The following pictures show how a fuselage is molded using a seamless layup. I am using my Micro Hand Launch Glider mold, the Itch. You can see a picture of the Itch on the Micro HLG page. I have tried to keep the detail up so that you can see how I do it. Note that this is the way I am currently doing it. I save alot of weight. When I use 2 layers of 1.5 oz glass with CF, the end weight of the fuselage and nosecone is 17-18 gm. If I use 1 layer of 1.5 oz glass and 1 layer of 3.2 oz stain glass (different fiber weave) with CF, the weight is 25 gm. The fuselage is made as dry as possible, since weight is in the epoxy. I have made the fuselage with 2 layers of 3.2 oz cloth, and the resulting fuselage weighs approximately 32 gm. This fuselage would be an excellent choice for a 60" HLG or small slope ship. I welcome your comments. -----Chris Adams
|This picture shows the fuselage and nosecone mold halves. They have been waxed and buffed out, and are ready for mold release application. I use an airbrush to apply a layer of PVA. There are other mold releases avaialable, but this is what I have been using for years and I like it. Make sure an even coat is applied and allowed to dry.|
|I first apply a coat of epoxy to one mold half, then place the part aside and apply a coat to the second mold half. Since epoxy cures with heat, application of a thin coat slows down the curing process and removes epoxy from the mixing cup, so curing in the cup is also slowed. Here I am using West Systems epoxy,105/206, and have mixed in neon yellow coloring.|
|After applying the layer of epoxy, I place the first glass layer in the mold and work it into the resin. I then add the CF tow, and stipple the CF to get the epoxy to soak into the tow. I then add a reinforcing layer around the wing saddle, 1 layer of 1.5 oz cloth. I try to wet out the glass where the edge of the seam would be. I wet out about 1/4" up on the top part of the glass on one half of the mold and then do the same on the other mold half for the bottom of the fuselage. I then add the second full layer of glass. At this point I try to stretch the epoxy, removing epoxy from one part of the mold to apply to another part of the mold. I try not to add extra epoxy unless I need to. Use your brush in a dabbing, stippling fashion to get the glass to absorb the epoxy. If you can see the glass weave, it will look like there is not enough epoxy. If this is the case then you have the right amount of epoxy. I always remember that if I add too much epoxy I will have a problem removing the excess, and the resultant fuselage will be heavier.|
|After laying up both sides I now trim the overlap to between 1/8" to 1/4". The overlap I have found to be very dependent on the curvature of the fuselage, the weight of the glass layers, and above all(!!!!!) the accessability of the layers when the mold is placed together for seaming. When using 2 layers of 1.5 oz cloth, the overlap can be greater, but with 3.2 oz cloth the overlap is smaller, especially if the fuselage sides are very curved as in the Itch tailboom.|
|I am now jumping to show the nosecone mold. The fuselage sides are now joined, but the joining is more easily seen in the nosecone layup. I lay up the main fuselage first, then layup the nosecone. The main problem is accessing the cloth overlaping the opposing side. Since the tailboom is very narrow I use a bent coat hanger, with its end bent in a tiny loop, to reach all the places where the coth overlaps the opposite side. If you are making a large fuselage mold, there may be ample access through the wing saddle or nose area. The tailboom can also be reached easily with a brush or with a brush, or swab, on a dowel.|
|This photos shows the nosecone mold pieces with the cloth and epoxy applied prior to trimming. The method for this is exactly like the main fuselage.|
|Here, the fiberglass cloth has been trimmed. Note that one half has the bottom seam extended, while the other half
has the top extended. The radius of the nose is the most troublesome. Since I can reach the nose easily when joining
the nosecones, I leave a little bit of extra glass around the nose area. When preparing the main fuselage for joining,
I cut the nose glass a little closer, and just prior to joining I add a little extra epoxy near the nose. When
the fuselage is joined, and allowed to settle for curing I tilt the mold nose down. Excess resin flows to the nose
and fills in any area where the glass does not overlap.
