Maximum cure on new work?

General Composites Discussions Composites Talk
#1

I’ll be starting on the next practice piece tomorrow or Tuesday, but this time the objective will be to turn out a working mold of the scoop on this hood, for some other projects I have in the works. This time, however, I’ll be adding multiple layers over a period of days… then leaving for a trip out west for a couple of weeks. My question is this:

If a new mold is built slowly over several days and left to completely “rest” and cure on the pattern over a period of several weeks, assuming it remains undisturbed and securely seated to the plug, does this significantly counteract the shrinkage related issues that PER’s are known for, as it relates to slight distortions on the finished surface? Would periodic heat cycles (after laminating is completed) through this process aid in stress relieving and further stabilizing the mold before popping it from the plug?

I know this may sound like a “simple” question to many of you, and maybe I SHOULD know the answer to this already, but I just wondered how many “quality” and “finish” related issues that people seem to raise concerning PER’s are actually more closely attributable to rushed work and insufficient curing, due to time constraints before demolding, than to the material itself?

Just curious…

#2

If dimensions of finished parts from your mould is very important, then make mould using epoxy resin system and powder bound CSM. This will result in a much more accurate mould, but you would have to use a slightly different procedure after applying gel-coat layer.

#3

I already have several gallons of some different epoxies and hardeners on hand, and I’ve tried a few things with them already with mixed results. Then I decided maybe it would be best to get my hands wet again with the PER systems and brush the cobwebs off of some rusty skillsets using less expensive materials, first, before I move on.
I’ve worked with these materials off and on for over thirty years (going back to early high-school). I was the only kid in my H.S. “Industrial Arts” class (and probably in the history of my old school, for that matter) that designed and built a balsa/lite-ply/'glass hulled, gas-powered ducted fan propelled, model hydroplane w/ an epoxy/'glass molded cowling for my wood-working project (got an “A” :smiley: )! LOL!! Then as I got older and tried to pursue things further, the challenges of daily life and raising a family would take precedent, so it was always “start-and-stop”. Always had fun and enjoyed myself making various things, but probably never developed the consistent skills to the degree that I could (or SHOULD) have. So I’m not quite back to “ground zero”… but re-learning quite a bit. I’m also discovering, from searching this board and learning from everyone here, that some of the things that I THOUGHT I knew back when aren’t necessarily so. Back “in-the-day”, my knowledge base consisted of whatever outdated books I could get from the local libraries, or over the phone/counter from the original owners/operators of “Fiberglast Developments” (about 15 minutes away). Hey… I was a kid! :rolleyes: But over the last year or so, since I’ve discovered this forum, I’m given cause to re-think my positions on more than a few things.
Before I move on to more high-end materials/methods (and more $$$), I think it would be prudent to develop a better hands-on, working knowledge of the basics, again. I KNOW that epoxy-based tooling and composites are superior in many respects, compared to PER/VER systems. But my original question remains:

Taking time constraints out of the equation… if working more slowly and deliberately, can (nearly) distortionless results be had with PER isopthalic tooling resins?

Kinda long, I know, just thought you should know “where I’m coming from”, and “why”. Thanks.

#4

No problems and actually you are correct on leaving the new (fully molded) mold on the plug over a long time before demolding will help and should not prove any problems demolding at the later date IF the mold releasing was done properly first.

The reason you got alligatoring the last time was that the gel coat was too thin. Try after spraying the gel coat, get a brush and wipe out the cup and apply that to those hard to spray areas.

When using a brush, try shaking the wet gel coated plug to level out the gel coat in those areas.

#5

Well, we’ll see what happens. My curiosity got the best of me as I was setting up this morning and I switched out the #5 tip (that I used the last time) in the cup-gun for the original #6 because, even thinned w/ Duratec, it was more like fogging on mist coats, even from 14"-16". Very slow and tough to get coverage in places, like inside the scoop where it alligatored on me.
Anyway, thinned the gelcoat (again) with Duratec Hi-Gloss Additive @ 15% and catalyzed @ >1.5% w/ MEKP to keep the heat out of it and keep it from “B” staging so quickly. So I stepped up to the plug, took a breath and pulled the trigger… whoosh! It came out of there like nobody’s business! Fortunately I started my pass off to the side on the masking paper along the flange in back. Gave me a moment to re-gauge my distance and speed before I moved out over the hood. Backed it off to around 18". Made the first pass (orange) over everything and then let it sit for a few minutes before starting my second pass. Checked it w/ the mil-gauge and it was somewhere between 10-15 mils on the first pass. Nuts! Didn’t quite get through the second pass before the first cup (24 ounces) was gone. Double-nuts!! So I catalyzed the second cup (black… pre-mixed and waiting) and finished the second pass… waited a few minutes then fogged a little more black on the whole thing so it’s uniform. So, to make a long story short, I used just over a quart on 12 sq/ft and the gelcoat is back up to, or just a tick over), 30 mils again. I just couldn’t leave well enough alone… :rolleyes:
On the “up” side… it took around an hour to get close to a nice “B” stage. The first couple times I catalyzed at US Composites’ 2% guideline and it was kicking to the squeak stage in just over 30 minutes! It kind of had me wondering about the batch of gelcoat, itself, or the MEKP solution that was supplied with it. But it’s always easier to point a finger than look in the mirror at my own dumbass-self. So I guess we’ll see what happens.
I have a cup of resin/Cabosil/milled fiber saturating right now. I’ll give the whole thing another 30-60 minutes to further cure, fill the corners and then start laying veil and mat. As long as it doesn’t lift, I’m going to just GO for it this time, add more layers over the next couple of days, let it completely cure out and then pop it off in a couple of weeks when we get back from LA (Anaheim) and other points south-west.

