Laying up in polyurethane resin - Any tips?

[Guest]

Hi,

I've recently learned, via the Disneysub boards, that the Custom replicas Nautilus is laid up using polyurethane resin and cloth, as opposed to using polyester or epoxy resins.

The advantage is very low shrinkage, especially suitable for laying up into slicone moulds, plus a very tough hull that is resilient to chipping.

Has anyone got any experience of this technique, and if so, care to pass on some of their wisdom?

Andy

[thordesign]

Andy,

Yes, we have tried poly

Andy,

Yes, we have tried poly resins. They work really well, but you have to have some very expensive equipment to really do it right for large models(injection or spray). Trying to do it in your basement with a brush is NOT a good idea(fumes are absolutely awful). We found it to be an effort in futility. Composite tooling does not last long with poly resins, so alternative tooling mediums are required such as silicone, which brings along its own unique set of problems. Number one being REALLY expensive for anything but very small models. Silicone tooling does not last long with poly resins, so tooling replacement is a major factor. If you make thin silicone slip molds, the rtv distorts after a couple of pulls so you loose integrity and model fit.

Poly resins have low shrinkage, but are not very thermally stable. If you get it hot in the sun for long, it will warp like crazy.

[Guest]

I've seen epoxy hulls warp

I've seen epoxy hulls warp in the sun though.

Is polyurethane worse than epoxy in this respect?

Andy

[thordesign]

Andy,

There may be some new

Andy,

There may be some new poly resins that I am not aware of. We tried them in 2003. From my experience, yes, the heat warpage is much worst than epoxy. You can post heat treat an epoxy hull to address the heat movement issues. You cannot do that with poly U resin.

[Guest]

I know you can post

I know you can post cure polyurethane resin to make it stronger.

Perhaps that helps prevent warpage too.

I'm not sure.

I've only ever worked with polyester resins, and find them very satisfactory, although I find they're too brittle for casting anything pointy and/or thin cross section.

I liked the idea of casting in polyurethane, because I considered rotocasting the hull, in the same fashion as making chocolate bunnies!!

Andy



Edited By Sub culture on 1123617771

[Guest]

I've had a look at

I've had a look at the Smooth-on range.

One of the resins 1508 is specified as stable upto 65 degees C, and 95 degrees C if post cured.

Andy



Edited By Sub culture on 1123679724

[bud]

Great, I love chocolate bunnies.

Great, I love chocolate bunnies. (lol)
Bud