3 – The Basics of Fiberglass – Plug Construction and Advanced Moldmaking

hi I’m Marilyn Klein president and owner of fiberglass developments hi I’m Scott Campbell Sales and Operations Manager at fiberglass developments in the spring of 1994 I was contacted by the premix corporation to assist the University of Akron in building an all composites supermileage race car although we typically are not fabricators I agreed to provide a fabrication leader in exchange for being able to videotape the entire process of building the car premix Goodyear and fiberglass developments all participated in financial support of the car and are proud to have been part of this unique educational project the essence of the supermileage competition is erase among vehicles all obtaining in excess of 1000 miles per gallon of fuel our goal was to assist the students and faculty in building a light and efficient composite car to compete in this race I was the fabrication leader and guided a team of engineering students through the process of design construction and fabrication of their composite car the process of building the plug through completing the finished shell took about six months and is edited into two videos this is the first video and here we demonstrate the steps of building a large plug and the advanced mold making techniques required for full-scale applications the second video in this series demonstrates vacuum bagging techniques and the sandwich core construction used to build the graphite honeycomb shell the University of Akron College of polymer science requested that we assist the college of mechanical engineering in building the composite shell the mechanical engineering students would then be responsible for adding the engine steering and all of the other components of the car we thank the University of Akron visual services department for shooting all of the in process footage that you see in these videos the car that we built was intended to be an evolution of an existing metal frame car our goal was to eliminate the metal frame and create a vehicle which was lightweight yet strong enough without the frame to all the loads of the car this included all the systems as well as the driver as I began the project I knew in my mind’s eye what the finished car would look like I knew the shape of the new car would have to be rounder and more uniform on the outside surface than the old car it would also have to be slightly taller and wider because we needed to use 27 inch bicycle wheels instead of the 20 inch wheels used previously the cockpit needed three feet of legroom for the driver as well as a windscreen which provided 180 degrees of vision from right to left as a result the shell of the car would have this basic shape we needed to create a model which had the exact shape of the finished car this model is called the plug from the plug we will pull two female moulds these moulds would then be used to make a top and bottom shell for the car as we begin construction of the plug you’ll want to keep in mind that we are following the same outline as demonstrated in our video the seven steps of molding fiberglass if you are new to molding and need a more concise explanation of the process you might wish to review that video this video and his sister do assume that the viewer is at an advanced level in hand laminating composites the first step of mold making is developing the plug in many cases such as this one there is no existing shape available to use as the plug and it will have to be created from scratch before we begin construction however there are three rules to remember in all plug construction first the plug must be geometrically identical to your desired finished part second the surface of your plug must be absolutely perfect there can be no flaws pin holes or dull spots as these will transfer directly to your mold and then to your parts third and finally the plug form needs to be strong enough to support the molding materials before they cure and not distort during construction remember the key to successful molding is to create a perfect plug it doesn’t matter what type of materials are used or how inexpensively the plug is made but it must meet these three criteria a plug as large as the one demonstrated in this video might be archived so that if additional molds were necessary the master plug would always be available if you know that the plug will be saved for future use build an even sturdier so we’ll survive multiple vigorous mold releases when a plug needs to be created entirely from scratch the first step is to lay out your design

