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Old 08-20-2009, 06:43 PM   #1 (permalink)
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cheap,dirty,(but heavy!!!) molds for fiberglass

My trailer project requires a fairing for the square-tubing axle.I've had a section of aluminum aircraft strut from an amphibious ultralight which augered into Lake Dallas during takeoff which is of perfect size and proportion but short on length.-----------I did an experiment to see if I could create a dirt simple mold from the strut,to layup enough fiberglass from it in sections to cover the axle.--------------- What I did,was cut the footprint of the strut into 3/4-inch foamboard so only half of it protruded above the surface of the foam.I built a dam of scrap wood and clamped that around with bar-clamps.---------- Aluminum tape was used to seal the gaps around the strut.The whole inside was coated with petroleum jelly as a release agent as you would with architectural plaster work.------------------- I mixed up 20-pounds of sand-mix concrete mix,poured half of it in,placed a pre-cut section of 3/8-inch steel hardware-cloth in for structural reinforcement,then placed the remainder of the mud into the setup,tapped on it to agitate,and left it to go off overnight.--------------------- Next day I de-clamped it,pulled the dams,inverted it onto a piece of foam rubber,and with little separated the "buck" from the "mold".------------- As you might expect she was a little rough,so after degreasing with Orange Go-Jo,a good rinse and a solar dry,I covered the working part of the mold with aluminum tape and with 3-coats of Meguire's #16 100% carnuba wax,buffed in between applications,she's producing pretty decent wet layup parts now,@ 45-minutes /part, and overnight cure.

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Old 10-03-2009, 04:43 PM   #2 (permalink)
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mold photographs and sequence of fiberglass layup

Apologize for late catchup,been very absorbed with the trailer project.Al Glidewell helped me load photos from the camera of the mold making and fiberglass wet layups for the square-tube axle fairing.-------------- I never know how the sequence of photos will come out when I submit them from photoshop.-------------- I'm no professional and hope the images provide some useful visual info.----------- In "school" we used very expensive tooling epoxies,special tooling plasters and hemp bird's nests to create a durable plastic-faced plaster splash,good for a few parts if carefully maintained.This mold cost maybe $3.00,for a 5-inch by 25-inch part about 1-inch deep.Some of the components are recyclable.--------------- A review of the photos show the original aluminum strut"pattern,male-mold,styling-buck" recessed into rigid foam insulation board atop a foam rubber pad,gaps taped with HVAC aluminum tape,surrounded by a clamped-on dam,coated with Vaseline,and covered with sand-mix concrete,including a hardware-cloth reinforcement embedded within the matrix.--------------- After an overnight cure,the "styling-buck,male-mold" is released,leaving the female "mold".------------ With 3 applications of carnuba wax,preferably followed with a spray coat of polyvinyl alcohol ( PVA ),the mold is ready for layups.Since I lacked the vibrator,as used in concrete countertop-making,I ended up with air voids.These could have been filled although I elected to just skin the whole face of the mold with aluminum tape and use this surface to cast against.----------------- The photos take you through an entire layup,with 2-cloth/1-mat plus 3-ounces of polyester resin+ MEK peroxide catalyst per part.------------ I made no attempt to vacuum bag,I just rolled the fabrics with the serrated roller designed for this activity and squeegied any excess resin.I let the parts cure overnight,and without PVA,I got good releases each time.---------------- Any part could be made in this way once a "master" pattern were available.Reproduction parts can be made by casting a mold directly off an existing structure,EXAMPLE: there is a Porsche 356 kit car that was developed this way.------------- Hope the info helps.I'll try and revisit the thread from time to time in case questions emerge.Happy fabricati!ng

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