Probably not, but print might be a concern.
I suggest trying to obtain a sample of RM5000, and do a test on a scrap piece of polystyrene.
I can’t understand how it would print through two layers of duratec primer, and duratec highgloss VE topcoat?
Since you have experience with many of the RM resins, what is the approximate resin/glass mass ratio with the infusion tooling resin RM5000? If you had a choice to use these RM resins, which one would you choose and why?
Can I also stiffen the structure with the RM resins without the fear of mold deformation?
Thanks,
N
Print: seams might show up, and as the epoxy probably is not cured completely, it might develop a print, right through the Duratec primer and top coat. I do not say it WILL happen, but i have seen it happening.
Vf for RM5000 is low, some 10%-15% perhaps. You need very open glass to have the highly filled polyester to infuse. At this moment we are able to infuse a 180% filled polyester resin, which is quite remarkable.
Which one would I use? If heat resistance is a concern, go for RM3000, and use the recommended amount of gelcoat and skincoat layers. The rate of cure of the gelcoat and skincoat is critical to produce a 100% defect free mould. The RM2000-6000 is just for backing up that nice surface.
If hand laminating is out of the question, RM5000 or RM6000 is your option.
But if price is an issue as well, RM2000 will do. It has a HDT of 85C, which is more than enough for most projects.
Forgot about the reinforcement.
I am not a big fan of mould reinforcement. Sooner or later it can show through. If you need to, make sure the base laminate is thick enough, and is well cured. Then RM2000 or whatever can be used to add stiffeners.
I like stiffeners only on hard edges and flanges, and have the surface in between stiffened by either balsa, or not at all. I must say that I am used to deal with moulds 50 ft and even larger. For smaller moulds it might not be that critical, as weight is much lower.
Herman,
Unless the surface temperature of the plug exceeds 90degC and the foam backing shrinks considerably, I don’t see print-through as a concern since the mold is well cured (its post cured and tempered after its first cure). Also the glass-epoxy has a very high resistance epoxy (from which the plug is made).
I’ll like to avoid the use of stiffeners due to the reasons you’ve outlined, since in long organically shaped structure, one will see the deformation very easily. However, I’ve seen most similar molds supported by a steel frame, and I always question: the huge difference in coeff of thermal expansion of steel and glass will distort the mold during each heating/cooling cycle, perhaps changing the tolerance on parts. Have you seen this?
What I was thinking of doing is the following: After the gelcoat and its cure, I’ll use VE with 2-3 layers say 150gm/200gm/300gm, I’ll let them cure properly, then scruff sand them and do a RM2000, with 4x450gm CSM. Let it cure for a day or two, then do an infusion or layup with RM2000 using two 5mm LRC soric on top of the scruff sanded laminate, 4 layers of 450gm CSM and on the outside one or two layers of 450gm glass cloth. This should make a lightweight and very strong and stiff laminate. I’ll wait for a few days and then layup a stiffening structure at the back again from this same material but not touching the actual part area. The mold is 7m long and I don’t want it to deform with time.
Agree with the comments on stiffeners for large and small (boat) moulds. There seldom seems to be understanding of print through. Having beveled edges less than 45 degrees does help to minimize any print through. Touching on what Herman mentions I have produced tooling and manufactured for several high production racing dingy’s, Laser/RS sailing, the tooling for which has been cored.
Herman, thanks for the tip for RM6000 and RM5000. Its possible that I’ll be getting a small sample quantity of these in the coming week. Would you like to share your experience in a bit more detail with any or both of these? My experience with PE/VE is rather limited and I’ll appreciate any suggestions, like what to do and what not to do?
Thanks,
N
the two parts mold,the seam could be no seen ,the sharp corner could do rounding.