design engineering with composites is beyond the scope of this video but I will outline some helpful hints based on my experience throughout the process the car had to meet the basic parameter stated above in the introduction provisions were also made for steering and braking systems the driveline axles motor mounts and safety systems when construction began many of these accessory systems had not yet been engineered so I had to design a platform that left the students as many options as possible these types of requirements affect the size and shape of the plug but there are additional considerations as well you must anticipate your molding process in this case we need the car to have a smooth outer shape while using sandwich cores inside to add stiffness to achieve this we had to construct to open female molds ultimately the molds need to be released from this plug so you must plan to divide the plug at a point which does not create any negative angles a negative angle occurs when an area below your mold seam is wider than the area the parting line you have to anticipate this when you design your plug and make sure that no negative angles exist do not count on the molds flexing enough to release around a negative angle they will not if negative angles are unavoidable the mold will have to be constructed in several more sections the second thing to anticipate is the ultimate layup of parts trapped air in the mold or in the parts results from either inadequate saturation or resin and reinforcement pulling away from surfaces that they can barely reach you want to avoid right angles and tight corners in your design where air pockets can form as you can see from this later shot of the rear of the plug I taper the curves as much as possible to avoid this finally the vacuum bagging lamination method used to construct the final parts also meant that a wider than average parting flange be incorporated into the molds as the point of attachment for the vacuum bag this required only minor modification to the existing part of the mole after you have completed your design you’re ready to start building the plug the second step of plug making is to build a sturdy frame the size of the Akron vehicle made carving the plug for one solid block of material impractical so a framework was constructed to provide the basic three-dimensional shape full-scale cross sectional views were cut out of drafting paper and glued to plywood sheets these cross sections were the bulkheads which made up the exact outer surface of the plug to orient and support them properly slots were cut in both the bulkheads and in longer framing boards this allowed the bulkheads to rest in the frame precisely located along the axis of the car the plywood is the first outline of the plug earlier centered holes were drilled 20 inches from the base of each piece of plywood these holes accept a large dowel rod which supports the tops of the bulkheads and helps them to remain in position after gluing the plywood and the frame together the rod was inserted notice that the framework is all internal and will not affect the surface of the plug you must make sure everything is straight use a t-square to verify the positions before continuing when the glue dries the bulkheads will be securely fixed in place the third step of plug construction is to make the surface for the frame we had decided to make the plug solid just surfacing the bulkheads wasn’t practical filling the plug with expanding polyurethane foam is ideal once cured it is easily cut and carved it is relatively inexpensive and will expand to fill even oddly shaped cavities to save on foam we didn’t fill the entire plug just the surface perimeter it was easy to tape newspaper to the bottom of the frame creating loaf pan type cavities when the frame was flipped over pouring into these square cavities was straightforward so we began there you’d have to seal all the edges with tape to prevent the phone from draining out the foam is a liquid which you pour into the cavity it will expand to 30 times its volume in the liquid state if the size of the cavity is known divide that by 30 to determine the volume of foam to mix more often the sizes unknown support just enough to cover the bottom uniformly until you gain experience with how the foam expands we continued mixing and pouring until the bottom of the frame was filled as you can see some sections were filled in multiple pours while others rose properly the first time all of them will be trimmed later to a uniform height after the bottom was filled we tipped the frame on its side and taped in newspaper like we did on the bottom however this merely created broad and shallow cavities which followed the outer contour of the car we soon found that these types of cavities do not contain the foam well enough so we did not construct anymore we were able to finish the side this way by making multiple pours but it was neither quick nor clean we discovered a better way we fill the inside with newspaper and stuff to create an inner pocket and all we’re

doing now is coming along and loosely applying newspaper loose enough so that it can expand and have the foam come out beyond it so we can cut it off later and shape it the opposite side and the rest of the frame were filled from above using this technique at this point the surface is quite rough you want to make sure that you have overfilled and have enough to trim adding or filling starts becoming more difficult from this point forward the newspaper on the outside will simply be shaved off with the excess foam now you will begin the fourth step of building your plug which is carving it to the correct shape saws and knives easily cut the foam but it cannot be hot-wired you want to trim away the excess and sand the surface smooth remember that the plywood bulkheads provide the actual finished dimensions so do not go to the foam deeper than the plywood trim as much as possible with the saws before trying to sand Scott used an electric belt sander to quickly trim the excess foil the newspaper which the SOGs did not remove from the frame the belt sander was fast