Great work. Subscribed. I hope to have the ability to make parts like that soon.
Can you post some more detailed information about the products you used to prep the plug and to prep the mold, including the gel coat or whatever you used before putting the carbon into the mold. I am not familiar with any of the products you used.
There's quite a bit that went into that mold and part to get that finish right out of the mold. I think most builders are pin hole filling and clearing the part post production. I could be wrong, I don't know a whole lot of people in the industry.
Anyway, to get from the plug to the finish part took me two and a half days working 12 hours a day. Granted, a lot of that time was spent learning and taking each step slowly, and laying up the mold. With the right tools (mainly a 1500 watt IR heat lamp) I could probably pull another part in 8 hours or so.
For the plug I used Duratec Surfacing Primer after prepping the plug and flange with bondo and evercoat glazing putty. The plug was sanded down to 150 grit and all pin holes filled. Shot the Duratec with a 2.5 HVLP @ 50 PSI. A note on Duratec and warmer climates, set a timer for 5 minutes from when you catalyze. When the timer goes off, stop spraying and pour what's left into a disposable cup with about the same surface area as your gun's cup. Start another timer and run solvent through your gun while watching the cup. This will give you a better idea of how much time you have to shoot the Duratec. Cleaning gelled Duratec out of an HVLP is no fun... Back on subject, once the Duratec cured enough to not clog up my paper (3-4hrs), I wet sanded with 400 grit to remove the orange peel, and then 1000 and polish/buffed with a random orbital buffer. I could have sanded with 1000 to start or even 2000 if I had better spraying skills. Duratec is available through US Composites among other retailers.
The other key to the mold having an excellent finish was the PVA application. I shot PVA 3 seperate times, washing it off each time and starting over before I got the finish right.
For the release system I used a semi perm release agent - Frekote 770NC and the FMS sealer. This stuff just wipes on the mold. Acetone to clean any oils or polishing compound, then wetted a blue shop towel with the FMS and wiped the mold starting from the outside. Once that flashed off in 5 minutes or so, the 770NC is applied the same way with 3 coats allowing 5-10 minutes to dry between coats. Soller Composites carries these products and sells them individually. There are several other retailers who sell frekote, but it is sold in a package of 4 cans. Soller breaks it up and sells individual cans.
For the part production, I applied an in mold coating (IMC). The product I chose was from German Advanved Composites (GAC), and is a poly urethane. This is one of the very time consuming steps. Frekote 770NC produces an extremely high slip surface, so much so that the IMC doesn't like to stick to it. In order to avoid fish eyes, the product has to be mist coated progressively and had to cure in between coats. The IMC I used has a 24 hour cure time at 77*, an hour at 140*, and a few minute at 170*, but begins to break down at 225*. This is where an IR curing lamp would have made my life easy. Instead I was trying to heat the mold up to 170 degrees using halogen work lamps and a heat gun. I was getting the mold to about 130-150 and some sections where the gun was directed were up to 185-200. Applying this product took about 4 hours total, but could have been done in probably an hour if I had a curing heat light. They are also very proud of this product and it is a little on the pricey side, but IMO worth every penny. It's up there with the imron stuff in price (it might actually be a rebranded imron polyurethane for all I know). Like I said, it was worth every penny and the guys at GAC (Juergen) were especially helpful with questions and even requested updates on this project as I complete it.
While the final coat of IMC dried I patterned out the fabric using the plug and some fabric I bought from Hobby Lobby. I used a 7.8oz 4x4 twill for the visual layer and 3 layers of 19.7oz 2x2 twill for structure. All carbon was purchased from Soller Composites.
- As a note here, the next hood I make I will lay up the visual in two pieces, and in mold air brush the seam black. It is just easier and will produce a better product. Doing this, I would need to precut some wax/parchment paper and mist it with 3M super 77 and lay it on the carbon. Then cut the carbon on the wax paper to keep the edges from fraying. The lighter carbon weaves are extremely difficult to handle in case you haven't worked with them.
The visual layer was laid down as a whole piece. I folded it down the middle length wise and draped it into the mold. I worked it into position using the rounded side of a clean bondo spreader and then slightly lifted the fabric, lightly misted super 77 on the mold, and very carefully replaced the fabric. The non-visual carbon was just relief cut and laid in with any stray tows cut away.
Bagging was pretty standard. I can go into detail, but if anyone is considering this kind of project than that would be the basics to get down first. Supplies for bagging and resin were purchased mainly through shop.fiberglasssupply.com. I think US composites is where I buy my film from because they offer 110" V Fold at an unbeatable price. Resin was 2070 Resin Research Infusion Resin. The final ratio of resin was right around 46% of the total part weight. I mixed up 70% to be on the safe side as I wasn't sure how much the line and bagging materials would eat up and how much was needed at the base of the cup.
I used the MTI hose from GAC. It's an excellent product and I believe it is worth the money. It really makes the process easy and minimizes the size of air bubbles and voids. And again, support from them was top notch.
I think that about covers it. If you have any specific questions let me know. I'm not an expert by any means, and I learn more from each failure and success than I knew to start with, but I'm happy to share what I do know and my experiences so far.
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