The SC Roto isn't really flexible per say. The shore hardness rating on it is a bit less than regular SC 300. They told me that it's a little "softer" (not much) to allow for "some" flex in the finished casting depending on it's cast thickness. If it's a thinner casting like 1/4 inch thick, or 1/8 th inch thick, it will flex a little farther than a casting of the same done in SC 300 before it ultimately "snaps". So the simple answer is, it is rigid, and strong enough for a helmet
I have traditionally done my helmets in FG. But I have to say, given that I've been at a dead stand still on those because of weather, and the ill effects it has on one's health ...
I might as well publicly say right here and now since we're "on topic" ... FG is just archaic. It's gone up in price, and well, it just makes me sick anymore. And it takes 10 times longer to set and cure. I'm about done with it
It has it's place, sure. And there are some things you just have to do in FG. But all in all, technology in plastics and polymers, or casting materials in general have advanced so far, that there really isn't a need for us "old time fiberglass lay-up guys" to continue killing their brain cells on styrene fumes (polyester resin)
So I've officially decided to offer things like helmets in a different medium. Again though, FG has it's place, like on a more complex piece like a DV helmet. But in general, I've found a casting material that is rigid, and virtually unbreakable that would suit this area perfectly. It's cheaper than the FG process when you add it up dollar for dollar including time. I'm not going to blow smoke about what it is just yet, until I know for sure. In a case like this, it's almost a wee bit of a trade secret, because once the trend is started, there will surely be others to follow suit, so I hope you understand. I just thought this might be a good opportunity to "let the cat out of the bag" that FG and me ... are officially getting a divorce, and I will have "visiting rights" when it is absolutely neccessary
The expanding foams - I think the Sgt. fang helmets are actually done in 8 lb. And there is no such thing as shore hardness with expanding flexible urethanes. That rating is essentially how many times it will expand over it's poured in thickness during the curing process. And it's cellular structure. The simple of it is - the fewer times it expands, the smaller the cells are (air pockets), the more rigid it is. The more it expands, the larger the cells are, and the cells are what create the "flex" in the structure when cure - on a molecular level. The more cells, the more flex .. until you reach "nerf"
Hope that makes some sense
The rebound 25 - I actually started THAT trend too
If that's what you're going to use, you won't need the thixotropic. Or at least, I wouldn't recommend it. It's pretty fast setting, and is designed for brush on vertical application. I've actually had to use their silicone "thinner" at times. Great stuff. Just keep in mind, you only need about 4-6 painted on layers with that stuff. It's thick, but it you put it on too thick, it excess will still ultimately slide off. Even with a thickener. It's silicone, it slippery
Basically, use only what you need, per layer and you'll be just fine.
Tutorials? I've had the best intentions on that for years. The problem is simply - TIME. It just takes so long to make a good tutorial when it comes to something complex in nature like this
FP
Thanks for all of the info.
So let me try to sum this up, and get the 'difinitive suggestions'.
Smoothcast 300 is great, but its an 'ultra low' viscosity, so its not going to be doing much each coat.
Smoothcast roto, is also goo, but a bit thicker, and supposedly 'self skinning' and its flexible. Too flexible for a helmet in the heat?
The 'foams' are in weights of 3-15 lb per cubic foot i believe. Meaning that the light 3 lb, is like post hole filler/sealant foam. And the 15 lb is a rock, and much denser. Is the 10-15 lb smoothon foam what is similar to the sgt fang?
As for thixotropics, I dont see any on the smoothon site. Im thinking Im going to use rebound 25 as evan suggested months ago to me, as my mold material, similar to the way FP did his helmet mold (though not nearly as well done) and cast it in smoothon 300, roto, or foam.
I dont mind the rigid foams, as long as they allow for a nice paint coat.
What are the FP helms done in? Gelcoat with fiberglass backing?
Ive painted on gelcoat in college, but never tried painting it. Can you use a brush to get a paint coat with gelcoat?
You know, we have all these masters of mold making around here, id LOVE to see a thorough tutorial on this. Because some of us work on such a tight budget that id hate to throw money into the wind without any gratification
Thanks again in advance.