but in some areas he removed too much material try to keep your cutting surface on the bulkhead or you cannot go to the foam a straight 2×4 about four feet long with sandpaper glued to the surface makes a great sanding block for the larger and flatter sections also polyurethane foam is easily sanded using another block of itself this works particularly well in areas of detail before long you can see that the plug is taking shape nicely most of the newspaper has been removed and the foam has closed the gaps between the bulkheads two days later the entire plug has been filled in and shaped even to the casual observer it is beginning to resemble the planned shape in some areas the foam was shaved too low and in others air pockets were trapped these can be filled with the standard auto body filler or you can mix phenolic micro balloons with your molding resin to create a spreadable sandable paste filler we had body filler on hand so it was used on the areas we needed to reconstruct the surface does not have to be perfect but it should not be higher than the surrounding foam once all the high spots on the phone were removed the plug was skinned this is the fifth step of building the plug the surface has to be completely non-porous and pretty resilient typically it is fiberglass this matte layer serves two functions first it protects the foam from accidental crushing during handling second and more importantly it provides a solid base for all other surfacing compounds to be applied later thoroughly saturate pieces of fiberglass mat then lay them in place begin with torn chunks which approximate the space between the bulkheads you are going to fill it may be helpful to paint some resin over the foam before applying it in order to fill many of the tiny holes the foam holds quite a bit of air because the cells were cut open during the shaping process try to work out the larger air pockets by stippling with a brush or wiping with your gloved fingers a groove saturation roller also helps to remove the air mixed batches of resin in quantities which can be applied before the cure sets in begin with small pots until you become familiar with the cure cycle I continue to work from batch to batch and I’m not concerned with how much of the fiberglass has been cured as I go along I make sure that each piece is laid properly without trapping air that way if the resin does set up I don’t worry about poor adhesion problems one even coat of fiberglass is all that is needed to coat the plug for protection if necessary extra layers may be added to fill minor low spots work consistently to cover all exposed foam the body filler can be covered just like the foam I worked alternately between filling shaping and skinning the foam until the entire framework was uniform when the entire framework has been skinned it needed to be lightly sanded to remove any stray fibers and promote good adhesion for other surfacing compounds this is also a good time to look for air pockets which need to be ground out and repaired the portions of mat which were ground out over the air pockets are being replaced other areas are being filled because too much foam was removed during the trimming stage notice that the mat saturates quicker when placed on a non-porous surface than it did over the phone it is possible to work faster now but still watch out for air bubbles I mentioned it earlier but this is a demonstration of a group saturation roller at work it has no equal for quickly and thoroughly removing air from a chopped mat surface look carefully for areas where the fiberglass did not stick to the foam these areas will feel spongy when pressed and must be cut away it is now time to proceed to the sixth step of

plug construction the sixth step of plug making is to complete the final shaping in the areas where the fiberglass skin has correctly assumed the shape of the vehicle it can simply be sanded with 80 grit dry sandpaper to prepare it for priming in our case the plug needed quite a bit of final shaping to achieve the desired contours the bottom of the plug was closest to being correct so we started there we added material to the bottom to level it and to the sides the smoother transition with the bottom use some type of sight gauge to determine where the material needs to be added or removed here I use a straightedge to look for low spots to circumstances existed at this stage which caused us to adjust the normal sequence of operations during the final plug shaping and mold construction the first circumstance was the current shape of the plug although the framework had been designed with no negative angles it had very little taper or draft to its sides it was decided that the lower carbon body shell would be extremely rigid and in its present form difficult to release from the mould consequently the mould sides needed a greater taper the ideal place to anticipate this would have been during the design of the plug however this is the final stage to make any changes and it is better to correct it now than to have the part stick in the mould or be damaged trying to force its release following this line I built a taper to a height of 3/8 of an inch over a 14 inch span per side using glass reinforced body filler however it had to be blended evenly from the bottom of the plug to the parting line and added another week to the project the desired