For the nosecone, I trim the one side flush with the mold side. I do this for both parts. I am now ready to join. I have found that using a wide artist's paintbrush I can apply a bead of epoxy along the flush seam, on the cloth. I do this for both parts. I do not use alot, but I use enough, as it will help with sealing the overlaping glass and fill in the seam joint.
|Here you can see the overlapping and trimmed areas of the glass cloth just prior to joining. I now fold over the cloth near the nose so that when I join the halves the cloth will not be trapped between the flat mold sides. If you look at the photo just prior to this you will see what I mean. This can be a problem with the main part of the fuselage joining, since you want to make sure that the cloth does not separate from the mold sides and create a bubble or delamination. I go over all edges near where the seam will be with a brush to remove bubbles or delaminations.|
|I received a number of suggestions after I posted this page regarding the overlaping cloth:
With only a couple of lightweight layers of glass in a HLG fuselage there should not be a need to trim the outer layer of glass. On a heavier molding, if there is a fear of making the overlap too light you could always add an extra 1" wide strip to compensate. However, during normal joining of fuselage sides, usually only one layer of joining tape is used. Incidentally, the first glass outer layer(s) can be trimmed flush with the mold on both sides and then use the last inner glass layer as the overlap. This gets around the problem of lifting of the outer glass layers from the mold as they pressed into place on the other side of the mold.
Additional fuselage strength may be added with fiber orientation. Bending strength will come from the cross
section. Torsional rigidity will come from the fiber orientation. In the fuse, especially in the section aft of the
trailing edge, the fibers can be oriented at 45 degrees to the long axes of the fuse. In some cases imbedding CF tow, or unidirectional cloth can increase the strength while not adding extra cloth weight.
|This photo speaks for itself. You can see that when joining the halves, you carefully set the mold parts together such that the extended part of the cloth projects into the open and free halve of the opposite side. The tolerances are great in the nosecone, but in the fuselage the tolerances may be very small. Be careful not to trap any part of the overlapping cloth between the mold halves. Once positioned, as shown, push down on the mold to keep the parts together and slide the mold parts sideways.|
|Once slid together, bolt the mold parts together. As mentioned earlier, that extra bead of epoxy will join and bind the overlaping glass to the trimed side. If any cloth gets trapped between the mold halves, I loosen the bolts, carefully separate the sides of the mold, and hold them apart with a small wedge. I then use a spatula to press the glass into the center of the mold. Be careful here since doing this delaminates the cloth from the internal sides of the mold. You MUST make sure that the wet glass is laminated to the mold sides otherwise you will get bubbles.|
|Here you can see the mold parts bolted together. I have taken a brush and carefully joined the overlapping cloth
to the opposite side. I have removed all air bubbles and used to brush to remove any delaminations. I used the
bent coat hanger end to reach into the nose, to join the glass cloth there.
The joining is easy with the nosecone, but making sure the overlaping cloth binds to the opposite side of the fuselage in the main mold is very difficult, at least it is with my Itch mold! I use a bright light to shine through the mold. Any delaminations or bubbles are very visible as light patches. I pat, swipe, press, or use whatever technique I can to get the overlaping cloth to settle into place. This is not easy, so careful designing of the mold is very important. I try to make one piece fuselages, and hate canopy cutouts as I don't want to spend alot of time making sure they match well. In the next photo you can see that the only access holes are through the tailboom, approx. 3/8" or less in diameter, and through the wing saddle, 1/2" x 2 1/2".
|Curing is very dependent upon temperature. Since when this was photographed my garage temperature was between 24-55
degrees F, I needed to contain the heat. My first fuselage took 3 days to cure, but with this setup it takes about
I have made a craddle of Al foil. I have placed my mold in the craddle. I then bring two 100W lightbulbs with reflectors down close to the mold. They are approximately 1-1/2 ft away. Note that I use a thermocouple thermometer from Radio Shack to monitor the temperature. The high temperature is regulated by the distance to the mold from the lights, and how cold my garage gets. Some may want to make an oven from a box, or from Al sided foamboard. Using this method, with an open top, I can get the mold temperature up to 130 F or greater. Note that at these high temps the mold can be damaged, or local heat can be higher since the BLACK CF tow can absorb and hold the heat better. I will flip the mold several times during the curing process.
Once cured, cool the mold! If you do not cool it the fuselage and epoxy will still be flexible and when you try to remove the part it will bend and keep the bend. You can, if required, use a heat gun on the part to soften the epoxy and straighten any bends. If you have a rigid mold, and the part is cool and cured, this should not be a problem.
I remove the bolts, then give a twist to the mold. This breaks the part free from the mold surface. I then separate the mold parts, and carefull remove the part. There will be alot of flashing around the seam area, and this can be trimmed off by breaking, trimming, or sanding. I then wash the mold and part with water to remove all PVA, then let them dry. I try to keep a log of the amount of resin I used, the mixing ratios, the glass layers etc, so that I can access whether I can get a lighter layup, or need to add more glass in easily damaged areas.
Have FUN!!!! Chris Adams firstname.lastname@example.org