Probably the single most important thing that can be done to protect our sailplanes from hangar rash and transportation damage is to make a cradle to securely hold the fuselage.
One of the easiest ways to make a cradle to fit the sailplane is to mold it out of fiberglass. These step-by-step instructions will help any builder accomplish this task quickly:
Step 1: When molding a cradle for a fiberglass sailplane, it’s a good idea to apply a couple coats of wax to the fuselage. Even though the entire fuse will be covered with plastic, you don’t want to take any chances the resin will get onto your new glass slipper.
Step 2: After waxing the plane, wrap the entire fuselage in plastic, cut little holes in the plastic where the tape can stick to the fuse. Be careful with tape selection, you do not want to remove any paint when peeling off the tape later. I use small amounts of Scotch tape to hold the plastic on. After securing the plastic, choose the locations where your cradles will contact the fuselage. At these locations, add a 1/4″ thick piece of filler. Use cardboard or air duct insulation foam as an example. This filler will allow the cradle to have room for a nice soft foam to cushion the fuse after we are all done. Also, be sure to add some release tape to the filler, you will be molding right on top of it.
TIP: Regular DUCT tape from the hardware store is the best release tape you can get. Fiberglass resin will NOT stick to it.
Step 3: Cut fiberglass cloth to size and apply it right over the filler pads to form the cradles. In the construction of these cradles for an 8-meter Duo Discus, I knew I needed them to be sturdy, so I used a piece of 5 oz. fiberglass cloth first, then a very thick fiberglass MAT over next followed by another piece of 5 oz. cloth. Since MAT is rough, the fiberglass cloth will make it look better when finished. Depending on the size and weight of the glider, you can adjust the layup schedule appropriately. Be sure to allow plenty extra around the edges, all of the excess will get cut off later.
Step 4: After the resin has cured, mark the center line of the fuselage. This is very important for lining it all up later. At this point, you need to choose the desired shape of each cradle. I take a piece a paper and make a template the size and shape I want. Start with the largest cradle, and work your way to the smallest. You will be able to use the same paper template for each one. Just keep cutting it smaller as you go. Once you have the shape you desire, line it up on the center line and using a sharpie, trace it onto the fiberglass.
Step 5: Remove the cradle, admire your craftsmanship for a moment, then cut the shape out. I try to cut close to the line, but leave a little for the belt sander to finish up. Be sure to wear a dust mask when cutting and sanding fiberglass.
Do the same for the other cradles if you have more than one.
Step 6: Time to make the supports. For this particular sailplane, I chose to male the cradles with a solid pedestal support. I has some 2×4 laying around and a small piece of 4×4 too. My plan uses the 4×4 for the front cradle, and the 2×4′s for the other two. Place the cradles back onto the plane and using the center lines you made, line them all up very accurately. Tape them to the fuse to hold them in place. Trim the wood pieces to fit the cradles and if you desire, add some design to the ends before we glue them together. I always cut curves into the supports, just for looks. Now is a good time to sand the wood smooth.
Step 7: Secure the wood to the fiberglass cradle. Using resin mixed with a filler, something like cotton FLOX or even Micro Balloons, make a thick past that will not run down the side of the plane. Apply the resin and squish it all into place. Use plenty of resin and use a stick or finger to smooth any glue that oozes out. Set all the supports at the same time and let them cure.
Step 8: Now that all the resin has cured and the hard work is done, its time to finish them up. Leaving them in place on the fuse, get a friend to help you draw your cut lines. I used a chalk line and held it at one end of the first cradle, then had my dad hold the other end against the last cradle and we snapped the line onto the blocks. I removed the cradles from the plane and cut the angles along the lines.
Mix up some more Micro Balloons and resin in a very thick past and use it as a filler. Sand and smooth the cradles and supports so you get a nice finish. A little time here pays off in the end. Next, spray on a couple coats of sandable primer and were ready to paint them!
Step 9: Once the paint has completely dried and you’re done admiring you handy-work, lets get these finished. You will need a tough, but soft foam to cushion the fuselage when it sits in these cradles. I use a 1/4″ white medium density foam with a self adhesive back. I purchase this foam in a 2′x2′ square from McMaster Carr, Part number 8722K271 Tear/chemical-resistant Polyethylene Foam, 3/8″ Thick, 24″x 24″ Sheet, Adhesive-backed, white. It is by far the best stuff I have ever used for this purpose. Make sure you leave some extra around the edge when you stick it down, once it touches, it’s ON. Trim off the edge with a razor blade.
Final Step: Using a piece of wood, make the bottom “strong-back” to attach the cradles onto. Be certain to align them properly and then you can fasten them from the bottom with screws. All that’s left is to add some Velcro strapping so the plane won’t move and you are done. Wasn’t that simple?
by Len Buffinton