result was achieved though and the material added 1.5 degrees of draft to each side of the plug the second circumstance which facted the final shaping of the plug was the timetable of the project the sooner the students could receive the structural or bottom portion of the vehicle the earlier they could begin final assembly and testing of the engine and other critical systems in an attempt to compress the schedule and produce the lower shell earlier only the bottom of the plug was fully shaped and surfaced before the lower mould was made we then came back and surfaced the top of the plug however to teach these mould making techniques in the proper sequence we will discuss finishing the plug in its entirety when that is complete we will proceed to mold construction as stated earlier the bottom of the plug was finished first we pick up now forming the top of the plug to speed the shaping I switched to a quick setting drywall compound to rapidly blend the top into the bottom this material dries in 20 minutes without cracking and sands easily I’m using a fairly wide applicator where the sides are flat enough to allow it this saves on sanding later my shaping tool consists simply of two drywall sanding blocks of different lengths and many drywall sanding screens since the drywall compound is softer than the body filler I used on the lower portion of the plug I am able to sand right next to the finished lower surface without changing its shape this transition area is the parting plane which divides the two molds and it cannot be altered I am now sanding one of the last layers of drywall compound I use a crosshatch pattern a longer stroke and a longer sanding block to make sure the flatter areas stay true the switch to drywall compound probably saved the week’s worth of work grinding on the body filler I use the flexible drafting tool to check and recheck my contours from side to side cardboard templates could also be used but I found this to be quick and accurate enough check every 6 to 12 inches depending on the length of the sanding block being used I finished covering the plug with regular drywall compound to get the smooth finish and sanded it with 180 grit dry sandpaper at this point I blew the remaining dust off the car before checking all the measurements again I knew that the shape that had been developed would be the final design of the vehicle after the plug achieves the proper shape it must be covered with the material which can be sanded and polished to a high-gloss finish this is the final step of building the plug the drywall compound was sealed with the latex primer available at most hardware stores this was sprayed on then lightly sanded with 240 grit dry sandpaper the product I’m spraying now is an automotive epoxy primer which I use to seal the entire plug surface this epoxy sprays on easily is extremely durable and can be polished to a mirror finish I first applied a light tack coat and let it dry then we filled any visible pinholes with a very light spackling compound we got this at the hardware store as well it is easy to apply with your fingers and the excess is removed with the palm of your hand next I sprayed on a medium coat of epoxy primer to cover the spackling compound this only sat long enough to tack up I applied a final coat of epoxy primer to seal everything the primer must be thick enough that later sanding operations

will not cut through it the plug set for over 24 hours to be sure the epoxy had time to fully cure before sanding would begin the sealed plug needs only sanding polishing and waxing to be ready for mold construction while the surface may appear fine a closer inspection usually reveals a slight orange peel texture this texture along with any other minor flaws must be sanded off the plug or it will be transferred to the mold surface begin using 240 grit wet sandpaper and a wet or dry sanding pad clean the paper frequently with water to remove dust and to lubricate the plug surface rinse the entire surface with clean water dry and inspect do not proceed to the next grade of paper until all the orange peel texture has been removed when only 240 grit scratches remain move on to the 320 wet paper to remove them use consecutively finer grades of paper until the scratches are very fine we stopped after using six hundred grit paper and wash the plug again the plug now has uniform fine scratches over the whole surface and is ready for buffing next we spread machine glaze over it with clean tarry wipes we hand buff the surface because a machine polisher was not available I personally recommend renting a machine polisher not only does it make the job easier it polishes to a higher luster as well number eleven parting wax was then applied to the plug allowed the haze and buffed off a total of six coats of wax were applied allowing the wax to harden for an hour between every two coats the resulting waxed plug is now ready for the upper mold to be constructed this shape is exactly what the final vehicle will look like it has a very high quality surface finish free of scratches and is bonded securely to the supporting layers below the plug is now complete it is identical to the desired shape of the finished car in every detail we are now ready to identify the parting plane and build the separation flange it is this line which will separate the top from the bottom