Here goes nothin’!

#6

Is there a convention in Anaheim or you just going to see Mickey?:rolleyes:

#7

Neither… My wife is driving our 17 year old to Utah (as I write this) for a 6-7 week stay at a wilderness retreat, then driving on to LA, where my daughter and I will meet her and stay with some close friends (in Anaheim and Belleflower) for a few days before leaving to come back. We usually go out in April for the Knotts’ Fabulous Fords event, and hit Irwindale for Test-n-Tune on Thursday nights, Huntington Beach for the “Donut Derelicts” cruise-in on Saturday morning, maybe Fuddruckers in Pasedena for their cruise-in… then whatever the heck else we can dream up for a bunch of “40-something” reprobates that are “in” to vintage Fords… and just old cars in general. Truly great people, close friends… great times!
The one thing that, oddly enough, caught my attention the first time we went out was seeing the concertina wire wrapped around some of the overhead, highway road signs! I asked my buddy what that was all about. Were they afraid somebody would steal them or sit up there and throw stuff down into traffic? We’re driving through LA… beautuiful blue skies, about 9A on a Friday… Zeppelins’ “Cashmere” thumpin’ as we cruise along in a slammed ‘72 Torino wagon w/ 18" Budniks… my buddy just smiled and shook his head and yells over the music, "Naw… it’s to keep the graffiti artists from taggin’ the signs! Welcome to LA…!". Laughed my ass off… still do when I think about it.

#8

Well, the Fab Ford show is over and I was planning to take my Irwindale Speedway Mini stock (#54…where are you) Mercury Capri race car there but the family that wanted to buy it had it and now backing out…:rolleyes:.

There is always many cool car things to do around here…and I was planning to post some cool car events coming up like the end of the Great race at Disneyland too!

I’m 1 year older than Disneyland and I still can remember it as a little merry go round and a few other rides…dates me!:eek:

#9

FWIW… everything went down without a hitch yesterday and I tried to keep it to the dry side of things on the wet-out. Checked the lay-up this morning and all appears well. Absolutely no lifting anywhere, nice and firm.
Today I’ll be doing a little additional filling on a “step” at the flange transition in back and then hit it with a layer of 1.5 ounce mat, followed by some 12 ounce bi-axial and 12 ounce double-bias. Tomorrow I’ll add some mat, 17 ounce bi-axial and 17 ounce double-bias… maybe top it off with some veil… then let it all sit and “cook” for a couple of weeks.

#10

What’s powder bound CSM?

#11

What’s powder bound CSM?

#12

Did a “Google” on it. Apparently it’s an alternative to emulsion-bound mat when working with epoxy. It appears to be commonly available in the EU and Australia. By the looks of things, it’s likely available here in the US, as well, just not sure how readily or in what quantities. Trust me, if I had stumbled across it, I would have bought a small quantity just to play with it.

Here’s one site that lists it, several line items from the top:

http://www.cfsnet.co.uk/acatalog/CFS_Catalogue__FIBREGLASS_MAT___FABRICS_10.html

#13

OleDutchD, when you are in Anaheim and if it is a Friday afternoon / evening, try cruising over to Garden Grove main street car cruise!:cool: Near Euclid and Garden Grove Blvd. area.

PM me if you are going to it and maybe we can get together there as it is a short bike ride for me from my home (my back door neighbor is Fast Eddie and you might have read about his creations in Hot Rod and many other mags too)…or maybe I’ll drive my Bug body go kart!:eek:

#14

FWIW… just got back from out west this afternoon. After unpacking everything, I walked out to the shop and popped the mold-in-question off the pattern. Nice clean release and it looks as if it will be a totally useable piece. Very satisfied with the results! :smiley: Next step will be to get it ready to lay-up some trial parts and then try my hand at infusion.

Also, before I set up to build the full hood mold, I’ll need to buy more resin as I’m almost down to my last five gallons. Is there a genuine, quantifiable advantage to using VER as opposed to PER-based tooling resin to build molds? Just wondered if the claimed benefits/advantages are accurate.

Thanks.