Vacuum Bagging a Carbon Fiber Engine Hatch: From Mold to Finished Part

Описание: A pair of engine hatches from a 1978 Formula 255 were damaged and needed to be rebuilt from scratch—lighter, stiffer, and flatter. We designed and built a simple melamine mold for vacuum bagging our carbon fiber and balsa core part, ensuring a stiff, light weight hatch, matching the original dimensions.

DETERMINING THE REQUIREMENTS
The original engine hatch was deformed, had many chips/dings, and was incredibly heavy. Due to clearance issues, the replica hatch dimensions had to be precise for a proper fit—the hatch dimensions and thickness, flange width, height, and thickness, and the latch locations. The hatch needed clearance on the drain holes, flame arrester, and the lip on the engine opening itself.

BUILDING THE MOLD
When building a vacuum bagging mold, it's important build an air tight mold. This was created using WEST SYSTEM Six10 Epoxy and melamine. Built into the mold was a 3° draft to make it easy for the part to be removed. All surfaces were waxed before introducing epoxy.

CARBOND FIBER LAMINATION/VACUUM BAGGING
In the lay up was a carbon/balsa/carbon sandwich and vacuum-bag it for proper compaction and resin control. Technical Advisor Terry covers how to lay clean fillets, surface-coat tricks to prevent fisheyes and print-through, proper carbon wet out techniques, tinting epoxy for more even coloration, proper core waterproofing tips, and how to build a leak-free bag setup.

RESULTS
The finished product is a stiff, light, carbon fiber engine hatch that sits flush with the deck and doesn't have any of the imperfections of the original hatches.

WEST SYSTEM PRODUCTS USED
105 Epoxy Resin - https://www.westsystem.com/products/1...
206 Slow Hardener (consider 209 Extra Slow Hardener in warmer shops or for more working time) - https://www.westsystem.com/products/2...
404 High-Density Filler - https://www.westsystem.com/products/4...
406 Colloidal Silica Filler - https://www.westsystem.com/products/4...
501 White Pigment (≤3% by volume) - https://www.westsystem.com/products/5...
Six10 Thickened Epoxy Adhesive (panel/frame bonding & fillets) - https://www.westsystem.com/products/s...


VACUUM BAGGING MATERIALS
Release fabric (peel ply), perforated film, breather, vacuum bag film, sealant tape, gauge, pump (~12 inHg).


MOLD & TOOLS
Melamine board, beveled draft strips (≈3°), router with flush-trim bit, squeegees, combination square, fondant ball tool, PPE (gloves, eyewear, respirator), dust control.


PRO TIPS FROM THE SHOP
● Melamine makes for a good mold surface
● Round corners so fabrics roll without bridging
● Use witness marks to speed placement during work with wet epoxy
● Carbon doesn’t “turn clear” like glass—use bright, raking light and pressure with thumb to confirm wet-out
● Seal kerfs in balsa core to limit moisture spread
● Tape off the bag-seal flange before mixing epoxy. Sealant wont stick to wet surfaces.
● Remove blush from cured surfaces with water and a scrub pad
● Drill hardware holes from both sides to avoid tear-out;
● Seal exposed core/wood with epoxy.


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CHAPTERS
00:00 Intro
00:24 Assessing the Repair
03:34 Creating the Mold Frame
17:06 Waxing the Mold
18:02 Applying Thickened Epoxy
22:22 Removing the Amine Blush
24:18 Taping off the Edge
24:56 Dry Fitting the Carbon and Balsa Core
27:14 Fillets for Lamination
28:15 The Layup
38:16 Vacuum Bag Materials
41:05 How to Pleat
43:47 Attaching the Vacuum
45:46 Debagging Process
48:08 Routing the Edge
49:49 Installing the Hardware
51:43 Conclusion

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