mold half as we explained when finishing the plug we had to construct the bottom mold as soon as the bottom of the plug was finished as a result this step of constructing the parting flange was performed when the plug was only partially finished due to the size and the taper toward the nose of the vehicle a full-size parting board was not constructed as it was in our molding fiberglass video it was still necessary to create a flange which would follow the parting line and separate the mold halves 14 inches from the bottom of the plug was a crest or waist which was the widest portion of the model this was the parting plane which would divide the plug into the upper and lower mold halves please note that the plug is resting upside down awaiting molding also note the wax Formica board screwed to the back forming the flange at the rear of the mold using modeling clay we constructed a three inch deep shelf around the entire perimeter of the plug I used the razor blade to smooth the clay making sure that I didn’t hit the surface of the plug the shop was supported with more clay and cantilever triangle supports made of sheet metal the Shelf needed the triangles to support the weight of the molding materials used to construct the flange since the plug was already waxed it was ready for PVA the clay shelf and the entire exposed half of the plug were then sprayed with PVA three light coats were applied to the highly waxed surface and allowed to dry the mold surface should appear uniformed and drive for continuing to molding at this time the lower mold was constructed off-camera and removed from the plug later in this video we will document the construction of the top mold in detail while the bottom mold was off the plug our next step was to extend the flange we’ll take a moment to explain why this was necessary during the vacuum bagging process the bag would actually be attached to the flange although three inches might have worked a narrow flange makes it difficult to attach all the other vacuum bagging materials and the sealant tape since the mold had to be released anyway we made the modification now so that the upper mold could be made with the wider flange already in place you can see that the finished mold is about 5/8 to 3/4 of an inch thick fiberglass this thick takes time to trim even with the proper tool to begin the modification the flange was neatly trimmed using an air cutoff wheel notice that I’m wearing long sleeves and respirators heavy fibreglass dust like this is best kept off the body and out of the lungs next the mold was inverted on a wax from mica board were 5 inch wide strips of chopped strand mat were butted against the existing flange these were added until they matched the height of the original then wider portions of mat were overlapped on in the mold and the flange when the flange matched the thickness of the rest of the mold and was continuous around the full perimeter it was allowed to cure and then it was released from the firm mica once again I used an air cutoff wheel and trim the excess from the edges of the widened flange the surface of the new flange was very good I still needed to use the belt

sander to level the transition between the old flange and the new one I wanted to mold the flange on the upper mold as smoothly as possible also a smooth flange helps to reduce leaks during vacuum bagging except for hand sanding with finer paper and blowing away the excess dust the lower mold was complete and ready for molding the top half I waxed the bottom mold again before replacing it on the plug this was in case any resin dripped into it while I was constructing the top mold we had already moved all the clay residue from the plug in the waxed flange with the bottom half of the mold returned to the plug we’re ready to document construction of the top mold half the higher surface of the plug was thoroughly sprayed with three coats of PVA before being placed back into the lower mold clay has been added to the new extended flange to make it even smoother and the flange was waxed six times to ensure an easy mold release more PVA was applied after the two were assembled so that the modified flange and exposed plug were completely coated it will now be easy to duplicate the width of that flange into the top mold this will be a polyester mold a polyester mold can be used to pull polyester parts or epoxy parts as we will do polyester molds are typically preferred in most large applications for two reasons first polyester resin is considerably less expensive than epoxy resin and second polyester construction allows the use of chopped strand mat most grades of chopped strand mat cannot be used with epoxy resin the first layer applied to the plug was the surface coat this surface coat will create the surface of the mold from which all future parts will be pulled and is extremely critical the quality of this layer is dependent upon the quality of the plug surface as well as the proper selection catalyzation and application of the gel coat used for the surface coat we use the number 78 tooling gel coat a good tooling grade gel coat is highly recommended for polyester mold surfaces tooling gel coat offers ongoing resistance to part release and has a minimum distortion we filled several cups which could be catalyzed when they were needed Scott measured the Emme KP using an Emmy KP dispenser