here tommorow I can see me doing a pull sooner than the weekend. Phew!

[RCnut]

Well as it turns out my fibreglass was with my good neighbour so I'm in business lol. Rubbers all on and just letting it go off and do the jackets tommorrow morning, Good thing I'm on holiday.

[Subculture]

Do you use Epoxy or Polyester resin?

[RCnut]

Polyester resin mix with some polyester filler to give it body, then Fibreglass matting to give strength, I prefer this over Gel coat as it weathers the knocks better than Gelcoat and dosnt crack a few years on. Just my own opinion you understand.

[Subculture]

I haven't heard of that technique before. It's not generally recommended to use gelcoat in rubber tools anyway. I've not seen a reason given but I would guess that shrinkage of the resin as it cures results in the resin moving away from the rubber tool, and as the resin is air inhibited it wouldn't fully cure. So they tend to recommend mixing a thixo additive e.g colloidal silica with normal lay-up resin and using that instead.

[RCnut]

Ahh well, Your knowledge on this is way over and above my own. I did try Gelcoat in a rubber mould a few years back and it came out very tacky so never did that one again. lol.

[He Who Shall Not Be Named]

I've done a lot of lay-up work and I too shy away from commercial gel-coat blends. My first layer in a lay-up is catalyzed resin, neat. I keep it from doing the fish-eye trick by making my last layer of mold release PVC, which has the texture to prevent such pooling of the resin as it cures hard. I then thicken up the next layer of resin a bit, to radius the hard-edges in the cavity, and eventually graduate with light weight, then heavier layers of glass cloth.

However, I'll tint the first layer of resin so I can see things better. Look over the 212 threads by Chris and Manfred and you'll see the blue tint I put into those GRP hulls.

David

[Subculture]

Ahh well, Your knowledge on this is way over and above my own. I did try Gelcoat in a rubber mould a few years back and it came out very tacky so never did that one again. lol.

No not at all- always done hard shell tools up until now for hulls, but have a master to mould in rubber, but I am going to lay that up in epoxy resin not polyester. Side steps the issue altogether, plus you get a very strong cast, and the pot life is longer.

[RCnut]

Whilst waiting for the rubber to go off I thought I'd do a cast of the Ratemaster and lets face it the whole model depends on this being nice and clear. So it is with great joy that I can say its come out dam well, no stickiness and virtually no shrinkage.

[Subculture]

Looks great. What clear casting resin did you use, a polyurethane or Polyester base?

[RCnut]

Polyester, and dispite warnings of doom and not ever going off and such I poured it last night and demoulded it this morning. Quite chuffed (Happy) really.

[Subculture]

Only polyester gelcoat resin that doesn't go off in rubber tools. Is it the bonda brand you've used?

[RCnut]

Nope, its by Polycraft, (Polylite) Got me a tad worried at first, Was green in colour then went clear. lol.

[Subculture]

I looked that up, and saw it's acrylic modified, which sounds good. I've used acrylic modified glues and they're incredibly tough. Do you know if you can you polish this stuff if it gets scratched?

[RCnut]

No Idea yet, I will have a go and see what I can do to it, but your right it does seem to be really tough.