this ensures a proper amount of catalyst is used for the gel coat he mixed carefully to avoid creating hot spots in the gel coat using a two inch brush he cut in the flange area with gel coat it is easier to begin by brushing than spraying in an area like this you need to cover that right angle where the flange meets the plug and make sure that the gel coat is applied evenly spring directly into an area like this often results in runs or heavy sags I’ll come back and spray over it to level any brush marks but I find this much more controlled after the flange covered I was ready to spray gel coat over the entire surface of the mold using the gel coat cup gun the remainder of the court was sprayed on the brushstrokes quickly disappeared when covered with the atomized gel coat gel coat is sprayed rather than brushed whenever possible even an experienced person will have occasional trouble with gel coat gel coat problems are usually a result of spraying too thick several thin passes are recommended I waited only long enough to catalyze another quart of gel coat before spraying it over the first notice how I use the cup gun it is truly a gravity feed gun and the gel coat will run out the nozzle if it is tipped down when it is extremely full I keep the nozzle pointed upward until I have pulled the trigger and material begins to flow also I do not release the trigger at the end of each pass like I would with a siphon type spray system instead I move quickly and watch that I don’t overlap the previous pass too much a gel coat thickness gauge is used to measure the thickness he checks in several places to make sure that there will be no thick or hot spots like 14 it took a third quart to build the gel coat up to the desired 20 to 21 mils the entire gel coat layer was allowed to cure until it passed the brush test the gel coat may sit on the surface for no more than a few hours before proceeding you need to wait until the gel coat passes the brush test which is when it is cured enough to not move when brush lightly with a dry brush after it passes the brush test however you want to begin laying up your mold within two to four hours to avoid distortion and blistering problems which you would not be able to see if I have gel coat that has been left on a surface for more than four to six hours I’ll pick it off and start over you really want a flawless mold and if your gel coat is damaged it’s really difficult to

repair next we started reinforcing the mold the schedule we followed was to apply two layers of matte followed by one layer of ten ounce cloth then we repeated the process for time until a total of 12 layers had been applied we use polyester laminating resin the first layer of reinforcement is also very important it must be applied without trapping any air pockets if an air bubble exists in this layer the gel coat is unsupported and will collapse when the mold is put into service as a rule neither mad nor woven fabric can be expected to lay around a 90 degree or smaller angle without developing air pockets to eliminate air pockets in the corner where the flange meets the plug we pre-cut strips of mat in two sizes we cut six inch wide strips of matte which match the width of the exposed flange these strips can be laid into place easily and have nice cut edges on both sides thoroughly saturate the strip of mat you intend to lay on the flange we don’t particularly care about the weight of the mold and are fairly generous with the resin content but one cut edge up against the plug and the other falls evenly and minimizes the trimming necessary when finishing the flange watch for clear air bubbles in the resin and work them out using the brush and your fingers as you work if you wish paint some resin down on the flange before you lay your mat strip into place we also cut a number of strips of mat about eight inches wide these I tore in half which left two strips with a single cut edge and one frayed edge I place the frayed edge strips onto the plug surface by budding the cut edge into the corner against the flange the frayed edge drapes evenly onto the plug surface where the other layers may be applied over it without trapping air pockets this bud joint at the corners effectively eliminates air bubbles as always I applied these strips one layer at a time watching closely not the trap air after a few layers have been applied in this way I placed the cut edge of the strip even with the edge of the flange and allow the frayed edge to overlap onto the plug after the flange and plug corner were covered with one even layer we were ready to lay up the surface over the plug it is easier to work torn chunks over the contours than full lengths of mat you will again lay resin on the surface and saturate the mat as well applying the mat directly with gloved hands is the most common approach and allows for the feel of the plug stippling with a brush and a groove saturation roller help to eliminate air you will to apply a total of two matte layers to the plug and the flange before continuing with the 10 ounce fabric on the top you need to let each of these first two matte layers cure individually before laying up the first layer of 10 ounce fabric this ensures that the mold does not get too hot and distort the tooling gel coat during the cure cycle once these three layers have been applied in this fashion and the mould allowed to cool two to three layers may be applied at a time and the mold will resist heat distortion continue by laying in the 10 ounce fabric between every two layers of chopped strand mat the fabric is stronger and more stable than the mat and will help the overall strength of the mold you don’t want to cut the 10 ounce fabric more than necessary it will be necessary to cut slits and some contours but you don’t want to cut strips the properties of the fabric are best achieved by leaving it in as big of pieces as possible you can still apply resin liberally as needed to the plug into the layers of reinforcement try to work evenly applying the same number of layers to all areas on large molds it is easy to lose track of how many layers have been applied and where if you leave a surface cure for more than 24 hours it may be necessary to sand it prior to laying on additional layers after all of the reinforcement layers were applied the completed mold half was about five eighths of an inch thick we usually recommend that the mold be three to four times thicker than the parts to be produced at them this is easily the case with the top mold as only three layers of carbon fiber will be used to make the upper shell the lower mold is also plenty thick because the sandwich laminate is really only seven layers of carbon fiber all seven are only an eighth of an inch thick in areas with no honeycomb a better gauge is to determine how long the mold is to be in service if it is expected to be used often make it a little heavier now so it will last the fourth step of molding is releasing the mold from the plug releasing the molds from the plug can

often be a tedious process locate the largest gaps between the two and begin working the wedges into these locations choose a wedge which matches the gap as they come in multiple sizes the first few wedges are generally most difficult to insert once a few were in place creating more gaps larger wedges may be worked around the mold until it releases completely never use any metal objects to aid in the release of the mold invariably metal will gouge or crack the new mold in this case it was just a matter of inserting enough wedges around the perimeter until the mold broke free the rear came up first then the rest of the mold was lifted off the plug the plug is still resting in the lower mold but it obviously came through the molding process intact it took many hands to lift the large waxed plug out of the lower mold however the two came apart easily because they had been released once before we inspected the molds following their release both were found to have highly polished surface finishes there were no marks or scratches requiring coarse sanding to eliminate but a slight surface texture was present the top mold look great and the team was feeling excited overall I was extremely pleased and felt that we were well on our way to making the shell off-camera Scott used an air-powered die grinder just as before to trim the excess material from the flange of the top mold after that he wet sanded beginning with 320 grit while using foam sanding pads it quickly progressed to 600 grit the mold was then washed and dried machine glaze was spread on the surface and hand polished using tarry wipes the molds were then waxed six times again allowing an hour between every two coats at this stage both the upper and lower molds were perfectly polished and ready for use in vacuum bagging fabrication the plug construction portion of this project took longer to complete the necessary in the end – perfect molds were produced but they could have been done sooner and easier with more forethought at the design stage I was eager to get building and left some quality issues in the cross-section designs unaddressed I knew I could compensate for it later so I forged ahead it’s a testimony to the composite materials themselves that such fine products can be made from such humble beginnings take it from me it is better spend an extra week at the drafting table or computer than an extra month in the shop remember the phrase measure twice cut once following the molding portion of this project the student team from the University of Akron had a working knowledge of the plug concept and mold making techniques necessary for completion of a project on this scale it was encouraging to hear the comments of the students as they brainstormed about other projects they could tackle using these skills and materials it is our goal that this video has given you the same knowledge and confidence to tackle your molding projects even if the design exists only in your mind using easily formed materials you can follow this process step-by-step to construct your desired plug and the molds to make your parts consult either the sister video on sandwich core construction or our molding fiberglass video for instructions on lamination of finished parts the last three steps of molding involves preparing the mold for fabrication through releasing the final parts these steps are covered in both our molding fiberglass and our sister video vacuum bagging techniques and sandwich core construction remember that you can call and talk to Scott or any member of our customer service team and we will be glad to help you with your questions and your project we want your project to be a success thank you for watching you